A remarkable recurrent nova in M 31: The optical observations

• Published in: Astronomy and astrophysics (Berlin) Vol. 563; p. np
• Main Authors: Darnley, M. J., Williams, S. C., Bode, M. F., Henze, M., Ness, J.-U., Shafter, A. W., Hornoch, K., Votruba, V.
• Format: Journal Article
• Language: English
• Published: EDP Sciences 01.03.2014
• Subjects: Accretion disks; Asymptotic properties; cataclysmic variables; galaxies: individual: M 31; Historic; Hubble Space Telescope; Nova; novae; Photometry; Progenitors (astrophysics); stars: individual: M 31N 2008-12a; Telescopes; ASE, Atlantic, Canary Is., La Palma; British Isles, England, Merseyside, Liverpool
• ISSN: 0004-6361; 1432-0746
• DOI: 10.1051/0004-6361/201423411

Context. In late Nov. 2013 the fifth eruption in five years of the M 31 recurrent nova M 31N 2008-12a was announced. Aims. In this Letter we address the optical lightcurve and progenitor system of M 31N 2008-12a. Methods. Optical imaging data of the 2013 eruption from the Liverpool Telescope, La Palma; Danish 1.54 m Telescope, La Silla; and archival Hubble Space Telescope near-IR, optical, and near-UV data are astrometrically and photometrically analysed. Results. Photometry of the 2013 eruption, combined with three previous eruptions, enabled construction of a template lightcurve of a very fast nova (\hbox{$t_{2}\left(V\right)\simeq4$}t2V)(≃4 days). The archival data allowed recovery of the progenitor system in optical and near-UV data, indicating a red-giant secondary with bright accretion disk, or alternatively a system with a sub-giant secondary but dominated by a disk. Conclusions. The eruptions of M 31N 2008-12a, and a number of historic X-ray detections, indicate a unique system with a recurrence timescale of ~1 yr. This implies the presence of a very high-mass white dwarf and a high accretion rate. The recovered progenitor system is consistent with such an elevated rate of accretion. We encourage additional observations, especially towards the end of 2014.