Liverpool Telescope SPRAT spectrum of PNV J01350197+3043202: a potential recurrence of M33N 2021-08a
ATel #17432; M. J.Darnley (LJMU), Jingyuan Zhao, Ziyang Mai, Jianlin Xu, Hualin Li, Mi Zhang, Wenjie Zhou, Guoyou Sun, Jiangao Ruan, Xing Gao (Xingming Observatory)
on 4 Oct 2025; 10:14 UT
Credential Certification: Matt Darnley (matt_darnley@icloud.com)
Subjects: Optical, Nova, Transient
Referred to by ATel #: 17435
A potential nova was discovered in M33 on 2025 Oct 02.65: http://www.cbat.eps.harvard.edu/unconf/followups/J01350197+3043202.html
Due to its spatial proximity, this has been identified as a potential recurrence of M33N 2021-08a (AT 2021wfc).
We obtained a single 600s spectrum of PNV J01350197+3043202 with the SPRAT instrument on the Liverpool Telescope on 2025 Oct 03.9758 (mid-point).
Although the signal-to-noise of the source was low in the spectrum, there is a clear detection of broad and double peaked Hα emission.
The Hα emission has a half-width of around 4800 km/s. The separation of the two peaks is around 5000 km/s.
There is also evidence of a N II, or possibly He I, emission line at around 5010 Angstroms.
Although there is negligible evidence for Hβ, there is double peaked emission around Hγ also showing a ~5000 km/s separation between the peaks.
As such, we conclude that the most likely source of this new transient is a nova eruption in M33.
If the spatial coincidence with M33N 2021-08a is confirmed, then this suggests a nova with a recurrence period of four years, or shorter: another rapid-recurrent nova.
This would, we believe, be the first recurrent nova confirmed in M33.
