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Discovery of Eleven Optical Nova Candidates in M81

ATel #3871; K. Hornoch (Astronomical Institute, Ondrejov, Czech Republic) and B. Sipocz (Centre for Astrophysics Research, U. of Hertfordshire, UK)
on 20 Jan 2012; 17:36 UT
Credential Certification: Allen W. Shafter (aws@nova.sdsu.edu)

Subjects: Optical, Nova, Transient

Referred to by ATel #: 3888

We report the discovery of five nova candidates in M81 found on a co-added 1100-s narrow-band H-alpha CCD image taken on 2012 Jan. 9.102 UT with the 2.54-m Isaac Newton Telescope (INT) at La Palma. The new objects are visible on the single frames used for the co-added image, 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.

Designations, positions, offsets from the galaxy center, and narrow-band H-alpha magnitudes are summarized in the following table:

TOCP designation   CBAT designation   R.A.Decl.   Offset R.A.     Offset Decl.   H-alpha mag
  PNV J09553278+6902139     2012-01a?     09 55 32.78     +69 02 13.9         2.1" W     101.2" S     19.31 +/- 0.05  
  PNV J09555380+6903383     2012-01b?     09 55 53.80     +69 03 38.3     110.6" E       16.8" S     19.26 +/- 0.05  
  PNV J09555778+6902041     2012-01c?     09 55 57.78     +69 02 04.1     132.0" E     111.0" S     20.50 +/- 0.09  
  PNV J09553792+6902498     2012-01d?     09 55 37.92     +69 02 49.8       25.5" E       65.3" S     20.49 +/- 0.09  
  PNV J09553560+6904154     2012-01e?     09 55 35.60     +69 04 15.4       13.0" E       20.3" N     20.10 +/- 0.10  

As comparison, we newly used images from the ING data archive which were taken with the INT on 2009 May 5.000 UT. Using six individual frames with exposure time of 600-s each, we got a deep, high-quality co-added image. By thorough visual comparison of this archival image and our recent image from Jan. 9.102 UT, we find six new nova candidates on the archival image. None of those have any records in any searches of papers or WWW pages devoted to extragalactic novae neither on SIMBAD. The new objects are visible on single frames used for the co-added image, but none of them is present on any other archival H-alpha INT image down to limiting magnitude as faint as H-alpha = 22.3.

In addition, we measured following magnitude of the PNV J09553266+6906072 (ATEL #3735), a bright nova in M81 (ATEL #3770): 2012 Jan. 9.102 UT, H-alpha = 19.41 +/- 0.05.

Supplementary material containing table with their designations, positions, offsets from the galaxy center, and narrow-band H-alpha magnitudes as well as their identification chart and a finding chart of the five M81 nova candidates from 2012 Jan. 9.102 UT is available through the link below.

Supplemental Material