We analyze the optical light curve data,obtained with the Zwicky Transient Facility(ZTF)survey,for 47 γ-ray blazars monitored by the Large Area Telescope onboard the Fermi Gamma-ray Space Telescope(Fermi).These 47sou...We analyze the optical light curve data,obtained with the Zwicky Transient Facility(ZTF)survey,for 47 γ-ray blazars monitored by the Large Area Telescope onboard the Fermi Gamma-ray Space Telescope(Fermi).These 47sources are selected because they are among the Fermi blazars with the largest optical variations in the ZTF data.Two color-magnitude variation patterns are seen in them,with one being redder-to-stable-when-brighter(RSWB;in 31 sources)and the other being stable when brighter(in 16 sources).The patterns fit with the results recently reported in several similar studies with different data.Moreover,we find that the colors in the stable state of the sources share similar values,for which(after being corrected for the Galactic extinction)most sources are in a range of 0.4–0.55.This feature could be intrinsic and may be applied in,for example,study of the intragalactic medium.We also determine the turning points for the sources showing the RSWB pattern,after which the color changes saturate and become stable.We find a correlation between optical fluxes and γ-ray fluxes at the turning points.The physical implications of the correlation remain to be investigated,probably better with a sample of high-qualityγ-ray flux measurements.展开更多
A warm corona has been widely proposed to explain the soft excess(SE)in X-ray above the 2-10 ke V power law extrapolation in Active Galactic Nuclei(AGNs).In actual spectral fittings,the warm coronal seed photon temper...A warm corona has been widely proposed to explain the soft excess(SE)in X-ray above the 2-10 ke V power law extrapolation in Active Galactic Nuclei(AGNs).In actual spectral fittings,the warm coronal seed photon temperature(T_s)is usually assumed to be far away from the soft X-ray,but kT_scan reach close to 0.1 ke V in the standard accretion disk model.In this study,we used Monte Carlo simulations to obtain radiation spectra from a slab-like warm corona and fitted the spectra using the spherical-geometry-based routine THCOMP or a thermal component.Our findings reveal tha high T_scan influence the fitting results.A moderately high kT_s(around 0.03 ke V)can result in an apparent low-temperature and flat SE,while an extremely high kT_s(around 0.07 ke V)can even produce an unobserved blackbody-like SE.Our conclusions indicate that,for spectral fittings of the warm coronal radiation(SE in AGNs),kT_sshould be treated as a free parameter with an upper limit,and an accurate coronal geometry is necessary when kT_s>0.01 ke V.展开更多
A Very High-energy(VHE) flare was observed by Major Atmospheric Gamma Imaging Cherenkov Telescopes on MJD 57788. This VHE flare was characterized by increased VHE flux and short timescales. In this study, we used one-...A Very High-energy(VHE) flare was observed by Major Atmospheric Gamma Imaging Cherenkov Telescopes on MJD 57788. This VHE flare was characterized by increased VHE flux and short timescales. In this study, we used one-zone synchrotron self-Compton, two-zone, and spine/layer models to explore this VHE flare's origin. The results indicate that this γ-ray flare can be explained by Inverse Compton Scattering radiation from the layer contributed gamma radiation and results in the γ-ray flare in a different way than the two-zone model. The difference between the two models lies in the performance of spectral energy distribution after γ-ray flare as well as a possible difference in the timescales of the flare.展开更多
With its high duty cycle, wide field of view and high detection sensitivity, Water Chereknov Detector Array as one of sub-arrays of Large High Altitude Air Shower Observatory is a promising facility to monitor transie...With its high duty cycle, wide field of view and high detection sensitivity, Water Chereknov Detector Array as one of sub-arrays of Large High Altitude Air Shower Observatory is a promising facility to monitor transient phenomena in the very high energy gamma-ray band. In this work, a real-time monitor for selected TeV extragalactic sources is introduced, this flare monitor is developed to detect very high energy flare events and for further studying the power-providing mechanism of blazar relativistic jets. The detailed information such as the searching method and sensitivity of this real-time flare monitor is also presented. In the end, successful multiwavelength and multi-messenger observation of 1ES 1959+650 and IC 310 also confirms the capabilities and reliability of the monitoring system.展开更多
基金supported by the National Science Foundation under Grant No.AST-2034437 and a collaboration including Caltech,IPACsupported by the Basic Research Program of Yunnan Province(No.202201AS070005)+2 种基金the National Natural Science Foundation of China(NSFC,grant No.12273033)the Original Innovation Program of the Chinese Academy of Sciences(E085021002)the support of the science research program for graduate students of Yunnan University(KC-23234629)。
文摘We analyze the optical light curve data,obtained with the Zwicky Transient Facility(ZTF)survey,for 47 γ-ray blazars monitored by the Large Area Telescope onboard the Fermi Gamma-ray Space Telescope(Fermi).These 47sources are selected because they are among the Fermi blazars with the largest optical variations in the ZTF data.Two color-magnitude variation patterns are seen in them,with one being redder-to-stable-when-brighter(RSWB;in 31 sources)and the other being stable when brighter(in 16 sources).The patterns fit with the results recently reported in several similar studies with different data.Moreover,we find that the colors in the stable state of the sources share similar values,for which(after being corrected for the Galactic extinction)most sources are in a range of 0.4–0.55.This feature could be intrinsic and may be applied in,for example,study of the intragalactic medium.We also determine the turning points for the sources showing the RSWB pattern,after which the color changes saturate and become stable.We find a correlation between optical fluxes and γ-ray fluxes at the turning points.The physical implications of the correlation remain to be investigated,probably better with a sample of high-qualityγ-ray flux measurements.
基金partially supported by the National Natural Science Foundation of China(NSFC,grant Nos.U2031201 and11733001)the Natural Science Foundation of Guangdong Province(2019B030302001)+3 种基金the science research grants from the China Manned Space Project,with No.CMS-CSST-2021-A06support from Astrophysics Key Subjects of Guangdong Province and Guangzhou Citysupport from Scientific and Technological Cooperation Projects(2020-2023)between the People’s Republic of China and the Republic of Bulgariasupport that was received from Guangzhou University(No.YM2020001)。
文摘A warm corona has been widely proposed to explain the soft excess(SE)in X-ray above the 2-10 ke V power law extrapolation in Active Galactic Nuclei(AGNs).In actual spectral fittings,the warm coronal seed photon temperature(T_s)is usually assumed to be far away from the soft X-ray,but kT_scan reach close to 0.1 ke V in the standard accretion disk model.In this study,we used Monte Carlo simulations to obtain radiation spectra from a slab-like warm corona and fitted the spectra using the spherical-geometry-based routine THCOMP or a thermal component.Our findings reveal tha high T_scan influence the fitting results.A moderately high kT_s(around 0.03 ke V)can result in an apparent low-temperature and flat SE,while an extremely high kT_s(around 0.07 ke V)can even produce an unobserved blackbody-like SE.Our conclusions indicate that,for spectral fittings of the warm coronal radiation(SE in AGNs),kT_sshould be treated as a free parameter with an upper limit,and an accurate coronal geometry is necessary when kT_s>0.01 ke V.
基金partially supported by the National Natural Science Foundation of China (NSFC, grant Nos. 12433004, U2031201, and 11733001)Guangdong Major Project of Basic and Applied Basic Research (grant No. 2019B030302001)+2 种基金the science research grants from the China Manned Space Project with No. CMS-CSST-2021-A06the support for Astrophysics Key Subjects of Guangdong Province and Guangzhou CityThe Key Laboratory for Astronomical Observation and Technology of Guangzhou also supports the work。
文摘A Very High-energy(VHE) flare was observed by Major Atmospheric Gamma Imaging Cherenkov Telescopes on MJD 57788. This VHE flare was characterized by increased VHE flux and short timescales. In this study, we used one-zone synchrotron self-Compton, two-zone, and spine/layer models to explore this VHE flare's origin. The results indicate that this γ-ray flare can be explained by Inverse Compton Scattering radiation from the layer contributed gamma radiation and results in the γ-ray flare in a different way than the two-zone model. The difference between the two models lies in the performance of spectral energy distribution after γ-ray flare as well as a possible difference in the timescales of the flare.
基金supported in China by NSFC grant No.12393853the Department of Science and Technology of Sichuan Province China with grant No.24NSFSC0449NSFC grant No.U2031205。
文摘With its high duty cycle, wide field of view and high detection sensitivity, Water Chereknov Detector Array as one of sub-arrays of Large High Altitude Air Shower Observatory is a promising facility to monitor transient phenomena in the very high energy gamma-ray band. In this work, a real-time monitor for selected TeV extragalactic sources is introduced, this flare monitor is developed to detect very high energy flare events and for further studying the power-providing mechanism of blazar relativistic jets. The detailed information such as the searching method and sensitivity of this real-time flare monitor is also presented. In the end, successful multiwavelength and multi-messenger observation of 1ES 1959+650 and IC 310 also confirms the capabilities and reliability of the monitoring system.
