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.

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
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.