Query : 2018A&A...610A..23G

2018A&A...610A..23G - Astronomy and Astrophysics, volume 610A, 23-23 (2018/2-1)

Radio emission in ultracool dwarfs: The nearby substellar triple system VHS 1256-1257.


Abstract (from CDS):

Aim. With the purpose of investigating the radio emission of new ultracool objects, we carried out a targeted search in the recently discovered system VHS J125601.92-125723.9 (hereafter VHS 1256-1257); this system is composed by an equal-mass M7.5 binary and a L7 low-mass substellar object located at only 15.8 pc.
Methods. We observed in phase-reference mode the system VHS 1256-1257 with the Karl G. Jansky Very Large Array at X band and L band and with the European VLBI Network at L band in several epochs during 2015 and 2016.
Results. We discovered radio emission at X band spatially coincident with the equal-mass M7.5 binary with a flux density of 60µJy. We determined a spectral index α=-1.1±0.3 between 8 and 12GHz, suggesting that non-thermal, optically thin, synchrotron, or gyrosynchrotron radiation is responsible for the observed radio emission. Interestingly, no signal is seen at L band where we set a 3σ upper limit of 20µJy. This might be explained by strong variability of the binary or self-absorption at this frequency. By adopting the latter scenario and gyrosynchrotron radiation, we constrain the turnover frequency to be in the interval 5-8.5GHz, from which we infer the presence of kG-intense magnetic fields in the M7.5 binary. Our data impose a 3σ upper bound to the radio flux density of the L7 object of 9µJy at 10GHz.

Abstract Copyright: © ESO, 2018

Journal keyword(s): brown dwarfs - stars: magnetic field - radiation mechanisms: general - techniques: interferometric

Simbad objects: 5

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Number of rows : 5
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
1 ICRF J125431.4-131716 Bz? 12 54 31.4682764 -13 17 16.211591       20.30   ~ 16 1
2 NAME VHS J1256-1257B BD* 12 56 01.83264 -12 57 27.6912           L8.0 44 0
3 VHS J1256-1257 LM* 12 56 02.15136 -12 57 21.7116     17.759   13.318 M7.0 36 0
4 ICRF J130313.8-105117 BLL 13 03 13.86795252 -10 51 17.1281751     22.90 21.41   ~ 20 1
5 3C 286 Sy1 13 31 08.2885060664 +30 30 32.960825107   17.51 17.25     ~ 3926 2

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