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 keV) ...slat-collimator-based X-ray astronomy satellite with the capability of all-sky monitoring in 0.2-3 MeV. 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.
Abstract
The power-law emission and reflection component provide valuable insights into the accretion process around a black hole. In this work, thanks to the broadband spectra coverage of the ...Nuclear Spectroscopic Telescope Array, we study the spectral properties for a sample of low-mass black hole X-ray binaries (BHXRBs). We find that there is a positive correlation between the photon index Γ and the reflection fraction
R
(the ratio of the coronal intensity that illuminates the disk to the coronal intensity that reaches the observer), consistent with previous studies, but except for MAXI J1820+070. It is quite interesting that this source also deviates from the well-known “V”-shaped correlation between the photon index Γ and the X-ray luminosity
log
L
X
, when it is in the bright hard state. More specifically, the Λ-shaped correlation between Γ and log
L
X
is observed, as the luminosity decreases by a factor of 3 in a narrow range from ∼10
38
to 10
37.5
erg s
−1
. Furthermore, we discover a strong positive correlation between
R
and the X-ray luminosity for BHXRBs in the hard state, which puts a constraint on the disk-corona coupling and the evolution.
Abstract Using data from the Neutron star Interior Composition ExploreR observatory, we identified a permanent spin frequency decrease of Δ ν = −(1.04 ± 0.07) × 10 −7 Hz around MJD 60132 in the ...rotation-powered pulsar PSR B0540-69, which exhibits a periodic signal at a frequency of ν ∼ 19.6 Hz. This points to an antiglitch event, a sudden decrease of the pulsar’s rotational frequency without any major alteration in the pulse profile or any significant increase of the pulsed flux. Additionally, no burst activity was observed in association with the antiglitch. To date, observations of the few known antiglitches have been made in magnetars or accreting pulsars. This is the first antiglitch detected in a rotation-powered pulsar. Given its radiatively quiet nature, this antiglitch is possibly of internal origin. Therefore, we tentatively frame this event within a proposed mechanism for antiglitches where the partial “evaporation” of the superfluid component leads to an increase in the normal component’s moment of inertia and a decrease in the superfluid one.
We present the calibration of the Insight-Hard X-ray Modulation Telescope (Insight-HXMT) X-ray satellite, which can be used to perform timing and spectral studies of bright X-ray sources. ...Insight-HXMT carries three main payloads onboard: the High Energy X-ray telescope (HE), the Medium Energy X-ray telescope (ME) and the low Energy X-ray telescope (LE). In orbit, the radioactive sources, activated lines, the fluorescence lines and celestial sources are used to calibrate the energy scale and energy resolution of the payloads. The Crab nebular is adopted as the primary effective area calibrator and empirical functions are constructed to modify the simulated effective areas of the three payloads respectively. The systematic errors of HE, compared to the model of the Crab nebular, are less than 2% in 28–120 keV and 2%–10% above 120 keV. The systematic errors of ME are less than 1.5% in 10–35 keV. The systematic errors of LE are less than 1% in 1–7 keV except the Si K–edge (1.839 keV, up to 1.5%) and less than 2% in 7–10 keV.
The recently discovered neutron star transient Swift J0243.6+6124 has been monitored by the Hard X-ray Modulation Telescope. Based on the obtained data, we investigate the broadband spectrum of the ...source throughout the outburst. We estimate the broadband flux of the source and search for possible cyclotron line in the broadband spectrum. However, no evidence of line-like features is found up to 150 keV. In the absence of any cyclotron line in its energy spectrum, we estimate the magnetic field of the source based on the observed spin evolution of the neutron star by applying two accretion torque models. In both cases, we get consistent results with B ∼ 1013 G, D ∼ 6 kpc and peak luminosity of >1039 erg s−1, which makes the source the first Galactic ultraluminous X-ray source hosting a neutron star.
Insight-HXMT
, the first X-ray astronomical satellite in China, aims to reveal new sources in the Galaxy and to study fundamental physics of X-ray binaries from 1 to 250 keV. It has three collimated ...telescopes, the High Energy X-ray telescope (HE), the Medium Energy X-ray telescope (ME), and the Low Energy X-ray telescope (LE). Before the launch, in-orbit backgrounds of these three telescopes had been estimated through Geant4 simulation, in order to investigate the instrument performance and the achievement of scientific goals. In this work, these simulated backgrounds are compared with in-orbit observations. Good agreements are shown for all three telescopes. For HE, (1) the deviation of the simulated background rate after two years of operation in space is
∼
5
%
from the observation; (2) the total background spectrum and the relative abundance of the ∼67 keV line show long-term increases both in simulations and observations. For ME, (1) the deviation of simulated background rate is within
∼
15
%
from the observation, and (2) there are no obvious long-term increase features in the background spectra of simulations and observations. For LE, the background level given by simulations is also consistent with observations. The consistencies of these comparisons validate that the
Insight-HXMT
mass model, i.e., space environment components and models adopted, physics processes selected, and detector constructions built, is reasonable. However, the line features at ∼7.5 and 8.0 keV, which are obvious in the observed spectra of LE, are not evident in simulations. This might result from uncertainties in the LE constructions.
Abstract
MAXI J1820+070 is a newly discovered black hole X-ray binary, whose dynamical parameters, namely the black hole mass, the inclination angle, and the source distance, have recently been ...estimated. Insight-HXMT have observed its entire outburst from 2018 March 14. In this work, we attempted to estimate the spin parameter
a
*
, using the continuum-fitting method and applying a fully relativistic thin disk model to the soft-state spectra obtained by Insight-HXMT. It is well known that
a
*
is strongly dependent on three dynamical parameters in this method, and we have examined two sets of parameters. Adopting our preferred parameters:
M
=
8.48
−
0.72
+
0.79
M
⊙
,
i
= 63° ± 3°, and
D
= 2.96 ± 0.33 kpc, we found a slowly spinning black hole of
a
*
= 0.14 ± 0.09 (1
σ
), which gives a prograde spin parameter as the majority of other systems show. It is also possible for the black hole to have a retrograde spin (less than 0) if different dynamical parameters are taken.
ABSTRACT
We report results on the joint-fit of the NuSTAR and HXMT data for the black hole X-ray binary candidate MAXI J1535-571. The observations were obtained in 2017 when the source evolved ...through the hard, hard-intermediate, and soft-intermediate states over the rising phase of the outburst. After subtracting continuum components, X-ray reflection signatures are clearly showed in those observations. By modelling the relativistic reflection in detail, we find that the inner radius Rin is relatively stable with Rin ≲ 1.55Rg during the three states, which implies that the inner radius likely extends to the innermost stable circular orbit even in the bright hard state. When adopting Rin = RISCO, the spin parameter is constrained to be $0.985_{-0.004}^{+0.002}$ at 90 per cent confidence (statistical only). The best-fitting results reveal that the inclination of the inner accretion disc is ∼70–74 deg, which notably conflicts with the apparent orientation of the ballistic jet (≤45 deg). In addition, both the photon index and the electron temperature increase during the transition from hard to soft state. It seems that the corona evolves from dense low-temperature in the low/hard state to tenuous high-temperature after the state transition, which indicates that the state transition is accompanied by the evolution of the coronal properties.
We propose a new method for retrieving the atmospheric number density profile in the lower thermosphere, based on the X-ray Earth occultation of the Crab Nebula with the Hard X-ray Modulation ...Telescope (Insight-HXMT) Satellite. The absorption and scattering of X-rays by the atmosphere result in changes in the X-ray energy, and the Earth’s neutral atmospheric number density can be directly retrieved by fitting the observed spectrum and spectrum model at different altitude ranges during the occultation process. The pointing observations from LE/Insight-HXMT on 16 November 2017 are analyzed to obtain high-level data products such as lightcurve, energy spectrum and detector response matrix. The results show that the retrieved results based on the spectrum fitting in the altitude range of 90–200 km are significantly lower than the atmospheric density obtained by the NRLMSISE-00 model, especially in the altitude range of 110–120 km, where the retrieved results are 34.4% lower than the model values. The atmospheric density retrieved by the new method is qualitatively consistent with previous independent X-ray occultation results (Determan et al., 2007; Katsuda et al., 2021), which are also lower than empirical model predictions. In addition, the accuracy of atmospheric density retrieved results decreases with the increase of altitude in the altitude range of 150–200 km, and the accurate quantitative description will be further analyzed after analyzing a large number of X-ray occultation data in the future.
ABSTRACT Dead time is a common instrumental effect of X-ray detectors, which would alter the behaviour of timing properties of astronomical signals, such as distorting the shape of power density ...spectra (PDS), affecting the root-mean-square of potential quasi-periodic oscillation signals, etc. We revisit the effects of the dead time of Medium Energy X-ray telescope (ME) onboard Insight-HXMT based on the simulation of electronic read-out mechanism that causes the dead time and the real data. We investigate dead time effects on the pulse profile as well as the quasi–periodic oscillation (QPO) signals. The dead time coefficient suggests a linear correlation with the observed count rate in each phase bin of the pulse profile according to the simulation of periodic signal as well as the real data observed on Swift J0243.6+6124. The Fourier-amplitude-difference (FAD) method could well recover the intrinsic shape of the observed PDS in the case that the PDS is from two identical detectors. We apply this technique on ME, by splitting the nine FPGA modules into two groups. The results indicate that the FAD technique suits the case when two groups of detectors are not largely different; and the recovered PDS of Sco X-1 observed by ME slightly enhances the significance of the previously known QPO signal, meanwhile the root-mean-square of QPO is significantly improved. We provide the FAD correction tool implemented in HXMTDAS for users in the future to better analyse QPO signals.
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