Examinando por Autor "Mamajek, E. E."

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Acceso Abierto
Pleiades or Not? Resolving the Status of the Lithium-rich M Dwarfs HHJ 339 and HHJ 430
(The Institute of Physics (IOP), 2020-06-18) Stauffer, J.; Barrado, D.; David, T.; Rebull, L. M.; Hillenbrand, L. A.; Mamajek, E. E.; Oppenheimer, R.; Aigrain, S.; Bouy, H.; Lillo Box, J.; Agencia Estatal de Investigación (AEI); National Aeronautics and Space Administration (NASA); Stauffer, J. [0000-0003-3595-7382]; David, T. [0000-0001-6534-6246]; Rebull, L. M. [0000-0001-6381-515X]; Mamajek, E. E. [0000-0003-2008-1488]; Oppenheimer, R. [0000-0001-7130-7681]; Aigrain, S. [0000-0003-1453-0574]; Bouy, H. [0000-0002-7084-487X]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Oppenheimer et al. discovered two M5 dwarfs in the Pleiades with nearly primordial lithium. These stars are not low enough in mass to represent the leading edge of the lithium depletion boundary at Pleiades age (~125 Myr). A possible explanation for the enhanced lithium in these stars is that they are actually not members of the Pleiades but instead are members of a younger moving group seen in projection toward the Pleiades. We have used data from Gaia DR2 to confirm that these two stars, HHJ 339 and HHJ 430, are indeed not members of the Pleiades. Based on their space motions, parallaxes, and positions in a Gaia-based color–magnitude diagram, it is probable that these two stars are about 40 parsecs foreground to the Pleiades and have ages of ~25 Myr. Kinematically they are best matched to the 32 Ori moving group.
Acceso Abierto
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.