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[vsnet-survey 66] (fwd) variable star survey by Vello Tabur
(fwd) variable star survey by Vello Tabur
The following messages have been posted to vsnet-chat:
From: Fraser Farrell <fraser@trilobytes.com.au>
Date: Wed, 28 Nov 2001 01:22:54 +1030
Subject: [vsnet-chat 4929] Re: new southern variables
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://www.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://www.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://www.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://www.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://www.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://www.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://www.tip.net.au/~vello
Date: Tue, 27 Nov 2001 11:53:06 -0700 (MST)
From: Brian Skiff <bas@lowell.edu>
Subject: [vsnet-chat 4930] Re: new southern variables
This looks like very useful stuff, and I encourage Vello to proceed
with the work. For inclusion in databases it will be necessary to have
at least an approximate zero-point for the magnitudes. Given the
magnitude limit, I would use "good" Tycho-2 stars (errors < 0.03 in both
VT and BT), and given the instrumentation, I would transform to Cousins R
using equations Arne Henden has provided. It would be better to have a
separate transformation for the obvious Miras and LPVs (i.e. the red stars
with a lot of far-red/near-IR output), perhaps simply a zero-point fudge-
factor.
Convert everything using at least two (preferably more, up to 5 or 7)
comparison stars to standard R. Make a list of coordinates to identify
the stars. These should be found from a current "catalogue of precision",
in the south meaning specifically UCAC1. It may be helpful to examine each
star on digitized sky survey images to check for crowding etc and verify
the identification.
For the cyclic variables: once you have about three cycles in hand,
and the period is reasonably determinate, I would bundle up the stars in
batches of 50 or 100 and publish them with finder charts and lightcurves
in the IBVS. The data going into the lightcurves can be included as links
to the on-line version of the paper(s). An example of the final product
(sans lightcurves) can be seen in Lennart Dahlmark's recent list:
http://www.konkoly.hu/cgi-bin/IBVS?5181
Dahlmark has his data logged by hand, so there are no lightcurves, although
I am hoping to get his data keyed-in eventually. With your automated
set-up, you can generate the lightcurves readily, so this is not a problem.
I'll be pleased to help with the catalogue identification part if
desired, mainly because I don't want to see additional clutter in the
stellar databases. Bulk search in VizieR, as Fraser suggests, do work most
of the time, but there are some subtleties that can trip you up here and
there.
\Brian
Date: Thu, 29 Nov 2001 18:13:51 +0000 (GMT)
From: Roger Pickard <rdp@star.ukc.ac.uk>
Subject: [vsnet-chat 4931] Re: new southern variables
Dear Vello (and Fraser),
I was amazed to read Fraser's message on VSNET recently together with a
copy of your original e-mail.
Frazer has already answered a number of points about catalogues etc., your
survey and others similar and even covers the usefulness (although I
didn't like being reminded of what Don Bradman did!) of what you're doing,
so I wont dwell on those points.
It's certainly sad that Frank Bateson didn't show any interest, but I know
he is looking forward to retirement, and at age 90, I guess he's entitled
to do so!
As for the AAVSO, they can be great at times but at others you wouldn't
think they existed but it's still surprising they didn't bite!
I'd like to be able to say that the British Astronomical Association could
help, but we only have limited resources and would do no more than store
images for the time being. However, if you could extract date, time and
mag etc. for each one then we could certainly incorporate them into our
database more readily. That said, our database is predominantly of
northern hemisphere stars (although we do have a few variables south of
the equator on our programme and tend to exchange information with the
RASNZ).
The work you're doing is very worthwhile and must be preserved.
Best wishes,
Roger
-----
Roger Pickard,
Director, BAA Variable Star Section,
28 Appletons,
Hadlow,
Kent TN11 0DT.
England.
Tel: 01732 850663 (Int: +441732850663)
E-mail: rdp@star.ukc.ac.uk
BAA VSS Web Page: www.britastro.org/vss
From: "Stan Walker" <astroman@voyager.co.nz>
Date: Sat, 1 Dec 2001 09:16:15 +1300
Subject: [vsnet-chat 4932] Re: new southern variables
Hi All,
I was intrigued by the work of Vello Tabur which Fraser mentioned and took
the opportunity to look at the noted web site. It's a refreshing change to
see someone who actually follows up on new variables and gets enough
measures to enable some sort of a classification.
It's disappointing that there has been a lack of interest but not all that
surprising. Firstly, the length of time the operation has been going is
short - only a few hundred days - and Vello may tire of the game so that
after the time and trouble of setting up a database to handle all these
measures they suddenly cease! I certainly hope Vello doesn't - maybe he'll
give up comets and concentrate on variables?
I notice a comment in the database to the effect that CCD measures are much
better than visual measures. This would not go down well in certain
quarters - and is not necessarily true given the unfiltered nature of the
measures. Some observers are very good and with good sequences the results
are very impressive.
Some years ago I mentioned to Frank Bateson the probability that someone
would produce a set-up like Vello's and produce as many measures as the rest
of the section put together. The idea was derided but it seems to be
happening! Fraser mentions the NACAA meeting but a more useful spot might be
the planned AAVSO meeting in Hawaii next year? The VSS is fairly moribund at
the moment - it needed a new director years ago - and, in spite of my
aversion to American dominance of too many things, I feel that a centralised
repository for all VS measures is the best way to go.
Finally, I've been setting up a stopped down Meade 8 with BVRI filters to
measure Cepheids and Miras. But maybe the telephoto lens is the way to go.
Seems so from Vello's results.
Regards,
Stan
----- Original Message -----
From: Fraser Farrell <fraser@trilobytes.com.au>
To: Vello Tabur <vello@pcug.org.au>
Cc: <vsnet-chat@kusastro.kyoto-u.ac.jp>
From: aah@nofs.navy.mil
Date: Sat, 1 Dec 2001 09:55:09 -0700
Subject: [vsnet-chat 4933] Re: new southern variables
Stan wrote:
>Finally, I've been setting up a stopped down Meade 8 with BVRI filters to
>measure Cepheids and Miras. But maybe the telephoto lens is the way to go.
>Seems so from Vello's results.
Those are two different approaches. For followup observations, I would
prefer the better pixelization you will get from the Meade 8; the photometry
should be superior. In addition, the BVRI filters are much better
than no filters, or just one filter, when using a telephoto. I'm surprised
you are stopping the system down, as there should be very few bright variables
you cannot observe full aperture.
For discovery, wide field is essential and a telephoto fits the bill.
Note that ROTSE-I uses Canon telephoto lenses and has discovered
thousands of variables in the north; a similar system in the south would
be great fun. ASAS is close, but at last glance was not doing an all-sky
survey. Once the sky has been covered to ~14th mag, then you have to start
using larger apertures; a fun exercise in itself.
I'd recommend the AAVSO Hawaii meeting for discussions relating to
observation depositories. It is being touted as a Pan-Pacific meeting
and will be combined with a high-energy workshop as well. I hope to
make it there if I can find funding.
Arne
Date: Mon, 3 Dec 2001 23:57:28 -0600
From: Seiichi Yoshida <comet@aerith.net>
Subject: [vsnet-chat 4935] Re: new southern variables
Dear Vello Tabur and VSNET colleagues,
I am Seiichi Yoshida working on the MISAO Project.
> 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://www.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.
Vello, congratulations on your discovery of new variable stars! I
visited your web page. I believe some of them must be real new
variable stars.
Yes, there are dozens of thousands of new variable stars discovered
recently in addition to the catalogs you have checked. As Fraser
kindly introduced, I have a database of many variable stars including
undesignated recent ones. The catalogs registered in the database are:
http://www.aerith.net/misao/pixy/catalog.html
I could not find the list of R.A. and Decl. of your new variable stars
on your web page. If it is available, I can check them with 1300
thousand objects in my database and the GSC, USNO-A2.0, Tycho data.
In general, including the MISAO Project, the special (not authorized
by GCVS, IAU, etc.) names are assigned to the new variable stars by
the discoverers. Vello, would you please assign the names for your
stars and issue a list of names, R.A. and Decl., magnitude range, and
so on? If the list is released, we can register it to the database and
make follow-up observations.
As Fraser pointed out, most of the MISAO images are of the Northern
Hemisphere right now. But southern images are also welcome!
Please assign the special name even if your star is identified with
GSC, USNO-A2.0, Tycho, IRAS, MSX5C, etc. because those names do not
express that the star is variable. In general, we do not assign a
special name when another special name has been already assigned as a
variable star. But it depends on the policy of discoverers or
projects.
Best regards,
--
Seiichi Yoshida
comet@aerith.net
http://www.aerith.net/
vsnet-adm@kusastro.kyoto-u.ac.jp
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