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GCN Circular 9033

GRB 090323 TLS detection - still bright
2009-03-25T00:42:02Z (15 years ago)
Alexander Kann at TLS Tautenburg <>
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 

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 

- 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 

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