{
  "body": "S. P. R. Shilling (Lancaster U.) reports on behalf of the Swift UVOT team:\n \nSwift/UVOT observed the field of EP250304a (Chen et al., GCN 39580) for a total of 2 ks\nin the U-band starting at 02:48:13 UT, 1.25 hours after the detection by Einstein Probe WXT.\n \nAn optical source consistent with the EP-FXT position (Chen et al., GCN 39580) is detected and\nappears to be rising in brightness. The preliminary detection magnitudes reported below\nare calculated using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373).\nThe magnitude at the start of the observation is 19.29 +/- 0.09 (1.25 hours post trigger)\nand rises to 18.91 +/- 0.15 (~2.75 hours post trigger).\n \nWe note that an X-ray source at this position was independently observed by the\nSwift/XRT (Page et al., GCN 39584). We also note that, in addition to the Swift/UVOT detection,\nan optical counterpart at this position has been detected by the TRT (Liu et al., GCN 39583)\nbut has not been detected by MASTER (Lipunov et al., GCN 39581). Finally, that the source\nhas a spectroscopic redshift, observed with the VLT/X-shooter, of z=0.2 (Saccardi et al., GCN 39585).",
  "eventId": "EP250304a",
  "bibcode": "2025GCN.39587....1S",
  "circularId": 39587,
  "submittedHow": "web",
  "submitter": "Sam Shilling at Lancaster University <shilling.sam@gmail.com>",
  "createdOn": 1741090689814,
  "subject": "EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve",
  "format": "text/plain"
}