SIMBAD references

2024MNRAS.533.1654Z - Mon. Not. R. Astron. Soc., 533, 1654-1669 (2024/September-2)

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

ZHANG Z.H., RADDI R., BURGASSER A.J., CASEWELL S.L., SMART R.L., GALVEZ-ORTIZ M.C., JONES H.R.A., BAIG S., LODIEU N., GAUZA B., PAVLENKO Y.V., JIAO Y.F., ZHAO Z.K., ZHOU S.Y. and PINFIELD D.J.

Abstract (from CDS):

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$^{+1.9}_{-1.8}$ pc away with a projected separation of 1375$^{+35}_{-33}$ au. The primary is a cool DC white dwarf with a hydrogen dominated atmosphere, and has a total age of $10.5^{+3.3}_{-2.1}$ Gyr, based on white dwarf model fitting. The secondary is an L subdwarf with a metallicity of [M/H] = $-0.72^{+0.08}_{-0.10}$ (i.e. [Fe/H] = $-0.81\pm 0.10$) and $T_{\rm eff}$ = 2298$^{+45}_{-43}$ 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 $\sim$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.

Abstract Copyright: © 2024 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society.

Journal keyword(s): binaries: general - brown dwarfs - stars: Population II - subdwarfs - white dwarfs

Simbad objects: 24

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