Spectroscopy and photometry of the nova M31N 2015-08c and photometry of the recurrent nova M31N 2008-12a

ATel #8033; S. Fabrika, E. A. Barsukova, A. F. Valeev, A. Vinokurov, O. Sholukhova (Special Astrophysical Observatory), V. P. Goranskij (SAI, Moscow University), K. Hornoch (Astronomical Institute, Ondrejov), M. Henze, M. Hernanz (CSIC-IEEC), G. Sala, J. Jose, J. Figueira (UPC-IEEC), A. W. Shafter (SDSU)
on 10 Sep 2015; 12:31 UT
Credential Certification: Sergei Fabrika (fabrika@sao.ru)

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We report optical spectroscopy and photometry of the recent M31 nova candidate M31N 2015-08c (= PNV J00441654+4132239) and photometry of M31N 2008-12a. The first object was discovered by Gloria Sala et al. (ATEL #7963), the second (= PTF09hsd) is well known recurrent nova (recent ATELs #8029, #7984, #7980, #7979, #7976, #7974, #7969, #7967, #7965, #7964) undergoing the recent 2015 eruption. The spectral data of 2015-08c were obtained on 2015 Sept. 4.924 UT using the Russian BTA telescope equipped with the SCORPIO spectrograph. The spectra were taken with a spectral resolution of 13.3 Å in the spectral range of 3650 - 7890 Å. The nova M31N 2015-08c shows very strong emission Balmer lines with P Cyg type profiles, as well as broad P Cyg FeII and NaI (5686, 5892 and 6159 Å) lines, and FeII blends. We observe as well a bright O I 7773 Å emission without P Cyg. Widths of H-alpha and H-beta lines (FWHM, with account for spectral resolution) is 1560 and 1590 km/s respectively. Equivalent width of their emission components are 378 and 106 Å respectively. A half-width at zero intensity of H-alpha is 2500 km/s. A radial velocity of strong emission components (heliocentric) is -110 km/s, those of absorption components is -1880 km/s. Our spectra, in conjunction with the radial velocity map of M31 from 21-cm measurements (Corbelli et al., 2010, Astron. Astrophys. 511, A89) for the nova location (-100 km/s), shows that the object is an Fe II nova located in the disk of M31.

A photometry of the nova obtained shortly prior to the spectroscopy with the same device gave B = 18.75, V = 18.08, Rc = 17.72, Ic = 17.89. An accuracy of the photometry is ± 0.05. We used standards from Massey et al. (AJ, 131, 2478, 2006). We have an additional photometry based on a sequence of 4x200s stacked R filter CCD images, obtained with the 80 cm 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 E2V CCD Camera (BV coated 2k x 2k chip with 13.5 microns sq. pixels). The R band magnitudes are: 2015 Aug. 27.07 UT 19.1 ± 0.2; 28.06 19.2 ± 0.2; 29.10 18.16 ± 0.15; 30.02 17.39 ± 0.11; 2015 Sept. 01.93 UT 17.96 ± 0.13; 05.06 17.8 ± 0.2; 06.08 17.7 ± 0.2; 07.03 18.0 ± 0.2; 08.01 18.0 ± 0.2.

A photometry of M31N 2008-12a has been taken with the SCORPIO spectrograph on 2015 Sept. 4.854 UT and on 2015 Sept. 6.032 UT. The accuracies and standards are the same as in 2015-08c. On the first night we find B = 20.46, V = 20.29, Rc = 20.15. On the second night we obtain B = 20.55, V = 20.26, Rc = 20.24, Ic = 20.32.