GRBweb by P. Coppin

This page lists all entries on GRB250416C in GRBweb

Summary GCN 40167 GCN 40184 GCN 40219

Summary table
Variable	Value	Source
T0	17:53:59 UTC	GCN_circulars,Konus-Wind Det
ra	256.4228°	GCN_circulars,Konus-Wind Det
decl	25.7755°	GCN_circulars,Konus-Wind Det
redshift	0.9630	GCN_circulars,Optical
GBM_located	False
mjd	60781.74582175926	GCN_circulars,Konus-Wind Det

GCN 40167 table
GRB_name	GRB250416C
GCN_number	40167
Detection_method	Konus-Wind Det
t_trigger	17:53:59 UTC
Circular_text	TITLE: GCN CIRCULAR NUMBER: 40167 SUBJECT: Konus-Wind detection of GRB 250416C (a counterpart of EP250416a) DATE: 25/04/18 17:38:33 GMT FROM: Dmitry Svinkin at Ioffe Institute D. Svinkin, D. Frederiks, A.Lysenko, A. Ridnaya, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long-duration GRB 250416C was detected by Konus-Wind (KW) in the waiting mode at about T0=64427 s UT (17:53:47). A Bayesian block analysis of the KW waiting mode data in the 20-400 keV band reveals a ~7 sigma count-rate increase in the interval from T0-6.3 s to T0+11.4 s. The KW light curve of this burst is available at http://www.ioffe.ru/LEA/GRBs/GRB250416C/ The total burst fluence is 1.50(-0.42,+1.04)x10^-6 erg/cm^2, and the 2.944 s peak energy flux, measured from T0-0.405 s, is 1.57(-0.57,+1.15)x10^-7 erg/cm^2. (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum of the burst, measured from T0-6.3 s to T0+11.4 s, can be described by a power law with exponential cutoff (CPL) model dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -1.35(-0.36,+0.66) and Ep = 228(-110,+735) keV. The burst was detected simultaneously with the fast X-ray transient EP250416a (T0(EP)=17:53:59 UT; Zhao et al., GCN 40154; Zhou et al., GCN 40165). The positional and temporal coincidence of this burst with the transient supports the conclusion that the EP250416a is the GRB counterpart. All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary.

GCN 40184 table
GRB_name	GRB250416C
GCN_number	40184
Detection_method	Konus-Wind Det
ra	256.4228°
decl	25.7755°
Circular_text	TITLE: GCN CIRCULAR NUMBER: 40184 SUBJECT: GRB 250416C / EP250416a: SVOM/GRM observation of a burst DATE: 25/04/20 12:06:30 GMT FROM: Chenwei Wang at IHEP SVOM/GRM team: Chen-Wei Wang, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Maria-Grazia Bernardini (INAF-OAB), Stéphane Schanne (CEA), Frédéric Piron (LUPM) Report on behalf of the SVOM team: SVOM/GRM was triggered on-ground by GRB 250416C at 2025-04-16T17:53:48 (T0). This burst was also detected by Konus-Wind (D. Svinkin et al, GCN 40167) and EP (Zhao et al., GCN 40154; Zhou et al., GCN 40165). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a single pulse with a T90 of 8 +4/-4 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250416C.png The time coincidence and relative counts of each detectors of GRM suggest that this GRB is associated with EP250416a. In addition, the position of this burst, which is determined by EP/FXT (GCN 40154, RA: 256.4228 deg, DEC: 25.7755 deg, Error: 20 arcsec), located at about 83 degrees from the SVOM optical axis, and was outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-10 to T0+10 s is best fitted by a power law function. The power law index is -2.04 +0.19/-0.26. The event fluence (10-1000 keV) in this time interval is (1.2 +0.3/-0.3)E-06 erg/cm^2. 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. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM/GRM point of contact for this burst is: Chen-Wei Wang (IHEP) (cwwang@ihep.ac.cn)

GCN 40219 table
GRB_name	GRB250416C
GCN_number	40219
Detection_method	Optical
redshift	0.9630
Circular_text	TITLE: GCN CIRCULAR NUMBER: 40219 SUBJECT: EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963 DATE: 25/04/23 18:19:28 GMT FROM: Jonathan Quirola at Radboud University Andrew J. Levan (Radboud), Jonathan Quirola-Vásquez (Radboud), Peter G. Jonker (Radboud), Franz E. Bauer (UTA), Antonio Martin-Carrillo (UCD), Daniele B. Malesani (DAWN/ NBI and Radboud), Javi Sánchez-Sierras (Radboud), Maria E. Ravasio (Radboud), Agnes van Hoof (Radboud), Jennifer Chacon (PUC), Joyce van Dalen (Radboud), Gregory Corcoran (UCD) report on behalf of a larger collaboration: We observed the optical and X-ray counterpart (Levan et al., GCN 40160; Sbarrato et al., GCN 40166) of the Einstein Probe (EP) transient EP250416a (Zhao et al., GCN 40154, 40165), also identified as GRB 250416C (Svinkin et al., GCN 40167; Wang et al., GCN 40184). Observations were carried out using the Gemini South telescope located on Cerro Pachon, Chile, equipped with the GMOS-S instrument in spectroscopy mode. Observations started on 2025-04-17 at 07:44:43 (i.e., ~0.58 days after the EP detection), and consisted of 4 exposures of 900 s each using the B480 grating, covering the wavelength range between ~4000 and 9500 AA. In our spectrum, we clearly detect an emission line at 7317 AA. Considering the most likely options for this feature (Halpha, Hbeta, [O III], [O II]), the interpretation more consistent with the data is the (unresolved) [O II] 3727/3729 doublet at z = 0.963. In all other cases, we would expect to see other features which would fall over well-covered regions of the spectrum, which are not observed. We thus suggest that this is the redshift of the host galaxy of EP250416a. The spectrum shows tentative absorption features at the expected locations of Mg II (2796, 2803 AA) and Mg I (2852 AA) at z = 0.962, although the signal to noise in the blue region of the spectrum is badly affected by the bright Moon, hence we cannot conclusively determine an absorption redshift. We acknowledge excellent support from the Gemini South staff.