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Outburst of the symbiotic star CI Cygni
August 31, 2008

Further to AAVSO Special Notice #121, we urgently request visual
observations and instrumental photometry of the outbursting 
symbiotic variable star CI Cygni, beginning immediately 
(2008 August 31; JD 2454710) and continuing for at least the next
several weeks as the outburst evolves.

The last major outburst of CI Cygni occurred in March 1975.  We
note that CI Cyg should be in or near eclipse according to the
ephemeris published by Fekel et al. (2000, AJ 119, 1375); their
ephemeris predicts an eclipse date of 2454695.4 (assuming T0 =
2450426.4 and a period P = 853.8).

Both visual observations and instrumental photometry of this event
are strongly encouraged.  Filtered time series observations are
especially encouraged, particularly if the system goes into
eclipse during the outburst.  Calibrated, filtered photometry
may provide constraints on the physical properties of the
primary and secondary stars in this system if and when the outburst
source is eclipsed.

Observer G. Poyner (Birmingham, England) estimates that CI Cyg
was at m(vis) = 9.8 on JD 2454709.515 (2008 August 31.015).
For information about the course of the current outburst through
2008 August 31, see AAVSO Special Notice #121, available at: 
http://www.aavso.org/publications/specialnotice/121.shtml


CI Cygni is located at RA: 19h 50m 11.8s , Dec: +35d 41m 03s (J2000)


Charts for CI Cygni may be generated with VSP:

http://www.aavso.org/observing/charts/vsp/index.html?pickname=CI%20Cyg


Recently submitted observations for CI Cygni are available here:

http://www.aavso.org/cgi-bin/newql.pl?name=CI%20Cyg&output=html


Please report all observations to the AAVSO as CI Cyg (AUID 000-BCJ-172).


This AAVSO Alert Notice was prepared by Matthew Templeton.

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