TITLE: GCN CIRCULAR NUMBER: 39510 SUBJECT: LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations DATE: 25/02/27 08:37:53 GMT FROM: Yue Wang m18509381757@163.com
Yue Wang, Chen-Wei Wang, Shao-Lin Xiong, Shi-Jie Zheng, Ping Wang (IHEP) and Ce Cai (HEBNU) report on behalf of the SVOM team:
At the event time 2025-02-06T21:25:30.439 (UTC) of S250206dm (GCN 39175; GCN 39178; GCN 39231), SVOM/GRM was observing normally and monitored 96.6% of the localization probability region of this GW event.
There was no SVOM/GRM in-flight trigger around the event time of S250206dm. The routine blind search of SVOM/GRM data also found no burst candidate.
Considering three typical GRB spectral models (i.e. soft, normal and hard Band functions), three timescales and the center region of GW localization (RA= 38.21°, Dec = 53.47°), the 3 sigma upper limits of the GRB energy flux (15 keV-5000 keV, in units of 10^-7 erg/s/cm^2) are reported below:
|Timescale (s) | Soft | Normal | Hard| | ------------ | ------------ | ------------ | ------------ | |0.1| 0.63 | 1.36 | 17.09 | |1| 0.20 | 0.43 | 5.40 | |10| 0.06 | 0.14 | 1.71 |
With the median luminosity distance of 373 Mpc from the GW detection (GCN 39231), we further calculate the following upper limits of the GRB intrinsic luminosity (1 keV-10 MeV, in units of 10^49 erg/s):
|Timescale (s) | Soft | Normal | Hard| | ------------ | ------------ | ------------ | ------------ | |0.1| 0.17 |0.25|4.35| |1| 0.05 |0.08|1.38| |10| 0.01 |0.03|0.44|
We note that all these results are preliminary and refined analysis will be reported.
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: Yue Wang (IHEP) (yuewang@ihep.ac.cn)
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