{
  "bibcode": "1999GCN...221....1T",
  "body": "GRB 990123 : Multiple and Distorted Images of the Host Galaxy?\n\nE. L. Turner (Princeton Univ. Obsv.):\n\nDjorgovski et al. (GCN Circ. 216) suggested that GRB 990123 might be\nstrongly lensed by an intervening galaxy based on the extreme energetics\nimplied by its high gamma-ray fluence (Feroci et al., IAUC 7095) and\nthe redshift lower bound of 1.61 (Kelson et al., IAUC 7096) and on the\nrelatively bright coincident galaxy found on the digital POSS-II images\nby Odewahn et al. (GCN Circ. 201 and IAUC 7094).  Their prediction that\nthis galaxy's redshift would be much smaller than 1.6 and probably in\nthe range 0.2 to 0.3 was quickly confirmed by Hjorth et al. (GCN Circ. \n219) who in fact found one definite galaxian redshift system at z = 0.286\nand a second possible one at z = 0.210, thus providing strong apparent\nsupport for the gravitational lensing hypothesis in GRB 990123.\n\nHjorth et al. also note that additional images of this GRB may appear on\na time scale of days to months due to differential lensing time delays.\n\nThe light from the host galaxy of GRB 990123 will also be affected by any\nstrong gravitational lensing which has influenced the burst and should\nshow strongly distorted and probably multiple images if the magnification\nfactor is large.  Detection and characterization of such lensed host galaxy\nimages would provide strong additional evidence for the lensing hypothesis\nbut, more importantly and much more urgently, would also allow detailed\nmodeling of the lensing mass distribution and geometry and, thus, far more\nprecise prediction of where and when additional images of the burst are\nexpected to occur.  \n\nThese predictions would make it far more practical (and economical of\nobserving resources) to detect and intensively study additional images\nof the burst as they appear.  Such data would not only be valuable for\nprobing the early stages of GRB physics but might also allow a sufficiently\nprecise determination of the time delay(s) to use for a measurement of\nthe cosmic distance scale.  Thus, deep and high resolution imaging in\nsearch of the possibly distorted and multiple images of the GRB 990123\nhost galaxy is urgently indicated.\n\nThis report may be cited.",
  "circularId": 221,
  "createdOn": 917284076000,
  "email": "elt@astro.princeton.edu",
  "subject": "GRB 990123 : Multiple and Distorted Images of the Host Galaxy?",
  "submitter": "Ed Turner at PrincetonU.  <elt@astro.princeton.edu>",
  "eventId": "GRB 990123"
}