Examinando por Autor "Burgasser, A. J."

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The Gaia Ultra-Cool Dwarf Sample – III: seven new multiple systems containing at least one Gaia DR2 ultracool dwarf
(Oxford Academics: Oxford University Press, 2020-04-15) Marocco, F.; Smart, R. L.; Mamajek, E. E.; Sarro, L. M.; Burgasser, A. J.; Caballero, J. A.; Rees, J. M.; Caselden, D.; Cruz, K. L.; Van Linge, R.; Pinfield, D. J.; National Aeronautics and Space Administration (NASA); Agencia Estatal de Investigación (AEI); 0000-0002-5622-5191; 0000-0002-4424-4766; 0000-0002-6523-9536; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
We present 10 new ultracool dwarfs in seven wide binary systems discovered using Gaia second data release data, identified as part of our Gaia Ultra-Cool Dwarf Sample project. The seven systems presented here include an L1 companion to the G5 IV star HD 164507, an L1: companion to the V478 Lyr AB system, an L2 companion to the metal-poor K5 V star CD-28 8692, an M9 V companion to the young variable K0 V star LT UMa, and three low-mass binaries consisting of late Ms and early Ls. The HD 164507, CD-28 8692, V478 Lyr, and LT UMa systems are particularly important benchmarks, because the primaries are well characterized and offer excellent constraints on the atmospheric parameters and ages of the companions. We find that the M8 V star 2MASS J23253550+4608163 is ∼2.5 mag overluminous compared to M dwarfs of similar spectral type, but at the same time it does not exhibit obvious peculiarities in its near-infrared spectrum. Its overluminosity cannot be explained by unresolved binarity alone. Finally, we present an L1+L2 system with a projected physical separation of 959 au, making this the widest L + L binary currently known.
Restringido
Ultracool dwarfs in deep extragalactic surveys using the virtual observatory: ALHAMBRA and COSMOS
(Oxford Academics: Oxford University Press, 2021-02-01) Gálvez Ortiz, M. C.; Martín, E. L.; Gómez Muñoz, I. M.; Rodrigo, C.; Burgasser, A. J.; Lodieu, N.; Béjar, V. J. S.; Huélamo, N.; Morales Calderón, M.; Bouy, H.; Solano, Enrique; Agencia Estatal de Investigación (AEI); Ministerio de Economía y Competitividad (MINECO); Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Ultracool dwarfs (UCDs) encompass a wide variety of compact stellar-like objects with spectra classified as late-M, L, T, and Y. Most of them have been discovered using wide-field imaging surveys. The Virtual Observatory (VO) has proven to be of great utility to efficiently exploit these astronomical resources. We aim to validate a VO methodology designed to discover and characterize UCDs in deep extragalactic surveys like Advance Large Homogeneous Area Medium-Band Redshift Astronomical (ALHAMBRA) and Cosmological Evolution Survey (COSMOS). Three complimentary searches based on parallaxes, proper motions and colours, respectively, were carried out. A total of 897 candidate UCDs were found, with only 16 previously reported in SIMBAD. Most of the new UCDs reported here are likely late-M and L dwarfs because of the limitations imposed by the utilization of optical (Gaia DR2 and r-band) data. We complement ALHAMBRA and COSMOS photometry with other catalogues in the optical and infrared using VOSA, a VO tool that estimates effective temperatures from the spectral energy distribution fitting to collections of theoretical models. The agreement between the number of UCDs found in the COSMOS field and theoretical estimations together with the low false-negative rate (known UCDs not discovered in our search) validates the methodology proposed in this work, which will be used in the forthcoming wide and deep surveys provided by the Euclid space mission. Simulations of Euclid number counts for UCDs detectable in different photometric passbands are presented for a wide survey area of 15 000 deg2, and the limitations of applicability of Euclid data to detect UCDs using the methods employed in this paper are discussed.