[vsnet-chat 993] Nova Oph 1998 fading

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

On Wed, 24 Jun 1998, Taichi Kato wrote:

> Nova Oph 1998 fading
> 
>      Has anyone experienced such a rapid fading (2 mag in 2.8 days) in
> classical novae?  What was the apparent plateau (Jun. 18-20) before this
> fading?  Does anyone have an idea?
> 
> Regards,
> Taichi Kato
> 
Dear Dr. Kato,

To my knowledge, this behaviour is very unique.

For Nova V838 Her 1991, it was found that t2=1.2 d, and t3=3 d 
(Warner's book 1995), but it was soon after the outburst.

In the light curve of Nova V1974 Cygni 1992 (Retter & Leibowitz, 1998
MNRAS, 297, L37), one can notice 3 different slopes. We believe that the
first one is due to the contraction of the common envelope, the second
might be related with the decay in the white dwarf light and the third 
should be connected with the accretion disc. 

According to this suggestion, in Nova Oph 98, the common envelope phase
has been finished, and now we observe the cooling of the white dwarf.
However, it looks odd that the light from the white dwarf decreased so
quickly. So, another (better-?) explanation is that there was a phase of
constant ejection of matter (the plateau), which suddenly stopped.

Anyway, observations are highly recommended. If the nova enters the
'binary phase', an irradiation effect might be revealed, so continuous
photometry could be fruitful.

Regards,
Alon Retter

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