Discovery of Two Novae in M81

ATel #4129; K. Hornoch (Astronomical Institute, Ondrejov, Czech Republic), O. Vaduvescu (ING & IAC, La Palma, Spain), C. Zurita (IAC, La Palma, Spain), L. Patrick (ING, La Palma, Spain & University of Sheffield, UK), H. Ledo (ING, La Palma, Spain & CAR, U. of Hertfordshire, UK), R. Karjalainen (ING, La Palma, Spain)
on 25 May 2012; 23:57 UT
Credential Certification: Allen W. Shafter (aws@nova.sdsu.edu)

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We report the discovery of two novae 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 ~0.8" seeing on May 22.901 UT. The new objects are well visible on the co-added image (see the finding chart linked below) as well as on individual 400-s frames, but are not present on numerous narrow-band H-alpha archival images from the INT down to limiting magnitude as faint as H-alpha = 22.3. We obtained also Sloan r' and Sloan i'-band images which helped us to classify the objects. Strong H-alpha emission together with relative faintness in Sloan r' and Sloan i' bands supports the classification of the objects as novae. Significantly stronger H-alpha emission of PNV J09552271+6903162 when compared to PNV J09553273+6902173 agrees with the different stages of the outburst in each of the objects.

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

 
 
  TOCP designation    CBAT designation  R.A. (J2000)  Dec. (J2000)  Offset R.A.  Offset Dec. 
PNV J09552271+6903162  M81N 2012-05a?   09 55 22.71   +69 03 16.2     56.1" W      38.9" S 
PNV J09553273+6902173  M81N 2012-05b?   09 55 32.73   +69 02 17.3      2.4" W      97.8" S 
 

The photometry obtained with the INT + WFC is summarized here:

 
 
                       PNV J09552271+6903162              PNV J09553273+6902173 
 
   Date UT         H-alpha mag      Sloan r' mag      H-alpha mag      Sloan r' mag 
 
2012 04 29.000       > 21.2                              > 21.2 
2012 05 16.944   19.5 +/- 0.2                            > 20.2 
2012 05 22.901   19.56 +/- 0.10                     19.66 +/- 0.10 
2012 05 22.919                     21.6 +/- 0.15                      20.60 +/- 0.08 
 

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