[vsnet-alert 119] AL Com light curve to date

[Steve Howell <howell@PSI.EDU>]

The Belgian Astronomical Society recently sent out its CVC 34.
This contains a record of mostly visual observations of AL Com 
during its current outburst.

The data listed in this circular has two pre-maximum points .
These are very interesting as one they are unusual to have for any outburst,
but also, they show that AL Com was far above its minimum value 
(near V~21) a few days before its maximum light. This type of behaviour
has been suspected by some and indeed was recently modeled in APJ 1995
Vol 439, p. 337 for outbursts of TOADS. So I thank the observers for these
data in particular.

Also, we note that the recently reported SH period (by Kato and Nogami 13
April 1995) gives a period of 0.05666 days. Using the relationship 
given in Howell and Hurst (IBVS 4043) this would predict an orbital priod
of 0.05466 days for AL Com. These periods in minutes are 81.6 and 78
respectively.

Patterson reported a period of 81.8 min observed on 5/6 April 1995.
This was before maximum light and is not equal to the superhump period
reported by Kato and Nogami. However, Pattersons period is within the errors of 
the period of 84 minutes discovered by Howell and Szkody (IBVS 3653),
which they attributed to the orbital period of the system.

Thus, AL Com's periods still remain somewhat of a mystery and we are
still in need of a radial velocity study at minimum. I can tell you from
personnal experience, that Telescope allocation commitees, do not like
giving away 4-m time to get a period for a star. ;-))

Cheers,
Steve Howell

 Steve B. Howell 
 Planetary Science Institute, Astrophysics Group 
 620 N. 6th Ave. 
 Tucson, AZ 85705  USA 
 Phone (520) 622-6300 
 Fax (520) 622-8060 
 e-mail: howell@frankenstein.psi.edu 
 homepage: http://vsnet.psi.edu/

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