[vsnet-alert 12118] CI Cyg is on the rise since last March

[Ulisse Munari]

The current rebrightening phase was already announced on ATel 2732 on
last July 12 (see text attached below), where it is highlighted how
the current outburst (started in 2008) is a close copy of that CI Cyg 
experienced in 1970-78, which was characterized by several maxima.
The first one already occoured, peaking at V=9.50, B−V=+0.78, V−Rc=+0.80, 
V−Ic=+2.07on the first week of October 2008 (Siviero et al. 2009, MNRAS 399, 
2139), and minimum brightness was reached at V=11.0, B-V=+1.1, V−Ic=+3.2on
March of this year. The star is now halfway to the rise to the second of the
three predicted maxima.
Ulisse Munari

   "CI Cyg toward a new maximum in current major outburst phase"

ATel #2732; U. Munari, A. Siviero (INAF Padova-Asiago), G. Cherini,
             S. Dallaporta, P. Valisa (ANS Collaboration)
             on 12 Jul 2010; 15:16 UT

Subjects: Cataclysmic Variables, Novae, Variables

The symbiotic star CI Cyg is on a steep rise toward a second maximum in the 
major outburst phase it entered in 2008 (Munari et al. 2008, CBET 1487), the 
first one after 30 years of flat quiescence.

CI Cyg has experienced only a few outbursts in its long recorded history. The 
outbursts of 1911 and 1937 have been modest in both brightness amplitude and 
duration. Then, between 1970 and 1978 CI Cyg experienced a major outburst phase, 
characterized by three maxima occurring on Nov 1971 (V=9.3), Nov 1973 (V=9.8) 
and Aug 195 (V=8.7) and minima (V=11.1) on Jun 1973 and Mar 1975. One further 
and sharper minimum, centered on Oct 4, 1975 (at V=11.1), was caused by a total 
eclipse of the outbursting component by the M5.5 III companion, following the 
ephemeris Min(V) = 2442690 + 853.8xE (Belyakina 1984, Izv.Krym.Astrofiz.Obs. 68, 
108; Fekel et al. 2000, AJ 119, 1375).

The current outburst is a close copy of that CI Cyg experienced in 1970-78. 
After a maximum at V=9.50, B−V=+0.78, V−Rc=+0.80, V−Ic=+2.07 that occurred on 
the first week of October 2008 (Siviero et al. 2009, MNRAS 399, 2139), CI Cyg 
declined steadily and reached minimum brightness at V=11.0, B-V=+1.1, V−Ic=+3.2 
on March 2010. The time delay between maximum and minimum has been about about 
550 days, as for the 1970-78 event. At the time of the latter, a rise toward a 
second maximum started soon after the first minimum. The same is occurring right 
now, with CI Cyg currently on the rise toward a new maximum. The last 
measurement we collected gives V=10.44, B-V=+1.19, V-Rc=+1.18, V-Ic=+2.88 on 
July 9, 2010.

If the similarity with the 1970-78 active phase will be maintained, the second 
maximum around V=9.8 should be reached in several weeks time.