The remnant of the luminous red nova PSN J14021678+5426205/M 101 in infrared and optical ranges

ATel #8599; V. P. Goranskij, A. M. Tatarnikov, N. I. Shatsky, A. E. Nadjip (SAI, Moscow Univ.); E. A. Barsukova, A. F. Valeev (Special Astrophysical Observatory, Russia)
on 28 Jan 2016; 13:31 UT
Credential Certification: Vitaly Goranskij (goray@sai.msu.ru)

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We report a detection of the infrared source at the position of this red nova in the galaxy M 101 (ATel #7069, #7070, #7072, #7079, #7082, #7206). The object was discovered on 2015 February 10 by C. D. Vintdevara (Barlad Observatory, Romania) in the course of the repeated outburst, the first outburst was happened in 2014 November. We used the new 2.5 m telescope of the SAI Caucasus Mountain Observatory equipped with ASTRONIRCAM instrument operating in JHK bands (MKO photometric system). Observations were carried out on 2016 January 22.04 UT, the accumulated exposures were 1560 s in J, 740 s in H, and 930 s in K. Magnitudes referred to 2MASS point sources (transferred to MKO) in the field of view are the following: J = 18.65 &plusm;0.05; H = 17.64 &plusm;0.10; K = 16.32 &plusm;0.05. The previous optical observations of this red nova were performed on 2015 December 17.04 UT with the Russian 6 m telescope and SCORPIO focal reducer. The exposures were 860 s in the Rc and 579 s in the Ic bands. The source was not detected. The detection limits were 23.0 mag in Rc and 21.5 in Ic. With the distance modulus of M 101 of 29.22 mag (NED), the absolute magnitude of the source in the K band is equal to -12.9. This suggests that the nova passes through the stage of a ″brown (or L-type) supergiant″ like that one observed in V838 Mon (Evans et al., 2003, MNRAS V.343, 1054). With the known distance to V838 Mon, its absolute K magnitude is estimated as -9.2 a year after the 2002 outburst. Thus the brightness of M 101 red nova exceeds that one of V838 Mon by about 30 times. J-K color index of M101 red nova, 2.3 mag is redder than that of V838 Mon a year after its outburst, 1.8 mag. Our optical observations in 2015 showed that M 101 red nova manifested other extreme parameters among red novae, as maximum outburst luminosity, maximum outburst duration, minimum outburst amplitude, and unusual double-peak shape of the light curve. We interpreted this event as merging of components in a massive system of OB stars (the preliminary results of the optical research are in http://www.vgoranskij.net/lrn2015-in-m101.pdf ; the paper by Goranskij et al. will appear in Astrophysical Bulletin, 2016, Vol.71, No.1, p.82).

The images in Rc and JHK bands