Re: V455 And - fading?

From: Joe Patterson <*jop_at_astro.columbia.edu*> Date: Sun, 23 Sep 2007 05:44:16 -0400 · jop_at_astro.columbia.edu

Hi CBAers,

Looking at Arto's long light curve from last night, I'd guess what he 
guesses - that the fading may well signify the "end of the outburst".
Data from the western USA will test this further. In all likelihood, 
what this really means is "the end of the slow linear decline from 
supermaximum".  Everything so far - including the properties at 
quiescence - is an awfully good match to WZ Sge; so if we take that star 
as a guide, we might expect now...

* a 1-2 magnitude fast drop (happening in <2 days);
* then a few "echo outbursts" - fast rises followed by fast declines -
   over the following 2 weeks;
* then a very slow decline - over a year or more - to quiescence at mag
   16.5.

These echo outbursts are still very dimly (at best!) understood.  They 
weren't quite recognized until 1997, and probably only WZ Sge-type dwarf 
novae show them.  And they're short-lived.  So there's not much data on 
them... and especially little data on how the orbital light curves are 
affected by these fast 1-2 mag ramps in the eruption light curve.  With 
the emphasis on FAST - the eruption rises in echo outbursts are as fast 
as 6 hrs or so.  So keep up the watch!

Now that some of you have invested some time in designing a system for 
doing faster photometry, I strongly recommend doing some trial runs on
DQ Herculis and RX1730-05.  These stars are a lot fainter than V455 And
(respectively 14.7 and 16.3), but they have fairly strong fast periodic 
signals - near 70 s.  We've been studying those signals for years, so I 
can make a pretty good evaluation of your results.  You can evaluate 
them yourself too, using period-analysis software such as Tonny's 
PERANSO (which many of my students use, by the way).  Plus we need 
late-season pulse timings on both stars... plus they don't require a lot 
of observing time (a 2-hour run is fine if conditions are decent).

Whew... hard work keeping up with all this!  The last great 
superoutbursts (EG Cnc in Dec 97 and WZ Sge in Jul 01) happened during 
winter and summer vacations - definitely the preferred time for all
this heart-attack-per-minute activity.  And echo outbursts, if they 
occur, are not so easy on the nervous system either.  Should settle down 
in a month or so.

Then we can rest.

Ha, ha, ha.

joe