[vsnet-grb-info 11948] GRB 120521C: Early Tautenburg limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  13337
SUBJECT: GRB 120521C: Early Tautenburg limits
DATE:    12/05/22 22:17:24 GMT
FROM:    Alexander Kann at TLS Tautenburg  <kann at tls-tautenburg.de>

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) 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), we do not detect any source, in agreement with earlier results
(Klotz et al., GCN 13319; Bersier et al., GCN 13320; De Cia et al., GCN
13321; Levan et al., GCN 13322; Jelinek et al., GCN 13323; Morgan et al.,
GCN 13325; Gorbovskoy et al., GCN 13329; Oates et al., GCN 13331). The
possible host galaxy (Perley et al., GCN 13332) 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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