Issue |
A&A
Volume 678, October 2023
|
|
---|---|---|
Article Number | A161 | |
Number of page(s) | 10 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361/202347141 | |
Published online | 17 October 2023 |
Plausible association of distant late M dwarfs with low-frequency radio emission⋆,⋆⋆
1
Leiden Observatory, Leiden University, PO Box 9513 2300 RA Leiden, The Netherlands
e-mail: gloudemans@strw.leidenuniv.nl
2
ASTRON, Netherlands Institute for Radio Astronomy, Oude Hoogeveensedijk 4, Dwingeloo 7991 PD, The Netherlands
3
Institute for Astronomy, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
4
Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
5
Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
6
Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwa-no-Ha, Kashiwa City, Chiba 277-8582, Japan
7
McDonald Observatory, University of Texas at Austin, 2515 Speedway, Stop C1402, Austin, TX 78712, USA
8
Department of Astronomy, University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, TX 78712, USA
9
Hobby Eberly Telescope, University of Texas, 2515 Speedway, Stop C1402, Austin, TX 78712, USA
10
Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK
11
University of Colorado Boulder, Laboratory for Atmospheric and Space Physics, 3665 Discovery Drive, Boulder, CO 80303, USA
12
Max-Planck Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
Received:
9
June
2023
Accepted:
8
August
2023
We present the serendipitous discovery of eight distant (> 50 pc) late M dwarfs with plausible associated radio emission at 144 MHz. The M-dwarf nature of our sources has been confirmed with optical spectroscopy performed using HET/LRS2 and Subaru/FOCAS, and their radio flux densities are within the range of 0.5−1.0 mJy at 144 MHz. Considering the radio-optical source separation and source densities of the parent catalogues, we suggest that it is statistically probable that the M dwarfs are associated with the radio emission. However, it remains plausible that for some of the sources the radio emission originates from an optically faint and red galaxy hiding behind the M dwarf. The isotropic radio luminosities (∼1017 − 18 erg s−1 Hz−1) of the M dwarfs suggest that if the association is real, the radio emission is likely driven by a coherent emission process produced via plasma or electron-cyclotron maser instability processes, which is potentially caused by binary interaction. Long-term monitoring in the radio and high-resolution radio follow-up observations are necessary to search for any variability and pinpoint the radio emission to determine whether our tentative conclusion that these ultracool dwarfs are radio emitting is correct. If the low-frequency radio emission is conclusively associated with the M dwarfs, this would reveal a new population of optically faint and distant (> 50 pc) radio-emitting M dwarfs.
Key words: stars: low-mass / radio continuum: stars / techniques: spectroscopic
The spectra and photometric measurements are available at the CDS via anonymous ftp to cdsarc.cds.unistra.fr (130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/678/A161
Based on observations obtained with the Hobby-Eberly Telescope (HET), which is a joint project of the University of Texas at Austin, Pennsylvania State University, Ludwig-Maximillians-Universitaet Muenchen, and Georg-August Universitaet Goettingen. The HET is named in honor of its principal benefactors, William P. Hobby and Robert E. Eberly.
© The Authors 2023
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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