This study investigates the relationship between the detection rates of MgⅡabsorption lines and the asymmetries of[OⅢ]emission lines.We first select 21,364 quasars from the Sloan Digital Sky Survey DR12Q exhibiting ...This study investigates the relationship between the detection rates of MgⅡabsorption lines and the asymmetries of[OⅢ]emission lines.We first select 21,364 quasars from the Sloan Digital Sky Survey DR12Q exhibiting prominent[OⅢ]emission lines,of which 351 quasars have Category 1 MgⅡabsorption lines(4365≤υ_(r)≤10,000 km s^(-)1)and 518 quasars have Category 2 MgⅡabsorption lines(610≤υ_(r)≤4365 km s-1).Subsequently,we quantify the asymmetries of[OⅢ]emission lines using the velocity offsetδv,and find that the detection rates of Category 1 MgⅡabsorption lines(predominantly intervening absorbers)show no correlation with the blueshifted asymmetries of[OⅢ]emission lines,whereas the detection rates of Category 2 MgⅡabsorption lines(primarily outflow and intervening absorbers)increase with risingδ_(v).Finally,we discuss the results from two perspectives:quasar evolutionary stages and acceleration mechanisms driven by radiation pressure.展开更多
This paper explores the correlation between the fractional variation of the ionizing continuum and CⅣbroad absorption lines(BALs)with different ionization levels.Our results reveal anti-correlations between fractiona...This paper explores the correlation between the fractional variation of the ionizing continuum and CⅣbroad absorption lines(BALs)with different ionization levels.Our results reveal anti-correlations between fractional variation of the continuum and fractional equivalency width(EW)variation of the CⅣB ALs without AlⅢB AL/mini-BALs at corresponding velocities,providing evidence for the widespread influence of the ionizing continuum variability on the variation of HiBALs.Conversely,for CⅣBALs accompanied by AlⅢBAL/mini-BALs(LoBAL groups),no significant correction is detected.The absence of such a correlation does not rule out the possibility that variations in these low-ionization lines are caused by ionizing continuum variability,but rather suggests the influence of B AL saturation to some extent.This saturation effect is reflected in the distribution of the fractional EW variation,where the CⅣBAL group accompanied by AlⅢBAL has a smaller standard deviation for the best-fitting Gaussian component than the two BAL groups without AlⅢB AL.However,the distribution of fractional variation of their continuum does not show any significant difference.Besides the saturation influence,another potential explanation for the lack of correlations in the LoBAL groups may be the effects of other variability mechanisms besides the ionization change,such as clouds transiting across the line of sight.展开更多
The location ofγ-ray emission of blazars remains a contested topic,inspiring the development of numerous investigative techniques to address this issue.In this work,we analyzed Fermiγ-ray light curves in the GeV and...The location ofγ-ray emission of blazars remains a contested topic,inspiring the development of numerous investigative techniques to address this issue.In this work,we analyzed Fermiγ-ray light curves in the GeV and MeV bands,employing the discrete cross-correlation function method to discern time lags between the two bands.For 4C+21.35,Ton 599,B21420+32,and PKS 1510-089,we identified a time lag spanning several days,while for PKS 1441+25,the time lag was not statistically found.The results imply that the soft photons necessary for inverse Compton scattering predominantly originate from the dusty torus in the first four sources,whereas for PKS1441+25,they seem to be sourced mainly from the broad-line region.Further analysis of the opacity(τγγ)and the GeV spectra study supports the conclusion that the location of the dissipation region must be beyond the BLR to avoid significant absorption.Notably,for PKS 1441+25,the emission region is also posited to lie outside yet proximate to the BLR.The parameters of describing the emission region were obtained by fitting broadband spectral energy distribution with contemporaneous observation data.Our findings suggest that for the five TeV FSRQs,during Te V flaring events,the jet appears to maintain an equilibrium between the energy density of the magnetic field and that of the particles for all investigated sources,with the exceptions of 4C+21.35 and PKS1441+25.In terms of the overall jet power,particle energy is the dominant contributor,and the observed blazar radiation cannot be solely attributed to the magnetic field,except in the case of 4C+21.35.Consequently,magnetic reconnection is unlikely to be the primary mechanism behind particle acceleration in these systems.展开更多
We investigate the relationship between the variability of broad absorption lines(BALs)or narrow absorption lines(NALs)and that of continuum using a data set of two-epoch SDSS spectra containing 134 C IV NAL-BAL pairs...We investigate the relationship between the variability of broad absorption lines(BALs)or narrow absorption lines(NALs)and that of continuum using a data set of two-epoch SDSS spectra containing 134 C IV NAL-BAL pairs.Our analysis reveals an anti-correlation between the fractional equivalent width(EW)variations in NALs(or BALs)and the fractional flux variations of the continuum,with Spearman rank correlation coefficients of r=-0.47(p=1E-08)and r=-0.58(p=1E-13),respectively.In addition,we find a positive correlation between the fractional EW variations in NALs and BALs(r=0.72,p=1E-22),and derive a regression equation ΔEW_(NAL)/<EW_(NAL)>=0.803ΔEW_(BAL)/<EW_(BAL)>+0.008,with an intrinsic scatter of 0.14.These results suggest that the variability in the ionizing continuum may play a significant role in the observed changes in C IV NALs and BALs,supporting the idea of photoionization-driven variability.The co-variability between C IV NALs and BALs may imply that they originate from outflows with similar physical conditions.展开更多
Microquasars are the compact objects generally including accreting black holes which produce relativistic jets.The physical mechanisms of jet launching,collimation,and acceleration are poorly understood.Microquasars s...Microquasars are the compact objects generally including accreting black holes which produce relativistic jets.The physical mechanisms of jet launching,collimation,and acceleration are poorly understood.Microquasars show strong variability in multi-wavelength observations.In x-rays,the sources show the fast variation features down to millisecond time scales,with the prominent quasiperiodic oscillations(QPOs)around 0.1 Hz–tens of Hz in light curves,however,physical origin of QPOs is still uncertain.FAST as the largest radio telescope provides the opportunity to study fast variability of both radio flux and polarization in microquasars.In the FAST observations from 2020–2022,we reported the first evidence of radio subsecond quasi-periodic oscillations of GRS 1915+105,providing the direct link between QPOs and the dynamics of relativistic jets.These QPOs with the centroid frequency around 5 Hz are transient,accompanied with strong evolution of the spectral index.Combined with multiwavelength observations,we discuss the possible physical models to produce radio QPOs in BH systems:the helical motion of jet knots or precession of the jet base.In near future,high time resolution radio monitoring of microquasars based on FAST is expected to discover more new phenomena in black hole systems,which will be important for understanding the physics in strong gravity.展开更多
The[O iii]λλ4960,5008 emission lines in the optical spectra of galaxies and quasars have been widely used to investigate the possible variation of the fine-structure constantαover cosmic time.In this work,we utiliz...The[O iii]λλ4960,5008 emission lines in the optical spectra of galaxies and quasars have been widely used to investigate the possible variation of the fine-structure constantαover cosmic time.In this work,we utilize the Large Sky Area Multi-object Fiber Spectroscopic Telescope(LAMOST)quasar survey,for the first time,to measure the relativeαvariationΔα/αin time through the[O iii]doublet method.From the LAMOST Data Release 9 quasar catalog,we refine a sample of 209 quasar spectra with strong and narrow[O iii]emission lines over a redshift range of 0<z<0.8.Analysis on all of the 209 spectra obtainsΔα/α=(0.5±3.7)×10^(−4),which suggests that there is no evidence of varyingαon the explored cosmological timescales.Assuming a linear variation,the mean rate of change inΔα/αis limited to be(−3.4±2.4)×10^(−13)yr^(−1)in the last 7.0 Gyr.While our LAMOST-based constraint on Δα/α is not competitive with those of the Sloan Digital Sky Survey(SDSS)quasar observations,our analysis serves to corroborate the results of SDSS with another independent survey.展开更多
基金supported by the Scientific Research Project of Guangxi Minzu University(2023KJQD07)Guangxi Natural Science Foundation(2025GXNSFBA069287)+2 种基金the Guangxi Natural Science Foundation(2024GXNSFDA010069,2019GXNSFFA245008)the National Natural Science Foundation of China(12073007)the Scientific Research Project of Guangxi University for Nationalities(2018KJQD01)。
文摘This study investigates the relationship between the detection rates of MgⅡabsorption lines and the asymmetries of[OⅢ]emission lines.We first select 21,364 quasars from the Sloan Digital Sky Survey DR12Q exhibiting prominent[OⅢ]emission lines,of which 351 quasars have Category 1 MgⅡabsorption lines(4365≤υ_(r)≤10,000 km s^(-)1)and 518 quasars have Category 2 MgⅡabsorption lines(610≤υ_(r)≤4365 km s-1).Subsequently,we quantify the asymmetries of[OⅢ]emission lines using the velocity offsetδv,and find that the detection rates of Category 1 MgⅡabsorption lines(predominantly intervening absorbers)show no correlation with the blueshifted asymmetries of[OⅢ]emission lines,whereas the detection rates of Category 2 MgⅡabsorption lines(primarily outflow and intervening absorbers)increase with risingδ_(v).Finally,we discuss the results from two perspectives:quasar evolutionary stages and acceleration mechanisms driven by radiation pressure.
基金supported by the Guangxi Natural Science Foundation(No.2021GXNSFBA220044)the National Natural Science Foundation of China(No.11903002)the Research Project of Baise University(No.2019KN04)。
文摘This paper explores the correlation between the fractional variation of the ionizing continuum and CⅣbroad absorption lines(BALs)with different ionization levels.Our results reveal anti-correlations between fractional variation of the continuum and fractional equivalency width(EW)variation of the CⅣB ALs without AlⅢB AL/mini-BALs at corresponding velocities,providing evidence for the widespread influence of the ionizing continuum variability on the variation of HiBALs.Conversely,for CⅣBALs accompanied by AlⅢBAL/mini-BALs(LoBAL groups),no significant correction is detected.The absence of such a correlation does not rule out the possibility that variations in these low-ionization lines are caused by ionizing continuum variability,but rather suggests the influence of B AL saturation to some extent.This saturation effect is reflected in the distribution of the fractional EW variation,where the CⅣBAL group accompanied by AlⅢBAL has a smaller standard deviation for the best-fitting Gaussian component than the two BAL groups without AlⅢB AL.However,the distribution of fractional variation of their continuum does not show any significant difference.Besides the saturation influence,another potential explanation for the lack of correlations in the LoBAL groups may be the effects of other variability mechanisms besides the ionization change,such as clouds transiting across the line of sight.
基金support from the National Natural Science Foundation of China(NSFC,Grant No.12203034)from the Shanghai Science and Technology Fund under grant No.22YF1431500+11 种基金from the science research grants from the China Manned Space Projectsupport from the National Natural Science Foundation of China(NSFC,grant No.12203043)support from the National Natural Science Foundation of China(NSFC,grant No.11933002)support from the National Natural Science Foundation of China(NSFC,grant No.12173026)the National Key Research and Development Program of China(grant No.2022YFC2807303)the Shanghai Science and Technology Fund(grant No.23010503900)the Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learningthe Shuguang Program(23SG39)of the Shanghai Education Development Foundation and Shanghai Municipal Education Commissionsupport from the National Natural Science Foundation of China(NSFC,grant No.U2031201,and 11733001)the Scientific and Technological Cooperation Projects(20202023)between the People’s Republic of China and the Republic of Bulgariathe science research grants from the China Manned Space Project with No.CMS-CSST-2021A06partially supported by the Bulgarian National Science Fund of the Ministry of Education and Science under grants KP-06-H38/4(2019),KP-06-KITAJ/2(2020),and KP-06-H68/4(2022)。
文摘The location ofγ-ray emission of blazars remains a contested topic,inspiring the development of numerous investigative techniques to address this issue.In this work,we analyzed Fermiγ-ray light curves in the GeV and MeV bands,employing the discrete cross-correlation function method to discern time lags between the two bands.For 4C+21.35,Ton 599,B21420+32,and PKS 1510-089,we identified a time lag spanning several days,while for PKS 1441+25,the time lag was not statistically found.The results imply that the soft photons necessary for inverse Compton scattering predominantly originate from the dusty torus in the first four sources,whereas for PKS1441+25,they seem to be sourced mainly from the broad-line region.Further analysis of the opacity(τγγ)and the GeV spectra study supports the conclusion that the location of the dissipation region must be beyond the BLR to avoid significant absorption.Notably,for PKS 1441+25,the emission region is also posited to lie outside yet proximate to the BLR.The parameters of describing the emission region were obtained by fitting broadband spectral energy distribution with contemporaneous observation data.Our findings suggest that for the five TeV FSRQs,during Te V flaring events,the jet appears to maintain an equilibrium between the energy density of the magnetic field and that of the particles for all investigated sources,with the exceptions of 4C+21.35 and PKS1441+25.In terms of the overall jet power,particle energy is the dominant contributor,and the observed blazar radiation cannot be solely attributed to the magnetic field,except in the case of 4C+21.35.Consequently,magnetic reconnection is unlikely to be the primary mechanism behind particle acceleration in these systems.
基金supported by the Guangxi Natural Science Foundation(No.2021GXNSFBA220044)the National Natural Science Foundation of China(No.11903002)the Research Project of Baise University(No.2019KN04)。
文摘We investigate the relationship between the variability of broad absorption lines(BALs)or narrow absorption lines(NALs)and that of continuum using a data set of two-epoch SDSS spectra containing 134 C IV NAL-BAL pairs.Our analysis reveals an anti-correlation between the fractional equivalent width(EW)variations in NALs(or BALs)and the fractional flux variations of the continuum,with Spearman rank correlation coefficients of r=-0.47(p=1E-08)and r=-0.58(p=1E-13),respectively.In addition,we find a positive correlation between the fractional EW variations in NALs and BALs(r=0.72,p=1E-22),and derive a regression equation ΔEW_(NAL)/<EW_(NAL)>=0.803ΔEW_(BAL)/<EW_(BAL)>+0.008,with an intrinsic scatter of 0.14.These results suggest that the variability in the ionizing continuum may play a significant role in the observed changes in C IV NALs and BALs,supporting the idea of photoionization-driven variability.The co-variability between C IV NALs and BALs may imply that they originate from outflows with similar physical conditions.
基金supported by the National Natural Science Foundation of China(Grant No.12133007)the National Key Research and Development Program of China(Grant Nos.2021YFA0718503 and 2023YFA1607901)the Cultivation Project for FAST Scientific Payoff and Research Achievement of CAMS-CAS。
文摘Microquasars are the compact objects generally including accreting black holes which produce relativistic jets.The physical mechanisms of jet launching,collimation,and acceleration are poorly understood.Microquasars show strong variability in multi-wavelength observations.In x-rays,the sources show the fast variation features down to millisecond time scales,with the prominent quasiperiodic oscillations(QPOs)around 0.1 Hz–tens of Hz in light curves,however,physical origin of QPOs is still uncertain.FAST as the largest radio telescope provides the opportunity to study fast variability of both radio flux and polarization in microquasars.In the FAST observations from 2020–2022,we reported the first evidence of radio subsecond quasi-periodic oscillations of GRS 1915+105,providing the direct link between QPOs and the dynamics of relativistic jets.These QPOs with the centroid frequency around 5 Hz are transient,accompanied with strong evolution of the spectral index.Combined with multiwavelength observations,we discuss the possible physical models to produce radio QPOs in BH systems:the helical motion of jet knots or precession of the jet base.In near future,high time resolution radio monitoring of microquasars based on FAST is expected to discover more new phenomena in black hole systems,which will be important for understanding the physics in strong gravity.
基金supported by the National Natural Science Foundation of China(grant Nos.12422307,12373053,and 12321003)the Key Research Program of Frontier Sciences(grant No.ZDBS-LY-7014)+1 种基金Chinese Academy of Sciences,and the Natural Science Foundation of Jiangsu Province(grant No.BK20221562)supported by the Chinese Academy of Sciences President's International Fellowship Initiative(grant No.2023VMB0001)。
文摘The[O iii]λλ4960,5008 emission lines in the optical spectra of galaxies and quasars have been widely used to investigate the possible variation of the fine-structure constantαover cosmic time.In this work,we utilize the Large Sky Area Multi-object Fiber Spectroscopic Telescope(LAMOST)quasar survey,for the first time,to measure the relativeαvariationΔα/αin time through the[O iii]doublet method.From the LAMOST Data Release 9 quasar catalog,we refine a sample of 209 quasar spectra with strong and narrow[O iii]emission lines over a redshift range of 0<z<0.8.Analysis on all of the 209 spectra obtainsΔα/α=(0.5±3.7)×10^(−4),which suggests that there is no evidence of varyingαon the explored cosmological timescales.Assuming a linear variation,the mean rate of change inΔα/αis limited to be(−3.4±2.4)×10^(−13)yr^(−1)in the last 7.0 Gyr.While our LAMOST-based constraint on Δα/α is not competitive with those of the Sloan Digital Sky Survey(SDSS)quasar observations,our analysis serves to corroborate the results of SDSS with another independent survey.
