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GCN Circular 3499

Subject
GRB050504: Ashra-P2/3 monitor and Ashra-AFT response
Date
2005-05-28T14:38:57Z (20 years ago)
From
Koji Noda at ICRR,U of Tokyo <nodak@icrr.u-tokyo.ac.jp>
M.Sasaki, N.Manago, Y.Aita, T.Aoki, Y.Asaoka, M.Jobashi, K.Noda,
A.Okumura (ICRR, Univ.Tokyo), S.Ogawa (Toho Univ.), T.Chonan, Y.Watanabe
(Titech) report on behalf of the Ashra collaboration:

We have observed the field of GRB050504 (08:00:59 UT) covering the
Integral error circle (Mereghetti et al, GCN 3348Loading...
 
 ) by Ashra-P2/3
(Prototype of 2/3 scale) and Ashra-AFT at the Haleakala observatory in
Hawaii (latitude = 20d 42' 37" N, longitude = 156d 15' 31" W, altitude =
3020m) in conditions of variable clouds across the field. 

The Ashra-P2/3 continuously monitored the Integral field with 5sec-repeat
of unfiltered 4sec exposures from 1 second before the burst. The
Ashra-AFT automatically responded to the Integral trigger and took the
first image of 4sec-exposure at 08:01:57 UT (58 seconds after the burst
and 37 seconds after the alert socket). We also took following 10
unfiltered images of 4sec-exposure every 9 to 10 seconds (08:01:57 UT -
08:03:29 UT). 

No new source was found within the Integral position by the two telescopes.
We compared the co-added 10 images (10 x 4sec) from Ashra-P2/3 with BT
in the Tycho catalog and the earliest 3 images and the co-added images
(10 x 4sec) from Ashra-AFT with the USNO-B1.0 respectively. We preliminarily
obtained 4-sigma limiting magnitudes as follows:

Ashra-P2/3 limiting magnitude
 -----------------------------------------------------
   start    end      exposure     limit mag.
   after GRB (s)          (s)     BT
 -----------------------------------------------------
      -1      49    40.0           8.0
 -----------------------------------------------------

Ashra-AFT limiting magnitude
 -----------------------------------------------------
   start    end      exposure     limit mag.
   after GRB (s)          (s)     B1          R1
 -----------------------------------------------------
      58      62     4.0          16.7        15.0
      68      72     4.0          16.9        15.1
      77      81     4.0          16.8        15.1
 -----------------------------------------------------
      58     150    40.0          17.7        16.0
 ----------------------------------------------------- 

URL: http://www.icrr.u-tokyo.ac.jp/~ashra/

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