Independent Discovery of a Probable Nova in M81

ATel #17064; K. Hornoch (Ondrejov), H. Kucakova (Charles University), A. W. Shafter (SDSU)
on 5 Mar 2025; 20:11 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 in M81 on a co-added 5400-s unfiltered CCD frame taken on 2025 Mar. 5.160 UT with the 0.65-m telescope at Ondrejov. The new object is visible also on a prediscovery co-added CCD frame taken on Mar. 4.063 UT with the same instrumentation under poor conditions (dense cirrus clouds).

The object was independently discovered on Mar. 4.869 UT by F. Castellani et al. and designated as PNV J09554343+6905154 = AT 2025dih.

The object designated by us as M81N 2025-03a is located at R.A. = 9h55m43s.64, Decl. = +69o05'16".5 (equinox 2000.0), which is 56.1" east and 81.4" north 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 
 
2025-03-02.997 | >21.4  |      | C       | OND 
2025-03-04.063 |  20.2  | 0.3  | C       | OND 
2025-03-05.160 |  19.8  | 0.15 | 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