Independent Discovery of a Second Probable Nova in M81

ATel #17066; K. Hornoch (Ondrejov), H. Kucakova (Charles University), A. W. Shafter (SDSU)
on 6 Mar 2025; 22:58 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 another probable nova in M81 on a co-added 3600-s unfiltered CCD frame taken on 2025 Mar. 6.138 UT with the 0.65-m telescope at Ondrejov. Additionally, we found the new object visible also on a prediscovery co-added CCD frame taken on Mar. 5.160 UT with the same instrumentation. Since the new object is laying on top of a brighter spot in the M81 background it was missed during initial search of the 5.160 UT frame (see ATel #17064), also due to its intrinsic faintness at that time.

The object was independently discovered on Mar. 5.827 UT by F. Castellani et al. and designated as PNV J09551261+6902462 = AT 2025dkp.

The object designated by us as M81N 2025-03b is located at R.A. = 9h55m12s.69, Decl. = +69o02'46".3 (equinox 2000.0), which is 109.8" west and 68.8" south of the center of M81 (see link to discovery image below).

Here we list the observing dates and corresponding photometry:

 
  Date [UT]    |  Mag   | Err  | Filter  | Telescope 
 
2025-03-04.063 | >21.0  |      | C       | OND 
2025-03-05.160 |  20.9  | 0.25 | C       | OND 
2025-03-06.138 |  19.2  | 0.1  | C       | OND 
 

As with all extragalactic novae, follow-up spectroscopic and photometric observations to determine the nova's spectroscopic class and rate of decline (speed class) are encouraged. The OND 0.65-m is a reflecting telescope at the Ondrejov observatory operated jointly by the Astronomical Institute of ASCR and the Astronomical Institute of the Charles University of Prague, Czech Republic. It uses a Moravian Instruments G2-3200 MkII CCD camera (with a Kodak KAF-3200ME sensor and standard BVRI photometric filters) mounted at the prime focus. The unfiltered OND photometry was calibrated against R-band comparison stars from Perelmuter & Racine (1995).

Discovery image