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August 15, 1999

    Asteroids in our images    

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.

( 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.

The past MISAO project announce mails are available at:


Seiichi Yoshida

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