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
Credential Certification: Ulisse Munari (ulisse.munari@oapd.inaf.it)

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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 a few weeks time.