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arXiv · 1607.08082

M31N 2008-12a - the remarkable recurrent nova in M31: Pan-chromatic observations of the 2015 eruption

M. J. Darnley·M. Henze·M. F. Bode·I. Hachisu·M. Hernanz·K. Hornoch·R. Hounsell·M. Kato·J. -U. Ness·J. P. Osborne·K. L. Page·V. A. R. M. Ribeiro·P. Rodriguez-Gil·A. W. Shafter·M. M. Shara·I. A. Steele·S. C. Williams·A. Arai·I. Arcavi·E. A. Barsukova·P. Boumis·T. Chen·S. Fabrika·J. Figueira·X. Gao·N. Gehrels·P. Godon·V. P. Goranskij·D. J. Harman·D. H. Hartmann·G. Hosseinzadeh·J. Chuck Horst·K. Itagaki·J. Jose·F. Kabashima·A. Kaur·N. Kawai·J. A. Kennea·S. Kiyota·H. Kucakova·K. M. Lau·H. Maehara·H. Naito·K. Nakajima·K. Nishiyama·T. J. O'Brien·R. Quimby·G. Sala·Y. Sano·E. M. Sion·A. F. Valeev·F. Watanabe·M. Watanabe·B. F. Williams·Z. Xu
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Abstract

The Andromeda Galaxy recurrent nova M31N 2008-12a had been observed in eruption ten times, including yearly eruptions from 2008-2014. With a measured recurrence period of $P_\mathrm{rec}=351\pm13$ days (we believe the true value to be half of this) and a white dwarf very close to the Chandrasekhar limit, M31N 2008-12a has become the leading pre-explosion supernova type Ia progenitor candidate. Following multi-wavelength follow-up observations of the 2013 and 2014 eruptions, we initiated a campaign to ensure early detection of the predicted 2015 eruption, which triggered ambitious ground and space-based follow-up programs. In this paper we present the 2015 detection; visible to near-infrared photometry and visible spectroscopy; and ultraviolet and X-ray observations from the Swift observatory. The LCOGT 2m (Hawaii) discovered the 2015 eruption, estimated to have commenced at Aug. $28.28\pm0.12$ UT. The 2013-2015 eruptions are remarkably similar at all wavelengths. New early spectroscopic observations reveal short-lived emission from material with velocities $\sim13000$ km s$^{-1}$, possibly collimated outflows. Photometric and spectroscopic observations of the eruption provide strong evidence supporting a red giant donor. An apparently stochastic variability during the early super-soft X-ray phase was comparable in amplitude and duration to past eruptions, but the 2013 and 2015 eruptions show evidence of a brief flux dip during this phase. The multi-eruption Swift/XRT spectra show tentative evidence of high-ionization emission lines above a high-temperature continuum. Following Henze et al. (2015a), the updated recurrence period based on all known eruptions is $P_\mathrm{rec}=174\pm10$ d, and we expect the next eruption of M31N 2008-12a to occur around mid-Sep. 2016.

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M. J. Darnley, M. Henze, M. F. Bode, I. Hachisu, M. Hernanz, K. Hornoch, R. Hounsell, M. Kato, J. -U. Ness, J. P. Osborne, K. L. Page, V. A. R. M. Ribeiro, P. Rodriguez-Gil, A. W. Shafter, M. M. Shara, I. A. Steele, S. C. Williams, A. Arai, I. Arcavi, E. A. Barsukova, P. Boumis, T. Chen, S. Fabrika, J. Figueira, X. Gao, N. Gehrels, P. Godon, V. P. Goranskij, D. J. Harman, D. H. Hartmann, G. Hosseinzadeh, J. Chuck Horst, K. Itagaki, J. Jose, F. Kabashima, A. Kaur, N. Kawai, J. A. Kennea, S. Kiyota, H. Kucakova, K. M. Lau, H. Maehara, H. Naito, K. Nakajima, K. Nishiyama, T. J. O'Brien, R. Quimby, G. Sala, Y. Sano, E. M. Sion, A. F. Valeev, F. Watanabe, M. Watanabe, B. F. Williams, Z. Xu. 2016-07-27. M31N 2008-12a - the remarkable recurrent nova in M31: Pan-chromatic observations of the 2015 eruption. https://doi.org/10.3847/1538-4357%2F833%2F2%2F149

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