2010CBET.2411....1H

Kamil Hornoch, Astronomical Institute, Ondrejov; and Jesus M. Corral- Santana and Jorge Casares, Instituto de Astrofisica de Canarias and Universidad de La Laguna, report their discovery of a probable nova in the galaxy M31 on co-added 720-s narrow-band H_alpha and 360-s Sloan r' CCD frames taken by Corral-Santana and Casares with the 2.54-m Isaac Newton Telescope (+ WFC) at La Palma on July 10.210 and 10.200 UT, respectively. The new object, designated M31N 2010-07b, is visible on single images used for the co-added frame and is faintly visible also on many pre-discovery co-added frames taken during June, but it is not present on numerous archival images taken at Ondrejov and other observatories. M31N 2010-07b is located at R.A. = 0:43:07.50, Decl. = +41:17:58.6 (equinox 2000.0), which is 261" east and 110" north of the center of M31. Available R-band magnitudes for M31N 2010-07b, measured by Hornoch: 2005 June 11.211 UT, [22.0 (D. Mackey, 2.54-m Isaac Newton Telescope + narrow-band H_alpha filter); Oct. 8.369, [22.9 (P. Garnavich and C. Kennedy, 1.83-m Vatican Advanced Technology Telescope + R filter); 2010 Jan. 31.784, [21.9 (P. Kubanek, N. Morales, J. L. Ortiz, J. Gorosabel, and M. Jelinek, 1.23-m telescope at Calar Alto + R filter); June 4.135, R = 20.7 ± 0.2 (Morales, Ortiz, Gorosabel, Kubanek, and Jelinek, 1.23-m telescope at Calar Alto); 9.459, R = 20.9 ± 0.3 (Garnavich, C. Littlefield, N. Paul, and S. Bouzid, 1.83-m Vatican Advanced Technology Telescope); 17.152, R = 20.8 ± 0.2 (Kubanek, Gorosabel, O. Lara Gil, and Jelinek, 1.23-m telescope at Calar Alto); July 10.200, Sloan r' = 20.9 ± 0.2 (Corral-Santana and Casares, 2.54-m Isaac Newton Telescope); 10.210, [H_alpha] = 18.8 ± 0.15 (Corral-Santana and Casares); 11.210, Sloan r' = 20.9 ± 0.2 (Corral-Santana and Casares); 19.186, Sloan r' = 20.8 ± 0.2 (D. Pinfield, B. Sipocz, and G. Kovacs, 2.54-m Isaac Newton Telescope); 19.191, [H_alpha] = 18.7 ± 0.15 (Pinfield, Sipocz, and Kovacs); 20.069, [H_alpha] = 18.8 ± 0.15 (Gorosabel, Lara Gil, Jelinek, Kubanek, and P. Martorell, 1.23-m telescope at Calar Alto). When comparing measurements in Sloan r' and H_alpha, they notice strong excess in H_alpha emission, suggesting that the object is a nova well after the outburst.