{
  "circularId": 18078,
  "version": 2,
  "format": "text/plain",
  "createdOn": 1438030853000,
  "bibcode": "2015GCN.18078....1W",
  "submitter": "Alan M. Watson at Instituto de Astronomia UNAM  <alan@astro.unam.mx>",
  "editedOn": 1731009494249,
  "eventId": "GRB 150724B",
  "body": "Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC), William \nH. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori Fox (UCB), \nJ. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara \n(ORAU/GSFC), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico \nRamirez-Ruiz (UCSC), José A. de Diego (UNAM), Leonid Georgiev (UNAM), \nJesús González (UNAM), Carlos Román-Zúñiga (UNAM), Neil Gehrels (GSFC), \nand Harvey Moseley (GSFC) report:\n\nWe reobserved the field of the LAT GRB 150724B (Bissaldi et al., GCN \n18065) with the Reionization and Transients Infrared Camera (RATIR; \nwww.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio \nAstronómico Nacional on Sierra San Pedro Mártir from 2015/07 27.24 to \n2015/07 27.47 UTC (8819.11 to 8824.45 hours after the Fermi trigger), \nobtaining a total of 4.01 hours exposure in the r and i bands.\n\nWe detect the source we previously reported (Butler et al. GCN 18072) at \n23:27:33.82 +3:49:06.8 (J2000, �0.5\"). In comparison with the SDSS DR9, we \nobtain the following detections:\n\n   r 23.50 ± 0.19\n   i 23.99 ± 0.27\n\nThese magnitudes are in the AB system and are not corrected for Galactic \nextinction in the direction of the GRB.\n\nA naive comparison to our observations from the previous night would \nsuggest that the source has not faded in r but has faded in i. However, \nexamining the images in detail, we suspect that our photometry in i from \nthe first night might be influenced by a spuriously bright pixel. We \ntherefore discount the apparent fading in i.\n\nWe thank the staff of the Observatorio Astronómico Nacional in San Pedro \nMártir.\n\n[GCN OPS NOTE(27jul15): Per author's request, \"140724A\" was changed to \"150724B\" \nin the Subject-line.]",
  "subject": "GRB 150724B: Continued RATIR Optical Observations",
  "email": "alan@astro.unam.mx",
  "editedBy": "Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of Leo P. Singer at NASA/GSFC <leo.p.singer@nasa.gov>"
}