[vsnet-campaign-nova 1109] Re: V697 Sco: an IP?

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

On Tue, 22 Oct 2002, Taichi Kato wrote:

> V697 Sco: an IP?
> 
>    Back to an old issue.  V697 Sco (Nova Sco 1941) has been proposed to be
> an intermediate polar.  This nova did not show apparent oscillations.
> Does this observation imply that IPs and nova oscillations are not
> related (?) > Any comments, Alon?
 
Dear Dr. Kato,

Thank you for attacking my idea. This is the only way our argument could
be settled. It is obvious that the idea that the transition phase in novae
is connected with IPs could be completely wrong, but you have certainly
not shown it. 

V697 Sco is a southern nova from 1941, which was discovered when it
reached V=10.2. How many visual measurements of the nova were made??? Did
the vsnet exist these days??? Did observers have CCDs then??? How many
southern amateurs observe novae in 1941??? I didn't bother to check its
light curve. You are most welcome to do it, but I would bet that the
measurements are not sufficient to determine whether the light curve shows
transition phase oscillations. 

In addition, if you have read my papers, you should have noticed that I
suggest that the properties of the transition phase may be connected with
the spin period. DQ Her systems with shorter spin periods (say a few
minutes)  would have more dust and a deep minimum in the light curve. 
Novae with longer spin periods (~tens of minutes) will have oscillations,
and those with the largest spin periods (~few hours) would only have small
indication of dust (e.g. Nova V1425 Aql 1995). The physics behind this
behaviour is that in systems with longer spin periods the inner part of
the disc is more truncated (they have a bigger hole) thus the interaction
between the reformed truncated (less massive) accretion disc with the
magnetosphere of the white dwarf is less violent. According to Warner &
Woudt, V697 Sco has a very long spin period (3.3 h), so it is a discless
system. I would thus not expect oscillations during the transition phase
at all, perhaps only some minor indication of dust. 

I believe that my idea could be refuted by new data. Old data are too
scarce. And again, I may be wrong, but the idea is very simple, it is
consistent with the observations, it gives a natural explanation to the
question `why certain novae show oscillations while other don't?', it
explains nicely why the ratio of IPs / CVs is very similar to the ratio:
transition phase novae / all novae, and it looks as if its predictions
have become true in several case. 

Regards,
Alon
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