We present radial velocity(RV)curve templates of RR Lyrae first-overtone(RRc)stars constructed with the Mg I b triplet and Hαlines using time-domain Medium-Resolution Survey spectra of seven RRc stars from Large Sky ...We present radial velocity(RV)curve templates of RR Lyrae first-overtone(RRc)stars constructed with the Mg I b triplet and Hαlines using time-domain Medium-Resolution Survey spectra of seven RRc stars from Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST)Data Release 9.Additionally,we derive the relation between the stellar RV curve amplitudes and g-band light curve amplitudes from Zwicky Transient Facility(ZTF)public survey.For those RRc stars without ZTF g-band light curves,we provide the conversions from the light curve amplitudes in ZTF r-and i-bands,Gaia G-band,and V-band from the All-Sky Automated Survey for Supernovae to those in ZTF g-band.We validate our RV curve templates using the RRc star SV Scl and find the uncertainties of systemic RV are less than 2.11 km s~(-1)and 6.08 km s~(-1)based on the Mg I b triplet and Hαlines,respectively.We calculate the systemic RVs of 30 RRc stars using the RV curve templates constructed with the Mg I b triplet and Hαlines and find the systemic RVs are comparable with each other.This RV curve template will be particularly useful for obtaining the systemic RV of RRc using the LAMOST spectroscopy.展开更多
The Van Hoof effect is a phase shift existing between the radial velocity curves of hydrogen and metallic lines within the atmosphere of pulsating stars.In this article,we present a study of this phenomenon through th...The Van Hoof effect is a phase shift existing between the radial velocity curves of hydrogen and metallic lines within the atmosphere of pulsating stars.In this article,we present a study of this phenomenon through the spectra of the brightest pulsating star RR Lyr of RR Lyrae stars recorded for 22 yr.We based ourselves,on the one hand,on 1268 spectra(41 nights of observation)recorded between the years 1994 and 1997 at the Observatory of Haute Provence(OHP,France)previously observed by Chadid and Gillet,and on the other hand on 1569 spectra(46nights of observation)recorded at our Oukaimeden Observatory(Morocco)between 2015 and 2016.Through this study,we have detected information on atmospheric dynamics that had not previously been detected.Indeed,the Van Hoof effect which results in a clear correlation between the radial velocities of hydrogen and those of the metallic lines has been observed and analyzed at different Blazhko phases.A correlation between the radial velocities of different metallic lines located in the lower atmosphere has been observed as well.For the first time,we were able to show that the amplitude of the radial velocity curves deduced from the lines of hydrogen and that of FeⅡ(λ4923.921?)increases toward the minimum of the Blazhko cycle and decreases toward the maximum of the same Blazhko cycle.Furthermore,we found that the Van Hoof effect is also modulated by the Blazhko effect.Thus,toward the minimum of the Blazhko cycle the Van Hoof effect is more visible and at the maximum of the Blazhko cycle,this effect is minimal.We also observed the temporal evolution of the amplitudes of the radial velocities of the lower and upper atmosphere.When observed over a long time,we can interpret it as a function of the Blazhko phases.展开更多
With the rapid development of the Internet,people pay more and more attention to the protection of privacy.The second-generation onion routing system Tor is the most commonly used among anonymous communication systems...With the rapid development of the Internet,people pay more and more attention to the protection of privacy.The second-generation onion routing system Tor is the most commonly used among anonymous communication systems,which can be used to protect user privacy effectively.In recent years,Tor’s congestion problem has become the focus of attention,and it can affect Tor’s performance even user experience.Firstly,we investigate the causes of Tor network congestion and summarize some link scheduling algorithms proposed in recent years.Then we propose the link scheduling algorithm SWRR based on WRR(Weighted Round Robin).In this process,we design multiple weight functions and compare the performance of these weight functions under different congestion conditions,and the appropriate weight function is selected to be used in our algorithms based on the experiment results.Finally,we also compare the performance of SWRR with other link scheduling algorithms under different congestion conditions by experiments,and verify the effectiveness of the algorithm SWRR.展开更多
基金supported by the National Key Research and Development Program of China(2023YFA1608100)the National Natural Science Foundation of China(NSFC,grant Nos.12090044,11833006 and 12303023)+3 种基金the science research grants from the China Manned Space Project including the CSST Milky Way and Nearby Galaxies Survey on Dust and Extinction Project CMS-CSST-2021-A09 and No.CMS-CSST-2021-A08.G.C.LHubei Provincial Natural Science Foundation with grant No.2023AFB577the Key Laboratory Fund of Ministry of Education under grant No.QLPL2022P01National Natural Science Foundation of China(NSFC,Grant No.U1731108)。
文摘We present radial velocity(RV)curve templates of RR Lyrae first-overtone(RRc)stars constructed with the Mg I b triplet and Hαlines using time-domain Medium-Resolution Survey spectra of seven RRc stars from Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST)Data Release 9.Additionally,we derive the relation between the stellar RV curve amplitudes and g-band light curve amplitudes from Zwicky Transient Facility(ZTF)public survey.For those RRc stars without ZTF g-band light curves,we provide the conversions from the light curve amplitudes in ZTF r-and i-bands,Gaia G-band,and V-band from the All-Sky Automated Survey for Supernovae to those in ZTF g-band.We validate our RV curve templates using the RRc star SV Scl and find the uncertainties of systemic RV are less than 2.11 km s~(-1)and 6.08 km s~(-1)based on the Mg I b triplet and Hαlines,respectively.We calculate the systemic RVs of 30 RRc stars using the RV curve templates constructed with the Mg I b triplet and Hαlines and find the systemic RVs are comparable with each other.This RV curve template will be particularly useful for obtaining the systemic RV of RRc using the LAMOST spectroscopy.
文摘The Van Hoof effect is a phase shift existing between the radial velocity curves of hydrogen and metallic lines within the atmosphere of pulsating stars.In this article,we present a study of this phenomenon through the spectra of the brightest pulsating star RR Lyr of RR Lyrae stars recorded for 22 yr.We based ourselves,on the one hand,on 1268 spectra(41 nights of observation)recorded between the years 1994 and 1997 at the Observatory of Haute Provence(OHP,France)previously observed by Chadid and Gillet,and on the other hand on 1569 spectra(46nights of observation)recorded at our Oukaimeden Observatory(Morocco)between 2015 and 2016.Through this study,we have detected information on atmospheric dynamics that had not previously been detected.Indeed,the Van Hoof effect which results in a clear correlation between the radial velocities of hydrogen and those of the metallic lines has been observed and analyzed at different Blazhko phases.A correlation between the radial velocities of different metallic lines located in the lower atmosphere has been observed as well.For the first time,we were able to show that the amplitude of the radial velocity curves deduced from the lines of hydrogen and that of FeⅡ(λ4923.921?)increases toward the minimum of the Blazhko cycle and decreases toward the maximum of the same Blazhko cycle.Furthermore,we found that the Van Hoof effect is also modulated by the Blazhko effect.Thus,toward the minimum of the Blazhko cycle the Van Hoof effect is more visible and at the maximum of the Blazhko cycle,this effect is minimal.We also observed the temporal evolution of the amplitudes of the radial velocities of the lower and upper atmosphere.When observed over a long time,we can interpret it as a function of the Blazhko phases.
基金This work is supported by the National Natural Science Foundation of China(Grant No.61170273,No.U1536111)and the China Scholarship Council(No.[2013]3050).In addition,we express our sincere gratitude to Lingling Gong,Meng Luo,Zhimin Lin,Peiyuan Li and the anonymous reviewers for their valuable comments and suggestions.
文摘With the rapid development of the Internet,people pay more and more attention to the protection of privacy.The second-generation onion routing system Tor is the most commonly used among anonymous communication systems,which can be used to protect user privacy effectively.In recent years,Tor’s congestion problem has become the focus of attention,and it can affect Tor’s performance even user experience.Firstly,we investigate the causes of Tor network congestion and summarize some link scheduling algorithms proposed in recent years.Then we propose the link scheduling algorithm SWRR based on WRR(Weighted Round Robin).In this process,we design multiple weight functions and compare the performance of these weight functions under different congestion conditions,and the appropriate weight function is selected to be used in our algorithms based on the experiment results.Finally,we also compare the performance of SWRR with other link scheduling algorithms under different congestion conditions by experiments,and verify the effectiveness of the algorithm SWRR.
