GCN Circular 9033
Subject
GRB 090323 TLS detection - still bright
Date
2009-03-25T00:42:02Z (15 years ago)
From
Alexander Kann at TLS Tautenburg <kann@tls-tautenburg.de>
D. A. Kann, U. Laux and B. Stecklum (TLS Tautenburg) report:
We observed the afterglow (Updike et al., GCN 9026, Cenko et al. GCN 9027)
of the intense Fermi GBM/LAT GRB 090323 (Ohno et al., GCN 9021) with the
1.34m Schmidt telescope of the TLS Tautenburg observatory under inclement
conditions (low transparency, passing clouds). We obtained 8 Rc frames of
600 seconds exposure time each before clouds shut us down. The afterglow
is faintly detected in each single image and clearly detected in the
complete stack.
Assuming the star at RA = 12 42 39.3, Dec. = +17 05 05.7 to have Rc =
17.15 (USNOR1=17.17, USNOR2=17.12), we measure the following afterglow
magnitude:
days after trigger Rc dRc (statistical)
1.87751 20.88 0.04
This value is only slightly fainter than those reported ~18 hours earlier
(Updike et al., GCN 9026, Cenko et al. GCN 9027), which may indicate the
following:
- The afterglow is undergoing a plateau phase or possibly even a
rebrightening (if it faded more inbetween).
- The magnitude of the comparison star is highly incorrect (e.g., variable
star). But we also used several other comparison stars and find agreement
within +/- 0.2 mags.
If the afterglow truly is this bright, this makes it one of the most
luminous afterglows every detected, comparable or even exceeding the
recent GRB 090313 (Perley et al., GCN 8985, de Ugarte Postigo et al.,
8992). The very low foreground extinction, excellent observability, low
influence of moonlight combined with the extreme high energy properties
(possible several ksec long tail emission in LAT, Ohno et al., GCN 9021,
extremely high isotropic energy release, Golenetskii et al., GCN 9030) and
the spectroscopic redshift (Chornock et al., GCN 9028) make this a GRB of
special interest, and more observations, especially with medium-size
telescopes, are encouraged. If weather permits, Tautenburg will continue
observations.
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