[vsnet-alert 1074] (fwd) V1974 Cyg Campaign (Retter)

[Taichi Kato <tkato@kusastro.kyoto-u.ac.jp>]

From owner-vsnet@kusastro.kyoto-u.ac.jp Tue Jul 22 21:23 JST 1997
Date: Tue, 22 Jul 1997 15:16:08 +0300
From: Alon Retter <alon@wise.tau.ac.il>
To: vsnet@kusastro.kyoto-u.ac.jp, is@sirius.astrouw.edu.pl,
        dey@herschel.usno.navy.mil, jop@tristram.phys.columbia.edu
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Subject: [vsnet 1073] Nova V1974 Cyg 1992 - Call for observations
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Dear vsneters,

We are planning a campaign on Nova Cyg 1992 during the next few months
(July to December), and we are looking for collaborators from other
observatories.  The nova was about Mv=15.8 in May, and its recent decay
rate has been about 0.5 mag/year. Its estimated visual mag. during the
next few months is therefore 16.

In the last 3 years this system had permanent superhumps with a period
of 2.04 hr (Skillman et al. 1997, PASP, 109, 114 ; Retter, Leibowitz,
and Ofek, 1997, MNRAS, 283, 745). The peak-to-peak amplitude of the
superhump is about 7%, but with the orbital variation it is sometimes
double this value.

We would like to check the following issues:

1. The change in the superhump period. It decreased during 1994,
   and increased during 1995 and 1996. This trend might be reversed 
   during 1997.
2. A possible decrease in the orbital period. Semeniuk et al. 1996, 
   Acta Astro. 46, 311 and Skillman et al. 1997 detected a very small 
   decrease in the 1.95 hr orbital period, however it might be explained 
   by a phase shift of the variation.
3. Simple calculations lead to the prediction that the permanent 
   superhumps will cease when the nova magnitude reaches an upper limit 
   of about 17.5-18.5 (it could happen before). We would like to check 
   the evolution of the superhumps as the nova magnitude approaches 
   this value, which corresponds to some critical value of the mass 
   transfer rate M-dot.
 
   This is the first time that we may have an opportunity to follow
   observationally such developments in a classical nova, which  makes
   V1974 Cyg a particularly interesting target.

The Wise Observatory and Kyoto Observatory (Katsura Matsumoto and
Taichi Kato) give it a high priority. The CBA group (J. Patterson) also
has started to observe this star, and will be back from the summer
holiday in September with more telescopes.

If you're interested in joining this campaign, please contact Alon
Retter (alon@wise1.tau.ac.il). Since the period is short, even a 2-hr
run will be helpful.


Alon Retter and Elia Leibowitz
Wise Observatory

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