Discovery of a Probable Nova in M81 and Photometry of Three M81 Novae

ATel #7019; K. Hornoch (Astronomical Institute, Ondrejov, Czech Republic), R. Errmann (ING, La Palma, Spain and Astrophysical Institute and University Observatory, Jena, Germany), Ch. Carlisle (ING, La Palma, Spain and University of Sheffield, UK), O. Vaduvescu (ING, La Palma, Spain)
on 3 Feb 2015; 06:38 UT
Credential Certification: Allen W. Shafter (aws@nova.sdsu.edu)

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We report the discovery of a probable nova in M81 on a co-added 1600-s narrow-band H-alpha CCD image taken with the 2.5-m Isaac Newton Telescope (INT) + WFC at La Palma under ~1.6" seeing on 2015 Jan. 29.117 UT. The new object is easily visible on the co-added image (see the finding chart linked below) and is present at H-alpha = 20.6 ± 0.25 mag on a prediscovery image taken with the INT on Jan. 15.126 UT (see ATel #6968), but is not present on numerous narrow-band H-alpha archival images from the INT down to limiting magnitude as faint as H-alpha = 22.1. On Jan. 29.120 UT we also obtained Sloan r'-band images which helped us to classify the object.

The new object designated PNV J09551301+6904206 = M81N 2015-01b (tentative designation) is located at R.A. = 9h55m13s.01, Decl. = +69o04'20".6 (equinox 2000.0), which is 108.0" west and 25.5" north of the center of M81.

The photometry obtained with the INT + WFC for the PNV J09551301+6904206 and for M81 novae PNV J09550693+6902588 (ATel #6968), PNV J09554328+6902033 (ATel #6599 and #6678), and PNV J09555775+6902126 (ATel #6552 and #6678) is summarized in the following table:

 
                         2015 01 29.117     2015 01 29.120 
 
       Object             H-alpha mag        Sloan r' mag 
 
PNV J09551301+6904206    21.1 +/- 0.3          > 23.2 
PNV J09550693+6902588    21.2 +/- 0.25      23.7 +/- 0.5 
PNV J09554328+6902033    21.3 +/- 0.3          > 22.6 
PNV J09555775+6902126    20.8 +/- 0.2       21.8 +/- 0.15 

Strong H-alpha emission together with relative faintness in Sloan the r'-band (both observed in the INT data) supports the classification of the PNV J09551301+6904206 as a nova caught well after outburst, which is consistent with its relatively faint magnitude and the 0.5 mag fade observed over the last two weeks.

This work is based on observations made with the Isaac Newton Telescope operated on the island of La Palma by the ING in the Spanish Observatorio del Roque de los Muchachos.

Finding Chart