[vsnet-chat 2225] Asteroids in our images

[Seiichi Yoshida <seiichi@muraoka.info.waseda.ac.jp>]

MISAO Project Announce Mail (August 15, 1999)

Hello. I am Seiichi Yoshida working on the MISAO project.

The number of CCD images taken by the Ageo Survey Team (KenIchi
Kadota, Seiichi Yoshida) is 4188 so far, from 1998 March 7 to 1999
July 30.

All the images are examined by the PIXY system, then checked for new
objects or new variable stars, and the magnitude data of known
variable stars are recorded. As the announce mail on Aug. 8 reported,
134 new variable stars have been discovered. However, no comets,
asteroids, novae nor supernovae have been discovered.

In fact, the situation on asteroids has been very strange. No new
asteroids were discovered from the 4188 CCD images. On the contrary,
known asteroids could not be detected at all, except for two cases.

The automatic new objects survey by the PIXY system must output
asteroids as candidates of new objects if they happened to be in the
images, and there are some past images of the same area.
However, only two asteroids have been detected hitherto, (4) Vesta as
reported in the announce mail on Feb. 26, and (349) Dembowska detected 
from CCD images of M66 taken in January. 

I investigated if it means asteroids so rarely happen to be in the
images by chance, or it means the PIXY system cannot detect new
objects completely because of some bug. Because the PIXY system cannot 
detect 16 mag at best from the Ageo Survey Team images, I investigated 
if asteroids until number 1000 have been in the field of the images in 
the past. As a result, I found that 42 asteroids were in the field of
Ageo Survey Team images and brighter than the limiting magnitude.

Here are the list of asteroids in the Ageo Survey Team images taken 
by 530-mm or more focal length telescope, the main instruments
recently. 

Asteroid            Date         Ma. f.length Lm. Result
(  6) Hebe          1999 Jul  7   8.9  530mm  14.0  O
( 75) Eurydike      1999 Feb  6  13.0  990mm  16.7  *
( 93) Minerva       1999 Jan 22  12.0  990mm  15.8  *
(148) Gallia        1999 Apr 29  12.1  530mm  14.3  *
(159) Aemilia       1999 Apr 14  13.2  530mm  15.3  O
(167) Urda          1999 Apr  8  13.9  530mm  15.4  *
(208) Lacrimosa     1999 May  1  13.5  530mm  15.3  O
(230) Athamantis    1999 Apr 14  10.5  530mm  15.3  ?
(243) Ida           1999 Jul 15  13.8  530mm  14.1  X
(349) Dembowska     1999 Jan  7  10.3  990mm  16.0  O
(354) Eleonora      1999 Jul  7  11.3  530mm  14.1  O
(454) Mathesis      1999 Apr 29  13.4  990mm  14.3  X
(483) Seppina       1999 May 20  13.1  530mm  15.2  O
(527) Euryanthe     1999 Apr  8  13.7  530mm  14.3  X
(538) Friederike    1999 May  8  13.9  530mm  14.6  -
(641) Agnes         1999 Apr 16  15.5  990mm  15.8  -
(644) Cosima        1999 Jul  7  14.3  530mm  14.7  X
(653) Berenike      1999 Apr 30  13.1  530mm  15.0  X
(656) Beagle        1999 Apr 14  14.0  530mm  15.3  X
(666) Desdemona     1999 Apr 14  15.2  530mm  15.5  X
(780) Armenia       1999 Jun  9  13.2  990mm  16.2  *
(803) Picka         1998 Nov 23  14.0  720mm  15.5  *
(825) Tanina        1999 Jan  7  14.3  990mm  16.2  O
(863) Benkoela      1999 Apr 14  13.7  530mm  14.4  -
                    1999 May  8  13.5  530mm  14.3  -

O: It was detected as a candidate of new object. But it was ignored
   because there were no past image for reference.
*: Because the image is only one, the existence could not be confirmed 
   automatically.
X: It was not detected.
-: No object could not be found at all.

Most of asteroids in the field of the images have been output as
candidates of new objects. However, because there were no past images
for reference, the system could not determine they are really new
objects or just normal stars not recorded in star catalog. So they
were ignored. Most of faint asteroids near the limiting magnitude were
not detected. 

There is one special case, that is (230) Athamantis. It must have been
output as a candidate of new object because there were past
images. But I guess the focal length of the past images were so
different (180mm against 530mm), I ignored the output. Because no
report is remained now, I cannot say any more.

After all, I can see the following conclusions.

* The possibility that an asteroid happens to be in the images is very 
  small.

    The Ageo Survey Team took over 4000 images, but only 42 asteroids
    were found. Much more new variable stars have been discovered.

* Enormous new objects may be remained in the Ageo Survey Team images.

    The 134 new variable stars of the MISAO Project were discovered by 
    comparing CCD images to past images and found as variable. But no
    asteroids could not be found in such a overlapping fields. The
    Ageo Survey Team is not concentrating on fields where few
    asteroids exist. Therefore, most of the Ageo Survey Team images
    have not been overlapping yet and the new variable stars were
    discovered from few overlapping images, in conclusion. In the
    images above, which asteroids happened to be in, many unknown
    variable stars must be remained. 

* The PIXY system can detect 13 mag or brighter new objects
  automatically.

    Most of 13 mag or brighter asteroids were output as candidates of
    new objects so far. After this, while the number of overlapping
    images increases, 13 mag or brighter new objects will be detected
    automatically. 

P.S.
The past MISAO project announce mails are available at:
  http://vsnet.info.waseda.ac.jp/muraoka/members/seiichi/misao/

--
Seiichi Yoshida
seiichi@muraoka.info.waseda.ac.jp
http://vsnet.info.waseda.ac.jp/muraoka/members/seiichi/index.html

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