TITLE: GCN CIRCULAR NUMBER: 7864 SUBJECT: GRB 080605: TLS 3rd Epoch - Source Confusion DATE: 08/06/09 01:24:01 GMT FROM: Alexander Kann at TLS Tautenburg D. A. Kann, U. Laux & S. Ertel (TLS Tautenburg) report: We obtained further images of the Swift GRB 080605 (Sbarufatti et al., GCN 7828). A 300 second Ic frame obtained under excellent observing conditions shows the field remains unchanged in comparison to the second epoch as well as the final images of the first epoch (Kann et al., GCN 7845). Recently, Yoshida et al. (GCN 7863) also claimed detection of a plateau phase. Clemens et al. (GCN 7851), on the other hand, report a clear fading of the afterglow, as well as only a moderately red color in comparison to Kann et al. (GCN 7845), which can possibly be explained by the moderate Galactic reddening alone. Comparison with a multicolor finding chart taken by GROND (C. Clemens, priv. comm.) reveals the culprit: source confusion. Near the position of the afterglow, there are in total three sources, all seemingly stellar in GROND images, along a line. The star to the southeast (Source #1) was immediately reported (Sbarufatti et al., GCN 7828, Kann et al., GCN 7829) and is clearly visible in the DSS. To the northwest, there is another source (Source #2), also clearly visible in the DSS. An inspection of the DSS IR frame reveals that #2 is hardly visible at all, but a new source (Source #3), inbetween #1 and #2, now becomes clearly visible. This source is extremely red, possibly a red dwarf, and it is THIS source which begins to dominate the photometry reported in Kann et al. (GCN 7845) (and presumably Yoshida et al., GCN 7863), which is mostly I band. The small offset from source #1 lead us to believe that this is the afterglow (and explained the puzzling observation that it seemed to slightly shift position). Therefore, we retract the identification of a plateau phase of the afterglow of GRB 080605, as well as the claim of extreme redness and the resulting high lumonisity around 1 day in the observer frame. On the other hand, the afterglow IS clearly detected on the early I band frames of the TLS RRM observation, as well as in the R band and a stacked V band frame. The early photometry, which leads to a decay slope of alpha ~ 1, is still valid. Image subtraction will have to be performed to see how many detections we have actually gotten. This message may be cited.