[vsnet-grb-info 17973] GRB 160509A: TLS Tautenburg Afterglow Detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19421
SUBJECT: GRB 160509A: TLS Tautenburg Afterglow Detection
DATE:    16/05/10 21:32:49 GMT
FROM:    Sebastian Schmidl at TLS Tautenburg  <schmidl at tls-tautenburg.de>

S. Schmidl, D. A. Kann, U. Laux (all TLS Tautenburg), S. Schulze (PUC), S.
Klose, and A. Nicuesa Guelbenzu (both TLS Tautenburg) report:

We observed the location of the afterglow of the bright Fermi LAT/GBM
(Longo et al., GCN 19403, Roberts et al., GCN 19411) GRB 160509A,
localized in the X-rays by Kennea (GCN 19407) and Kennea et al. (GCN
19408), in the optical/NIR by Levan et al. (GCN 19411) and Cenko et al.
(GCN 19416), as well as in the radio band by Alexander et al. (GCN 19414),
with the 1.34m Schmidt telescope of the Thueringer Landessternwarte
Tautenburg, in good conditions.

We obtained a total of 26 x 600 s images in the Rc band, starting at
20:46:04 UT, 11.78 hrs after the GRB. The total stack has an integration
time of 15600 s, centered 0.583 days after the GRB.

At the afterglow position, we detect an extended source. Comparing to the
higher resolution DCT image (Cenko & Tanvir, priv. comm.), there is a
nearby source which is somewhat blended with the afterglow in our image.
Therefore, we use a small aperature to measure the afterglow magnitude. 
Using four comparison stars in the surroundings, whose SDSS magnitudes
were transformed to the Rc band using the transformation equations of
Lupton (2005), we obtained a magnitude of:

Rc = 23.6 +/- 0.3 mag.

This is in good agreement with the detections derived by Levan et al. and
Cenko et al. after transforming their results from AB to Vega mags.

The magnitude is not corrected for the Galactic extinction along the line
of sight of E(B-V) = 0.25 mag (Schlafly & Finkbeiner 2011).

Using the prompt emission results of Konus-Wind (Frederiks et al., GCN
19417) and the redshift z = 1.17 (Tanvir et al., GCN 19419), we derive a
bolometric (1 keV - 10 MeV in the source frame) isotropic energy release
of (8.56 +/- 1.1)E53 erg, and a E_peak,rest = 625 keV. The isotropic
energy release is very similar to that of GRB 130427A, and we note the
light curve also shows similarities.

PS.: We also wish to point out that this GRB occurred on the 11th
anniversary of the first ever detected short-GRB X-ray afterglow, that of
GRB 050509A (Gehrels et al. 2005).