TITLE: GCN CIRCULAR NUMBER: 41613 SUBJECT: GRB 250830B: Swift-XRT observations DATE: 25/08/31 04:57:05 GMT FROM: Phil Evans at U of Leicester pae9@star.le.ac.uk
A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), J.A. Kennea (PSU), D.N. Burrows (PSU), S. Lanava (PSU) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:
Swift-XRT has performed follow-up observations of the MAXI-detected burst GRB 250830B, collecting 2.4 ks of Photon Counting (PC) mode data between T0+11.0 ks and T0+50.8 ks. This event also triggered Einstein Probe around 25 s after MAXI, and was separately designated EP250830a.
One uncatalogued X-ray source has been detected within the estimated 3-sigma EP error region (296 arcsec), also consistent with the MAXI error region; it is below the RASS limit and shows no definitive signs of fading. Therefore, at the present time we cannot confirm this as the afterglow. Details of this source are given below:
Source 1: RA (J2000.0): 105.7399 = 07h 02m 57.59s Dec (J2000.0): -64.8525 = -64d 51' 09.1" Error: 3.7 arcsec (radius, 90% conf. [Enhanced position]) Count-rate: 0.0323 +/- 0.0046 ct s^-1 Distance: 134 arcsec from EP position. Flux: (1.74 +/- 0.25)e-12 erg cm^-2 s^-1 (observed, 0.3-10 keV)
A further uncatalogued X-ray source was also detected, however this was too far from the EP position to be the afterglow.
The 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/ToO_GRBs/00021858.
This circular is an official product of the Swift-XRT team.
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