The Enigmatic Reccurent Nova: M31N 2017-01e

Novae are a class of cataclysmic variables with an accreting white dwarf primary and a secondary main-sequence/giant/sub-giant star. These systems go into outburst as a consequence of thermonuclear runaway on the surface of the white dwarf, ejecting the accreted material at high velocities and causing a sudden increase in the brightness of the system. If a system undergoes more than one nova eruption, it is classified as a recurrent nova, whereas classical novae are those observed to erupt only once. M31 hosts most known recurrent novae, including the fastest, M31N 2008-12a, which goes into outburst every year. The second fastest recurring nova M31N 2017-01e, also located in M31 has a recurrence period of approx. 2.5 years. Its position coincides with a bright blue (M_V~ -4.2, B-V~ -0.089, Massey et al. 2016) variable source showing a photometric modulation of 14.3 days (Vilardell et al. 2006). Additionally, the amplitude of its outburst is about four magnitudes, which is significantly smaller than the typical 8–10 magnitudes observed in most novae. We present here an analysis of the optical and UV data at quiescence as well as during the 2019 and 2024 outbursts. We detect a previously unreported soft X-ray emission following the 2019 outburst, most likely from the SSS phase. The analysis of high resolution optical data revealed two faint sources within 5 arcseconds of the nova location. We calculated the B-V colour of nova and the two sources as -0.14, -0.14 and -0.24, respectively. The unusually blue colour observed at quiescence deviates from typical B-V values for novae, which are ~0.36 for main-sequence companions, ~0.64 for subgiants, and ~1.5 for giants (Darnley et al. 2012). We perform SED analysis and propose plausible explanations for the nova's unique characteristics.