V5852 Sgr: An Unusual Nova Possibly Associated with the Sagittarius Stream

TL;DR

This paper presents a detailed study of the unusual nova V5852 Sgr, which exhibits mixed features of different nova classes and may be associated with the Sagittarius stream, making it potentially the first nova detected from a dwarf spheroidal galaxy.

Contribution

It provides the first spectroscopic and photometric analysis of V5852 Sgr, suggesting its possible association with the Sagittarius stream and highlighting its unique spectral and light curve features.

Findings

Nova shows mixed spectral features from different classes.

Possible association with the Sagittarius dwarf spheroidal galaxy.

First nova potentially detected from a dwarf spheroidal galaxy.

Abstract

We report spectroscopic and photometric follow-up of the peculiar nova V5852~Sgr (discovered as OGLE-2015-NOVA-01), which exhibits a combination of features from different nova classes. The photometry shows a flat-topped light curve with quasi-periodic oscillations, then a smooth decline followed by two fainter recoveries in brightness. Spectroscopy with the Southern African Large Telescope shows first a classical nova with an Fe II or Fe IIb spectral type. In the later spectrum, broad emissions from helium, nitrogen and oxygen are prominent and the iron has faded which could be an indication to the start of the nebular phase. The line widths suggest ejection velocities around $1000\,{\rm km\,s^{-1}}$. The nova is in the direction of the Galactic bulge and is heavily reddened by an uncertain amount. The $V$ magnitude 16 days after maximum enables a distance to be estimated and this suggests that the nova may be in the extreme trailing stream of the Sagittarius dwarf spheroidal galaxy. If so it is the first nova to be detected from that, or from any dwarf spheroidal galaxy. Given the uncertainty of the method and the unusual light curve we cannot rule out the possibility that it is in the bulge or even the Galactic disk behind the bulge.