Abstract

Classical novae and supernovae were long thought to be completely separate astrophysical phenomena. This is no longer true; most type Ia supernovae (SNIa), the “standardizable candles” that led to the discovery of the dark energy, are now understood to have had symbiotic nova progenitors. Symbiotic novae consist of a red giant and a rapidly accreting, frequently erupting white dwarf. Some of the offspring of these binaries are close double white dwarfs, which are equally viable SNIa progenitors. Understanding the evolution of these binaries over a Hubble time is essential to a robust calibration of the crucial standard candles that they produce.

I’ll review the current state of knowledge of the short and long-term temporal evolution of the white dwarfs in novae, and predictions about how these can lead to SNIa. A test of a key prediction of the theory is underway. In 2017 the Hubble Space Telescope is imaging the giant elliptical galaxy M87 53 times – every 5 days over 9 months – in a search for recurring “ultraviolet flashers” in M87 . These are the symbiotic novae predicted to produce SNIa. I’ll present early results from this program, which should finally quantify the fractions of SNIa progenitors containing one and two white dwarfs at redshift zero. This will be a strong constraint on all evolutionary models of the binaries which produce SNIa.