News
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!
