[vsnet-chat 4149] Large proper motion

[Seiichi Yoshida <comet@aerith.net>]

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
	http://stdatu.stsci.edu/dss/dss_form.html

	Astronomical Image On-line Access Interface
	http://dss.mtk.nao.ac.jp/

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.

	http://vsnet.aerith.net/misao/pixy/result/proper-j.html

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.

	No. 1087B
	Luyten Half-Second Catalogue, Second Edition (LHS; Luyten 1979)

	No. 1079
	Lowell Proper Motion Survey 8991 Northern Stars (Giclas 1971)

	No. 1112
	Lowell Proper Motion Survey - Southern Hemisphere  (Giclas+ 1978)

	No. 1098A
	NLTT Catalogue  (Luyten, 1979)

	No. 5070A
	Nearby Stars, Preliminary 3rd Version  (Gliese+ 1991)

These catalogs are available at the NASA Astronomical Data Center's
web site.

	http://adc.gsfc.nasa.gov/viewer/

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.

	http://vsnet.aerith.net/misao/pixy/result/proper.html

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.

P.S.
The past MISAO project announce mails are available at:
  http://vsnet.aerith.net/misao/

--
Seiichi Yoshida
comet@aerith.net
http://vsnet.aerith.net/

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