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AAVSO Special Notice #232

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Note: This Special Notice was originally issued as AAVSO Special Notice #231; #232 is the correct number.

Bright outburst of the pre-main sequence variable Z CMa

February 4, 2011: John Bortle, Stormville, NY, reports that the pre-main sequence binary variable Z CMa is in outburst, according to his observation of 2011 February 4.0 UT at visual magnitude 8.5. Observations in the AAVSO International Database confirm this outburst, which may have begun as long ago as April 2010, when it began brightening slightly from visual magnitude 10.7. When Z CMa emerged from its seasonal gap in November 2010, it was already 9th magnitude.

The current outburst is as bright as the one that occurred in 2008, the brightest in the star's known history. Z CMa is a very interesting object, a binary composed of a Herbig Be star and an FU Ori star. The Herbig star is embedded in nebulosity. The system is an x-ray source and has an x-ray jet. According to Stelzer et al. (2009, Astronomy & Astrophysics v.499, p.529, and astro-ph arXiv:0903.4060), the FU Ori star is the source of both the optical outbursts and the x-ray emission.

Observations of Z CMa are strongly encouraged, both during the current outburst and throughout the observing season. With its range of visual magnitude ~8.0-10.5, it is an excellent visual observing target. Visual, PEP, and CCD observations are welcome.

Coordinates: RA 07:03:43.16   Dec -11:33:06.2  (J2000.0)

Charts for Z CMa may be created using VSP:
http://www.aavso.org/vsp

Please report observations to the AAVSO International Database using the name Z CMA.

Our thanks to John Bortle for drawing our attention to the current outburst of this interesting system!

This AAVSO Special Notice was compiled by Elizabeth O. Waagen.
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