{
  "bibcode": "2007GCN..6148....1C",
  "body": "H.-W. Chen (U Chicago), K. Glazebrook (Swinburne University), and J. S. \nBloom (UC Berkeley) report on behalf of a larger collaboration:\n\n\"We continued imaging observations of the field around GRB 070224\n(Racusin et al., GCN 6137), using MagIC on the Magellan Clay telescope.\nThe observations consisted of 5x300 sec dithered exposures in the i' band\nand 6x600 sec dithered exposures in the z' band, starting at Feb 25.180 UT,\n~ 8 hours after the initial Swift trigger.  The images were taken under\nphotometric conditions with a mean seeing of 0.5\" in i' and 0.6\" in z'.\nObject photometry was calibrated using a Sloan Digital Sky Survey\nphotometric standard observed after the GRB field.  Combining the images\nobtained using GMOS and MagIC, we measure photometry of the compact source\nat RA(J2000)=11:56:06.6 and Dec(J2000)=-13:19:48.9 (Chen, Glazebrook, &\nBloom, GCN 6145; see also Thoene et al. GCN 6142, Mirabal et al. GCN\n6146, Rol et al. GCN 6147) as the following:\n\n   Filter         AB      UT(mid)         Camera\n\n     i'    22.60 +/- 0.10  25.107          GMOS\n     z'    22.40 +/- 0.20  25.135          GMOS\n     i'    22.54 +/- 0.05  25.188         MagIC\n     z'    22.56 +/- 0.05  25.221         MagIC\n\nWe therefore conclude that this is not a variable source.\n\nThe source at RA(J2000)=11:56:06.5 and Dec(J2000)=-13:19:49.9 that\nappeared at low level in the first GMOS i'-band image (Chen,\nGlazebrook, & Bloom GCN 6145) remains absent in the MagIC images.\"",
  "circularId": 6148,
  "createdOn": 1172457821000,
  "email": "hchen@oddjob.uchicago.edu",
  "subject": "GRB070224: Magellan Imaging Observations",
  "submitter": "Hsiao-Wen Chen at U Chicago  <hchen@oddjob.uchicago.edu>",
  "eventId": "GRB 070224"
}