2010CBET.2610....1H

Kamil Hornoch, Astronomical Institute, Ondrejov, reports measured positions for the apparent nova in M31 that was designated M31N 2010-12c (cf. CBETs 2594, 2597), from all available images taken with the 0.65-m telescope at Ondrejov (four positions), which give the following average astrometry: R.A. = 0:42:56.668 ± 0s.005, Decl. = +41:17:21.23 ± 0".13 (equinox 2000.0). An average of the position end figures for M31N 2010-01a (cf. CBETs 2124, 2127, 2136, 2187, 2594, 2597), measured from four archival images taken with the 0.65-m telescope at Ondrejov, 1.23-m telescope at Calar Alto, and 2.4-m Hiltner telescope at MDM yield 56s.728 ± 0s.005, 21".03 ± 0".12. Very similar results gave also averages for other published positions for the two objects: 56s.660 ± 0s.015 vs. 56s.735 ± 0s.023, and 21".30 ± 0".13 vs. 21".10 ± 0".20 for R.A. and Decl. end figures, respectively. Although it is very unlikely that two different novae in M31 will erupt within 0".8 in only 11 months, the precise positions clearly show that M31N 2010-01a and M31N 2010-12c are two different objects. Hornoch adds that comparison of high-quality images of M31N 2010-01a taken by J. Prieto and R. Khan on 2010 Jan. 14.086 UT with the 2.4-m Hiltner telescope (+ RETROCAM + Sloan r' filter) at MDM observatory and of M31N 2010-12c taken by Khan on 2010 Dec. 26.212 with the same telescope (+ OSMOS + R filter) clearly confirms the different locations of the two objects. The separation of centroids of the two objects is 2.5 pixels (pixel size 0".273). Additional R-band magnitudes of M31N 2010-12c: Dec. 16.846, 16.62 ± 0.06 (Hornoch, 0.65-m telescope at Ondrejov); 18.896, 17.18 ± 0.09 (Hornoch and P. Hornochova, 0.65-m telescope at Ondrejov); 24.185, 18.6 ± 0.1 (Khan, 2.4-m Hiltner telescope); 26.190, 18.8 ± 0.1 (Khan); 26.212, 18.86 ± 0.07 (Khan).