Japanese version Home Page Updated on August 29, 2000
August 29, 2000
Magnitude data collaboration between projects
MISAO Project Announce Mail (August 29, 2000)
Hello. I am Seiichi Yoshida working on the MISAO project.
It has passed about one and a half of year since the discovery of the first variable star on the MISAO Project. Now the number of MISAO variable (MisV) stars is about to reach to 1000.
Unfortunately, most of the MisV stars have a few observations and the profiles such as variable type, period, etc., are uncertain, because it has not passed long time since the MISAO Project started.
However, some of the MisV stars were observed not only in the MISAO Project but also by outside people or projects. As a result, there are some stars whose period was determined, which was uncertain only based on the MISAO's data, or whose interesting behavior was revealed.
The light curves of all MisV stars also observed by outside people or projects are available at the following web page.
MisV Stars Light Curve
We received the MisV observations from the following outside people.
The details on MisV0001 was reported in the announce mail issued on Apr. 19, 1999. The 390 day period was obtained based on the Kiyota's observations.
Mike Collins and Guy M Hurst reported me the interesting observations. They said that MisV0884 was too faint, fainter than 11 mag, when it was bright as 9.3 mag in the MISAO Project observations. Especially, Hurst's observations was with unfiltered CCD, as same as the MISAO observations, so it cannot be explained by the color of the star. Maybe it is a strange variable star.
Some MisV stars are in the well-observed fields, near by M27, near by recent novae, etc. If you find MisV stars on your images, and measure the magnitude, please report it to the public.
There are some working projects which are taking CCD images of all sky, accumulate magnitude data of stars, and search variable stars, besides the MISAO Project. The two projects, TASS (The Amateur Sky Survey) and ASAS (The All Sky Automated Survey), publish the observation data to the web.
Some MisV stars were observed in their patrol images. In the "MisV Stars Light Curve" web page, the light curve including the TASS and ASAS data are available. Most of the TASS data were researched by Michael Richmond. The identifications with ASAS stars were researched by John Greaves.
One of them, MisV0009 shows an interesting light curve. The TASS I-band observations show both the slow fading and short-time eclipse-like fading. The eclicpse-like event occurred between 2450995 and 2451022 (JD), with a large amplitude as maximum 10.2 mag and minimum 12.4 mag. But while TASS I-band observations were detecting the slow fading, TASS V-band observations show it was constant, or maybe slightly brightening. Including the MISAO observations and excluding the eclipse-like event, it looks like a slow variability with a rough period of 500 days.
Richmond also pointed out that the four stars, MisV0429, MisV0697, MisV0698 and MisV0699, was not recorded in the TASS project, although they are in the TASS patrol fields observed many times. It may be because the maximum brightness observed in the MISAO Project are faint as 12.8 mag, 13.3 mag, 13.7 mag, 13.8 mag respectively. But it maybe imply the rapid brightening and fading.
There are many ASAS data of MisV stars also observed in the ASAS project. The periodic variability evidently appears in the light curve. Most of them were revealed as Mira type or SR type variable stars with a long period. But the period of MisV0911 is uncertain, although the light curve looks quasi-periodic.
As mentioned above, data collaboration between projects can yield valuable information. In the MISAO Project, the magnitude of new variable stars discovered by outside searchers or projects are also measured and reported to the VSNET, not only searching MisV stars.
There are some MisV stars whose strange behavior were detected only based on the MISAO Project. In case of MisV0073, the unfiltered CCD observations suggest that short-period variability with about 20 day period. But the difference between unfiltered CCD magnitude and CCD magnitude with IR-blocking filter suggests that MisV0073 is a red variable star.
However, there are not data enough to determine the type or features of those stars with strange behaviors still now. It is also an important work of the MISAO Project to accumulate magnitude data continuously after this, not only to discover new variable stars.
By the way, the catalog of 2MASS (The Two Micron All Sky Survey) was published recently. Taichi Kato researched the identifications between the 2MASS data and MisV stars and revealed many MisV stars are recorded in the 2MASS catalog as bright objects. It means most of the MisV stars are red variables. Taichi Kato also found that the position of MisV0041 was inaccurate, based on the identification with 2MASS data.
As mentioned above, investigation of catalogs can reveal the type of variable stars or help to find mistakes. The number of all sky surveys increases after this and many catalogs will be published in the future. The catalogs based on the amateur activities like the MISAO Project can be also published. Therefore, researches on catalogs will be one of the important works in astronomy. In the MISAO Project, Taichi Kato and John Greaves research various catalogs for identifications with the MisV stars.
-- Seiichi Yoshida email@example.com http://www.aerith.net/