Discovery of Two Probable Novae in M31

ATel #15845; K. Hornoch, H. Kucakova (Astronomical Institute, Ondrejov, Czech Republic); P. Cagas (BSObservatory, Zlin, Czech Republic); A. W. Shafter, J. C. Horst (SDSU)
on 4 Jan 2023; 20:18 UT
Distributed as an Instant Email Notice Novae
Credential Certification: Allen W. Shafter (ashafter@sdsu.edu)

Tweet

We report the discovery of two probable novae in M31. The first nova candidate was independently discovered during our survey of the central region of M31 on a co-added 810-s CCD frame taken on 2023 Jan. 3.881 UT with the 0.65-m telescope at Ondrejov.

The object was independently discovered on Jan. 3.576 UT by M. Zhang and X. Gao and designated as PNV J00423797+4117130 = AT 2023U, and by I. Perez-Fournon et al. on Jan. 3.897 UT (see ATel #15842) and designated as M31N 2023-01a.

The object is located at R.A. = 0h42m37s.95, Decl. = +41o17'13".4 (equinox 2000.0), which is 71.9" west and 64.9" north of the center of M31 ( see discovery image ).

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

 
  Date [UT]    |  Mag   | Err  | Filter  | Telescope 
 
2023-01-01.829 | <20.4  |      | R       | D65 
2023-01-03.881 |  17.6  | 0.15 | R       | D65 
2023-01-03.890 |  17.6  | 0.15 | R       | D65 
 

During examination of our archival images (searching for potential previous eruptions of the current probable nova with negative result) we discovered a previously unreported nova candidate on a co-added 4200-s CCD frame taken on 2015 Dec. 10.857 UT at the BSObservatory with the 0.30-m telescope + G4-16000 CCD camera through a 7 nm wide Hα filter. The object is also faintly visible on co-added 810-s and 900-s R-band CCD frames taken on 2015 Dec. 5.719 and 7.717 UT, respectively, with the 0.65-m telescope at Ondrejov.

The object designated M31N 2015-12d is located at R.A. = 0h42m43s.91, Decl. = +41o16'02".2 (equinox 2000.0), which is only 4.7" west and 6.3" south of the center of M31 ( see discovery image ).

The following magnitudes were obtained using the 0.30-m telescope at BSObservatory (BSO) and the 0.65-m telescope at Ondrejov (D65):

 
  Date [UT]    |  Mag   | Err  | Filter  | Telescope 
 
2015-12-05.719 |  16.8  | 0.8  | R       | D65 
2015-12-07.717 |  17.2  | 0.9  | R       | D65 
2015-12-10.857 |  15.3  | 0.4  | Ha      | BSO 
 

As with all extragalactic novae, follow-up spectroscopic and photometric observations to confirm the M31N 2023-01a = PNV J00423797+4117130 = AT 2023U nature and determine its spectroscopic class and rate of decline (speed class) are encouraged.