ATEL #2546                                                           ATEL #2546

Title:          Discovery of coronal emission lines in V407 Cyg
Author: U. Munari, A. Siviero (INAF Padova-Asiago), P. Valisa (ANS Collaboration)
Queries:        ulisse.munari@oapd.inaf.it
Posted: 11 Apr 2010;  22:05  UT
Subjects:       Optical, Binaries, Cataclysmic Variables, Novae, Variables

We report about discovery of [FeX] 6375, [FeXI] 7890, [ArX] 5535 and [NiXII] 4233 Ang coronal emission lines in V407 Cyg, which are steadily increasing in intensity with time.

V07 Cyg is a symbiotic binary harboring a Mira variable, of 745 day pulsation and a possible orbital period of 43 years, at a 
distance of  2.5/3.0 kpc and a reddening of E(B-V)=0.5/0.6 (Munari et al. 1990, MNRAS 242, 653). Mira of such a long pulsation 
period are generally OH/IR sources, with a thick dust envelope which prevents direct observation of the central star. 
In addition to a possible previous one in 1936 (when the object was noted for the first time by Hoffmeister 1949, VVS 1, 295), 
V407 Cyg has been   recently discovered in outburst by Nishiyama and Kabashima (2010, CBET   #2199) on Mar 10.8 UT. Spectroscopic confirmation was first provided by   Munari et al. (2004, CBET #2204) on Mar. 13.1 UT. They noted the emergence
of the spectrum of a He/N nova that overwhelmed the absorption spectrum of   the Mira.  Numerous and strong emission lines were 
observed, which belonged   to two distinct groups.  The first group, composed by sharp profiles with   even narrower central 
absorptions, originated from the ionized slow wind of   the Mira. The second group, characterized by much broader profiles for   
helium, nitrogen and hydrogen lines , originated from the nova fast expanding   ejecta. Such a scenario was highly reminiscent 
of the recurrent nova RS Oph.   The outburst of V407 Cyg has since then been detected also in gamma-rays (ATel   #2487) and at 
radio wavelengths (ATel #2506, ATel #2511, ATel #2514, ATel   #2536), and observed in the infrared (CBET #2210).

Our tight Echelle high-resolution monitoring of the spectral evolution of   V407 Cyg traces the first appearance of the coronal 
emission lines around   March 17, when [FeX] 6375 Ang had an equivalent width of about 4 Ang. Since   then its equivalent width 
has steadily increased, reaching 17, 24, 36, 49   and 61 Ang on Mar 23, 28, Apr 2, 7 and 10, respectively.
The FWHM has   remained moderately stable around 600 km/sec over. Other coronal lines   present in V407 Cyg are [FeXI] 7890, [ArX] 5535 and [NiXII] 4233. As of   April 10, [NiXIII] 5116 and [FeXIV] 5303 are not detected. 
The coronal line   spectrum of V407 Cyg resemble quite closely that observed in RS Oph during its 2006 outburst.

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