GCN Circular 24369

LIGO/Virgo S190425z: Insight-HXMT observation and counterpart search

J. Guan, Y. Nang, N. Sai, C, Wang, C. K. Li, J. Y. Liao, Y. Huang, Y. J. Yang, Z. W. Li, X. B. Li, G. Li, S. L. Xiong, L. Tao, C. Z.
+Liu, X. L. Cao, Y. Chen, A. M. Zhang, Y. J. Jin, Z. Zhang (THU), T. P. Li (IHEP/THU), F. J. Lu, L. M. Song, M. Wu, Y. P. Xu, S. N.
+Zhang (IHEP), report on behalf of the Insight-HXMT team:

We performed small area scan survey of the LIGO localization region with Insight-HXMT after the LVC trigger S190425z (LVC et al. GCN
+24168). The observation started at 2019-4-25 16:28 UTC, about 8 hours after the trigger time. Four fields were visited, with
+overlaps, mapping 987.2 square degrees of the bayestar map 90% credible region and covering a sky region totalling of 20.4% of the
+LIGO localization likelihood. Each field was scanned twice and the total exposure time was 79.2 ks. No significant new source is
+found in the region in search of the Insight-HXMT raw light curves.


The survey also covered T2019ebq/PS19qp (Smith et al. GCN, 24210), a possible optical counterpart to S190425z, at 2019-04-26 02:12
+UTC (for 400s) and 2019-04-26 15:06 UTC (for 250s). We find no significant new X-ray sources in the data. The 5-sigma flux upper
+limits are obtained when fitting the light curves to the position of T2019ebq/PS19qp: 6.8 mCrab (HE���25-100 keV), 16.2 mCrab
+(ME���7-40 keV) and 5.2 mCrab (LE���1-6 keV). The flux upper limits for other positions in the scanned fields are about the same as
+quoted above.

Further analysis will be reported in the following circulars.

Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA)
+and the Chinese Academy of Sciences (CAS). More information could be found at: http://www.hxmt.org.


List of observed fields:

Start (UTC)        RA and Dec (J2000)   radius(degree)
2019/4/25 16:28    245    20         10
2019/4/25 19:38    252    12         10
2019/4/25 22:49    235    30         10
2019/4/26 02:00    255    0          10
2019/4/26 05:11    245    20         10
2019/4/26 08:22    252    12         10
2019/4/26 11:33    235    30         10
2019/4/26 14:44    255    0          10


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Sincerely Yours,
Zhengwei Li,
Key Laboratory of Particle Astrophysics,
Institute of High Energy Physics,
Chinese Academy of Sciences, Beijing China
TEL:15210983070 E-mail:lizw@ihep.ac.cn