Recurrent Novae: A Masquerade

Abstract

Due to low discovery efficiencies, there must be some number of classical novae (CNe) that are in fact recurrent novae (RNe) for which only one eruption has so far been observed. We collect all available information on the light curves, spectra, and quiescent characteristics of a time-limited sample of 237 Galactic CNe and the ten known Galactic RNe, and identify seven characteristics that are indicative of a short recurrence time: (1) outburst amplitude smaller than 14.5 − 4.5 × log(t 3 ), (2) orbital period >0.6 days, (3) infrared colors of J − H > 0.7 mag and H − K > 0.1 mag, (4) FWHM of Hα > 2000 km s −1 , (5) high excitation lines, such as Fe X or He II, near peak, (6) eruption light curves with a plateau, and (7) white dwarf mass greater than 1.2M . We use these characteristics to identify good RN candidates from among the list of known CNe and to draw conclusions about the population of Galactic RNe, specifically related to whether there are enough RNe to provide the observed Type Ia supernova rate, as RNe are good candidate progenitors. We find that 25% ± 10% of CNe are likely RNe with only one eruption observed so far, and that RNe could perhaps provide up to one half of the Type Ia supernovae. and collects information on novae that were not included in the original paper but were of interest to other conference attendees.