Exploring the archives: A search for novae in UVIT snapshots of M31

TL;DR

This paper presents the first UV catalog of novae in M31 using archival AstroSat UVIT data, revealing their properties in quiescence and outburst phases, and highlighting the importance of UV surveys for nova studies.

Contribution

It introduces a novel UV catalog of M31 novae from archival data and analyzes their UV properties during different phases, including pre-eruption dips.

Findings

42 novae detected in UVIT images

15 novae observed in multiple filters

Detection of pre-eruption dips in some light curves

Abstract

Extensive multi-wavelength studies of novae have been carried out in our galaxy and in M31 for decades. However, UV studies of extragalactic novae are limited, especially those in quiescence. For the first time, we present a UV catalog of novae in M31 using the archival AstroSat UVIT imaging data. We used two image subtraction techniques to retrieve objects located deep into the M31 central region. We have found 42 novae in total in the UVIT images, 15 of which have been detected in multiple filters in FUV and NUV. The novae detected at quiescence show signatures of accretion disk from their UV spectral energy distributions, whereas those in the outburst phase show signatures of pseudo-photosphere. A few novae were also detected in multiple epochs. Some show a near-constant FUV magnitude at quiescence, while others caught near the outburst reveal pre-eruption dips in their light curves. We conclude with a discussion on the significance of UV surveys in illuminating theoretical predictions for novae systems, including detecting the elusive early UV flash.