Independent Discovery of a Probable Nova in M31

ATel #16966; K. Hornoch (Astronomical Institute, Ondrejov, Czech Republic), A. W. Shafter (SDSU), H. Kucakova (Charles University, Prague, Czech Republic)
on 5 Jan 2025; 21:22 UT
Distributed as an Instant Email Notice Novae
Credential Certification: Allen W. Shafter (ashafter@sdsu.edu)

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We report the independent discovery of a probable nova found during our survey of the central region of M31. The object was discovered on a co-added 1260-s R-band CCD frame taken on 2025 Jan. 4.133 UT with the 40-in reflector at SDSU's Mount Laguna Observatory (MLO) under poor sky conditions. Due to faintness of the nova candidate on the discovery image we took a confirmation co-added 8820-s R-band CCD frame on Jan. 4.943 UT with the 0.65-m telescope at Ondrejov which were also under suboptimal sky conditions (cirrus clouds). Subsequently, we found that the probable nova was also visible on a prediscovery co-added 1800-s R-band CCD frame taken on Jan. 3.102 UT with the MLO 40-in reflector.

The object was independently discovered on Jan. 4.165 UT by the ZTF and designated as AT 2025bm.

The object has been designated by us as M31N 2025-01a and is located at R.A. = 0h42m49s.77, Decl. = +41o16'47".4 (equinox 2000.0), which is 61.4" east and 38.9" north of the center of M31 (see link to discovery image below).

The following R-band magnitudes were obtained using the 40-in reflector at SDSU's Mount Laguna Observatory (MLO) and the 0.65-m telescope at Ondrejov (D65):

 
  Date [UT]    |  Mag   | Err  | Filter  | Telescope 
 
2025-01-02.106 | >19.8  |      | R       | MLO 
2025-01-03.102 |  19.5  | 0.2  | R       | MLO 
2025-01-04.133 |  18.9  | 0.2  | R       | MLO 
2025-01-04.943 |  18.1  | 0.15 | R       | D65 
 

As with all extragalactic novae, follow-up spectroscopic and photometric observations to confirm the nova's nature and determine its spectroscopic class and rate of decline (speed class) are encouraged.

Discovery image