{
  "bibcode": "2009GCN..9648....1G",
  "body": "C. Guidorzi (U. Ferrara), A. Melandri, C.G. Mundell, D. Bersier,\nZ. Cano, S. Kobayashi, I.A. Steele, R.J. Smith (Liverpool JMU),\nand A. Gomboc (U. Ljubljana) report, on behalf of a large collaboration:\n\nWe re-analysed the data promptly acquired with the 2-m Faulkes\nTelescope North in the R and i' filters (Cano et al. GCN 9630)\nof the Swift GRB 090709A (Morris et al. GCN 9625).\n From the stacked images, we marginally detect a source in the\nr' frame at the position of the NIR afterglow found by PAIRITEL\n(Morgan et al. GCN 9635), identified as source 'B' by Subaru\n(Aoki et al. GCN 9634) and possibly detected in the r' and z' bands\n(Cenko et al. GCN 9646). The same object is not detected in the\ni' band frame (although with a shorter total exposure).\n\nStart time        End time        Exposure      Filter    mag\n(min)             (min)           (s)\n-------------------------------------------------------------------\n2.88             55.02           720            R        22.7 +/- 0.5\n7.55             47.05           520            i'       > 20.6\n-------------------------------------------------------------------\n\nCalibration was performed against the I and R2 values of the USNOB1\nnearby star at 19:19:44.575, +60:43:27.44 assuming I=14.68 and R2=15.70.\n\nWe built a tentative SED at the PAIRITEL observation mid time of 438 s\n(Morgan et al. GCN 9635), combining the P60 values in the z' filter\n(Cenko et al. GCN 9646) and the assuming for the r' filter an\nintermediate value comprising both the P60 and our own value.\nThis value as well as our i' band upper limits were backextrapolated\nto the chosen time assuming a range of power-law decay indices, from\n0.3 to 1. The SED was finally corrected for the Galactic reddening\nof E(B-V)=0.09. We found that the SED can be fitted with a simple\npower-law with spectral index beta=3.4 +/- 0.8 (90%cl) and no\nevidence for a Lyman drop.\nWe therefore support the nature of a very red afterglow at low z\n(Butler et al. GCN 9639) and possibly associated with a non-GRB\nprogenitor as suggested by the quasi-periodic oscillations found\nin the gamma-ray profile (Markwardt et al. GCN 9645; Golenetskii\net al. GCN 9647).\n\nOur stacked R band frame is available at the following link (red\nand green circles show the Swift-XRT and PAIRITEL circles, respectively):\n\nhttp://www.fe.infn.it/u/guidorzi/GRB090709A/090709A_R.jpg",
  "circularId": 9648,
  "createdOn": 1247227362000,
  "email": "guidorzi@fe.infn.it",
  "subject": "GRB 090709A: evidence for a very red afterglow at low z",
  "submitter": "Cristiano Guidorzi at Ferrara U,Italy  <guidorzi@fe.infn.it>",
  "eventId": "GRB 090709A"
}