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GCN Circular 185

Subject
GRB981226 Optical Observations
Date
1998-12-31T11:37:38Z (25 years ago)
From
Brad Schaefer at Yale <brad@grb2.physics.yale.edu>
Bradley E. Schaefer (Yale U.), Jonathan Kemp, Irina Feygina, Jules Halpern
(Columbia U.) report:

"We have obtained B, V, and R images with the 0.9-m and 1.0-m telescopes
on Cerro Tololo of the GRB981226 position on the nights of 26/27, 27/28,
and 30/31 December 1998.  We find no variable sources, and no significant
changes from the Digitized Sky Survey.  This includes the entire BeppoSAX
WFC error circle (Di Ciolo et al. IAUCirc. 7074) as well as the BeppoSAX
NFI error circle (Frontera et al. IAUCirc. 7078).  

A journal of our observations, the corresponding magnitudes, and limits
are presented in the table below.  Our limiting magnitudes are quoted for
a signal-to-noise ratio of 4.  For the three variables that have been
proposed previously, we find as follows: 

(1) No source is visible at the position of the proposed infrared variable 
    (Castro-Tirado et al. GCN 173) to the limits stated below.  This
    implies R-J > 1.7 for this source if it is the afterglow.

(2) There is no significant evidence for variability of the proposed
    candidate of Galama et al. (GCN 172).

(3) The source identified by Wozniak et al. (GCN 177) is clearly visible,
    but we have no significant evidence of its variability."

    -------------------------------------------------------------------
    Telescope    UT start    Band   Limit    Mag(Galama)   Mag(Wozniak)
    -------------------------------------------------------------------
    CTIO 1.0m   Dec 27.044    R     21.6     20.74+-0.13   21.20+-0.20
    CTIO 0.9m   Dec 27.064    V     21.8    >21.8         >21.8
    CTIO 0.9m   Dec 27.071    B     21.5    >21.5         >21.5
    CTIO 1.0m   Dec 28.034    R     21.7     21.06+-0.15   21.15+-0.24
    CTIO 0.9m   Dec 28.065    V     21.7    >21.7         >21.7
    CTIO 0.9m   Dec 28.072    R     21.0     20.8 +-0.3    21.03+-0.24
    CTIO 0.9m   Dec 31.052    R     22.1     21.10+-0.10   21.61+-0.20
    ------------------------------------------------------------------
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