Multiwavelength monitoring of a very active dwarf nova AX J1549.8-5416 with an unusually high duty cycle

GUOBAO ZHANG; JOSEPH D. GELFAND; DAVID M. RUSSELL; FRASER LEWIS; NICOLA MASETTI; FEDERICO BERNARDINI; ANDRUCHOW, I.; ZIBECCHI, LORENA

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2017 vol. 496 p. 4236 - 4248

0035-8711

We present the new optical, UV and X-ray observations of the typical CV AXJ1549.8?5416. Both the fast rise, exponential decay optical outbursts and the lackof apparent He II emission lines in the optical spectra suggest that AX J1549.8?5416 is a typical dwarf nova(DN). We present multi-wavelength (optical/UV/X-ray)observations of DN AX J1549.8?5416 throughout three mini-outbursts and one normaloutburst. These data represent one of the most complete multiwavelength studies of aDN and help to refine the X-ray/UV/optical relation in this system. We find the UVemission delays optical (1.0 − 5.4 days) during the rising phase of the outburst. TheX-ray emission shows suppression during the outburst peak and recovery during theend of the outburst.We also analyse the archival Swift, Chandra and XMM-Newton observations ofAX J1549.8?5416. We find a roughly anti-correlation between X-ray and UV flux. Thehigh-resolution X-ray spectra of XMM-Newton and Chandra can be well describedeither by a single temperature thermal plasma model or by an isobaric cooling flowmodel when its X-ray flux is high. We find the maximum temperature of the plasmain quiescence is significant higher than that in outburst in AX J1549.8?5416. The lowNH indicates AX J1549.8?5416 is a nearby and very X-ray bright Galactic DN. Ourestimated high duty cycle suggests the X-ray luminosity of this source should be largerthan 1032 erg/s in quiescence.