Report
Radio emission in a nearby ultracool dwarf binary: a multi-frequency study
| العنوان: | Radio emission in a nearby ultracool dwarf binary: a multi-frequency study |
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| المؤلفون: | Climent, Juan B., Guirado, J. C., Zapatero-Osorio, M. R., Zakhozhay, O. V., Pérez-Torres, M. A., Azulay, R., Gauza, B., Rebolo, R., Béjar, V. J. S., Martín-Pintado, J., Lefèvre, C. |
| المصدر: | A&A 660, A65 (2022) |
| سنة النشر: | 2022 |
| المجموعة: | Astrophysics |
| مصطلحات موضوعية: | Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Astrophysics of Galaxies |
| الوصف: | The substellar triple system VHS J125601.92$-$125723.9 is composed by an equal-mass M7.5 brown dwarf binary and a L7 low-mass substellar object. In this work, we aim to identify the origin of the radio emission occurring in the central binary of VHS 1256$-$1257 while discussing the expected mechanisms involved in the radio emission of ultracool dwarfs (UCDs). We observed this system with the Karl G. Jansky Very Large Array, the European very-long-baseline interferometry (VLBI) Network, the enhanced Multi Element Remotely Linked Interferometer Network, the NOrthern Extended Millimeter Array, and the Atacama Large Millimetre Array at frequencies ranging from 5 GHz up to 345 GHz in several epochs during 2017, 2018, and 2019. We have found radio emission at 6 GHz and 33 GHz coincident with the expected position of the central binary of VHS~1256$-$1257. The Stokes I density flux detected were 73 $\pm$ 4 $\mu$Jy and 83 $\pm$ 13 $\mu$Jy, respectively, with no detectable circular polarisation or pulses. No emission is detected at higher frequencies (230 GHz and 345 GHz) nor at 5 GHz with VLBI arrays. The emission appears to be stable over almost 3 years at 6 GHz. To explain the constraints obtained both from the detections and non-detections we considered multiple scenarios including thermal and non-thermal emission, and different contributions from each component of the binary. Our results can be well explained by non-thermal gyrosynchrotron emission originating at radiation belts with a low plasma density (n$_e$ = 300$-$700 cm$^{-3}$), a moderate magnetic field strength (B $\approx$ 140 G), and an energy distribution of electrons following a power-law ($d N / d E \propto E^{- \delta}$) with $\delta$ fixed at 1.36. These radiation belts would need to be present in both components and also be viewed equatorially. Comment: Accepted for publication in A&A. 13 pages, 6 figures |
| نوع الوثيقة: | Working Paper |
| DOI: | 10.1051/0004-6361/202142260 |
| URL الوصول: | http://arxiv.org/abs/2201.12606 |
| رقم الانضمام: | edsarx.2201.12606 |
| قاعدة البيانات: | arXiv |
| DOI: | 10.1051/0004-6361/202142260 |
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