Re: (no subject)

From: Joe Patterson <*jop_at_astro.columbia.edu*> Date: Wed, 18 Nov 2009 01:47:42 -0500 · jop_at_astro.columbia.edu

> 
> Do you have any arm chair thoughts on the behavior of TT Ari?

A few... they're bound to improve in the coming weeks.

> 
> Some questions that come to mind are has this family of CV's ever been
> extensively examined at quiescence for similar behavior?

No, most of these stars are too faint at quiescence... and the episodes 
can't be planned for, so you have to get lucky.  The one halfway 
exception is MV Lyr.  Robinson et al. wrote an excellent paper on the 
1980-1 minimum... which showed that the light curve was occasionally 
still, and occasionally showed some flickering.  Some precedent there - 
but not much detail (really just a few hours, total, of photometry).

> 
> I have noticed in the light curves leading up to the brightening that it
> "ramps" up and then falls precipitously.
> 

Yes, I think so. Somewhat common pattern... energy released fast, then 
cooling.

> What can be determined from the GALEX and Swift observations? It appears
> that the photon data from GALEX is not available from the MAST site, can you
> get this and look at correlations, if so what do those correlations
> indicate.

It's very likely that the orbital modulation (the slow wave you see at 
V=16.3) is the aspect of the heated secondary as it wheels around the 
WD.  The WD is hot/luminous enough to produce the heating.  In 
principle, Galex will give us the temperature of the WD (most of its 
flux is likely to be in the UV).  The amplitude of the wave can 
constrain the luminosity (subject to uncertainty in inclination), and 
then L=4piR**2sigmaT**4 gives us the radius, therefore the mass, of the 
WD.  Hallelujah.  In an ideal world.

BTW I'm not sure about the photon data; I'll dig deeper for that.

In the UV we at least approximately know what we'll see: a hot WD.  But 
in the X-ray, no one's taking bets.  It's pretty much a bare WD, that 
had an illustrious accretion past, and will soon rise again.  Will that 
mean... no X-rays at all?  Or is there some other accretion mode that 
can channel matter onto the white dwarf without releasing energy in a 
disk?  So it would be GREAT if some of our 25 ksec was at pure 
quiescence, and some was during the flares.

Another beautiful night in AZ.  I'm flying back tomorrow, so will be 
chat-silent for at least a day.

joe