[vsnet-chat 1954] periodicity search in Nova Vel 1999 and V4444 Sgr (Re: [vsnet-alert 3081])

[Alon Retter <ar@astro.keele.ac.uk>]

Dear vsneters,

According to our experience with young nova (we actually found
periodicities in 8 out of 9 young novae), the relevant parameter is not 
the time after outburst, but the decline rate. If the nova is a very 
fast one, periodicity can be found very shortly after eruption. The 
record is Nova V838 Her 1991. Leibowitz et al. (1992, Ap.J., 385, L49)
found eclipses in this system from about 3 weeks after outburst. This 
was a very fast nova (t2~2 day). The variations were detected ~7
magnitudes below the maximum brightness. Periodicities can be found 
from ~4-5 magnitudes below maximum flux, only after the common
envelope phase is over, and the binary system is resolved.

Apropos Nova Vel 1999, this phase is reaching fast. The maximum was
mV~2.5, and recent reports are mV~6.2, so I recommend to start search
for periodicities very soon.

Same is true for Nova V4444 Sgr 1999. It reached a maximum of
mV~7.5, and current estimates are mV~12.5. At the moment, it is 
therefore a better candidate for periodicity search than Nova Vel 
1999, but it is much fainter.

Let me also express the importance of finding periodicities in the
light curve of young novae. It can help to classify the nova into
the different types of CVs, and it can help in understanding the
inter relationship and evolution of CVs. This was expressed in
Nova V1974 Cyg 1992 (Retter \& Leibowitz, 1998, MNRAS, 296, L37). 
When the novae fade, they are naturally much harder to be observed.

Good luck!
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           'As a scientist I don't believe myself, so
   ST5 5BG, U.K.            why should I believe you?' (A.R. 1965-2085)
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On Tue, 8 Jun 1999, Daisaku Nogami wrote:

> Hi,
> 
> I do neither know time-resolved photometry which
> detected short-term variations in novae at the phase,
> about 10 days after the maximum, nor a thoery predicting 
> such modulations.  However, you may become the first
> man to succeed it :-)
> 
> Does anyone have comments?
> 
> Best regards,
> Daisaku Nogami
> 
>  From: Gordon Garradd <loomberah@ozemail.com.au>
>  To: "'Daisaku Nogami'" <nogami@kusastro.kyoto-u.ac.jp>
>  Subject: RE: [vsnet-alert 3081] (fwd) An ASCA Observation of Nova Vel 1999
>  Date: Mon, 7 Jun 1999 22:21:31 -0000
> 
>  > Is unfiltered time-series photometry useful?
>  > 
>  > Cheers, Gordon
>  > Loomberah, Australia
>  > 
>  > >>While the success or otherwise of the ASCA observation does not
>  > depend directly on coordinated observations, it will obviously
>  > be useful to have contemporaneous optical and IR observations ---
>  > particularly spectroscopy --- to probe the nova ejecta at multiple
>  > wavelengths.  
>

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