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Spectrum of optical counterpart to Swift/UVOT M31 transient

ATel #3068; S. Fabrika, E. A. Barsukova, A. F. Valeev, O. Sholukhova (Special Astrophysical Observatory, Russia), K. Hornoch (Astr. Inst., Ondrejov, Czech Republic), V. P. Goranskij (Sternberg Institute, Moscow Univ.), W. Pietsch (MPE, Germany)
on 5 Dec 2010; 23:13 UT
Credential Certification: Barsukova E.A. (bars@sao.ru)

Subjects: Optical, Cataclysmic Variable, Nova, Transient

We present spectrum and optical photometry of Swift/UVOT transient in the central region of the Andromeda Galaxy reported by Pietsch et al. (ATEL#3061).

The R band photometric data we have: 2010 Nov. 14.946 UT, 21.5 (K. Hornoch, P. Hornochova, and B. Mikulecka); 20.706, 20.4 (Hornoch); 25.672, 19.9 +/- 0.15 (Hornoch); 27.679, 20.4 +/- 0.2 (Hornoch); Dec. 3.801, 19.05 +/- 0.1 (Hornoch and Hornochova); 4.894, 18.8 +/- 0.1 (Hornoch and Hornochova).

We have taken spectra of the transient on 2010 Dec. 5.74 UT with the Russian 6-m telescope (BTA) equipped with the SCORPIO spectral camera. The spectral range is 380-720 nm, the spectral resolution is 1.3 nm. Strong and bright hydrogen lines from H-alpha to H9 are observed in the spectrum. H-beta and H-alpha emission line profiles are very asymmetric with extended red wings. EWs of these two lines are 7.5 and 27.5 nm respectively, their widths corrected for spectral resolution are 1350 and 1270 km/s respectively. The star heliocentric radial velocity measured in these hydrogen lines is -310 km/s. The H-beta line shows obvious P Cyg type profile with absorption/emission separation of 1700 km/s. There are numerous HeI and NII emission lines detected, as well as MgI 517.2, 518.3 nm lines. We conclude that this UV transient is a slowly brightening nova of He/N type.

During the spectral observations we have taken B, V, R images of the field, the magnitude estimates obtained with an accuracy of 0.1 mag are B = 19.26, V = 19.23, R = 18.76.

Spectrum of the optical counterpart to Swift/UVOT M31 transient