M31N 2022-09a is the fourth reported eruption of the recurrent nova M31N 1926-07c

ATel #15608; K. Hornoch (Astronomical Institute, Ondrejov, Czech Republic), A. W. Shafter (SDSU), P. Zasche (Astronomical Institute, Charles university, Czech Republic) and H. Kucakova (Ondrejov)
on 10 Sep 2022; 19:36 UT
Distributed as an Instant Email Notice Novae
Credential Certification: Allen W. Shafter (ashafter@sdsu.edu)

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K. Hornoch and H. Kucakova have reported a discovery of a probable nova in M31 designated M31N 2022-09a (see ATel #15599). An independent discovery of the new object designated as PNV J00425234+4116130 was reported by J. Zhao here, who also mentioned that the object is possible recurrence of M31N 1926-07c.

A careful registration of our co-added 1200-s R-band CCD image taken on 2022 Sep. 8.951 UT using the 0.65-m telescope at Ondrejov with an image of the 2008 eruption of the known recurrent nova M31N 1926-07c = 1997-10f = 2008-08b published in Shafter et al. (2015, ApJS, 216, 34) reveals that the transients are spatially coincident to better than 1" (see the link to the comparison image below). Timings of the four outbursts indicate possible recurrence time of ~3.5 years, assuming some recent eruptions have been missed (this would not necessarily be surprising since several recent eruptions would likely have taken place when M31 was near conjunction with the sun and virtually unobservable).

We also report additional R-band magnitudes of the recent eruption obtained using the 0.65-m telescope at Ondrejov:

2022 Aug. 8.808 UT, 17.8 ± 0.15; 9.093, 17.7 ± 0.1.

We conclude that M31N 2022-09a is indeed the fourth observed eruption of the recurrent nova M31N 1926-07c.

Spectroscopic classification and additional photometric observations to better characterize the light curve of M31N 2022-09a are encouraged.

Comparison Image: M31N 2008-08b (black); M31N 2022-09a (white)