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Rapid fading in the luminous blue variable S Doradus
April 15, 2010

Noel D. Richardson and Douglas R. Gies (Georgia State University)
announced on 2010 April 14 (Astronomer's Telegram #2560) that S Doradus
is currently fading in optical brightness, while its hydrogen Balmer
line (H-alpha) brightness is increasing.  The V-band magnitude of S Dor
(as measured by ASAS-3; Pojmanski, G., 2002, AcA 52, 397) has been
declining for more than a thousand days.  The star began a more rapid
decline earlier this year, and is now fainter than V=9.5.  BVRI
photometry by G. Di Scala (Sydney, NSW, Australia) shows that the star
was at V=9.83 on 2010 March 08.4535 (JD 2455263.9535), and the most
recent visual observation (A. Plummer, Linden, NSW, Australia) put the
star at m(vis)=9.9 on April 08.4215 (JD 2455294.9215).  Observations of
S Dor are encouraged to follow this current event.

S Dor is the class prototype for the luminous blue variables,
supermassive stars that exhibit irregular photometric variability, and
are experiencing substantial mass loss.  All observations of S Dor --
both visual estimates and CCD photometry -- will be important for
studying the current event. Intensive CCD time-series observations are
not critically needed, but nightly photometry will be very useful.


S Dor is located in the Large Magellanic Cloud, at the following (J2000)
coordinates:

        RA: 05 18 14.35 , Dec: -69 15 01.1


Charts for S Dor may be plotted using AAVSO VSP:

http://www.aavso.org/observing/charts/vsp/index.html?pickname=S%20Dor [4]


Please promptly report all observations to the AAVSO using the name
"S DOR".


This AAVSO Special Notice was prepared by Dr. Matthew Templeton

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