{
  "bibcode": "2021GCN.30247....1S",
  "body": "M. H. Siegel (PSU), M. Baer (PSU) and K. L. Page (U. Leicester)\nreport on behalf of the Swift/UVOT team:\n\nThe Swift/UVOT began settled observations of the field of GRB 210610B\n92 s after the BAT trigger (Page et al., GCN Circ. 30170). A fading source consistent\nwith the XRT position (Osborne et al. GCN Circ. 30189) and the previously reported\noptical counterpart (Kumar et al., GCN Circ. 30174; Rumyantsev et al. GCN Circ.\n30175; Hu et al., GCN Circ. 30177; de Wet et al., GCN Circ. 30180; Romanov, GCN Circ.\n30181; Fynbo et al., GCN Circ. 30182; Moskvitin, GCN Circ. 30187; Fu et al., GCN Circ.\n30188) is detected in the initial UVOT exposures.\n\nThe preliminary UVOT position is:\n   RA  (J2000) =  16:15:40.40 = 243.91833 (deg.)\n   Dec (J2000) = +14:23:56.9  =  14.39915 (deg.)\nwith an estimated uncertainty of 0.42 arc sec. (radius, 90% confidence).\n\nPreliminary detections using the UVOT photometric system\n(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: \n\nFilter         T_start(s)   T_stop(s)      Exp(s)           Mag\n\nwhite (fc)          92          242          147      13.63+/-1.10\nwhite              584         1355          225      15.24+/-0.02\nwhite           172034       172423          377      20.22+/-0.14\nwhite           286441       292869          328      20.71+/-0.23\nwhite           452008       515231         4066      21.69+/-0.16\nv                  634         1405           97      15.63+/-0.05\nv                 6631        51903          659      18.26+/-0.09\nb                  560         1331           77      15.78+/-0.04\nb                81150       133027          865      20.08+/-0.14\nu (fc)             304          554          245      13.86+/-0.03\nu                  707         1306           58      14.93+/-0.04\nu                 4850         5040          186      16.68+/-0.05\nu                45786        46567          761      18.06+/-0.05\nu               131743       132650          885      20.00+/-0.18\nu               365977       418267         3970      21.42+/-0.29\nuvw1               683         1282           58      14.51+/-0.06\nuvw1              4645         4845          196      16.26+/-0.07\nuvw1              7041        45779          989      17.54+/-0.06\nuvw1            125974       137480          881      19.53+/-0.20\nuvw1            200561       247267         1111      19.95+/-0.24\nuvm2              6836         7036          196      16.61+/-0.10\nuvw2               783         1034           38      15.05+/-0.09\nuvw2             50521        51421          885      18.44+/-0.10\n\nThe magnitudes in the table are not corrected for the Galactic extinction\ndue to the reddening of E(B-V) = 0.044 in the direction of the burst\n(Schlegel et al. 1998).",
  "circularId": 30247,
  "createdOn": 1623937038000,
  "email": "mhs18@psu.edu",
  "subject": "GRB 210610B: Swift/UVOT Detection",
  "submitter": "Mike Siegel at PSU/Swift MOC  <mhs18@psu.edu>",
  "eventId": "GRB 210610B"
}