Serendipitous discovery of radio flaring behaviour from a nearby M dwarf with MeerKAT

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Abstract
We report on the detection of MKT J174641.0−321404, a new radio transient found in untargeted searches of wide-field MeerKAT radio images centred on the black hole X-ray binary H1743−322. MKT J174641.0−321404 is highly variable at 1.3 GHz and was detected three times during 11 observations of the field in late 2018, reaching a maximum flux density of 590 ± 60 µJy. We associate this radio transient with a high proper motion, M dwarf star SCR 1746−3214 12 pc away from the Sun. Multiwavelength observations of this M dwarf indicate flaring activity across the electromagnetic spectrum, consistent with emission expected from dMe stars, and providing upper limits on quiescent brightness in both the radio and X-ray regimes. TESS photometry reveals a rotational period for SCR 1746−3214 of 0.2292 ± 0.0025 d, which at its estimated radius makes the star a rapid rotator, comparable to other low-mass systems. Dedicated spectroscopic follow up confirms the star as a mid-late spectral M dwarf with clear magnetic activity indicated by strong H α emission. This transient’s serendipitous discovery by MeerKAT, along with multiwavelength characterization, make it a prime demonstration of both the capabilities of the current generation of radio interferometers and the value of simultaneous observations by optical facilities such as MeerLICHT. Our results build upon the literature of M dwarfs’ flaring behaviour, particularly relevant to the habitability of their planetary systems.
Funding Information
  • Science and Technology Facilities Council
  • Alfred P. Sloan Foundation
  • European Research Council (694745)
  • National Research Foundation (111692)
  • Radboud University
  • Universityof CapeTown
  • Netherlands Organisation for Scientific Research
  • Oxford University
  • University of Manchester
  • University of Amsterdam
  • University of Pretoria
  • University of the Western Cape

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