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Spectroscopic confirmation and photometry of the Fe II novae M31N 2017-11a (AT2017hvi) and M31N 2017-11c

ATel #10998; S. Fabrika, O. Sholukhova, A. Vinokurov, A. F. Valeev, Yu. Solovyeva, (SAO RAS), K. Hornoch (Ondrejov), M. Henze (SDSU), A. W. Shafter (SDSU)
on 23 Nov 2017; 18:09 UT
Credential Certification: Sergei Fabrika (fabrika@sao.ru)

Subjects: Optical, Nova, Transient

Referred to by ATel #: 11095, 11108

We report optical spectroscopic confirmation of the two recent M31 nova candidates M31N 2017-11a (AT2017hvi) and M31N 2017-11c. The first nova was discovered on 2017-11-04.695 by PMO-Tsinghua Supernova Survey (PTSS-17zap); the second was discovered on 2017-11-12.465 by K. Nishiyama and F. Kabashima (=TCP J00414435+4108287).

The spectral data were obtained on 2017 Nov. 18.648 UT (first nova) and 18.612 UT (second nova) using the Russian BTA telescope equipped with the SCORPIO spectrograph. The spectrum was taken with a resolution of 5.3 Å in the 4050 - 5810 Å range. Photometry of each nova was obtained near the time of the BTA spectrum with the same device gave B =19.55 ± 0.08, V = 19.07 ± 0.07, Rc = 18.55 ± 0.04 for M31N 2017-11a and B = 18.81 ± 0.08, V = 18.32 ± 0.06, Rc = 17.67 ± 0.05 for M31N 2017-11c.

The nova M31N 2017-11a shows Balmer emission lines together with numerous strong Fe II lines. Another spectrum was taken two days later at the Liverpool telescope (ATel #10990). The line peaks are narrow with broad wings. The Fe II lines (4923 and 5018 Å) have a FWHM = 760 ± 30 km/s, EWs are 19 and 30 Å, respectively. The hydrogen Hβ and Hγ lines have FWHM = 1200 ± 30 km/s, EWs are 140 and 42 Å, respectively.

The nova M31N 2017-11c shows Balmer emission lines together with the same Fe II lines. However, the FeII lines have flat-topped profiles, but hydrogen lines show truncated peaks. The Fe II lines (4923 and 5018 Å) have a FWHM = 1500 and 1430 (± 50) km/s, EW = 27 and 35 Å respectively. The hydrogen Hβ line has a FWHM = 1950 km/s, Hγ has 1250 km/s with error bars ± 30 km/s. The EWs for Hβ is 106 Å , for Hγ 22 Å. The widths were corrected for spectral resolution.

We conclude that these two M31 novae belong to the Fe II class.