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Home > Einstein Probe follow up > EP250821a

EP_FIELD00059

EP

59

/EP

EP250821a: Swift observation summary

Data analysed so far:

• ObsID: 03000033001 with 1.9 ks exposure.
• ObsID: 03000033002 with 3.0 ks exposure.

About tiled field analysis.

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

• 3000033 — 5.0 ks of cleaned data taken between 2025-08-21 08:40:42 and 2025-08-22 03:32:05

Details of afterglow candidates

1 sources were found which matches the afterglow criteria.

#	RA (J2000)	Dec (J2000)	Err901	Detection Flag2	Rank3	Dist from Einstein Probe/WXT pos	Exposure	Notes	Vizier
1 [details]	19h 19m 32.66s289.88608°	-43° 22′ 53.2″-43.38144°	5.0′′ *	Good	1 (T)	2.2′	17.3 ks	The source is fading with 4.4-σ significance. The source is 4.0-σ above the RASS limit.
Mean XRT rate: 4.85 (±0.27) ×10-2 ct s-1 Peak XRT rate: 0.52 (±0.12) ct s-1 RASS PSPC 3-σ upper limit: 0.06 ct s-1 (PSPC count-rate) Mean XRT rate converted to PSPC: 0.062 (±0.003) ct s-1 Peak XRT rate converted to PSPC: 0.67 (±0.15) ct s-1 Mean XRT flux: 1.70 (+0.10, -0.09) ×10-12 erg cm-1s-1 Peak XRT flux: 1.8 (±0.4) ×10-11 erg cm-1s-1 Products: Light curve | Spectrum | Enhanced position

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 8 sources have been found in the XRT data. 2 sources match catalogued sources.

#	RA (J2000)	Dec (J2000)	Err901	Detection Flag2	Rank3	Dist from Einstein Probe/WXT pos	Exposure	Notes	Vizier
1 [details]	19h 19m 32.66s289.88608°	-43° 22′ 53.2″-43.38144°	5.0′′ *	Good	1 (T)	2.2′	17.3 ks	The source is fading with 4.4-σ significance. The source is 4.0-σ above the RASS limit.
Mean XRT rate: 4.85 (±0.27) ×10-2 ct s-1 Peak XRT rate: 0.52 (±0.12) ct s-1 RASS PSPC 3-σ upper limit: 0.06 ct s-1 (PSPC count-rate) Mean XRT rate converted to PSPC: 0.062 (±0.003) ct s-1 Peak XRT rate converted to PSPC: 0.67 (±0.15) ct s-1 Mean XRT flux: 1.70 (+0.10, -0.09) ×10-12 erg cm-1s-1 Peak XRT flux: 1.8 (±0.4) ×10-11 erg cm-1s-1 Products: Light curve | Spectrum | Enhanced position
2 [details]	19h 19m 24.49s289.85206°	-43° 30′ 58.4″-43.51621°	5.9′′	Good	3 (U)	6.4′	17.3 ks
Mean XRT rate: 4.3 (+0.7, -0.6) ×10-3 ct s-1 Peak XRT rate: 5.0 (+1.5, -1.3) ×10-3 ct s-1 RASS PSPC 3-σ upper limit: 0.06 ct s-1 (PSPC count-rate) Mean XRT rate converted to PSPC: 6.03 (+1.01, -0.87) ×10-3 ct s-1 Peak XRT rate converted to PSPC: 7.1 (+2.2, -1.8) ×10-3 ct s-1 Mean XRT flux: 1.19 (+0.20, -0.17) ×10-13 erg cm-1s-1 Peak XRT flux: 1.4 (±0.4) ×10-13 erg cm-1s-1 Products: Light curve | Spectrum
3 [details]	19h 18m 49.03s289.70430°	-43° 20′ 51.3″-43.34757°	8.8′′	Good	3 (U)	7.6′	17.3 ks
Mean XRT rate: 3.6 (+1.3, -1.0) ×10-3 ct s-1 Peak XRT rate: 3.6 (+1.3, -1.0) ×10-3 ct s-1 RASS PSPC 3-σ upper limit: 0.11 ct s-1 (PSPC count-rate) Mean XRT rate converted to PSPC: 3.6 (+1.3, -1.1) ×10-3 ct s-1 Peak XRT rate converted to PSPC: 3.6 (+1.3, -1.1) ×10-3 ct s-1 Mean XRT flux: 1.5 (+0.5, -0.4) ×10-13 erg cm-1s-1 Peak XRT flux: 1.5 (+0.5, -0.4) ×10-13 erg cm-1s-1 Products: Light curve | Spectrum
4 [details]	19h 19m 16.13s289.81722°	-43° 29′ 00.6″-43.48350°	6.0′′	Poor	3 (U)	4.7′	17.3 ks	This source may be affected by optical loading Matches SIMBAD source: HD 180655, 2.8″ away.
Mean XRT rate: 3.3 (±1.1) ×10-3 ct s-1 Peak XRT rate: 3.3 (±1.1) ×10-3 ct s-1 RASS PSPC 3-σ upper limit: 0.04 ct s-1 (PSPC count-rate) Mean XRT rate converted to PSPC: 5.8 (±2.0) ×10-3 ct s-1 Peak XRT rate converted to PSPC: 5.8 (±2.0) ×10-3 ct s-1 Mean XRT flux: 7.8 (±2.6) ×10-14 erg cm-1s-1 Peak XRT flux: 7.8 (±2.6) ×10-14 erg cm-1s-1 Products: Light curve | Spectrum
5 [details]	19h 20m 14.78s290.06157°	-43° 26′ 24.6″-43.44017°	6.7′′	Good	3 (U)	9.1′	17.3 ks
Mean XRT rate: 3.5 (+0.8, -0.7) ×10-3 ct s-1 Peak XRT rate: 3.8 (+1.4, -1.1) ×10-3 ct s-1 RASS PSPC 3-σ upper limit: 0.80 ct s-1 (PSPC count-rate) Mean XRT rate converted to PSPC: 5.9 (+1.4, -1.1) ×10-4 ct s-1 Peak XRT rate converted to PSPC: 6.4 (+2.3, -1.9) ×10-4 ct s-1 Mean XRT flux: 3.4 (+0.8, -0.6) ×10-13 erg cm-1s-1 Peak XRT flux: 3.7 (+1.3, -1.1) ×10-13 erg cm-1s-1 Products: Light curve | Spectrum
6 [details]	19h 19m 33.86s289.89107°	-43° 23′ 27.7″-43.39104°	6.2′′	Poor	3 (U)	1.9′	17.3 ks	The source is fading with 3.8-σ significance. This source may be affected by optical loading Matches SIMBAD source: Gaia DR3 6712811885380654336, 13.6″ away.
Mean XRT rate: 1.31 (±0.20) ×10-2 ct s-1 Peak XRT rate: 4.8 (±1.3) ×10-2 ct s-1 RASS PSPC 3-σ upper limit: 0.07 ct s-1 (PSPC count-rate) Mean XRT rate converted to PSPC: 0.0150 (±0.0023) ct s-1 Peak XRT rate converted to PSPC: 0.056 (±0.015) ×10-2 ct s-1 Mean XRT flux: 4.4 (±0.7) ×10-13 erg cm-1s-1 Peak XRT flux: 1.6 (±0.4) ×10-12 erg cm-1s-1 Products: Light curve | Spectrum
7 [details]	19h 18m 25.47s289.60611°	-43° 20′ 16.1″-43.33781°	7.0′′	Poor	3 (U)	11.7′	17.3 ks
Mean XRT rate: 2.85 (+1.27, -0.99) ×10-3 ct s-1 Peak XRT rate: 2.85 (+1.27, -0.99) ×10-3 ct s-1 RASS PSPC 3-σ upper limit: 0.04 ct s-1 (PSPC count-rate) Products: Light curve | Spectrum
8 [details]	19h 20m 08.54s290.03560°	-43° 27′ 15.7″-43.45436°	5.6′′	Poor	3 (U)	8.3′	17.3 ks
Mean XRT rate: undetermined ct s-1 Peak XRT rate: undetermined ct s-1 RASS PSPC 3-σ upper limit: 0.13 ct s-1 (PSPC count-rate) Mean XRT rate converted to PSPC: undetermined ct s-1 Peak XRT rate converted to PSPC: undetermined ct s-1 Mean XRT flux: undetermined erg cm-1s-1 Peak XRT flux: undetermined 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.

Image

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FITS image.

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Exposure map

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FITS exposure map.