News
News!
Serena Benatti and Claudia Di Maio, GAPS representatives for 2025
Serena Benatti has been appointed Chair of the GAPS collaboration for 2025. GAPS is the program that brings together most of the researchers in Italian institutions (INAF and some universities) working on exoplanets, with a particular focus on the use of high-resolution spectrographs at the TNG. Additionally, the Junior GAPS group, composed of Early Career Researchers in the collaboration, has elected Claudia Di Maio as its representative on the Board for the year 2025.
News!
Stellar X-RAY-UV Coronal Activity and its impact on planets
S. Colombo, D. Locci, R. Spinelli, A. Petralia, C. Cecchi Pestellini, G. Micela
Chapter in the volume: ‘Handbook of Exoplanet’
Planets spend their entire life within an environment predominantly shaped by the presence of a host star. This star, often characterized by intense energetic radiation and energetic stellar winds, imposes formidable constraints on planetary evolution. As a result, a deep understanding of the star and its interaction with the planet is essential for correctly understanding planetary processes and climate. The field of star-planet interaction is vast and involves various types of physics. This chapter focuses on the domain of high energies, specifically addressing the impact of high-energy radiation on the dynamic processes and chemistry of exoplanets, and the role that atmospheric photoevaporation plays in shaping stellar activity.
New EXOPA paper!
PASTAR: A model for stellar surface from the Sun to active stars
A. Petralia, J. Maldonado, G. Micela
Accepted for publication on A&A
Exoplanet characterization requires an in-depth understanding of the host star, as it represents a source of noise that can influence the exoplanetary parameters derived from the transit depth or atmospheric characterization. In this work, we present PAStar, a model that describes the stellar photosphere in the presence of spots and/or faculae and calculates its spectro-photometry. The model was validated using solar data and compared with another model available in the literature, ensuring the consistency of the results. Accurate description of stellar activity is a crucial step in many astrophysical contexts. The method we have developed provides a versatile tool for describing stellar activity when dominated by the presence of spots and faculae, marking an important advance in the study of interactions between exoplanets and host stars.
Example of an exoplanetary transit described with PAStar. (Left) Comparison of the transit shape in the absence of stellar activity (quiet phot) or in the presence of spots (spot) and faculae (spot+fac). (Center and Right) Surface of the star at two different times of the transit, where the position of the planet is indicated with a white disk and its orbital track with a dashed black line. The spots are shown in dark blue, while the faculae are depicted as bright coronas around the spots.
The new EXOPA 2025 Calendar is now available! Download it by clicking here!
Merry Christmas from EXOPA!
New EXOPA paper!
The GAPS Programme at TNG. LXIII. Photoevaporating puzzle: Exploring the enigmatic nature of TOI-5398 b atmospheric signal
M.C. D’ Arpa, G. Guilluy, G. Mantovan, F. Biassoni, R. Spinelli, D. Sicilia, D. Locci, A. Maggio, A.F. Lanza, A. Petralia, C. Di Maio, S. Benatti, A.S. Bonomo, F. Borsa, L. Cabona, S. Desidera, L. Fossati, G. Micela, L. Malavolta, L. Mancini, G. Scandariato, A. Sozzetti, M. Stangret, L. Affer, F. Amadori, M. Basilicata, A. Bignamini, W. Boschin, A. Ghedina
Accepted for publication on A&A
The recent study characterizing the atmosphere of TOI-5398 b, conducted as part of the GAPS (The Global Architecture of Planetary Systems) program using the high-resolution spectrograph HARPS-N, provides new insights into the atmospheric processes of exoplanets, with a specific focus on photoinduced evaporation. The detection of the Hα lines and the He I triplet, along with the Na I doublet, provides valuable data confirming the theoretical predictions regarding atmospheric escape in exoplanets. Additionally, the study offers a clearer view of the vertical distribution of atmospheric elements, showing that He I and Na I are found in the outer layers of the atmosphere, while Hα is located in a more central region. The novelty of this study lies in confirming these features in a planet similar to a hot Saturn rather than in an ultra-hot Jupiter. Furthermore, the detection of the Na I doublet in a relatively cold atmosphere (947 K) contributes to the understanding of atmospheric compositions in colder exoplanets. The combination of He I and Hα in a single system is rare and strengthens models predicting photoinduced evaporation effects. Moreover, the observed signals suggest the presence of atmospheric winds, which could be responsible for the extension of these elements, even suggesting the possible presence of a comet-like tail in TOI-5398 b. These results will support future efforts aimed at refining atmospheric models and better understanding atmospheric escape mechanisms.
News!
GIULIA PICCININI
On November 1st, Giulia Piccinini started her PhD at the Observatory, focusing on the determination of exoplanet masses using spectroscopic and astrometric techniques. The activity takes place within the scientific development of the Ariel mission, under the supervision of Giusi Micela.
News!
Discovered a new exoplanet orbiting Barnard’s star!!
Read the press release on the ESO website (link) and watch the interview with Serena Benatti, one of the authors of the discovery (link to the video).
New EXOPA paper!
The GAPS Programme at TNG. Atmospheric characterisation of KELT-9 b via single-line analysis: Detection of six H I Balmer lines, Na I, Ca I, Ca II, Fe I, Fe II, Mg I, Ti II, Sc II, and Cr II.
M. C. D’Arpa, A. Saba, F. Borsa, L. Fossati, G. Micela, C. Di Maio, M. Stangret, G. Tripodo, L. Affer, A. S. Bonomo, S. Benatti, M. Brogi, V. Fardella, A. F. Lanza, G. Guilluy, J. Maldonado, G. Mantovan, V. Nascimbeni, L. Pino, G. Scandariato, D. Sicilia, A. Sozzetti, R. Spinelli, G. Andreuzzi, A. Bignamini, R. Claudi, S. Desidera, A. Ghedina, C. Knapic, V. Lorenzi.
Accepted for publication on A&A
Height distribution of detected chemical species expressed in planetary radii (Rp) as a function of atmospheric temperature. The black dashed line represents the model temperature profile accounting for NLTE effects. The full lines representing each species height distribution are shifted with respect to the black dashed line for clarity.
In this work we analysed six primary transits of the ultra-hot Jupiter KELT-9 b obtained with the HARPS-N high-resolution spectrograph in the context of the Global Architecture of Planetary Systems (GAPS2) project, to characterise the atmosphere via single-line analysis. We extracted the transmission spectrum of each individual line by comparing the master out-of-transit spectrum with the in-transit spectra and computing the weighted average of the tomography in the planet reference frame. We corrected for the centre-to-limb variation and the Rossiter-McLaughlin effect by modelling the region of the star disc obscured by the planet during the transit and subtracting it from the master-out spectrum. We detected all six observable lines of the Balmer series within the HARPS-N wavelength range, from Hα to Hζ, with a significance exceeding 5σ. We also focussed on metal species, detecting Na I, Ca I, Ca II, Fe I, Fe II, Mg I, Ti II, Sc II, and Cr II lines. This is the first detection in the atmosphere of an exoplanet of Hε and Hζ lines, as well as of individual lines of Sc II and Cr II. Our detections are supported by a comparison with published synthetic transmission spectra of KELT-9b obtained accounting for non-local thermodynamic equilibrium effects. The results underline the presence of a systematic blueshift due to night-side to day-side winds. The single-line analysis allowed us not only to assess the presence of atomic species in the atmosphere of KELT-9 b, but also to further characterise the local stratification of the atmosphere. Coupling the height distribution of the detected species with the velocity shift retrieved, we acknowledged the height distribution of night-side to day-side winds. Moreover, the study of the rotational broadening of the different species supports the prediction of a tidally locked planet rotating as a rigid body.
New EXOPA paper!
XUV irradiation of young planetary atmospheres. Results from a joint XMM-Newton and HST observation of HIP67522
A. Maggio, I. Pillitteri, C. Argiroffi, D. Locci, S. Benatti, G. Micela.
Accepted for publication on A&A
Ratio of EUV/X fluxes as a function of the surface X flux of stars in a sample that also includes HIP 67522. The bands of different colors indicate the two scaling laws specified in the legend.
In this new work, we analyzed high-resolution spectroscopic observations of a young star with a mass similar to that of the Sun, which hosts two transiting planets. In fact, this is currently the youngest known multi-planetary system. The X-ray and far-ultraviolet observations, conducted almost simultaneously with the scientific satellites XMM-Newton and Hubble Space Telescope, aimed to reconstruct the distribution of hot plasma in the outer atmosphere of this star, particularly to calculate its emission in the extreme ultraviolet (EUV, 100-1216 Angstrom) range, which cannot be directly measured due to the lack of adequate space instrumentation. Reconstructing the entire electromagnetic emission, from the visible band to soft X-rays, is a necessary step for studying the influence of stellar radiation on the atmospheres of exoplanets. The X + EUV radiation, in particular, induces significant photochemical and photoevaporation effects, which are of great current interest for understanding planetary formation and evolution, and ultimately for studying the irradiation conditions that may be present in the early stages of life development on “other worlds” orbiting stars similar to our Sun.
The study also served to verify the predictions of several “scaling laws” proposed in the literature, which should help estimate EUV emission when X-band emission is known, without necessarily relying on direct observations. Our study shows that there are still uncertainties in these scaling laws, warranting further investigation.
New EXOPA paper!
Spot Modeling through Multiband Photometry Analysis of V1298 Tau
A. Biagini, A. Petralia, C. Di Maio, L. Betti, E. Pace, G. Micela.
Accepted for publication on A&A
Left: simulated sunspot on V1298 Tau according to the model presented in Biagini et al. 2024. Right: a real image of the Sun during the period studied, from HMI Crediti: A&A; Biagini et al. 2024.
Stellar activity consists of different phenomena, mainly spots and faculae, and it is one of the main sources of noise in exoplanetary observations because it affects both spectroscopic and photometric observations. If we want to study young active planetary systems we need to model the activity of the host stars in order to remove astrophysical noise from our observational data. We modelled the contribution of stellar spots in photometric observations. Through the use of multiband photometry, we aim to extract the geometric properties of the spots and constrain their temperature. We analyzed multiband photometric observations acquired with the 80 cm Marcon telescope of the Osservatorio Polifunzionale del Chianti of V1298 Tau, assuming that the photometric modulation observed in different bands should be due to cold spots. We constrained the effective temperature of the active regions present on the surface of V1298 Tau, which is composed by the contemporary presence of spots and faculae. We tested our hypothesis on solar data, verifying that we measure the size of the dominant active region and its averaged effective temperature.
Carmen joins the EXOPA group!
CARMEN AYALA LOERA
has won a fellowship titled “Machine Learning Techniques to Study M-Type Stars and Their Planets,” funded by “PRIN 2022 – Know your little neighbours: characterizing low-mass stars and planets in the Solar neighbourhood.” She will work in Palermo for a year under the supervision of Jesus Maldonado.
New EXOPA paper!
The time evolution of the ultraviolet habitable zone
R. Spinelli, F. Borsa, G. Ghirlanda, G. Ghisellini, F. Haardt and F. Rigamonti.
Accepted for publication on MNRAS Letters
Evolution of the UV habitable zone (grey, red, and purple zones for different atmospheric transmissivities in the UV band) and the habitable zone (green zone) for the planetary systems under consideration.
Recent experiments suggest that a minimal dose of ultraviolet radiation may have been crucial for the formation of some fundamental building blocks of life, such as ribonucleic acid (RNA). On the other hand, excessive ultraviolet radiation is detrimental to life as we know it, as it can destroy numerous molecules, including DNA. Based on these premises, it is possible to define a ring-shaped zone around stars where a planet can receive a suitable ultraviolet flux for the formation and presence of life. In a previous paper (The ultraviolet habitable zone of exoplanets, published in MNRAS), we presented an analysis of ultraviolet observations from the Swift telescope of stars hosting potentially habitable planets, which were discovered in the “classical” habitable zone, the ring-shaped zone where a planet can have a temperature that allows for the presence of liquid water on its surface. These observations led us to conclude that potentially habitable planets discovered orbiting around M stars (the most numerous type of stars in the galaxy) are outside the ultraviolet habitable zone, as their stars are currently too weak in the UV band to trigger the formation of some RNA precursors. In this new article, we tested the hypothesis that the formation of these compounds may have occurred during the early evolutionary phases of these stars, which are currently estimated to be over 3 billion years old. To do this, we combined Swift observations with GALEX observations of young star groups, from which we obtained an average temporal evolution of UV luminosity for stars of different masses. We found that for all the stars in the sample, there exists or has existed in the past an intersection between the classical habitable zone and the ultraviolet habitable zone, except for very cold stars (with a temperature less than 2800 K, such as Trappist-1). The level and duration of the intersection are higher for stars with greater temperature (and mass) and for atmospheres that are more transparent to ultraviolet radiation. This study suggests that the conditions for forming some of the fundamental building blocks for life are (or have been) more common in our galaxy than previously thought. Among the stars in the sample, an interesting case is that of Proxima Centauri, the closest star to us: compared to similar M stars, these two habitable zones have intersected for much longer, nearly 3 billion years.
EXOPA at the Sharper Night 2024 [Link]
The EXOPA group will participate in the European Researchers’ Night (Sharper Night) 2024, which will be held on September 27th!
Discover our activity at the link!
4th Workshop of the Italian Scientific Community Involved in the Activities of the Ariel Consortium in Palermo from May 20th to 22nd, 2024 [Link]
New EXOPA paper!
A Reanalysis of the LHS 1140 b atmosphere observed with the Hubble Space Telescope
A. Biagini, G. Cracchiolo, A. Petralia, J. Maldonado, C. Di Maio, G. Micela
Accepted for publication on Monthly Notices of the Royal Astronomical Society (MNRAS)
The super-Earth LHS 1140 b is an interesting target for atmospheric observations since it is close to the habitable zone of its star and falls in the gap of the radius distribution of small exoplanets, in the region thought to correspond to the transition between planets with and without atmospheres. Observations of the primary transit with WFC3 on board of the Hubble Space Telescope (HST) revealed a modulation in the planet transmission spectrum compatible with the presence of water; however this modulation may be also due to stellar activity-related phenomena. Here we present a detailed analysis of the WFC3/HST observations to probe the nature of this modulation and to understand if it can be attributable to the presence of unocculted spots on the stellar surface. Our analysis strongly suggests that LHS1140 is a rather quiet star with subsolar [Fe/H] and enriched in 𝛼 elements. Therefore, we rule out the possibility that the planetary spectrum is affected by the presence of spots and faculae. This analysis shows the importance of a proper modelling of the stellar spectrum when analyzing transit observations. Finally, we modelled the planetary atmosphere of LHS1140 b to retrieve its atmospheric composition. However, the low resolution and the narrow spectral range of HST observations prevented us from definitively determining whether the spectral features are attributable to the presence of water or of other molecules in the planetary atmosphere.
Giusi Micela’s Interview on the Online Newspaper Avvenire!
Giusi Micela and Isabella Pagano (director of the INAF – Astronomical Observatory of Catania) gave an interview to the online newspaper Avvenire titled Astrofisica. “We’re hunting for exoplanets to search for life very far from here.” You can find it here.
Play with Ariel on PlayINAF
How will Ariel work?
Let us discover this with activity in augmented reality, realized with Zapworks, where you can transform your mobile devices – smartphones or tablets – into the Ariel satellite, hunting for exotic atmospheres. This is a digital experiment aimed at understanding the analysis of the atmospheres of planets outside the Solar System. Learn more here.
Giusi Micela receives the “Rose Day” award for STEM.
On Saturday, March 9th, astrophysicist Giusi Micela from INAF in Palermo was awarded the 2024 Rose Day prize in the STEM category, a recognition that this year celebrates women who inspire other women, creating a more inclusive world. The event is organized by the Zonta Palermo Triscele and Zonta Palermo Zyz clubs. Full article here.
Signed Addendum No. 2 to Implementing Agreement No. 2021-5-HH.0 for the “Italian Participation in Phase B2/C/D of the Ariel Mission”
The Ariel satellite with the official logo of the Italian group. Logo credits: L. Leonardi
On February 9th, Addendum No. 2 to Implementing Agreement No. 2021-5-HH.0 for the “Italian Participation in Phase B2/C/D1 of the Ariel Mission” was signed. This is a three-year addendum through which ASI (Italian Space Agency) finances the activities of scientific institutes for the preparation of the Ariel mission. The lead institute is INAF (National Institute for Astrophysics) with scientific manager Giusi Micela, who also coordinates the activities of the partners: the University of Florence, Sapienza University, and the Institute of Photonics and Nanotechnologies of CNR (National Research Council) in Padua. The Ariel mission (the Atmospheric Remote-Sensing Infrared Exoplanet Large-survey) will be dedicated to studying the atmospheres of at least 1000 planets orbiting nearby stars, to determine their chemical composition and physical conditions. Ariel was selected by ESA (European Space Agency) as the M4 mission of the “Cosmic Vision 2015-2025” program for a scheduled launch in 2029. Italy has a particularly important role in Ariel as one of the three leading nations (together with England and France) of the mission, and its participation within the consortium is led by the INAF – Astronomical Observatory of Palermo. Furthermore, Italy has a very significant role in the scientific and technological preparation of the mission, being responsible for the telescope, the Instrument Control Unit, and onboard software, as well as thermal analysis, performance, and coordination of ground segment activities relevant to the consortium.
New EXOPA paper!
Signatures of X-rays dominated chemistry in the spectra of exoplanetary atmospheres
D. Locci, G. Aresu, A. Petralia, G. Micela, A. Maggio, C. Cecchi Pestellini
Accepted for publication on Planetary Science Journal (PSJ) – https://arxiv.org/abs/2402.04688
Transmission spectra of gaseous exoplanets computed by varying the value of the X-rays luminosity: LX = 1026 (green line), 1028 (red line), and 1030 erg s−1 (blue line), with T(X) = 0.3, 0.5, and 1 keV, respectively.
High-energy radiation from stars impacts planetary atmospheres deeply affecting their chemistry, providing departures from chemical equilibrium. While the upper atmospheric layers are dominated by ionizations induced by extreme ultraviolet radiation, deeper into the atmosphere molecular abundances are controlled by a characteristic X-ray-dominated chemistry, mainly driven by an energetic secondary electron cascade. In this work, we aim to identify molecular photochemically induced fingerprints in the transmission spectra of a giant planet atmosphere. We have developed a numerical code capable of synthesizing transmission spectra with arbitrary spectral resolution, exploiting updated infrared photoabsorption cross-sections. Chemical mixing ratios are computed using a photochemical model, tailored to investigate high-energy ionization processes. We find that in case of high levels of stellar activity, synthetic spectra in both low and high resolutions show significant, potentially observable out-of-equilibrium signatures arising mainly from CO, CH4, C2H2, and HCN.
New EXOPA paper!
The enigmatic dance of the HD 189733A system: a quest for accretion
S. Colombo, I. Pillitteri, A. Petralia, S. Orlando, G. Micela.
Accepted on A&A https://arxiv.org/abs/2401.03962
Snapshot displaying the intricate magnetic field topology of the system. The yellow sphere represents the star, while the magnetic field lines, depicted by the gradient of red-to-blue lines, are color-coded based on their respective magnetic field intensities.
Several studies suggest that the emission properties of a star can be affected by its interaction with a nearby planet. However, the actual observability of these effects remains a subject of debate. An example is the HD189733A system, where some characteristics of its emissions have been interpreted as indicative of ongoing interactions between the star and its planet. Other studies attribute these characteristics to the coronal activity of the star. In this work, we investigate whether the observed stellar X-ray flare events, which appear to be in phase with the planetary period in the HD189733A system, could be attributed to the accretion of the planetary wind onto the stellar surface or resulted from an interaction between the planetary and stellar winds. We developed a 3D MHD model that describes the system HD189733A, including the central host star and its hot Jupiter, along with their respective winds. The effects of gravity and the magnetic fields of both star and planet are taken into account. In the cases examined in this study, the accretion scenario is only viable when the stellar and planetary magnetic field strengths are at 5 G and 1 G, respectively. In this case, the Rayleigh-Taylor instabilities (RTIs) lead to the formation of an accretion column connecting star and planet. Once formed the column remains stable for the entire simulation. The accretion column yields an accretion rates of about 1e12 g/s and shows a mean density of about 1e7 cm^-3. In the other cases, the accretion column does not form because the RTI is suppressed by the stronger magnetic field intensities assumed for both the star and the planet. We synthesized the emission resulting from the shocked planetary wind and, its total X-ray emission ranges from 5e23 to 1e24 erg/s. In the case of accretion, the emission originating from the hot spot cannot be distinguished from the coronal activity.
First EXOPA paper of 2024!
THE GAPS PROGRAMME AT TNG LII. SPOT MODELING OF V1298 TAU USING SPOTCCF TOOL
C. Di Maio, A. Petralia, G. Micela, A.F. Lanza, M. Rainer, L. Malavolta, S. Benatti, L. Affer, J. Maldonado, S. Colombo, M. Damasso, A. Maggio, K. Biazzo, A. Bignamini, F. Borsa, W. Boschin, L. Cabona, M. Cecconi, R. Claudi, E. Covino, L. Di Fabrizio, R. Gratton, V. Lorenzi, L. Mancini, S. Messina, E. Molinari, M. Molinaro, D. Nardiello, E. Poretti, A. Sozzetti
Accepted for publication in A&A https://arxiv.org/abs/2312.14269
Esempio di un profilo CCF di V1298 Tau (in blu) modellato tramite SpotCCF assumendo la presenza di due macchie stellari sulla superficie della stella (in arancione). Nel box viene mostrata la configurazione delle macchie ottenute da SpotCCF.
Intrinsic variability due to magnetic activity, typical in young stars, poses a significant challenge in the detection and characterization of exoplanets. Stellar activity can impact photometric measurements and spectroscopic observations, influencing our ability to detect exoplanets. In this study, we present SpotCCF, a method capable of modeling the stellar photosphere and its surface inhomogeneities (stellar spots) in young and active stars exhibiting high rotational velocities. It is based on the cross-correlation function (CCF) technique, allowing the extraction of information about the configuration of spots on the stellar surface. Within the GAPS project, we analyzed over 300 spectra of the star V1298 Tau provided by the high-resolution HARPS-N spectrograph installed at the Galileo National Telescope.
Applying the SpotCCF model, we extracted the spot configuration (latitude, longitude, and projected filling factor) and provided new radial velocity time series. The results of this work demonstrated how deformations in the CCF profiles of the star V1298 Tau are modulated with stellar rotation, supporting the hypothesis that they are caused by the presence of stellar spots. Additionally, it suggested a differential rotation velocity of the star with lower rotation at latitudes near the pole. Our method also allowed for improved radial velocity extraction, yielding a significantly lower dispersion compared to the commonly used TERRA pipeline.
Two new members join the EXOPA group!
ANDREA DAMONTE
won a Vinci doctoral scholarship and started his joint PhD program between the Université de Paris and the University of Palermo. The research theme of his doctoral thesis focuses on studying the effects of stellar flares on planetary atmospheres. Andrea began his work on December 1st in Palermo and will be supervised by Giusi Micela in Palermo and Antonio Garcia Munoz in Paris.
GIULIA PICCININI
has started a research fellowship at the Observatory focused on determining the masses of exoplanets using spectroscopic and astrometric techniques. The work is part of the scientific development of the Ariel mission under the supervision of Giusi Micela.
The new EXOPA Calendar for 2024 is now available! Download it!
