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Nova candidate 2008-09b in M31 galaxy is not a nova

ATEL # 1762; E. Barsukova, S. Fabrika, O. Sholukhova, A. Valeev (Special Astrophysical Observatory, Russia), V. Goranskij (SAI, Moscow Univ.), W. Pietsch (MPE, Germany), K. Hornoch (Lelekovice, Czech Republic)
on 4 Oct 2008; 19:06 UT
Password Certification: Barsukova E.A. (bars@sao.ru)

Subjects: Infra-Red, Optical, Nova, Variables, Stars

We report the spectroscopic observations of an optical nova candidate 2008-09b (RA 00:40:31.94, +41:06:25.0, J2000) discovered by F. Yuan et al., (http://www.cfa.harvard.edu/iau/CBAT_M31.html) on 2008 Sep. 20.15 UT at the maximum brightness of 18.5 ROTSE unfiltered mag. The spectrum was taken using the Russian 6-m telescope and SCORPIO spectral camera on 2008 Oct. 2.032 UT. The spectrum range is 390-755 nm, resolution 1.3 nm. The brightness of the object was 20.3 mag in the V band at the moment of observation. BTA CCD unfiltered magnitude was 18.4 what did not confirm the variability of this star since its discovery.

The spectrum of 2008-09b is very red and does not belong to a classical nova. Multiple TiO bands, and weak narrow Halpha line are presented. Spectral class is a supergiant M9. This spectrum closely resembles both spectra of Galactic peculiar red novae remnants, V4332 Sgr and V838 Mon taken in 2007.

We found this star in the infrared POSS II-N plate taken on 1993 Sep. 23 UT at the level of 18.0 in the I band. The star is under the plate limit of R=21.0 in the POSS II red plate taken on 1989 Oct 1 UT, and is unseen in other POSS plates, too. The object is identical to 2MASS 00403197 +4106243 (J=17.0+/-0.2; H=15.34+/-0.12; K=14.85+/-0.10). So, this star is seen in all infrared or unfiltered images, and may be constant red supergiant star. If a red nova, this star exploded before 1993.

Spectrum of M31N 2008-09b


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