If you think you've found an interesting object ...

Michael Richmond
July 17, 1999
Jan 16, 2001
June 18, 2002
Aug 26, 2003
Oct 18, 2003
June 12, 2004
Aug 3, 2004

"Wow, I think I've discovered a new variable star! But how can I be sure?"

You can find one good summary of steps to take in the MISAO Project's guide to investigating interesting objects. Read on for some other suggestions.

If you find an interesting object in some TASS catalog or in the database itself, you should first check to see if someone else has already noticed it. Arne Henden (in a message to vsnet-chat on 16 Jan 2001) suggested taking the following steps:

  1. determine its coordinates. You can often do this from the USNO-A finding chart program with a narrow field of view:
    http://www.nofs.navy.mil/data/FchPix/cfra2.html

  2. Check the SIMBAD archive

  3. check 2MASS or IRAS to see if it is a very red object (they are almost always variable).
    http://www.ipac.caltech.edu/2mass/

  4. check the asteroid location sites to see if it is just a known asteroid.

    John Greaves wrote a guide to searching for asteroids in TASS data included on Data Set 23; it gives very detailed instructions for using the "Guide" star charting program.

    read the guide to using "Guide" to search for asteroids

  5. look in all the available large-area surveys of the sky to see if they picked it up in the past. Arne Henden has written a nice paper listing (some of the) surveys as of April 2004, including URLs.
    Arne's paper on surveys (text, PDF)
    Arne's paper on surveys (slides, PDF)

  6. check the scanned photographic plate archives to see its history, or at least its relative color.
    http://www.nofs.navy.mil/data/FchPix/cfra2.html

  7. search for this object in list of stars which the TASS project has found to be (or suspects to be) variable

    If, at this point, your object still appears to be a new variable of some sort, then

  8. then contact organizations like VSNET or AAVSO , or send a message to the TASS mailing list


Check the SIMBAD archive

SIMBAD stands for Set of Identifications, Measurements, and Bibliography for Astronomical Data. It is a giant database which collects in one place millions of measurements from the astronomical literature, focusing mainly on stellar sources (for extragalatic data, see NED). SIMBAD contains several different services, but the one of interest is its ability to search for all known information about a star near some particular position.

There are two main WWW sites, one on each side of the Atlantic:

You will need to register to use SIMBAD, but there is no fee for most European or American users. Just read the registration information at http://cdsweb.u-strasbg.fr/simbad/userid.html and then fill out the appropriate form. You may need to wait a day or so for your registration information to be processed.

The examples below have links to the US mirror site; European users should follow the instructions and ignore the links.

Once you've registered, you can quickly look up information on any particular star of interest. The normal approach is to select the Query by identifier, coordinates or bibcode item on the main SIMBAD page. It presents a form which looks in part like this:

You must enter the coordinates of the object in question into the box at top left. Of the many possible formats, two make the most sense for TASS-related queries:

After you submit a query, SIMBAD should return a form with a list of the objects it has found in a small area centered on your coordinates. It always lists the positions of its objects in HHMMSS.ss DDMMSS format, which can be a pain if you only know the coordinates in decimal degrees. I believe that the object closest to the given position is always listed first in the output. You can learn more about any of the listed objects by clicking on its name in the list.

If no object appears close the position you specified, then SIMBAD's catalogs don't include it. Even if an object does appear at the position of your candidate, it may be listed as a humdrum, ordinary star.


Check the TASS page which lists some variables we've found

On the main TASS WWW site, there's an item labelled Sample data and variables:

There are two similar pages on the TASS Wiki which lists variables (new, old and suspected) in a format which is easier to search:

These pages have examples of stars which TASS members have noticed in their examination of our data. There are some examples of new variables, and some re-discoveries of known ones. Unfortunately, we haven't listed in any uniform manner the name or position of these variables, so it may be difficult to verify that your object is or isn't among the set listed here.

Martin Nicholson has gathered together candidates for variable stars in the TASS database, from several different sources. You can find his lists here: