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

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

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2017 vol. 469 p. 4236 - 4248

0035-8711

We present the results of our analysis of new optical, ultraviolet (UV) and X-ray observations of a highly variable source − AX J1549.8−5416. Both the detection of several fast rise, exponential decay outbursts in the optical light curve and the lack of He II emission lines in the optical spectra suggest AX J1549.8−5416 is a cataclysmic variable of the dwarf nova (DN) type. The multiwavelength analysis of three mini-outbursts and one normal outburst represent one of the most complete multiwavelength studies of a DN and help to refine the relationship between the X-ray, UV and optical emission in this system. We find that the UV emission is delayed with respect to the optical by 1.0−5.4 days during the rising phase of the outburst. The X-ray emission is suppressed during the peak of the optical outburst and recovers during the end of the outburst. From our analysis of archival Swift, Chandra and XMM-Newton observations of AX J1549.8−5416, we estimate this DN has a high duty cycle (∼50%), suggesting a quiescent X-ray luminosity larger than 1032 erg/s. We also find the X-ray and UV flux are roughly anti-correlated. Furthermore, we find that, at low X-ray fluxes, the X-ray spectrum is well described by a single temperature thermal plasma model, while at high X-ray fluxes, an isobaric cooling flow model also works. We find that the maximum temperature of the plasma in quiescence is significantly higher than that in outburst.