Bibcode
Gauza, B.; Béjar, V. J. S.; Pérez-Garrido, A.; Lodieu, N.; Rebolo, R.; Zapatero Osorio, M. R.; Pantoja, B.; Velasco, S.; Jenkins, J. S.
Bibliographical reference
Monthly Notices of the Royal Astronomical Society, Volume 487, Issue 1, p.1149-1159
Advertised on:
7
2019
Citations
7
Refereed citations
7
Description
We demonstrate that the previously identified L/T transition brown dwarf
SDSS J213154.43-011939.3 (SDSS 2131-0119) is a widely separated
(82{^''.}3, ˜3830 au) common proper motion companion to
the low-mass star NLTT 51469, which we reveal to be a close binary
itself, separated by 0{^''.}64 ± 0{^''.}01
(˜30 au). We find the proper motion of SDSS 2131-0119 of
μαcos δ = -100 ± 20 mas yr-1
and μδ = -230 ± 20 mas yr-1
consistent with the proper motion of the primary provided by Gaia DR2:
μαcos δ = -95.49 ± 0.96 mas
yr-1 and μδ = -239.38 ± 0.96 mas
yr-1. Based on optical and near-infrared spectroscopy, we
classify the primary NLTT 51469A as an M3 ± 1 dwarf, estimate
photometrically the spectral type of its close companion NLTT 51469B at
˜M6, and confirm the spectral type of the brown dwarf to be L9
± 1. Using radial velocity, proper motion, and parallax, we
derived the UVW Galactic space velocities of NLTT 51469A, showing that
the system does not belong to any known young stellar moving group. The
high V, W velocities, lack of a 670.8 nm Li I absorption line, and
absence of H α emission, detected X-rays, or UV excess, indicate
that the system is likely a member of the thin disc population and is
older than 1 Gyr. For the parallactic distance of 46.6 ± 1.6 pc
from Gaia DR2, we determined luminosities of -1.50^{+0.02}_{-0.04} and
-4.4 ± 0.1 dex of the M3 and L9, respectively. Considering the
spectrophotometric estimation, which yields a slightly lower distance of
34^{+10}_{-13} pc, the obtained luminosities are -1.78^{+0.02}_{-0.04}
and -4.7^{+0.3}_{-0.5} dex. We also estimated their effective
temperatures and masses, and obtained 3410^{+140}_{-210} K and 0.42
± 0.02 M⊙ for the primary, and 1400-1650 K and
0.05-0.07 M⊙ for the wide companion. For the ˜M6
component, we estimated Teff = 2850 ± 200 K and m =
0.10^{+0.06}_{-0.01} M⊙.
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