TITLE: GCN CIRCULAR NUMBER: 44995 SUBJECT: GRB 260616A: SVOM/GRM observation DATE: 26/06/19 11:49:27 GMT FROM: guohx@ihep.ac.cn SVOM/GRM team: Hao-Xuan Guo, Chen-Wei Wang, Zheng-Hang Yu, Chao Zheng, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Ulysse Jacob (LUPM) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by GRB 260616A (SVOM burst-id sb26061602) at 2026-06-16T03:21:30.000 UTC (T0), which is also detected by Fermi/GBM (Fermi/GBM team, GCN #44948, Matt Godwin et al., GCN #44971), Fermi/LAT (S. Lopez et al., GCN #44960), GECAM-B (Hao-Xuan Guo et al., GCN #44964), Konus-Wind (A. Ridnaia et al., GCN #44967), Insight-HXMT (Chen-Wei Wang et al., GCN #44980) and NuSTAR (G. Waratkar et al., GCN #44987). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multiple pulses with a T90 of 143 +5/-4 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260616A.png In addition, the position of this burst, as determined by Fermi/LAT (RA = 93.53, Dec = -32.07, GCN #44960), is located at about 97 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-62 to T0+130 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.38 +0.05/-0.04 and the cutoff energy, parameterized as Epeak, is 573 +61/-52 keV. The event fluence (10-1000 keV) in this time interval is (2.14 +/-0.03)E-04 erg/cm^2. The 1s peak spectrum, measured from T0+75 to T0+76 s, if fitted by a power law function with an exponential high-energy cutoff, the power law index is -1.45 +0.11/-0.07 and the cutoff energy, parameterized as Epeak, is (2.00 +1.47/-0.85)E+03 keV. The flux (10-1000 keV) in this time interval is (4.48 +0.15/-0.14)E-06 erg/cm^2/s. The localization of GRB 260616A in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260616A_amati.png The localization of GRB 260616A in the 'Yonetoku' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260616A_yonetoku.png 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 point of contact for this burst is: Hao-Xuan Guo (IHEP)(guohx@ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/44995. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...