[Aavso-photometry] Fw: [cvnet-outburst] GW Lib info

[Mike Simonsen]

----- Original Message ----- 
From: <t.r.marsh at warwick.ac.uk>
To: <cvnet-outburst at yahoogroups.com>
Sent: Saturday, April 14, 2007 4:26 PM
Subject: [cvnet-outburst] GW Lib info


>
> Dear All,
>
> I was going through all the e-mails on the GW Lib outburst
> (a really great discovery!) and although Akira Imada's message
> contains relevant references, I did not find any that specifically
> mention why this star is especially interesting, so I thought
> I would say so myself to urge good coverage of this rare outburst.
> This is also why I am submitting this to cvnet-outburst rather than the
> discussion list.
>
> GW Lib is the first CV in which the white dwarf was found to be pulsating
> from what are called "non-radial oscillations", somewhat similar to the 5
> minute oscillations seen in the Sun. Such pulsating white dwarfs are known
> amongst the isolated white dwarfs where they are called as ZZ Ceti stars,
> and can allow us to probe the interiors of the stars. There are still only
> a handful of CVs known to harbour ZZ Ceti-type white dwarfs. ZZ Ceti
> pulsations only occur when the surface temperature of the white dwarfs
> lies in a rather restricted range around 11,000 K, although those in
> CVs seems to be able to pulsate at hotter temperatures, perhaps due to
> the accretion of helium-rich material. A very exciting feature of the GW
> Lib outburst is that it may heat the white dwarf up so much that the
> pulsations switch off only to come back as the white dwarf cools. It would
> be really wonderful if we can manage to see this. This will require time
> series photometry once GW Lib returns towards quiescence. This is probably
only
> feasible on large telescopes because the pulsation amplitudes are small
> and several os us are looking into this possibility, but I hope people can
> observe it fairly frequently throughout this outburst so that we can track
> the progress towards quiescence as well as spot superhumps, echo outbursts
> and all the other weird and wonderful things these stars can do,
>
> I wish everyone clear skies,
>
> Tom
>
>
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