2010CBET.2305....1H

Kamil Hornoch, Ondrejov Observatory, reports the discovery of an apparent nova in the galaxy M31 by M. Wolf, P. Hornochova, and himself on co-added 990-s and co-added 900-s R-band CCD frames taken with the 0.65-m telescope at Ondrejov during May 28.035-28.062 UT; the new object is visible on single images used for the co-added images, but is not present on numerous archival images taken at Lelekovice and Ondrejov back to 2002. M31N 2010-05a is located at R.A. = 0:42:35.88 ± 0s.03, Decl. = +41:16:37.7 ± 0".5 (equinox 2000.0), which is 95" west and 29" north of the center of M31. Available R-band magnitudes for M31N 2010-05a from various CCD images: 2010 Jan. 31.838, [21.2 (P. Kubanek, N. Morales, J. L. Ortiz, J. Gorosabel, and M. Jelinek, 1.23-m telescope at Calar Alto); Feb. 25.745, [20.1 (Hornoch, 0.65-m telescope at Ondrejov); Mar. 17.763, [19.9 (Hornoch, Wolf. and P. Zasche, 0.65-m telescope at Ondrejov); May 28.035, 17.6 ± 0.15 (Hornoch, Wolf, and Hornochova, 0.65-m telescope at Ondrejov); 28.049, 17.4 ± 0.2 (Hornoch, Wolf and Hornochova); 28.062, 17.4 ± 0.2 (Hornoch, Wolf and Hornochova); June 4.135, 17.11 ± 0.07 (Morales, Ortiz, Gorosabel, Kubanek, and Jelinek, 1.23-m telescope at Calar Alto).