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

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