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GCN Circular 983

GRB010222: fading behavior
2001-02-24T03:39:15Z (23 years ago)
Krzysztof Z. Stanek at CfA <>
K. Z. Stanek, P. Challis, S. Jha, R. Kilgard, J. McDowell
(Harvard-Smithsonian CfA) and P. M. Garnavich (Notre Dame) report:

We have obtained additional R-band data for the optical afterglow of
the GRB010222 using the F. L. Whipple Observatory 1.2m telescope:

HJD-2450000         UT           R_c       exp
1963.9457     010223 10:48  20.16+-0.07  600 sec

Combined with our earlier R-band data (GCN 970), this indicates a
power-law decay with a slope of 0.89, consistent with previous
determinations (GCNs 973, 975).

In the B-band, between 4.3 hours and 24.2 hours after the burst the
afterglow dimmed by about 1.8 magnitudes:

HJD-2450000         UT           B         exp
1962.9855     010222 11:46  18.46+-0.02  600 sec
1963.8173     010223 07:43  20.25+-0.10  600 sec

This is consistent with no color evolution between B and R.

Errors in the magnitudes are statistical only.  The B-band magnitudes
are relative to star "A" as marked in the finding chart at, assuming its
magnitude B=17.6.

Reductions of additional data are under way.

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