We present the observational results from a detailed timing analysis of the black hole candidate EXO 1846-031 during its outburst in 2019 with the observations of Insight-HXMT,NICER and MAXI.This outburst can be class...We present the observational results from a detailed timing analysis of the black hole candidate EXO 1846-031 during its outburst in 2019 with the observations of Insight-HXMT,NICER and MAXI.This outburst can be classified roughly into four different states.Type-C quasi-periodic oscillations(QPOs)observed by NICER(about 0.1-6 Hz)and Insight-HXMT(about 0.7-8 Hz)are also reported in this work.Meanwhile,we study various physical quantities related to QPO frequency.The QPO rms-frequency relationship in the energy band 1-10 keV indicates that there is a turning pointing in frequency around2 Hz,which is similar to that of GRS 1915+105.A possible hypothesis for the relationship above may be related to the inclination of the source,which may require a high inclination to explain it.The relationships between QPO frequency and QPO rms,hardness,total fractional rms and count rate have also been found in other transient sources,which can indicate that the origin of type-C QPOs is non-thermal.展开更多
The LE is the low energy telescope that is carried on Insight-HXMT.It uses swept charge devices(SCDs)to detect soft X-ray photons.LE’s time response is caused by the structure of the SCDs.With theoretical analysis an...The LE is the low energy telescope that is carried on Insight-HXMT.It uses swept charge devices(SCDs)to detect soft X-ray photons.LE’s time response is caused by the structure of the SCDs.With theoretical analysis and Monte Carlo simulations we discuss the influence of LE time response(LTR)on the timing analysis from three aspects:the power spectral density,the pulse profile and the time lag.After the LTR,the value of power spectral density monotonously decreases with the increasing frequency.The power spectral density of a sinusoidal signal reduces by a half at frequency 536 Hz.The corresponding frequency for quasi-periodic oscillation(QPO)signals is 458 Hz.The root mean square(RMS)of QPOs holds a similar behaviour.After the LTR,the centroid frequency and full width at half maxima(FWHM)of QPOs signals do not change.The LTR reduces the RMS of pulse profiles and shifts the pulse phase.In the time domain,the LTR only reduces the peak value of the cross-correlation function while it does not change the peak position;thus it will not affect the result of the time lag.When considering the time lag obtained from two instruments and one among them is LE,a 1.18 ms lag is expected caused by the LTR.The time lag calculated in the frequency domain is the same as that in the time domain.展开更多
Purpose The Einstein Probe(EP)is a space X-ray mission dedicated to the time-domain astrophysics,aiming to discover high-energy transients and monitor variable objects.As a principal scientific payload onboard EP,the ...Purpose The Einstein Probe(EP)is a space X-ray mission dedicated to the time-domain astrophysics,aiming to discover high-energy transients and monitor variable objects.As a principal scientific payload onboard EP,the Follow-up X-ray Telescope(FXT)mainly responses for prompt and deep follow-up observations of the triggered targets by EP-WXT and discovers and characterizes X-ray transients,particularly faint or distant X-ray transients.Since these transient signals fade rapidly or evolve dramatically,a fast and reliable analysis of the FXT data is essential to discover them and trigger timely and efficient follow-up observations,which is important to identify the nature of these sources.Methods To address this issue,we develop a real-time source search toolkit to automatically process EP-FXT observations in real time,detecting all the sources in the field of view of FXT,extracting their scientific information,and searching for transients and bursts.Accordingly,the toolkit consists of three modules:source detection,source information extraction,and source identification.Results The toolkit outcomes a quick-look database:1)a series of high-level scientific products for every observed source,such as the position,count rate,flux,variability amplitude,hardness,light curve,an absorbed powerlaw or blackbody model fitted spectrum,and the power density spectrum;2)transients and bursts;3)source list;4)sky map.As the software is automatically running,this quick-look database is continuously updated.Conclusion The real-time source search toolkit can process all the observed data and effectively meets the fast source search requirements of FXT.展开更多
Purpose Background removal is an important issue in data reduction for the follow-up X-ray telescope(FXT)onboard the Einstein Probe(EP),particularly for the particle-induced background.They appear in various charge pa...Purpose Background removal is an important issue in data reduction for the follow-up X-ray telescope(FXT)onboard the Einstein Probe(EP),particularly for the particle-induced background.They appear in various charge patterns in the focal plane PN-CCD,such as straight tracks,isolated showers and broad rectangular swathes.Methods We use the data obtained with the FXT mirror assembly covered,which are due to particle-induced background,to study the methods for rejecting such background.Results The particle-induced background in the FXT comprises background directly caused by particles,as well as instrument events that are also due to particles.A new rejection method,which involves cluster identification,and threshold veto for number of hits in rows and columns,is applied to remove the particle-induced background.The remaining background can be eliminated by the event reconstruction algorithm and event veto in subsequent FXT data reduction.Conclusion It is shown that their methods can achieve a background rejection efficiency of>99.8%.Additionally,there has been a notable decrease in the number of spikes in the light curves of the FXT.Furthermore,we found the instrument background is attributed to a combination of particles and CAMEX electronics.展开更多
Purpose The Follow-up X-ray Telescope(FXT)is a principal scientific payload onboard the Einstein Probe(EP).It is designed to be capable of localizing X-ray sources,measuring the energy spectra in X-ray band of 0.3-10 ...Purpose The Follow-up X-ray Telescope(FXT)is a principal scientific payload onboard the Einstein Probe(EP).It is designed to be capable of localizing X-ray sources,measuring the energy spectra in X-ray band of 0.3-10 keV,and in some cases,performing observations with high time resolution.The FXT consists of two X-ray mirror modules(FXTA and FXTB),each containing 54 nested Wolter-I paraboloid-hyperboloid mirror shells.Each module is equipped with a PN-CCD as the focal plane detector.In order to complement the capabilities of the FXT,the PN-CCD offers three readout modes,full field of view imaging with low time resolution mode(FF mode),partial window imaging with moderate time resolution mode(PW mode)and high time resolution mode(TM mode).These different modes require tools and algorithms for data reduction and analysis.Methods A software package is utilized to achieve the FXT data analysis processing and extract scientific products.In the data reduction,time correction,computation of the PI values,elimination of the events caused by particles,identification of anomalous pixels and columns,and event reconstruction will be provided.Generic tools from HEASOFT,such as Xselect and Xspec,can also be used to manipulate the data files of the FXT.Results The FXT data are distributed in FITS format files.Its software package was created by taking the FXT-specific tools and the generic tools,and re-packaging them as stand-alone application.And the FXT-specific tools are written in ftools style,and the run styles are fully compatible with the HEASOFT software.Conclusion This package can achieve the FXT data analysis processing for all three science modes and effectively meets the data analysis requirements of the FXT.展开更多
The calibration database(CALDB)for the Einstein probe’s follow-up X-ray telescope(EP-FXT)is designed to store essential calibration files such as point spread function(PSF)files,vignetting files,ancillary response fi...The calibration database(CALDB)for the Einstein probe’s follow-up X-ray telescope(EP-FXT)is designed to store essential calibration files such as point spread function(PSF)files,vignetting files,ancillary response files(ARFs),and response matrix files(RMFs).These files are essential to ensure the accuracy and reliability of scientific data analysis.We adopt a structured approach to organize the calibration data by using standardized file naming conventions and formats.Each file type includes specific extensions and binary tables to capture detailed calibration parameters.For example,the ancillary response file contains energy and effective area data,while the response matrix file includes response functions and energy-channel relationships.Keywords are systematically embedded within calibration files in the CALDB to support efficient indexing and retrieval.The calibration database successfully supports the diverse calibration requirements of EP-FXT,accommodating various observation modes and filters.It provides a robust framework for storing,retrieving,and updating calibration data,significantly reducing systematic errors in data analysis.The design ensures scalability and adaptability,allowing for future enhancements.By maintaining high calibration data integrity and accessibility,the database plays a critical role in maximizing the scientific return from EP-FXT observations,enabling precise calibration across different observational scenarios.展开更多
Purpose In this work,we present the pile-up fractions on the follow-up X-ray telescope(FXT)onboard Einstein Probe using its different read-out modes and filters for various source fluxes.This investigation could help ...Purpose In this work,we present the pile-up fractions on the follow-up X-ray telescope(FXT)onboard Einstein Probe using its different read-out modes and filters for various source fluxes.This investigation could help understand the pile-up effect on FXT and choose the filter and readout mode when observing dedicated sources.Methods We use the Simulation of X-ray Telescopes package to conduct the simulation from incidence of photons from celestial sources to the detection on the FXT pnCCD.Based on the reconstructed signals,we make a statistic on the counts of incident photons and detected events to obtain the pile-up fraction for each set of read-out mode and filter configuration.Results and conclusion From the perspective of incident photons among all detected events,the pile-up fraction increases monotonically with the brightness of the source.From the viewpoints of valid detected events,the fraction values exhibit an initial nonlinear increase,followed by a decrease,and a subsequent increase as the source fluxes increase,attributed to the presence of pile-up effects and the selection criteria for valid events.For some certain fluxes,the fraction value is larger in faster readout modes than lower modes.From the viewpoint of incident photon in valid detected events,a 10% pile-up fraction corresponds to 5 mCrab in full frame mode(FF),120 mCrab in partial windowed mode(PW),3 Crab in Timing mode(TM)under the medium filter type.At these fluxes,the deviation of the fitted photon indices is within 10% from that of the input source model.展开更多
In situ anchor of magnetic Fe304 nanoparticles （NPs） onto the surface of natural maifanite was realized by chemical oxidation coprecipitation in hot alkaline solution. The Fe304/maifanite composites were characteriz...In situ anchor of magnetic Fe304 nanoparticles （NPs） onto the surface of natural maifanite was realized by chemical oxidation coprecipitation in hot alkaline solution. The Fe304/maifanite composites were characterized by XRD, FTIR, SEM, and TEM. These results indicated that polycrystalline Fe304 NPs with inverse spinel structure were formed and tightly dispersed on maifanite surface. Based on the measurement of surface Zeta potential of maifanite at different medium pHs, the possible combination mechanism between natural maifanite and Fe304 NPs was proposed. Then, the as- obtained composites were developed as highly efficient heterogeneous Fenton-like catalyst for the discoloration of an azo dye, Methyl Orange （MO）. The comparative tests on MO discoloration in different systems revealed that Fe304/maifanite composite exhibited much higher Fenton-like catalytic activity than Fe304 NPs and the heterogeneous Fenton- like reaction governed the discoloration of MO. Kinetic results clearly showed that MO discoloration process followed the second-order kinetic model. Fe304/maifanite compo- sites exhibited the typical ferromagnetic property detected by VSM and could be easily separated from solution by an external magnetic field.展开更多
基金the HXMT mission,a project funded by China National Space Administration(CNSA)and the Chinese Academy of Sciences(CAS)supported by the National Key R&D Program of China(2016YFA0400800)the National Natural Science Foundation of China(Grant Nos.11673023,U1838201,U1838115,U1838111,U1838202,11733009 and U1838108)。
文摘We present the observational results from a detailed timing analysis of the black hole candidate EXO 1846-031 during its outburst in 2019 with the observations of Insight-HXMT,NICER and MAXI.This outburst can be classified roughly into four different states.Type-C quasi-periodic oscillations(QPOs)observed by NICER(about 0.1-6 Hz)and Insight-HXMT(about 0.7-8 Hz)are also reported in this work.Meanwhile,we study various physical quantities related to QPO frequency.The QPO rms-frequency relationship in the energy band 1-10 keV indicates that there is a turning pointing in frequency around2 Hz,which is similar to that of GRS 1915+105.A possible hypothesis for the relationship above may be related to the inclination of the source,which may require a high inclination to explain it.The relationships between QPO frequency and QPO rms,hardness,total fractional rms and count rate have also been found in other transient sources,which can indicate that the origin of type-C QPOs is non-thermal.
基金the National Key R&D Program of China(2016YFA0400800)the National Natural Science Foundation of China(Grant Nos.U1838201,U1838202,U1838101 and U1938109)the Insight-HXMT mission,a project funded by China National Space Administration(CNSA)and the Chinese Academy of Sciences(CAS)。
文摘The LE is the low energy telescope that is carried on Insight-HXMT.It uses swept charge devices(SCDs)to detect soft X-ray photons.LE’s time response is caused by the structure of the SCDs.With theoretical analysis and Monte Carlo simulations we discuss the influence of LE time response(LTR)on the timing analysis from three aspects:the power spectral density,the pulse profile and the time lag.After the LTR,the value of power spectral density monotonously decreases with the increasing frequency.The power spectral density of a sinusoidal signal reduces by a half at frequency 536 Hz.The corresponding frequency for quasi-periodic oscillation(QPO)signals is 458 Hz.The root mean square(RMS)of QPOs holds a similar behaviour.After the LTR,the centroid frequency and full width at half maxima(FWHM)of QPOs signals do not change.The LTR reduces the RMS of pulse profiles and shifts the pulse phase.In the time domain,the LTR only reduces the peak value of the cross-correlation function while it does not change the peak position;thus it will not affect the result of the time lag.When considering the time lag obtained from two instruments and one among them is LE,a 1.18 ms lag is expected caused by the LTR.The time lag calculated in the frequency domain is the same as that in the time domain.
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.XDA15310303the National Natural Science Foundation of China under Grant No.U2038102,U1938102.
文摘Purpose The Einstein Probe(EP)is a space X-ray mission dedicated to the time-domain astrophysics,aiming to discover high-energy transients and monitor variable objects.As a principal scientific payload onboard EP,the Follow-up X-ray Telescope(FXT)mainly responses for prompt and deep follow-up observations of the triggered targets by EP-WXT and discovers and characterizes X-ray transients,particularly faint or distant X-ray transients.Since these transient signals fade rapidly or evolve dramatically,a fast and reliable analysis of the FXT data is essential to discover them and trigger timely and efficient follow-up observations,which is important to identify the nature of these sources.Methods To address this issue,we develop a real-time source search toolkit to automatically process EP-FXT observations in real time,detecting all the sources in the field of view of FXT,extracting their scientific information,and searching for transients and bursts.Accordingly,the toolkit consists of three modules:source detection,source information extraction,and source identification.Results The toolkit outcomes a quick-look database:1)a series of high-level scientific products for every observed source,such as the position,count rate,flux,variability amplitude,hardness,light curve,an absorbed powerlaw or blackbody model fitted spectrum,and the power density spectrum;2)transients and bursts;3)source list;4)sky map.As the software is automatically running,this quick-look database is continuously updated.Conclusion The real-time source search toolkit can process all the observed data and effectively meets the fast source search requirements of FXT.
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.XDA15310000the National Natural Science Foundation of China under grant No.U1938102.
文摘Purpose Background removal is an important issue in data reduction for the follow-up X-ray telescope(FXT)onboard the Einstein Probe(EP),particularly for the particle-induced background.They appear in various charge patterns in the focal plane PN-CCD,such as straight tracks,isolated showers and broad rectangular swathes.Methods We use the data obtained with the FXT mirror assembly covered,which are due to particle-induced background,to study the methods for rejecting such background.Results The particle-induced background in the FXT comprises background directly caused by particles,as well as instrument events that are also due to particles.A new rejection method,which involves cluster identification,and threshold veto for number of hits in rows and columns,is applied to remove the particle-induced background.The remaining background can be eliminated by the event reconstruction algorithm and event veto in subsequent FXT data reduction.Conclusion It is shown that their methods can achieve a background rejection efficiency of>99.8%.Additionally,there has been a notable decrease in the number of spikes in the light curves of the FXT.Furthermore,we found the instrument background is attributed to a combination of particles and CAMEX electronics.
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.XDA15310000the National Natural Science Foundation of China under Grant No.U1938102.
文摘Purpose The Follow-up X-ray Telescope(FXT)is a principal scientific payload onboard the Einstein Probe(EP).It is designed to be capable of localizing X-ray sources,measuring the energy spectra in X-ray band of 0.3-10 keV,and in some cases,performing observations with high time resolution.The FXT consists of two X-ray mirror modules(FXTA and FXTB),each containing 54 nested Wolter-I paraboloid-hyperboloid mirror shells.Each module is equipped with a PN-CCD as the focal plane detector.In order to complement the capabilities of the FXT,the PN-CCD offers three readout modes,full field of view imaging with low time resolution mode(FF mode),partial window imaging with moderate time resolution mode(PW mode)and high time resolution mode(TM mode).These different modes require tools and algorithms for data reduction and analysis.Methods A software package is utilized to achieve the FXT data analysis processing and extract scientific products.In the data reduction,time correction,computation of the PI values,elimination of the events caused by particles,identification of anomalous pixels and columns,and event reconstruction will be provided.Generic tools from HEASOFT,such as Xselect and Xspec,can also be used to manipulate the data files of the FXT.Results The FXT data are distributed in FITS format files.Its software package was created by taking the FXT-specific tools and the generic tools,and re-packaging them as stand-alone application.And the FXT-specific tools are written in ftools style,and the run styles are fully compatible with the HEASOFT software.Conclusion This package can achieve the FXT data analysis processing for all three science modes and effectively meets the data analysis requirements of the FXT.
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.XDA15310303.
文摘The calibration database(CALDB)for the Einstein probe’s follow-up X-ray telescope(EP-FXT)is designed to store essential calibration files such as point spread function(PSF)files,vignetting files,ancillary response files(ARFs),and response matrix files(RMFs).These files are essential to ensure the accuracy and reliability of scientific data analysis.We adopt a structured approach to organize the calibration data by using standardized file naming conventions and formats.Each file type includes specific extensions and binary tables to capture detailed calibration parameters.For example,the ancillary response file contains energy and effective area data,while the response matrix file includes response functions and energy-channel relationships.Keywords are systematically embedded within calibration files in the CALDB to support efficient indexing and retrieval.The calibration database successfully supports the diverse calibration requirements of EP-FXT,accommodating various observation modes and filters.It provides a robust framework for storing,retrieving,and updating calibration data,significantly reducing systematic errors in data analysis.The design ensures scalability and adaptability,allowing for future enhancements.By maintaining high calibration data integrity and accessibility,the database plays a critical role in maximizing the scientific return from EP-FXT observations,enabling precise calibration across different observational scenarios.
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.XDA15310303 and No.XDA15310000.
文摘Purpose In this work,we present the pile-up fractions on the follow-up X-ray telescope(FXT)onboard Einstein Probe using its different read-out modes and filters for various source fluxes.This investigation could help understand the pile-up effect on FXT and choose the filter and readout mode when observing dedicated sources.Methods We use the Simulation of X-ray Telescopes package to conduct the simulation from incidence of photons from celestial sources to the detection on the FXT pnCCD.Based on the reconstructed signals,we make a statistic on the counts of incident photons and detected events to obtain the pile-up fraction for each set of read-out mode and filter configuration.Results and conclusion From the perspective of incident photons among all detected events,the pile-up fraction increases monotonically with the brightness of the source.From the viewpoints of valid detected events,the fraction values exhibit an initial nonlinear increase,followed by a decrease,and a subsequent increase as the source fluxes increase,attributed to the presence of pile-up effects and the selection criteria for valid events.For some certain fluxes,the fraction value is larger in faster readout modes than lower modes.From the viewpoint of incident photon in valid detected events,a 10% pile-up fraction corresponds to 5 mCrab in full frame mode(FF),120 mCrab in partial windowed mode(PW),3 Crab in Timing mode(TM)under the medium filter type.At these fluxes,the deviation of the fitted photon indices is within 10% from that of the input source model.
基金This work was financially supported by the National Natural Science Foundation of China （Grant No. 51404083）, the Program for New Century Excellent Talents in Heilongjiang Provincial Universities （Grant No. 1253-NCET-010）, the Research Development Fund of Nianzishan Institute of Maifanite, Qiqihaer （Grant No. 201406）, and the Natural Science Foundation of Heilongjiang Province, China （Grant No. E2015065）.
文摘In situ anchor of magnetic Fe304 nanoparticles （NPs） onto the surface of natural maifanite was realized by chemical oxidation coprecipitation in hot alkaline solution. The Fe304/maifanite composites were characterized by XRD, FTIR, SEM, and TEM. These results indicated that polycrystalline Fe304 NPs with inverse spinel structure were formed and tightly dispersed on maifanite surface. Based on the measurement of surface Zeta potential of maifanite at different medium pHs, the possible combination mechanism between natural maifanite and Fe304 NPs was proposed. Then, the as- obtained composites were developed as highly efficient heterogeneous Fenton-like catalyst for the discoloration of an azo dye, Methyl Orange （MO）. The comparative tests on MO discoloration in different systems revealed that Fe304/maifanite composite exhibited much higher Fenton-like catalytic activity than Fe304 NPs and the heterogeneous Fenton- like reaction governed the discoloration of MO. Kinetic results clearly showed that MO discoloration process followed the second-order kinetic model. Fe304/maifanite compo- sites exhibited the typical ferromagnetic property detected by VSM and could be easily separated from solution by an external magnetic field.
