[vsnet-chat 7286] Re: Prioritizing CV targets

[Berto Monard]

Mike,

The mere fact that you reached that cross point and started looking around (from the hill top), means that you will still have a lot of excitement coming your way.

There are many things that you can do with a CCD, even when you decide sticking to CV observing only.

As long you also carry on with visual CV spotting (I wonder how long that will be...), you can also be the first to investigate light curves of freshly erupting CVs with not much history by means of timeseries photometry (one filter only or none). S/outbursting UGSU systems require a couple of nights before they show s/humps. But then, when did the outburst really start and how will the transition light curve look? This was not spelled out by the pros in their reply. I believe there can be something learned from the transition light curve...

Now, the problem of which CVs are worthwhile working on? I would say that after many years of CV observing you ought to know the answer to that... Unstudied systems, or rare eruptors specifically (but not exclusively so) those with no known Porb are exciting targets for photometric time studies if they get bright. But there is more than one reason why certain CVs have no known Porb..

Re the different types of CVs etc.. you will find in time which ones give you the most satisfaction. Replies from professional astrophysicists did stress important facts and I am not in a position to comment at the same level of scientific insight.  I therefore rather stick to comments resulting from my observing experience. Many CVs in the CV Atlas are not much known of. A mere 'cv' classification indicates that. Other CVs from the atlas (whichever CV category) will turn out to be non-cv, wrongly CV classified, constant or with an incorrect position. And don't make a mistake: the CV atlas reflects present knowledge.

All amateur efforts to check up on the lesser known CV stars wrt light curve, Porb, classification, location of the suspect CV in the given field etc .. will not only be scientifically valuable but will give you satisfaction or fun if you like. Admittedly a CCD camera will help you enormously with this for its observing depth and archiveable value. 

Filtered vs unfiltered: depends on what you want to achieve. Accurate light curves vs discovery perhaps
Most faint CVs might not be picked up by filtered CCD cameras through a small scope. Just consider a typical magnitude loss of just under 2 mag for a V filter and 1.5 mag for a R filter. Indirectly put, it is a matter of accuracy vs precision (S/N mainly).

IMO the following are projects that can do a lot for you and science:

* Timeseries photometry of very long duration (>10h) could just reveal a Porb which would otherwise take many nights and different timezones. Most professional observing sessions on CVs are of much shorter duration. 

* Snapshot monitoring of faint CVs (all types) over long periods as often you can do them. This will take a lot of time and effort but they will provide answers. Regularly you will find some of them much brighter than shown in the literature (CV atlas ..). Note that most faint CVs are beyound magnitude 18.5 most of the time. If you use a V filter you will not see them. Also note that many quiescent CVs have a red colour due to the dominating light of the secondary and not much accretioin flow, or due to reddening (MW regions). Those you will never see unless you go unfiltered (and see them with the red/IR tail of the CCD response spectrum / note that you could do those with I filters but considering the observing time constraints that (not only) amateurs have...). In this case forget about accuracy meant for data bases but you will be able to get an idea of the brightness evolution of those CVs and at times spot increased activity / outbursts. 
I can go on writing on this specific project as I am involved with one and honestly timewise I cannot cope with the observing frequency I was set out to do, but mainly because I observe other targets.


* Other interesting (CCD) observing programs are beyound CV except these two:
   - Snapshot monitoring of known and suspected symbiotic stars. They are not in the CV atlas, but strictly spoken (arguably) they are part of the CV family. A number of those Z Ands have no certain identifications or counterparts. You might pick them up by imaging them regularly (at least the sky region they are residing in). I got valuable assistance from B Skiff wrt positions and possible identifications at the time I started out with that. Probably northern Z And stars are better archived. There are also less of them, unfortunately for the majority of observers. Is someone involved with such a project now?
Some of those stars are eclipsing but nobody knows that except the observer of such a program. I am looking forward to write about my findings at a later stage.
  - Follow up on X ray transients: this has been a favorite of mine years ago, even during my 'visual' years. As mentioned by one of the professional astronomers, these are potential CVs. Some of these alerted objects will have relatively bright counterparts during the active phase. As I found out filtered CCD observations might give better results in dense (MW, reddened) star regions. Most efforts however turn out negative or at least uncertain.


It might not have directly answered your questions, Mike, but hope that the above might help you (and hopefully others) somewhat in deciding the way forward. Some of what I wrote might be chaotic (reflecting the writer perhaps), but do whatever orderly observing suits you.

Let me therefore also state the importance of participation in directed observing campaigns: complementing satellite observations (usually AAVSO and VSNET), TOO observing campaigns with often expert guidance of professional astronomers (VSNET, CBA) and directed observing studies of specific targets under leadership of a dedicated professiona CV expert (CBA). I might have left out CV observing programs directed by other organisations like BAA and others of which I do not know much off, as they mainly deal with the northern sky. 


Any eventual offence, insult or oversight in the above must be accepted as unintentional from my side. I have not put in as much time into this as I would have liked. There is a lot of 'work' load waiting in my professional capacity here. Yes, I wrote this during 'work' time...


With my best regards and well meant wishes to all observers,

Berto Monard
Bronberg Observatory / CBA Pretoria 


 

 
 

>>> "Mike Simonsen" <mikesimonsen at mindspring.com> 08/03/2006 07:54 >>>
I'm sure I'm not the only one who has come to this point in their
development as an observer, so I would like to share my feelings and
questions, and hopefully spark some relevant discussion.

Besides the numerous list servers in the header, I am blind CCing many
professional astronomers in hopes that they will respond.

When I first began observing CVs to the near exclusion of all other kinds of
variables there was not a lot known about many, or most, of the CVs we were
monitoring. Many were newly discovered and even the type was not known for
sure. Some had never been seen in outburst. A lot has changed in this regard
in the last few years.

Preferential treatment has obviously been given to UGSU types. Detecting
superhumps and deriving a period has been the main game in town in this
regard. In fact, it seems nobody is interested if the long wait for an
outburst ends up revealing a 'mere UGSS'. Cases in point, the recent
outburst of CI Gem and the last two outbursts of DK Cas. Once no humping was
found they were basically ignored.

Question #1- is there no interesting science to be gleaned from UGs or UGSS?
If not, why are so many papers and investigations done on SS Cyg and U Gem?

Question #2- is the reason superhump recognition and period 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?

Question#3- if you insist on working unfiltered, aren't there a bunch of CVs
with no known period that you could work on in quiescence to determine the
period?

I just wonder at the usefulness of jumping all over every new ASAS variable
to see if it is a UGSU or not and then leaving the whole thing at that. Its
kinda like the current situation with novae. What is to be learned by
following yet another novae from outburst to quiescence? OK, its a
nova...big deal.

As an amateur I would appreciate a little direction in this regard. With
more and more surveys coming online there will be more and more CVs, novae
and SN discovered, and we need a way to separate the wheat from the chaff.
Certainly a million new W UMa eclipsers will be uncovered, but who cares?
Maybe one or three will prove of interest. I think it is the same with CVs
and novae.

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".

Question #4- isn't there a way to pre-determine the probability somewhat?
I don't have an answer. Maybe it takes tools, like spectroscopy, beyond our
means to make that determination.

For visual observers the situation is still much the same as it has been. We
are the fire spotters. We patiently monitor CVs for years that may or may
not prove to be of interest, depending on whether they do the superhump
dance once they go off. But what of the ones we have now alerted the world
to that have had their 'superhumpness' or not and periods determined.

Question #5- is there a valid scientific reason for continued monitoring?

Maybe the emerging role of visual observers is to continue monitoring the
stars with the oldest historical light curves. These 'legacy stars' may show
period changes or surprises in human time scales we are not expecting, and
it will be the visual observers who catch these changes, not surveys with
limited life spans or superhump CCD observers who only observe these stars
for a few hours on a few nights and then move on.

One of the most interesting things any professional has said in a CVnet
interview was when Joe Patterson said, "The dwarf-nova outburst itself has
become generally well understood -- in the sense that there's a theory which
successfully reproduces the observed phenomena.  But it's noteworthy that
all of that theory was crafted to fit previously known data -- it has never
actually predicted something not known in advance. So that higher standard
of scientific worthiness has never been met.  In addition, the theory breaks
down when applied to dwarf novae in quiescence -- it predicts about a
thousand times less accretion than is actually observed!  Plenty of thought
needed there."

Clearly we could all use some help. Isn't there a way we can help each other
(pro/am) more? When I founded CVnet I was hoping for more professional
guidance and participation than we ended up getting. I'd have to say that is
the only disappointment after the first year. There are a few generous and
gracious pros who have contributed, and we all appreciate their
contributions. I am doing what I can to expand on this facet of CVnet.

As a visual observer who now has his other foot in the CCD game, I want to
do the best and most relevant science both visually and with the CCD. I'd
like to keep monitoring the CVs that are active and fairly bright visually,
making as many positive observations as possible, as well as the long term
projects like waiting for PQ And or EG Cnc (or RS Oph for that matter!) to
go off. I rather regard my CV program much like an ornithologist with a
'life list'. There are a number of CVs I just want to SEE before I go. I
don't care if they are particularly scientifically relevant. Its a hobby for
me, and I can wait and monitor what ever I want, enjoying the view, the
solitude and the oneness with the universe I feel when I am out at the
scope.

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.

"Build it and they will come."
>From 'Field of Dreams', the movie.


Mike Simonsen

*********************************
C. E. Scovil Observatory
http://home.mindspring.com/~mikesimonsen/ 
AAVSO Chart Team
charts at aavso.org 
CVnet Administrator
http://cvnet.aavso.org 

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