Discovery of Two Apparent Novae in M81

ATel #5109; K. Hornoch (Astronomical Institute, Ondrejov, Czech Republic), J. McCormac, O. Vaduvescu (ING, La Palma, Spain)
on 5 Jun 2013; 22:02 UT
Credential Certification: Allen W. Shafter (aws@nova.sdsu.edu)

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We report the discovery of two apparent novae in the M81 galaxy 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 in ~1.5" seeing on 2013 June 3.905 UT. The new objects are visible on individual 400-s frames and well visible on the co-added image (see the finding chart linked below), but are not present on numerous narrow-band H-alpha archival images from the INT down to a limiting magnitude as faint as H-alpha = 22.7.

Designations, positions, and offsets of the new objects from the center of M81 are summarized in the following table:

 
 
  TOCP designation    CBAT designation  R.A. (J2000)  Dec. (J2000)  Offset R.A.  Offset Dec. 
 
PNV J09553291+6905261  M81N 2013-06a?   09 55 32.91   +69 05 26.1      1.4" W      91.0" N 
PNV J09552524+6905322  M81N 2013-06b?   09 55 25.24   +69 05 32.2     42.5" W      97.1" N 
 

The photometry of the new objects, as well as of PNV J09553917+6902390 (ATel #4894 and #4968) obtained with the INT + WFC on June 3.901 and 3.905 UT (I-band and H-alpha, respectively), is summarized here:

 
 
  TOCP designation      CBAT designation    H-alpha mag         I mag 
 
PNV J09553291+6905261    M81N 2013-06a?    20.2 +/- 0.15    21.6 +/- 0.3 
PNV J09552524+6905322    M81N 2013-06b?    19.9 +/- 0.1     19.9 +/- 0.15 
PNV J09553917+6902390    M81N 2013-03a?    20.9 +/- 0.25       > 21.9 

The PNV J09553291+6905261 is visible also on a co-added prediscovery 1440-s unfiltered CCD image taken by K. Hornoch on May 15.863 UT with the 0.65-m telescope at Ondrejov at 20.1 +/- 0.25 mag (R-band magnitudes used from comparison stars), but is not visible (nor is the PNV J09552524+6905322) on images taken with the 1.23-m telescope at Calar Alto (ATel #5015) down to R = 22.3 mag and I = 21.4 mag on Apr. 16.968 and 17.002 UT, respectively. Current strong H-alpha emission together with the relative faintness of the PNV J09553291+6905261 in the I-band, supported by the prediscovery detection, suggests the object has evolved well beyond peak brightness, while the identical H-alpha and I-band magnitudes of the PNV J09552524+6905322 are consistent with a nova observed near maximum light.

This work is based 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