TITLE: GCN CIRCULAR NUMBER: 7484 SUBJECT: GRB 080319B optical observations DATE: 08/03/20 13:57:38 GMT FROM: AAVSO GRB Network at AAVSO Veli-Pekka Hentunen (Varkaus, Finland), Arto Oksanen (Muurame, Finland), and Petri Kehusmaa (Hyvinkaa, Finland) report to the AAVSO High Energy Network the following optical detections and upper limits of GRB 080319B (Racusin et al., GCN Circular #7427): Veli-Pekka Hentunen and Markku Nissinen (Taurus Hill Obs., Varkaus, Finland) report the detection of the optical afterglow of GRB 080319B (Racusin et al., GCN Circular #7427). The afterglow was observed unfiltered for a total of 1500 seconds using an SBIG ST8-XME CCD mounted on a Meade LX200 0.3-m telescope. Observations commenced approximately 15.3 hours post-burst; the mid-point of the observations was 2008 March 19.8999 UT. The afterglow was clearly detected at an unfiltered magnitude of 19.08 +/- 0.02, calibrated relative to USNO-A2.0 1200-07324239. A detailed report of this observation is available at the following URL: ftp://ftp.aavso.org/grb/Veli-PekkaHentunen_080319B_2454545.53358_.txt A FITS image of this observation is available at the following URL: ftp://ftp.aavso.org/grb/Veli-PekkaHentunen_080319B_2454545.53358_.fits Petri Kehusmaa (Slope Rock Observatory, Hyvinkaa, Finland) reports a non-detection of the optical afterglow of GRB 080319B. The afterglow was observed through a V filter for a total of 1800 seconds using an SBIG ST-7XME CCD mounted on a 0.2-m telescope. Observations commenced approximately 17 hours post-burst; the mid-point of the observations was 2008 March 19.9675 UT. The afterglow was not detected in the V-band with an upper limit of R=17.6 (calibrated relative to USNO-A2.0). A detailed report of this observation is available at the following URL: ftp://ftp.aavso.org/grb/PetriKehusmaa_GRB080319B_2454545.93778_.txt A FITS image of this observation is available at the following URL: ftp://ftp.aavso.org/grb/PetriKehusmaa_GRB080319B_2454545.93778_.fits Arto Oksanen and Olli-Pekka Reimaala (Hankasalmi Obs., Hankasalmi, Finland) also report the detection of the optical afterglow of GRB 080319B. The afterglow was observed unfiltered for a total of 2040 seconds (17 x 120s) using an SBIG STL-1001E CCD mounted on an RC Optical Systems 0.4-m telescope. Observations commenced approximately 19.3 hours post-burst; the mid-point of the observations was 2008 March 20.0639 UT. The afterglow was clearly detected at an unfiltered (CR) magnitude 19.0 +/- 0.1, calibrated relative to USNO-A2.0. Note that this magnitude uses a different comparison star from that of Hentunen and Nissinen (see above), and may be offset by a few tenths of a magnitude. A detailed report of this observation is available at the following URL: ftp://ftp.aavso.org/grb/ArtoOksanen_GRB080319B_2454545.72325_.txt A FITS image of this observation is available at the following URL: ftp://ftp.aavso.org/grb/ArtoOksanen_GRB080319B_2454545.72325_.fits The AAVSO thanks the Curry Foundation for their continued support of the AAVSO International High Energy Network.