Examinando por Autor "Petralia, A."

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Acceso Abierto
HADES RV Programme with HARPS-N at TNG XIII. A sub-Neptune around the M dwarf GJ 720 A
(EDP Sciences, 2021-05-31) González Álvarez, E.; Petralia, A.; Micela, G.; Maldonado, J.; Affer, L.; Maggio, A.; Covino, E.; Damasso, M.; Lanza, A. F.; Perger, M.; Pinamonti, M.; Poretti, E.; Scandariato, G.; Sozzetti, A.; Bignamini, A.; Giacobbe, P.; Leto, G.; Pagano, I.; Zanmar Sánchez, R.; Rebolo, R.; Ribas, I.; Suárez Mascareño, A.; Toledo Padrón, B.; González Hernández, Carmen; National Science Foundation (USA NSF); Agenzia Spaziale Italiana (ASI); Generalitat de Catalunya; Fundación Caixa; Agencia Estatal de Investigación (AEI); González Álvarez, E. [0000-0002-4820-2053]; Petralia, A. [0000-0002-9882-1020]; Maldonado, J. [0000-0002-2218-5689]; Affer, L. [0000-0001-5600-3778]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. The high number of super-Earth and Earth-like planets in the habitable zone detected around M-dwarf stars in recent years has revealed these stellar objects to be the key to planetary radial velocity (RV) searches. Aims. Using the HARPS-N spectrograph within The HArps-n red Dwarf Exoplanet Survey (HADES) we have reached the precision needed to detect small planets with a few Earth masses using the spectroscopic radial velocity technique. HADES is mainly focused on the M-dwarf population of the northern hemisphere. Methods. We obtained 138 HARPS-N RV measurements between 2013 May and 2020 September of GJ 720 A, classified as an M0.5 V star located at a distance of 15.56 pc. To characterize the stellar variability and to distinguish the periodic variation due to the Keplerian signals from those related to stellar activity, the HARPS-N spectroscopic activity indicators and the simultaneous photometric observations with the APACHE and EXORAP transit surveys were analyzed. We also took advantage of TESS, MEarth, and SuperWASP photometric surveys. The combined analysis of HARPS-N RVs and activity indicators let us address the nature of the periodic signals. The final model and the orbital planetary parameters were obtained by simultaneously fitting the stellar variability and the Keplerian signal using a Gaussian process regression and following a Bayesian criterion. Results. The HARPS-N RV periodic signals around 40 days and 100 days have counterparts at the same frequencies in HARPS-N activity indicators and photometric light curves. We thus attribute these periodicities to stellar activity; the first period is likely associated with the stellar rotation. GJ 720 A shows the most significant signal at 19.466 ± 0.005 days with no counterparts in any stellar activity indices. We hence ascribe this RV signal, having a semi-amplitude of 4.72 ± 0.27 m s−1, to the presence of a sub-Neptune mass planet. The planet GJ 720 Ab has a minimum mass of 13.64 ± 0.79 M⊕, it is in circular orbit at 0.119 ± 0.002 AU from its parent star, and lies inside the inner boundary of the habitable zone around its parent star.
Acceso Abierto
HADES RV programme with HARPS-N at TNG XIV. A candidate super-Earth orbiting the M-dwarf GJ 9689 with a period close to half the stellar rotation period
(EDP Sciences, 2021-07-12) Maldonado, J.; Petralia, A.; Damasso, M.; Pinamonti, M.; Scandariato, G.; González Álvarez, E.; Affer, L.; Micela, G.; Lanza, A. F.; Leto, G.; Poretti, E.; Sozzetti, A.; Perger, M.; Giacobbe, P.; Zanmar Sánchez, R.; Maggio, A.; Rebolo, R.; Ribas, I.; Suárez Mascareño, A.; Toledo Padrón, B.; Bignamini, A.; Molinari, E.; Covino, E.; Claudi, R.; Desidera, S.; Herrero, E.; Morales, J. C.; Pagano, I.; Piotto, G.; González Hernández, Carmen; Agencia Estatal de Investigación (AEI); Generalitat de Catalunya; Maldonado, J. [0000-0002-2218-5689]; Petralia, A. [0000-0002-9882-1020]; Damasso, M. [0000-0001-9984-4278]; Pinamonti, M. [0000-0002-4445-1845]; Affer, L. [0000-0001-5600-3778]; Lanza, A. F. [0000-0001-5928-7251]; Leto, G. [0000-0002-0040-5011]; Poretti, E. [0000-0003-1200-0473]; Sozzetti, A. [0000-0002-7504-365X]; Perger, M. [0000-0001-7098-0372]; Zanmar Sánchez, R. [0000-0002-6997-0887]; Maggio, A. [0000-0001-5154-6108]; González Hernández, J. I. [0000-0002-0264-7356]; Ribas, I. [0000-0002-6689-0312]; Toledo Padrón, B. [0000-0002-8194-215X]; Bignamini, A. [0000-0002-5606-6354]; Molinari, E. [0000-0002-1742-7735]; Covino, E. [0000-0002-7579-2298]; Claudi, R. [0000-0001-7707-5105]; Desidera, S. [0000-0001-8613-2589]
Context. It is now well-established that small, rocky planets are common around low-mass stars. However, the detection of such planets is challenged by the short-term activity of host stars. Aims. The HARPS-N red Dwarf Exoplanet Survey programme is a long-term project at the Telescopio Nazionale Galileo aimed at monitoring nearby, early-type, M dwarfs, using the HARPS-N spectrograph to search for small, rocky planets. Methods. A total of 174 HARPS-N spectroscopic observations of the M0.5V-type star GJ 9689 taken over the past seven years have been analysed. We combined these data with photometric measurements to disentangle signals related to the stellar activity of the star from possible Keplerian signals in the radial velocity data. We ran an MCMC analysis, applying Gaussian process regression techniques to model the signals present in the data. Results. We identify two periodic signals in the radial velocity time series, with periods of 18.27 and 39.31 d. The analysis of the activity indexes, photometric data, and wavelength dependency of the signals reveals that the 39.31 d signal corresponds to the stellar rotation period. On the other hand, the 18.27 d signal shows no relation to any activity proxy or the first harmonic of the rotation period. We, therefore, identify it as a genuine Keplerian signal. The best-fit model describing the newly found planet, GJ 9689 b, corresponds to an orbital period of Pb = 18.27 ± 0.01 d and a minimum mass of MP sini = 9.65 ± 1.41 M⊕.