[vsnet-be 52] V380 Cep (=NSV 13489): A Herbig Be Photometric Binary?

[Thom Gandet <tgandet@mindspring.com>]

   V380 Cep (=HD 200775 = NSV 13489) is an AAVSO program star and is 
one of the brightest Herbig-Be stars.  It is located in the large
reflection nebula, NGC 7023; there is a beautiful photograph of the
nebula in the February Gallery section of Sky and Telescope; V380 is
the brightest star in the field.  There is only one observation of it
I could find in the AAVSO database.

   In the recent past, it has exhibited variations in V<=0.2 mag.;
the historical range in V is 7.24-7.48.

   In an August, 1998, PASP paper, Miroshnichenko et al report a
3.68 year period in the variation of the H-alpha line equivalent
widths (EWs).  They report that during the last H-alpha 'high state',
in 1997, the emission-line EWs were at their highest levels (by about
50%) in 20 years. The H-alpha EW "light-curve" also shows a secular
trend towards higher values.

   Miroshnichenko et al state that historically high H-alpha EWs 
may occur in May of this year, perhaps exceeding the historical
maximum, sometime October of 2000 and May of this year.

   They also report that photometry since 1983 shows evidence of a 
positive correlation between the H-alpha EW and the visual 
luminosity.  If the long-term trend of increasing EWs continues,
V380 Cep may exceed its historical *visual* maximum as well this 
year.

   It's not known when maximum light will occur, and visual observers
may help pin that down.  It may be an eclipsing binary in which the
photometric variations can be seen only during an H-alpha
high-state.  The luminosity variations may also be due solely to
interactions of the circumstellar matter with the star(s).  In
either case, it is important to determine any periodicity present
in the luminosity variation.  (I've often wondered if something
akin to CV "superhumps" might be observed in Be stars.)

   V380 Cep may also be a spectroscopic binary, although the
evidence is weak.  The radial velocities are strongly variable,
but with no clear-cut periodicity.

   Visual and PEP observers stand a good chance of catching it in
some interesting antics this year.  (To my knowledge, PEP has been
done in the recent past only in Central Europe.)  Observers at
latitudes north of about +40can best observe it all year, and
it is circumpolar north of +22

   Miroshnichenko emphasizes the importance of both high-res
spectroscopy and precision photometry during this time.


Clear skies,
Thom Gandet

   
-- 
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                      Lizard Hollow Observatory
                        Thom Gandet, Director
                            PO Box 77021                   
                      Tucson, AZ 85703-7021  USA
              www.azstarnet.com/~tgandet/lizard_hollow.htm
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