[vsnet-campaign-nova 845] Nova V1039 Cen 2001 - possible periodicity

[Alon Retter <retter@Physics.usyd.edu.au>]

Dear southern vsneters,

Continuous CCD photometry carried out by Marc Bos (Mt Molehill
Observatory) during 5 hours on Monday (18/2/2) with no filter
shows nearly 3 cycles of a ~1.7-h modulation with a full amplitude 
of ~0.05 mag. More observations are strongly encouraged to confirm 
the presence of the possible periodicity. There are a few other 
weak signals at higher frequencies but below the detection limit. 
This result may be very significant.  

If confirmed, the 1.7-h period can have 3 simple interpretations:

1. Orbital period (however, there are only 3-4 known novae with
   orbital periods below the period gap (below ~2 h), so it is 
   quite interesting. In comparison, there are ~50 novae with 
   orbital periods > 3 h.

2. Superhump period (positive or negative superhump). In this case 
   the orbital period, would be very close to ~1.7 h (a few percent 
   shorter/longer). More data may show 1-2 more periods (the 
   orbital period and the other type of superhump).

3. Spin period. According to my untrustable memory the longest spin 
   period known in intermediate polars is ~1.1 h, although there are 
   two candidates with longer periods (~1.5 h, ~2 h). So, V1039 Cen 
   is at the top of this range. In this case, another longer period
   (the orbital period) may be discovered with more data. I expect a
    period of ~5-7 h in this case. Other periods, which result from 
    various combinations of the two periods may be discovered as well.

There are actually a few other possibilities with lower chances, that 
I prefer not to mention here.

Option 3 would probably support my suggestion for a correlation between
the transition phase in novae and intermediate polars as V1039 Cen seem
to have had a few long-term oscillations with full amplitude of ~1 mag.
Options 1+2 still don't kill this idea as spin periods are best seen in
the X-Ray, not the optical. Thus, we need an X-Ray run - probably with
Chandra. Your result will sure help writing the proposal in plan. 

Regards,
Alon
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   Dr. Alon Retter          Tel. (work)     +44-(0)1782-58-3493
   Physics Dept.            Fax  (work)     +44-(0)1782-711093
   Keele University         -----------------------------------
   Staffordshire, ST5 5BG   'As a scientist I don't believe myself, so
   U.K.                     why should I believe you?' (A.R. 1965-2085)
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