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
Purpose:The purpose of this study is to investigate the performance of out-of-time events(OoT events)in the Follow-up X-ray Telescope(FXT)onboard the Einstein Probe.The OoT events,registered on the PN-CCD during its r...Purpose:The purpose of this study is to investigate the performance of out-of-time events(OoT events)in the Follow-up X-ray Telescope(FXT)onboard the Einstein Probe.The OoT events,registered on the PN-CCD during its readout time,can provide information on the sources,e.g.,spectral indices,and diagnose the behavior of pile-up.Methods:In order to analyze the characteristics of OoT events,we simulated sources,each of which had been modeled using an absorbed power law combined with Gaussians,in different FXT modes and different luminosities.This allowed us to determine the OoT spectral indices and pile-up effect.Results:In the timing mode of FXT,the OoT events occupy a large proportion and the OoT correction must be done with the assumption that all photons originate from the source position on the CCD.While for some bright sources,the OoT events may be sufficient to derivate the source spectra,especially when pile-up occurs,particularly in the full frame mode and the partial window mode of FXT.Conclusion:We conclude that the OoT events can provide additional information about the celestial sources and can be used to estimate whether the pile-up occurs or not and the scope of pile-up.Furthermore,they can be also used to determine the new sources and improve the detection significance of a source.展开更多
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 National Natural Science Foundation of China under grant No.U1938102.
文摘Purpose:The purpose of this study is to investigate the performance of out-of-time events(OoT events)in the Follow-up X-ray Telescope(FXT)onboard the Einstein Probe.The OoT events,registered on the PN-CCD during its readout time,can provide information on the sources,e.g.,spectral indices,and diagnose the behavior of pile-up.Methods:In order to analyze the characteristics of OoT events,we simulated sources,each of which had been modeled using an absorbed power law combined with Gaussians,in different FXT modes and different luminosities.This allowed us to determine the OoT spectral indices and pile-up effect.Results:In the timing mode of FXT,the OoT events occupy a large proportion and the OoT correction must be done with the assumption that all photons originate from the source position on the CCD.While for some bright sources,the OoT events may be sufficient to derivate the source spectra,especially when pile-up occurs,particularly in the full frame mode and the partial window mode of FXT.Conclusion:We conclude that the OoT events can provide additional information about the celestial sources and can be used to estimate whether the pile-up occurs or not and the scope of pile-up.Furthermore,they can be also used to determine the new sources and improve the detection significance of a source.
