{
  "bibcode": "2018GCN.22665....1S",
  "body": "M. H. Siegel (PSU) and V. D'Elia (ASDC)\nreport on behalf of the Swift/UVOT team:\n\nThe Swift/UVOT began settled observations of the field of GRB 180418A\n3086 s after the BAT trigger (D'Elia et al., GCN Circ. 22646).\nA fading source consistent with the XRT position\n(Goad et al. GCN Circ. 22650)\nis detected in the initial UVOT exposures, confirming the previously\nreported optical afterglows (Zheng & Filippenko, GCN Circ. 22647; Guidorzi\net al., GCN Circ. 22648; Troja et al., GCN Circ. 22652; Fong et al., GCN\nCirc. 22659; Malesani et al., GCN Circ. 22660; Schady et al., GCN Circ. 22662;\nMisra et al., GCN Circ. 22663).\n\nThe preliminary UVOT position is:\n   RA  (J2000) =  11:20:29.21 = 170.12172 (deg.)\n   Dec (J2000) = +24:55:59.2  =  24.93311 (deg.)\nwith an estimated uncertainty of 0.49 arc sec. (radius, 90% confidence).\n\nPreliminary detections and 3-sigma upper limits 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)        3087         3236          147         19.19+-0.11\nwhite             3087         4470          344         19.45+-0.09\nwhite            49806        72093         4850        >22.62\nv                 3243         4835          347        >19.53\nb                 4064         4264          196        >20.19\nb                15510        16114          590        >20.82\nu (fc)            3859         4059          196         19.35+-0.24\nu                14598        31858          894        >20.73\nuvw1              3655         3855          196         19.19+-0.28\nuvw1              9720        27635         1206         20.02+-0.21\nuvm2              3450         3649          196         18.93+-0.27\nuvm2              8814        26975         2165         20.65+-0.26\nuvw2              4476         4676          196        >19.69\n\nThe magnitudes in the table are not corrected for the Galactic extinction\ndue to the reddening of E(B-V) = 0.02 in the direction of the burst\n(Schlegel et al. 1998).",
  "circularId": 22665,
  "createdOn": 1524175517000,
  "email": "siegel@swift.psu.edu",
  "subject": "GRB 180418A: Swift/UVOT Detection",
  "submitter": "Mike Siegel at PSU/Swift MOC  <siegel@swift.psu.edu>",
  "eventId": "GRB 180418A"
}