GCN Circular 27718

S.-N. Zhang, X.-B. Li, C.-K. Li, M.-Y. Ge, S.-L. Xiong,
S.-M. Jia, J.-Y. Nie, H.-S. Zhao, C.-Z. Liu, Y. Chen, X.-L. Cao,
Y.-P. Xu, F.-J. Lu, L.-M. Song (IHEP), T.-P. Li (THU/IHEP),
on behalf of the Insight-HXMT team:

Since 2020-04-28 07:14:51 UTC, Insight/HXMT has been observing
SGR J1935+2154 under a public ToO. The current plan is to
continue this public ToO until the end of May. An extended observation
after May is probable if this SGR is still in active phase.

Joint observations with Insight-HXMT are highly encouraged.
The observation plan of Insight-HXMT can be found at:
http://enghxmt.ihep.ac.cn/dqjh.jhtml

Insight/HXMT data of this public ToO will be released very soon
(i.e. a few days after observation), following to the data policy of
Insight-HXMT. The data can be accessed at: http://hsuc.ihep.ac.cn/web

We caution that significant data saturation may exist and is not corrected
in the standard Insight-HXMT data products, since Insight-HXMT was not
designed to handle very high counting rates. We are developing specific
methods and codes to handle such data saturation, which have been applied
successfully to the burst of SGR J1935+2154 associated with FRB 200428
(Atel #13687). However, these codes are not yet mature enough for public
release. We thus suggest users of these data products be aware of these
effects. For assistance on accessing and analyzing the Insight-HXMT data,
please contact Dr. X.-B. Li at lixb@ihep.ac.cn

As of May 10, 2020, about 100 bursts from SGR J1935+2154 have been
found in a preliminary search of the raw data of HE, ME and LE.
The online catalogue of SGR J1935+2154 bursts detected by Insight-HXMT
could be found at: http://enghxmt.ihep.ac.cn/bfy/331.jhtml

The sensitivities (3-sigma) of Insight-HXMT to short bursts are:
HE (20 - 250 keV):�� Fluence = 4.5E-9 * sqrt(T)�� erg/cm2,
ME ( 5 - 30�� keV):�� Fluence = 3.5E-9 * sqrt(T)�� erg/cm2,
LE ( 1 - 10�� keV):�� Fluence = 2.7E-9 * sqrt(T)�� erg/cm2,
where T is the burst duration in second.