Extragalactic Nova Populations

TL;DR

This paper reviews nova rates across various galaxy types, finding consistent rates normalized by luminosity, and explores how stellar populations influence nova characteristics and recurrence in different galaxies.

Contribution

It provides new measurements of nova rates in Virgo ellipticals and analyzes how stellar populations affect nova properties and recurrence.

Findings

Nova rates are consistent across galaxy types when normalized by luminosity.

No correlation between nova rates and globular cluster frequency.

Younger stellar populations produce faster and more He/N novae.

Abstract

Nova rates have now been measured for more than a dozen galaxies spanning a wide range of Hubble types. When normalized to the infrared K-band luminosity of the galaxy, the luminosity-specific nova rates typically fall in the range of 1-3 novae per year per 10^10 solar luminosities in K, and do not vary significantly across the Hubble sequence. Preliminary nova rates are presented for three Virgo ellipticals (M49, M84, and M87) with differing globular cluster specific frequencies. No dependence of the luminosity-specific nova rate on globular cluster specific frequency was found. Photometric and spectroscopic observations of novae in the Local Group suggest that galaxies dominated by a younger stellar population (M33 and the LMC) are characterized by novae with a generally faster photometric evolution, and by a higher fraction of He/N novae compared with novae in M31. The recurrent nova population in the LMC appears to be higher than that seen in M31 and the Galaxy.