A remarkable recurrent nova in M 31: The 2010 eruption recovered and evidence of a six-month period

TL;DR

This study confirms the 2010 eruption of the recurrent nova M31N 2008-12a, suggesting a possible six-month recurrence period, which makes it an even more rapid and exceptional Type Ia Supernova progenitor candidate.

Contribution

The paper provides evidence for the 2010 eruption and proposes a revised recurrence period of approximately six months for M31N 2008-12a, based on archival data and multi-wavelength analysis.

Findings

2010 eruption confirmed in archival images

Recurrence period possibly ~6 months

Next eruption predicted for late Sep 2015

Abstract

The Andromeda Galaxy recurrent nova M31N 2008-12a has been caught in eruption nine times. Six observed eruptions in the seven years from 2008 to 2014 suggested a duty cycle of ~1 year, which makes this the most rapidly recurring system known and the leading single-degenerate Type Ia Supernova progenitor candidate; but no 2010 eruption has been found so far. Here we present evidence supporting the recovery of the 2010 eruption, based on archival images taken at and around the time. We detect the 2010 eruption in a pair of images at 2010 Nov 20.52 UT, with a magnitude of m_R = 17.84 +/- 0.19. The sequence of seven eruptions shows significant indications of a duty cycle slightly shorter than one year, which makes successive eruptions occur progressively earlier in the year. We compared three archival X-ray detections with the well observed multi-wavelength light curve of the 2014 eruption to accurately constrain the time of their optical peaks. The results imply that M31N 2008-12a might have in fact a recurrence period of ~6 months (175 +/- 11 days), making it even more exceptional. If this is the case, then we predict that soon two eruptions per year will be observable. Furthermore, we predict the next eruption will occur around late Sep 2015. We encourage additional observations.