Independent Discovery of a Probable Nova in M31, AT 2026vdo

ATel #17914; K. Hornoch, H. Kucakova, K. Honkova (Ondrejov), A. W. Shafter (SDSU)
on 20 Jul 2026; 19:10 UT
Distributed as an Instant Email Notice Novae
Credential Certification: Allen W. Shafter (ashafter@sdsu.edu)

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We report the discovery of a probable nova found during our survey of the central region of M31. The object was discovered on a co-added 1320-s R-band CMOS frame taken on 2026 Jul. 19.957 UT with the 0.65-m telescope at Ondrejov. Subsequently, we found a prediscovery detection of the new object on a co-added R-band CMOS frame taken on 2026 Jul. 18.944 UT with the same instrumentation under poor sky conditions.

The object was independently discovered on Jul. 20.081 UT by R. Fidrich and T. Tordai and on Jul. 19.9993 UT by A. Valcheva et al. (ATel #17910).

The object has been designated by us as M31N 2026-07b (because previous reported probable nova in M31 AT2026uti was discovered on Jul. 13.803 UT as first M31 nova candidate reported in July and thus should be designated as 2026-07a) and is located at R.A. = 0h42m55s.96, Decl. = +41o17'31".6 (equinox 2000.0), which is 131.2" east and 83.1" north of the center of M31 (see link to discovery image below).

The following R-band magnitudes were obtained using the 0.65-m telescope at Ondrejov (D65):

 
  Date [UT]    |  Mag   | Err  | Filter  | Telescope 
 
2026-07-15.978 | >19.2  |      | R       | D65 
2026-07-18.944 |  18.9  | 0.25 | R       | D65 
2026-07-19.957 |  17.9  | 0.1  | 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