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Spectroscopy and photometry of the luminous red nova PSN J14021678+5426205 in M 101

ATel #7206; V. P. Goranskij, D. V. Cherjasov, B. S. Safonov, O. V. Vosyakova (SAI, Moscow University), E. A. Barsukova, O. I. Spiridonova, A. F. Valeev (Special Astrophysical Observatory, Russia)
on 11 Mar 2015; 19:55 UT
Credential Certification: Vitaly Goranskij (goray@sai.msu.ru)

Subjects: Optical, Nova, Star, Transient, Variables

Referred to by ATel #: 8599, 8848, 8891

Spectra of PSN J14021678+5426206 in M101 (ATel #7063, #7069, #7070, #7072, #7079, #7082) were obtained with the Russian 6-m telescope BTA equipped with the SCORPIO camera on 2015 Feb 24.95 UT (wavelength range 4052 - 5847 Å), and on 2015 Feb 25.08 UT (wavelength range 5750 - 7498 Å). Spectral resolution was 5 Å. The spectrum shows cool photospheric continuum with multiple deep absorption lines, and Hα emission. Hα line has an asymmetric profile with the maximum intensity at the velocity of 60 km/s with a red wing expanding to a velocity of 600 km/s (hereafter the velocities are measured relative to the M 101 center, 241 km/s, NED). EW(Hα) = -21 Å and FWHM = 530 km/s (corrected for instrumental profile). Hβ has a P Cyg type profile with an absorption component at -520 km/s. Other strongest lines with the P Cyg type profiles are Na I 5889, 5896 Å, Ba II 6141 and 6497 Å. A spectral type may be derived as K0 I - K5 I by the method of cross-correlation with spectra of normal luminosity class I stars (Jacoby et al., 1984, ApJSS 56, 257). Strengths of absorption lines exceed the line strengths of normal stars by 4 - 6 times. There are depressions in the ranges of 5000 - 5500 Å and 6100 - 6400 Å due to line blocking. The absorption line set of the nova repeats in detail the line set of V838 Mon in its spectra taken on 20th day after the beginning of outburst. We have identified Mg I, Fe I, Cr I, Ti I, Ba II and other element species. The essential difference is the absence of Li I 6708 Å line in the spectrum of M 101 nova, which was very strong in the spectrum of V838 Mon. The velocity of the absorption line spectrum is -440 km/s.

Photometric CCD BVRc observations were performed since 2015 Feb 15 with the following telescopes: (1) 2.5-m telescope of the SAI Caucasus Mountain Observatory; (2) the SAO 1-m Zeiss telescope; (3) the SAO 6-m BTA telescope with the SCORPIO spectral camera. A comparison star located at 14:02:17.0, +54:27:30, J2000.0 was used, its BVRc magnitudes were measured as (18.01, 16.88, 16.02) in three nights relative to the BVRcIc standard by Raiteri et al. (1999, AsAp 352, 19) in the outskirts of S4 0954+65. The accuracy of the attachment was of 0.02 mag. BVRc data of PSN J14021678+5426205 are as follows:

Feb 15.95 UT (18.86, 17.67, 16.78) (1)

Feb 18.07 UT (18.99, 17.65, 16.77) (2)

Feb 19.09 UT (19.03, 17.66, 16.80) (2)

Feb 21.04 UT (19.09, 17.71, 16.83) (1)

Feb 22.03 UT (19.05, 17.69, 16.82) (2)

Feb 23.07 UT (19.08, 17.69, 16.81) (2)

Feb 24.07 UT (19.07, 17.69, 16.83) (2)

Feb 24.90 UT (19.09, 17.70, 16.83) (2)

Feb 24.93 UT (19.04, 17.69, 16.83) (3)

Feb 28.06 UT (19.23, 17.79, 16.90) (1)

Mar 8.96 UT (19.83, 18.28, 17.32) (2)

Mar 10.04 UT (19.81, 18.31, 17.38) (2)

Mar 11.06 UT (19.86, 18.40, 17.49) (2).

Both the spectroscopy and the photometry confirm that the object is a luminous red nova. In the second half of February, the light curve of the nova had a plateau which changed with a rapid decay in the beginning of March.