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GCN Circular 9041

Subject
GRB 090323: TLS detection at 5 days, no break
Date
2009-03-28T04:23:25Z (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 decent 
conditions (low transparency). We obtained 11 Rc frames of 600 seconds 
exposure time each before dawn shut us down. The afterglow is faintly 
detected in some single images and well-detected in the 
complete stack.

Using the same comparison star as Kann et al. (GCN 9033), we measure the 
following afterglow magnitude:

days after trigger	Rc	dRc (statistical)

5.10418			22.67	0.20

Using other published data (Updike et al., GCN 9026, Wang et al., GCN 
9034, Perley et al. GCN 9036, Guidorzi et al., GCN 9039) as well as 
additional TLS data from the first observation run, we find that all data 
agree decently well with a single power law decay with a slope alpha ~ 
1.8. Therefore, there does not seem to be a plateau phase, but there is 
also no sign of a break yet. The relatively steep decay makes it unclear 
if this is a steep pre-break decay slope or a shallow post-break decay 
slope. In the latter case, it will be possible to track the afterglow for 
a very long time. Further deep, high S/N observations with larger 
telescopes are advised.

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