GRB 250213A

Yun Wang (PMO), Wen-Jin Xie (NAOC), J.-L. Atteia (IRAP), N. Dagoneau (CEA), F. Piron (LUPM), Li Zhang (IHEP)

report on behalf of the SVOM mission team.

At 2025-02-13T23:46:24 UTC (Tb) SVOM/ECLAIRs triggered on the gamma-ray burst GRB 250213A (SVOM burst-id sb25021316).
The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network.

The burst was only detected by the Image Trigger (IMT), which produced a sequence of 2 alerts. IMT provided the alert with the best signal-to-noise-ratio (SNR) of 7.50 in the [8-50] keV energy band over a time window of 20.48 seconds starting at Tb.

The localization of the best alert is R.A., Dec 112.4888, -20.0967 degrees:
RA (J2000) = 7h29m57.31s
Dec (J2000) = -20d05m48.10s
with a 90% C.L. radius of 10.46 arcmin (including systematic error of 2 arcmin added in quadrature).

A SVOM follow-up ToO observation has been scheduled. 

The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe.

The Burst Advocate (BA) on shift for this burst is Yun Wang (wangyun@pmo.ac.cn)
Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst.

P. A. Evans (U. Leicester) reports on behalf of the Swift team:

Swift has initiated a ToO observation of the SVOM/ECLAIRs GRB 250213A. 
Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00021777

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the SVOM/ECLAIRs event. Any X-ray source
considered to be a probable afterglow candidate will be reported via a 
GCN Circular after manual consideration.

Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).

This circular is an official product of the Swift-XRT team.

L.P. Xin, Y.L. Qiu, H.L. Li(NAOC), Y. Wang(PMO), W.J. Xie, C. Wu, Z.H. Yao, Y.N. Ma, X.H. Han, H.B. Cai, J. Wang, J.Y. Wei (NAOC), report on behalf of the SVOM team:

The SVOM/VT conducted follow-up observations of the GRB 250213A (Wang et al., GCN 39317
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 ) in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously. 

With the X band downlinked data, an uncatalogued optical source was detected within the errorbox of XRT2 (Evens et al., GCN 39321
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 ) in VT_R stacked image, compared to the Pan-STARRS DR1 catalog. 

The brightness of the source was estimated to be 22.5 +/-0.2 mag in AB magnitude in VT_R image at the mid time of 3.28 hours post the burst, with a total exposure time of 42*100 seconds. 

The source is located at RA, Dec =112.55872, =-19.94929, which is equivalent to:

RA (J2000) : 07:30:14.1
Dec (J2000): -19:56:57.44
with an uncertainty of 0.5 arcsec.

Based on the data available, we are not sure wether it is a persistent source or the candidate for the burst. 
More deep follow-ups are encouraged to confirm the nature of the source. 

The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC),CAS.

Jean-Grégoire Ducoin (CPPM), Alan M. Watson (UNAM), Rosa L. Becerra (U Roma), Jean-Luc Atteia (IRAP), Benjamin Schneider (LAM) Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Dalya Akl (AUS), Camila Angulo (UNAM), Sarah Antier (OCA), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Francesco Magnani (CPPM), Margarita Pereyra (UNAM), and Ny Avo Rakotondrainibe (LAM) report:

We imaged the field of the SVOM/ECLAIRs GRB 250213A (Wang et al., GCN Circ. 39317
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 ) with the DDRAGO wide-field imager on the COLIBRÍ telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico.

We observed from 2025-02-15 02:22 UTC to 09:19 UTC (T+1.11 to T+1.40 days after the trigger) and obtained 229 minutes of exposure in the r filter under very poor seeing conditions. The data were coadded with the COLIBRÍ pipeline and analyzed in STDWeb/STDPipe (Karpov 2021), with photometric calibration against Pan-STARRS DR1 and image subtraction against Pan-STARRS DR2.

Our field includes the position of the SVOM/VT optical afterglow candidate (Xin et al., GCN Circ. 39325
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 ) and the X-ray sources #2 (consistent with the VT source) and #3 (consistent with the SVOM/ECLAIRs uncertainty) in the Swift/XRT ToO observations (Evans et al., GCN Circ. 39321
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 ).

At the position of the SVOM/VT optical candidate, after image subtraction, we do not detect a point source to a 3-sigma limit of:

	r > 22.8

Within the uncertainty region of XRT source #3, we do not detect any point sources to a 3-sigma limit of:
	r > 22.5

Our magnitude limits are not corrected for the substantial Galactic extinction in the direction of this burst, estimated to be A_V = 2.46 or A_r = 2.05 (Schlafly & Finkbeiner, 2011).

We warmly thank the COLIBRÍ and DDRAGO engineering teams and the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir.

J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore
(U. Leicester), M. Capalbi (INAF-IASFPA), M. Perri (SSDC & INAF-OAR),
V. D'Elia (SSDC & INAF-OAR), M. A. Williams (PSU), S. Dichiara (PSU),
J.A. Kennea (PSU) and P.A. Evans (U. Leicester) reports on behalf of
the Swift-XRT team:

Swift-XRT has performed follow-up observations of the
SVOM/ECLAIRs-detected burst GRB 250213A, collecting  3.3 ks of Photon
Counting (PC) mode data between T0+26.1 ks and T0+50.5 ks. 

Three uncatalogued X-ray sources have been detected, however none of
them is above the RASS limit or shows definitive signs of fading.
Therefore, at the present time we cannot identify which, if any, is the
afterglow. Details of these sources are given below:

Source 2:
  RA (J2000.0):  112.5572  =  07:30:13.74
  Dec (J2000.0): -19.9494  =  -19:56:57.9
  Error: 9.1 arcsec (radius, 90% conf. [Enhanced position])
  Count-rate: (5.8 [+2.0, -1.6])e-3 ct s^-1   
  Distance: 578 arcsec from SVOM/ECLAIRs position.
  Flux: (4.2 [+1.4, -1.2])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 3:
  RA (J2000.0):  112.5390  =  07:30:9.37
  Dec (J2000.0): -20.1093  =  -20:06:33.6
  Error: 6.4 arcsec (radius, 90% conf.)
  Count-rate: (3.4 [+1.4, -1.2])e-3 ct s^-1   
  Distance: 175 arcsec from SVOM/ECLAIRs position.
  Flux: (6.4 [+2.7, -2.2])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 4:
  RA (J2000.0):  112.2781  =  07:29:6.75
  Dec (J2000.0): -20.0889  =  -20:05:19.9
  Error: 6.3 arcsec (radius, 90% conf.)
  Count-rate: (3.0 [+1.6, -1.2])e-3 ct s^-1   
  Distance: 712 arcsec from SVOM/ECLAIRs position.
  Flux: (5.9 [+3.1, -2.3])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)

A catalogued source was also detected.

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/00021777.

This circular is an official product of the Swift-XRT team.