- GCN Circular #39041
C. Wu, D.-H. Zhao, W.-J. Xie (NAOC), S. Schanne (CEA), C.-W. Wang (IHEP), D. Götz (CEA)
report on behalf of the SVOM team:
The SVOM/ECLAIRs telescope triggered and located the long duration GRB 250127A (sb25012701) starting at 2025-01-27T05:04:46 UTC (Tb).
The following trigger information was received on the ground with low-latency by the SVOM VHF Alert Network.
The burst was detected by both the on-board Count-Rate Trigger (CRT) and Image Trigger (IMT) and 12 alerts were received. The best detection is obtained by IMT with a signal-to-noise ratio of 17.45 in the 8-120 keV energy band over a time window of 40.96 s starting at Tb. In the real-time light-curve the burst is well seen in the 5-50 keV band and not above.
The localization of the best Alert is RA, Dec = 169.589, 3.346 (J2000). The uncertainty on this position is 4.8 arcminutes at 90% C.L. which includes 2 arcminutes of systematic uncertainty in quadrature.
The SVOM/GRM light curve can be found here:
https://www.bursthub.cn//admin/static/svgrb250127A.png
SVOM performed an automatic slew on this burst, MXT and VT results will be reported later.
The Space 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 SVOM point of contact for this burst is: Donghua Zhao ( zhaodh@bao.ac.cn )
- GCN Circular #39043
D. Turpin, J. T. Palmerio, A. Saccardi (CEA), B. Schneider (LAM), S. Basa (UAR Pytheas, OHP, LAM), S. Vergani (GEPI/Obs. de Paris), E. Le Floc'h (CEA), C. Wu, L.-P Xin (NAOC) on behalf of a larger collaboration.
We observed the field of GRB 250127A detected by SVOM (Wu et al., GCN 39041) with the Sinistro instrument mounted on the 1-m telescope of the LCO network and the SCICAM QHY600 camera mounted on the 40 cm telescope, located at the Cerro Tololo, Chile. Our observation started at 2025-01-27T07:12:38.385 UTC (2.13 hr after the trigger) with a series of 2 x180s images using the PS1-z filter and 4 x 180s exposure using the sdss-r filter.
We did not detect any uncatalogued optical source inside the SVOM/ECLAIRs error region. We derived the preliminary following upper limit z > 17.8 (T-TGRB = 2.23h ,midtime) and r > 22.1 (T-TGRB = 2.32h ,midtime) given at 5 sigma (AB system) calibrated with the PanSTARRS DR2 catalog and not corrected for galactic extinction.
At the time of our observations, we note the presence of the minor planet designated as 2007 RT45 at RA, DEC (J2000): 11:18:42.1, +03:21:34 just outside the SVOM/ECLAIRs localisation error region.
This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101004719.
- GCN Circular #39044
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a ToO observation of the SVOM/ECLAIRs GRB 250127A.
Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00021757
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.
- GCN Circular #39047
SVOM/VT team: L.P. Xin, Y. L. Qiu, H.L. Li., C. Wu, D.H. Zhao, Z.H. Yao, Y.N. Ma, X.H. Han, J. Wang, W.J.Xie, H.B. Cai，J.Y. Wei（NAOC）， J. Palmerio (CEA) and S. Vergani (obs.Paris)
report on behalf of the SVOM team:
GRB 250127A (Wu et al., GCN 39041) was observed by SVOM/VT after the automatic slew of the platform. The VT conducted observations in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously.
With the VHF and X band downlinked data, no any credible candidates were found in our single or stacked images within either the errorbox of Eclairs (Wu et al., GCN 39041), or the errorbox of source #2 detected by Swift/XRT (Swift Team,GCN 39044). The 3 sigma limits in AB magnitude were derived as follows:
---------------------------------------------------------
(t-T0)_mid(min) exptime(s) Band upperlim(3sigma)
2.5 15 VT_B 20.6
2.5 15 VT_R 20.3
78.08 23*100 VT_B 23.6
79.75 23*100 VT_R 23.4
147.38 48*100+15 VT_B 23.9
147.01 46*100+2*15 VT_R 23.7
This is consistent with the non-detection report (Turpin et al., GCN 39043).
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.
- GCN Circular #39053
Y.-H. I. Yin (NJU), Y. L. Wang, H. N. Yang, H. Y. Liu (NAO, CAS), Z. Y. Liu, M. Q. Huang (USTC), Z. X. Ling, Y. Liu (NAO, CAS), B. Cordier (CEA) on behalf of the Einstein Probe team:
We performed a follow-up observation of GRB 250127A (SVOM, Wu et al., GCN 39041) with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission. The observation started at 2025-01-27 11:29:09 (UTC) with ~ 2.4 ks of exposure in total.
An uncatalogued X-ray source is detected by both modules of FXT at the position of R. A. = 169.6284 deg, DEC = 3.3508 deg (J2000) with an uncertainty of 10 arcsec (90% C. L.), which is 2.38 arcmin away from the SVOM position (Wu et al., GCN 39041). This position is also consistent with the location of Swift/XRT Source 2 (P. A. Evans, GCN 39044). The average FXT 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic equivalent hydrogen column density of 4.52 x 10^20 cm^-2 and a photon index of 1.79 (-0.92/+0.92). The derived average unabsorbed 0.5-10 keV flux is 1.30 (-0.68/+1.44) x 10^(-13) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters.
Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). EP is a mission of the Chinese Academy of Sciences in collaboration with ESA, MPE and CNES.
- GCN Circular #39056
J.A. Kennea (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U.
Leicester), B. Sbarufatti (INAF-OAB), C. Salvaggio (INAF-OAB), M. Ferro
(INAF-OAB), D.N. Burrows (PSU), M. A. Williams (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 250127A, collecting 2.9 ks of Photon
Counting (PC) mode data between T0+18.3 ks and T0+25.4 ks.
One uncatalogued X-ray sources have been detected within the estimated
90% SVOM/ECLAIRs error region (4.8 arcmin; GCN Circ. 39041), it is
below the RASS limit and shows no definitive signs of fading in the two
snapshot of observations that were taken. Details of this source are
given below:
Source 2:
RA (J2000.0): 169.6282 = 11:18:30.76
Dec (J2000.0): +3.3518 = +03:21:06.4
Error: 8.6 arcsec (radius, 90% conf.)
Count-rate: (2.9 [+1.5, -1.1])e-3 ct s^-1
Distance: 138 arcsec from SVOM/ECLAIRs position.
Flux: (3.3 [+1.7, -1.3])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)
The source was also detected by the FXT telescope on board of Einstein
Probe (GCN Circ. 39053), which observed this field around the same time
of the XRT observations.
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/00021757.
This circular is an official product of the Swift-XRT team.
- GCN Circular #39083
N. Pankov (HSE, IKI), A. Pozanenko (IKI), V. Rumyantsev (CrAO), I. Sokolov (INASAN) report on behalf of the IKI-GRB-FuN:
We performed optical observations of the field of GRB 250127A (Wu et. al, GCN 39041; Turpin et. al, GCN 39043; Evans, GCN 39044; Xin et. al, GCN 39047; Yin et. al, GCN 39053; Kennea et. al, GCN 39056) in the R-filter using the 2.6-meter ZTSh telescope of the Crimean Astrophysical Observatory (CrAO), and in Clear light with the 0.8-meter K-800 telescope of the Terskol Observatory (INASAN). The observations began on 2025-01-27 23:27 UT, i.e. ~0.022 days since SVOM trigger. We do not detect any new sources spatially consistent with the X-Ray afterglow position reported by the Swift XRT team (Kennea et. al, GCN 39056) and the EP-FXT team (Yin et. al, GCN 39053). The preliminary upper limits are given below:
Date UT start t-T0 Exp. Filter UL(3sigma) Telescope
(mid, days) (s)
2025-01-27 23:27:51 0.02251 87*30 Clear 18.2 K-800
2025-01-28 00:08:00 0.80364 14*120 R 23.7 ZTSh
The photometry has calibrated using nearby stars from the USNO-B1.0 catalog (R2 magnitudes). No correction has been made for the Galactic extinction A_R = 0.119 (Schlegel & Finkbeiner, 1998).
- GCN Circular #39095
Y.-H. I. Yin (NJU), Y. L. Wang, H. N. Yang, H. Y. Liu (NAO, CAS), Z. Y. Liu, M. Q. Huang (USTC), Z. X. Ling, Y. Liu (NAO, CAS), B. Cordier, D. Turpin (CEA) on behalf of the Einstein Probe team:
We performed a second follow-up observation of GRB 250127A (SVOM, Wu et al., GCN 39041) with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission. The observation started at 2025-01-29 09:55:45 (UTC) with ~ 4.9 ks of exposure in total.
The uncatalogued x-ray source detected by both Swift/XRT (Source 2, Kennea et al., GCN 39056) and EP-FXT (Yin et al. GCN 39053) is no longer detected in our second EP-FXT epoch. Assuming Galactic equivalent hydrogen column density of 4.52 x 10^20 cm^-2 and a photon index of 2.0, the upper limit of the 0.5-10 keV flux is estimated to be 1.93 x 10^-14 erg/s/cm^2. The fading behavior of the x-ray source identified by Yin et al. GCN 39053 and Kennea et al., GCN 39056, confirms it as being the afterglow of GRB 250127A.
Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). EP is a mission of the Chinese Academy of Sciences in collaboration with ESA, MPE and CNES.
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