Proyecto de Investigación: ExoplANETS 776403
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776403
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ESPRESSO mass determination of TOI-263b: an extreme inhabitant of the brown dwarf desert
(EDP Sciences, 2021-06-04) Pallé, E.; Luque, R.; Zapatero Osorio, M. R.; Parviainen, H.; Ikoma, M.; Tabernero, H. M.; Zechmeister, M.; Mustill, A. J.; Béjar, V. J. S.; Narita, N.; Agencia Estatal de Investigación (AEI), European Research Council; Fundacao para a Ciencia e a Tecnologia (FCT); National Aeronautics and Space Administration (NASA); National Science Foundation (NSF); Japan Society for the Promotion of Science (KAKENHI)
The TESS mission has reported a wealth of new planetary systems around bright and nearby stars amenable for detailed characterizations of planet properties and atmospheres. However, not all interesting TESS planets orbit around bright host stars. TOI-263 b is a validated ultra-short-period substellar object in a 0.56-day orbit around a faint (V = 18.97) M 3.5 dwarf star. The substellar nature of TOI-263 b was explored using multicolor photometry: a true radius of 0.87 ± 0.21 RJ was determined, establishing TOI-263 b ’s nature as somewhere between an inflated Neptune and a brown dwarf. The orbital period-radius parameter space occupied by TOI-263 b is quite unique, which prompted a further characterization of its true nature. Here, we report radial velocity measurements of TOI-263 obtained with three VLT units and the ESPRESSO spectrograph to retrieve the mass of TOI-263 b. We find that TOI-263 b is a brown dwarf with a mass of 61.6 ± 4.0 MJup. Additionally, the orbital period of the brown dwarf is found to be synchronized with the rotation period of the host star, and the system is found to be relatively active, possibly revealing a star–brown dwarf interaction. All these findings suggest that the system’s formation history might be explained via disk fragmentation and a later migration to close-in orbits. If the system is found to be unstable, TOI-263 will be an excellent target to test the migration mechanisms before the brown dwarf becomes “engulfed” by its parent star.
Unveiling the power spectra of delta Scuti stars with TESS The temperature, gravity, and frequency scaling relation
(EDP Sciences, 2020-06-11) Barceló Forteza, S.; Moya, A.; Barrado, D.; Martín Ruiz, S.; Suárez, J. C.; García Hernández, A.; Solano, Enrique; National Aeronautics and Space Administration (NASA); Ministerio de Economía y Competitividad (MINECO); European Research Council (ERC); Agencia Estatal de Investigación (AEI); Universidad de Granada (UGR); Junta de Andalucía; 0000-0001-9281-2919; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFISICA DE ANDALUCIA (IAA), SEV-2017-0709
Thanks to high-precision photometric data legacy from space telescopes like CoRoT andKepler, the scientific community could detect and characterize the power spectra of hundreds of thousands of stars. Using the scaling relations, it is possible to estimate masses and radii for solar-type pulsators. However, these stars are not the only kind of stellar objects that follow these rules:delta Scuti stars seem to be characterized with seismic indexes such as the large separation (Delta nu). Thanks to long-duration high-cadence TESS light curves, we analysed more than two thousand of this kind of classical pulsators. In that way, we propose the frequency at maximum power (nu(max)) as a proper seismic index since it is directly related with the intrinsic temperature, mass and radius of the star. This parameter seems not to be affected by rotation, inclination, extinction or resonances, with the exception of the evolution of the stellar parameters. Furthermore, we can constrain rotation and inclination using the departure of temperature produced by the gravity-darkening effect. This is especially feasible for fast rotators as most of delta Scuti stars seem to be. © ESO 2020.
Wide companions to M and L subdwarfs with Gaia and the Virtual Observatory
(EDP Sciences, 2021-06-29) González Payo, J.; Cortés Contreras, M.; Lodieu, N.; Zhang, Z. H.; Gálves Ortiz, M. C.; Solano, Enrique; Agencia Estatal de Investigación (AEI); European Research Council (ERC)
Aims. The aim of the project is to identify wide common proper motion companions to a sample of spectroscopically confirmed M and L metal-poor dwarfs (also known as subdwarfs) to investigate the impact of metallicity on the binary fraction of low-mass metal-poor binaries and to improve the determination of their metallicity from the higher-mass binary.
Methods. We made use of Virtual Observatory tools and large-scale public surveys to look in Gaia for common proper motion companions to a well-defined sample of ultracool subdwarfs with spectral types later than M5 and metallicities below or equal to −0.5 dex. We collected low-resolution optical spectroscopy for our best system, which is a binary composed of one sdM1.5 subdwarf and one sdM5.5 subdwarf located at ∼1360 au, and for another two likely systems separated by more than 115 000 au.
Results. We confirm one wide companion to an M subdwarf, and infer a multiplicity for M subdwarfs (sdMs) of 1.0−1.0+2.0% for projected physical separations of up to 743 000 au. We also find four M–L systems, three of which are new detections. No colder companion was identified in any of the 219 M and L subdwarfs of the sample, mainly because of limitations on the detection of faint sources with Gaia. We infer a frequency of wide systems for sdM5–9.5 of 0.60−0.60+1.17% for projected physical separations larger than 1 360 au (up to 142 400 au). This study shows a multiplicity rate of 1.0−1.0+2.0% in sdMs, and 1.9−1.9+3.7% in extreme M subdwarfs. We did not find any companion for the ultra M subdwarfs of our sample, establishing an upper limit of 5.3% on binarity for these objects.
Homogeneous study of Herbig Ae/Be stars from spectral energy distributions and Gaia EDR3
(EDP Sciences, 2021-06-25) Guzmán Díaz, J.; Mendigutía, I.; Montesinos, B.; Oudmaijer, R. D.; Vioque, M.; Rodrigo, C.; Meeus, G.; Marcos Arenal, P.; Solano, Enrique; Comunidad de Madrid; Agencia Estatal de Investigación (AEI); European Research Council (ERC)
Context. Herbig Ae/Be stars (HAeBes) have so far been studied based on relatively small samples that are scattered throughout the sky. Their fundamental stellar and circumstellar parameters and statistical properties were derived with heterogeneous approaches before Gaia.
Aims. Our main goal is to contribute to the study of HAeBes from the largest sample of such sources to date, for which stellar and circumstellar properties have been determined homogeneously from the analysis of the spectral energy distributions (SEDs) and Gaia EDR3 parallaxes and photometry.
Methods. Multiwavelength photometry was compiled for 209 bona fide HAeBes for which Gaia EDR3 distances were estimated. Using the Virtual Observatory SED Analyser (VOSA), photospheric models were fit to the optical SEDs to derive stellar parameters, and the excesses at infrared (IR) and longer wavelengths were characterized to derive several circumstellar properties. A statistical analysis was carried out to show the potential use of such a large dataset.
Results. The stellar temperature, luminosity, radius, mass, and age were derived for each star based on optical photometry. In addition, their IR SEDs were classified according to two different schemes, and their mass accretion rates, disk masses, and the sizes of the inner dust holes were also estimated uniformly. The initial mass function fits the stellar mass distribution of the sample within 2 < M*∕M⊙ < 12. In this aspect, the sample is therefore representative of the HAeBe regime and can be used for statistical purposes when it is taken into account that the boundaries are not well probed. Our statistical study does not reveal any connection between the SED shape from the Meeus et al. (2001, A&A, 365, 476) classification and the presence of transitional disks, which are identified here based on the SEDs that show an IR excess starting at the K band or longer wavelengths. In contrast, only ~28% of the HAeBes have transitional disks, and the related dust disk holes are more frequent in HBes than in HAes (~34% vs. 15%). The relatively small inner disk holes and old stellar ages estimated for most transitional HAes indicate that photoevaporation cannot be the main mechanism driving disk dissipation in these sources. In contrast, the inner disk holes and ages of most transitional HBes are consistent with the photoevaporation scenario, although these results alone do not unambiguously discard other disk dissipation mechanisms.Conclusions. The complete dataset is available online through a Virtual Observatory-compliant archive, representing the most recent reference for statistical studies on the HAeBe regime. VOSA is a complementary tool for the future characterization of newly identified HAeBes.
Lupus DANCe Census of stars and 6D structure with Gaia-DR2 data
(EDP Sciences, 2020-11-16) Galli, P. A. B.; Bouy, H.; Olivares, J.; Miret Roig, N.; Vieira, R. G.; Sarro, L. M.; Barrado, D.; Berihuete, A.; Bertout, C.; Bertín, E.; Cuillandre, J. C.; European Research Council (ERC); Agencia Estatal de Investigación (AEI); Agence Nationale de la Recherche (ANR); Berihuete, A. [0000-0002-8589-4423]; Georgetti Vieira, R. [0000-0002-3607-3979]; Galli, P. [0000-0003-2271-9297]; Olivares Romero, J. [0000-0003-0316-2956]; Sarro, L. M. [0000-0002-5622-5191]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. Lupus is recognised as one of the closest star-forming regions, but the lack of trigonometric parallaxes in the pre-Gaia era hampered many studies on the kinematic properties of this region and led to incomplete censuses of its stellar population.
Aims. We use the second data release of the Gaia space mission combined with published ancillary radial velocity data to revise the census of stars and investigate the 6D structure of the Lupus complex.
Methods. We performed a new membership analysis of the Lupus association based on astrometric and photometric data over a field of 160 deg2 around the main molecular clouds of the complex and compared the properties of the various subgroups in this region.
Results. We identified 137 high-probability members of the Lupus association of young stars, including 47 stars that had never been reported as members before. Many of the historically known stars associated with the Lupus region identified in previous studies are more likely to be field stars or members of the adjacent Scorpius-Centaurus association. Our new sample of members covers the magnitude and mass range from G ≃ 8 to G ≃ 18 mag and from 0.03 to 2.4 M⊙, respectively. We compared the kinematic properties of the stars projected towards the molecular clouds Lupus 1–6 and showed that these subgroups are located at roughly the same distance (about 160 pc) and move with the same spatial velocity. Our age estimates inferred from stellar models show that the Lupus subgroups are coeval (with median ages ranging from about 1 to 3 Myr). The Lupus association appears to be younger than the population of young stars in the Corona-Australis star-forming region recently investigated by our team using a similar methodology. The initial mass function of the Lupus association inferred from the distribution of spectral types shows little variation compared to other star-forming regions.
Conclusions. In this paper, we provide an updated sample of cluster members based on Gaia data and construct the most complete picture of the 3D structure and 3D space motion of the Lupus complex.
