Optical spectroscopy and photometry of nova M31N 2013-05b

ATel #5145; E. A. Barsukova, S. Fabrika, A. Vinokurov (Special Astrophysical Observatory, Russia), K. Hornoch (Astronomical Institute, Ondrejov, Czech Republic), M. Henze (ESA/ESAC, Spain), A. W. Shafter (SDSU)
on 19 Jun 2013; 08:16 UT
Credential Certification: Barsukova E.A. (bars@sao.ru)

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We report additional optical spectroscopy, performed on 2013 June 1.006 UT, of the recent M31 nova M31N 2013-05b (= SWIFT J004255.6+411412 = PNV J00425563+4114125; see ATels #5091, #5092, #5099). Another spectrum, which was obtained one day later, was published in ATel #5123.

Our spectrum has been taken with the Russian BTA telescope equipped with the SCORPIO spectral camera. The spectral range was 3800-6990 A with an resolution of 13 A. The spectrum shows a blue continuum with a very strong H-alpha emission line with equivalent width of 450 +/- 100 A. The line width is characterized by a FWHM = 1000 +/- 60 km/s, which is comparable with the measurement given in ATel #5123. This line appears to have very broad asymmetric wings with HWZI = 5600 +/- 400 km/s. In addition, near the blue limit of the spectral range, we marginally detected two bright [Ne III] 3869, 3967 A lines. Despite the relatively low S/N of the spectrum, the broad H-alpha line wings (HWZI >> 2500 km/s), together with the suspected [Ne III] lines suggest that the object may belong to the "He/N" spectroscopic class.

Furthermore, we report photometry based on five R-band images and three V-band images obtained with the same device. On May 31.995 UT we measured R = 19.0 +/- 0.1, and on June 01.001 UT we found V = 19.5 +/- 0.15. Additional photometry obtained on a co-added 500-s R-band CCD frame taken on 2013 June 8.028 UT with the 0.65-m telescope at Ondrejov gave R = 20.8 +/- 0.4. Based on previously published photometry and the photometry published in this ATel, we have determined that the nova faded extremely rapidly, with times to decline by 2 and 3 magnitudes from maximum light estimated to be ~ 1 day and ~ 3-4 days, respectively. Taken together, the spectroscopic and photometric properties of M31N 2013-05b are consistent with those typical of recurrent novae.