{
  "bibcode": "2022GCN.31966....1D",
  "body": "V. D���Elia (ASI-SSDC & INAF-OAR) and M. H. Siegel (PSU)\r\nreport on behalf of the Swift team:\r\n\r\nSwift has performed follow-up observations of the Fermi/GBM-detected burst GRB 220426A (GCN Circ. 31950, 31955), which was also detected by Swift/BAT-GUANO (GCN Circ. 31954), Konus-Wind (GCN Circ. 31959), INTEGRAL/SPI-ACS, and HEND/Mars-Odyssey (GCN Circ. 31958).\r\n\r\nThe XRT observations consist of three tiles of 1 ks each, to cover the GRB error region. The data were acquired between 45 and 47 hours after the burst and are entirely in PC mode.\r\n\r\nOne bright, uncatalogued X-ray source has been detected:\r\n\r\nSource 1:\r\n  RA (J2000.0): 22h 32m 34.33s\r\n  Dec (J2000.0): -22�� 57��� 01.0���\r\n  Error: 3.7 arcsec (radius, 90% conf.)\r\n  Count-rate: (1.4 +/- 0.5)e-2 ct s^-1\r\n  Distance: 3.2 arcmin from the IPN position\r\n  Flux: (4.1 +/- 1.4)e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)\r\n\r\nNevertheless, we note that at the XRT position the RASS PSPC 3 sigma upper limit is 0.05 cts/s (XRT equivalent count-rate).\r\n\r\nThe UVOT took images of 616s each on the three XRT tiles with the white filter 160-170 ks after the trigger. We identify one source at 1.9��� from the XRT coordinates of Source 1,  with a white magnitude of 18.01.\r\n\r\nThe UVOT position is:\r\n   RA  (J2000) =  22:32:34.39 = 338.14330 (deg.)\r\n   Dec (J2000) = -22:57:02.7  =  22.95074 (deg.)\r\n\r\nwith an estimated uncertainty of 0.5 arc sec. (radius, 90% confidence).\r\n\r\nHowever, we note that this is a known source in the DSS and is therefore unlikely to be the afterglow. No other sources are detected to a limiting magnitude in the white filter of 20.8.\r\n\r\nMore Swift observations are planned in the next days to assess for variability\r\n\r\nThe results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/xrt_products/TILED_GRB00104/<https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.swift.ac.uk%2Fxrt_products%2FTILED_GRB00104%2F&data=05%7C01%7Cvalerio.delia%40ssdc.asi.it%7Cbbf1b046abbf47f102b008da29348927%7Ccbfc58d4e60f468d8fe490676de085f7%7C0%7C0%7C637867602862749464%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=rivAVi0hBq7OV9vDQ4K1Xb1mbfcuxK9etLjffE3p1UI%3D&reserved=0>.\r\n\r\nThis circular is an official product of the Swift team.",
  "circularId": 31966,
  "createdOn": 1651167091000,
  "email": "valerio.delia@ssdc.asi.it",
  "subject": "GRB 220426A: Swift-XRT and UVOT observations",
  "submitter": "Valerio D'Elia at ASDC  <valerio.delia@ssdc.asi.it>",
  "eventId": "GRB 220426A"
}