Examinando por Autor "Pepe, F. A."

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Acceso Abierto
Characterization of the K2-38 planetary system Unraveling one of the densest planets known to date
(EDP Sciences, 2020-09-14) Toledo Padrón, B.; Lovis, C.; Suárez Mascareño, A.; Barros, S. C. C.; Sozzetti, A.; Bouchy, F.; Zapatero Osorio, M. R.; Rebolo, R.; Cristiani, S.; Pepe, F. A.; Santos, N. C.; Sousa, S. G.; Tabernero, H. M.; Lillo Box, J.; Bossini, D.; Adibekyan, V.; Allart, R.; Damasso, M.; D´Odorico, V.; Figueira, P.; Lavie, B.; Lo Curto, G.; Mehner, A.; Micela, G.; Modigliani, A.; Nunes, N. J.; Pallé, E.; Abreu, M.; Affolter, M.; Alibert, Y.; Aliverti, M.; Allende Prieto, C.; Alves, D.; Amate, M.; Ávila, G.; Baldini, V.; Bandy, T.; Benatti, S.; Benz, W.; Bianco, A.; Broeg, C.; Cabral, A.; Calderone, G.; Cirami, R.; Coelho, J.; Conconi, P.; Coretti, I.; Cumani, C.; Cupani, G.; Deiries, S.; Dekker, H.; Delabre, B.; Demangeon, O. D.; Di Marcoantonio, P.; Ehrenreich, D.; Fragoso, A.; Genolet, L.; Genoni, M.; Génova Santos, R.; Hughes, I.; Iwert, O.; Knudstrup, J.; Landoni, M.; Lizon, J. L.; Maire, C.; Manescau, A.; Martins, C. J. A. P.; Mégevand, D.; Molaro, P.; Monteiro, M. J. P. F. G.; Monteiro, M. A.; Moschetti, M.; Mueller, E.; Oggioni, L.; Oliveira, A.; Rivas, M.; Santana Tschudi, S.; Santin, P.; Santos, P.; Segovia, A.; Sosnowska, D.; Spanò, P.; Tenegi, F.; Udry, S.; Zanutta, A.; Zerbi, Filippo M.; González Hernández, Carmen; Fundacion La Caixa; Swiss National Science Foundation (SNSF); European Research Council (ERC); Fundacao para a Ciencia e a Tecnologia (FCT); Ministerio de Ciencia e Innovación (MICINN); 0000-0001-8160-5076; 0000-0003-0987-1593; 0000-0001-5664-2852; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. An accurate characterization of the known exoplanet population is key to understanding the origin and evolution of planetary systems. Determining true planetary masses through the radial velocity (RV) method is expected to experience a great improvement thanks to the availability of ultra-stable echelle spectrographs. Aims. We took advantage of the extreme precision of the new-generation echelle spectrograph ESPRESSO to characterize the transiting planetary system orbiting the G2V star K2-38 located at 194 pc from the Sun with V similar to 11.4. This system is particularly interesting because it could contain the densest planet detected to date. Methods. We carried out a photometric analysis of the available K2 photometric light curve of this star to measure the radius of its two known planets, K2-38b and K2-38c, with P-b = 4.01593 +/- 0.00050 d and P-c = 10.56103 +/- 0.00090 d, respectively. Using 43 ESPRESSO high-precision RV measurements taken over the course of 8 months along with the 14 previously published HIRES RV measurements, we modeled the orbits of the two planets through a Markov chain Monte Carlo analysis, significantly improving their mass measurements. Results. Using ESPRESSO spectra, we derived the stellar parameters, T-eff = 5731 +/- 66, log g = 4.38 +/- 0.11 dex, and [Fe/H] = 0 :26 +/- 0.05 dex, and thus the mass and radius of K2-38, M-star = 1.03(-0.02)(+0.04) M-circle plus and R-circle plus = 1.06+0:09 0:06 R-circle plus. We determine new values for the planetary properties of both planets. We characterize K2-38b as a super-Earth with R-P = 1.54 +/- 0.14 R-circle plus and M-p = 7.3(-1.0)(+1:1) M-circle plus, and K2-38c as a sub-Neptune with RP = 2.29 +/- 0.26 R-circle plus and M-p = 8.3(-1.3)(+1:3) M (circle plus). Combining the radius and mass measurements, we derived a mean density of rho(p) = 11.0(-2.8)(+4:1) g cm(-3) for K2-38b and rho(p) = 3.8+1:8 1:1 g cm(-3) for K2-38c, confirming K2-38b as one of the densest planets known to date. Conclusions. The best description for the composition of K2-38b comes from an iron-rich Mercury-like model, while K2-38c is better described by a rocky-model with H2 envelope. The maximum collision stripping boundary shows how giant impacts could be the cause for the high density of K2-38b. The irradiation received by each planet places them on opposite sides of the radius valley. We find evidence of a long-period signal in the RV time-series whose origin could be linked to a 0.25-3 MJ planet or stellar activity.
Acceso Abierto
ESPRESSO highlights the binary nature of the ultra-metal-poor giant HE 0107−5240.
(EDP Sciences, 2020-01-22) Bonifacio, P.; Molaro, P.; Adibekyan, V.; Aguado, D.; Alibert, Y.; Allende Prieto, C.; Caffau, E.; Cristiani, S.; Cupani, G.; Di Marcoantonio, P.; D´Odorico, V.; Ehrenreich, D.; Figueira, P.; Genova, R.; Lo Curto, G.; Lovis, C.; Martins, C. J. A. P.; Mehner, A.; Micela, G.; Monaco, L.; Nunes, N. J.; Pepe, F. A.; Poretti, E.; Rebolo, R.; Santos, N. C.; Saviane, I.; Sousa, S.; Sozzetti, A.; Suárez Mascareño, A.; Udry, S.; Zapatero Osorio, M. R.; González Hernández, Carmen; Agencia Estatal de Investigación (AEI); Ministerio de Economía y Competitividad (MINECO); Fundacao para a Ciencia e a Tecnologia (FCT); European Research Council (ERC); European Research Council (ERC); Molaro, P. [0000-0002-0571-4163]; Monaco, L. [0000-0002-3148-9836]; Nunes, N. J. [0000-0002-3837-6914]; Suarez Mascareño, A. [0000-0002-3814-5323]; Aguado, D. [0000-0001-5200-3973]; González Hernández, J. I. [0000-0002-0264-7356]; Adibekyan, V. [0000-0002-0601-6199]; Zapatero Osorio, M. R. [0000-0001-5664-2852]; Figueira, P. [0000-0001-8504-283X]; Sozzetti, A. [0000-0002-7504-365X]; Santos, N. [0000-0003-4422-2919]; Cupani, G. [0000-0002-6830-9093]; Martins, C. J. A. P. [0000-0002-4886-9261]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. The vast majority of the known stars of ultra low metallicity ([Fe/H] < −4.5) are known to be enhanced in carbon, and belong to the “low-carbon band” (A(C) = log(C/H)+12 ≤ 7.6). It is generally, although not universally, accepted that this peculiar chemical composition reflects the chemical composition of the gas cloud out of which these stars were formed. The first ultra-metal-poor star discovered, HE 0107−5240, is also enhanced in carbon and belongs to the “low-carbon band”. It has recently been claimed to be a long-period binary, based on radial velocity measurements. It has also been claimed that this binarity may explain its peculiar composition as being due to mass transfer from a former AGB companion. Theoretically, low-mass ratios in binary systems are much more favoured amongst Pop III stars than they are amongst solar-metallicity stars. Any constraint on the mass ratio of a system of such low metallicity would shed light on the star formation mechanisms in this metallicity regime. Aims. We acquired one high precision spectrum with ESPRESSO in order to check the reality of the radial velocity variations. In addition we analysed all the spectra of this star in the ESO archive obtained with UVES to have a set of homogenously measured radial velocities. Methods. The radial velocities were measured using cross correlation against a synthetic spectrum template. Due to the weakness of metallic lines in this star, the signal comes only from the CH molecular lines of the G-band. Results. The measurement obtained in 2018 from an ESPRESSO spectrum demonstrates unambiguously that the radial velocity of HE 0107−5240 has increased from 2001 to 2018. Closer inspection of the measurements based on UVES spectra in the interval 2001–2006 show that there is a 96% probability that the radial velocity correlates with time, hence the radial velocity variations can already be suspected from the UVES spectra alone. Conclusions. We confirm the earlier claims of radial velocity variations in HE 0107−5240. The simplest explanation of such variations is that the star is indeed in a binary system with a long period. The nature of the companion is unconstrained and we consider it is equally probable that it is an unevolved companion or a white dwarf. Continued monitoring of the radial velocities of this star is strongly encouraged.
Acceso Abierto
Fundamental physics with ESPRESSO: Towards an accurate wavelength calibration for a precision test of the fine-structure constant
(EDP Sciences, 2021-02-19) Schmidt, T. M.; Molaro, P.; Murphy, M. T.; Lovis, C.; Cupani, G.; Cristiani, S.; Pepe, F. A.; Rebolo, R.; Santos, N. C.; Abreu, M.; Adibekyan, V.; Alibert, Y.; Aliverti, M.; Allart, R.; Allende Prieto, C.; Alves, D.; Baldini, V.; Broeg, C.; Cabral, A.; Calderone, G.; Cirami, R.; Coelho, J.; Coretti, I.; D´Odorico, V.; Di Marcoantonio, P.; Ehrenreich, D.; Figueira, P.; Genoni, M.; Génova Santos, R.; Kerber, F.; Londoni, M.; Leite, A. C. O.; Louis Lizon, J.; Lo Curto, G.; Manescau, A.; Martins, C. J. A. P.; Mégevand, D.; Mehner, A.; Micela, G.; Modigliani, A.; Monteiro, M.; Monteiro, M. J. P. F. G.; Mueller, E.; Nunes, N. J.; Oggioni, L.; Oliveira, A.; Pariani, G.; Pasquini, L.; Redaelli, E.; Riva, M.; Santos, P.; Sosnowska, D.; Sousa, S. G.; Sozzetti, A.; Suárez Mascareño, A.; Udry, S.; Zapatero Osorio, M. R.; Zerbi, Filippo M.; González Hernández, Carmen; Istituto Nazionale di Astrofisica (INAF); Australian Research Council (ARC); Swiss National Science Foundation (SNSF); Fundacao para a Ciencia e a Tecnologia (FCT); European Research Council (ERC); Schmidt, T. M. [0000-0002-4833-7273]; Molaro, P. [0000-0002-0571-4163]; Murphy, M. T. [0000-0002-7040-5498]; Cristiani, S. [0000-0002-2115-5234]; Pepe, F. A. [0000-0002-9815-773X]; Rebolo, R. [0000-0003-3767-7085]
Observations of metal absorption systems in the spectra of distant quasars allow one to constrain a possible variation of the fine-structure constant throughout the history of the Universe. Such a test poses utmost demands on the wavelength accuracy and previous studies were limited by systematics in the spectrograph wavelength calibration. A substantial advance in the field is therefore expected from the new ultra-stable high-resolution spectrograph ESPRESSO, which was recently installed at the VLT. In preparation of the fundamental physics related part of the ESPRESSO GTO program, we present a thorough assessment of the ESPRESSO wavelength accuracy and identify possible systematics at each of the different steps involved in the wavelength calibration process. Most importantly, we compare the default wavelength solution, which is based on the combination of Thorium-Argon arc lamp spectra and a Fabry-Pérot interferometer, to the fully independent calibration obtained from a laser frequency comb. We find wavelength-dependent discrepancies of up to 24 m s−1. This substantially exceeds the photon noise and highlights the presence of different sources of systematics, which we characterize in detail as part of this study. Nevertheless, our study demonstrates the outstanding accuracy of ESPRESSO with respect to previously used spectrographs and we show that constraints of a relative change of the fine-structure constant at the 10−6 level can be obtained with ESPRESSO without being limited by wavelength calibration systematics.
Acceso Abierto
K2-111: an old system with two planets in near-resonance.
(Oxford Academics: Blackwell Publishing, 2020-10-27) Mortier, A.; Zapatero Osorio, M. R.; Malavolta, L.; Alibert, Y.; Rice, K.; Lillo Box, J.; Vanderburg, A.; Oshagh, M.; Buchhave, L. A.; Adibekyan, V.; Delgado Mena, E.; López Morales, M.; Charbonneau, D.; Sousa, S. G.; Lovis, C.; After, L.; Allende Prieto, C.; Barros, S. C. C.; Benatti, S.; Bonomo, A. S.; Boschin, W.; Bouchy, F.; Cabral, A.; Collier Cameron, A.; Cosentino, R.; Cristiani, S.; Demangeon, O. D. S.; Di Marcantonio, P.; D´Odorico, V.; Dumusque, X.; Ehrenreich, D.; Figueira, P.; Fiorenzano, A. F. M.; Ghedina, A.; Haldemann, J.; Harutyunyan, A.; Haywood, R. D.; Latham, D. W.; Lavie, B.; Lo Curto, G.; Maldonado, J.; Menescau, A.; Martins, C. J. A. P.; Mayor, M.; Mégevand, D.; Mehner, A.; Micela, G.; Molaro, P.; Molinari, E.; Nunes, N. J.; Pepe, F. A.; Pallé, E.; Phillips, D.; Piotto, G.; Pinamonti, M.; Poretti, E.; Rivas, M.; Rebolo, R.; Santos, N. C.; Sasselov, D.; Sozzetti, A.; Suárez Mascareño, A.; Udry, S.; West, R. G.; Watson, C. A.; Wilson, T. G.; González Hernández, Carmen; Science and Technology Facilities Council (STFC); Istituto Nazionale di Astrofisica (INAF); Swiss National Science Foundation (SNSF); Fundação para a Ciência e a Tecnologia (FCT); National Aeronautics and Space Administration (NASA); European Research Council (ERC); 0000-0002-9433-871X; 0000-0002-3814-5323; 0000-0002-0571-4163; 0000-0003-4434-2195; 0000-0003-1605-5666; 0000-0001-7246-5438; 0000-0003-2434-3625; 0000-0003-1231-2389; 0000-0003-1784-1431; 0000-0002-7504-365X; 0000-0002-0601-6199; 0000-0001-8749-1962; 0000-0002-8863-7828; 0000-0003-4422-2919; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
This paper reports on the detailed characterization of the K2-111 planetary system with K2, WASP, and ASAS-SN photometry, as well as high-resolution spectroscopic data from HARPS-N and ESPRESSO. The host, K2-111, is confirmed to be a mildly evolved (log g = 4.17), iron-poor ([Fe/H]=-0.46), but alpha-enhanced ([alpha/Fe]=0.27), chromospherically quiet, very old thick disc G2 star. A global fit, performed by using PyORBIT, shows that the transiting planet, K2-111 b, orbits with a period P-b = 5.3518 +/- 0.0004 d and has a planet radius of 1.82(-0.09)(+0.11) R-circle plus and a mass of 5.29(-0.77)(+0.76) M-circle plus, resulting in a bulk density slightly lower than that of the Earth. The stellar chemical composition and the planet properties are consistent with K2-111 b being a terrestrial planet with an iron core mass fraction lower than the Earth. We announce the existence of a second signal in the radial velocity data that we attribute to a non-transiting planet, K2-111 c, with an orbital period of 15.6785 +/- 0.0064 d, orbiting in near-3:1 mean motion resonance with the transiting planet, and a minimum planet mass of 11.3 +/- 1.1M(circle plus). Both planet signals are independently detected in the HARPS-N and ESPRESSO data when fitted separately. There are potentially more planets in this resonant system, but more well-sampled data are required to confirm their presence and physical parameters.
Acceso Abierto
Six transiting planets and a chain of Laplace resonances in TOI-178
(EDP Sciences, 2021-05-06) Leleu, A.; Alibert, Y.; Hara, N. C.; Hooton, M. J.; Wilson, T. G.; Robutel, P.; Delisle, J. B.; Laskar, J.; Hoyer, S.; Lovis, C.; Bryant, E. M.; Ducrot, E.; Gillen, E.; Alonso, R.; Pepe, F. A.; Correia, A. C. M.; Alves, D.; Cooke, B. F.; Cristiani, S.; Damasso, M.; Simon, A. E.; Angerhausen, D.; Günther, M. N.; Beck, M.; Queloz, D.; Dumusque, X.; Beck, T.; Di Marcoantonio, P.; Ehrenreich, D.; Erikson, A.; Olofsson, G.; Bourrier, V.; Reimers, C.; Futyan, D.; Boué, G.; Fridlund, M.; Gandolfi, D.; García Muñoz, Antonio; Peter, G.; Burleigh, M. R.; Bárczy, T.; Guillon, M.; Goad, M. R.; Cabrera, J.; Chamberlain, S.; Moyaro, M.; Davies, M. B.; Thomas, N.; Isaak, K.; Deleuil, M.; Heng, K.; Jehin, E.; Jenkins, J. S.; Anglada Escudé, G.; Pedersen, P. P.; Figueira, P.; Verrecchia, F.; Lecavelier des Etangs, A.; Fortier, A.; Lam, K.; Lendl, M.; Lillo Box, J.; Sousa, S. G.; García, L. J.; Osborn, Hugh P.; Gill, S.; Maxted, P. F. L.; McCormac, J.; Mehner, A.; Tilbrook, R. H.; Guedel, M.; Nunes, N. J.; Oshagh, M.; Ottensamer, R.; Charnoz, S.; Haldemann, J.; Sebastian, D.; Jordán, A.; Bekkelien, A.; Piotto, G.; Kiss, L.; Persson, C. M.; Polenta, G.; Pollacco, D.; Acton, J. S.; Lo Curto, G.; Brandeker, A.; Rando, N.; Magrin, D.; Ragazzoni, R.; Ratti, F.; Rauer, H.; Barrado, D.; Micela, G.; Molaro, P.; Ribas, I.; Santos, N. C.; Scandariato, G.; Billot, N.; Murray, C. A.; Zapatero Osorio, M. R.; Pagano, I.; Demory, B. O.; Sozzetti, A.; Pallé, E.; Smith, A. M. S.; Steller, M.; Suárez Mascareño, A.; Henderson, B.; Anderson, D. R.; Poretti, E.; Fossati, L.; Triaud, A.; Pozuelos, F. J.; Thompson, S.; Turner, O.; Udry, S.; Corral Van Damme, C.; Raynard, L.; Adibekyan, V.; Rebolo, R.; Vines, J. I.; Walton, N. A.; West, R. G.; Di Persio, G.; Schneider, J.; Delrez, L.; Allart, R.; Allende Prieto, C.; Nascimbeni, V.; Sestovic, M.; Cameron, A. C.; Szabó, G. M.; Kristiansen, M. H.; Barros, S. C. C.; Ségransan, D.; Asquier, J.; Baumjohann, W.; Bayliss, D.; Demangeon, O. D. S.; Van Grootel, V.; Martins, C. J. A. P.; Bonfanti, A.; Venus, H.; Benz, W.; Bonfils, X.; Bouchy, F.; Hogan, A. E.; Wheatley, P. J.; Wolter, D.; Broeg, C.; Buder, M.; Burdanov, A.; Lavie, B.; González Hernández, Carmen; Alvarez, M. [0000-0002-6786-2620]; Carrasco Martínez, J. M. [0000-0002-3029-5853]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Determining the architecture of multi-planetary systems is one of the cornerstones of understanding planet formation and evolution. Resonant systems are especially important as the fragility of their orbital configuration ensures that no significant scattering or collisional event has taken place since the earliest formation phase when the parent protoplanetary disc was still present. In this context, TOI-178 has been the subject of particular attention since the first TESS observations hinted at the possible presence of a near 2:3:3 resonant chain. Here we report the results of observations from CHEOPS, ESPRESSO, NGTS, and SPECULOOS with the aim of deciphering the peculiar orbital architecture of the system. We show that TOI-178 harbours at least six planets in the super-Earth to mini-Neptune regimes, with radii ranging from 1.152−0.070+0.073 to 2.87−0.13+0.14 Earth radii and periods of 1.91, 3.24, 6.56, 9.96, 15.23, and 20.71 days. All planets but the innermost one form a 2:4:6:9:12 chain of Laplace resonances, and the planetary densities show important variations from planet to planet, jumping from 1.02−0.23+0.28 to 0.177−0.061+0.055 times the Earth’s density between planets c and d. Using Bayesian interior structure retrieval models, we show that the amount of gas in the planets does not vary in a monotonous way, contrary to what one would expect from simple formation and evolution models and unlike other known systems in a chain of Laplace resonances. The brightness of TOI-178 (H = 8.76 mag, J = 9.37 mag, V = 11.95 mag) allows for a precise characterisation of its orbital architecture as well as of the physical nature of the six presently known transiting planets it harbours. The peculiar orbital configuration and the diversity in average density among the planets in the system will enable the study of interior planetary structures and atmospheric evolution, providing important clues on the formation of super-Earths and mini-Neptunes.