Novae as a Class of Transient X-ray Sources

TL;DR

This paper explores classical and recurrent novae as potential sources of faint X-ray transients in the Galactic Center, suggesting X-ray monitoring could reveal more about nova populations in obscured regions.

Contribution

It demonstrates that classical novae are likely responsible for faint X-ray transients and proposes X-ray monitoring as an effective method to detect and study them in the Galactic Center.

Findings

Classical novae are consistent with faint X-ray transients in luminosity and duration.

Estimated nova rate in the Galactic Center is about 0.1 per year.

X-ray monitoring can uncover hidden nova populations in obscured regions.

Abstract

Motivated by the recently discovered class of faint (10^34-10^35 ergs/s) X-ray transients in the Galactic Center region, we investigate the 2-10 keV properties of classical and recurrent novae. Existing data are consistent with the idea that all classical novae are transient X-ray sources with durations of months to years and peak luminosities in the 10^34-10^35 ergs/s range. This makes classical novae a viable candidate class for the faint Galactic Center transients. We estimate the rate of classical novae within a 15 arcmin radius region centered on the Galactic Center (roughly the field of view of XMM-Newton observations centered on Sgr A*) to be ~0.1 per year. Therefore, it is plausible that some of the Galactic Center transients that have been announced to date are unrecognized classical novae. The continuing monitoring of the Galactic Center region carried out by Chandra and XMM-Newton may therefore provide a new method to detect classical novae in this crowded and obscured region, where optical surveys are not, and can never hope to be, effective. Therefore, X-ray monitoring may provide the best means of testing the completeness of the current understanding of the nova populations.