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H-alpha Confirmation of Seven Nova Candidates in M31

ATel #4181; K. Hornoch (Astronomical Institute, Ondrejov, Czech Republic), O. Vaduvescu (ING, La Palma & IAC, Tenerife, Spain), C. Zurita (IAC, Tenerife, Spain)
on 16 Jun 2012; 18:44 UT
Credential Certification: Allen W. Shafter (aws@nova.sdsu.edu)

Subjects: Optical, Nova, Transient

Referred to by ATel #: 4511

Recently, the discoveries of several nova candidates in M31 have been reported (ATEL #3735, #3976, and #3987), but there have been no spectroscopic confirmations. To classify these objects, we obtained narrow-band H-alpha, Sloan r', and Sloan i'-band CCD images of the central region of M31 using the 2.5-m Isaac Newton Telescope (INT) + WFC at La Palma under ~1.2" seeing on May 22.198 - 22.216 UT.

The photometry obtained from the INT + WFC images is summarized in the following table:

 
  TOCP designation    CBAT designation   H-alpha mag      Sloan r' mag     Sloan i' mag 
PNV J00413185+4108320  M31N 2012-05d?   16.74 +/- 0.05   19.53 +/- 0.08   20.8  +/- 0.15 
PNV J00423149+4126138  M31N 2012-05c?   16.67 +/- 0.04   19.16 +/- 0.07   19.49 +/- 0.09 
PNV J00423272+4115373  M31N 2012-05b?   16.76 +/- 0.05   19.38 +/- 0.08   20.2  +/- 0.1 
PNV J00425927+4118146  M31N 2012-05a?   14.76 +/- 0.04   16.98 +/- 0.04   17.07 +/- 0.08 
PNV J00422292+4104165  M31N 2012-03c?   17.58 +/- 0.06   19.59 +/- 0.09   20.6  +/- 0.15 
PNV J00422773+4108136  M31N 2012-03b?   17.92 +/- 0.07   19.80 +/- 0.10   20.3  +/- 0.1 
PNV J00433417+4125078  M31N 2012-03a?   20.4  +/- 0.15       > 22.2           > 20.9 
PNV J00415824+4124011  M31N 2011-11c?   20.8  +/- 0.2        > 22.2           > 20.9 
PNV J00421003+4105141  M31N 2011-11a?   18.99 +/- 0.10   21.4  +/- 0.1        > 20.8 
PNV J00424359+4116378  M31N 2011-05a?   18.35 +/- 0.09   20.9  +/- 0.3        > 20.8 
 
Strong excess H-alpha emission is present in all seven nova candidates discovered during 2012 March and May, as well as in PNV J00421003+4105141 and PNV J00415824+4124011, which were confirmed spectroscopically as FeII-class novae in M31 (ATEL #3769 and #3778). A very similar H-alpha excess is also observed in PNV J00424359+4116378, which was originally classified as probable nova due to its strong excess H-alpha emission on 2011 July 14 (ATEL #3486). Relative faintness in the Sloan i' with respect to the Sloan r' band excludes the possibility that some of the seven spectroscopically unconfirmed objects could be Mira-like stars observed during a maximum. Instead, there is a strong support for the classification of the seven objects as novae.

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.