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GCN Circular 991

GRB010222: R-band data
2001-02-26T00:30:59Z (23 years ago)
Krzysztof Z. Stanek at CfA <>
K. Z. Stanek and E. Falco (Harvard-Smithsonian CfA) report:

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

  UT            R_c       exp
25.4385    21.48+-0.08  2x600 sec

Fitting a simple power-law decay to our data taken about one day after
the burst (GCN 983) and the current data yields a slope of about
1.3. This confirms the steepening decay of the optical afterglow, as
indicated by Masetti et al. (GCN 985).  Fitting broken power-law to
all the data produces a food fit, but the parameters of the fit are at
present underconstrained, except that the break seems to be gradual,
beta<<1. Continuing imaging is needed, also in the BVI-bands if

The R-band magnitude is relative to star "A" as marked in the finding
chart at, assuming
its magnitude R=17.0. Because of the discrepancy between the values
assigned to "A" by Valentini et al. (GCN 986: R=16.7) and Henden (GCN
987: R=17.175), we decided for now to continue using R=17.0 as our
fiducial point.

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