[vsnet-chat 4929] Re: new southern variables

[Fraser Farrell <fraser@trilobytes.com.au>]

Vello,

So discovering C/1996 Q1 and C/1997 N1 wasn't enough for you? Now you have to 
find hundreds of apparently unknown southern variables as well?  Bugga...what 
does that leave for the rest of us to find?  ;-)

Seriously, I was fascinated by your results so far, so I'm taking the liberty 
of CCing this to VSNET and a few other people who may be interested. Your 
entire original message is therefore appended for the benefit of those other 
readers; and I expect you will get other responses than what follows.

And have you considered presenting this work at the next NACAA?

- - - -

You probably know already that the GCVS + NSV + HIPP are not complete for 
variable stars. And in the case of the GCVS some of the numbers are as dodgey 
as the last Federal Budget. The definitive and actively maintained versions 
of the GCVS & NSV and their supplements are available online at:  
http://vsnet.sai.msu.su/groups/cluster/gcvs/gcvs/

For variables brighter than ~12 I would also check out the Tycho Catalogue's 
variable stars annex, the Catalogue of Cool Carbon Stars, the S Stars 
catalogue, the Cataclysmic Variables lists, and the IRAS and MSX/MSX5C 
sources. All of these are available through the CDS Vizier catalogue 
collection at:  http://vizier.u-strasbg.fr/   where you will also find 
thousands of other catalogues for all sorts of Things Out There (including 
the latest GCVS etc if the Russians are offline).

The CDS also runs the SIMBAD database at:  http://simbad.u-strasbg.fr/Simbad  
 SIMBAD is brilliant for queries like "list all known objects within X 
arcminutes of ..." and "show me references for this object". For example a 
public access query on my favourite Very Red Star DY Cru returned eight 
catalogued names, 11 literature abstracts and a finder chart. If you need 
full access to SIMBAD send an email to the managers explaining who you are 
and what you do. Worked for me, even though I haven't discovered any comets 
;-)

The IBVS is another place to look. Thousands of issues are available online 
at:  http://vsnet.konkoly.hu/IBVS/   Typical IBVS articles announce discoveries 
of new variables, significant observations of known variables, updates to 
catalogue data etc. The editorial policy is to keep 'em short & sweet. Plenty 
of amateur contributors too.

And I should mention VSNET itself at:  
http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/  Their mailing list archive contains 
vast amounts of info and (fortunately) it is searchable online. You can also 
subscribe to any of a zillion mailing lists - but be warned the traffic on 
some of them is immense!

- - - -

I note that your CCD survey is optimised for comet-hunting and the variable 
star info is a byproduct. Nevertheless I'm not aware of any similar 
wide-field surveys of the southern sky which are producing results like yours 
[** correct me if I'm wrong, readers **]. MACHO and OGLE and their ilk have 
done or are doing regular surveys of specific patches of southern sky; and 
there are several people surveying the galactic plane and Magellanics for 
novae.

The closest equivalent I know about to your equipment & techniques seems to 
be the MISAO project. They recently announced their 1100th new variable. As a 
byproduct they have resolved a lot of misidentifications and positional 
errors in the GCVS. However their published list contains nothing south of 
Dec -33d so I presume all their observers are northern. Check out their 
website at:  http://vsnet.aerith.net/misao/index.html   MISAO also maintain a 
link list to many interesting and useful catalogues.

The Amateur Sky Survey (TASS) is currently testing their latest camera 
design, which will takes simultaneous 100-sec CCD exposures in B V R and I to 
discover and characterise all sorts of objects. So far TASS has concentrated 
on equatorial regions but there is at least one TASS camera already in the 
southern hemisphere. Check TASS out at:  http://vsnet.tass-survey.org

- - - -

I assume you want to maintain maximum CCD sensitivity for your comet hunting, 
therefore using a V filter or IR blocker is not desirable. This does make it 
a tad difficult to transform your lightcurves into standard magnitudes (I 
think Mike Bessel at Stromlo has a method?), but for some investigations this 
isn't a problem.

For example, the discovery process itself, determination of any period(s), 
and times of maxima/minima. Even the known variables can benefit from 
unfiltered CCD because their characteristics change. Many southern specimens 
have not been examined since Don Bradman humiliated the poms at Lords!

Generally, the red variables look much brighter than visual on unfiltered CCD 
- much to the embarrassment of new chum nova hunters - but their amplitudes 
are smaller. A lot of the dramatic visual variation is caused by a 
combination of the peak energy emission moving between Red and Very Red (or 
Near-Infrared), and temperature-triggered formation of opaque oxides in their 
atmospheres. Many specimens also have circumstellar material which is 
infrared-bright, or line emissions in the red & near infrared.

After looking at some of your 1000+ lightcurves I would agree a lot of them 
are miras or semiregulars. And those flatliners may turn out to be constant 
after all: suburban Canberra isn't the ideal place to do rigorous photometry! 
Nevertheless there are lots of interesting wiggly ones on your "unknown" list 
which demand follow-up; and undoubtedly some surprises await us in your known 
list.

Speaking personally I'm wondering if you have bagged any of the RV Tau 
variables I (occasionally) watch. Do you have a list of names of the stars 
you have imaged?

- - - -

Frank's apparent disinterest is not out of character for him (sadly), but I'm 
surprised that the AAVSO didn't bite. They have a CCD section. And Janet is 
usually eager to receive any kind of observations from down here.

Another alternative is to send your data to VSNET. A number of CCD and 
photographic observers already do this as a matter of routine; and some of 
them are only doing differential photometry like you. Of course identify the 
comparison stars etc. Some of these listings contain variables that are 
recorded nowhere else.

And finally, don't be at all surprised to discover new things in our half of 
the sky. You of all people should know that! ;-)


cheers,

Fraser Farrell
---------------------------------------------------
Buying Your First Telescope In Australia
www.trilobytes.com.au/astronomy/scope.htm

Binocular variables for Southern Observers
www.trilobytes.com.au/astronomy/bvstars.htm
---------------------------------------------------



>
> Rob visited me in Canberra a few months ago and saw my CCD based comet
> hunting setup. I've recently written some code to generate light curves
> for some southern varaibles that happen to grace my images on a regular
> basis. I explained to Rob that I've found quite a few stars that vary in
> brightness but are not catalogued in the GCVS, NSV nor HIPP catalogs and
> he suggested that you might be interested in them. A few years back I
> emailed Frank Bateson about it but didn't get very far. I guess he
> though I was a crackpot when I said I'd found 50 new variables!
>
> Partly to see what sort of data I had, and partly to establish some
> credibility for my findings, I created these light curves to demonstrate
> my work. Please have a look at the thumbnails linked from this
> explanatory page:
>         http://vsnet.tip.net.au/~vello/varstar/explain.htm
>
> What do you think? The "known variables" page shows some nice light
> curves. The "unidentifed varaibles" needs some follow-up work. A few are
> difficult to separate from the "noise" but most show a definite
> brightness variation. First up, are there any other catalogues that I
> should be checking to try to identify these stars?  I'd be amazed if
> they were all new, but hey, how many people have done a wide field CCD
> survey of the far southern sky? Its possible this area has been
> neglected.
>
> Secondly, my mag limit is around 12, so many of these are relatively
> bright stars and many show large variations. Perhaps they emit a lot of
> light in the IR and vary less at visual wavelengths. Are you interested
> in visually following up on some of these?
>
> Finally, who should I report these observations to?  I tried contacting
> the AAVSO but they never return my e-mails. Surely someone would be
> interested in 24,000 magnitude estimates (and growing!)
>
> Cheers,
>
> --
> Vello Tabur
> SearchSoftwareAmerica, R&D
> Comet Hunting Techniques: http://vsnet.tip.net.au/~vello

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