EP250704a: Swift observation summary

This is a confirmed GRB (GRB 250704B), the afterglow is source 2 -- please see the GRB results at https://www.swift.ac.uk/xrt_products/00019908 for updated analysis

Mission:	Einstein Probe/WXT
Einstein Probe RA:	300.872°
Einstein Probe Dec:	+12.030°
Einstein Probe Err:	3.1 arcmin
T0:	2025-07-04 08:16:52 UT
Galactic:	52.10° -10.03°
Galactic N_H:	9.66× 10²⁰ cm^-2

Sun distance:	141.10°
Sun angle:	10.84 [hr] (West of Sun)
Moon distance:	97.71°
Visibility of this field.
First slew:	2025-07-04 08:46:40 UT
First observation:	2025-07-04 08:46:13 UT
First analysis:	2025-07-04 11:41:13 UT

Data analysed so far:

ObsID: 00019908001 with 1.7 ks exposure.

About tiled field analysis.

So far 1 fields have been scheduled for observations. Data are available and processed for 1 of these.

1 fields were processed but not included in the analysis. This is because, after standard processing and the removal of times contaminated by light reflected off the bright Earth, there was too little data (<100 s) for source detection to be performed.

Details of afterglow candidates

1 sources were found which matches the afterglow criteria.

#	RA (J2000)	Dec (J2000)	Err₉₀¹	Detection Flag²	Rank³	Exposure	Notes	Vizier
2 [details]	20h 03m 29.18s300.87158°	+12° 01′ 23.9″12.02331°	3.6′′	Reasonable	2 (O)	0.4′	1.7 ks	The source is 4.1-σ above the RASS limit.
Mean XRT rate: 0.247 (±0.017) ct s^-1 Peak XRT rate: 0.39 (±0.09) ct s^-1 RASS PSPC 3-σ upper limit: 0.03 ct s^-1 (PSPC count-rate) Mean XRT rate converted to PSPC: 0.316 (±0.021) ct s^-1 Peak XRT rate converted to PSPC: 0.50 (±0.11) ct s^-1 Mean XRT flux: 8.8 (±0.6) ×10^-12 erg cm^-1s^-1 Peak XRT flux: 1.4 (±0.3) ×10^-11 erg cm^-1s^-1 Products: Light curve \| Spectrum

¹ Radius, 90% confidence.
² Indicates how likely the source is to be real. See the LSXPS documentation.
³ T=Transient Source, O=Outbursting known source, U=Uncatalogued X-ray source, K=Known X-ray source.
^* The position was enhanced using astrometry derived from the Swift UVOT.
^† The position was astrometrically corrected using the XRT sources and the 2MASS catalogue.

Find an upper limit.

Sources found so far

So far 2 sources have been found in the XRT data. 1 sources match catalogued sources.

#	RA (J2000)	Dec (J2000)	Err₉₀¹	Detection Flag²	Rank³	Dist from Einstein Probe/WXT pos	Exposure	Notes
1 [details]	20h 03m 18.52s300.82718°	+12° 09′ 49.0″12.16362°	3.9′′	Good	3 (U)	8.4′	1.7 ks	This source may be affected by optical loading Matches SIMBAD source: Gaia DR3 1805949089882861568, 1.2″ away.
Mean XRT rate: 2.0 (±0.5) ×10^-2 ct s^-1 Peak XRT rate: 2.0 (±0.5) ×10^-2 ct s^-1 RASS PSPC 3-σ upper limit: 0.03 ct s^-1 (PSPC count-rate) Mean XRT rate converted to PSPC: 0.033 (±0.008) ct s^-1 Peak XRT rate converted to PSPC: 0.033 (±0.008) ×10^-2 ct s^-1 Mean XRT flux: 7.5 (±1.7) ×10^-13 erg cm^-1s^-1 Peak XRT flux: 7.5 (±1.7) ×10^-13 erg cm^-1s^-1 Products: Light curve \| Spectrum
2 [details]	20h 03m 29.18s300.87158°	+12° 01′ 23.9″12.02331°	3.6′′	Reasonable	2 (O)	0.4′	1.7 ks	The source is 4.1-σ above the RASS limit.
Mean XRT rate: 0.247 (±0.017) ct s^-1 Peak XRT rate: 0.39 (±0.09) ct s^-1 RASS PSPC 3-σ upper limit: 0.03 ct s^-1 (PSPC count-rate) Mean XRT rate converted to PSPC: 0.316 (±0.021) ct s^-1 Peak XRT rate converted to PSPC: 0.50 (±0.11) ct s^-1 Mean XRT flux: 8.8 (±0.6) ×10^-12 erg cm^-1s^-1 Peak XRT flux: 1.4 (±0.3) ×10^-11 erg cm^-1s^-1 Products: Light curve \| Spectrum

Image

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FITS image.

Exposure map

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FITS exposure map.