Bibliography

2019

1. Simultaneous Kepler/K2 and XMM-Netwon observations of superflares in the Pleiades ADS
Abstract

Flares are powerful events ignited by a sudden release of magnetic energy. With the aim of studying flares in the 125-Myr-old stars in the Pleiades observed simultaneously in optical and X-ray light, we obtained new XMM-Newton observations of this cluster during the observations of Kepler K2 Campaign 4. Our objective is to characterize the most powerful flares observed in both bands and to constrain the energy released in the optical and X-ray, the geometry of the loops, and their time evolution. We aim to compare our results to existing studies of flares occurring in the Sun and stars at different ages. We selected bright X-ray/optical flares occurred in 12 known members of the Pleiades from their K2 and XMM-Newton light curves. The sample includes ten K-M stars, one F9 star, and one G8 star. Flare average properties were obtained from integrated analysis of the light curves during the flares. The time evolution of the plasma in the magnetic loops is constrained with time-resolved X-ray spectral analysis. Most of the flares studied in this work emitted more energy in optical than in X-rays, as in most solar flares, even if the Pleiades flares output a larger fraction of their total energy in X-rays than typical solar flares do. Additionally, the energy budget in the two bands is weakly correlated. We also found comparable flare duration in optical and X-rays and observed that rapidly rotating stars (e.g., with rotation period shorter than 0.5 days) preferentially host short flares. We estimated the slope of the cooling path of the flares in the log(EM)-versus-log(T) plane. The values we obtained are affected by large uncertainties, but their nominal values suggest that the flares analyzed in this paper are mainly due to single loops with no sustained heating occurring during the cooling phase. We also observed and analyzed oscillations with a period of 500 s during one of the flares.

Guarcello , M. G.;Micela, G.;Sciortino, S.;Lopez-Santiago, J.;Argiroffi, C.;Reale, F.;Flaccomio, E.;Alvarado-Gomez, J. D.;Antoniou, V.;Drake, J. J.;Pillitteri, I.;Rebull, L. M.;Stauffer, J.
Astronomy & Astrophysics, Volume 622, id.A210, 24 pp.
Jan 2019

2018

1. A chemical survey of exoplanets with ARIEL ADS CITATION
Abstract

Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the essential nature of these exoplanets remains largely mysterious: there is no known, discernible pattern linking the presence, size, or orbital parameters of a planet to the nature of its parent star. We have little idea whether the chemistry of a planet is linked to its formation environment, or whether the type of host star drives the physics and chemistry of the planet’s birth, and evolution. ARIEL was conceived to observe a large number ( 1000) of transiting planets for statistical understanding, including gas giants, Neptunes, super-Earths and Earth-size planets around a range of host star types using transit spectroscopy in the 1.25-7.8 μm spectral range and multiple narrow-band photometry in the optical. ARIEL will focus on warm and hot planets to take advantage of their well-mixed atmospheres which should show minimal condensation and sequestration of high-Z materials compared to their colder Solar System siblings. Said warm and hot atmospheres are expected to be more representative of the planetary bulk composition. Observations of these warm/hot exoplanets, and in particular of their elemental composition (especially C, O, N, S, Si), will allow the understanding of the early stages of planetary and atmospheric formation during the nebular phase and the following few million years. ARIEL will thus provide a representative picture of the chemical nature of the exoplanets and relate this directly to the type and chemical environment of the host star. ARIEL is designed as a dedicated survey mission for combined-light spectroscopy, capable of observing a large and well-defined planet sample within its 4-year mission lifetime. Transit, eclipse and phase-curve spectroscopy methods, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allow us to measure atmospheric signals from the planet at levels of 10-100 part per million (ppm) relative to the star and, given the bright nature of targets, also allows more sophisticated techniques, such as eclipse mapping, to give a deeper insight into the nature of the atmosphere. These types of observations require a stable payload and satellite platform with broad, instantaneous wavelength coverage to detect many molecular species, probe the thermal structure, identify clouds and monitor the stellar activity. The wavelength range proposed covers all the expected major atmospheric gases from e.g. H2O, CO2, CH4 NH3, HCN, H2S through to the more exotic metallic compounds, such as TiO, VO, and condensed species. Simulations of ARIEL performance in conducting exoplanet surveys have been performed – using conservative estimates of mission performance and a full model of all significant noise sources in the measurement – using a list of potential ARIEL targets that incorporates the latest available exoplanet statistics. The conclusion at the end of the Phase A study, is that ARIEL – in line with the stated mission objectives – will be able to observe about 1000 exoplanets depending on the details of the adopted survey strategy, thus confirming the feasibility of the main science objectives.

Tinetti, Giovanna;Drossart, Pierre;Eccleston, Paul;Hartogh, Paul;Heske, Astrid;Leconte, Jérémy;Micela, Giusi;Ollivier, Marc;Pilbratt, Göran;Puig, Ludovic;Turrini, Diego;Vandenbussche, Bart;Wolkenberg, Paulina;Beaulieu, Jean-Philippe;Buchave, Lars A.;Ferus, Martin;Griffin, Matt;Guedel, Manuel;Justtanont, Kay;Lagage, Pierre-Olivier;Machado, Pedro;Malaguti, Giuseppe;Min, Michiel;Nørgaard-Nielsen, Hans Ulrik;Rataj, Mirek;Ray, Tom;Ribas, Ignasi;Swain, Mark;Szabo, Robert;Werner, Stephanie;Barstow, Joanna;Burleigh, Matt;Cho, James;du Foresto, Vincent Coudé;Coustenis, Athena;Decin, Leen;Encrenaz, Therese;Galand, Marina;Gillon, Michael;Helled, Ravit;Morales, Juan Carlos;Muñoz, Antonio García;Moneti, Andrea;Pagano, Isabella;Pascale, Enzo;Piccioni, Giuseppe;Pinfield, David;Sarkar, Subhajit;Selsis, Franck;Tennyson, Jonathan;Triaud, Amaury;Venot, Olivia;Waldmann, Ingo;Waltham, David;Wright, Gillian;Amiaux, Jerome;Auguères, Jean-Louis;Berthé, Michel;Bezawada, Naidu;Bishop, Georgia;Bowles, Neil;Coffey, Deirdre;Colomé, Josep;Crook, Martin;Crouzet, Pierre-Elie;Da Peppo, Vania;Sanz, Isabel Escudero;Focardi, Mauro;Frericks, Martin;Hunt, Tom;Kohley, Ralf;Middleton, Kevin;Morgante, Gianluca;Ottensamer, Roland;Pace, Emanuele;Pearson, Chris;Stamper, Richard;Symonds, Kate;Rengel, Miriam;Renotte, Etienne;Ade, Peter;Affer, Laura;Alard, Christophe;Allard, Nicole;Altieri, Francesca;André, Yves;Arena, Claudio;Argyriou, Ioannis;Aylward, Alan;Baccani, Cristian;Bakos, Gaspar;Banaszkiewicz, Marek;Barlow, Mike;Batista, Virginie;Bellucci, Giancarlo;Benatti, Serena;Bernardi, Pernelle;Bézard, Bruno;Blecka, Maria;Bolmont, Emeline;Bonfond, Bertrand;Bonito, Rosaria;Bonomo, Aldo S.;Brucato, John Robert;Brun, Allan Sacha;Bryson, Ian;Bujwan, Waldemar;Casewell, Sarah;Charnay, Bejamin;Pestellini, Cesare Cecchi;Chen, Guo;Ciaravella, Angela;Claudi, Riccardo;Clédassou, Rodolphe;Damasso, Mario;Damiano, Mario;Danielski, Camilla;Deroo, Pieter;Di Giorgio, Anna Maria;Dominik, Carsten;Doublier, Vanessa;Doyle, Simon;Doyon, René;Drummond, Benjamin;Duong, Bastien;Eales, Stephen;Edwards, Billy;Farina, Maria;Flaccomio, Ettore;Fletcher, Leigh;Forget, François;Fossey, Steve;Fränz, Markus;Fujii, Yuka;García-Piquer, Álvaro;Gear, Walter;Geoffray, Hervé;Gérard, Jean Claude;Gesa, Lluis;Gomez, H.;Graczyk, Rafał;Griffith, Caitlin;Grodent, Denis;Guarcello , Mario Giuseppe;Gustin, Jacques;Hamano, Keiko;Hargrave, Peter;Hello, Yann;Heng, Kevin;Herrero, Enrique;Hornstrup, Allan;Hubert, Benoit;Ida, Shigeru;Ikoma, Masahiro;Iro, Nicolas;Irwin, Patrick;Jarchow, Christopher;Jaubert, Jean;Jones, Hugh;Julien, Queyrel;Kameda, Shingo;Kerschbaum, Franz;Kervella, Pierre;Koskinen, Tommi;Krijger, Matthijs;Krupp, Norbert;Lafarga, Marina;Landini, Federico;Lellouch, Emanuel;Leto, Giuseppe;Luntzer, A.;Rank-Lüftinger, Theresa;Maggio, Antonio;Maldonado, Jesus;Maillard, Jean-Pierre;Mall, Urs;Marquette, Jean-Baptiste;Mathis, Stephane;Maxted, Pierre;Matsuo, Taro;Medvedev, Alexander;Miguel, Yamila;Minier, Vincent;Morello, Giuseppe;Mura, Alessandro;Narita, Norio;Nascimbeni, Valerio;Nguyen Tong, N.;Noce, Vladimiro;Oliva, Fabrizio;Palle, Enric;Palmer, Paul;Pancrazzi, Maurizio;Papageorgiou, Andreas;Parmentier, Vivien;Perger, Manuel;Petralia, Antonino;Pezzuto, Stefano;Pierrehumbert, Ray;Pillitteri, Ignazio;Piotto, Giampaolo;Pisano, Giampaolo;Prisinzano, Loredana;Radioti, Aikaterini;Réess, Jean-Michel;Rezac, Ladislav;Rocchetto, Marco;Rosich, Albert;Sanna, Nicoletta;Santerne, Alexandre;Savini, Giorgio;Scandariato, Gaetano;Sicardy, Bruno;Sierra, Carles;Sindoni, Giuseppe;Skup, Konrad;Snellen, Ignas;Sobiecki, Mateusz;Soret, Lauriane;Sozzetti, Alessandro;Stiepen, A.;Strugarek, Antoine;Taylor, Jake;Taylor, William;Terenzi, Luca;Tessenyi, Marcell;Tsiaras, Angelos;Tucker, C.;Valencia, Diana;Vasisht, Gautam;Vazan, Allona;Vilardell, Francesc;Vinatier, Sabrine;Viti, Serena;Waters, Rens;Wawer, Piotr;Wawrzaszek, Anna;Whitworth, Anthony;Yung, Yuk L.;Yurchenko, Sergey N.;Osorio, María Rosa Zapatero;Zellem, Robert;Zingales, Tiziano;Zwart, Frans
Experimental Astronomy, Volume 46, Issue 1, pp.135-209
Nov 2018
2. A chemical survey of exoplanets with ARIEL ADS CITATION
Abstract

Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the essential nature of these exoplanets remains largely mysterious: there is no known, discernible pattern linking the presence, size, or orbital parameters of a planet to the nature of its parent star. We have little idea whether the chemistry of a planet is linked to its formation environment, or whether the type of host star drives the physics and chemistry of the planet’s birth, and evolution. ARIEL was conceived to observe a large number ( 1000) of transiting planets for statistical understanding, including gas giants, Neptunes, super-Earths and Earth-size planets around a range of host star types using transit spectroscopy in the 1.25-7.8 μm spectral range and multiple narrow-band photometry in the optical. ARIEL will focus on warm and hot planets to take advantage of their well-mixed atmospheres which should show minimal condensation and sequestration of high-Z materials compared to their colder Solar System siblings. Said warm and hot atmospheres are expected to be more representative of the planetary bulk composition. Observations of these warm/hot exoplanets, and in particular of their elemental composition (especially C, O, N, S, Si), will allow the understanding of the early stages of planetary and atmospheric formation during the nebular phase and the following few million years. ARIEL will thus provide a representative picture of the chemical nature of the exoplanets and relate this directly to the type and chemical environment of the host star. ARIEL is designed as a dedicated survey mission for combined-light spectroscopy, capable of observing a large and well-defined planet sample within its 4-year mission lifetime. Transit, eclipse and phase-curve spectroscopy methods, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allow us to measure atmospheric signals from the planet at levels of 10-100 part per million (ppm) relative to the star and, given the bright nature of targets, also allows more sophisticated techniques, such as eclipse mapping, to give a deeper insight into the nature of the atmosphere. These types of observations require a stable payload and satellite platform with broad, instantaneous wavelength coverage to detect many molecular species, probe the thermal structure, identify clouds and monitor the stellar activity. The wavelength range proposed covers all the expected major atmospheric gases from e.g. H2O, CO2, CH4 NH3, HCN, H2S through to the more exotic metallic compounds, such as TiO, VO, and condensed species. Simulations of ARIEL performance in conducting exoplanet surveys have been performed – using conservative estimates of mission performance and a full model of all significant noise sources in the measurement – using a list of potential ARIEL targets that incorporates the latest available exoplanet statistics. The conclusion at the end of the Phase A study, is that ARIEL – in line with the stated mission objectives – will be able to observe about 1000 exoplanets depending on the details of the adopted survey strategy, thus confirming the feasibility of the main science objectives.

Tinetti, Giovanna;Drossart, Pierre;Eccleston, Paul;Hartogh, Paul;Heske, Astrid;Leconte, Jérémy;Micela, Giusi;Ollivier, Marc;Pilbratt, Göran;Puig, Ludovic;Turrini, Diego;Vandenbussche, Bart;Wolkenberg, Paulina;Beaulieu, Jean-Philippe;Buchave, Lars A.;Ferus, Martin;Griffin, Matt;Guedel, Manuel;Justtanont, Kay;Lagage, Pierre-Olivier;Machado, Pedro;Malaguti, Giuseppe;Min, Michiel;Nørgaard-Nielsen, Hans Ulrik;Rataj, Mirek;Ray, Tom;Ribas, Ignasi;Swain, Mark;Szabo, Robert;Werner, Stephanie;Barstow, Joanna;Burleigh, Matt;Cho, James;du Foresto, Vincent Coudé;Coustenis, Athena;Decin, Leen;Encrenaz, Therese;Galand, Marina;Gillon, Michael;Helled, Ravit;Morales, Juan Carlos;Muñoz, Antonio García;Moneti, Andrea;Pagano, Isabella;Pascale, Enzo;Piccioni, Giuseppe;Pinfield, David;Sarkar, Subhajit;Selsis, Franck;Tennyson, Jonathan;Triaud, Amaury;Venot, Olivia;Waldmann, Ingo;Waltham, David;Wright, Gillian;Amiaux, Jerome;Auguères, Jean-Louis;Berthé, Michel;Bezawada, Naidu;Bishop, Georgia;Bowles, Neil;Coffey, Deirdre;Colomé, Josep;Crook, Martin;Crouzet, Pierre-Elie;Da Peppo, Vania;Sanz, Isabel Escudero;Focardi, Mauro;Frericks, Martin;Hunt, Tom;Kohley, Ralf;Middleton, Kevin;Morgante, Gianluca;Ottensamer, Roland;Pace, Emanuele;Pearson, Chris;Stamper, Richard;Symonds, Kate;Rengel, Miriam;Renotte, Etienne;Ade, Peter;Affer, Laura;Alard, Christophe;Allard, Nicole;Altieri, Francesca;André, Yves;Arena, Claudio;Argyriou, Ioannis;Aylward, Alan;Baccani, Cristian;Bakos, Gaspar;Banaszkiewicz, Marek;Barlow, Mike;Batista, Virginie;Bellucci, Giancarlo;Benatti, Serena;Bernardi, Pernelle;Bézard, Bruno;Blecka, Maria;Bolmont, Emeline;Bonfond, Bertrand;Bonito, Rosaria;Bonomo, Aldo S.;Brucato, John Robert;Brun, Allan Sacha;Bryson, Ian;Bujwan, Waldemar;Casewell, Sarah;Charnay, Bejamin;Pestellini, Cesare Cecchi;Chen, Guo;Ciaravella, Angela;Claudi, Riccardo;Clédassou, Rodolphe;Damasso, Mario;Damiano, Mario;Danielski, Camilla;Deroo, Pieter;Di Giorgio, Anna Maria;Dominik, Carsten;Doublier, Vanessa;Doyle, Simon;Doyon, René;Drummond, Benjamin;Duong, Bastien;Eales, Stephen;Edwards, Billy;Farina, Maria;Flaccomio, Ettore;Fletcher, Leigh;Forget, François;Fossey, Steve;Fränz, Markus;Fujii, Yuka;García-Piquer, Álvaro;Gear, Walter;Geoffray, Hervé;Gérard, Jean Claude;Gesa, Lluis;Gomez, H.;Graczyk, Rafał;Griffith, Caitlin;Grodent, Denis;Guarcello , Mario Giuseppe;Gustin, Jacques;Hamano, Keiko;Hargrave, Peter;Hello, Yann;Heng, Kevin;Herrero, Enrique;Hornstrup, Allan;Hubert, Benoit;Ida, Shigeru;Ikoma, Masahiro;Iro, Nicolas;Irwin, Patrick;Jarchow, Christopher;Jaubert, Jean;Jones, Hugh;Julien, Queyrel;Kameda, Shingo;Kerschbaum, Franz;Kervella, Pierre;Koskinen, Tommi;Krijger, Matthijs;Krupp, Norbert;Lafarga, Marina;Landini, Federico;Lellouch, Emanuel;Leto, Giuseppe;Luntzer, A.;Rank-Lüftinger, Theresa;Maggio, Antonio;Maldonado, Jesus;Maillard, Jean-Pierre;Mall, Urs;Marquette, Jean-Baptiste;Mathis, Stephane;Maxted, Pierre;Matsuo, Taro;Medvedev, Alexander;Miguel, Yamila;Minier, Vincent;Morello, Giuseppe;Mura, Alessandro;Narita, Norio;Nascimbeni, Valerio;Nguyen Tong, N.;Noce, Vladimiro;Oliva, Fabrizio;Palle, Enric;Palmer, Paul;Pancrazzi, Maurizio;Papageorgiou, Andreas;Parmentier, Vivien;Perger, Manuel;Petralia, Antonino;Pezzuto, Stefano;Pierrehumbert, Ray;Pillitteri, Ignazio;Piotto, Giampaolo;Pisano, Giampaolo;Prisinzano, Loredana;Radioti, Aikaterini;Réess, Jean-Michel;Rezac, Ladislav;Rocchetto, Marco;Rosich, Albert;Sanna, Nicoletta;Santerne, Alexandre;Savini, Giorgio;Scandariato, Gaetano;Sicardy, Bruno;Sierra, Carles;Sindoni, Giuseppe;Skup, Konrad;Snellen, Ignas;Sobiecki, Mateusz;Soret, Lauriane;Sozzetti, Alessandro;Stiepen, A.;Strugarek, Antoine;Taylor, Jake;Taylor, William;Terenzi, Luca;Tessenyi, Marcell;Tsiaras, Angelos;Tucker, C.;Valencia, Diana;Vasisht, Gautam;Vazan, Allona;Vilardell, Francesc;Vinatier, Sabrine;Viti, Serena;Waters, Rens;Wawer, Piotr;Wawrzaszek, Anna;Whitworth, Anthony;Yung, Yuk L.;Yurchenko, Sergey N.;Osorio, María Rosa Zapatero;Zellem, Robert;Zingales, Tiziano;Zwart, Frans
Experimental Astronomy, Online First
Sep 2018
3. A multi-wavelength view of magnetic flaring from PMS stars ADS CITATION
Abstract

Flares from the Sun and other stars are most prominently observed in the soft X-ray band. Most of the radiated energy, however, is released at optical/UV wavelengths. In spite of decades of investigation, the physics of flares is not fully understood. Even less is known about the powerful flares routinely observed from pre-main sequence stars, which might significantly influence the evolution of circumstellar disks. Observations of the NGC2264 star forming region were obtained in Dec. 2011, simultaneously with three telescopes, Chandra (X-rays), CoRoT (optical), and Spitzer (mIR), as part of the “Coordinated Synoptic Investigation of NGC2264” (CSI-NGC2264). Shorter Chandra and CoRoT observations were also obtained in March 2008. We analyzed the lightcurves to detect X-ray flares with an optical and/or mIR counterpart. Basic flare properties from the three datasets, such as emitted energies and peak luminosities, were then compared to constrain the spectral energy distribution of the flaring emission and the physical conditions of the emitting regions. Flares from stars with and without circumstellar disks were also compared to establish any difference that might be attributed to the presence of disks. Seventy-eight X-ray flares with an optical and/or mIR counterpart were detected. Their optical emission is found to correlate well with, and to be significantly larger than, the X-ray emission. The slopes of the correlations suggest that the difference becomes smaller for the most powerful flares. The mIR flare emission seems to be strongly affected by the presence of a circumstellar disk: flares from stars with disks have a stronger mIR emission with respect to stars without disks. This might be attributed to the reprocessing of the optical (and X-ray) flare emission by the inner circumstellar disk, providing evidence for flare-induced disk heating.

Flaccomio, E.;Micela, G.;Sciortino, S.;Cody, A. M.;Guarcello , M. G.;Morales-Calderòn, M.;Rebull, L.;Stauffer, J. R.
Astronomy & Astrophysics, Volume 620, id.A55, 34 pp.
Jul 2018
4. Low mass star formation and subclustering in the HII regions RCW 32, 33 and 27 of the Vela Molecular Ridge. A photometric diagnostics to identify M-type stars ADS CITATION
Abstract

Most stars born in clusters and recent results suggest that star formation (SF) preferentially occurs in subclusters. Studying the morphology and SF history of young clusters is crucial to understanding early SF. We identify the embedded clusters of young stellar objects (YSOs) down to M stars, in the HII regions RCW33, RCW32 and RCW27 of the Vela Molecular Ridge. Our aim is to characterise their properties, such as morphology and extent of the clusters in the three HII regions, derive stellar ages and the connection of the SF history with the environment. Through public photometric surveys such as Gaia, VPHAS, 2MASS and Spitzer/GLIMPSE, we identify YSOs with IR, Halpha and UV excesses, as signature of circumstellar disks and accretion. In addition, we implement a method to distinguish M dwarfs and giants, by comparing the reddening derived in several optical/IR color-color diagrams, assuming suitable theoretical models. Since this diagnostic is sensitive to stellar gravity, the procedure allows us to identify pre-main sequence stars. We find a large population of YSOs showing signatures of circumstellar disks with or without accretion. In addition, with the new technique of M-type star selection, we find a rich population of young M stars with a spatial distribution strongly correlated to the more massive population. We find evidence of three young clusters, with different morphology. In addition, we identify field stars falling in the same region, by securely classifying them as giants and foreground MS stars. We identify the embedded population of YSOs, down to about 0.1 Msun, associated with the HII regions RCW33, RCW32 and RCW27 and the clusters Vela T2, Cr197 and Vela T1, respectively, showing very different morphologies. Our results suggest a decreasing SF rate in Vela T2 and triggered SF in Cr197 and Vela T1.

Prisinzano, L.;Damiani, F.;Guarcello , M. G.;Micela, G.;Sciortino, S.;Tognelli, E.;Venuti, L.
Astronomy & Astrophysics, Volume 617, id.A63, 20 pp.
Jun 2018
5. The Gaia-ESO Survey and CSI 2264: Substructures, disks, and sequential star formation in the young open cluster NGC 2264 ADS CITATION
Abstract

Context. Reconstructing the structure and history of young clusters is pivotal to understanding the mechanisms and timescales of early stellar evolution and planet formation. Recent studies suggest that star clusters often exhibit a hierarchical structure, possibly resulting from several star formation episodes occurring sequentially rather than a monolithic cloud collapse. Aims: We aim to explore the structure of the open cluster and star-forming region NGC 2264 ( 3 Myr), which is one of the youngest, richest and most accessible star clusters in the local spiral arm of our Galaxy; we link the spatial distribution of cluster members to other stellar properties such as age and evolutionary stage to probe the star formation history within the region. Methods: We combined spectroscopic data obtained as part of the Gaia-ESO Survey (GES) with multi-wavelength photometric data from the Coordinated Synoptic Investigation of NGC 2264 (CSI 2264) campaign. We examined a sample of 655 cluster members, with masses between 0.2 and 1.8 M⊙ and including both disk-bearing and disk-free young stars. We used Teff estimates from GES and g,r,i photometry from CSI 2264 to derive individual extinction and stellar parameters. Results: We find a significant age spread of 4-5 Myr among cluster members. Disk-bearing objects are statistically associated with younger isochronal ages than disk-free sources. The cluster has a hierarchical structure, with two main blocks along its latitudinal extension. The northern half develops around the O-type binary star S Mon; the southern half, close to the tip of the Cone Nebula, contains the most embedded regions of NGC 2264, populated mainly by objects with disks and ongoing accretion. The median ages of objects at different locations within the cluster, and the spatial distribution of disked and non-disked sources, suggest that star formation began in the north of the cluster, over 5 Myr ago, and was ignited in its southern region a few Myr later. Star formation is likely still ongoing in the most embedded regions of the cluster, while the outer regions host a widespread population of more evolved objects; these may be the result of an earlier star formation episode followed by outward migration on timescales of a few Myr. We find a detectable lag between the typical age of disk-bearing objects and that of accreting objects in the inner regions of NGC 2264: the first tend to be older than the second, but younger than disk-free sources at similar locations within the cluster. This supports earlier findings that the characteristic timescales of disk accretion are shorter than those of disk dispersal, and smaller than the average age of NGC 2264 (i.e., ≲3 Myr). At the same time, we note that disks in the north of the cluster tend to be shorter-lived ( 2.5 Myr) than elsewhere; this may reflect the impact of massive stars within the region (notably S Mon), that trigger rapid disk dispersal. Conclusions: Our results, consistent with earlier studies on NGC 2264 and other young clusters, support the idea of a star formation process that takes place sequentially over a prolonged span in a given region. A complete understanding of the dynamics of formation and evolution of star clusters requires accurate astrometric and kinematic characterization of its population; significant advance in this field is foreseen in the upcoming years thanks to the ongoing Gaia mission, coupled with extensive ground-based surveys like GES. Full Table B.1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/609/A10

Venuti, L.;Prisinzano, L.;Sacco, G. G.;Flaccomio, E.;Bonito, R.;Damiani, F.;Micela, G.;Guarcello , M. G.;Randich, S.;Stauffer, J. R.;Cody, A. M.;Jeffries, R. D.;Alencar, S. H. P.;Alfaro, E. J.;Lanzafame, A. C.;Pancino, E.;Bayo, A.;Carraro, G.;Costado, M. T.;Frasca, A.;Jofré, P.;Morbidelli, L.;Sousa, S. G.;Zaggia, S.
Astronomy & Astrophysics, Volume 609, id.A10, 24 pp.
Jan 2018

2017

1. The Gaia-ESO Survey and CSI 2264: Substructures, disks, and sequential star formation in the young open cluster NGC 2264 ADS
Abstract

Context. Reconstructing the structure and history of young clusters is pivotal to understanding the mechanisms and timescales of early stellar evolution and planet formation. Recent studies suggest that star clusters often exhibit a hierarchical structure, possibly resulting from several star formation episodes occurring sequentially rather than a monolithic cloud collapse. Aims: We aim to explore the structure of the open cluster and star-forming region NGC 2264 ( 3 Myr), which is one of the youngest, richest and most accessible star clusters in the local spiral arm of our Galaxy; we link the spatial distribution of cluster members to other stellar properties such as age and evolutionary stage to probe the star formation history within the region. Methods: We combined spectroscopic data obtained as part of the Gaia-ESO Survey (GES) with multi-wavelength photometric data from the Coordinated Synoptic Investigation of NGC 2264 (CSI 2264) campaign. We examined a sample of 655 cluster members, with masses between 0.2 and 1.8 M⊙ and including both disk-bearing and disk-free young stars. We used Teff estimates from GES and g,r,i photometry from CSI 2264 to derive individual extinction and stellar parameters. Results: We find a significant age spread of 4-5 Myr among cluster members. Disk-bearing objects are statistically associated with younger isochronal ages than disk-free sources. The cluster has a hierarchical structure, with two main blocks along its latitudinal extension. The northern half develops around the O-type binary star S Mon; the southern half, close to the tip of the Cone Nebula, contains the most embedded regions of NGC 2264, populated mainly by objects with disks and ongoing accretion. The median ages of objects at different locations within the cluster, and the spatial distribution of disked and non-disked sources, suggest that star formation began in the north of the cluster, over 5 Myr ago, and was ignited in its southern region a few Myr later. Star formation is likely still ongoing in the most embedded regions of the cluster, while the outer regions host a widespread population of more evolved objects; these may be the result of an earlier star formation episode followed by outward migration on timescales of a few Myr. We find a detectable lag between the typical age of disk-bearing objects and that of accreting objects in the inner regions of NGC 2264: the first tend to be older than the second, but younger than disk-free sources at similar locations within the cluster. This supports earlier findings that the characteristic timescales of disk accretion are shorter than those of disk dispersal, and smaller than the average age of NGC 2264 (i.e., ≲3 Myr). At the same time, we note that disks in the north of the cluster tend to be shorter-lived ( 2.5 Myr) than elsewhere; this may reflect the impact of massive stars within the region (notably S Mon), that trigger rapid disk dispersal. Conclusions: Our results, consistent with earlier studies on NGC 2264 and other young clusters, support the idea of a star formation process that takes place sequentially over a prolonged span in a given region. A complete understanding of the dynamics of formation and evolution of star clusters requires accurate astrometric and kinematic characterization of its population; significant advance in this field is foreseen in the upcoming years thanks to the ongoing Gaia mission, coupled with extensive ground-based surveys like GES. Full Table B.1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/609/A10

Venuti, L.;Prisinzano, L.;Sacco, G. G.;Flaccomio, E.;Bonito, R.;Damiani, F.;Micela, G.;Guarcello , M. G.;Randich, S.;Stauffer, J. R.;Cody, A. M.;Jeffries, R. D.;Alencar, S. H. P.;Alfaro, E. J.;Lanzafame, A. C.;Pancino, E.;Bayo, A.;Carraro, G.;Costado, M. T.;Frasca, A.;Jofré, P.;Morbidelli, L.;Sousa, S. G.;Zaggia, S.
Astronomy & Astrophysics, Volume 609, id.A10, 24 pp.
Dec 2017
2. Near-infrared time-series photometry in the field of Cygnus OB2 association. I. Rotational scenario for candidate members ADS CITATION
Abstract

Context. In recent decades, the picture of early pre-main sequence stellar rotational evolution has been constrained by studies targeting different regions at a variety of ages with respect to young star formation. Observational studies suggest a dependence of rotation with mass, and for some mass ranges a connection between rotation and the presence of a circumstellar disk. The role of environmental conditions on the rotational regulation, however, has still not been fully explored. Aims: We investigate the rotational properties of candidate members of the young massive association Cygnus OB2. By evaluating their rotational properties, we address questions regarding the effect of environment properties on PMS rotational evolution. Methods: We studied JHK-band variability in 5083 candidate members (24% of them are disk-bearing stars). We selected variable stars with the Stetson variability index and performed the period search with the Lomb-Scargle periodogram for periods between 0.83-45 days. Period detections were verified using false alarm probability levels, Saunders statistics, the string and rope length method, and visual verification of folded light curves. Results: We identified 1224 periodic variable stars (24% of the candidate member sample, 8% of the disk-bearing sample, and 28% of the non-disk-bearing sample). Monte Carlo simulations were performed in order to evaluate completeness and contamination of the periodic sample, out of which 894 measured periods were considered reliable. Our study was considered reasonably complete for periods between 2 and 30 days. Conclusions: The general scenario for the rotational evolution of young stars seen in other regions is confirmed by Cygnus OB2 period distributions with disc-bearing stars rotating on average more slowly than non-disk-bearing stars. A mass-rotation dependence was also verified, but as in NGC 6530, very low mass stars (M ≤ 0.4 M⊙) are rotating on average slower than higher mass stars (0.4M⊙<M ≤ 1.4 M⊙). We observed an excess of slow rotators among the lower mass population. The disk and mass-rotation connection was also analyzed by taking into account the incident UV radiation arising from O stars in the association. Results compatible with the disk-locking scenario were verified for stars with low UV incidence, but no statistical significant relation between rotation and disk presence was verified for stars with high UV incidence suggesting that massive stars can have an important role in regulating the rotation of nearby low mass stars. The full Table 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/603/A106

Roquette, J.;Bouvier, J.;Alencar, S. H. P.;Vaz, L. P. R.;Guarcello, M. G.
Astronomy & Astrophysics, Volume 603, id.A106, 63 pp.
Jul 2017
3. CSI 2264: Simultaneous optical and X-ray variability in pre-Main Sequence stars. I: Time resolved X-ray spectral analysis during optical dips and accretion bursts in stars with disks ADS CITATION
Abstract

Pre-main sequence stars are variable sources. In stars with disks, this variability is related to the morphology of the inner circumstellar region (<0.1 AU) and that of the photosphere and corona, all impossible to be spatially resolved with present day techniques. This has been the main motivation for the Coordinated Synoptic Investigation of NGC 2264. In this paper, we focus on the stars with disks. We analyze the X-ray spectral properties extracted during optical bursts and dips in order to unveil the nature of these phenomena. We analyze simultaneous CoRoT and Chandra/ACIS-I observations to search for coherent optical and X-ray flux variability in stars with disks. Then, stars are analyzed in two different samples. In stars with variable extinction, we look for a simultaneous increase of optical extinction and X-ray absorption during the optical dips; in stars with accretion bursts, we search for soft X-ray emission and increasing X-ray absorption during the bursts. Results. We find evidence for coherent optical and X-ray flux variability among the stars with variable extinction. In 9/24 stars with optical dips, we observe a simultaneous increase of X-ray absorption and optical extinction. In seven dips, it is possible to calculate the NH/AV ratio in order to infer the composition of the obscuring material. In 5/20 stars with optical accretion bursts, we observe increasing soft X-ray emission during the bursts that we associate to the emission of accreting gas. It is not surprising that these properties are not observed in all the stars with dips and bursts, since favorable geometric configurations are required. The observed variable absorption during the dips is mainly due to dust-free material in accretion streams. In stars with accretion bursts, we observe on average a larger soft X-ray spectral component not observed in non accreting stars.

Guarcello , M. G.;Flaccomio, E.;Micela, G.;Argiroffi, C.;Sciortino, S.;Venuti, L.;Stauffer, J.;Rebull, L.;Cody, A. M.
Astronomy & Astrophysics, Volume 602, id.A10, 79 pp.
Jan 2017

2016

1. Globules and pillars in Cygnus X. I. Herschel far-infrared imaging of the Cygnus OB2 environment ADS CITATION
Abstract

The radiative feedback of massive stars on molecular clouds creates pillars, globules and other features at the interface between the H II region and molecular cloud. Optical and near-infrared observations from the ground as well as with the Hubble or Spitzer satellites have revealed numerous examples of such cloud structures. We present here Herschel far-infrared observations between 70 μm and 500 μm of the immediate environment of the rich Cygnus OB2 association, performed within the Herschel imaging survey of OB Young Stellar objects (HOBYS) program. All of the observed irradiated structures were detected based on their appearance at 70 μm, and have been classified as pillars, globules, evaporating gasous globules (EGGs), proplyd-like objects, and condensations. From the 70 μm and 160 μm flux maps, we derive the local far-ultraviolet (FUV) field on the photon dominated surfaces. In parallel, we use a census of the O-stars to estimate the overall FUV-field, that is 103-104 G0 (Habing field) close to the central OB cluster (within 10 pc) and decreases down to a few tens G0, in a distance of 50 pc. From a spectral energy distribution (SED) fit to the four longest Herschel wavelengths, we determine column density and temperature maps and derive masses, volume densities and surface densities for these structures. We find that the morphological classification corresponds to distinct physical properties. Pillars and globules are massive (~500 M⊙) and large (equivalent radius r ~ 0.6 pc) structures, corresponding to what is defined as “clumps” for molecular clouds. EGGs and proplyd-likeobjects are smaller (r ~ 0.1 and 0.2 pc) and less massive (~10 and ~30 M⊙). Cloud condensations are small (~0.1 pc), have an average mass of 35 M⊙, are dense (~6 × 104 cm-3), and can thus be described as molecular cloud “cores”. All pillars and globules are oriented toward the Cyg OB2 association center and have the longest estimated photoevaporation lifetimes, a few million years, while all other features should survive less than a million years. These lifetimes are consistent with that found in simulations of turbulent, UV-illuminated clouds. We propose a tentative evolutionary scheme in which pillars can evolve into globules, which in turn then evolve into EGGs, condensations and proplyd-like objects. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

Schneider, N.;Bontemps, S.;Motte, F.;Blazere, A.;André, Ph.;Anderson, L. D.;Arzoumanian, D.;Comerón, F.;Didelon, P.;Di Francesco, J.;Duarte-Cabral, A.;Guarcello , M. G.;Hennemann, M.;Hill, T.;Könyves, V.;Marston, A.;Minier, V.;Rygl, K. L. J.;Röllig, M.;Roy, A.;Spinoglio, L.;Tremblin, P.;White, G. J.;Wright, N. J.
Astronomy & Astrophysics, Volume 591, id.A40, 21 pp.
Jun 2016

2015

1. X-Ray Emission from Massive Stars in Cyg OB2 ADS CITATION
Abstract

We report on the analysis of the Chandra-ACIS data of O, B, and WR stars in the young association Cyg OB2. X-ray spectra of 49 O-stars, 54 B-stars, and 3 WR-stars are analyzed and for the brighter sources, the epoch dependence of the X-ray fluxes is investigated. The O-stars in Cyg OB2 follow a well-defined scaling relation between their X-ray and bolometric luminosities: {log}\\frac{{L}{{X}}}{{L}{bol}}=-7.2+/- 0.2. This relation is in excellent agreement with the one previously derived for the Carina OB1 association. Except for the brightest O-star binaries, there is no general X-ray overluminosity due to colliding winds in O-star binaries. Roughly half of the known B-stars in the surveyed field are detected, but they fail to display a clear relationship between LX and Lbol. Out of the three WR stars in Cyg OB2, probably only WR 144 is itself responsible for the observed level of X-ray emission, at a very low {log}\\frac{{L}{{X}}}{{L}{bol}}=-8.8+/- 0.2. The X-ray emission of the other two WR-stars (WR 145 and 146) is most probably due to their O-type companion along with a moderate contribution from a wind-wind interaction zone.

Rauw, G.;Nazé, Y.;Wright, N. J.;Drake, J. J.;Guarcello , M. G.;Prinja, R. K.;Peck, L. W.;Albacete Colombo, J. F.;Herrero, A.;Kobulnicky, H. A.;Sciortino, S.;Vink, J. S.
The Astrophysical Journal Supplement Series, Volume 221, Issue 1, article id. 1, 20 pp. (2015).
Nov 2015

2014

1. Accretion and Outflow in the Proplyd-like Objects Near Cygnus OB2 ADS CITATION
Abstract

Cygnus OB2 is the most massive association within 2 kpc from the Sun, hosting hundreds of massive stars, thousands of young low mass members, and some sights of active star formation in the surrounding cloud. Recently, 10 photoevaporating proplyd-like objects with tadpole-shaped morphology were discovered in the outskirts of the OB association, approximately 6-14 pc away from its center. The classification of these objects is ambiguous, being either evaporating residuals of the parental cloud that are hosting a protostar inside or disk-bearing stars with an evaporating disk, such as the evaporating proplyds observed in the Trapezium Cluster in Orion. In this paper, we present a study based on low-resolution optical spectroscopic observations made with the Optical System for Imaging and low Resolution Integrated Spectroscopy, mounted on the 10.4 m Gran Telescopio CANARIAS, of two of these protostars. The spectrum of one of the objects shows evidence of accretion but not of outflows. In the latter object, the spectra show several emission lines indicating the presence of an actively accreting disk with outflow. We present estimates of the mass loss rate and the accretion rate from the disk, showing that the former exceeds the latter as observed in other known objects with evaporating disks. We also show evidence of a strong variability in the integrated flux observed in these objects as well as in the accretion and outflow diagnostics.

Guarcello , M. G.;Drake, J. J.;Wright, N. J.;García-Alvarez, D.;Kraemer, K. E.
The Astrophysical Journal, Volume 793, Issue 1, article id. 56, 14 pp. (2014).
Sep 2014

2013

1. Pre-main-sequence stars older than 8 Myr in the Eagle nebula ADS CITATION
Abstract

Attention is given to a population of 110 stars in the NGC 6611 cluster of the Eagle nebula that have prominent near-infrared excess and optical colours typical of pre-main-sequence (PMS) stars older than 8 Myr. At least half of those for which spectroscopy exists have a Hα emission line profile revealing active accretion. In principle, the V – I colours of all these stars would be consistent with those of young PMS objects (<1 Myr) whose radiation is heavily obscured by a circumstellar disc seen at high inclination and in small part scattered towards the observer by the back side of the disc. However, using theoretical models it is shown here that objects of this type can only account for a few per cent of this population. In fact, the spatial distribution of these objects, their X-ray luminosities, their optical brightness, their positions in the colour-magnitude diagram and the weak Li absorption lines of the stars studied spectroscopically suggest that most of them are at least eight times older than the ˜1 Myr-old PMS stars already known in this cluster and could be as old as ˜30 Myr. This is the largest homogeneous sample to date of Galactic PMS stars considerably older than 8 Myr that are still actively accreting from a circumstellar disc and it allows us to set a lower limit of 7 per cent to the disc frequency at ˜16 Myr in NGC 6611. These values imply a characteristic exponential lifetime of ˜6 Myr for disc dissipation.

De Marchi, Guido;Panagia, Nino;Guarcello , M. G.;Bonito, Rosaria
Monthly Notices of the Royal Astronomical Society, Volume 435, Issue 4, p.3058-3070
Nov 2013
2. Spectroscopic observations of blue stars with infrared excesses in NGC 6611 ADS CITATION
Abstract

Context. The young open cluster NGC 6611 includes a group of peculiar objects with interesting properties among its candidate members: blue stars with infrared (IR) excesses. These stars show excesses in IR bands, a signature of the presence of a circumstellar disk, but optical colors typical of older field stars. To confirm their membership in the cluster, it is therefore important to use new spectroscopic observations, together with previous photometric data. Aims: We aim to confirm the membership of these objects and investigate their physical properties to verify whether the observed colors are intrinsic or altered by the disk or by the accretion processes. Methods: We analyzed the intermediate-resolution spectroscopic data obtained for a subsample of blue stars in NGC 6611 with FLAMES. In particular, we focused on the study of 1) the profile of the Hα emission line, to select stars with accretion and outflow activity; 2) the Li absorption line, used as a youth indicator; 3) the radial velocity. Results: Using the spectroscopic analysis, it has been possible to investigate the Li absorption line, as well as to distinguish between stars with inert or active disks. In particular, from the analysis of the Hα emission line we were able to infer the activity due to the accretion and outflow processes and the variability of the emission. We also investigated the binarity of the blue stars and their membership to NGC 6611. Conclusions: From our spectroscopic analysis, we conclude that half of the sample of blue stars (10/20) are confirmed members of NGC 6611 (with 6 more stars that could also be possible members). In conclusion, our results indicate that members of young clusters can also be found in an anomalous region of the color-magnitude diagram, i.e., outside of the pre-main sequence locus where most of the cluster members lie.

Bonito, R.;Prisinzano, L.;Guarcello , M. G.;Micela, G.
Astronomy & Astrophysics, Volume 556, id.A108, 10 pp.
Aug 2013
3. The Protoplanetary Disks in the Nearby Massive Star-forming Region Cygnus OB2 ADS CITATION
Abstract

The formation of stars in massive clusters is one of the main modes of the star formation process. However, the study of massive star-forming regions is hampered by their typically large distances to the Sun. One exception to this is the massive star-forming region Cygnus OB2 in the Cygnus X region, at the distance of ~1400 pc. Cygnus OB2 hosts very rich populations of massive and low-mass stars, being the best target in our Galaxy to study the formation of stars, circumstellar disks, and planets in the presence of massive stars. In this paper, we combine a wide and deep set of photometric data, from the r band to 24 μm, in order to select the disk-bearing population of stars in Cygnus OB2 and identify the class I, class II, and stars with transition and pre-transition disks. We selected 1843 sources with infrared excesses in an area of 1° × 1° centered on Cyg OB2 in several evolutionary stages: 8.4% class I, 13.1% flat-spectrum sources, 72.9% class II, 2.3% pre-transition disks, and 3.3% transition disks. The spatial distribution of these sources shows a central cluster surrounded by an annular overdensity and some clumps of recent star formation in the outer region. Several candidate subclusters are identified, both along the overdensity and in the rest of the association.

Guarcello , M. G.;Drake, J. J.;Wright, N. J.;Drew, J. E.;Gutermuth, R. A.;Hora, J. L.;Naylor, T.;Aldcroft, T.;Fruscione, A.;García-Alvarez, D.;Kashyap, V. L.;King, R.
The Astrophysical Journal, Volume 773, Issue 2, article id. 135, 24 pp. (2013).
Aug 2013

2012

1. Optical Photometric GTC/OSIRIS Observations of the Young Massive Association Cygnus OB2 ADS CITATION
Abstract

In order to fully understand the gravitational collapse of molecular clouds, the star formation process, and the evolution of circumstellar disks, these phenomena must be studied in different Galactic environments with a range of stellar contents and positions in the Galaxy. The young massive association Cygnus OB2, in the Cygnus-X region, is a unique target to study how star formation and the evolution of circumstellar disks proceed in the presence of a large number of massive stars. We present a catalog obtained with recent optical observations in the r, i, z filters with OSIRIS, mounted on the 10.4 m Gran Telescopio CANARIAS telescope, which is the deepest optical catalog of Cyg OB2 to date. The catalog consists of 64,157 sources down to M = 0.15 M ⊙ at the adopted distance and age of Cyg OB2. A total of 38,300 sources have good photometry in all three bands. We combined the optical catalog with existing X-ray data of this region, in order to define the cluster locus in the optical diagrams. The cluster locus in the r – i versus i – z diagram is compatible with an extinction of the optically selected cluster members in the 2.64 m < AV < 5.57 m range. We derive an extinction map of the region, finding a median value of AV = 4.33 m in the center of the association, decreasing toward the northwest. In the color-magnitude diagrams, the shape of the distribution of main-sequence stars is compatible with the presence of an obscuring cloud in the foreground ~850 ± 25 pc from the Sun.

Guarcello , M. G.;Wright, N. J.;Drake, J. J.;García-Alvarez, D.;Drew, J. E.;Aldcroft, T.;Kashyap, V. L.
The Astrophysical Journal Supplement, Volume 202, Issue 2, article id. 19, 12 pp. (2012).
Oct 2012
2. Chandra/ACIS-I Study of the X-Ray Properties of the NGC 6611 and M16 Stellar Populations ADS CITATION
Abstract

Mechanisms regulating the origin of X-rays in young stellar objects and the correlation with their evolutionary stage are under debate. Studies of the X-ray properties in young clusters allow us to understand these mechanisms. One ideal target for this analysis is the Eagle Nebula (M16), with its central cluster NGC 6611. At 1750 pc from the Sun, it harbors 93 OB stars, together with a population of low-mass stars from embedded protostars to disk-less Class III objects, with age <=3 Myr. We study an archival 78 ks Chandra/ACIS-I observation of NGC 6611 and two new 80 ks observations of the outer region of M16, one centered on the Column V and the other on a region of the molecular cloud with ongoing star formation. We detect 1755 point sources with 1183 candidate cluster members (219 disk-bearing and 964 disk-less). We study the global X-ray properties of M16 and compare them with those of the Orion Nebula Cluster. We also compare the level of X-ray emission of Class II and Class III stars and analyze the X-ray spectral properties of OB stars. Our study supports the lower level of X-ray activity for the disk-bearing stars with respect to the disk-less members. The X-ray luminosity function (XLF) of M16 is similar to that of Orion, supporting the universality of the XLF in young clusters. Eighty-five percent of the O stars of NGC 6611 have been detected in X-rays. With only one possible exception, they show soft spectra with no hard components, indicating that mechanisms for the production of hard X-ray emission in O stars are not operating in NGC 6611.

Guarcello , M. G.;Caramazza, M.;Micela, G.;Sciortino, S.;Drake, J. J.;Prisinzano, L.
The Astrophysical Journal, Volume 753, Issue 2, article id. 117, 16 pp. (2012).
Jul 2012
3. The radial distribution of dust species in young brown dwarf discs ADS CITATION
Abstract

We present a study of the radial distribution of dust species in young brown dwarf discs. Our work is based on a compositional analysis of the 10 and 20 μm silicate emission features for brown dwarfs in the Taurus-Auriga star-forming region. A fundamental finding of our work is that brown dwarfs exhibit stronger signs of dust processing in the cold component of the disc, compared to the higher mass T Tauri stars in Taurus. For nearly all of our targets, we find a flat disc structure, which is consistent with the stronger signs of dust processing observed in these discs. For the case of one brown dwarf, 2M04230607, we find the forsterite mass fraction to be a factor of ˜3 higher in the outer disc compared to the inner disc region. Simple large-scale radial mixing cannot account for this gradient in the dust chemical composition, and some local crystalline formation mechanism may be effective in this disc. The relatively high abundance of crystalline silicates in the outer cold regions of brown dwarf discs provides an interesting analogy to comets. In this context, we have discussed the applicability of the various mechanisms that have been proposed for comets on the formation and the outward transport of high-temperature material. We also present Chandra X-ray observations for two Taurus brown dwarfs, 2M04414825 and CFHT-BD-Tau 9. We find 2M04414825, which has an ˜12 per cent crystalline mass fraction, to be more than an order of magnitude brighter in X-ray than CFHT-BD-Tau 9, which has an ˜35 per cent crystalline mass fraction. Combining with previous X-ray data, we find the inner disc crystalline mass fractions to be anti-correlated with the X-ray strength.

Riaz, B.;Honda, M.;Campins, H.;Micela, G.;Guarcello , M. G.;Gledhill, T.;Hough, J.;Martín, E. L.
Monthly Notices of the Royal Astronomical Society, Volume 420, Issue 3, pp. 2603-2624.
Mar 2012
4. Photoevaporating Proplyd-like Objects in Cygnus OB2 ADS CITATION
Abstract

We report the discovery of 10 proplyd-like objects in the vicinity of the massive OB association Cygnus OB2. They were discovered in IPHAS Hα images and are clearly resolved in broadband Hubble Space Telescope/Advanced Camera for Surveys, near-IR, and Spitzer mid-IR images. All exhibit the familiar tadpole shape seen in photoevaporating objects such as the Orion proplyds, with a bright ionization front at the head facing the central cluster of massive stars and a tail stretching in the opposite direction. Many also show secondary ionization fronts, complex tail morphologies, or multiple heads. We consider the evidence that these are either proplyds or “evaporating gaseous globules” (EGGs) left over from a fragmenting molecular cloud, but find that neither scenario fully explains the observations. Typical sizes are 50,000-100,000 AU, larger than the Orion proplyds, but in agreement with the theoretical scaling of proplyd size with distance from the ionizing source. These objects are located at projected separations of ~6-14 pc from the OB association, compared to ~0.1 pc for the Orion proplyds, but are clearly being photoionized by the ~65 O-type stars in Cyg OB2. Central star candidates are identified in near- and mid-IR images, supporting the proplyd scenario, though their large sizes and notable asymmetries are more consistent with the EGG scenario. A third possibility is therefore considered that these are a unique class of photoevaporating partially embedded young stellar objects that have survived the destruction of their natal molecular cloud. This has implications for the properties of stars that form in the vicinity of massive stars.

Wright, Nicholas J.;Drake, Jeremy J.;Drew, Janet E.;Guarcello , Mario G.;Gutermuth, Robert A.;Hora, Joseph L.;Kraemer, Kathleen E.
The Astrophysical Journal Letters, Volume 746, Issue 2, article id. L21, 7 pp. (2012).
Feb 2012

2011

1. Could CoRoT-7b and Kepler-10b be remnants of evaporated gas or ice giants? ADS CITATION
Abstract

We present thermal mass loss calculations over evolutionary time scales for the investigation if the smallest transiting rocky exoplanets CoRoT-7b (∼1.68REarth) and Kepler-10b (∼1.416REarth) could be remnants of an initially more massive hydrogen-rich gas giant or a hot Neptune-class exoplanet. We apply a thermal mass loss formula which yields results that are comparable to hydrodynamic loss models. Our approach considers the effect of the Roche lobe, realistic heating efficiencies and a radius scaling law derived from observations of hot Jupiters. We study the influence of the mean planetary density on the thermal mass loss by placing hypothetical exoplanets with the characteristics of Jupiter, Saturn, Neptune, and Uranus to the orbital location of CoRoT-7b at 0.017 AU and Kepler-10b at 0.01684 AU and assuming that these planets orbit a K- or G-type host star. Our findings indicate that hydrogen-rich gas giants within the mass domain of Saturn or Jupiter cannot thermally lose such an amount of mass that CoRoT-7b and Kepler-10b would result in a rocky residue. Moreover, our calculations show that the present time mass of both rocky exoplanets can be neither a result of evaporation of a hydrogen envelope of a “Hot Neptune” nor a “Hot Uranus”-class object. Depending on the initial density and mass, these planets most likely were always rocky planets which could lose a thin hydrogen envelope, but not cores of thermally evaporated initially much more massive and larger objects.

Leitzinger, M.;Odert, P.;Kulikov, Yu. N.;Lammer, H.;Wuchterl, G.;Penz, T.;Guarcello , M. G.;Micela, G.;Khodachenko, M. L.;Weingrill, J.;Hanslmeier, A.;Biernat, H. K.;Schneider, J.
Planetary and Space Science, Volume 59, Issue 13, p. 1472-1481.
Oct 2011
2. Star formation in the outer Galaxy: membership and fundamental parameters of the young open cluster NGC 1893 ADS CITATION
Abstract

Context. Different environmental conditions can play a crucial role in determining final products of the star formation process, and in this context, less favorable activities of star formation are expected in the external regions of our Galaxy. Aims: We studied the properties of the young open cluster NGC 1893 located about 12 Kpc from the galactic center, to investigate how different physical conditions can affect the process of star formation. Methods: By adopting a multiwavelength approach, we compiled a catalog extending from X-rays to NIR data to derive the cluster membership. In addition, optical and NIR photometric properties are used to evaluate the cluster parameters. Results: We find 415 diskless candidate members and 1061 young stellar objects with a circumstellar disk or class II candidate members, 125 of which are also Hα emitters. Considering the diskless candidate members, we find that the cluster distance is 3.6 ± 0.2 kpc and the mean interstellar reddening is E(B – V) = 0.6 ± 0.1 with evidence of differential reddening in the whole surveyed region. Conclusions: NGC 1893 contains a conspicuous population of pre-main sequence stars, together with the well-studied main sequence cluster population. We found a disk fraction of about 70% similar to the one found in clusters of similar age in the solar neighbor and then, despite expected unfavorable conditions for star formation, we conclude that very rich young clusters can also form in the outer regions of our Galaxy. Full Tables 5-8 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/527/A77

Prisinzano, L.;Sanz-Forcada, J.;Micela, G.;Caramazza, M.;Guarcello , M. G.;Sciortino, S.;Testi, L.
Astronomy & Astrophysics, Volume 527, id.A77, 19 pp.
Mar 2011

2010

1. Chronology of star formation and disk evolution in the Eagle Nebula ADS CITATION
Abstract

Context. Massive star-forming regions are characterized by intense ionizing fluxes, strong stellar winds and, occasionally, supernovae explosions, all of which have important effects on the surrounding media, on the star-formation process and on the evolution of young stars and their circumstellar disks. We present a multiband study of the massive young cluster NGC 6611 and its parental cloud (the Eagle Nebula) with the aim of studying how OB stars affect the early stellar evolution and the formation of other stars. Aims: We search for evidence of triggering of star formation by the massive stars inside NGC 6611 on a large spatial scale (~10 parsec) and ongoing disk photoevaporation in NGC 6611 and how its efficiency depends on the mass of the central stars. Methods: We assemble a multiband catalog of the Eagle Nebula with photometric data, ranging from B band to 8.0 μm, and X-ray data obtained with two new and one archival Chandra/ACIS-I observation. We select the stars with disks from infrared photometry and disk-less ones from X-ray emission, which are associated both with NGC 6611 and the outer region of the Eagle Nebula. We study induced photoevaporation searching for the spatial variation of disk frequency for distinct stellar mass ranges. The triggering of star formation by OB stars has been investigated by deriving the history of star formation across the nebula. Results: We find evidence of sequential star formation in the Eagle Nebula going from the southeast (2.6 Myears) to the northwest (0.3 Myears), with the median age of NGC 6611 members ~1 Myear. In NGC 6611, we observe a drop of the disk frequency close to massive stars (up to an average distance of 1 parsec), without observable effects at larger distances. Furthermore, disks are more frequent around low-mass stars (≤ 1 M⊙) than around high-mass stars, regardless of the distance from OB stars. Conclusions: The star-formation chronology we find in the Eagle Nebula does not support the hypothesis of a large-scale process triggered by OB stars in NGC 6611. Instead, we speculate that it was triggered by the encounter (about 3 Myears ago) with a giant molecular shell created by supernovae explosions about 6 Myears ago. We find evidence of disk photoevaporation close to OB stars, where disks are heated by incident extreme ultraviolet (EUV) radiation. No effects are observed at large distances from OB stars, where photoevaporation is induced by the far ultraviolet (FUV) radiation, and long timescales are usually required to completely dissipate the disks.

Guarcello , M. G.;Micela, G.;Peres, G.;Prisinzano, L.;Sciortino, S.
Astronomy and Astrophysics, Volume 521, id.A61, 17 pp.
Oct 2010
2. Pre-main sequence stars with disks in the Eagle Nebula observed in scattered light ADS CITATION
Abstract

Context. NGC 6611 and its parental cloud, the Eagle Nebula (M 16), are well-studied star-forming regions, thanks to their large content of both OB stars and stars with disks and the observed ongoing star formation. In our previous studies of the Eagle Nebula, we identified 834 disk-bearing stars associated with the cloud, after detecting their excesses in NIR bands from J band to 8.0 μ m. Aims: In this paper, we study in detail the nature of a subsample of disk-bearing stars that show peculiar characteristics. They appear older than the other members in the V vs. V-I diagram, and/or they have one or more IRAC colors at pure photospheric values, despite showing NIR excesses, when optical and infrared colors are compared. Methods: We confirm the membership of these stars to M 16 by a spectroscopic analysis. The physical properties of these stars with disks are studied by comparing their spectral energy distributions (SEDs) with the SEDs predicted by models of T Tauri stars with disks and envelopes. Results: We show that the age of these stars estimated from the V vs. V-I diagram is unreliable since their V-I colors are altered by the light scattered by the disk into the line of sight. Only in a few cases their SEDs are compatible with models with excesses in V band caused by optical veiling. Candidate members with disks and photospheric IRAC colors are selected by the used NIR disk diagnostic, which is sensitive to moderate excesses, such as those produced by disks with low masses. In 1/3 of these cases, scattering of stellar flux by the disks can also be invoked. Conclusions: The photospheric light scattered by the disk grains into the line of sight can affect the derivation of physical parameters of Class II stars from photometric optical and NIR data. Besides, the disks diagnostic we defined are useful for selecting stars with disks, even those with moderate excesses or whose optical colors are altered by veiling or photospheric scattered light. Table with the data of the stars is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/521/A18

Guarcello , M. G.;Damiani, F.;Micela, G.;Peres, G.;Prisinzano, L.;Sciortino, S.
Astronomy and Astrophysics, Volume 521, id.A18, 9 pp.
Oct 2010

2009

1. Correlation between the spatial distribution of circumstellar disks and massive stars in the young open cluster NGC 6611. II. Cluster members selected with Spitzer/IRAC ADS CITATION
Abstract

Context: The observations of the proplyds in the Orion Nebula Cluster, exhibiting clear evidence of ongoing photoevaporation, have provided clear proof of the role of externally induced photoevaporation in the evolution of circumstellar disks. NGC 6611 is an open cluster suitable for study of disk photoevaporation, due to its significant population of massive members and stars with disk. In a previous paper, we obtained evidence of the influence of the strong UV field generated by the massive cluster members on the evolution of disks around low-mass Pre-Main Sequence members. Our study was based on a multiband BVIJHK and X-ray catalog compiled for the purpose of selecting cluster members with and without disk. Aims: We attempt to complete the list of candidate cluster members, using data at longer wavelengths obtained with Spitzer/IRAC, and we reinvestigate the effects of UV radiation on the evolution of disks in NGC 6611. Methods: In a field of view of 33’×34′ centered on the cluster, we select the candidate members with disks of NGC 6611 using IRAC color-color diagrams and suitable reddening-free color indices. Using the X-ray data to select Class III cluster members, we also estimate disks frequency relative to the intensity of the incident radiation emitted by massive members. Results: We identify 458 candidate members with circumstellar disks, among which 146 had not been discovered previously. By comparing all color indices used to select cluster members with disk, we claim that these indices measure the excess of radiation due to the emission of the same physical region of the disk (i.e. the inner rim at the dust sublimation radius). Our new results confirm that UV radiation from massive stars affects the evolution of nearby circumstellar disks. Optical-infrared catalog of the candidate members of the open cluster NGC 6611 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/496/453

Guarcello , M. G.;Micela, G.;Damiani, F.;Peres, G.;Prisinzano, L.;Sciortino, S.
Astronomy and Astrophysics, Volume 496, Issue 2, 2009, pp.453-463
Mar 2009
2. Star formation in massive cluster: a multiwavelength study of the Eagle Nebula
Abstract

Not Available

Guarcello, Mario
Thesis (Ph.D.)-- SAO, 2009. Advisor N/A
n/a 2009

2007

1. Correlation between the spatial distribution of circumstellar disks and massive stars in the open cluster NGC 6611. Compiled catalog and cluster parameters ADS CITATION
Abstract

Context: The observation of young stars with circumstellar disks suggests that the disks are dissipated, starting from the inner region, by the radiation of the central star and eventually by the formation of rocky planetesimals, over a time scale of several million years. It was also shown that strong UV radiation emitted by nearby massive stars can heat a circumstellar disk up to some thousand degrees, inducing the photoevaporation of the gas. This process strongly reduces the dissipation time scale. Aims: We study whether there exists a correlation between the spatial distribution of stars with circumstellar disks and the position of massive stars with spectral class earlier than B5, in the open cluster NGC 6611. Methods: We created a multiband catalog of the cluster, down to V˜ 23^m, using optical data from a WFI observation at 2.2 m of ESO in the BVI bands, the 2MASS public point source catalog and an archival X-ray observation made with CHANDRA/ACIS. We selected the stars with infrared excess (due to the emission of a circumstellar disk) using suitable color indices independent of extinction, and studied their spatial distribution. Results: The spatial distribution of the stars with K band excess (due to the presence of a circumstellar disk) is anti correlated with that of the massive stars: the disks are more frequent at large distances from these stars. We argue that this is in agreement with the hypothesis that the circumstellar disks are heated by the UV radiation from the massive stars and photoevaporated. Based on observations made with the European Observatory telescopes obtained from the ESO/ST-ECF Science Archive Facility. Table 3 and Appendix are only available in electronic form at http://www.aanda.org

Guarcello , M. G.;Prisinzano, L.;Micela, G.;Damiani, F.;Peres, G.;Sciortino, S.
Astronomy and Astrophysics, Volume 462, Issue 1, January IV 2007, pp.245-255
Jan 2007

2019

1. The Gaia-ESO Survey: age spread in the star forming region NGC6530 from the HR diagram and gravity indicators ADS
Abstract

In very young clusters, stellar age distribution is the empirical proof of the duration of star formation (SF) and of the physical mechanisms involved in the process. We derived accurate stellar ages for the cluster NGC6530, associated with the Lagoon Nebula to infer its SF history. We use the Gaia-ESO survey observations and Gaia DR2 data, to derive cluster membership and fundamental stellar parameters. We identified 652 confirmed and 9 probable members. The reddening inferred for members and non-members allows us to distinguish MS stars and giants, in agreement with the distances inferred from Gaia DR2 data. The foreground and background stars show a spatial pattern that traces the 3D structure of the nebular dust component. We derive stellar ages for 382 confirmed cluster members and we find that the gravity-sensitive gamma index distribution for M stars is correlated with stellar age. For all members with Teff<5500 K, the mean logarithmic age is 5.84 (units of years) with a dispersion of 0.36 dex. The age distribution of stars with accretion and/or disk (CTTSe) is similar to that of stars without accretion and without disk (WTTSp). We interpret this dispersion as evidence of a real age spread since the total uncertainties on age determinations, derived from Monte Carlo simulations, are significantly smaller than the observed spread. This conclusion is supported by the evidence of a decreasing of the gravity-sensitive gamma index as a function of stellar ages. The presence of the age spread is also supported by the spatial distribution and the kinematics of old and young members. In particular, members with accretion and/or disk, formed in the last 1 Myr, show evidence of subclustering around the cluster center, in the Hourglass Nebula and in the M8-E region, suggesting a possible triggering of star formation events by the O-type star ionization fronts.

Prisinzano, L.;Damiani, F.;Kalari, V.;Jeffries, R.;Bonito, R.;Micela, G.;Wright, N. J.;Jackson, R. J.;Tognelli, E.;Guarcello , M. G.;Vink, J. S.;Klutsch, A.;Jiménez-Esteban, F. M.;Roccatagliata, V.;Tautvaišienė, G.;Gilmore, G.;Randich, S.;Alfaro, E. J.;Flaccomio, E.;Koposov, S.;Lanzafame, A.;Pancino, E.;Bergemann, M.;Carraro, G.;Franciosini, E.;Frasca, A.;Gonneau, A.;Hourihane, A.;Jofré, P.;Lewis, J.;Magrini, L.;Monaco, L.;Morbidelli, L.;Sacco, G. G.;Worley, C. C.;Zaggia, S.
eprint arXiv:1901.09589
Jan 2019

2018

1. Photoevaporation and close encounters: how the environment around Cygnus OB2 affects the evolution of protoplanetary disks ADS
Abstract

Cygnus OB2 is the most massive stellar association within 2 kpc from the Sun. Given its large content of massive stars, counting tens of O and 3 WR stars, and thousands of young low mass stars, Cygnus OB2 is the best target to study how massive stars affect the star formation process in the parental cloud and the evolution of nearby protoplanetary disks. I will present the results of our study on the feedback provided by the environment in Cygnus OB2 on disk evolution, combining the X-ray data from the 1.08 Msec Chandra Cygnus OB2 Legacy Project (P.I. J. J. Drake) with an extensive set of optical and infrared data of the association. I will analyze and compare the destructive feedback provided by disk photoevaporation induced by the intense local UV field and close encounters between members of the association, and I will show evidence indicating that disk evolution in an environment similar to Cygnus OB2 is seriously affected by externally induced photoevaporation while close encounters do not provide an important feedback.

Guarcello, Mario
Protoplanetary disks seen through the eyes of new-generation high-resolution instruments. Proceedings of the conference held 25-28 June, 2018 in Rome, Italy. Online at https://indico.ict.inaf.it/event/631/, id. 27.
Dec 2018
2. Young Stars and their Variability with LSST ADS
Abstract

Young stars exhibit short-term photometric variability caused by mass accretion events from circumstellar disks, the presence of dusty warps within the inner disks, starspots that rotate across the stellar surfaces, and flares. Long-term variability also occurs owing to starspot longevity and cycles, and from changes in stellar angular momenta and activity as the stars age. We propose to observe the Carina star-forming region in different bands with a cadence of 30 minutes every night for one week per year to clarify the nature of both the short-term and long-term variability of the thousands of young stars in this region. By obtaining well-sampled multicolor lightcurves of this dense young cluster, LSST would acquire the first statistically significant data on how these objects vary on both short and long timescales. This information will allow us to relate the observed variability to stellar properties such as mass, age, binarity, and to environmental properties such as location within or exterior to the H II region, and to the presence or absence of a circumstellar disk.

Rosaria;Bonito;Hartigan, Patrick;Venuti, Laura;Guarcello , Mario;Prisinzano, Loredana;Argiroffi, Costanza;Messina, Sergio;Johns-Krull, Christopher;Feigelson, Eric;Stauffer, John;Giannini, Teresa;Antoniucci, Simone;Sciortino, Salvo;Micela, Giusi;Pillitteri, Ignazio;Fedele, Davide;Podio, Linda;Damiani, Francesco;McGehee, Peregrine;Street, Rachel;Gizis, John;Sacco, Germano;Magrini, Laura;Flaccomio, Ettore;Orlando, Salvatore;Miceli, Marco;Stelzer, Beate;Fuchs, Julien;Chen, Sophia;Pikuz, Sergey;Frasca, Antonio;Biazzo, Katia;Codella, Claudio;Pastorello, Andrea;Alcala
eprint arXiv:1812.03135
Dec 2018
3. Investigating the population of Galactic star formation regions and star clusters within a Wide-Fast-Deep Coverage of the Galactic Plane ADS CITATION
Abstract

One of the aims of LSST is to perform a systematic survey of star clusters and star forming regions (SFRs) in our Galaxy. In particular, the observations obtained with LSST will make a big difference in Galactic regions that have been poorly studied in the past, such as the anticenter and the disk beyond the Galactic center, and they will have a strong impact in discovering new distant SFRs. These results can be achieved by exploiting the exquisite depth that will be attained if the wide-fast-deep (WFD) observing strategy of the main survey is also adopted for the Galactic plane, in the g, r, and i filters.

Prisinzano, L.;Magrini, L.;Damiani, F.;Sacco, G.;Bonito, R.;Venuti, L.;Casali, G.;Roccatagliata, V.;Randich, S.;Inno, L.;Cantat-Gaudin, T.;Minniti, D.;Bragaglia, A.;Degli Innocenti, S.;Prada Moroni, P. G.;Tognelli, E.;Sollima, A.;Vallenari, A.;Guarcello , M.;Messina, S.;Micela, G.;Sciortino, S.;Spagna, A.;Sanna, N.;Kastner, J.;Roman, A.;Szabo, R.;Dias, B.;Feigelson, E.;Jeffries, R.;Friel, E.;Stauffer, J.;Van der Swaelmen, M.;Sordo, R.;Bossini, D.
eprint arXiv:1812.03025
Dec 2018
4. X-ray spectral characterization of the young Cygnus OB2 population ADS
Abstract

We analyze the X-ray spectra of the $\sim$8000 sources detected in the Cygnus OB2 Chandra Legacy Survey (Drake et al., this issue), with the goals of characterizing the coronal plasma of the young low-mass stars in the region and estimating their intrinsic X-ray luminosities. We adopt two different strategies for X-ray sources for which more or less than 20 photons were detected. For the brighter sample we fit the spectra with absorbed isothermal models. In order to limit uncertainties, for most of the fainter Cygnus OB2 members in this sample, we constrain the spectral parameters to characteristic ranges defined from the brightest stars. For X-ray sources with $<$20 net photons we adopt a conversion factor from detected photon flux to intrinsic flux. This was defined, building on the results for the previous sample, as a function of the 20% quantile of the detected photon energy distributions, which we prove to also correlate well with extinction. We then use the X-ray extinction from the spectral fits to constrain the ratio between optical and X-ray extinction toward Cygnus OB2, finding it consistent with standard "Galactic"' values, when properly accounting for systematics. Finally we exploit the large number of sources to constrain the average coronal abundances of several elements, through two different ensemble analyses of the X-ray spectra of low-mass Cygnus OB2 members. We find the pattern of abundances to be largely consistent with that derived for the young stellar coronae in the Orion Nebula Cluster.

Flaccomio, E.;Albacete-Colombo, J. F.;Drake, J. J.;Guarcello , M. G.;Kashyap, V.;Wright, N. J.;Briggs, K.;Ercolano, B.;Mccollogh, M.;Sciortino, S.
eprint arXiv:1811.06769
Nov 2018
5. VizieR Online Data Catalog: Magnetic flaring from PMS stars spectra (Flaccomio+, 2018) ADS
Abstract

Tables are provided with the data to reproduce figure B.1. in the paper, showing the lightcurves of flares observed simultaneously in the Chandra X-ray band, and in the CoRoT (optical) and/or Spitzer (mIR) bands. Up to four tables are included for each of the 75 panels in the figure: the CoRoT lightcurve, the Spitzer lightcurve, and the Chandra lightcurve, binned using both a fixed bin duration (indicated in the File Summary below as “bin”) and the “natural binning” Maximum-Likelihood algorithm described in the text (indicated as “blk”). For the CoRoT and Spitzer lightcurves, polynomial expressions representing the non-flaring emission during flares, derived as described in the text, are reported in the header of the relative text files, along with time intervals used to derived time-integrated flare emission. (5 data files).

Flaccomio, E.;Micela, G.;Sciortino, S.;Cody, A. M.;Guarcello , M. G.;Morales-Calderon, M.;Rebull, L.;Stauffer, J. R.
VizieR On-line Data Catalog: J/A+A/620/A55. Originally published in: 2018A&A...620A..55F
Sep 2018
6. Observational sites characterization for the Fly-Eye survey telescope ADS
Abstract

The issue of protecting ground infrastructures and space assets from the hazards coming from space, i.e. space debris, Near-Earth-Objects (NEO) and Space Weather, has recently gained momentum. In Europe it is addressed by the Space Situational Awareness Programme (SSA) of the European Space Agency (ESA) as well as at European Commission level. Within this framework it is foreseen the deployment of a European network of sensors for the detection of space objects able to trigger and support impact monitoring activities. The so-called “Fly-Eye” telescope with its unique optical design guaranteeing a wide-field (6.7°x6.7° FoV) and a high-sensitivity (down to 21.5 visual magnitude) is a key element to this end. In survey mode this telescope allows to timely detect small NEOs approaching the Earth and to efficiently catalogue space debris in a wide range of orbital regimes, from high LEO (Low-Earth Orbit) up to the geostationary ring. The first-light of the ESA SSA Fly-Eye telescope devoted to NEO survey is expected by end 2019. In order to investigate observational sites in Italy which could satisfy the SSA observational requirements we have analyzed different locations taking into account sky pollution, cloud coverage and seeing values. Both space and ground-based data were used. Cloud coverage data have been obtained from Earth observation satellites at different scale resolution (MODIS ACQUA, MODIS TERRA, MSG) and epochs. Seeing evaluation is based on existing data and/or in-situ ground-based seeing monitor equipments. The sky brightness was estimated by using NOAA (VIIRS/DMSP) and World Atlas 2015 (F. Falchi et al. 2016) maps. Due to the peculiarity in which NEO and space debris survey are expected to operate, logistic considerations were also taken into account. We present the outcome of the resulting trade-off analysis which shows the advantages and drawbacks of each site, eventually leading to identify those which could satisfy the technical and operational needs of running a NEO/space debris based on Fly-eye telescopes.

Di Cecco, Alessandra;Micela, Giuseppina;Perozzi, Ettore;Bianco, Giuseppe;Marzo, Cosimo;Falvella, Maria Cristina;Buzzoni, Alberto;Di Paola, Andrea;Fierro, Davide;Guarcello, Mario Giuseppe
42nd COSPAR Scientific Assembly. Held 14-22 July 2018, in Pasadena, California, USA, Abstract id. S.3-14-18.
Jul 2018
7. VizieR Online Data Catalog: Star formation in the Vela Molecular Ridge (Prisinzano+, 2018) ADS
Abstract

Astrometric and photometric data used in this work come from the public APASS9 (Cat. II/336), VPHAS+ (Cat. II/341) and 2MASS (Cat. II/246) catalogs. In addition, we used TGAS Gaia DR1 (I/337) kinematic data and public X-ray data obtained by ROSAT High Resolution Imager (HRI, 1RXH, third Release, Cat. IX/28) and Chandra Data Archive (Wang et al., 2016, Cat. J/ApJS/224/40). In table 2 we present astrometry, photometry and membership information of the young stellar objects (YSO) selected with classical methods, that is, from Halpha, IR excesses, kinematics, and X-ray detection. In table 3 we present astrometry and photometry of the M-type YSOs, selected with the new photometry technique described in the paper. For these latter objects, we also give the extinction and the ages. (2 data files).

Prisinzano, L.;Damiani, F.;Guarcello , M. G.;Micela, G.;Sciortino, S.;Tognelli, E.;Venuti, L.
VizieR On-line Data Catalog: J/A+A/617/A63. Originally published in: 2018A&A...617A..63P
Jun 2018
8. Diffuse X-ray emission in the Cygnus OB2 association ADS
Abstract

We present a large-scale study of diffuse X-ray emission in the nearby massive stellar association Cygnus OB2 as part of the Chandra Cygnus OB2 Legacy Program. We used 40 Chandra X-ray ACIS-I observations covering $\sim$1.0 deg$^2$. After removing 7924 point-like sources detected in our survey, background-corrected X-ray emission, the adaptive smoothing reveals large-scale diffuse X-ray emission. Diffuse emission was detected in the sub-bands Soft [0.5 : 1.2] and Medium [1.2 : 2.5], and marginally in the Hard [2.5 : 7.0] keV band. From X-ray spectral analysis of stacked spectra we compute a total [0.5 : 7.0 keV] diffuse X-ray luminosity of L$_{\rm x}^{\rm diff}\approx$4.2$\times$10$^{\rm 34}$ erg s$^{-1}$, characterized with plasma temperature components at kT$\approx$ 0.11, 0.40 and 1.18 keV, respectively. The HI absorption column density corresponding to these temperatures has a distribution consistent with N$_{\rm H}$ = 0.43, 0.80 and 1.39 $\times$10$^{22}$ cm$^{-2}$. The extended medium band energy emission likely arises from O-type stellar winds thermalized by wind-wind collisions in the most populated regions of the association, while the soft band emission probably arises from less energetic termination shocks against the surrounding Interstellar-Medium. Super-soft and Soft diffuse emission appears more widely dispersed and intense than the medium band emission. The diffuse X-ray emission is generally spatially coincident with low-extinction regions that we attribute to the ubiquitous influence of powerful stellar winds from massive stars and their interaction with the local Interstellar-Medium. Diffuse X-ray emission is volume-filling, rather than edge-brightened, oppositely to other star-forming regions. We reveal the first observational evidence of X-ray haloes around some evolved massive stars.

Albacete Colombo, J. F.;Drake, J. J.;Flaccomio, E.;Wright, N. J.;Kashyap, V.;Guarcello , M. G.;Briggs, K.;Drew, J. E.;Fenech, D. M.;Micela, G.;McCollough, M.;Prinja, R. K.;Schneider, N.;Sciortino, S.;Vink, J. S.
eprint arXiv:1806.01231
Jun 2018

2017

1. Time resolved X-ray spectral analysis during optical dips and accretion bursts in stars with disks of NGC 2264 from Chandra/ACIS-I and CoRoT data ADS
Abstract

The simultaneous X-ray and optical observations with excellent time resolution of T Tauri stars with disks may provide insight on the accretion process and the properties of the inner disk. This was one of the motivations of the CSI 2264 campaign. In this talk I will show the results obtained from time resolved X-ray spectral analysis from deep Chandra/ACIS-I observations during the optical dips and accretion bursts isolated in the CoRoT light curves of the disk-bearing members of NGC 2264. These simultaneous Chandra-CoRoT data allow us to find evidence of increasing X-ray absorption during the optical dips, to study the composition of the material responsible for the variable extinction in these stars with disks, and to find evidence for soft X-ray emission observed during the optical bursts, and thus related to the accretion process.

Guarcello , M.;Flaccomio, E.;Micela, G.;Argiroffi, C.;Sciortino, S.;Venuti, L.;Stauffer, J.;Rebull, L.;Cody, A.
The X-ray Universe 2017, Proceedings of the conference held 6-9 June, 2017 in Rome, Italy. Edited by J.-U. Ness and S. Migliari. Online at https://www.cosmos.esa.int/web/xmm-newton/2017-symposium, p.92
Oct 2017
2. VizieR Online Data Catalog: NGC2264 structure and star formation history (Venuti+, 2018) ADS
Abstract

We aim to explore the structure of the open cluster and star-forming region NGC 2264 (3 Myr), and to reconstruct its star formation history. Our study focuses on a sample of 655 young stars in the region. We employed spectroscopic data from the Gaia-ESO Survey and multi-wavelength photometry from the CSI 2264 campaign to: i) derive individual extinction and stellar parameters (mass, age) for cluster members; ii) classify the evolutionary status of the objects (disk-bearing/disk-free, accreting/non-accreting); iii) explore the nature of young stars at different locations within the cluster as a function of age. In tableb1, we provide the following information: object identifiers in the Gaia-ESO Survey and CSI 2264 catalogs; spatial coordinates; membership flag; g,r,i photometry; disk classification; accreting status; gamma-index; effective temperature; Lithium equivalent width (EW); Halpha EW and width at 10% intensity; photometric Halpha emission; UV excess; Av; bolometric luminosity; mass and age estimates. (1 data file).

Venuti, L.;Prisinzano, L.;Sacco, G. G.;Flaccomio, E.;Bonito, R.;Damiani, F.;Micela, G.;Guarcello , M. G.;Randich, S.;Stauffer, J. R.;Cody, A. M.;Jeffries, R. D.;Alencar, S. H. P.;Alfaro, E. J.;Lanzafame, A. C.;Pancino, E.;Bayo, A.;Carraro, G.;Costado, M. T.;Frasca, A.;Jofre, P.;Morbidelli, L.;Sousa, S. G.;Zaggia, S.
VizieR On-line Data Catalog: J/A+A/609/A10. Originally published in: 2018A&A...609A..10V
Sep 2017
3. VizieR Online Data Catalog: Rotational periods in Cygnus OB2 (Roquette+, 2017) ADS
Abstract

Our observational dataset was obtained with the 3.8m United Kingdom Infra-Red Telescope (UKIRT), at Manua Kea, Hawaii, equipped with the Wide Field Camera (WFCAM); the programs were U/07A/H16 and U/07B/H60. Our complete dataset is composed of up to 115 nights observed using the J, H, and K filters (Hewett et al., 2006MNRAS.367..454H). The observations were carried during 2007 in two seasons: The first season comprises 43 observed nights between April 1 and May 21; the second season comprises 73 observed nights between August 4 and November 3. The two observational seasons span a total of 217 days. The exposures were short, 2 seconds in each filter. Rotational periods for 894 Cygnus OB2 candidate members. For each star, an internal ID, IDs in Guarcello et al. (2013, Cat. J/ApJ/773/135) and Guarcello et al. (2015, arXiv:1501.03761), coordinates, Stetson variability index, period, estimated mass and reddening, median JHK magnitudes, median JHK photometric errors, peak-to- peak JHK amplitudes, and Disk class according to Guarcello et al. (2013, Cat. J/ApJ/773/135) ate presented. (1 data file).

Roquette, J.;Bouvier, J.;Alencar, S. H. P.;Vaz, L. P. R.;Guarcello, M. G.
VizieR On-line Data Catalog: J/A+A/603/A106. Originally published in: 2017A&A...603A.106R
May 2017
4. Age spread and sequential star formation in the young cluster NGC 2264 ADS
Abstract

We investigate the structure and star formation history of the NGC 2264 cluster (3 Myr). We combine spectroscopic T_eff with multi-color photometry to derive homogeneous extinction and stellar parameters for 655 cluster members (M_star = 0.2-1.8 M_⊙). We infer an intrinsic age spread of ˜4 Myr across the cluster. NGC 2264 members were born in the course of sequential star formation activity, which still continues in the most embedded regions of the cluster. We find evidence for photoevaporation effects driven by OB stars in the region that locally impact the timescales for disk evolution within the cluster.

Venuti, L.;Prisinzano, L.;Sacco, G.;Flaccomio, E.;Bonito, R.;Damiani, F.;Micela, G.;Guarcello , M.;GES Collaboration;CSI 2264 Collaboration
Memorie della Societa Astronomica Italiana, v.88, p.848 (2017)
n/a 2017

2016

1. Time Resolved X-Ray Spectral Analysis of Class II YSOs in NGC 2264 During Optical Dips and Bursts ADS
Abstract

Pre-Main Sequence stars are variable sources. The main mechanisms responsible for their variability are variable extinction, unsteady accretion, and rotational modulation of both hot and dark photospheric spots and X-ray active regions. In stars with disks this variability is thus related to the morphology of the inner circumstellar region (<0.1 AU) and that of photosphere and corona, all impossible to be spatially resolved with present day techniques. This has been the main motivations of the Coordinated Synoptic Investigation of NGC2264, a set of simultaneous observations of NGC2264 with 15 different telescopes.We analyze the X-ray spectral properties of stars with disks extracted during optical bursts and dips in order to unveil the nature of these phenomena. Stars are analyzed in two different samples. In stars with variable extinction a simultaneous increase of optical extinction and X-ray absorption is searched during the optical dips; in stars with accretion bursts we search for soft X-ray emission and increasing X-ray absorption during the bursts. In 9/33 stars with variable extinction we observe simultaneous increase of X-ray absorption and optical extinction. In seven dips it is possible to calculate the NH/AV ratio in order to infer the composition of the obscuring material. In 5/27 stars with optical accretion bursts, we observe soft X-ray emission during the bursts that we associate to the emission of accreting gas. It is not surprising that these properties are not observed in all the stars with dips and bursts since favorable geometric configurations are required. The observed variable absorption during the dips is mainly due to dust-free material in accretion streams. In stars with accretion bursts we observe in average a larger soft X-ray spectral component not observed in non accreting stars. This indicates that this soft X-ray emission arises from the accretion shocks.

Guarcello , Mario Giuseppe;Flaccomio, Ettore;Micela, Giuseppina;Argiroffi, Costanza;Venuti, Laura
The 19th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun (CS19), Uppsala, Sweden, 06-10 June 2016, id.99
Jul 2016
2. Photoevaporation and close encounters: how the environment around Cygnus OB2 affects the evolution of protoplanetary disks ADS CITATION
Abstract

In our Galaxy, star formation occurs in a variety of environments, with a large fraction of stars formed in clusters hosting massive stars. OB stars have an important feedback on the evolution of protoplanetary disks around nearby young stars and likely on the process of planet formation occurring in them. The nearby massive association Cygnus OB2 is an outstanding laboratory to study this feedback. It is the closest massive association to our Sun, and hosts hundreds of massive stars and thousands of low mass members. In this paper, we analyze the spatial variation of the disk fraction in Cygnus OB2 and we study its correlation with the local values of Far and Extreme ultraviolet radiation fields and the local stellar surface density. We present definitive evidence that disks are more rapidly dissipated in the regions of the association characterized by intense local UV field and large stellar density. In particular, the FUV radiation dominates disks dissipation timescales in the proximity (i.e. within 0.5 pc) of the O stars. In the rest of the association, EUV photons potentially induce a significant mass loss from the irradiated disks across the entire association, but the efficiency of this process is reduced at increasing distances from the massive stars due to absorption by the intervening intracluster material. We find that disk dissipation due to close stellar encounters is negligible in Cygnus OB2, and likely to have affected 1% or fewer of the stellar population. Disk dissipation is instead dominated by photoevaporation. We also compare our results to what has been found in other young clusters with different massive populations, concluding that massive associations like Cygnus OB2 are potentially hostile to protoplanetary disks, but that the environments where disks can safely evolve in planetary systems are likely quite common in our Galaxy.

Guarcello , M. G.;Drake, J. J.;Wright, N. J.;Albacete-Colombo, J. F.;Clarke, C.;Ercolano, B.;Flaccomio, E.;Kashyap, V.;Micela, G.;Naylor, T.;Schneider, N.;Sciortino, S.;Vink, J. S.
eprint arXiv:1605.01773
May 2016
3. The statistical uncertainties on X-ray flux and spectral parameters from Chandra ACIS-I observations of faint sources: Application to the Cygnus OB2 Association ADS CITATION
Abstract

We investigate the uncertainties of fitted X-ray model parameters and fluxes for relatively faint Chandra ACIS-I source spectra. Monte-Carlo (MC) simulations are employed to construct a large set of 150,000 fake X-ray spectra in the low photon count statistics regime (from 20 to 350 net counts) using the XSPEC spectral model fitting package. The simulations employed both absorbed thermal (APEC) and non-thermal (power-law) models, in concert with the Chandra ACIS-I instrument response and interstellar absorption. Simulated X-ray spectra were fit assuming a wide set of different input parameters and C-statistic minimization criteria to avoid numerical artifacts in the accepted solutions. Results provide an error estimate for each parameter (absorption, NH, plasma temperature, kT, or power-law slope, Gamma, and flux, and for different background contamination levels. The distributions of these errors are studied as a function of the 1 sigma quantiles and we show how these correlate with different model parameters, net counts in the spectra and relative background level. Maps of uncertainty in terms of the 1 sigma quantiles for parameters and flux are computed as a function of spectrum net counts. We find very good agreement between our estimated X-ray spectral parameter and flux uncertainties and those recovered from spectral fitting for a subset of the X-ray sources detected in the Chandra Cygnus OB2 Legacy Survey diagnosed to be Association members and that have between 20 and 350 net counts. Our method can provide uncertainties for spectral parameters whenever formal X-ray spectral fits cannot be well-constrained, or are unavailable, and predictions useful for computing Chandra ACIS-I exposure times for observation planning.

Albacete-Colombo, J. F.;Flaccomio, E.;Drake, J. J.;Wright, N. J.;Guarcello , M.;Kashyap, V.
eprint arXiv:1603.08372
Mar 2016

2015

1. Simulating the sensitivity to stellar point sources of Chandra X-ray observations ADS CITATION
Abstract

The Chandra Cygnus OB2 Legacy Survey is a wide and deep X-ray survey of the nearby and massive Cygnus OB2 association. The survey has detected ~8,000 X-ray sources, the majority of which are pre-main sequence X-ray emitting young stars in the association itself. To facilitate quantitative scientific studies of these sources as well as the underlying OB association it is important to understand the sensitivity of the observations and the level of completeness the observations have obtained. Here we describe the use of a hierarchical Monte Carlo simulation to achieve this goal by combining the empirical properties of the observations, analytic estimates of the source verification process, and an extensive set of source detection simulations. We find that our survey reaches a 90% completeness level for a pre-main-sequence population at the distance of Cyg OB2 at an X-ray luminosity of 4 x 10^30 ergs/s and a stellar mass of 1.3 Msun for a randomly distributed population. For a spatially clustered population such as Cyg~OB2 the 90% completeness level is reached at 1.1 Msun instead, as the sources are more concentrated in areas of our survey with a high exposure. These simulations can easily be adapted for use with other X-ray observations and surveys, and we provide X-ray detection efficiency curves for a very wide array of source and background properties to allow these simulations to be easily exploited by other users.

Wright, Nicholas J.;Drake, Jeremy J.;Guarcello , Mario G.;Kashyap, Vinay L.;Zezas, Andreas
eprint arXiv:1511.03943
Nov 2015
2. Cygnus OB2: Star Formation Ugly Duckling Causes a Flap ADS CITATION
Abstract

Cygnus OB2 is one of the largest known OB associations in our Galaxy, with a total stellar mass of 30,000 Msun and boasting an estimated 65 O-type stars and hundreds of OB stars. At a distance of only 1.4kpc, it is also the closest truly massive star forming region and provides a valuable testbed for star and planet formation theory. We have performed a deep stellar census using observations from X-ray to infrared, which has enabled studies of sub-structuring, mass segregation and dynamics, while infrared data reveal a story of protoplanetary disk attrition in an extremely harsh radiation environment. I will discuss how Cygnus OB2 challenges the idea that stars must form in dense, compact clusters, and demonstrates that stars as massive as 100 Msun can form in relatively low-density environments. Convincing evidence of disk photoevaporation poses a potential problem for planet formation and growth in starburst environments.

Drake, Jeremy J.;Wright, Nicholas;Guarcello, Mario
IAU General Assembly, Meeting #29, id.2258134
Aug 2015
3. Optical and infrared counterparts of the X-ray sources detected in the Chandra Cygnus OB2 Legacy Survey ADS CITATION
Abstract

The young massive OB association Cygnus OB2, in the Cygnus X complex, is the closest (1400 pc) star forming region to the Sun hosting thousands of young low mass stars and up to 1000 OB stars, among which are some of the most massive stars known in our Galaxy. This region holds great importance for several fields of modern astrophysics, such as the study of the physical properties of massive and young low-mass stars and the feedback provided by massive stars on star and planet formation process. Cygnus OB2 has been recently observed with Chandra/ACIS-I as part of the 1.08Msec Chandra Cygnus OB2 Legacy Project. This survey detected 7924 X-ray sources in a square degree area centered on Cyg OB2. Since a proper classification and study of the observed X-ray sources also requires the analysis of their optical and infrared counterparts, we combined a large and deep set of optical and infrared catalogs available for this region with our new X-ray catalog. In this paper we describe the matching procedure and present the combined catalog containing 5703 sources. We also briefly discuss the nature of the X-ray sources with optical and infrared counterparts using their position in the color-magnitude and color-color diagrams.

Guarcello , M. G.;Drake, J. J.;Wright, N. J.;Naylor, T.;Flaccomio, E.;Kashyap, V. L.;Garcia-Alvarez, D.
eprint arXiv:1501.03761
Jan 2015

2014

1. VizieR Online Data Catalog: VIc photometry of IR-excess stars in NGC6611 (De Marchi+ 2013) ADS
Abstract

The data analysed in this work were extracted from the multiband photometric catalogue of NGC 6611 and of the surrounding M 16 cloud compiled by Guarcello et al. (2010, Cat. J/A+A/521/A61). (1 data file).

de Marchi, G.;Panagia, N.;Guarcello , M. G.;Bonito, R.
VizieR On-line Data Catalog: J/MNRAS/435/3058. Originally published in: 2013MNRAS.435.3058D
Oct 2014
2. Cygnus OB2: Star Formation Ugly Duckling Causes a Flap ADS
Abstract

Cygnus OB2 is one of the largest known OB associations in our Galaxy, with a total stellar mass of 3×10^4 Msun and boasting an estimated 65O-type stars and hundreds of OB stars. At a distance of only 1.4kpc, it is also the closest truly massive star forming region and provides a valuable testbed for star and planet formation theories. Chandra’s megasecond 1 square degree survey of the association revealed about 8000 X-ray point sources, approximately 5750 of which have been identified with objects in optical and infrared surveys. The stellar census has enabled studies of sub-structuring, mass segregation anddynamics, while infrared data reveal a story of protoplanetary disk attrition in an extremely harsh radiation environment. We will discuss how Cygnus OB2 challenges the idea that stars must form in dense, compact clusters, and demonstrates that stars as massive as 100Msun can form in relatively low-density environments. Convincing evidence of disk photoevaporation poses a potential problem for planet formation and growth in starburst environments.

Drake, Jeremy J.;Guarcello , Mario G.;Wright, Nicholas James
American Astronomical Society, HEAD meeting #14, id.103.05
Aug 2014
3. The Chandra Cygnus OB2 Legacy Survey: Design and X-ray Point Source Catalog ADS CITATION
Abstract

The Cygnus OB2 association is the largest concentration of young and massive stars within 2 kpc of the Sun, including an estimated 65 O-type stars and hundreds of OB stars. The Chandra Cygnus OB2 Legacy Survey is a large imaging program undertaken with the Advanced CCD Imaging Spectrometer onboard the Chandra X-ray Observatory. The survey has imaged the central 0.5 deg^2 of the Cyg OB2 association with an effective exposure of 120ks and an outer 0.35 deg^2 area with an exposure of 60ks. Here we describe the survey design and observations, the data reduction and source detection, and present a catalog of 8,000 X-ray point sources. The survey design employs a grid of 36 heavily (~50%) overlapping pointings, a method that overcomes Chandra’s low off-axis sensitivity and produces a highly uniform exposure over the inner 0.5 deg^2. The full X-ray catalog is described here and is made available online.

Wright, Nicholas J.;Drake, Jeremy J.;Guarcello , Mario G.;Aldcroft, Tom L.;Kashyap, Vinay L.;Damiani, Francesco;DePasquale, Joe;Fruscione, Antonella
eprint arXiv:1408.6579
Aug 2014
4. The X-ray emission of the massive stars population in Cyg OB2 ADS
Abstract

Cygnus OB2 contains a wealth of massive stars of spectral types O, B and Wolf-Rayet. In the framework of a Chandra legacy program to study the X-ray emission from this important association, we have studied the X-ray properties of its massive stars population. We show that the O-stars in Cyg OB2 follow a well-defined scaling relation between their X-ray and bolometric luminosities: log(Lx/Lbol) = -7.2 ± 0.2. Except for the brightest O-star binaries, there is no general X-ray overluminosity due to colliding winds in O-star binaries. Roughly half of the known B-stars in the surveyed field are detected, but they fail to display a clear relationship between Lx and Lbol. Out of the three WR stars in Cyg OB2, probably only WR144 is itself responsible for the observed level of X-ray emission, at a very low log(Lx/Lbol) = -8.8 ± 0.2. The X-ray emission of the other two WR-stars (WR145 and 146) is most probably due to their O-type companion along with a moderate contribution from a wind-wind interaction zone.

Rauw, G.;Nazé, Y.;Wright, N.;Drake, J.;Guarcello , M.;Chandra Cygnus OB2 legacy survey Consortium
The X-ray Universe 2014, edited by Jan-Uwe Ness. Online at http://www.cosmos.esa.int/web/xmm-newton/2014-symposium/, id.307
Jul 2014
5. Disk Survival in the Extremely Massive Association Cygnus OB2 ADS
Abstract

Star formation in massive clusters proceeds under the influence of the intense ionizing flux emitted by OB stars. Among the massive star forming regions in our Galaxy, Cygnus OB2 is the best available target to study these processes given its relative proximity and large content of OB and low-mass stars. We present our preliminary results on the photoevaporation of circumstellar disks in Cyg OB2 induced by the UV radiation emitted by OB stars.

Guarcello , Mario Giuseppe;Drake, Jeremy J.;Wright, Nicholas J.;Drew, Janet E.;Garcia-Alvarez, D.;Gutermuth, R. A.;Hora, J. L.;Kashyap, V.;King, Robert R.;Naylor, Tim
The Labyrinth of Star Formation, Astrophysics and Space Science Proceedings, Volume 36. ISBN 978-3-319-03040-1. Springer International Publishing Switzerland, 2014, p. 89
n/a 2014
6. The Dynamics of an Expanding OB Association ADS CITATION
Abstract

We present 3-dimensional kinematical observations of the massive OB association Cygnus OB2 to identify the mechanisms responsible for disrupting young star clusters. The picture revealed by these observations is of a highly-substructured, dynamically unmixed OB association that does not exhibit the position-velocity correlations predicted by the theories of infant mortality or tidal stripping. These observations would appear to support a picture of hierarchical star formation.

Wright, Nicholas J.;Bouy, Herve;Drake, Jeremy J.;Drew, Janet E.;Guarcello , Mario;Barrado y Navacués, David
The Labyrinth of Star Formation, Astrophysics and Space Science Proceedings, Volume 36. ISBN 978-3-319-03040-1. Springer International Publishing Switzerland, 2014, p. 465
n/a 2014

2013

1. Externally Induced Disks Photoevaporation in the Massive Cluster Cygnus OB2 ADS
Abstract

CygnusOB2, the most massive OB association of the Cygnus-X region, hosts more than 2000 OB stars and a population of young pre-Main Sequence stars. It is 1.4kpc distant from the Sun and the best target to study star formation and disk evolution in the presence of a large number of massive stars. We present a multiwavelength study of protoplanetary disks in Cyg OB2, based on new deep optical and X-ray data obtained with OSIRIS@GTC and Chandra/ACIS-I (the Cygnus OB2 Chandra Legacy Survey), and on archival data from 2MASS, UKIDSS, IPHAS and the Spitzer Legacy Survey of the Cygnus-X Region. We compare the spatial variation of disk fraction with the intensity of the ionized flux emitted by the OB members of CygOB2. We show that the disk fraction decreases gradually with increasing the intensity of the ionizing flux. The results suggests protoplanetary disks in Cyg OB2 suffer long-range photoevaporation induced by the OB star population. This is different than the results obtained in the study of NGC6611 (i.e. Guarcello et al 2007), NGC2264 (i.e. Balog et al. 2007), and the Trapezium in Orion (i.e. Storzer & Hollenbach 1999), where disk fraction drops only in the proximity of the OB stars. We discuss this difference in terms of the larger ionizing flux and older age in Cyg OB2 with respect to these other clusters and touch upon the relevance of this work for planet formation in the universe.

Guarcello, Mario
Protostars and Planets VI, Heidelberg, July 15-20, 2013. Poster #2S037
Jul 2013
2. OSIRIS deep Imaging of Cygnus OB2: the stellar population of the Cygnus X central engine ADS CITATION
Abstract

The young massive cluster Cyg OB2 is the closest massive star forming region to the Sun, with hundreds of OB members, and then the best target in the Milky Way to study the feedback of massive stars on the star formation process. To study in detail the stellar population of such a unique target, Cyg OB2 has been observed with GTC/OSIRIS and Chandra/ACIS-I. We present the OSIRIS observations, the catalog and the preliminary scientific results.

Guarcello , M. G.;Drake, J. J.;Wright, N. J.;García-Álvarez, D.;Drew, J. E.;Aldcroft, T.;Fruscione, A.;Kashyap, V. L.
Fourth Science Meeting with the GTC (Eds. C. Muñoz-Tuñón & J. M. Rodríguez-Espinosa) Revista Mexicana de Astronomía y Astrofísica (Serie de Conferencias) Vol. 42, pp. 5-7 (2013) (http://www.astroscu.unam.mx/~rmaa/)
May 2013
3. The Disk-bearing Population in the Massive Stars Forming Region Cygnus OB2 ADS
Abstract

Cygnus OB2 is the closest massive star forming region hosting thousand OB stars to the Sun (1450 pc). It represents the best target to study how OB stars affect the star formation process, protoplanetary disk evolution and the evolution of the parent molecular cloud its surroundings. We obtained deep optical observations in r’, i’, and z’ bands with the 10.4m Gran Telescopio Canarias OSIRIS camera, and performed an X-ray survey covering about 1 square degree with Chandra’s ACIS-I (the 1.08 Msec Chandra Cyg OB2 Legacy Survey). These observations, combined with existing deep infrared and optical data of this region (from IPHAS, SDSS DR8, 2MASS/PSC, UKIDSS/GPS, and the ”The Spitzer Legacy Survey of the Cygnus-X Region”) allow us to select the cluster members down to sub-solar masses, and to analyze in detail the different effects that the radiation from OB stars have on the surrounding young stellar population, including triggering of star formation, externally induced disk photoevaporation, and dissipation of protostellar cores. In this contribution, we present the first results obtained from our combined survey: the selection of disk-bearing cluster members, the study of their evolutionary status and of the morphology of the association.

Guarcello , Mario G.;Drake, J. J.;Wright, N. J.;Drew, J.;Garcia-Alvarez, D.;Gutermuth, R. A.;Hora, J. L.;Kashyap, V.;King, R.;Naylor, T.
American Astronomical Society, AAS Meeting #221, id.251.20
Jan 2013

2012

1. VizieR Online Data Catalog: riz photometry in Cyg OB2 (Guarcello+, 2012) ADS
Abstract

The observations were performed in the r’, i’, and z’ filters with OSIRIS, mounted on the 10.4m Gran Telescopio CANARIAS (GTC) of the Spanish Observatorio del Roque de los Muchachos in La Palma, between 2009-09-11 and 2009-09-22. The scale on the detector is 0.127arcsec/pix (1 data file).

Guarcello , M. G.;Wright, N. J.;Drake, J. J.;Garcia-Alvarez, D.;Drew, J. E.;Aldcroft, T.;Kashyap, V. L.
VizieR On-line Data Catalog: J/ApJS/202/19. Originally published in: 2012ApJS..202...19G
Nov 2012
2. The Dynamics of an Expanding OB Association ADS CITATION
Abstract

We present 3-dimensional kinematical observations of the massive OB association Cygnus OB2 to identify the mechanisms responsible for disrupting young star clusters. The picture revealed by these observations is of a highly-substructured, dynamically unmixed OB association that does not exhibit the position-velocity correlations predicted by the theories of infant mortality or tidal stripping. These observations would appear to support a picture of hierarchical star formation.

Wright, Nicholas J.;Bouy, Herve;Drake, Jeremy J.;Drew, Janet E.;Guarcello , Mario;Navacues, David Barrado y
eprint arXiv:1208.0211
Aug 2012
3. The Gaia-ESO Public Spectroscopic Survey ADS CITATION
Abstract

The Gaia-ESO Public Spectroscopic Survey has begun and will obtain high quality spectroscopy of some 100000 Milky Way stars, in the field and in open clusters, down to magnitude 19, systematically covering all the major components of the Milky Way. This survey will provide the first homogeneous overview of the distributions of kinematics and chemical element abundances in the Galaxy. The motivation, organisation and implementation of the Gaia-ESO Survey are described, emphasising the complementarity with the ESA Gaia mission. Spectra from the very first observing run of the survey are presented.

Gilmore, G.;Randich, S.;Asplund, M.;Binney, J.;Bonifacio, P.;Drew, J.;Feltzing, S.;Ferguson, A.;Jeffries, R.;Micela, G.;Negueruela, I.;Prusti, T.;Rix, H.-W.;Vallenari, A.;Alfaro, E.;Allende-Prieto, C.;Babusiaux, C.;Bensby, T.;Blomme, R.;Bragaglia, A.;Flaccomio, E.;François, P.;Irwin, M.;Koposov, S.;Korn, A.;Lanzafame, A.;Pancino, E.;Paunzen, E.;Recio-Blanco, A.;Sacco, G.;Smiljanic, R.;Van Eck, S.;Walton, N.;Aden, D.;Aerts, C.;Affer, L.;Alcala, J.-M.;Altavilla, G.;Alves, J.;Antoja, T.;Arenou, F.;Argiroffi, C.;Asensio Ramos, A.;Bailer-Jones, C.;Balaguer-Nunez, L.;Bayo, A.;Barbuy, B.;Barisevicius, G.;Barrado y Navascues, D.;Battistini, C.;Bellas Velidis, I.;Bellazzini, M.;Belokurov, V.;Bergemann, M.;Bertelli, G.;Biazzo, K.;Bienayme, O.;Bland-Hawthorn, J.;Boeche, C.;Bonito, S.;Boudreault, S.;Bouvier, J.;Brandao, I.;Brown, A.;de Bruijne, J.;Burleigh, M.;Caballero, J.;Caffau, E.;Calura, F.;Capuzzo-Dolcetta, R.;Caramazza, M.;Carraro, G.;Casagrande, L.;Casewell, S.;Chapman, S.;Chiappini, C.;Chorniy, Y.;Christlieb, N.;Cignoni, M.;Cocozza, G.;Colless, M.;Collet, R.;Collins, M.;Correnti, M.;Covino, E.;Crnojevic, D.;Cropper, M.;Cunha, M.;Damiani, F.;David, M.;Delgado, A.;Duffau, S.;Edvardsson, B.;Eldridge, J.;Enke, H.;Eriksson, K.;Evans, N. W.;Eyer, L.;Famaey, B.;Fellhauer, M.;Ferreras, I.;Figueras, F.;Fiorentino, G.;Flynn, C.;Folha, D.;Franciosini, E.;Frasca, A.;Freeman, K.;Fremat, Y.;Friel, E.;Gaensicke, B.;Gameiro, J.;Garzon, F.;Geier, S.;Geisler, D.;Gerhard, O.;Gibson, B.;Gomboc, A.;Gomez, A.;Gonzalez-Fernandez, C.;Gonzalez Hernandez, J.;Gosset, E.;Grebel, E.;Greimel, R.;Groenewegen, M.;Grundahl, F.;Guarcello , M.;Gustafsson, B.;Hadrava, P.;Hatzidimitriou, D.;Hambly, N.;Hammersley, P.;Hansen, C.;Haywood, M.;Heber, U.;Heiter, U.;Held, E.;Helmi, A.;Hensler, G.;Herrero, A.;Hill, V.;Hodgkin, S.;Huelamo, N.;Huxor, A.;Ibata, R.;Jackson, R.;de Jong, R.;Jonker, P.;Jordan, S.;Jordi, C.;Jorissen, A.;Katz, D.;Kawata, D.;Keller, S.;Kharchenko, N.;Klement, R.;Klutsch, A.;Knude, J.;Koch, A.;Kochukhov, O.;Kontizas, M.;Koubsky, P.;Lallement, R.;de Laverny, P.;van Leeuwen, F.;Lemasle, B.;Lewis, G.;Lind, K.;Lindstrom, H. P. E.;Lobel, A.;Lopez Santiago, J.;Lucas, P.;Ludwig, H.;Lueftinger, T.;Magrini, L.;Maiz Apellaniz, J.;Maldonado, J.;Marconi, G.;Marino, A.;Martayan, C.;Martinez-Valpuesta, I.;Matijevic, G.;McMahon, R.;Messina, S.;Meyer, M.;Miglio, A.;Mikolaitis, S.;Minchev, I.;Minniti, D.;Moitinho, A.;Momany, Y.;Monaco, L.;Montalto, M.;Monteiro, M. J.;Monier, R.;Montes, D.;Mora, A.;Moraux, E.;Morel, T.;Mowlavi, N.;Mucciarelli, A.;Munari, U.;Napiwotzki, R.;Nardetto, N.;Naylor, T.;Naze, Y.;Nelemans, G.;Okamoto, S.;Ortolani, S.;Pace, G.;Palla, F.;Palous, J.;Parker, R.;Penarrubia, J.;Pillitteri, I.;Piotto, G.;Posbic, H.;Prisinzano, L.;Puzeras, E.;Quirrenbach, A.;Ragaini, S.;Read, J.;Read, M.;Reyle, C.;De Ridder, J.;Robichon, N.;Robin, A.;Roeser, S.;Romano, D.;Royer, F.;Ruchti, G.;Ruzicka, A.;Ryan, S.;Ryde, N.;Santos, N.;Sanz Forcada, J.;Sarro Baro, L. M.;Sbordone, L.;Schilbach, E.;Schmeja, S.;Schnurr, O.;Schoenrich, R.;Scholz, R.-D.;Seabroke, G.;Sharma, S.;De Silva, G.;Smith, M.;Solano, E.;Sordo, R.;Soubiran, C.;Sousa, S.;Spagna, A.;Steffen, M.;Steinmetz, M.;Stelzer, B.;Stempels, E.;Tabernero, H.;Tautvaisiene, G.;Thevenin, F.;Torra, J.;Tosi, M.;Tolstoy, E.;Turon, C.;Walker, M.;Wambsganss, J.;Worley, C.;Venn, K.;Vink, J.;Wyse, R.;Zaggia, S.;Zeilinger, W.;Zoccali, M.;Zorec, J.;Zucker, D.;Zwitter, T.;Gaia-ESO Survey Team
The Messenger, vol. 147, p. 25-31
Mar 2012
4. Discovery of 15 Myr Old pre-Main Sequence Stars with Active Accretion and Sizeable Discs in NGC 6611 ADS
Abstract

Attention is given to a population of 110 stars with prominent near-infrared (NIR) excess in the NGC 6611 cluster of the Eagle Nebula that have optical colours typical of pre-main sequence (PMS) stars older than 10 Myr. In principle, their V-I colours would be consistent with those of young PMS objects (< 1 Myr), whose radiation is heavily obscured by a circumstellar disc seen at high inclination and in small part scattered towards the observer by the back side of the disc. However, using theoretical models it is shown here that objects of this type can only account for a few percent of this population. In fact, the spatial distribution of these objects, their X-ray luminosities, their optical brightness and their positions in the colour-magnitude diagram unambiguously indicate that most of these stars are intrinsically older than 10 Myr. Ages range from 8 to 30 Myr with a median value of 15 Myr. This is the largest homogeneous sample to date of Galactic PMS stars considerably older than 10 Myr that are still actively accreting from a circumstellar disc and it allows us to set a lower limit of 5% to the disc frequency at 15 Myr in NGC 6611. These values imply a characteristic exponential lifetime of 5 Myr for disc dissipation.

De Marchi, Guido;Panagia, N.;Guarcello , M. G.;Bonito, R.
American Astronomical Society, AAS Meeting #219, id.337.06
Jan 2012

2011

1. Chandra/ACIS-I study of the young stellar population of the Eagle Nebula
Abstract

Not Available

Guarcello , Mario;Caramazza, Marilena;Drake, Jeremy;Micela, Giuseppina;Sciortino, Salvatore
"The X-ray Universe 2011, Presentations of the Conference held in Berlin, Germany, 27-30 June 2011. Available online at: http://xmm.esac.esa.int/external/xmm_science/workshops/2011symposium/, article id.219"
Aug 2011
2. Cluster members and disk fraction of CygnusOB2
Abstract

Not Available

Guarcello , Mario;Drake, Jeremy;Wright, Nicholas
"The X-ray Universe 2011, Presentations of the Conference held in Berlin, Germany, 27-30 June 2011. Available online at: http://xmm.esac.esa.int/external/xmm_science/workshops/2011symposium/, article id.218"
Aug 2011
3. The Chandra Cygnus OB2 Legacy Survey
Abstract

Not Available

Wright, Nicholas;Drake, Jeremy;Guarcello , Mario;Aldcroft, Tom;Kashyap, Vinay;Fruscione, Antonella;Damiani, Francesco;Flaccomio, Ettore;van der Veen, Erik
"The X-ray Universe 2011, Presentations of the Conference held in Berlin, Germany, 27-30 June 2011. Available online at: http://xmm.esac.esa.int/external/xmm_science/workshops/2011symposium/, article id.170"
Aug 2011
4. Observations and theory on the externally induced photoevaporation of circumstellar disk ADS
Abstract

Class II Pre-Main Sequence stars are characterized by the presence of the circumstellar disk in the equatorial plane, which is the site of the planets formation. The induced photoevaporation of disks is one of the key processes leading the evolution of these structures. Photoevaporation occurs when the disk is irradiated by UV and X-ray radiation: Far UltraViolet (FUV) photons (with energy ranging from 6eV to 13.6eV) dissociate H2 molecules, while Extreme UltraViolet (EUV, from 13.6eV to 100eV ) and X-ray photons ionize gas atoms. Since both processes heat the gas up to 1000K-10000K, the thermal pressure drives a photoevaporative flow of gas away from the disk. Photoevaporation is usually induced by the central star itself; however, direct images (taken with the Hubble Space Telescope) of the young stars surrounded by photoevaporating disks in the Orion Nebula Cluster showed that photoevaporation can be induced by the energetic radiation emitted by nearby massive stars. In these cases, the externally induced photoevaporation can dissipate the disks in short timescale (even smaller than 1 Myear in the more extreme situations). Besides, recent studies of the massive young clusters NGC2244 and NGC6611 confirmed that the evolution of circumstellar disks is affected by induced photoevaporation in the core of such massive clusters, but there is still some controversy about these results. In this talk I will review the main features of the photoevaporation process, its effects on disks evolution when it is induced by nearby ionizing sources, and the supporting observational evidences.

Guarcello, Mario G.
American Astronomical Society, AAS Meeting #218, id.312.02; Bulletin of the American Astronomical Society, Vol. 43, 2011
May 2011

2010

1. VizieR Online Data Catalog: NGC 1893 optical and NIR photometry (Prisinzano+, 2011) ADS
Abstract

We present new optical and NIR photometric data in the VRIJHK and H-α bands for the cluster NGC 1893. The optical photometry was obtained by using images acquired in service mode using two different telescopes: the Device Optimized for the LOw RESolution (DOLORES) mounted on the Telescopio Nazionale Galileo (TNG), used in service mode during three nights in 2007, and the Calar Alto Faint Object Spectrograph (CAFOS), mounted on the 2.2m telescope in Calar Alto German-Spanish Observatory (Spain), during three nights in 2007 and 2008. NIR observations were acquired in service mode at the TNG, using the large field Near Infrared Camera Spectrometer (NICS) with the Js(1.25um), H(1.63um) and K'(2.12um) filters during eight nights in 2007 and 2008. We observed a field around NGC 1893 with a raster of 4×4 pointings, at each pointing we obtained a series of NINT dithered exposures. Each exposure is a repetition of a DIT (Detector Integration Time) times NDIT (number of DIT), to avoid saturation of the background. (4 data files).

Prisinzano, L.;Sanz-Forcada, J.;Micela, G.;Caramazza, M.;Guarcello , M. G.;Sciortino, S.;Testi, L.
VizieR On-line Data Catalog: J/A+A/527/A77. Originally published in: 2011A&A...527A..77P
Oct 2010
2. VizieR Online Data Catalog: Stars associated to Eagle Nebula (M16=NGC6611) (Guarcello+ 2010) ADS
Abstract

This catalog contains coordinates and both optical and infrared photometry, plus usefull tags, of the candidate stars associated to the Eagle Nebula (M16), bost disk-less and disk-bearing, selected in Guarcello et al. 2010: “Chronology of star formation and disks evolution in the Eagle Nebula”. The optical photometry in BVI bands comes from observations with WFI@ESO (Guarcello et al. 2007, Cat. J/A+A/462/245); JHK photometry have been obtained from 2MASS/PSC (Bonatto et al. 2006A&A…445..567B, Guarcello et al. 2007, Cat. J/A+A/462/245) and UKIDSS/GPS catalogs (Guarcello et al., 2010, in prep.) ; IRAC data are from GLIMPSE public survey (Indebetouw 2007ApJ…666..321I, Guarcello et al., 2009, Cat. J/A+A/496/453); X-ray data from three observations with Chandra/ACIS-I (Linsky et al., 2007, Cat. J/ApJ/654/347, Guarcello et al., 2007, J/A+A/462/245, Guarcello et al. 2010, in prep.). (1 data file).

Guarcello , M. G.;Micela, G.;Peres, G.;Prisinzano, L.;Sciortino, S.
VizieR On-line Data Catalog: J/A+A/521/A61. Originally published in: 2010A&A...521A..61G
Aug 2010
3. VizieR Online Data Catalog: Blue stars with disk photometry in NGC 6611 (Guarcello+, 2010) ADS
Abstract

This catalog contains coordinates and both optical and infrared photometry, plus usefull tags, of the Blue Stars With Disk (BWE stars) discussed in detail in Guarcello et al. (2010, in prep): “Pre-main sequence stars with disks in the Eagle nebula observed in scattered light”. The optical photometry in BVI bands comes from observations with WFI@ESO (Guarcello et al. 2007, Cat. J/A+A/462/245); JHK photometry have been obtained from 2MASS/PSC and UKIDSS/GPS catalogs (Bonatto et al., 2006A&A…445..567B, Guarcello et al., 2007, Cat. J/A+A/462/245 and 2010, in prep); IRAC data are from GLIMPSE public survey (Indebetouw 2007ApJ…666..321I, Guarcello et al., 2009, Cat. J/A+A/496/453); X-ray data from observations with Chandra/ACIS-I (Linsky et al. 2007, Cat. J/ApJ/654/347, Guarcello et al., 2007, Cat. J/A+A/462/245, Guarcello et al., 2010, in prep). BWE stars have been studied by analizing their Spectral Energy Distribution (SED) using the grid of YSO models developed by Robitaille et al. 2006ApJS..167..256R. (1 data file).

Guarcello , M. G.;Damiani, F.;Micela, G.;Peres, G.;Prisinzano, L.;Sciortino, S.
VizieR On-line Data Catalog: J/A+A/521/A18. Originally published in: 2010A&A...521A..18G
Jun 2010

2009

1. VizieR Online Data Catalog: Photometry of candidate members of NGC6611 (Guarcello+, 2009) ADS
Abstract

Optical BVI photometry have been obtained from 2.2m WFI@ESO observations; JHK data are from 2MASS Point Sources Catalog; IRAC data are from GLIMPSE catalog. X-ray data have been obtained from a CHANDRA/ACIS-I observation of a field o f 17’x17′ centered on the cluster. (1 data file).

Guarcello , M. G.;Micela, G.;Damiani, F.;Peres, G.;Prisinzano, L.;Sciortino, S.
VizieR On-line Data Catalog: J/A+A/496/453. Originally published in: 2009A&A...496..453G
Mar 2009

2007

1. VizieR Online Data Catalog: BVI photometry in NGC 6611 (Guarcello+, 2007) ADS
Abstract

The optical data have been taken in the BVI bands with the Wield Field Camera (WFI), mounted on the 2.2m telescope of the European Southern Observatory (ESO) in La Silla (Chile). The optical images used in this work were taken on 29 July 2000. (1 data file).

Guarcello , M. G.;Prisinzano, L.;Micela, G.;Damiani, F.;Peres, G.;Sciortino, S.
VizieR On-line Data Catalog: J/A+A/462/245. Originally published in: 2007A&A...462..245G
Sep 2007

Proceedings and Other Publications

• Wright, N. J.; Bouy, H.; Drake, J. J.; Drew, J. E.; Guarcello, M. G.; Navacues, D. B., 2012, “The Dynamics of an Expanding OB Association”, ArXiv, 208, 0211. link
• Gilmore, G.; Randich, S.; Asplund, M.; Binney, J.; Bonifacio, P.; Drew, J.; Feltzing, S.; Ferguson, A.; Jeffries, R.; Micela, G.; and 265 coauthors, 2012, “The Gaia-ESO Public Spectroscopic Survey”, The Messanger Vol. 1, 147, 25G. link
• Guarcello, M. G.; Drake, J. J.; Wright, N. J.; Garcia-Alvarez, D.; Drew, J. E.; Aldcroft, T.; Fruscione, A.; Kashyap, V. L., 2013, “OSIRIS deep Imaging of Cygnus OB2: the stellar population of the Cygnus X central engine”, RMxAC, 52, 5G. link
• Guarcello, M. G.; Drake, J. J.; Wright, N. J.; Drew, J. E.; Garcia-Alvarez, D.; Gutermuth, R. A.; Hora, J. L.; Kashyap, V.; King, R. R.; Naylor, T., 2014, “Disk Survival in the Extremely Massive Association Cygnus OB2”, ASSP, 36, 89G. link
• Guarcello, M. G.; Chapter: “Ammassi Stellari” (Star Clusters) of the book: “Voci e domande dell’Astrofisica” (Voices and questions of Astrophysics)