GRB 000131

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  537
SUBJECT: Optical observations of GRB000131
DATE:    00/02/09 11:37:45 GMT
FROM:    SG Bhargavi at Indian Inst of Astrophysics  <bhargavi@iiap.ernet.in>  S.G.Bhargavi, A.K. Pati, G. SelvaKumar and R.Cowsik (Indian Institute of Astrophysics,Bangalore, India 560034)
 
 We observed the error box of GRB000131 (GCN #529, #530) on Feb 4th and  5th between 15-18UT using the 2.34m as well as 1.02m telescopes of  Vainu Bappu Observatory, Kavalur, India. The sky conditions were  non-photometric with poor transparency and seeing (fwhm >2".5).
 
 The fading optical counterpart reported by Peredson et al ( GCN #534) is  not detected in a single 30min V image (limiting magnitude = 21.0) taken  on Feb 4.68 UT with 2.34m telescape.

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TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  534
SUBJECT: GRB 000131 Optical Observations
DATE:    00/02/06 22:46:47 GMT
FROM:    Holger Pedersen at Copenhagen U Obs  <holger@astro.ku.dk>

VLT Detection of Fading Optical Source in the GRB 000131 Error Box

H. Pedersen, B. L. Jensen, J. Hjorth, L. Fogh Olsen (U. of Copenhagen), M. I. Andersen (U. of Oulo), J. Gorosabel (DSRI, Copenhagen), M. Vestergaard (Ohio State U.), L. Kaper (U. of Amsterdam), and A. O. Jaunsen (U. of Oslo), on behalf of a European GRB consortium, report:

"Using the 8.2-m Antu telescope, Paranal, and the 1.54-m Danish telescope, La Silla, we have performed optical observations, covering the entire error box of GRB 000131 (GCN #529, #530), as follows:

Antu:

2000 February 4.04 UT; B, V, R ; 240 s each filter ; FWHM = 0.9"
2000 February 4.22 UT; B, V, R ; 240 s each filter ; FWHM = 0.9"
2000 February 6.10 UT; B, V, R ; 240 s each filter ; FWHM = 1.2"
2000 February 6.22 UT; B, V, R ; 240 s each filter ; FWHM = 1.2"

1.54-m Danish:

2000 February 4.19 UT; I ; 3600 s ; FWHM = 1.3"

For Antu, two separate pointings were obtained using FORS1; the exposure times apply to each of these. For the 1.54-m, the error box was covered by a single pointing with DFOSC.

Intercomparison of the Antu images reveals a single, unresolved object, which has faded significantly between the two observing nights. The variation is noticed on the V and R exposures, while the B exposures do not show the object at any epoch. The object is detected in the combined 1.54-m Danish I-band image.

Its position is RA(J2000) = 6:13:31.0, Dec(J2000) = -51:56:40, with an uncertainty of about 2".

The object has R ~ 24 in the Feb 4 images and has faded 0.6+-0.1 mag on Feb 6, corresponding to a power law decay index of -1.2+-0.2.

Sections of the images can be seen at http://www.astro.ku.dk/~brian_j/grb/grb000131/

jointly with a DSS finding chart.

We appreciate the kind assistance given by the VLT Service Mode team."

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FORS1: 480 s in R, taken 2000 Feb 4.04-4.22.
The spike to the left of the OT is due to a bright (V~9) star to the south.
(North - up, East - left)
FORS1: 480 s in R, taken 2000 Feb 6.10-6.22.
The spike to the left of the OT is due to a bright (V~9) star to the south.
(North - up, East - left)
FORS1: 480 s in V, taken 2000 Feb 4.04-4.22.
The brightening of the field is due to a bright (V~9) star to the south.
(North - up, East - left)
 FORS1: 480 s in V, taken 2000 Feb 6.10-6.22.
The brightening of the field is due to a bright (V~9) star to the south.
(North - up, East - left)
       
 
       
DFOSC: 3600 s in gunn-i, taken 2000 Feb 4.19.
The spikes are due to a bright (V~9) star to the south.
 DSS-2, quoted limit: R~22.0
The circle indicates the approximate position of the OT, with the surrounding box covering the sections shown above.
DSS-2, quoted limit: R~22.0
The diamond represents the IPN+BATSE error-box, with the two squares being the 6.8x6.8' pointings of FORS1. The DFOSC-pointing covers the whole image.
The OT is situated just to the North (up) and West (right) of the bright star at the Position 2-pointing.
  

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TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  530
SUBJECT: BATSE+IPN location of GRB000131
DATE:    00/02/03 00:02:02 GMT
FROM:    R. Marc Kippen at BATSE/UAH/MSFC  <marc.kippen@msfc.nasa.gov> R. M. Kippen (UAH/MSFC) reports on behalf of the BATSE GRB Team:

GRB000131 was detected by BATSE as trigger #7975 at 53877.497 s UT on 2000 January 31.  BACODINE/GCN locations were not issued because the trigger began in a real-time telemetry gap.  The burst lasts more than 100 s and is therefore undoubtedly the same event detected by KONUS, Ulysses and NEAR (GCN 529) some 76 s after the BATSE trigger time (corresponding to the brightest pulse of the burst).  The final BATSE location is (R.A., Dec. J2000) = (94.0, -52.0 deg), with a total (statistical + systematic) error radius of 2.3 deg (68% Conf.).  This location rules out one of the two possible IPN error boxes (GCN 529), which means that the most probable combined BATSE+IPN error-box is:

                          RA(2000)            DEC(2000)
 ERROR BOX CENTER:    6 h 13 m 32.72 s    -51 o 55 '  36.77 "
 ERROR BOX CORNER 1:  6 h 13 m  8.83 s    -52 o  2 '  20.83 "
 ERROR BOX CORNER 2:  6 h 13 m 25.43 s    -51 o 50 '  11.43 "
 ERROR BOX CORNER 3:  6 h 13 m 40.09 s    -52 o  1 '   1.94 "
 ERROR BOX CORNER 4:  6 h 13 m 56.59 s    -51 o 48 '  52.07 "

The center of this box is within about 0.4 deg of the independent BATSE location centroid.

-eof-

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TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  529
SUBJECT: IPN localization of GRB000131
DATE:    00/02/02 23:36:17 GMT
FROM:    Kevin Hurley at UCBerkeley/SSL  <khurley@sunspot.ssl.berkeley.edu> K. Hurley, on behalf of the Ulysses GRB team, and T. Cline and E. Mazets, on behalf of the KONUS-WIND and NEAR GRB teams, report:

Ulysses, Konus, and NEAR observed a gamma-ray burst on January 31, 2000 at 14:59:13 UT.  Its T90 duration was ~50 s and its 25-100 keV fluence was ~10^-5 erg/cm^2.  At present, it can only be localized to two alternate ~55 sq. arcmin. error boxes given by the following preliminary centers and corners (~3 sigma confidence):

 ERROR BOX CENTER:   6 h 13 m 32.72 s    -51 o 55 '  36.77 "
 ERROR BOX CORNER 1:  6 h 13 m  8.83 s    -52 o  2 '  20.83 "
 ERROR BOX CORNER 2:  6 h 13 m 25.43 s    -51 o 50 '  11.43 "
 ERROR BOX CORNER 3:  6 h 13 m 40.09 s    -52 o  1 '   1.94 "
 ERROR BOX CORNER 4:  6 h 13 m 56.59 s    -51 o 48 '  52.07 "
 
     OR

 ERROR BOX CENTER:  10 h 48 m 50.99 s      4 o 34 '   1.70 "
 ERROR BOX CORNER 1: 10 h 49 m 21.03 s      4 o 35 '  42.55 "
 ERROR BOX CORNER 2: 10 h 48 m 31.31 s      4 o 36 '  35.98 "
 ERROR BOX CORNER 3: 10 h 49 m 10.65 s      4 o 31 '  26.95 "
 ERROR BOX CORNER 4: 10 h 48 m 20.91 s      4 o 32 '  19.87 "

There is a fair chance that further processing will allow one of these positions to be ruled out.

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