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GCN Circular 11853

GRB 110328A / Swift J164449.3+573451: Infrared transient
2011-03-31T18:19:39Z (13 years ago)
Andrew Levan at U.of Leicester <>
A.J. Levan (U. Warwick), D. Perley (U.C. Berkeley), N.R. Tanvir (U.
Leicester), J. Bloom, S.B. Cenko (U.C. Berkeley) report for a larger

"We re-observed the localization of GRB 110328A with Gemini-N/NIRI
on 31 March 2011. Observations were taken in the K-band, and began
at 13:15UT, roughly 24 hours after our previous observation (Levan
et al. GCN 11846). We find that the IR source, coincident
with the X-ray (Osborne et al. GCN 11826) and radio (Zauderer et
al. GCN 11848) localisations has faded by 0.25 +/- 0.03 magnitudes
over this time frame. Hence we conclude that the IR light does
contain a substantial contribution from transient emission. We note
that the apparent brightening of the source in a few hours between the
observations of Morgan et al. (GCN 11845) and Gemini (GCN 11846),
coupled with the fading over the subsequent 24 hours, suggests that
the behaviour of the system is complex, and as in the X-ray, is not
simply modelled by either a rising, or decaying lightcurve.

The location of the source is consistent with the galaxy
observed in the optical with a measured redshift z=0.351,
(Levan et al. GCN 11833, Thoene et al. GCN 11834) hence
increasing the confidence in a true association.

Further observations are planned."
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