Radio emission in ultracool dwarfs: the nearby substellar triple system VHS 1256-1257
Author
dc.contributor.author
Guirado, J. C.
Author
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Azulay, R.
Author
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Gauza, B.
Author
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Pérez Torres, M. A.
Author
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Rebolo, R.
Author
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Climent, J. B.
Author
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Zapatero Osorio, M. R.
Admission date
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2018-07-31T17:31:54Z
Available date
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2018-07-31T17:31:54Z
Publication date
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2018
Cita de ítem
dc.identifier.citation
Astronomy & Astrophysics,610, A23 (2018)
es_ES
Identifier
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10.1051/0004-6361/201732130
Identifier
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https://repositorio.uchile.cl/handle/2250/150494
Abstract
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Aims. 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 60 mu Jy. We determined a spectral index alpha = -1.1 +/- 0.3 between 8 and 12 GHz, 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 3 sigma upper limit of 20 mu Jy. 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 5-8.5 GHz, from which we infer the presence of kG-intense magnetic fields in the M7.5 binary. Our data impose a 3 alpha upper bound to the radio flux density of the L7 object of 9 mu Jy at 10 GHz.