{
  "bibcode": "2015GCN.17543....1C",
  "body": "Z. Cano (Univ. Iceland), D. Malesani, J. P. U. Fynbo (DARK/NBI),\nA. de Ugarte Postigo (IAA/CSIC and DARK/NBI), N. R. Tanvir (Univ.\nLeicester),\nP. Jakobsson (Univ. Iceland), M. Saajasto, T. Pursimo (NOT), report on\nbehalf of a larger collaboration:\n\nWe observed the field of BAT trigger 633105 (Lien et al., GCN Circ. 17512)\nwith the\n2.5-m Nordic Optical Telescope (NOT) equipped with ALFOSC on 01-Mar-2015 and\n03-Mar-2015, obtaining 6x300 s of SDSS r-band exposures in each epoch.  The\nmid\nexposure times of our observations correspond to +0.60 and +2.59 days from\nthe\ninitial trigger, respectively.\n\nConsistent with the X-ray position of the known source [PFH2005] 622\n(thought to\nbe associated with the gamma-ray transient; Evans et al., GCN Circ. 17536),\nwe\ndetect one object at coordinates:\n\nRA = 00:45:14.80\nDec = +41:50:32.35\n\nIts magnitude is R =  22.7 +- 0.1 (using a USNO-A2.0 star in the field for\ncalibration). Two more objects are also detected in close proximity of the\nXMM\nposition (Pietsch et al. 2005, A&A, 434, 483), and potentially consistent\nwith\nit, including the source seen by UVOT by Hagen & Lien (GCN 17541), which\nappears\nto be quite blue (it has R = 22.3 +- 0.1 in our image).\n\nWe carried out digital image subtraction between our two images, where we\nsubtracted the first epoch from the second by using an adaptation of the\nISIS\nsoftware. In our difference image we do not detect any residual flux at the\ncombined XRT and XMM location, down to an upper limit of R > 23.2.\n\nAll objects seen in the NOT image are also apparent in the deep, archival\ndata\nfrom the PAndAS survey (McConnachie et al. 2009, Nature, 461, 66), which\nalso reveals\na few more, fainter objects in the close proximity of the XMM position. No\nobject seems\nto have varied significantly.\n\nA gif animation of the two epochs of NOT imaging, and the difference image,\ncan\nbe retrieved from:\nhttp://www.astro.ku.dk/~malesani/GRB/150301C/subtraction.gif\n\nA comparison image of the NOT image from 01-Mar-2015 and the PAndAS image\ncan be found at:\nhttp://www.astro.ku.dk/~malesani/GRB/150301C/comparison_NOT_PAndAS.png",
  "circularId": 17543,
  "createdOn": 1425506701000,
  "email": "zewcano@gmail.com",
  "subject": "BAT trigger 633105 (GRB 150301C): NOT r-band upper limit",
  "submitter": "Zach Cano at U of Iceland  <zewcano@gmail.com>",
  "eventId": "GRB 150301C"
}