{
  "bibcode": "2008GCN..7845....1K",
  "body": "D. A. Kann, U. Laux and S. Ertel (TLS Tautenburg) report:\n\nWe continue observations of the afterglow of GRB 080605 (independently \ndiscovered by Sbarufatti et al., GCN 7828, Kann et al., GCN 7829, and \nGomboc et al., GCN 7831). We acquired one 300 sec image each in V, R, and \nI around 0.95 days after the GRB, and further imaging 0.1 days later until \ndawn. Astonishingly, the afterglow is still clearly visible in R and I \nbands.\n\nAs mentioned in the above-cited GCNs, the afterglow is close to a star and \naffected by its PSF in images with low-quality seeing or large pixel \nscale, such as the TLS camera. To obtain a qualitative description of the \nafterglow evolution, we perform aperature photometry in a 3 pixel \naperature, and derive the aperature correction for each image by comparing \nthe counts for a reference star in the 3 pixel aperature with that in a 7 \npixel (which is typically seeing-matched) aperature. As a reference star, \nwe use the star to the south of the afterglow, USNOB1.0 ID 0940-0289655 at \n(catalog position): RA = 17:28:29.920, Dec. = +04:00:36.51, which has R2 = \n15.90 mag, I = 14.54 mag. We derive the following magnitudes for selected \nimages in the I band (the error is estimated to be 0.1 magnitudes in all \ncases):\n\ndt\t\tI\n\n0.00478791\t16.74\n0.00674681\t17.18\n0.00869923\t17.36\n0.01064872\t17.61\n0.01849396\t18.19\n0.02433042\t18.19\n0.05922051\t18.48\n0.96109933\t18.51\n1.05275325\t18.71\n\nThe early afterglow decay (0.00479 to 0.01849 days) is well-described by a \npower-law with decay slope alpha=0.97. After this, the afterglow decay \nseems to flatten. Between 0.06 days and 0.95 days, the afterglow magnitude \nremains unchanged, indicating a plateau phase. As the afterglow has \nresumed its decay 0.1 days later, this probably implies that the \nafterglow underwent a strong rebrightening which we caught after the \npeak. This is reminiscent of GRB 071003, which lies at a very similar \nredshift (Perley et al. 2008, ApJ, submitted, arXiv:0805.2394) of ~ 1.6 \n(Jakobsson et al., GCN 7832).\n\nFurthermore, we determined the R band magnitude at two epochs:\n\ndt\t\tR\n\n0.01655957\t19.87\n0.95457023\t20.75\n\nCorrected for the moderate Galactic foreground extinction of E(B-V) = \n0.136, we find R - I ~ 2 mag. This is a very red color for an afterglow, \nindicating strong internal reddening due to dust. We caution that the \nUSNOB1.0 comparison star may have incorrect photometry, on the other hand, \na simple image comparison shows that the R band magnitude is much fainter \nthan the I band magnitude.\n\nThe strong rebrightening combined with the large correction for dust \nextinction that is needed imply that this is an intrinsically extremely \nluminous afterglow. Further follow-up, especially in the NIR bands, is \nhighly encouraged.\n\nThis message may be cited.",
  "circularId": 7845,
  "createdOn": 1212805634000,
  "email": "kann@tls-tautenburg.de",
  "subject": "GRB 080605: TLS RRM Analysis, Plateau/Rebrightening, Red OT",
  "submitter": "Alexander Kann at TLS Tautenburg  <kann@tls-tautenburg.de>",
  "eventId": "GRB 080605"
}