Discovery of coronal emission lines in V407 Cyg
ATel #2546; U. Munari, A. Siviero (INAF Padova-Asiago), P. Valisa (ANS Collaboration)
on 11 Apr 2010; 22:05 UT
Credential Certification: Ulisse Munari (ulisse.munari@oapd.inaf.it)
Subjects: Optical, Binary, Cataclysmic Variable, Nova, Variables
Referred to by ATel #: 2741
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.
