GRB 250317B: Swift observation summary

This is a confirmed GRB (GRB 250317B), the afterglow is source 1 -- please see the GRB results at https://www.swift.ac.uk/xrt_products/00019621 for updated analysis

Mission:	SVOM/ECLAIRs
SVOM RA:	211.608°
SVOM Dec:	+40.051°
SVOM Err:	6.3 arcmin
T0:	2025-03-17 02:12:18 UT
Galactic:	77.48° +69.80°
Galactic N_H:	9.95× 10¹⁹ cm^-2

Sun distance:	130.06°
Sun angle:	9.68 [hr](West of Sun)
Moon distance:	53.39°
Visibility of this field.
First slew:	2025-03-17 05:00:34 UT
First observation:	2025-03-17 04:59:55 UT
First analysis:	2025-03-17 07:57:10 UT

Data analysed so far:

ObsID: 00019621001 with 1.7 ks exposure.
ObsID: 00019621003 with 1.5 ks exposure.

About tiled field analysis.

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

19621 — 3.2 ks of cleaned data taken between 2025-03-17 05:00:25 and 2025-03-18 04:33:26

Details of afterglow candidates

1 sources were found which matches the afterglow criteria.

#	RA (J2000)	Dec (J2000)	Err₉₀¹	Detection Flag²	Rank³	Dist from SVOM/ECLAIRs pos	Exposure	Notes	Vizier
1 [details]	14h 06m 34.27s211.64281°	+40° 04′ 47.7″40.07991°	3.9′′	Good	2 (O)	2.4′	3.2 ks	The source is fading with 4.4-σ significance. The source is 3.9-σ above the LSPXS limit.
Mean XRT rate: 8.7 (±0.8) ×10^-2 ct s^-1 Peak XRT rate: 0.19 (±0.04) ct s^-1 RASS PSPC 3-σ upper limit: 0.01 ct s^-1 (PSPC count-rate) Mean XRT rate converted to PSPC: 0.214 (±0.020) ct s^-1 Peak XRT rate converted to PSPC: 0.46 (±0.10) ct s^-1 Mean XRT flux: 3.05 (±0.29) ×10^-12 erg cm^-1s^-1 Peak XRT flux: 6.5 (±1.5) ×10^-12 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 2 sources have been found in the XRT data. 1 sources match catalogued sources.

#	RA (J2000)	Dec (J2000)	Err₉₀¹	Detection Flag²	Rank³	Dist from SVOM/ECLAIRs pos	Exposure	Notes
1 [details]	14h 06m 34.27s211.64281°	+40° 04′ 47.7″40.07991°	3.9′′	Good	2 (O)	2.4′	3.2 ks	The source is fading with 4.4-σ significance. The source is 3.9-σ above the LSPXS limit.
Mean XRT rate: 8.7 (±0.8) ×10^-2 ct s^-1 Peak XRT rate: 0.19 (±0.04) ct s^-1 RASS PSPC 3-σ upper limit: 0.01 ct s^-1 (PSPC count-rate) Mean XRT rate converted to PSPC: 0.214 (±0.020) ct s^-1 Peak XRT rate converted to PSPC: 0.46 (±0.10) ct s^-1 Mean XRT flux: 3.05 (±0.29) ×10^-12 erg cm^-1s^-1 Peak XRT flux: 6.5 (±1.5) ×10^-12 erg cm^-1s^-1 Products: Light curve \| Spectrum \| Enhanced position
2 [details]	14h 06m 28.61s211.61922°	+40° 09′ 22.2″40.15617°	6.6′′	Good	3 (U)	6.3′	3.2 ks	Matches SIMBAD source: SDSS J140628.79+400919.2, 3.6″ away.
Mean XRT rate: 4.0 (+2.3, -1.7) ×10^-3 ct s^-1 Peak XRT rate: 4.0 (+2.3, -1.7) ×10^-3 ct s^-1 RASS PSPC 3-σ upper limit: 0.01 ct s^-1 (PSPC count-rate) Mean XRT rate converted to PSPC: 0.013 (+0.008, -0.006) ×10^-2 ct s^-1 Peak XRT rate converted to PSPC: 0.013 (+0.008, -0.006) ×10^-2 ct s^-1 Mean XRT flux: 1.1 (+0.7, -0.5) ×10^-13 erg cm^-1s^-1 Peak XRT flux: 1.1 (+0.7, -0.5) ×10^-13 erg cm^-1s^-1 Products: Light curve \| Spectrum

Image

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Exposure map

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FITS exposure map.