h=Received:Message-ID:From:To:Cc:Subject:Date:MIME-Version:Content-Type:Content-Transfer-Encoding:X-Priority:X-MSMail-Priority:X-Mailer:X-MimeOLE:X-ELNK-Trace:X-Originating-IP;
Received: from [4.229.111.90] (helo=computer)
From: "Mike Simonsen" <mikesimonsen
Date: Wed, 8 Mar 2006 17:38:05 -0500
Cc: AVSON

Coel Hellier sent this response to "Prioritizing CV targets".


Dear Mike,
   I've written the enclosed reply to your questions.
Feel free to send it to the various mailing lists if
you wish.
      Coel.
=============================================================

UGSS?
> If not, why are so many papers and investigations done on SS Cyg and U
Gem?

Yes, there is interesting science to be done with UGs and UGSSs.
However, the basics of UG lightcurves are now fairly well known
and it is not at all clear how to make further progress in
understanding with new lightcurves.  In this sense, science is
"the art of the possible".  There is still worth in gaining new
lightcurves in case something unusual happens or in case the
accumulation reveals something new, but there may be little

In the case of UGSU there is an immediate reward in the form
of a tangible number (the superhump period and often the
period excess, epsilon) and also there is a clear path to using
epsilon values to learn about CV evolution (see papers by
Joe Patterson etal).

Also, as Boris pointed out, there is a lot of useful stuff to
be done on CVs that fade rather than brighten (VY Scls, SW Sexs,
IPs, polars) but for obvious reasons good data is harder to acquire.
But if garden UGs are well studied, and you have the capability
to go deeper, these "fading" classes would be rewarding.

> determination is so popular is because it can be done unfiltered?
> Isn't there more science that can be done by placing UBVRI filters on
> CCDs while investigating CVs?

A single colour is unlikely to gain you much that white
light won't give you.  But cycling filters is problematic
in CVs because you have to disentangle colour information
from changes due to the ubiquitous flickering.  Ideally one
needs several colours simultaneously, but that is likely
beyond most amateur equipment.

> of CVs with no known period that you could work on in quiescence to
> determine the period?

Yes, but again they tend to be fainter (bright ones tend to
have been done).  Recently Patrick Woudt, Brian Warner and
Retha Pretorius have produced a series of papers on fainter,
less studied CVs, which shows that there is a lot of interest
equipment beyond that of most amateurs, but with decent
amateur equipment the less studied stars could be rewarding.

> One argument must surely be, "if we don't study each one to a certain
> extent how will we know which ones will prove interesting".
>
> somewhat?  I don't have an answer. Maybe it takes tools, like
> spectroscopy, beyond our means to make that determination.

Yes, there are ways. For example something detected in
(I'm showing my biases here!).   But predicting the
unexpected can be a little tricky.

> But what of the ones we have now alerted the world to that
> have had their 'superhumpness' or not and periods determined.
>
> monitoring?

of CVs is one of the essential foundations of our understanding.
It may be that at some point amateur observations will be
there yet, and even when we are there we'll need a period
of overlap to allow us to normalize the different datasets.

So, yes, there is value in monitoring CVs, even the
"less interesting" ones that aren't superhumping or
but it might not be all that tangible in terms of
specific papers.

> On the other hand, I started doing variable star observing because I
> wanted to contribute to science. There are a bunch of us out here with
> talent, enthusiasm, time, money and expertise who want to do good
> things. Show us the way and we will follow. Empower us and we will
> amaze you.

As I'm sure everyone is aware, the CBA is an excellent
example of this working very successfully.  So maybe
your question is whether there should be an equivalent
for visual observations and for monitoring snapshots
(rather than the long runs that the CBA specialise
in).

I'm not sure of the answer.  To some extent there is
value in amateurs all doing their own thing and not
planning it too carefully, simply because that means
that the unexpected is more likely to be spotted.

But it is probably the case that more direction
would be worthwhile.  If the current generation of
amateurs, with increasingly good equipment, can get
of the same quality that the previous generation
has done with high states, then that would be highly
worthwhile.

          Coel Hellier



_______________________________________________