The Rate and Spatial Distribution of Novae in M31 as Determined by a Twenty-Year Survey

TL;DR

This twenty-year survey of M31 identified 262 novae, revealing their spatial distribution and estimating a nova rate of approximately 40 per year, which is lower than previous estimates and informs understanding of nova populations in galaxies.

Contribution

The study provides the first long-term, spatially-complete nova rate measurement in M31, refining the galaxy's nova frequency and distribution using extensive observational data.

Findings

Nova rate in M31 is approximately 40 per year.

Novae distribution follows the bulge light of M31.

Estimated nova rate for the Milky Way is about 28 per year.

Abstract

A long-term (1995-2016) survey for novae in the nearby Andromeda galaxy (M31) was conducted as part of the Research-Based Science Education initiative. During the course of the survey 180 nights of observation were completed at Kitt Peak, Arizona. A total of 262 novae were either discovered or confirmed, 40 of which have not been previously reported. Of these, 203 novae form a spatially-complete sample detected by the KPNO/WIYN 0.9-m telescope within a $20'\times20'$ field centered on the nucleus of M31. An additional 50 novae are part of a spatially-complete sample detected by the KPNO 4-m telescope within a larger $36'\times36'$ field. Consistent with previous studies, it is found that the spatial distribution of novae in both surveys follows the bulge light of M31 somewhat more closely than the overall background light of the galaxy. After correcting for the limiting magnitude and the spatial and temporal coverage of the surveys, a final nova rate in M31 is found to be $R=40^{+5}_{-4}$ yr$^{-1}$, which is considerably lower than recent estimates. When normalized to the $K$-band luminosity of M31, this value yields a luminosity-specific nova rate, $\nu_K = 3.3\pm0.4$ yr$^{-1} [10^{10} L_{\odot,K}]^{-1}$. By scaling the M31 nova rate using the relative infrared luminosities of M31 and our Galaxy, a nova rate of $R_\mathrm{G}=28^{+5}_{-4}$ is found for the Milky Way.