A prompt radio transient associated with a gamma-ray superflare from the young M dwarf binary DG CVn. (15th November 2014)

• Record Type: Journal Article
• Authors: Fender, R. P.; Anderson, G. E.; Osten, R.; Staley, T.; Rumsey, C.; Grainge, K.; Saunders, R. D. E.
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 446:Number 1(2015:Jan.)
• Page Start: L66
• Page End: L70
• Publication Date: 2014-11-15
• Subjects: Acceleration of particles -- telescopes -- stars: flare -- radio continuum: stars -- X-rays: stars; Astronomy -- Research -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnrasl/slu165
• Languages: English
• ISSNs: 1745-3933

Abstract

Abstract : On 2014 April 23, the Swift satellite detected a gamma-ray superflare from the nearby star system DG CVn. This system comprises an M-dwarf binary with extreme properties: it is very young and at least one of the components is a very rapid rotator. The gamma-ray superflare is one of only a handful detected by Swift in a decade. As part of our AMI-LA Rapid Response Mode, ALARRM, we automatically slewed to this target, were taking data at 15 GHz within 6 min of the burst, and detected a bright (∼100 mJy) radio flare. This is the earliest detection of bright, prompt, radio emission from a high-energy transient ever made with a radio telescope, and is possibly the most luminous incoherent radio flare ever observed from a red dwarf star. An additional bright radio flare, peaking at around 90 mJy, occurred around one day later, and there may have been further events between 0.1–1 d when we had no radio coverage. The source subsequently returned to a quiescent level of 2–3 mJy on a time-scale of about 4 d. Although radio emission is known to be associated with active stars, this is the first detection of large radio flares associated with a gamma-ray superflare, and demonstrates both feasibility and scientific importance of rapid response modes on radio telescopes.