Primeval very low-mass stars and brown dwarfs – VIII. The first age benchmark L subdwarf, a wide companion to a halo white dwarf

We report the discovery of five white dwarf + ultracool dwarf systems identified as common proper motion wide binaries in the Gaia Catalogue of Nearby Stars. The discoveries include a white dwarf + L subdwarf binary, VVV 1256-62AB, a gravitationally bound system located 75.6 ¿pc away with a projecte...

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Detalles Bibliográficos
Autores: Zhang, ZengHua, Raddi, Roberto|||0000-0002-9090-9191, Burgasser, Adam, Casewell, Sarah, Laurence Smart, Richard, Galvez Ortiz, Maria Cruz, Jones, H., Baig, Sayan, Lodieu, Nicolas, Gauza, Bartosz, Pavlenko, Ya, Jiao, Ya Feng, Zhao, Zongbao, Zhou, Siyan, Pinfield, D. J.
Tipo de recurso: artículo
Fecha de publicación:2024
País:España
Institución:Universitat Politècnica de Catalunya (UPC)
Repositorio:UPCommons. Portal del coneixement obert de la UPC
Idioma:inglés
OAI Identifier:oai:upcommons.upc.edu:2117/427426
Acceso en línea:https://hdl.handle.net/2117/427426
https://dx.doi.org/10.1093/mnras/stae1851
Access Level:acceso abierto
Palabra clave:Binaries: general
Brown dwarfs
Stars: Population II
Subdwarfs
White dwarfs
Àrees temàtiques de la UPC::Física
Descripción
Sumario:We report the discovery of five white dwarf + ultracool dwarf systems identified as common proper motion wide binaries in the Gaia Catalogue of Nearby Stars. The discoveries include a white dwarf + L subdwarf binary, VVV 1256-62AB, a gravitationally bound system located 75.6 ¿pc away with a projected separation of 1375 au. The primary is a cool DC white dwarf with a hydrogen dominated atmosphere, and has a total age of ¿Gyr, based on white dwarf model fitting. The secondary is an L subdwarf with a metallicity of [M/H] = (i.e. [Fe/H] = ¿) and = 2298 ¿K based on atmospheric model fitting of its optical to near infrared spectrum, and likely has a mass just above the stellar/substellar boundary. The subsolar metallicity of the L subdwarf and the system’s total space velocity of 406¿km¿s-1 indicates membership in the Galactic halo, and it has a flat eccentric Galactic orbit passing within 1¿kpc of the centre of the Milky Way every 0.4¿Gyr and extending to 15–31¿kpc at apogal. VVV 1256-62B is the first L subdwarf to have a well-constrained age, making it an ideal benchmark of metal-poor ultracool dwarf atmospheres and evolution.

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