Examinando por Autor "Alonso, R."

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Acceso Abierto
CHEOPS observations of the HD 108236 planetary system: a fifth planet, improved ephemerides, and planetary radii
(EDP Sciences, 2021-02-19) Bonfanti, A.; Delrez, L.; Hooton, M. J.; Wilson, T. G.; Fossati, L.; Alibert, Y.; Hoyer, S.; Mustill, A. J.; Osborn, H. P.; Adibekyan, V.; Gandolfi, D.; Van Eylen, V.; Viotto, V.; Walter, I.; Walton, N. A.; Wildi, F.; Wolter, D.; Salmon, S.; Sousa, S. G.; Tuson, A.; Van Grootel, V.; Cabrera, J.; Nascimbeni, V.; Maxted, P. F. L.; Barros, S. C. C.; Billot, N.; Bonfils, X.; Borsato, L.; Broeg, C.; Davies, M. B.; Deleuil, M.; Demangeon, O. D. S.; Fridlund, M.; Lacedelli, G.; Lendl, M.; Persson, C.; Santos, N. C.; Scandariato, G.; Szabó, Gy. M.; Collier Cameron, A.; Udry, S.; Benz, W.; Beck, M.; Ehrenreich, D.; Fortier, A.; Isaak, K. G.; Queloz, D.; Alonso, R.; Asquier, J.; Bandy, T.; Bárczy, T.; Barrado, D.; Barragán, O.; Baumjohann, W.; Beck, T.; Bekkelien, A.; Bergomi, M.; Brandeker, A.; Busch, M. D.; Cessa, V.; Charnoz, S.; Chazelas, B.; Van Damme, C. C.; Demory, B. O.; Erikson, A.; Farinato, J.; Futyan, D.; García Muñoz, Antonio; Gillon, M.; Guedel, M.; Guterman, P.; Hasiba, J.; Heng, K.; Hernández, E.; Kiss, L.; Kuntzer, T.; Laskar, J.; Lecavelier des Etangs, A.; Lovis, C.; Magrin, D.; Malvasio, L.; Marafatto, L.; Michaelis, H.; Munari, M.; Olofsson, G.; Ottacher, H.; Ottensamer, R.; Pagano, I.; Pallé, E.; Peter, G.; Piazza, D.; Piotto, G.; Pollacco, D.; Ragazzoni, R.; Rando, N.; Ratti, F.; Rauer, H.; Ribas, I.; Rieder, M.; Rohlfs, R.; Safa, F.; Salatti, M.; Ségransan, D.; Simon, A. E.; Smith, A. M. S.; Sordet, Michael; Steller, M.; Thomas, N.; Tschentscher, M.; Swiss Space Office (SSO); La Silla Observatory; Austrian Research Promotion Agency (FFG); European Research Council (ERC); Swiss National Science Foundation (SNSF); Agencia Estatal de Investigación (AEI); Generalitat de Catalunya; European Space Agency (ESA); Fundacao para a Ciencia e a Tecnologia (FCT); Belgian Federal Science Policy Office (BELSPO); Hungarian National Research, Development and Innovation Office (NKFIH); Istituto Nazionale di Astrofisica (INAF); Swedish National Infrastructure for Computing (SNIC); Bonfanti, A. [0000-0002-1916-5935]; Cameron, A. [0000-0002-8863-7828]; Santos, N. [0000-0003-4422-2919]; Mustill, A. J. [0000-0002-2086-3642]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. The detection of a super-Earth and three mini-Neptunes transiting the bright (V = 9.2 mag) star HD 108236 (also known as TOI-1233) was recently reported on the basis of TESS and ground-based light curves. Aims. We perform a first characterisation of the HD 108236 planetary system through high-precision CHEOPS photometry and improve the transit ephemerides and system parameters. Methods. We characterise the host star through spectroscopic analysis and derive the radius with the infrared flux method. We constrain the stellar mass and age by combining the results obtained from two sets of stellar evolutionary tracks. We analyse the available TESS light curves and one CHEOPS transit light curve for each known planet in the system. Results. We find that HD 108236 is a Sun-like star with R⋆ = 0.877 ± 0.008 R⊙, M⋆ = 0.869−0.048+0.050 M⊙, and an age of 6.7−5.1+4.0 Gyr. We report the serendipitous detection of an additional planet, HD 108236 f, in one of the CHEOPS light curves. For this planet, the combined analysis of the TESS and CHEOPS light curves leads to a tentative orbital period of about 29.5 days. From the light curve analysis, we obtain radii of 1.615 ± 0.051, 2.071 ± 0.052, 2.539−0.065+0.062, 3.083 ± 0.052, and 2.017−0.057+0.052 R⊕ for planets HD 108236 b to HD 108236 f, respectively. These values are in agreement with previous TESS-based estimates, but with an improved precision of about a factor of two. We perform a stability analysis of the system, concluding that the planetary orbits most likely have eccentricities smaller than 0.1. We also employ a planetary atmospheric evolution framework to constrain the masses of the five planets, concluding that HD 108236 b and HD 108236 c should have an Earth-like density, while the outer planets should host a low mean molecular weight envelope. Conclusions. The detection of the fifth planet makes HD 108236 the third system brighter than V = 10 mag to host more than four transiting planets. The longer time span enables us to significantly improve the orbital ephemerides such that the uncertainty on the transit times will be of the order of minutes for the years to come. A comparison of the results obtained from the TESS and CHEOPS light curves indicates that for a V ~ 9 mag solar-like star and a transit signal of ~500 ppm, one CHEOPS transit light curve ensures the same level of photometric precision as eight TESS transits combined, although this conclusion depends on the length and position of the gaps in the light curve.
Acceso Abierto
Detection and characterization of an ultra-dense sub-Neptunian planet orbiting the Sun-like star K2-292★
(EDP Sciences, 2019-03-14) Luque, R.; Nowak, G.; Pallé, E.; Dai, F.; Kaminski, A.; Nagel, E.; Hidalgo, D.; Bauer, F. F.; Lafarga, M.; Livingston, J.; Barragán, O.; Hirano, T.; Fridlund, M.; Gandolfi, D.; Justesen, A. B.; Hjorth, M.; Van Eylen, V.; Winn, J. N.; Esposito, M.; Morales, J. C.; Albrecht, S.; Alonso, R.; Amado, P. J.; Beck, P.; Caballero, J. A.; Cabrera, J.; Cochran, W. D.; Csizmadia, Sz.; Deeg, H.; Eigmuller, Ph.; Endl, M.; Erikson, A.; Fukui, A.; Grziwa, S.; Guenther, E. W.; Hatzes, A. P.; Knudstrup, E.; Korth, J.; Lam, K. W. F.; Lund, M. N.; Mathur, S.; Montañés Rodríguez, P.; Narita, N.; Nespral, D.; Niraula, P.; Pätzold, M.; Persson, C. M.; Prieto Arranz, J.; Quirrenbach, A.; Rauer, H.; Redfield, S.; Reiners, A.; Ribas, I.; Smith, A. M. S.; European Research Council (ERC); Ministerio de Economía y Competitividad (MINECO); Japan Society for the Promotion of Science (JSPS); Danish National Research Foundation (DNRF); Deutsche Forschungsgemeinschaft (DFG); Swedish National Space Agency (SNSA); Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
We present the discovery and characterization of a new transiting planet from Campaign 17 of the Kepler extended mission K2. The planet K2-292 b is a warm sub-Neptune on a 17 day orbit around a bright (V = 9.9 mag) solar-like G3 V star with a mass and radius of M⋆ = 1.00 ± 0.03 M⊙ and R⋆ = 1.09 ± 0.03 R⊙, respectively. We modeled simultaneously the K2 photometry and CARMENES spectroscopic data and derived a radius of Rp=2.63−0.10+0.12 R⊕ and mass of Mp=24.5−4.4+4.4 M⊕, yielding a mean density of ρp=7.4−1.5+1.6 g cm−3, which makes it one of the densest sub-Neptunian planets known to date. We also detected a linear trend in the radial velocities of K2-292 (γ˙RV = −0.40−0.07+0.07 m s−1 d−1) that suggests a long-period companion with a minimum mass on the order of 33 M⊕. If confirmed, it would support a formation scenario of K2-292 b by migration caused by Kozai-Lidov oscillations.
Acceso Abierto
Detection and Doppler monitoring of K2-285 (EPIC 246471491), a system of four transiting planets smaller than Neptune
(EDP Sciences, 2019-03-04) Pallé, E.; Nowak, G.; Luque, R.; Hidalgo, D.; Barragán, O.; Prieto Arranz, J.; Hirano, T.; Fridlund, M.; Gandolfi, D.; Livingston, J.; Dai, F.; Morales, J. C.; Lafarga, M.; Albrecht, S.; Alonso, R.; Amado, P. J.; Caballero, J. A.; Cabrera, J.; Cochran, W. D.; Csizmadia, Sz.; Deeg, H.; Eigmuller, Ph.; Endl, M.; Erikson, A.; Fukui, A.; Guenther, E. W.; Grziwa, S.; Hatzes, A. P.; Korth, J.; Kürster, M.; Kuzuhara, M.; Montañés Rodríguez, P.; Murgas Alcaino, F.; Narita, N.; Nespral, D.; Pätzold, M.; Persson, C. M.; Quirrenbach, A.; Rauer, H.; Redfield, S.; Reiners, A.; Ribas, I.; Smith, A. M. S.; Van Eylen, V.; Winn, J. N.; Zechmeister, M.; Agencia Estatal de Investigación (AEI); Japan Society for the Promotion of Science (JSPS); Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. The Kepler extended mission, also known as K2, has provided the community with a wealth of planetary candidates that orbit stars typically much brighter than the targets of the original mission. These planet candidates are suitable for further spectroscopic follow-up and precise mass determinations, leading ultimately to the construction of empirical mass-radius diagrams. Particularly interesting is to constrain the properties of planets that are between Earth and Neptune in size, the most abundant type of planet orbiting Sun-like stars with periods of less than a few years. Aims. Among many other K2 candidates, we discovered a multi-planetary system around EPIC 246471491, referred to henceforth as K2-285, which contains four planets, ranging in size from twice the size of Earth to nearly the size of Neptune. We aim here at confirming their planetary nature and characterizing the properties of this system. Methods. We measure the mass of the planets of the K2-285 system by means of precise radial-velocity measurements using the CARMENES spectrograph and the HARPS-N spectrograph. Results. With our data we are able to determine the mass of the two inner planets of the system with a precision better than 15%, and place upper limits on the masses of the two outer planets. Conclusions. We find that K2-285b has a mass of Mb = 9.68−1.37+1.21 M⊕ and a radius of Rb = 2.59−0.06+0.06 R⊕, yielding a mean density of ρb = 3.07−0.45+0.45 g cm−3, while K2-285c has a mass of Mc = 15.68−2.13+2.28 M⊕, radius of Rc = 3.53−0.08+0.08 R⊕, and a mean density of ρc = 1.95−0.28+0.32 g cm−3. For K2-285d (Rd = 2.48−0.06+0.06 R⊕) and K2-285e (Re = 1.95−0.05+0.05 R⊕), the upper limits for the masses are 6.5 M⊕ and 10.7 M⊕, respectively. The system is thus composed of an (almost) Neptune-twin planet (in mass and radius), two sub-Neptunes with very different densities and presumably bulk composition, and a fourth planet in the outermost orbit that resides right in the middle of the super-Earth/sub-Neptune radius gap. Future comparative planetology studies of this system would provide useful insights into planetary formation, and also a good test of atmospheric escape and evolution theories.
Acceso Abierto
The hot dayside and asymmetric transit of WASP-189 b seen by CHEOPS
(EDP Sciences, 2020-11-09) Lendl, M.; Csizmadia, Sz.; Deline, A.; Fossati, L.; Kitzmann, D.; Heng, K.; Hoyer, S.; Salmon, S.; Benz, W.; Broeg, C.; Ehrenreich, D.; Malvasio, L.; Marafatto, L.; Michaelis, H.; Munari, M.; Nascimbeni, V.; Olofsson, G.; Ottacher, H.; Ottensamer, R.; Pagano, I.; Pallé, E.; Peter, G.; Pizza, D.; Piotto, G.; Pollacco, D.; Ratti, F.; Rauer, H.; Ragazzoni, R.; Rando, N.; Ribas, I.; Rieder, M.; Rohlfs, R.; Safa, F.; Santos, N. C.; Scandariato, G.; Ségransan, D.; Simón, A. E.; Singh, V.; Smith, A. M. S.; Sordet, Michael; Sousa, S. G.; Steller, M.; Szabó, Gy. M.; Thomas, N.; Tschentscher, M.; Udry, S.; Viotto, V.; Walter, I.; Walton, N. A.; Wildi, F.; Wolter, D.; Fortier, A.; Queloz, D.; Bonfanti, A.; Brandeker, A.; Collier Cameron, A.; Delrez, L.; García Muñoz, Antonio; Hooton, M. J.; Maxted, P. F. L.; Morris, B. M.; Van Grootel, V.; Wilson, T. G.; Alibert, Y.; Alonso, R.; Asquier, J.; Bandy, T.; Bárczy, T.; Barrado, D.; Barros, S. C. C.; Baumjohann, W.; Beck, M.; Beck, T.; Bekkelien, A.; Bergomi, M.; Billot, N.; Biondi, F.; Bonfils, X.; Bourrier, V.; Busch, M. D.; Cabrera, J.; Cessa, V.; Charnoz, S.; Chazelas, B.; Corral Van Damme, C.; Davies, M. B.; Deleuil, M.; Demangeon, O. D. S.; Demory, B. O.; Erikson, A.; Farinato, J.; Fridlund, M.; Futyan, D.; Gandolfi, D.; Gillon, M.; Guterman, P.; Hasiba, J.; Hernández, E.; Isaak, K. G.; Kiss, L.; Kuntzer, T.; Lecavelier des Etangs, A.; Lüftinger, T.; Laskar, J.; Lovis, C.; Magrin, D.; Austrian Research Promotion Agency (FFG); Deutsche Forschungsgemeinschaft (DFG); European Research Council (ERC); Swiss National Science Foundation (SNSF); Agencia Estatal de Investigación (AEI); Fundação para a Ciência e a Tecnologia (FCT); National Research Development and Innovation Office, Hungarian (NKFIH); Agenzia Spaziale Italiana (ASI); Generalitat de Catalunya; European Space Agency (ESA); Fundacao para a Ciencia e a Tecnologia (FCT); Belgian Federal Science Policy Office (BELSPO); Istituto Nazionale di Astrofisica (INAF); Wilson, T. G. [0000-0001-8749-1962]; Cameron, A. [0000-0002-8863-7828]; Fridlund, M. [0000-0002-0855-8426]; Cabrera, J. [0000-0001-6653-5487]; Barros, S. [0000-0003-2434-3625]; Santos, N. [0000-0003-4422-2919]; Piotto, G. [0000-0002-9937-6387]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
The CHEOPS space mission dedicated to exoplanet follow-up was launched in December 2019, equipped with the capacity to perform photometric measurements at the 20 ppm level. As CHEOPS carries out its observations in a broad optical passband, it can provide insights into the reflected light from exoplanets and constrain the short-wavelength thermal emission for the hottest of planets by observing occultations and phase curves. Here, we report the first CHEOPS observation of an occultation, namely, that of the hot Jupiter WASP-189 b, a MP ≈ 2MJ planet orbiting an A-type star. We detected the occultation of WASP-189 b at high significance in individual measurements and derived an occultation depth of dF = 87.9 ± 4.3 ppm based on four occultations. We compared these measurements to model predictions and we find that they are consistent with an unreflective atmosphere heated to a temperature of 3435 ± 27 K, when assuming inefficient heat redistribution. Furthermore, we present two transits of WASP-189 b observed by CHEOPS. These transits have an asymmetric shape that we attribute to gravity darkening of the host star caused by its high rotation rate. We used these measurements to refine the planetary parameters, finding a ~25% deeper transit compared to the discovery paper and updating the radius of WASP-189 b to 1.619 ± 0.021RJ. We further measured the projected orbital obliquity to be λ = 86.4−4.4+2.9°, a value that is in good agreement with a previous measurement from spectroscopic observations, and derived a true obliquity of Ψ = 85.4 ± 4.3°. Finally, we provide reference values for the photometric precision attained by the CHEOPS satellite: for the V = 6.6 mag star, and using a 1-h binning, we obtain a residual RMS between 10 and 17 ppm on the individual light curves, and 5.7 ppm when combining the four visits.
Acceso Abierto
Three planets transiting the evolved star EPIC 249893012: A hot 8.8-M super-Earth and two warm 14.7 and 10.2-M sub-Neptunes
(EDP Sciences, 2020-04-24) Hidalgo, D.; Pallé, E.; Alonso, R.; Gandolfi, D.; Fridlund, M.; Nowak, G.; Luque, R.; Hirano, T.; Justesen, A. B.; Cochran, W. D.; Barragán, O.; Spina, L.; Rodler, F.; Albrecht, S.; Anderson, D.; Amado, P. J.; Bryant, E.; Caballero, J. A.; Cabrera, J.; Csizmadia, Sz.; Dai, F.; De Leon, J.; Deeg, H. J.; Eigmuller, Ph.; Endl, M.; Erikson, A.; Esposito, M.; Figueira, P.; Georgieva, I.; Grziwa, S.; Guenther, E. W.; Hatzes, A. P.; Hjorth, M.; Hoeijmakers, H. J.; Kabath, P.; Korth, J.; Kuzuhara, M.; Lafarga, M.; Lampón, M.; Leao, I. C.; Livingston, J.; Mathur, S.; Montañés Rodríguez, P.; Morales, J. C.; Murgas Alcaino, F.; Nagel, E.; Narita, N.; Nielsen, L. D.; Patzold, M.; Persson, C. M.; Prieto Arranz, J.; Quirrenbach, A.; Rauer, H.; Redfield, S.; Reiners, A.; Ribas, I.; Smith, A. M. S.; Subjak, J.; Van Eylen, V.; Wilson, P. A.; Ministerio de Economía y Competitividad (MINECO); Agencia Estatal de Investigación (AEI); Deutsche Forschungsgemeinschaft (DFG); Japan Science and Technology Agency (JST); Hidalgo, D. [0000-0002-7340-6963]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
We report the discovery of a new planetary system with three transiting planets, one super-Earth and two sub-Neptunes, that orbit EPIC 249893012, a G8 IV-V evolved star ( M ? = 1.05 0.05 M fi, R ? = 1.71 0.04 R fi, Te ff = 5430 85 K). The star is just leaving the main sequence. We combined K2 photometry with IRCS adaptive-optics imaging and HARPS, HARPS-N, and CARMENES highprecision radial velocity measurements to confirm the planetary system, determine the stellar parameters, and measure radii, masses, and densities of the three planets. With an orbital period of 3:5949+0:0007 0:0007 days, a mass of 8:75+1:09 1:08 M , and a radius of 1:95+0:09 0:08 R , the inner planet b is compatible with nickel-iron core and a silicate mantle ( b = 6:39+1:19 1:04 g cm 3). Planets c and d with orbital periods of 15:624+0:001 0:001 and 35:747+0:005 0:005 days, respectively, have masses and radii of 14:67+1;84 1:89 M and 3:67+0:17 0:14 R and 10:18+2:46 2:42 M and 3:94+0:13 0:12 R , respectively, yielding a mean density of 1:62+0:30 0:29 and 0:91+0:25 0:23 g cm 3, respectively. The radius of planet b lies in the transition region between rocky and gaseous planets, but its density is consistent with a rocky composition. Its semimajor axis and the corresponding photoevaporation levels to which the planet has been exposed might explain its measured density today. In contrast, the densities and semimajor axes of planets c and d suggest a very thick atmosphere. The singularity of this system, which orbits a slightly evolved star that is just leaving the main sequence, makes it a good candidate for a deeper study from a dynamical point of view.