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Spectroscopy and photometry of the novae M31N 2014-09a and M31N 2014-09b

ATel #6498; E. A. Barsukova, S. Fabrika, A. F. Valeev, A. Vinokurov, O. Sholukhova (Special Astrophysical Observatory), M. Henze (ESA/ESAC, Spain), K. Hornoch (Astronomical Institute, Ondrejov), G. Sala, J. Figueira (UPC-IEEC), A. W. Shafter (SDSU), V. P. Goranskij (SAI MSU)
on 25 Sep 2014; 18:21 UT
Credential Certification: Sergei Fabrika (fabrika@sao.ru)

Subjects: Optical, Nova, Transient, Variables

We report optical spectroscopy and photometry of the recent M31 nova candidates M31N 2014-09a (= PNV J00432372+4122256) and M31N 2014-09b (= PNV J00434997+4114049). The first object was discovered by Koichi Nishiyama and Fujio Kabashima on 2014 Sept. 08.610 UT (ATEL #6463), the second one was announced on the CBAT Transient Objects Confirmation Page (see also ATEL #6490). M31N 2014-09b is located in the disk of M31.

The data were obtained on 2014 Sept. 22.867 UT (2014-09b) and 22.982 UT (2014-09a) using the Russian BTA telescope equipped with the SCORPIO spectrograph. Photometry of the objects obtained shortly prior to the spectroscopy gave B = 18.70±0.06, V = 18.62±0.06, R = 17.96±0.05 (2014-09a) and B = 18.83±0.06, V = 18.49±0.05, R = 8.33±0.05 (2014-09b). The spectra were taken with a spectral resolution of 5 A in the spectral range of 4050 - 5850 A.

The nova M31N 2014-09a shows very strong emission Hbeta, Hgamma, Hdelta lines with P Cyg type profiles, as well as broad Fe II lines and Fe II blends. The Hbeta and Fe II lines are double-peaked. We have measured the Hbeta, Hgamma, Hdelta and Fe II (5169 A) line parameters, they are respectively: FWHM = 1830, 2170, 2090, 2300 km/s; EW = 115, 24, 24, 64 A respectively. The radial velocity of Hbeta is -190 km/s (all radial velocities were measured as the center of gravity). The radial velocities in P Cyg absorption line profiles are -1960, -1650 and -1600 km/s for Hbeta, Hgamma and Hdelta respectively.

The nova M31N 2014-09b shows a blue continuum with a rich absorption spectrum with blue-shifted hydrogen, He I and numerous Fe II lines. The strongest lines of He I and Fe II show P Cyg-like profiles. The Hbeta, Hgamma and Hdelta line parameters are FWHM = 1100 km/s, EW = 2.6 A; FWHM = 600 km/s, EW = 2.7 A, and FWHM = 1300 km/s, EW = 2.8 A respectively. The radial velocity of the Hbeta line is -520 km/s. Taking into account the radial velocity map of M31 from 21-cm measurements (Corbelli et al., 2010, Astron. Astrophys. 511, A89) for the nova location we have found that the measured radial velocity corresponds to an expansion velocity of about 370 km/s.

We conclude that both candidates are novae that belong to the Fe II class, however, 2014-09a borders on being a member of the broad-lined Fe II class (Fe IIb). The disk nova M31N 2014-09b is probably a slowly rising nova near or before its maximum light.

We also report additional (pre-discovery) photometry of M31N 2014-09b obtained with the 80 cm Ritchey-Chretien F/9.6 Joan Oro telescope at Observatori Astronomic del Montsec, owned by the Catalan Government and operated by the Institut d'Estudis Espacials de Catalunya, Spain, using a Finger Lakes PL4240-1-BI CCD Camera (with a Class 1 Basic Broadband coated 2k x 2k chip with 13.5 microns sq. pixels). The object was detected in four 4x200s stacked R filter CCD images and first seen on 2014 Sept. 14.13 UT, which is before the pre-discovery date reported in ATEL #6490. The R band magnitudes and upper limits are: 2014 Sept. 02.96 UT: >20.2; 10.14 UT: >19.3; 14.13 UT: 19.5±0.1; 16.07 UT: 19.4±0.1; 20.11 UT: 19.0±0.1; 21.04 UT: 18.6±0.2. All magnitudes were obtained from a photometric solution using R magnitudes of the Local Group Galaxies Survey (Massey et al. 2006, AJ, 131, 2478).