[vsnet-alert 15433] (fwd) MASTER OT J095310.04+335352.8 is not a hydrogen-poor R CrB star

Taichi Kato tkato at kusastro.kyoto-u.ac.jp
Sat Feb 23 11:04:22 JST 2013

(fwd) MASTER OT J095310.04+335352.8 is not a hydrogen-poor R CrB star

ATEL #4834							     ATEL #4834

Title:	Follow up spectroscopy and photometry of TYC 2505-672-1 (MASTER
		OT J095310.04+335352.8)
Author:	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)
Queries:	lipunov2007 at gmail.com
Posted:	22 Feb 2013; 20:09 UT
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.

Global MASTER Net: http://observ.pereplet.ru

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