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 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 050509B (Gehrels et al. 2005). [GCN OPS NOTE(10may16): Per author's request, In the last paragraph, "050509A" was corrected to "050509B".]