In-orbit performance of ME onboard Insight-HXMT in the first 5 years

Introduction The medium-energy X-ray telescope(ME)is a collimated X-ray telescope onboard the Insight hard X-ray modulation telescope(Insight-HXMT)satellite.It has 1728 Si-PIN pixels readout using 54 low noise application-specific integrated circuits(ASICs).ME covers the energy range of 5–30 keV and has a total detection area of 952cm2.The typical energy resolution of ME at the beginning of the mission is 3 keV at 17.8 keV(full width at half maximum,FWHM),and the time resolution is 255μs.In this study,we present the in-orbit performance of ME in its first 5 years of operation.Methods The performance of ME was monitored using onboard radioactive sources and astronomical X-ray objects.ME carries six 241Am radioactive sources for onboard calibration,which can continuously illuminate the calibration pixels.The long-term performance evolution of ME can be quantified using the properties of the accumulated spectra of the calibration pixels.In addition,observations of the Crab Nebula and the pulsar were used to check the long-term evolution of the detection efficiency as a function of energy.Conclusion After 5 years of operation,742cm2 of the Si-PIN pixelswere stillworking normally.The peak positions of 241Am emission lines gradually shifted to the high-energy region,implying a slow increase in ME gain of 1.43%.A comparison of the ME spectra of the Crab Nebula and the pulsar shows that the E–C relations and the redistribution matrix file are still acceptable for most data analysis works,and there is no detectable variation in the detection efficiency.

Insight-HXMT observations of the first binary neutron star merger GW170817

Finding the electromagnetic(EM) counterpart of binary compact star merger, especially the binary neutron star(BNS) merger,is critically important for gravitational wave(GW) astronomy, cosmology and fundamental physics. On Aug. 17, 2017,Advanced LIGO and Fermi/GBM independently triggered the first BNS merger, GW170817, and its high energy EM counterpart,GRB 170817 A, respectively, resulting in a global observation campaign covering gamma-ray, X-ray, UV, optical, IR, radio as well as neutrinos. The High Energy X-ray telescope(HE) onboard Insight-HXMT(Hard X-ray Modulation Telescope) is the unique high-energy gamma-ray telescope that monitored the entire GW localization area and especially the optical counterpart(SSS17 a/AT2017 gfo) with very large collection area(~1000 cm^2) and microsecond time resolution in 0.2-5 MeV. In addition,Insight-HXMT quickly implemented a Target of Opportunity(ToO) observation to scan the GW localization area for potential X-ray emission from the GW source. Although Insight-HXMT did not detect any significant high energy(0.2-5 MeV) radiation from GW170817, its observation helped to confirm the unexpected weak and soft nature of GRB 170817 A. Meanwhile,Insight-HXMT/HE provides one of the most stringent constraints(~10^(-7) to 10^(-6) erg/cm^2/s) for both GRB170817 A and any other possible precursor or extended emissions in 0.2-5 MeV, which help us to better understand the properties of EM radiation from this BNS merger. Therefore the observation of Insight-HXMT constitutes an important chapter in the full context of multi-wavelength and multi-messenger observation of this historical GW event.

Overview to the Hard X-ray Modulation Telescope (Insight-HXMT) Satellite

As China’s first X-ray astronomical satellite, the Hard X-ray Modulation Telescope (HXMT), which was dubbed as Insight-HXMT after the launch on June 15, 2017, is a wide-band(1-250 ke V) slat-collimator-based X-ray astronomy satellite with the capability of all-sky monitoring in 0.2-3 Me V. It was designed to perform pointing, scanning and gamma-ray burst(GRB)observations and, based on the Direct Demodulation Method (DDM), the image of the scanned sky region can be reconstructed.Here we give an overview of the mission and its progresses, including payload, core sciences, ground calibration/facility, ground segment, data archive, software, in-orbit performance, calibration, background model, observations and some preliminary results.

The enhanced X-ray Timing and Polarimetry mission—eXTP

In this paper we present the enhanced X-ray Timing and Polarimetry mission—eXTP. eXTP is a space science mission designed to study fundamental physics under extreme conditions of density, gravity and magnetism. The mission aims at determining the equation of state of matter at supra-nuclear density, measuring effects of QED, and understanding the dynamics of matter in strong-field gravity. In addition to investigating fundamental physics, eXTP will be a very powerful observatory for astrophysics that will provide observations of unprecedented quality on a variety of galactic and extragalactic objects. In particular, its wide field monitoring capabilities will be highly instrumental to detect the electro-magnetic counterparts of gravitational wave sources.The paper provides a detailed description of:(1) the technological and technical aspects, and the expected performance of the instruments of the scientific payload;(2) the elements and functions of the mission, from the spacecraft to the ground segment.

The Medium Energy X-ray telescope (ME) onboard the Insight-HXMT astronomy satellite

The Medium Energy X-ray telescope(ME) is one of the three main telescopes on board the Insight hard X-ray modulation telescope(Insight-HXMT) astronomy satellite. ME contains 1728 pixels of Si-PIN detectors sensitive in 5-30 ke V with a total geometrical area of 952 cm^2. The application specific integrated circuit(ASIC) chip, VA32TA6, is used to achieve low power consumption and low readout noise. The collimators define three kinds of field of views(FOVs) for the telescope, 1°×4°, 4°×4°,and blocked ones. Combination of such FOVs can be used to estimate the in-orbit X-ray and particle background components.The energy resolution of ME is ~3 ke V at 17.8 ke V(FWHM) and the time resolution is 255 μs. In this paper, we introduce the design and performance of ME.