Discovery of a Probable Nova in M81

ATel #5015; K. Hornoch (Astronomical Institute, Ondrejov, Czech Republic), N. Morales (IAA/CSIC, Spain), J. Gorosabel (UPV/EHU and IAA/CSIC, Spain), P. Kubanek (Institute of Physics ASCR, Czech Republic)
on 26 Apr 2013; 17:40 UT
Credential Certification: Allen W. Shafter (aws@nova.sdsu.edu)

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We report the discovery of a probable nova in the M81 galaxy on co-added 1800-s R-band and 1800-s I-band CCD frames taken with the 1.23-m telescope at Calar Alto on Apr. 16.968 and 17.002 UT, respectively. The new object is visible on individual 180-s images and well visible on the co-added image (see link to the R-band discovery image below), but is not present on numerous archival images down to limiting magnitudes as faint as Sloan r' = 23.2, R = 23.4, I = 22.7, and H-alpha = 22.6. The object is also present on prediscovery images taken with the 2.5-m Isaac Newton Telescope (INT) + WFC at La Palma on Apr. 5.946 - 5.949 UT (ATel #4968).

The new object designated PNV J09545056+6900364 is located at R.A. = 9h54m50s.56, Decl. = +69o00'36".4 (equinox 2000.0), which is 228.7" west and 198.7" south of the center of M81.

The following magnitudes were obtained:

2013 Feb. 25.146 UT, [22.4 (2.5-m INT at La Palma, Sloan r', ATel #4844); Apr. 5.946, H-alpha = 22.2 +/- 0.3 (2.5-m INT at La Palma); 5.946, R = 22.7 +/- 0.3 (2.5-m INT at La Palma); 5.949, I = 22.3 +/- 0.3 (2.5-m INT at La Palma); 16.968, R = 21.15 +/- 0.1 (1.23-m at Calar Alto); 17.002, I = 21.2 +/- 0.2 (1.23-m at Calar Alto); 24.883, 22.3 +/- 0.4 (0.65-m at Ondrejov, unfiltered, R-band magnitudes used from comparison stars).

Rather weak H-alpha emission (with respect to evolved novae) on the prediscovery epoch is consistent with early stage of a nova outburst. Also, its color evolution is consistent with evolving nova phenomenon.

In addition, we measured magnitudes and precise positions of PNV J09554503+6902369 (ATel #4980) using the 1.23-m Calar Alto images: Apr. 16.968, R = 20.44 +/- 0.1; 17.002, I = 20.4 +/- 0.15. R.A. = 9h55m45s.11, Decl. = +69o02'36".2 (equinox 2000.0), which is 64.0" east and 78.9" south of the center of M81.

We thank H. Kucakova for getting M81 images at Ondrejov. This work is based (in part) on observations made with the Isaac Newton Telescope (INT) operated on the island of La Palma by the Isaac Newton Group (ING) in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias (IAC).

Finding chart