Insight-HXMT detection of a QPO in 1-150 keV in MAXI J1803-298
ATel #14613; Author list: Yanan Wang (Uni. of Southampton); Yingchen Xu (IHEP); Long Ji (SYSU); Liang Zhang (Uni. of Southampton); Liming Song (IHEP); Jinlu Qu; Shuang-Nan Zhang; Fangjun Lu; Yupeng Chen on behalf of the HXMT team
on 8 May 2021; 06:26 UT
Credential Certification: Yu-Peng Chen (chenyp@ihep.ac.cn)
Subjects: X-ray, Transient
Following the MAXI/GSC alert of the newly discovered X-ray transient MAXI J1803-298 (ATel #14587), Insight-HXMT performed its observation from May 3 at 17:00 UTC to May 3 at 21:09 UTC with an exposure time of ~3 ks. A strong QPO signal at 0.16+/-0.03 Hz has been detected by all the three instruments on board in the 1-10 keV, 10-20 keV and 25-150 keV, respectively. The amplitude of the QPO rms increased with the three energy bands from 9.0+/-0.4%, 11.8+/-4.5% to 12.7+/-4.9% meanwhile the amplitude of the broadband noise rms below 16 Hz decreased from 21.8+/-4.3%, 21.7+/-6.9% to 16.5+/-4.7%. The 1-10 keV detection of the QPO is consistent with the previous reports by ATel #14602 and #14609.
The broad energy spectra can be reasonably described by a cutoff power-law with a photon index of 1.51+/-0.01 and a high energy cutoff of 68.3+/-3.7 keV. Positive residuals at 6-8 keV suggest the presence of an iron emission line. The 2-150 keV flux is about 8.3E-09 ergs/cm^2/s. The above timing and spectral features support MAXI J1803-298 as being an accreting black hole in the hard state of an outburst. Insight-HXMT will continually monitor MAXI J1803-298 in a nearly full-day basis to trace its evolution in the current state.
Insight-HXMT is China's first X-ray astronomical satellite (http://hxmten.ihep.ac.cn). It consists of three collimated telescopes: the High Energy X-ray Telescope, the Medium Energy X-ray Telescope, and the Low Energy X-ray Telescope, with collecting area/energy-range of ~5100 cm^2/20-250 keV, ~952 cm^2/5-30 keV and ~384 cm^2/1-10 keV, respectively.
