{
  "bibcode": "2011GCN.11844....1L",
  "body": "G. Leloudas, D. Malesani (DARK/NBI), D. Xu (WIS), P. Jakobsson (U.  \nIceland), J. Telting (NOT), report on behalf of a larger collaboration.\n\nWe observed again the field of the peculiar source GRB 110328A / Swift  \nJ164449.3+573451 (Cummings et al., GCN 11823; Kennea et al., ATel  \n3242) with the NOT equipped with ALFOSC, using the same instrument  \nsetup adopted in our first observation (Leloudas et al. GCN 11830).  \nObservations were carried in the R and z filters with exposures of  \n3x600 and 8x300 s, respectively. The observations were carried out  \nstarting on 04:10 UT, roughly 26 hr after our first observations and  \n39 hr after the first Swift trigger.\n\nThe reported galaxy at z=0.35 (Cenko et al., GCN 11827; Levan et al.,  \nGCN 11833; Thoene et al., GCN 11834), which is consistent with the  \nposition of the X-ray and radio emission (Osborne et al., GCN 11826;  \nZauderer et al., GCN 11836), does not show measurable variability over  \nthis time range.\n\nIts R-flux has remained constant to within 0.02 +- 0.07 mag, relative  \nto several stars in the field. Image subtraction using ISIS (Alard  \n2000, A&AS 144, 363) also does not reveal any variable source on the  \npotential host galaxy or nearby. Similarly, no variability is observed  \nin the z-band up to 0.02 +- 0.15 mag. Given the strong variability of  \nthe X-ray counterpart over the same time span, this suggests that the  \noptical emission is dominated by the host galaxy contribution.\n\nPreliminary photometric calibration using the Landolt standard field  \nSA 107 yields R = 19.35 for the USNO star 1475-0312998, close to its  \narchival value (R=19.4) that was used in GCN 11830.",
  "circularId": 11844,
  "createdOn": 1301518184000,
  "email": "giorgos@dark-cosmology.dk",
  "subject": "GRB 110328A / Swift J164449.3+573451: No optical variability of the optical counterpart",
  "submitter": "Giorgos Leloudas at Dark Cosmology Centre  <giorgos@dark-cosmology.dk>",
  "eventId": "GRB 110328A"
}