Electronic Telegram No. 2338 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION CBAT Director: Daniel W. E. Green; Room 209; Dept. of Earth and Planetary Sciences; Harvard University; 20 Oxford St.; Cambridge, MA 02138; U.S.A. e-mail: cbat@iau.org; cbatiau@eps.harvard.edu URL http://www.cfa.harvard.edu/iau/cbat.html NOVAE IN M81: M81N 2010-06a, M81N 2010-06b, M81N 2010-06c, M81N 2010-06d Kamil Hornoch, Astronomical Institute, Ondrejov; Daniel J. Hurley, University College, Cork; and Hannu Parviainen and Hans J. Deeg, Instituto de Astrofisica de Canarias and Universidad de La Laguna, report their discovery of two additional apparent novae in the galaxy M81 on a co-added 900-s narrow-band H_alpha CCD frame taken by Hurley, Parviainen, and Deeg with the 2.54-m Isaac Newton Telescope (+ WFC) at La Palma on June 14.893 UT. The new objects are visible on single 300-s images used for the co-added image. Additional narrow-band H_alpha CCD frames taken by Hurley, Parviainen, and Deeg, with the same instrumentation on June 15.920 confirmed the presence of both new objects, which are not present on numerous archive images from the 2.54-m Isaac Newton Telescope, the 4.2-m William Herschel Telescope, the 4-m Mayall telescope, the 8.2-m Subaru telescope, and the 8.1-m Gemini North telescope, down to limiting magnitudes as faint as Sloan r' = 22.4, R = 22.6, V = 22.5, and [H_alpha] = 21.6. M81N 2010-06c is located at R.A. = 9h55m31s.00, Decl. = +69o04'03".3 (equinox 2000.0), which is 11".6 west and 8".2 north of the center of M81. Available R-band and [H_alpha] magnitudes for M81N 2010-06c, measured by Hornoch: June 11.164 UT, [21.0 (P. Garnavich, C. Littlefield, N. Paul, and S. Bouzid, 1.83-m Vatican Advanced Technology Telescope + R filter); 14.893, [H_alpha] = 19.9 +/- 0.2 (Hurley, Parviainen, and Deeg, 2.54-m telescope); 15.920, [H_alpha] = 19.6 +/- 0.2 (Hurley, Parviainen, and Deeg). M81N 2010-06d is located at R.A. = 9h55m34s.96, Decl. = +69o03'51".5 (equinox 2000.0), which is 9".6 east and 3".6 south of the center of M81. Available magnitudes for M81N 2010-06d: June 11.164, [20.9 (Garnavich, Littlefield, Paul, and Bouzid, 1.83-m telescope + R filter); 14.893, [H_alpha] = 20.1 +/- 0.3 (Hurley, Parviainen, and Deeg); 15.920, [H_alpha] = 20.0 +/- 0.2 (Hurley, Parviainen, and Deeg). Julie Nantais and John Huchra, Harvard-Smithsonian Center for Astrophysics, examined the locations of the recently discovered novae M81N 2010-06a and M81N 2010-06b (as reported by Hornoch et al. on CBET 2332) in deep Hubble Space Telescope Advanced Camera for Surveys imaging in the bands B, V, and I. The Hubble images date between September 2004 and December 2006. No visible progenitors are found for these novae to magnitudes B about 25.7, V about 24.7, and I about 24.2. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2010 CBAT 2010 June 26 (CBET 2338) Daniel W. E. Green