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Follow up spectroscopy and photometry of TYC 2505-672-1 (MASTER OT J095310.04+335352.8)

ATel #4834; V. Afanasiev (SAO RAS), D. Denisenko (Lomonosov State University, SAI), V. Krushinsky (Ural Federal University), E. Gorbovskoy, V. Lipunov , P. Balanutsa, V. Yecheistov, N. Tiurina, V. Kornilov, A. Belinski, N. Shatskiy, V. Chazov, A. Kuznetsov, D. Zimnukhov (Moscow State University, SAI), I. Zalozhnih, A. Popov, A. Bourdanov, A. Punanova (Ural Federal University), K. Ivanov, S. Yazev, N. Budnev, E. Konstantinov, O. Chuvalaev, V. Poleshchuk, O. Gress (Irkutsk State University), A. Parkhomenko, A. Tlatov, D. Dormidontov, V. Senik (Kislovodsk solar station of the Pulkovo observatory RAS), V. Yurkov, Y. Sergienko, D. Varda, E. Sinyakov (Blagoveshchensk Educational University),S. Shurpakov, V. Shumkov, P. Podvorotny (MASTER team members), H. Levato, C. Saffe (ICATE), C. Mallamaci, C. Lopez and F. Podest (Observatorio Astronomico Felix Aguilar; OAFA)
on 22 Feb 2013; 20:09 UT
Credential Certification: Vladimir Lipunov (lipunov2007@gmail.com)

Subjects: Optical, Transient, Variables

Following the detection of TYC 2505-672-1 fading episode by MASTER network (Denisenko et al., ATel #4784) we have performed the additional spectroscopic and photometric observations of this object in minimum light. The spectrum of TYC 2505-672-1 was obtained with the Russian 6-m BTA telescope (SAO RAS, Nizhniy Arkhyz, Karachay-Cherkessia) + SCORPIO instrument (Afanasiev and Moiseev, 2005, Astron. Lett., Vol. 31, No. 3, p. 194) on 2013 Feb. 10. It is consistent with that of M1III red giant without unusual absorption lines, but with H-alpha in emission (FWHM=320 km/s). The observed wavelength of H-alpha line is 6561.0+/-0.1 AA corresponding to the blue shift of -82 km/s. A number of weak FeI and NaI emission lines are also present with typical FWHM of ~150-180 km/s. The spectrum is available at http://master.sai.msu.ru/static/OT/TYC2505-672-1-BTAspectrum0210.gif

BVRI photometry of TYC 2505-672-1 was obtained with MASTER-Amur binocular telescope (two identical 0.40-m f/2.5 reflectors + 4kx4k CCDs) on 2013 Feb. 11.61-11.62 UT with three 60-sec exposures taken in each filter and again on Feb. 22.62-22.63 UT. The following magnitudes were measured on Feb. 11: B=16.81, V=15.37, R=14.58, I=13.49. The corresponding (B-V) color of 1.44 is less than the value of B-V=1.80 in Tycho2 catalog (Hog et al., 2000) measured during HIPPARCOS observations in 1990-1992 and close to the APASS value of 1.38 measured on two nights around Jan. 30, 2012 with the variable at V~15.0 (Henden, private communication).

MASTER-Amur currenlty observes the field of TYC 2505-672-1 every 5-7 nights in the white light. The observed unfiltered magnitudes in Nov. 2012 - Feb. 2013 are consistent with the star being constatnt during this interval of time within the errors of photometry.

The object's behavior is unusual for the typical R CrB stars. This may be the first active episode of the red giant entering the short RCB phase. That may explain the absence of surrounding carbon dust, small J-K colors and presence of hydrogen emission. We encourage the continued spectroscopic and photometric monitoring to follow up the evolution of the current fading episode.

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