It is urgent to develop catalysts with application potential for oxidative coupling of methane(OCM)at relatively lower temperature.Herein,three-dimensional ordered macro porous(3 DOM)La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)(...It is urgent to develop catalysts with application potential for oxidative coupling of methane(OCM)at relatively lower temperature.Herein,three-dimensional ordered macro porous(3 DOM)La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)(A_(2)B_(2)O_(7)-type)catalysts with disordered defective cubic fluorite phased structure were successfully prepared by a colloidal crystal template method.3DOM structure promotes the accessibility of the gaseous reactants(O2and CH4)to the active sites.The co-doping of Ca and Sr ions in La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts improved the formation of oxygen vacancies,thereby leading to increased density of surface-active oxygen species(O_(2)^(-))for the activation of CH4and the formation of C2products(C2H6and C2H4).3DOM La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts exhibit high catalytic activity for OCM at low temperature.3DOM La1.7Sr0.3Ce1.7Ca0.3O7-δcatalyst with the highest density of O_(2)^(-)species exhibited the highest catalytic activity for low-temperature OCM,i.e.,its CH4conversion,selectivity and yield of C2products at 650℃are 32.2%,66.1%and 21.3%,respectively.The mechanism was proposed that the increase in surface oxygen vacancies induced by the co-doping of Ca and Sr ions boosts the key step of C-H bond breaking and C-C bond coupling in catalyzing low-temperature OCM.It is meaningful for the development of the low-temperature and high-efficient catalysts for OCM reaction in practical application.展开更多
The Follow-up X-ray Telescope(FXT)is one of the main scientific instruments on board the Einstein Probe astronomical satellite,which was launched in 2024 January.FXT consists of two Wolter I type nested telescopes(FXT...The Follow-up X-ray Telescope(FXT)is one of the main scientific instruments on board the Einstein Probe astronomical satellite,which was launched in 2024 January.FXT consists of two Wolter I type nested telescopes(FXT-A and FXT-B)with a focal length of 1600 mm.The focal plane detector employs a PNCCD with 384×384 pixels.The timing mode of FXT serves as the primary operating mode for fast X-ray timing observations.To evaluate and validate the timing performance of FXT prior to launch,a comprehensive timing calibration was performed at the 100 m X-ray test facility.By simulating various periodic Crab-like profiles using the Grid Controlled X-ray Tube(GCXT)in conjunction with a pulsar simulation module,it was verified that the relative time accuracy of FXT exceeds 5×10^(−9).Furthermore,employing GCXT with a voltage pulse generation module enabled the determination of the time resolutions for FXT-A and FXT-B,recorded as 45.6±2.7μs and 47.1±2.8μs,respectively.An absolute timing calibration for FXT-B was carried out using the GCXT and a time interval analyzer,revealing a measured time delay of 3.9±2.1μs for FXT-B.展开更多
In this paper,we present the current status of the enhanced X-ray Timing and Polarimetry mission,which has been fully approved for launch in 2030.eXTP is a space science mission designed to study fundamental physics u...In this paper,we present the current status of the enhanced X-ray Timing and Polarimetry mission,which has been fully approved for launch in 2030.eXTP is a space science mission designed to study fundamental physics under extreme conditions of matter density,gravity,and magnetism.The mission aims at determining the equation of state of matter at supra-nuclear density,measuring the effects of quantum electro-dynamics,and understanding the dynamics of matter in strong-field gravity.In addition to investigating fundamental physics,the eXTP mission is poised to become a leading observatory for time-domain and multi-messenger astronomy in the 2030s,as well as providing observations of unprecedented quality on a variety of galactic and extragalactic objects.After briefly introducing the history and a summary of the scientific objectives of the eXTP mission,this paper presents a comprehensive overview of:(1)the cutting-edge technology,technical specifications,and anticipated performance of the mission’s scientific instruments;(2)the full mission profile,encompassing spacecraft design,operational capabilities,and ground segment infrastructure.展开更多
Background:The Einstein Probe mission is an astronomical satellite developed in China,focusing on time-domain astronomy in the soft X-ray energy band.A key payload of this mission is the follow-up X-ray telescope(FXT)...Background:The Einstein Probe mission is an astronomical satellite developed in China,focusing on time-domain astronomy in the soft X-ray energy band.A key payload of this mission is the follow-up X-ray telescope(FXT),which is the result of international collaboration between China and Europe.The FXT features gold-coated nickel Wolter-I-type focusing mirrors and utilizes PNCCD detectors for imaging and spectroscopy in the focal plane.Methods:We reviewed the seven-year development history of the FXT.Initially,the configuration of the FXT consisted of a single telescope unit in 2017,but it later evolved into a dual-unit setup.Building on the successful design of eROSITA,the FXT team has innovatively introduced new operational modes for the PNCCD.FXT team also developed an ultra-compact helium pulse tube refrigerator,which cools the PNCCD down to-90℃.Additionally,various passive shielding measures have been implemented to protect against high-energy charged particles and enhance radiation resistance.These advancements have significantly improved the overall performance and reliability of the FXT.Results and conclusion:The ground calibrations and tests of the FXT demonstrate that its primary performance meets the established design goals.The FXT has exhibited outstanding performance in orbit,establishing itself as one of the space X-ray telescopes with considerable international influence.展开更多
Scheduled for launch in 2030,the enhanced X-ray Timing and Polarization(eXTP)telescope is a Chinese space-based mission aimed at studying extreme conditions and phenomena in astrophysics.eXTP will feature three main p...Scheduled for launch in 2030,the enhanced X-ray Timing and Polarization(eXTP)telescope is a Chinese space-based mission aimed at studying extreme conditions and phenomena in astrophysics.eXTP will feature three main payloads:Spectroscopy Focusing Array(SFA),Polarimetry Focusing Array(PFA),and a Wide-field Camera(W2C).This white paper outlines observatory science,incorporating key scientific advances and instrumental changes since the publication of the previous white paper.We will discuss perspectives of eXTP on the research domains of flare stars,supernova remnants,pulsar wind nebulae,cataclysmic variables,X-ray binaries,ultraluminous X-ray sources,active galactic nucleus(AGN),and pulsar-based positioning and timekeeping.展开更多
Purpose The follow-up X-ray telescope(FXT)is one of the two payloads of the Einstein Probe(EP),consisting of the upper composite with the X-ray mirror module as the core,the lower composite with the pnCCD module as th...Purpose The follow-up X-ray telescope(FXT)is one of the two payloads of the Einstein Probe(EP),consisting of the upper composite with the X-ray mirror module as the core,the lower composite with the pnCCD module as the core,and the interface structure.The FXT thermal control subsystem is responsible for the thermal design,thermal implementations,and testing of the entire FXT payload thermal control.Methods A design approach is adopted with passive thermal control technology as the main method and active thermal control technology as a supplement for common components.The X-ray mirror modules are high-precision optical components,utilizing active closed-loop temperature control to ensure high precision and stability.The pnCCD detectors operate at a stable low temperature,with refrigerators used to cool the detector houses,ensuring they can operate under stable low-temperature conditions.The hot ends of the refrigerators are connected to the external radiator panels through heat pipes for heat dissipation.Results The thermal control subsystem of FXT is operating properly in-orbit.All component temperatures meet the design requirements.Conclusion After multiple rounds of design and test verification,FXT was successfully launched with EP and completed in-orbit testing.During the in-orbit testing phase of EP,the function of the FXT thermal control subsystem works well.The temperatures of the components and units are normal.This paper introduces the design of FXT thermal control and the in-orbit performance of the thermal control subsystem.展开更多
Purpose The Einstein Probe(EP)satellite is a space X-ray satellite for time-domain astronomy and high-energy astrophysics.The precision control of the optical structure directly affects the imaging quality and positio...Purpose The Einstein Probe(EP)satellite is a space X-ray satellite for time-domain astronomy and high-energy astrophysics.The precision control of the optical structure directly affects the imaging quality and positioning accuracy of the Follow-up X-ray Telescope(FXT),playing a crucial role in achieving the on-orbit scientific objectives of the FXT.Higher positioning accuracy makes it easier to identify corresponding bodies for the discovery and positioning of transient sources.Accurate positioning is beneficial for follow-up observations in other bands,such as optical spectroscopy.Methods This article mainly introduces the precision control methods and processes of the FXT optical structure,which have been tested and verified through satellite test.The on-orbit source positioning accuracy of the FXT telescope is within 20 arcseconds(90% confidence level),meeting the requirements of the FXT mission.Results and Conclusion To ensure the accuracy of the EP satellite’s FXT optical structure,measures such as component processing control,installation control,and posttest adjustments are taken on the ground to ensure that the detector mounting position,optical axis deviation,and other precision indicators before and after the satellite lever test meet the design requirements.After a successful launch,through on-orbit calibration,the FXT-A and FXT-B optical axis pointing direction deviation is 39 arcseconds,and the source positioning error is better than 3'' at 68% confidence level.FXT optical structure meets all the requirements from design,processing,installation,etc.,successfully meeting scientific needs.展开更多
Purpose:In order to evaluate the mechanical feasibility of the domestic baffle made by wire electrode cutting for the mirror assembly of the Follow-up X-ray Telescope(FXT)onboard the Einstein Probe(EP)mission.Methods:...Purpose:In order to evaluate the mechanical feasibility of the domestic baffle made by wire electrode cutting for the mirror assembly of the Follow-up X-ray Telescope(FXT)onboard the Einstein Probe(EP)mission.Methods:Finite element analysis was performed to compare the structural differences between the domestic baffle made by wire electrode cutting and the eROSITA baffle made by bonding.The finite element models were verified by test data in advance to avoid significant deviations.Finally,the differences in dynamical performances between the FXT mirror assemblies with the two baffles were investigated through modal analysis and frequency response analysis using the pre-verified models.Results and conclusions:The results show that,from the perspective of the entire mirror assembly,their eigenfrequencies remain similar,except for the second lateral eigenfrequency,which shifts forward by approximately 24 Hz in the mirror assembly equipped with the domestic baffle.However,for the X-ray baffles themselves,the axial and lateral eigenfrequencies of the two baffles differ by approximately 49 Hz and 185 Hz,respectively.These eigenfrequencies are staggered,ensuring that over-response is avoided.In terms of response amplification,the domestic baffle,compared to the eROSITA baffle,exhibits inferior axial mechanical characteristics but superior lateral characteristics.In summary,from a mechanical perspective,the domestic baffle is feasible.展开更多
Background The Einstein probe(EP)is an X-ray astronomical satellite dedicated to time-domain astronomy and high-energy astrophysics.Initiated at the end of 2017,it was successfully launched on January 9,2024.The follo...Background The Einstein probe(EP)is an X-ray astronomical satellite dedicated to time-domain astronomy and high-energy astrophysics.Initiated at the end of 2017,it was successfully launched on January 9,2024.The follow-up X-ray telescope(FXT)is a key payload on the EP satellite.The FXT employs PNCCD as its focal plane detector.Its electronic components include the electronic control box(EC-Box),the detector electronics boxes(DE-Box),the refrigerator controller,the movement mechanisms controller,and the temperature control instrument.Methods The FXT conducted functional performance tests in-orbit as planned,including three operating modes of the detector,energy detection range,and energy resolution.Results Since FXT became operational in orbit,all electronic equipment has been working stably.The FXT has an energy detection range of 0.3-10 keV,with an energy resolution of approximately 92 eV@1.25 keV,and an electronic noise of about 3.3e^(-).展开更多
Purpose:Mini-magnets of FXT are designed to deflect low-energy electrons that are incident into the camera aperture area,preventing them from reaching the focal plane detector and thereby reducing the noises they gene...Purpose:Mini-magnets of FXT are designed to deflect low-energy electrons that are incident into the camera aperture area,preventing them from reaching the focal plane detector and thereby reducing the noises they generate.Methods:By employing a combination of theoretical calculations and experimental measurements,the parameters of the FXT mini-magnets were obtained,including magnetic field distributions,magnetic moment results,and electron deflection efficiency.Results:The structural and magnetic models of the optimized mini-magnets are presented.Distributions of magnetic field intensity on different planes within the camera aperture are compared with the measured results from the FXT flight models(FMs).The results for the total and separated magnetic moment of two sets of FMs are also provided.Additionally,the deflection efficiency for 25 keV electrons is calculated under various incident conditions.Conclusion:The FMs of mini-magnets show good performance,with the measured values of magnetic field distributions being highly consistent with the theoretical values.A perfect result for total magnetic moment of less than 10mA·m^(2)has been achieved,far better than requirement of 100mA·m^(2).The calculated electron deflection efficiency reached over 99.88%,effectively fulfilling the objective of deflecting electrons in space.展开更多
We report the discovery of a peculiar X-ray transient,EP240408a,by Einstein Probe(EP)and follow-up studies made with EP,Swift,NICER,GROND,ATCA and other ground-based multiwavelength telescopes.The new transient was fi...We report the discovery of a peculiar X-ray transient,EP240408a,by Einstein Probe(EP)and follow-up studies made with EP,Swift,NICER,GROND,ATCA and other ground-based multiwavelength telescopes.The new transient was first detected with Wide-field X-ray Telescope(WXT)on board EP on April 8th,2024,manifested in an intense yet brief X-ray flare lasting for 12 s.The flare reached a peak flux of 3:9×10^(−9) erg cm^(−2) s^(−1) in 0.5-4 keV,∼300 times brighter than the underlying X-ray emission detected throughout the observation.Rapid and more precise follow-up observations by EP/FXT,Swift and NICER confirmed the finding of this new transient.Its X-ray spectrum is non-thermal in 0.5-10 keV,with a power-law photon index varying within 1.8-2.5.The X-ray light curve shows a plateau lasting for∼4 d,followed by a steep decay till becoming undetectable∼10 d after the initial detection.Based on its temporal property and constraints from previous EP observations,an unusual timescale in the range of 7-23 d is found for EP240408a,which is intermediate between the commonly found fast and long-term transients.No counterparts have been found in optical and near-infrared,with the earliest observation at 17 h after the initial X-ray detection,suggestive of intrinsically weak emission in these bands.We demonstrate that the remarkable properties of EP240408a are inconsistent with any of the transient types known so far,by comparison with,in particular,jetted tidal disruption events,gamma-ray bursts,X-ray binaries and fast blue optical transients.The nature of EP240408a thus remains an enigma.We suggest that EP240408a may represent a new type of transients with intermediate timescales of the order of∼10 d.The detection and follow-ups of more of such objects are essential for revealing their origin.展开更多
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 m...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.展开更多
The in-flight instrumental background of the Follow-up X-ray Telescope(FXT)onboard Einstein Probe mis sion is analysed in this work by utilizing observations collected during the performance verification phase and sub...The in-flight instrumental background of the Follow-up X-ray Telescope(FXT)onboard Einstein Probe mis sion is analysed in this work by utilizing observations collected during the performance verification phase and subsequent dedicated filter wheel closed observations.The instrumental backgrounds of the two FXT modules are consistent with each other,with an average rate of~4×10^(-2)counts s^(-1)keV^(-1)in the 0.5-10 keV band for each module.The background is nearly uniformly distributed across the detector area,with a minor increase(<8%)observed along rows.The spatial distribution shows significant modulation by the geomagnetic field.The spectral shapes remain unchanged in 0.5-10 keV at different rates.The long-term temporal variation indicates a periodic change associated with the orbital precession(~57 days).The innovative design of FXT full-frame readout mode enables simultaneous recording of events in both the imaging area(IMG)and the frame store area(FSA)of the pnCCD.FSA event rates show a strong linear correlation with the IMG,based on which the IMG instrumental background modeling is established.展开更多
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 as...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.展开更多
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 fundament...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 170817A, 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 （SSS17a/AT2017gfo） with very large collection area （M000 cm2） 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 170817A. Meanwhile, Insight-HXMT/HE provides one of the most stringent constraints （-10-7 to 104 erg/cm2/s） for both GRB170817A 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.展开更多
The Low Energy X-ray telescope(LE) is one of the three main instruments of the Insight-Hard X-ray Modulation Telescope(Insight-HXMT). It is equipped with Swept Charge Device(SCD) sensor arrays with a total geometrical...The Low Energy X-ray telescope(LE) is one of the three main instruments of the Insight-Hard X-ray Modulation Telescope(Insight-HXMT). It is equipped with Swept Charge Device(SCD) sensor arrays with a total geometrical area of 384 cm^2 and an energy band from 0.7 to 13 ke V. In order to evaluate the particle induced X-ray background and the cosmic X-ray background simultaneously, LE adopts collimators to define four types of Field Of Views(FOVs), i.e., 1.6°×6°, 4°×6°, 50°-60°×2°-6 oand the blocked ones which block the X-ray by an aluminum cover. LE is constituted of three detector boxes(LEDs) and an electric control box(LEB) and achieves a good energy resolution of 140 e V@5.9 ke V, an excellent time resolution of 0.98 ms, as well as an extremely low pileup(<1%@18000 cts/s). Detailed performance tests and calibration on the ground have been performed,including energy-channel relation, energy response, detection efficiency and time response.展开更多
Purpose The low-energy X-ray telescope(LE)is a main instrument of the Insight-HXMT mission and consists of 96 swept charge devices covering the 1–10 keV energy band.The energy gain and resolution are continuously cal...Purpose The low-energy X-ray telescope(LE)is a main instrument of the Insight-HXMT mission and consists of 96 swept charge devices covering the 1–10 keV energy band.The energy gain and resolution are continuously calibrated by analyzing Cassiopeia A(Cas A)and blank sky data,while the effective areas are also calibrated with the observations of the Crab Nebula.In this paper,we present the evolution of the in-orbit performances of LE in the first 5 years since launch.Methods The Insight-HXMT data analysis software package(HXMTDAS)is utilized to extract the spectra of Cas A,blank sky,and Crab Nebula using different good time interval selections.We fit a model with a power-law continuum and several Gaussian lines to different ranges of Cas A and blank sky spectra to get peak energies of their lines through xspec.After updating the energy gain calibration in CALibration DataBase(CALDB),we rerun the Cas A data to obtain the energy resolution.An empirical function is used to modify the simulated effective areas so that the background-subtracted spectrum of the Crab Nebula can best match the standard model of the Crab Nebula.Results The energy gain,resolution,and effective areas are calibrated every month.The corresponding calibration results are duly updated in CALDB,which can be downloaded and used for the analysis of Insight-HXMT data.Simultaneous observations with NuSTAR and NICER can also be used to verify our derived results.Conclusion LE is a well-calibrated X-ray telescope working in 1–10 keV band.The uncertainty of LE gain is less than 20eV in 2–9 keV band,and the uncertainty of LE resolution is less than 15eV.The systematic errors of LE,compared to the model of the Crab Nebula,are lower than 1.5%in 1–10 keV.展开更多
基金supported by the National Key Research and Development Program of China(Nos.2022YFB3504100,2022YFB3506200)the National Natural Science Foundation of China(Nos.22208373,22376217)+1 种基金the Beijing Nova Program(No.20220484215)the Science Foundation of China University of Petroleum,Beijing(No.2462023YJRC030)。
文摘It is urgent to develop catalysts with application potential for oxidative coupling of methane(OCM)at relatively lower temperature.Herein,three-dimensional ordered macro porous(3 DOM)La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)(A_(2)B_(2)O_(7)-type)catalysts with disordered defective cubic fluorite phased structure were successfully prepared by a colloidal crystal template method.3DOM structure promotes the accessibility of the gaseous reactants(O2and CH4)to the active sites.The co-doping of Ca and Sr ions in La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts improved the formation of oxygen vacancies,thereby leading to increased density of surface-active oxygen species(O_(2)^(-))for the activation of CH4and the formation of C2products(C2H6and C2H4).3DOM La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts exhibit high catalytic activity for OCM at low temperature.3DOM La1.7Sr0.3Ce1.7Ca0.3O7-δcatalyst with the highest density of O_(2)^(-)species exhibited the highest catalytic activity for low-temperature OCM,i.e.,its CH4conversion,selectivity and yield of C2products at 650℃are 32.2%,66.1%and 21.3%,respectively.The mechanism was proposed that the increase in surface oxygen vacancies induced by the co-doping of Ca and Sr ions boosts the key step of C-H bond breaking and C-C bond coupling in catalyzing low-temperature OCM.It is meaningful for the development of the low-temperature and high-efficient catalysts for OCM reaction in practical application.
基金supported by the Strategic Priority Research Program on Space Science,the Chinese Academy of Sciences,grant No.XDA15310103.
文摘The Follow-up X-ray Telescope(FXT)is one of the main scientific instruments on board the Einstein Probe astronomical satellite,which was launched in 2024 January.FXT consists of two Wolter I type nested telescopes(FXT-A and FXT-B)with a focal length of 1600 mm.The focal plane detector employs a PNCCD with 384×384 pixels.The timing mode of FXT serves as the primary operating mode for fast X-ray timing observations.To evaluate and validate the timing performance of FXT prior to launch,a comprehensive timing calibration was performed at the 100 m X-ray test facility.By simulating various periodic Crab-like profiles using the Grid Controlled X-ray Tube(GCXT)in conjunction with a pulsar simulation module,it was verified that the relative time accuracy of FXT exceeds 5×10^(−9).Furthermore,employing GCXT with a voltage pulse generation module enabled the determination of the time resolutions for FXT-A and FXT-B,recorded as 45.6±2.7μs and 47.1±2.8μs,respectively.An absolute timing calibration for FXT-B was carried out using the GCXT and a time interval analyzer,revealing a measured time delay of 3.9±2.1μs for FXT-B.
基金the support of the National Natural Science Foundation of China(Grant No.12333007)the International Partnership Program of Chinese Academy of Sciences(Grant No.113111KYSB20190020)+4 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA15020100)support by ASI,under the dedicated eXTP agreements and agreement ASI-INAF n.2017-14-H.O.by INAF and INFN under project REDSOXsupport from the Deutsche Zentrum für Luft-und Raumfahrt,the German Aerospace Center(DLR)support from MINECO grant ESP2017-82674-R and FEDER funds.
文摘In this paper,we present the current status of the enhanced X-ray Timing and Polarimetry mission,which has been fully approved for launch in 2030.eXTP is a space science mission designed to study fundamental physics under extreme conditions of matter density,gravity,and magnetism.The mission aims at determining the equation of state of matter at supra-nuclear density,measuring the effects of quantum electro-dynamics,and understanding the dynamics of matter in strong-field gravity.In addition to investigating fundamental physics,the eXTP mission is poised to become a leading observatory for time-domain and multi-messenger astronomy in the 2030s,as well as providing observations of unprecedented quality on a variety of galactic and extragalactic objects.After briefly introducing the history and a summary of the scientific objectives of the eXTP mission,this paper presents a comprehensive overview of:(1)the cutting-edge technology,technical specifications,and anticipated performance of the mission’s scientific instruments;(2)the full mission profile,encompassing spacecraft design,operational capabilities,and ground segment infrastructure.
基金supported by the Strategic Priority Research Program on Space Science,the Chinese Academy of Sciences(Grant No.XDA 15310103).
文摘Background:The Einstein Probe mission is an astronomical satellite developed in China,focusing on time-domain astronomy in the soft X-ray energy band.A key payload of this mission is the follow-up X-ray telescope(FXT),which is the result of international collaboration between China and Europe.The FXT features gold-coated nickel Wolter-I-type focusing mirrors and utilizes PNCCD detectors for imaging and spectroscopy in the focal plane.Methods:We reviewed the seven-year development history of the FXT.Initially,the configuration of the FXT consisted of a single telescope unit in 2017,but it later evolved into a dual-unit setup.Building on the successful design of eROSITA,the FXT team has innovatively introduced new operational modes for the PNCCD.FXT team also developed an ultra-compact helium pulse tube refrigerator,which cools the PNCCD down to-90℃.Additionally,various passive shielding measures have been implemented to protect against high-energy charged particles and enhance radiation resistance.These advancements have significantly improved the overall performance and reliability of the FXT.Results and conclusion:The ground calibrations and tests of the FXT demonstrate that its primary performance meets the established design goals.The FXT has exhibited outstanding performance in orbit,establishing itself as one of the space X-ray telescopes with considerable international influence.
基金supported by the China’s Space Origins Exploration Program,the National Natural Science Foundation of China(Grant Nos.12273010,12333007,12433004,12233002,12373041,and 12422306)the International Partnership Program of Chinese Academy of Sciences(Grant No.113111KYSB20190020)+9 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA15020100)the Spanish MICIU(Grant Nos.PID2021-124581OB-I0,PID2024-155316NB-I00,and 2021SGR00426)the Ramon y Cajal Fellowship(Grant Nos.RYC2021-032718-I,and RYC2018-025950-I)the European Union NextGenerationEU/PRTR,the Spanish MINECO(Grant Nos.PID2022-136828NB-C44,and PID2023-148661NB-I00)the E.U.FEDER Funds,the AGAUR/Generalitat de Catalunya(Grant No.SGR-386/2021)the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)-Projektnummer(Grant No.549824807)the Programma di Ricerca Fondamentale INAF 2023,the National SKA Program of China(Grant No.2020SKA0120300)the National Key R&D Program of China(Grant No.2021YFA0718500)the Xinjiang Tianchi Program,the Hong Kong Government under HKU(Grant No.17304524)the Bagui Scholars Program.
文摘Scheduled for launch in 2030,the enhanced X-ray Timing and Polarization(eXTP)telescope is a Chinese space-based mission aimed at studying extreme conditions and phenomena in astrophysics.eXTP will feature three main payloads:Spectroscopy Focusing Array(SFA),Polarimetry Focusing Array(PFA),and a Wide-field Camera(W2C).This white paper outlines observatory science,incorporating key scientific advances and instrumental changes since the publication of the previous white paper.We will discuss perspectives of eXTP on the research domains of flare stars,supernova remnants,pulsar wind nebulae,cataclysmic variables,X-ray binaries,ultraluminous X-ray sources,active galactic nucleus(AGN),and pulsar-based positioning and timekeeping.
基金supported by the Einstein-Probe(EP)Program which is funded by the Strategic Priority Research Program of the Chinese Academy of Sciences Grant No.XDA15310103.
文摘Purpose The follow-up X-ray telescope(FXT)is one of the two payloads of the Einstein Probe(EP),consisting of the upper composite with the X-ray mirror module as the core,the lower composite with the pnCCD module as the core,and the interface structure.The FXT thermal control subsystem is responsible for the thermal design,thermal implementations,and testing of the entire FXT payload thermal control.Methods A design approach is adopted with passive thermal control technology as the main method and active thermal control technology as a supplement for common components.The X-ray mirror modules are high-precision optical components,utilizing active closed-loop temperature control to ensure high precision and stability.The pnCCD detectors operate at a stable low temperature,with refrigerators used to cool the detector houses,ensuring they can operate under stable low-temperature conditions.The hot ends of the refrigerators are connected to the external radiator panels through heat pipes for heat dissipation.Results The thermal control subsystem of FXT is operating properly in-orbit.All component temperatures meet the design requirements.Conclusion After multiple rounds of design and test verification,FXT was successfully launched with EP and completed in-orbit testing.During the in-orbit testing phase of EP,the function of the FXT thermal control subsystem works well.The temperatures of the components and units are normal.This paper introduces the design of FXT thermal control and the in-orbit performance of the thermal control subsystem.
基金supported by the Strategic Priority Research Program on Space Science,the Chinese Academy of Sciences(Grant No.XDA 15310103).
文摘Purpose The Einstein Probe(EP)satellite is a space X-ray satellite for time-domain astronomy and high-energy astrophysics.The precision control of the optical structure directly affects the imaging quality and positioning accuracy of the Follow-up X-ray Telescope(FXT),playing a crucial role in achieving the on-orbit scientific objectives of the FXT.Higher positioning accuracy makes it easier to identify corresponding bodies for the discovery and positioning of transient sources.Accurate positioning is beneficial for follow-up observations in other bands,such as optical spectroscopy.Methods This article mainly introduces the precision control methods and processes of the FXT optical structure,which have been tested and verified through satellite test.The on-orbit source positioning accuracy of the FXT telescope is within 20 arcseconds(90% confidence level),meeting the requirements of the FXT mission.Results and Conclusion To ensure the accuracy of the EP satellite’s FXT optical structure,measures such as component processing control,installation control,and posttest adjustments are taken on the ground to ensure that the detector mounting position,optical axis deviation,and other precision indicators before and after the satellite lever test meet the design requirements.After a successful launch,through on-orbit calibration,the FXT-A and FXT-B optical axis pointing direction deviation is 39 arcseconds,and the source positioning error is better than 3'' at 68% confidence level.FXT optical structure meets all the requirements from design,processing,installation,etc.,successfully meeting scientific needs.
基金supported by the Einstein Probe(EP)Program which is funded by the"Strategic Priority Research Program"of the Chinese Academy of Sciences(Grant No.XDA15310103).
文摘Purpose:In order to evaluate the mechanical feasibility of the domestic baffle made by wire electrode cutting for the mirror assembly of the Follow-up X-ray Telescope(FXT)onboard the Einstein Probe(EP)mission.Methods:Finite element analysis was performed to compare the structural differences between the domestic baffle made by wire electrode cutting and the eROSITA baffle made by bonding.The finite element models were verified by test data in advance to avoid significant deviations.Finally,the differences in dynamical performances between the FXT mirror assemblies with the two baffles were investigated through modal analysis and frequency response analysis using the pre-verified models.Results and conclusions:The results show that,from the perspective of the entire mirror assembly,their eigenfrequencies remain similar,except for the second lateral eigenfrequency,which shifts forward by approximately 24 Hz in the mirror assembly equipped with the domestic baffle.However,for the X-ray baffles themselves,the axial and lateral eigenfrequencies of the two baffles differ by approximately 49 Hz and 185 Hz,respectively.These eigenfrequencies are staggered,ensuring that over-response is avoided.In terms of response amplification,the domestic baffle,compared to the eROSITA baffle,exhibits inferior axial mechanical characteristics but superior lateral characteristics.In summary,from a mechanical perspective,the domestic baffle is feasible.
基金supported by the Strategic Priority Research Program on Space Science,the Chinese Academy of Sciences Grant No.XDA15310103.
文摘Background The Einstein probe(EP)is an X-ray astronomical satellite dedicated to time-domain astronomy and high-energy astrophysics.Initiated at the end of 2017,it was successfully launched on January 9,2024.The follow-up X-ray telescope(FXT)is a key payload on the EP satellite.The FXT employs PNCCD as its focal plane detector.Its electronic components include the electronic control box(EC-Box),the detector electronics boxes(DE-Box),the refrigerator controller,the movement mechanisms controller,and the temperature control instrument.Methods The FXT conducted functional performance tests in-orbit as planned,including three operating modes of the detector,energy detection range,and energy resolution.Results Since FXT became operational in orbit,all electronic equipment has been working stably.The FXT has an energy detection range of 0.3-10 keV,with an energy resolution of approximately 92 eV@1.25 keV,and an electronic noise of about 3.3e^(-).
基金supported by the Einstein-Probe(EP)Program which is funded by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA1531010301).
文摘Purpose:Mini-magnets of FXT are designed to deflect low-energy electrons that are incident into the camera aperture area,preventing them from reaching the focal plane detector and thereby reducing the noises they generate.Methods:By employing a combination of theoretical calculations and experimental measurements,the parameters of the FXT mini-magnets were obtained,including magnetic field distributions,magnetic moment results,and electron deflection efficiency.Results:The structural and magnetic models of the optimized mini-magnets are presented.Distributions of magnetic field intensity on different planes within the camera aperture are compared with the measured results from the FXT flight models(FMs).The results for the total and separated magnetic moment of two sets of FMs are also provided.Additionally,the deflection efficiency for 25 keV electrons is calculated under various incident conditions.Conclusion:The FMs of mini-magnets show good performance,with the measured values of magnetic field distributions being highly consistent with the theoretical values.A perfect result for total magnetic moment of less than 10mA·m^(2)has been achieved,far better than requirement of 100mA·m^(2).The calculated electron deflection efficiency reached over 99.88%,effectively fulfilling the objective of deflecting electrons in space.
基金based on data obtained with Einstein Probe,a space mission supported by Strategic Priority Program on Space Science of Chinese Academy of Sciences,in collaboration with ESA,MPE and CNES(Grant No.XDA15310000)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB0550200)+5 种基金the National Key R&D Program of China(Grant No.2022YFF0711500)the support by the National Natural Science Foundation of China(Grant Nos.12333004,12321003,12103065,12373040,12021003,12025303,12393814,and 12203071)the China Manned Space Project(Grant Nos.CMS-CSST-2021-A13,and CMS-CSST-2021-B11)the Youth Innovation Promotion Association of the Chinese Academy of Sciencessupported by a Ramón y Cajal fellowship(Grant No.RYC2021-030888-I)financial support from AGAUR,CSIC,MCIN and AEI 10.13039/501100011033(Grant Nos.PID2023-151307NB-I00,PIE 20215AT016,CEX2020-001058-M,and 2021-SGR-01270)。
文摘We report the discovery of a peculiar X-ray transient,EP240408a,by Einstein Probe(EP)and follow-up studies made with EP,Swift,NICER,GROND,ATCA and other ground-based multiwavelength telescopes.The new transient was first detected with Wide-field X-ray Telescope(WXT)on board EP on April 8th,2024,manifested in an intense yet brief X-ray flare lasting for 12 s.The flare reached a peak flux of 3:9×10^(−9) erg cm^(−2) s^(−1) in 0.5-4 keV,∼300 times brighter than the underlying X-ray emission detected throughout the observation.Rapid and more precise follow-up observations by EP/FXT,Swift and NICER confirmed the finding of this new transient.Its X-ray spectrum is non-thermal in 0.5-10 keV,with a power-law photon index varying within 1.8-2.5.The X-ray light curve shows a plateau lasting for∼4 d,followed by a steep decay till becoming undetectable∼10 d after the initial detection.Based on its temporal property and constraints from previous EP observations,an unusual timescale in the range of 7-23 d is found for EP240408a,which is intermediate between the commonly found fast and long-term transients.No counterparts have been found in optical and near-infrared,with the earliest observation at 17 h after the initial X-ray detection,suggestive of intrinsically weak emission in these bands.We demonstrate that the remarkable properties of EP240408a are inconsistent with any of the transient types known so far,by comparison with,in particular,jetted tidal disruption events,gamma-ray bursts,X-ray binaries and fast blue optical transients.The nature of EP240408a thus remains an enigma.We suggest that EP240408a may represent a new type of transients with intermediate timescales of the order of∼10 d.The detection and follow-ups of more of such objects are essential for revealing their origin.
基金support of the Chinese Academy of Sciences through the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA15020100)support by ASI, under the dedicated eXTP agreements and agreement ASI-INAF (Grant No. 2017-14-H.O.)+3 种基金by INAF and INFN under project REDSOXsupport from the Deutsche Zentrum für Luft- und Raumfahrt, the German Aerospce Center (DLR)support of Science Centre (Grant No. 2013/10/M/ST9/00729)support from MINECO (Grant No. ESP2017-82674-R) and FEDER funds
文摘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.
基金supported by Strategic Priority Program on Space Science of Chinese Academy of Sciences,in collaboration with ESA,MPE and CNES(grant Nos.XDA15310303,XDA15310103 and XDA15052100)。
文摘The in-flight instrumental background of the Follow-up X-ray Telescope(FXT)onboard Einstein Probe mis sion is analysed in this work by utilizing observations collected during the performance verification phase and subsequent dedicated filter wheel closed observations.The instrumental backgrounds of the two FXT modules are consistent with each other,with an average rate of~4×10^(-2)counts s^(-1)keV^(-1)in the 0.5-10 keV band for each module.The background is nearly uniformly distributed across the detector area,with a minor increase(<8%)observed along rows.The spatial distribution shows significant modulation by the geomagnetic field.The spectral shapes remain unchanged in 0.5-10 keV at different rates.The long-term temporal variation indicates a periodic change associated with the orbital precession(~57 days).The innovative design of FXT full-frame readout mode enables simultaneous recording of events in both the imaging area(IMG)and the frame store area(FSA)of the pnCCD.FSA event rates show a strong linear correlation with the IMG,based on which the IMG instrumental background modeling is established.
基金project funded by China National Space Administration(CNSA)and the Chinese Academy of Sciences(CAS)support from the National Key Research and Development Program of China(Grant No.2016YFA0400800)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant Nos.XDA04010202,XDA04010300,and XDB23040400)the National Natural Science Foundation of China(Grant Nos.U1838201,and U1838102).
文摘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.
基金supported by the National Program on Key Research and Development Project(Grant No.2016YFA0400800)from the Ministry of Science and Technology of China(MOST)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB23040400)the Hundred Talent Program of Chinese Academy of Sciences,the National Natural Science Foundation of China(Grant Nos.11233001,11503027,11403026,11473027,and11733009)
文摘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 170817A, 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 （SSS17a/AT2017gfo） with very large collection area （M000 cm2） 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 170817A. Meanwhile, Insight-HXMT/HE provides one of the most stringent constraints （-10-7 to 104 erg/cm2/s） for both GRB170817A 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.
基金the Strategic Priority Research Program on Space Science,the Chinese Academy of Sciences(Grant No.XDA040102).
文摘The Low Energy X-ray telescope(LE) is one of the three main instruments of the Insight-Hard X-ray Modulation Telescope(Insight-HXMT). It is equipped with Swept Charge Device(SCD) sensor arrays with a total geometrical area of 384 cm^2 and an energy band from 0.7 to 13 ke V. In order to evaluate the particle induced X-ray background and the cosmic X-ray background simultaneously, LE adopts collimators to define four types of Field Of Views(FOVs), i.e., 1.6°×6°, 4°×6°, 50°-60°×2°-6 oand the blocked ones which block the X-ray by an aluminum cover. LE is constituted of three detector boxes(LEDs) and an electric control box(LEB) and achieves a good energy resolution of 140 e V@5.9 ke V, an excellent time resolution of 0.98 ms, as well as an extremely low pileup(<1%@18000 cts/s). Detailed performance tests and calibration on the ground have been performed,including energy-channel relation, energy response, detection efficiency and time response.
基金support from the National Program on Key Research and Development Project(Grant No.2021YFA0718500)from the Minister of Science and Technology of China(MOST)The authors thank supports from the National Natural Science Foundation of China under Grants 12273043,U1838201,U1838202,U1938102,and U1938108This work was partially supported by the International Partnership Program of Chinese Academy of Sciences(Grant No.113111KYSB20190020).
文摘Purpose The low-energy X-ray telescope(LE)is a main instrument of the Insight-HXMT mission and consists of 96 swept charge devices covering the 1–10 keV energy band.The energy gain and resolution are continuously calibrated by analyzing Cassiopeia A(Cas A)and blank sky data,while the effective areas are also calibrated with the observations of the Crab Nebula.In this paper,we present the evolution of the in-orbit performances of LE in the first 5 years since launch.Methods The Insight-HXMT data analysis software package(HXMTDAS)is utilized to extract the spectra of Cas A,blank sky,and Crab Nebula using different good time interval selections.We fit a model with a power-law continuum and several Gaussian lines to different ranges of Cas A and blank sky spectra to get peak energies of their lines through xspec.After updating the energy gain calibration in CALibration DataBase(CALDB),we rerun the Cas A data to obtain the energy resolution.An empirical function is used to modify the simulated effective areas so that the background-subtracted spectrum of the Crab Nebula can best match the standard model of the Crab Nebula.Results The energy gain,resolution,and effective areas are calibrated every month.The corresponding calibration results are duly updated in CALDB,which can be downloaded and used for the analysis of Insight-HXMT data.Simultaneous observations with NuSTAR and NICER can also be used to verify our derived results.Conclusion LE is a well-calibrated X-ray telescope working in 1–10 keV band.The uncertainty of LE gain is less than 20eV in 2–9 keV band,and the uncertainty of LE resolution is less than 15eV.The systematic errors of LE,compared to the model of the Crab Nebula,are lower than 1.5%in 1–10 keV.
