A remarkable recurrent nova in M 31: The predicted 2014 outburst in X-rays with Swift
Abstract
The M 31 nova M31N 2008-12a was recently found to be a recurrent nova (RN) with a recurrence time of about 1 year. This is by far the fastest recurrence time scale of any known RNe. Our optical monitoring programme detected the predicted 2014 outburst of M31N 2008-12a in early October. We immediately initiated an X-ray/UV monitoring campaign with Swift to study the multiwavelength evolution of the outburst. We monitored M31N 2008-12a with daily Swift observations for 20 days after discovery, covering the entire supersoft X-ray source (SSS) phase. We detected SSS emission around day six after outburst. The SSS state lasted for approximately two weeks until about day 19. M31N 2008-12a was a bright X-ray source with a high blackbody temperature. The X-ray properties of this outburst were very similar to the 2013 eruption. Combined X-ray spectra show a fast rise and decline of the effective blackbody temperature. The short-term X-ray light curve showed strong, aperiodic variability which decreased significantly after about day 14. Overall, the X-ray properties of M31N 2008-12a are consistent with the average population properties of M 31 novae. The optical and X-ray light curves can be scaled uniformly to show similar time scales as those of the Galactic RNe U Sco or RS Oph. The SSS evolution time scales and effective temperatures are consistent with a high-mass WD. We predict the next outburst of M31N 2008-12a to occur in autumn 2015.
Keywords
Cite
@article{arxiv.1504.06237,
title = {A remarkable recurrent nova in M 31: The predicted 2014 outburst in X-rays with Swift},
author = {M. Henze and J. -U. Ness and M. J. Darnley and M. F. Bode and S. C. Williams and A. W. Shafter and G. Sala and M. Kato and I. Hachisu and M. Hernanz},
journal= {arXiv preprint arXiv:1504.06237},
year = {2015}
}
Comments
13 pages, 7 figures, 3 tables; accepted for publication in A&A