[vsnet-chat 7287] Re: Prioritizing CV targets

[Daisaku NOGAMI]

Dear Mike, and other colleagues around the world,

Thank you very much, Mike, for giving us the seeds of interesting
discussion!  While Boris, Coel, and Steve have already made nice
comments on this topic as pros, please let me add some of my personal
thought.

As all of them mentioned, all types of CVs, such as, U Gem stars,
Z Cam stars, nova-likes including SW Sex stars and VW Scl stars,
polars, intermediate polars, and novae, are definately worthwhile
to be monitored.  And those observations must give basic information
on the physics of the accretion phenomenon, the evolutions, and so
on.  For a recent example, a peculiar behavior of Z Cam currently
ongoing was reported in vsnet-obs (54554) (together with T UMi's
peculiar light curve).  This curious light curve of Z Cam can not
be explained simply by a decrease/increase of the mass transfer rate,
probably.  The brightening of UZ For and the outburst of RS Oph are
other recent examples.

The reason why SU UMa stars seem to have a high priority against
CV of the other types is the immediate rewards, I think, as Coel
already mentioned.  Several days time-series observations during
a long outburst of an unknow-type dwarf nova can detect superhumps,
which is evidence of the SU UMa nature of this star.  Since SU UMa
stars generally have short orbital periods below 3 hours, it is easy
to accurately measure the superhump period.  If both of the superhump
period and the orbital period are known, we can deduce the evolutional
status of that star.  Rebrightenings after superoutbursts, time
derivatives of the superhump period, and the transition from the early
superhump to the genuine superhump in WZ Sge stars are presently hot
topics.  We can observe these phenomena by a simple method, unfiltered
time-series photometry, which amateurs having CCDs can easily carry
out.  I believe that these are ones of most significant astrophysical
topics to which amateurs can make good contributions without
unreasonable efforts.

This does never mean, of course, that importance of daily observations
of other types CVs and other types of variables objects has decreased,
as I noted above.  Steve wrote, ``CVs are fun, always have been and
always will be!''.  I strongly agree.  Other variables objects, such as
pulsating stars, eclipsing stars, flare stars, pre-mail sequence stars,
X-ray binaries, and GRB afterglows are fun, too!  I personally pay
much attention to an X-ray binary V4641 Sgr in the coming season :)

Best regards,
Daisaku Nogami