Electronic Telegram No. 2500 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION CBAT Director: Daniel W. E. Green; Hoffman Lab 209; Harvard University; 20 Oxford St.; Cambridge, MA 02138; U.S.A. e-mail: cbatiau@eps.harvard.edu (alternate cbat@iau.org) URL http://www.cbat.eps.harvard.edu/index.html Prepared using the Tamkin Foundation Computer Network APPARENT NOVA IN M31: M31N 2010-10c Jiangao Ruan, Fangchenggang, Guangxi, China; and Xing Gao, Urumqi, Xinjiang, China, report the discovery of a possible nova (mag approximately 17.8) on several 60-s unfiltered CCD survey images (limiting mag about 19.0) taken by Xing Gao in the course of the Xingming Observatory Sky Survey around Oct. 13.5566 UT using a Celestron C14 Schmidt-Cassegrain telescope at Mt. Nanshan. The new object, designated M31N 2010-10c, is located at R.A. = 0h44m26s.6, Decl. = +41d31'13".4 (equinox 2000.0). Koichi Nishiyama, Kurume, Japan; and Fujio Kabashima, Miyaki, Japan, report their independent discovery of M31N 2010-10c at mag 17.0 on nine 40-s unfiltered CCD frames (limiting magnitude 19.9) taken around Oct. 15.574 UT using a Meade 200R 0.40-m f/9.8 reflector (+ SBIG STL1001E camera), providing position end figures 26s.55, 13".8 (offset 1153" east and 905" north from the center of the galaxy M31). Nishiyama and Kabashima note that a star in the HST/ACS VI data of M31 globular clusters has position end figures 26s.56, 13."8 and magnitudes V = 26.102, I = 24.499. Another independent discovery of M31N 2010-10c was made by Koichi Itagaki (Teppo-cho, Yamagata, Japan; forwarded by S. Nakano, Sumoto), who reported it at mag 17.4 on unfiltered CCD frames (limiting mag 19.5) taken on Oct. 16.399 using a 0.60-m f/5.7 reflector, providing position end figures 26s.56, 13".8; he has posted an image of the new object at the following website URL: http://www.k-itagaki.jp/images/31-pn-16.jpg. T. Yusa, Osaki, Japan, writes that (following a request from Kabashima and Nishiyama), he found M31N 2010-10c at mag 17.5 on Oct. 16.396 on an unfiltered CCD exposure (limiting mag 19.0) taken with a 0.30-m f/7 Cassegrain telescope (+ SBIG STL-1001E camera), yielding position end figures 26s.54, 13".2. Yusa has posted an image of M31N 2010-10c at website URL http://space.geocities.jp/yusastar77/PNinM31_101016.htm. Additional magnitudes for M31N 2010-10c, unfiltered unless otherwise noted: 1986 Nov. 27, [20.8 (Digitized Sky Survey, red image; via Ruan and Gao); 1986 Nov. 27, [18.4 (DSS, red image; via Nishiyama and Kabashima); 1993 Oct. 21, 18.1 (DSS, infrared image; via Nishiyama and Kabashima); 2010 Sept. 25.576, [19.5 (Itagaki); Oct. 9.600, [19.7 (Nishiyama and Kabashima); 10.635, [19.9 (Nishiyama and Kabashima); 11.555, [19.0 (Ruan and Gao); 12.6254, [19.0 (Ruan and Gao); 13.515, [20.5 (Itagaki); 13.596, 17.5 (Ruan and Gao); 14.583, V = 17.0 (Ruan and Gao); 16.626, 17.6 (Nishiyama and Kabashima). NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2010 CBAT 2010 October 16 (CBET 2500) Daniel W. E. Green