GCN Circular 13337

D. A. Kann, B. Stecklum and U. Laux (TLS Tautenburg) report:

We observed to position of Swift GRB 120521C (Trigger 522656, Baumgartner
et al., GCN 13318
Not found
 
 
) with the TLS 1.34m Schmidt telescope. Conditions were
mediocre, with good seeing but bad transparency. Observations were
triggered manually and began 28 minutes after the trigger (17 minutes
after the alert). We obtained 5 x 60 s images in Rc, 4 x 180 s images also
in Rc, and 1 x 600 s each in Z and Ic. The Ic image is affected in depth
by passing clouds.

At the position of the enhanced X-ray afterglow (Beardmore et al., GCN
13324
Not found
 
 
), we do not detect any source, in agreement with earlier results
(Klotz et al., GCN 13319
Not found
 
 
; Bersier et al., GCN 13320
Not found
 
 
; De Cia et al., GCN
13321
Not found
 
 
; Levan et al., GCN 13322
Not found
 
 
; Jelinek et al., GCN 13323
Not found
 
 
; Morgan et al.,
GCN 13325
Not found
 
 
; Gorbovskoy et al., GCN 13329
Not found
 
 
; Oates et al., GCN 13331
Not found
 
 
). The
possible host galaxy (Perley et al., GCN 13332
Not found
 
 
) is not detected.

We us the SDSS star at RA, Dec. (J2000) = 14:17:02.836, +42:6:07.62
(214.26181759, 42.10211787, catalog ID 1237661874023500000) as a
comparison star. Using the transformations of Lupton (2005), we find Rc =
18.33, Ic = 17.93 and Z = 17.78 for this star.

We find the following 2 sigma limiting magnitudes:

Time (days)	Exposure (s)	Filter	UL
0.019827	1 x 60		Rc	21.0
0.022275	5 x 60		Rc	21.8
0.027171	1 x 180		Rc	21.5
0.030760	4 x 180		Rc	22.5
0.040247	1 x 600		Z	20.2
0.048757	1 x 600		Ic	19.3

We note that while the non-detections we as well as other telescopes have
found point to this being a dark GRB, the X-ray absorption seen by Swift
is small. The Keck detection of a possible host galaxy in g' band likely
rules out a high-z interpretation, though.

No further observations are planned.

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