Japanese version Home Page Updated on June 17, 2001
March 26, 2001
Large proper motion
MISAO Project Announce Mail (March 26, 2001)
Hello. I am Seiichi Yoshida working on the MISAO project.
Images offered to the MISAO Project are examined comparing with the star catalog, the USNO-A2.0 or so, even if we have no past images of the same field. When bright stars not recorded in the star catalog, candidates of new objects, are found, we check them to judge they are really new objects like novae or not.
When candidates of new objects are found, we search the DSS (Digitized Sky Survey) past images and check whether the candidates exist or not. The DSS images are available at the following sites.
The STScI Digitized Sky Survey
Astronomical Image On-line Access Interface
Because the DSS images are based on the plates, you have to be careful to compare them with unfiltered CCD images. Especially, red variable stars can be often three mag or more fainter on the DSS images than on the unfiltered CCD images.
When a bright star on the CCD image is not found on the DSS images at all, it may be a real nova. However, you still have to keep being careful. Because some stars are moving fast, that is the proper motion.
Many stars with large proper motion have been found from the amateur images offered to the MISAO Project. The web page to introduce such stars with large proper motion, and the contrastive images of the recent CCD images and the old DSS images, are available at the following site.
There are two types of DSS, DSS 1 and 2. The DSS 1 covers the whole sky. However, you have to be careful to refer to the DSS 1 images because they are taken around 1950. Some stars move several arcsec in one year, so the position of them can be shifted several arcmin or more during 50 years.
In order to judge the bright star on the CCD image is a real new object or a star with large proper motion, you can look the DSS images around the star position carefully to search the counterpart, of course. But you also can check the catalogs of stars with large proper motion.
Brian Skiff, John Greaves, and Francisco Manuel Rica Romero introduce me the following five catalogs.
These catalogs are available at the NASA Astronomical Data Center's web site.
Brian Skiff told me that stars with large proper motion are nearly completely cataloged down to 16 or 17 mag in the northern sky, and down to about 13 mag in the southern sky.
All stars with large proper motion found in the MISAO Project are recorded in the catalog of the Lowell Observatory (No. 1079, 1112).
There are some variable stars with large proper motion. The following web page introduces an interesting examaple, double variable star, in the field of CCD images taken by Nobuo Ohkura, Okayama, Japan.
These stars are designated as GQ And and GX And in the General Catalogue of Variable Stars. They are also recorded in the Luyten's catalog of stars with large proper motion (No. 1087B) as LHS 3 and LHS 4. They are orbital double star, so they moves to the same direction in the same pace. Francisco Manuel Rica Romero told me that this pair is designated as GRB 34 AB, a orbital double star with a period of 2600 years.
Because the position of a star with large proper motion is different from the cataloged position in the USNO-A2.0, etc., it will be marked up as red after the examination using the PIXY System 2. You can see the proper motion easily comparing with the DSS images, even in case of the amateur images. So please be careful while searching new objects.
-- Seiichi Yoshida email@example.com http://www.aerith.net/