Theoretical investigations into the deflection angle caused by microlenses offer a direct path to uncovering principles of the cosmological microlensing effect.This work specifically concentrates on the the probabilit...Theoretical investigations into the deflection angle caused by microlenses offer a direct path to uncovering principles of the cosmological microlensing effect.This work specifically concentrates on the the probability density function(PDF)of the light deflection angle induced by microlenses.We have made several significant improvements to the widely used formula from Katz et al.First,we update the coefficient from 3.05 to 1.454,resulting in a better fit between the theoretical PDF and our simulation results.Second,we developed an elegant fitting formula for the PDF that can replace its integral representation within a certain accuracy,which is numerically divergent unless arbitrary upper limits are chosen.Third,to facilitate further theoretical work in this area,we have identified a more suitable Gaussian approximation for the fitting formula.展开更多
As a completely independent method,the measurement of time delay of strongly lensed quasars(TDSL)are crucial to resolve the Hubble tension.Extensive monitoring is required but so far limited to a small sample of stron...As a completely independent method,the measurement of time delay of strongly lensed quasars(TDSL)are crucial to resolve the Hubble tension.Extensive monitoring is required but so far limited to a small sample of strongly lensed quasars.Together with several partner institutes,Beijing Normal University is constructing a 1.93 m reflector telescope at the Muztagh-Ata site in west China,which has the world class observing conditions with median seeing of 082 and median sky brightness of 21.74 mag arcsec-2 in V-band during the dark time.The telescope will be equipped with both a three-channel imager/photometer which covers 3500–11,000?wavelength band,and a low-medium resolution(λ/δλ=500/2000/7500)spectrograph.In this paper,we investigate the capability of the Muztagh-Ata 1.93 m telescope in measuring time delays of strongly lensed quasars.We generate mock strongly lensed quasar systems and light curves with microlensing effects based on five known strongly lensed quasars,i.e.,RX J1131-1231,HE 0435-1223,PG 1115+080,WFI 2033-4723 and SDSS 1206+4332.In particular,RX J1131-1231 is generated based on the lens modeling results of Suyu et al.Due to the lack of enough information,the other four systems are calculated by a simple analytical approximation.According to simulations,for RX J1131-like systems(wide variation in time delay between images)the TDSL measurement can be achieved with the precision aboutΔt=0.5 day with four seasons campaign length and 1 day cadence.This accuracy is comparable to the up-coming TDCOSMO project.And it would be better when the campaign length keeps longer and with high cadence.As a result,the capability of the Muztagh-Ata 1.93 m telescope allows it to join the network of TDSL observatories.It will enrich the database for strongly lensed quasar observations and make more precise measurements of time delays,especially considering the unique coordinate of the site.展开更多
We tested a new model of CMOS detector manufactured by the Gpixel Inc,for potential space astronomical application.In laboratory,we obtain some bias images under the typical application environment.In these bias image...We tested a new model of CMOS detector manufactured by the Gpixel Inc,for potential space astronomical application.In laboratory,we obtain some bias images under the typical application environment.In these bias images,clear random row noise pattern is observed.The row noise also contains some characteristic spatial frequencies.We quantitatively estimated the impact of this feature to photometric measurements,by making simulated images.We compared different bias noise types under strict parameter control.The result shows the row noise will significantly deteriorate the photometric accuracy.It effectively increases the readout noise by a factor of2-10.However,if it is properly removed,the image quality and photometric accuracy will be significantly improved.展开更多
We present a Python based parameter inference system for the gravitational wave(GW)measured in the millihertz band.This system includes the following features:the GW waveform originated from the massive black hole bin...We present a Python based parameter inference system for the gravitational wave(GW)measured in the millihertz band.This system includes the following features:the GW waveform originated from the massive black hole binaries(MBHB),the stationary instrumental Gaussian noise,the higher-order harmonic modes,the full response function from the time delay interferometry and the Gaussian likelihood function with the dynamic nested parameter sampler.In particular,we highlight the role of higher-order modes.By including these modes,the luminosity distance estimation precision can be improved roughly by a factor of 50,compared with the case with only the leading order(l=2,|m|=2)mode.This is due to the response functions of different harmonic modes on the inclination angle are different.Hence,it can help to break the distance-inclination degeneracy.Furthermore,we show the robustness of testing general relativity(GR)by using higher-order harmonics.Our results show that the GW from MBHB can simultaneously constrain four of the higher harmonic amplitudes(deviation from GR)with 95%confidence level of c21=0.54-1.05+0.82,c32=-0.65-1.42+3.02,c33=0.56-0.96^(+0.79) and c44=1.57-2.19^(+3.22),respectively.展开更多
We report the properties of more than 800 bursts detected from the repeating fast radio burst(FRB)source FRB 20201124A with the Five-hundred-meter Aperture Spherical radio Telescope during an extremely active episode ...We report the properties of more than 800 bursts detected from the repeating fast radio burst(FRB)source FRB 20201124A with the Five-hundred-meter Aperture Spherical radio Telescope during an extremely active episode on UTC 2021 September 25th-28th in a series of four papers.In this fourth paper of the series,we present a systematic search of the spin period and linear acceleration of the source object from both 996 individual pulse peaks and the dedispersed time series.No credible spin period was found from this data set.We rule out the presence of significant periodicity in the range between 1 ms and 100 s with a pulse duty cycle<0.49±0.08(when the profile is defined by a von-Mises function,not a boxcar function)and linear acceleration up to 300 m s^(-2)in each of the four one-hour observing sessions,and up to 0.6 m s^(-2)in all 4 days.These searches contest theoretical scenarios involving a 1 ms–100 s isolated magnetar/pulsar with surface magnetic field<10^(15)G and a small duty cycle(such as in a polar-cap emission mode)or a pulsar with a companion star or black hole up to 100 M_(⊙)and P_(b)>10 hr.We also perform a periodicity search of the fine structures and identify 53 unrelated millisecond-timescale“periods”in multicomponents with the highest significance of 3.9σ.The“periods”recovered from the fine structures are neither consistent nor harmonically related.Thus they are not likely to come from a spin period.We caution against claiming spin periodicity with significance below~4σwith multi-components from one-off FRBs.We discuss the implications of our results and the possible connections between FRB multi-components and pulsar microstructures.展开更多
An empirical stellar spectral library with large coverage of stellar parameters is essential for stellar population synthesis and studies of stellar evolution.In this work,we present Stellar Spectra Factory(SSF),a too...An empirical stellar spectral library with large coverage of stellar parameters is essential for stellar population synthesis and studies of stellar evolution.In this work,we present Stellar Spectra Factory(SSF),a tool to generate empirical-based stellar spectra from arbitrary stellar atmospheric parameters.The relative flux-calibrated empirical spectra can be predicted by SSF given arbitrary effective temperature,surface gravity,and metallicity.SSF constructs the interpolation approach based on the Stellar LAbel Machine,using ATLAS-A library,which contains spectra covering from O type to M type,as the training data set.SSF is composed of four data-driven sub-models to predict empirical stellar spectra.Sub-model SSF-N can generate spectra from A to K type and some M giant stars,covering 3700<T_(eff)<8700 K,0<logg<dex,and-1.5<[M/H]<0.5 dex.Sub-model SSF-gM is mainly used to predict M giant spectra with 3520<T_(eff)<4000 K and-1.5<[M/H]<0.4 dex.Sub-model SSF-dM is for generating M dwarf spectra with 3295<T_(eff)<4040 K,-1.0<[M/H]<0.1 dex.Sub-model SSF-B can predict B-type spectra with 9000<T_(eff)<24,000 K and-5.2<M_(G)<1.5 mag.The accuracy of the predicted spectra is validated by comparing the flux of predicted spectra to those with same stellar parameters selected from the known spectral libraries,MILES and MaStar.The averaged difference of flux over optical wavelength between the predicted spectra and the corresponding ones in MILES and MaStar is less than 5%.More verification is conducted between the magnitudes calculated from the integration of the predicted spectra and the observations in PS1 and APASS bands with the same stellar parameters.No significant systematic difference is found between the predicted spectra and the photometric observations.The uncertainty is 0.08 mag in the r band for SSF-gM when comparing with the stars with the same stellar parameters selected from PS1.The uncertainty becomes 0.31 mag in the i band for SSF-dM when comparing with the stars with the same stellar parameters selected from APASS.展开更多
We present the interstellar scintillation analysis of fast radio burst(FRB)20220912A during its extremely active episode in 2022using data from the Five-hundred-meter Aperture Spherical Radio Telescope(FAST).We detect...We present the interstellar scintillation analysis of fast radio burst(FRB)20220912A during its extremely active episode in 2022using data from the Five-hundred-meter Aperture Spherical Radio Telescope(FAST).We detect a scintillation arc in the FRB’s secondary spectrum,which describes the power in terms of the scattered FRB signals’time delay and Doppler shift.The arc indicates that the scintillation is caused by a highly localized region.Our analysis favors a Milky Way origin of the ionized interstellar medium(IISM)for the localized scattering medium but cannot rule out a host galaxy origin.We present our method for detecting the scintillation arc,which can be applied generally to sources with irregularly spaced bursts or pulses.These methods could help shed light on the complex interstellar environment surrounding the FRBs and in our Galaxy.展开更多
Identifying strong lensing gravitational wave(SLGW)events is of utmost importance in astrophysics as we approach the historic first detection of SLGW amidst the growing number of gravitational wave(GW)events.Currently...Identifying strong lensing gravitational wave(SLGW)events is of utmost importance in astrophysics as we approach the historic first detection of SLGW amidst the growing number of gravitational wave(GW)events.Currently,one crucial method for identifying SLGW signals involves assessing the overlap of parameters between two GWs.However,the distribution of discrete matter,such as stars and sub-halos,within the strong lensing galaxy can imprint a wave optical(WO)effect on the SLGW waveform.These frequency dependent imprints introduce biases in parameter estimation and impact SLGW identification.In this study,we assess the influence of the stellar microlensing field embedded in a strong lensing galaxy.Our findings demonstrate that the WO effect reduces the detection efficiency of SLGW by 5%-50%for various false alarm probabilities per pair(FAPper pair).Specifically,at an FAPper pairof 10^(-5),the detection efficiency decreases from~10%to~5%.Consequently,the presence of the microlensing field can result in missing half of the strong lensing candidates.Additionally,the microlensing WO effect introduces a noticeable bias in intrinsic parameters,particularly for chirp mass and mass ratio.However,it has tiny influence on extrinsic parameters.Considering all parameters,~30%of events exhibit a 1σparameter bias,~12%exhibit a 2σparameter bias,and~5%exhibit a 3σparameter bias.展开更多
For the stochastic gravitational wave backgrounds(SGWBs)search centred at the milli-Hz band,the galactic foreground produced by white dwarf binaries(WDBs)within the Milky Way contaminates the extra-galactic signal sev...For the stochastic gravitational wave backgrounds(SGWBs)search centred at the milli-Hz band,the galactic foreground produced by white dwarf binaries(WDBs)within the Milky Way contaminates the extra-galactic signal severely.Because of the anisotropic distribution pattern of the WDBs and the motion of the space-borne gravitational wave interferometer constellation,the time-domain data stream will show an annual modulation.This property is fundamentally diferent from those of the SGWBs.In this article,we propose a new filtering method for the data vector based on the annual modulation phenomenon.We apply the resulted inverse variance filter to the LISA Data Challenge.The result shows that for the weaker SGWB signal,such as energy density Ω_(astro)=1×10^(-12),the filtering method can enhance the posterior distribution peak prominently.For the stronger signal,such as Ω_(astro)=3×10^(-12),the method can improve the Bayesian evidence from“substantial”to“strong”against null hypotheses.This method is model-independent and self-contained.It does not ask for other types of information besides the gravitational wave data.展开更多
基金supported by the National Natural Science Foundation of China(NSFC,Grant Nos.U1931210,11673065 and 11273061)funds the NBSDC-DB-10(No.2020000088)the science research grants from the China Manned Space Project with No.CMS-CSST-2021-A12。
文摘Theoretical investigations into the deflection angle caused by microlenses offer a direct path to uncovering principles of the cosmological microlensing effect.This work specifically concentrates on the the probability density function(PDF)of the light deflection angle induced by microlenses.We have made several significant improvements to the widely used formula from Katz et al.First,we update the coefficient from 3.05 to 1.454,resulting in a better fit between the theoretical PDF and our simulation results.Second,we developed an elegant fitting formula for the PDF that can replace its integral representation within a certain accuracy,which is numerically divergent unless arbitrary upper limits are chosen.Third,to facilitate further theoretical work in this area,we have identified a more suitable Gaussian approximation for the fitting formula.
基金supported by the China Manned Space Project with No.CMS-CSST-2021-A12the National Natural Science Foundation of China under Grant Nos.11973016,U2031209,11873006 and U1931210。
文摘As a completely independent method,the measurement of time delay of strongly lensed quasars(TDSL)are crucial to resolve the Hubble tension.Extensive monitoring is required but so far limited to a small sample of strongly lensed quasars.Together with several partner institutes,Beijing Normal University is constructing a 1.93 m reflector telescope at the Muztagh-Ata site in west China,which has the world class observing conditions with median seeing of 082 and median sky brightness of 21.74 mag arcsec-2 in V-band during the dark time.The telescope will be equipped with both a three-channel imager/photometer which covers 3500–11,000?wavelength band,and a low-medium resolution(λ/δλ=500/2000/7500)spectrograph.In this paper,we investigate the capability of the Muztagh-Ata 1.93 m telescope in measuring time delays of strongly lensed quasars.We generate mock strongly lensed quasar systems and light curves with microlensing effects based on five known strongly lensed quasars,i.e.,RX J1131-1231,HE 0435-1223,PG 1115+080,WFI 2033-4723 and SDSS 1206+4332.In particular,RX J1131-1231 is generated based on the lens modeling results of Suyu et al.Due to the lack of enough information,the other four systems are calculated by a simple analytical approximation.According to simulations,for RX J1131-like systems(wide variation in time delay between images)the TDSL measurement can be achieved with the precision aboutΔt=0.5 day with four seasons campaign length and 1 day cadence.This accuracy is comparable to the up-coming TDCOSMO project.And it would be better when the campaign length keeps longer and with high cadence.As a result,the capability of the Muztagh-Ata 1.93 m telescope allows it to join the network of TDSL observatories.It will enrich the database for strongly lensed quasar observations and make more precise measurements of time delays,especially considering the unique coordinate of the site.
基金support by the National Key R&D Program of China No.2022YFF0503400。
文摘We tested a new model of CMOS detector manufactured by the Gpixel Inc,for potential space astronomical application.In laboratory,we obtain some bias images under the typical application environment.In these bias images,clear random row noise pattern is observed.The row noise also contains some characteristic spatial frequencies.We quantitatively estimated the impact of this feature to photometric measurements,by making simulated images.We compared different bias noise types under strict parameter control.The result shows the row noise will significantly deteriorate the photometric accuracy.It effectively increases the readout noise by a factor of2-10.However,if it is properly removed,the image quality and photometric accuracy will be significantly improved.
基金supported by the National Key R&D Program of China No.2021YFC2203001。
文摘We present a Python based parameter inference system for the gravitational wave(GW)measured in the millihertz band.This system includes the following features:the GW waveform originated from the massive black hole binaries(MBHB),the stationary instrumental Gaussian noise,the higher-order harmonic modes,the full response function from the time delay interferometry and the Gaussian likelihood function with the dynamic nested parameter sampler.In particular,we highlight the role of higher-order modes.By including these modes,the luminosity distance estimation precision can be improved roughly by a factor of 50,compared with the case with only the leading order(l=2,|m|=2)mode.This is due to the response functions of different harmonic modes on the inclination angle are different.Hence,it can help to break the distance-inclination degeneracy.Furthermore,we show the robustness of testing general relativity(GR)by using higher-order harmonics.Our results show that the GW from MBHB can simultaneously constrain four of the higher harmonic amplitudes(deviation from GR)with 95%confidence level of c21=0.54-1.05+0.82,c32=-0.65-1.42+3.02,c33=0.56-0.96^(+0.79) and c44=1.57-2.19^(+3.22),respectively.
基金supported by the National SKA Program of China(Nos.2020SKA0120200 and 2020SKA0120100)the National Natural Science Foundation of China(Grant Nos.12041303,11873067 and 12041304)+4 种基金the National Key R&D Program of China(Nos.2017YFA0402600,2021YFA0718500 and 2017YFA0402602)the CAS-MPG LEGACY project,the Max-Planck Partner Group,the Key Research Project of Zhejiang Lab(No.2021PE0AC0)supported by the National Natural Science Foundation of China(NSFC,Nos.11988101 and 11833009)the Key Research Program of the Chinese Academy of Sciences(Grant No.QYZDJ-SSWSLH021)supported by the Cultivation Project for the FAST scientific Payoff and Research Achievement of CAMS-CAS。
文摘We report the properties of more than 800 bursts detected from the repeating fast radio burst(FRB)source FRB 20201124A with the Five-hundred-meter Aperture Spherical radio Telescope during an extremely active episode on UTC 2021 September 25th-28th in a series of four papers.In this fourth paper of the series,we present a systematic search of the spin period and linear acceleration of the source object from both 996 individual pulse peaks and the dedispersed time series.No credible spin period was found from this data set.We rule out the presence of significant periodicity in the range between 1 ms and 100 s with a pulse duty cycle<0.49±0.08(when the profile is defined by a von-Mises function,not a boxcar function)and linear acceleration up to 300 m s^(-2)in each of the four one-hour observing sessions,and up to 0.6 m s^(-2)in all 4 days.These searches contest theoretical scenarios involving a 1 ms–100 s isolated magnetar/pulsar with surface magnetic field<10^(15)G and a small duty cycle(such as in a polar-cap emission mode)or a pulsar with a companion star or black hole up to 100 M_(⊙)and P_(b)>10 hr.We also perform a periodicity search of the fine structures and identify 53 unrelated millisecond-timescale“periods”in multicomponents with the highest significance of 3.9σ.The“periods”recovered from the fine structures are neither consistent nor harmonically related.Thus they are not likely to come from a spin period.We caution against claiming spin periodicity with significance below~4σwith multi-components from one-off FRBs.We discuss the implications of our results and the possible connections between FRB multi-components and pulsar microstructures.
基金supported by the National Key R&D Program of China No.2019YFA0405500the National Natural Science Foundation of China(NSFC)with grant No.11835057+1 种基金Guo Shou Jing Telescope(the Large Sky Area Multi-Object Fiber Spectroscopic Telescope LAMOST)is a National Major Scientific Project built by the Chinese Academy of SciencesFunding for the project has been provided by the National Development and Reform Commission。
文摘An empirical stellar spectral library with large coverage of stellar parameters is essential for stellar population synthesis and studies of stellar evolution.In this work,we present Stellar Spectra Factory(SSF),a tool to generate empirical-based stellar spectra from arbitrary stellar atmospheric parameters.The relative flux-calibrated empirical spectra can be predicted by SSF given arbitrary effective temperature,surface gravity,and metallicity.SSF constructs the interpolation approach based on the Stellar LAbel Machine,using ATLAS-A library,which contains spectra covering from O type to M type,as the training data set.SSF is composed of four data-driven sub-models to predict empirical stellar spectra.Sub-model SSF-N can generate spectra from A to K type and some M giant stars,covering 3700<T_(eff)<8700 K,0<logg<dex,and-1.5<[M/H]<0.5 dex.Sub-model SSF-gM is mainly used to predict M giant spectra with 3520<T_(eff)<4000 K and-1.5<[M/H]<0.4 dex.Sub-model SSF-dM is for generating M dwarf spectra with 3295<T_(eff)<4040 K,-1.0<[M/H]<0.1 dex.Sub-model SSF-B can predict B-type spectra with 9000<T_(eff)<24,000 K and-5.2<M_(G)<1.5 mag.The accuracy of the predicted spectra is validated by comparing the flux of predicted spectra to those with same stellar parameters selected from the known spectral libraries,MILES and MaStar.The averaged difference of flux over optical wavelength between the predicted spectra and the corresponding ones in MILES and MaStar is less than 5%.More verification is conducted between the magnitudes calculated from the integration of the predicted spectra and the observations in PS1 and APASS bands with the same stellar parameters.No significant systematic difference is found between the predicted spectra and the photometric observations.The uncertainty is 0.08 mag in the r band for SSF-gM when comparing with the stars with the same stellar parameters selected from PS1.The uncertainty becomes 0.31 mag in the i band for SSF-dM when comparing with the stars with the same stellar parameters selected from APASS.
基金supported by the National SKA Program of China(Grant Nos.2020SKA0120200,and 2020SKA0120100)the CAS Project for Young Scientists in Basic Research(Grant No.YSBR-063)+5 种基金the National Natural Science Foundation of China(Grant Nos.12041303,11988101,11833009,11873067,12041304,and 12203045)the National Key R&D Program of China(Grant Nos.2017YFA0402600,2021YFA0718500,2017YFA04026022022YFC2205203)the CAS-MPG LEGACY Projectthe Max-Planck Partner Group,the Key Research Project of Zhejiang Lab(Grant No.2021PE0AC0)the Western Light Youth Project of Chinese Academy of Sciences。
文摘We present the interstellar scintillation analysis of fast radio burst(FRB)20220912A during its extremely active episode in 2022using data from the Five-hundred-meter Aperture Spherical Radio Telescope(FAST).We detect a scintillation arc in the FRB’s secondary spectrum,which describes the power in terms of the scattered FRB signals’time delay and Doppler shift.The arc indicates that the scintillation is caused by a highly localized region.Our analysis favors a Milky Way origin of the ionized interstellar medium(IISM)for the localized scattering medium but cannot rule out a host galaxy origin.We present our method for detecting the scintillation arc,which can be applied generally to sources with irregularly spaced bursts or pulses.These methods could help shed light on the complex interstellar environment surrounding the FRBs and in our Galaxy.
基金supported by the National Key R&D Program of China(Grant No.2021YFC2203001)support from Project funded by China Postdoctoral Science Foundation(Grant No.2023M730298)。
文摘Identifying strong lensing gravitational wave(SLGW)events is of utmost importance in astrophysics as we approach the historic first detection of SLGW amidst the growing number of gravitational wave(GW)events.Currently,one crucial method for identifying SLGW signals involves assessing the overlap of parameters between two GWs.However,the distribution of discrete matter,such as stars and sub-halos,within the strong lensing galaxy can imprint a wave optical(WO)effect on the SLGW waveform.These frequency dependent imprints introduce biases in parameter estimation and impact SLGW identification.In this study,we assess the influence of the stellar microlensing field embedded in a strong lensing galaxy.Our findings demonstrate that the WO effect reduces the detection efficiency of SLGW by 5%-50%for various false alarm probabilities per pair(FAPper pair).Specifically,at an FAPper pairof 10^(-5),the detection efficiency decreases from~10%to~5%.Consequently,the presence of the microlensing field can result in missing half of the strong lensing candidates.Additionally,the microlensing WO effect introduces a noticeable bias in intrinsic parameters,particularly for chirp mass and mass ratio.However,it has tiny influence on extrinsic parameters.Considering all parameters,~30%of events exhibit a 1σparameter bias,~12%exhibit a 2σparameter bias,and~5%exhibit a 3σparameter bias.
基金supported by the National Key R&D Program of China(Grant Nos.2021YFC2203001,and 2021YFC2203003)National Natural Science Foundation of China(Grant No.12247101)。
文摘For the stochastic gravitational wave backgrounds(SGWBs)search centred at the milli-Hz band,the galactic foreground produced by white dwarf binaries(WDBs)within the Milky Way contaminates the extra-galactic signal severely.Because of the anisotropic distribution pattern of the WDBs and the motion of the space-borne gravitational wave interferometer constellation,the time-domain data stream will show an annual modulation.This property is fundamentally diferent from those of the SGWBs.In this article,we propose a new filtering method for the data vector based on the annual modulation phenomenon.We apply the resulted inverse variance filter to the LISA Data Challenge.The result shows that for the weaker SGWB signal,such as energy density Ω_(astro)=1×10^(-12),the filtering method can enhance the posterior distribution peak prominently.For the stronger signal,such as Ω_(astro)=3×10^(-12),the method can improve the Bayesian evidence from“substantial”to“strong”against null hypotheses.This method is model-independent and self-contained.It does not ask for other types of information besides the gravitational wave data.