The clarity of nights is the major factor that should be carefully considered for optical/infrared astronomical observatories in site-testing campaigns.Cloud coverage is directly related to the amount of time availabl...The clarity of nights is the major factor that should be carefully considered for optical/infrared astronomical observatories in site-testing campaigns.Cloud coverage is directly related to the amount of time available for scientific observations at observatories.In this article,we report on the results of detailed night-time cloud statistics and continuous observing time derived from ground-based all-sky cameras(ASCs)at the Muztagh-ata site from 2017to 2021.Results obtained from acquisition data show that the proportion of the annual observing time at the Muztagh-ata site is 65%,and the best period with the least cloud coverage and longer continuous observing time is from September to February.We made a comparison of the monthly mean observing nights obtained from our ASC and CLARA data set,and results show that the discrepancy between them may depend on the cloud top heights.On average,this site can provide 175 clear nights and 169 nights with at least 4 hr of continuous observing time per year.展开更多
The 85-cm telescope at Xinglong station is a prime focus system that operates well with high science outputs. The telescope has been upgraded since 2014 with a new corrector, and new filters and camera, which are prov...The 85-cm telescope at Xinglong station is a prime focus system that operates well with high science outputs. The telescope has been upgraded since 2014 with a new corrector, and new filters and camera, which are provided by Beijing Normal University. The filter set is the Johnson-Cousins UBV RI system. We report the test results of the new system including bias, dark current, linearity, gain and readout noise of the CCD camera. Then we derive accurate instrumental calibration coefficients in UBV RI bands with Landolt standard stars during photometric nights. Finally, we give the limiting magnitudes with various exposure times and signal-to-noise ratios for observers as references.展开更多
Site-testing is crucial for achieving the goal of scientific research and analysis of meteorological and optical observing conditions,one of the associated basic tasks.As one of three potential sites to host the 12-me...Site-testing is crucial for achieving the goal of scientific research and analysis of meteorological and optical observing conditions,one of the associated basic tasks.As one of three potential sites to host the 12-meter Large Optical/infrared Telescope(LOT),the Muztagh-ata site,which is located on the Pamir Plateau in Xinjiang,in west China,began its site-testing task in the spring of 2017.In this paper,we firstly start with an introduction to the site and then present a statistical analysis of the ground-level meteorological properties such as air temperature,barometric pressure,relative humidity,and wind speed and direction,recorded by an automatic weather station with standard meteorological sensors for a two-year duration.We also show the monitoring results of sky brightness during this period.展开更多
In this article,we present detailed seasonal,monthly and daily statistics of temperature difference in the surface layer at the Muztagh-ata site based on the temperature measurements at two heights of 2 m and6 m.We fi...In this article,we present detailed seasonal,monthly and daily statistics of temperature difference in the surface layer at the Muztagh-ata site based on the temperature measurements at two heights of 2 m and6 m.We find that temperature inversion occurs frequently at our site during nighttime,especially during the cold season.Strong temperature inversion always represents stable atmospheric turbulence,which is crucial for an optical observatory.By analyzing the behavior of temperature inversion and its correlation with wind and cloud amount,one conclusion can be made that radiation inversion is the main reason for the existence of temperature inversion in the surface-layer at the Muztagh-ata site.展开更多
The Large Optical/infrared Telescope(LOT)is a ground-based 12 m diameter optical/infrared telescope which is proposed to be built in the western part of China in the next decade.Based on satellite remote sensing data,...The Large Optical/infrared Telescope(LOT)is a ground-based 12 m diameter optical/infrared telescope which is proposed to be built in the western part of China in the next decade.Based on satellite remote sensing data,along with geographical,logistical and political considerations,three candidate sites were chosen for ground-based astronomical performance monitoring.These sites include:Ali in Tibet,Daocheng in Sichuan and Muztagh-ata in Xinjiang.Up until now,all three sites have continuously collected data for two years.In this paper,we will introduce this site testing campaign,and present its monitoring results obtained during the period between March 2017 and March 2019.展开更多
The Nanshan One-meter Wide-field Telescope is a prime focus system that is located at Nanshan Station of Xinjiang Astronomical Observatories.The field of view was designed to 1.5°× 1.5°,and the Johnson-...The Nanshan One-meter Wide-field Telescope is a prime focus system that is located at Nanshan Station of Xinjiang Astronomical Observatories.The field of view was designed to 1.5°× 1.5°,and the Johnson-Cousins UBVRI system was chosen as the main filter set.The telescope has been providing observation services for astronomers since September 2013.Variable source searching and time-domain surveys are the main scientific goals.The system’s test results are reported including linearity,dark current,bias,readout noise and gain of the CCD camera.The accurate instrumental calibration coefficients in UBVRI bands were driven with Landolt standard stars during photometric nights.Finally,the limiting magnitudes are given with signal-to-noise ratios and various exposure times for observers.展开更多
In this article,we present a detailed analysis of the statistical properties of seeing for the Muztaghata site which is a candidate site for hosting the future Chinese Large Optical/infrared Telescope(LOT)project.The ...In this article,we present a detailed analysis of the statistical properties of seeing for the Muztaghata site which is a candidate site for hosting the future Chinese Large Optical/infrared Telescope(LOT)project.The measurements were obtained with differential image motion monitors(DIMMs)from April2017 to November 2018 at different heights during different periods.The median seeings at 11 m and6 m are very close but significantly different from that on the ground.We mainly analyzed the seeing at11 m monthly and hourly,having found that the best season for observing was from late autumn to early winter and seeing tended to improve during the night only in autumn.The analysis of the dependence on temperature inversion,wind speed and direction also was made and the best meteorological conditions for seeing are given.展开更多
A large ground-based optical/infrared telescope is being planned for a world-class astronomical site in China.The cloud-free night percentage is the primary meteorological consideration for evaluating candidate sites....A large ground-based optical/infrared telescope is being planned for a world-class astronomical site in China.The cloud-free night percentage is the primary meteorological consideration for evaluating candidate sites.The data from GMS and NOAA satellites and the MODIS instrument were utilized in this research,covering the period from 1996 to 2015.Our data analysis benefits from overlapping results from different independent teams as well as a uniform analysis of selected sites using GMS+NOAA data.Although significant ground-based monitoring is needed to validate these findings,we identify three different geographical regions with a high percentage of cloud-free conditions(~83%on average),which is slightly lower than at Mauna Kea and Cerro Armazones(~85%on average)and were chosen for the large international projects TMT and ELT respectively.Our study finds evidence that cloud distributions and the seasonal changes affected by the prevailing westerly winds and summer monsoons reduce the cloud cover in areas influenced by the westerlies.This is consistent with the expectations from climate change models and is suggestive that most of the identified sites will have reduced cloud cover in the future.展开更多
Based on previous site testing and satellite cloud data,Ali,Daocheng and Muztagh-ata have been selected as candidate sites for the Large Optical/Infrared Telescope(LOT) in China.We present the data collection,processi...Based on previous site testing and satellite cloud data,Ali,Daocheng and Muztagh-ata have been selected as candidate sites for the Large Optical/Infrared Telescope(LOT) in China.We present the data collection,processing,management and quality analysis for our site testing based on using similar hardware.We analyze meteorological data,seeing,background light,cloud and precipitable water vapor data from 2017 March 10 to 2019 March 10.We also investigated the relative usefulness of our all-sky camera data in comparison to that from the meteorological TERRA satellite data based on a night-by-night comparison of the correlation and consistency between them.We find a 6% discrepancy arising from a wide range of factors.展开更多
KIC 10417986 is a short orbital period(0.0737 day)ellipsoidal variable star with aδSct andγDor hybrid pulsation component discovered by Kepler.The ground-based spectroscopic observations were carried out in the wint...KIC 10417986 is a short orbital period(0.0737 day)ellipsoidal variable star with aδSct andγDor hybrid pulsation component discovered by Kepler.The ground-based spectroscopic observations were carried out in the winters of 2020 and 2021 to investigate the binary nature of this star.We derive the orbital parameters using the rvfit code with a result of K_(1)=29.7±1.5 km s^(-1),γ=-18.7±1.7 km s^(-1),and confirm an orbital period of 0.84495 day instead of the result given by Kepler.The atmospheric parameters of the primary are determined by the synthetic spectral fitting technique with the estimated values of T_(eff)=7411±187 K,log g=4.2±0.3 dex,[M/H]=0.08±0.09 dex and vsini=52±11 km s^(-1).KIC 10417986 is a circular orbit binary system.From the single-lined nature and mass function of the star,the derived orbital inclination is 26°±6°,and the mass of the secondary is 0.52_(-0.09)^(+0.18)M_(⊙),which should be a late-K to early-M type star.Fourteen frequencies are extracted from Kepler light curves,of which six independent frequencies in the high-frequency region are identified as the p-mode pulsations ofδSct star,and one independent frequency in the low-frequency region(f_(2)=1.3033 cd^(-1))is probably the rotational frequency due to the starspots rather than the ellipsoidal effect.展开更多
基金supported by the Chinese Academy of Sciences (CAS) “Light of West China”Program (No.2022_XBQNXZ_014)the Xinjiang Natural Science Foundation (Grant No.2022D01A357)+2 种基金the Joint Research Fund in Astronomy under a cooperative agreement between the National Natural Science Foundation of China (NSFC)and the CAS (Grant No.U2031209)the NSFC (Grant Nos.11873081,11603065,and 12073047)resource sharing platform construction project of Xinjiang Uygur Autonomous Region (No.PT2306)。
文摘The clarity of nights is the major factor that should be carefully considered for optical/infrared astronomical observatories in site-testing campaigns.Cloud coverage is directly related to the amount of time available for scientific observations at observatories.In this article,we report on the results of detailed night-time cloud statistics and continuous observing time derived from ground-based all-sky cameras(ASCs)at the Muztagh-ata site from 2017to 2021.Results obtained from acquisition data show that the proportion of the annual observing time at the Muztagh-ata site is 65%,and the best period with the least cloud coverage and longer continuous observing time is from September to February.We made a comparison of the monthly mean observing nights obtained from our ASC and CLARA data set,and results show that the discrepancy between them may depend on the cloud top heights.On average,this site can provide 175 clear nights and 169 nights with at least 4 hr of continuous observing time per year.
基金support from the staff at the Xinglong 85-cm telescopesupport from the National Natural Science Foundation of China(NSFC)through grant 11673003+3 种基金the National Basic Research Program of China(973 program,2014CB845700)partially supported by the Open Project Program of the Key Laboratory of Optical Astronomy(National Astronomical Observatories)NSFC under Grant Nos.11403088 and 11273051(Xinjiang Astronomical Observatory)Chinese Academy of Sciences and Department of Astronomy,Beijing Normal University
文摘The 85-cm telescope at Xinglong station is a prime focus system that operates well with high science outputs. The telescope has been upgraded since 2014 with a new corrector, and new filters and camera, which are provided by Beijing Normal University. The filter set is the Johnson-Cousins UBV RI system. We report the test results of the new system including bias, dark current, linearity, gain and readout noise of the CCD camera. Then we derive accurate instrumental calibration coefficients in UBV RI bands with Landolt standard stars during photometric nights. Finally, we give the limiting magnitudes with various exposure times and signal-to-noise ratios for observers as references.
基金supported by the National Natural Science Foundation of China(Grant Nos.11873081 and 11603065)the Operation,Maintenance and Upgrading Fund for Astronomical Telescopes and Facility Instruments,budgeted from the Ministry of Finance of China and administered by the Chinese Academy of Sciences。
文摘Site-testing is crucial for achieving the goal of scientific research and analysis of meteorological and optical observing conditions,one of the associated basic tasks.As one of three potential sites to host the 12-meter Large Optical/infrared Telescope(LOT),the Muztagh-ata site,which is located on the Pamir Plateau in Xinjiang,in west China,began its site-testing task in the spring of 2017.In this paper,we firstly start with an introduction to the site and then present a statistical analysis of the ground-level meteorological properties such as air temperature,barometric pressure,relative humidity,and wind speed and direction,recorded by an automatic weather station with standard meteorological sensors for a two-year duration.We also show the monitoring results of sky brightness during this period.
基金supported by the National Natural Science Foundation of China(Grant Nos.11873081 and 11803076)the Operation,Maintenance and Upgrading Fund for Astronomical Telescopes and Facility Instruments,budgeted from the Ministry of Finance of China(MOF)and administered by the Chinese Academy of Sciences(CAS)。
文摘In this article,we present detailed seasonal,monthly and daily statistics of temperature difference in the surface layer at the Muztagh-ata site based on the temperature measurements at two heights of 2 m and6 m.We find that temperature inversion occurs frequently at our site during nighttime,especially during the cold season.Strong temperature inversion always represents stable atmospheric turbulence,which is crucial for an optical observatory.By analyzing the behavior of temperature inversion and its correlation with wind and cloud amount,one conclusion can be made that radiation inversion is the main reason for the existence of temperature inversion in the surface-layer at the Muztagh-ata site.
基金supported by the Operation,Maintenance and Upgrading Fund for Astronomical Telescopes and Facility Instruments,budgeted from the Ministry of Finance of China(MOF)and administered by the Chinese Academy of Sciences(CAS)supported by the National Natural Science Foundation of China(Grant No.11873081)。
文摘The Large Optical/infrared Telescope(LOT)is a ground-based 12 m diameter optical/infrared telescope which is proposed to be built in the western part of China in the next decade.Based on satellite remote sensing data,along with geographical,logistical and political considerations,three candidate sites were chosen for ground-based astronomical performance monitoring.These sites include:Ali in Tibet,Daocheng in Sichuan and Muztagh-ata in Xinjiang.Up until now,all three sites have continuously collected data for two years.In this paper,we will introduce this site testing campaign,and present its monitoring results obtained during the period between March 2017 and March 2019.
基金supported by the program of the light in China’s Western Region(LCWRGrant Nos.2015-XBQN-B-04,2015-XBQN-A02)+5 种基金the National Natural Science Foundation of China(Grant Nos.11803076,11873081,11661161016 and U1831209)the 13th Five-year Informatization Plan of Chinese Academy of Sciences(Grant No.XXH13503–03–107)the Youth Innovation Promotion Association CAS(Grant Nos.2014050,2018080)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB23040100)2017 Heaven Lake Hundred-Talent Program of Xinjiang Uygur Autonomous Region of Chinathe Open Project Program of the Key Laboratory of Optical Astronomy(NAOC)。
文摘The Nanshan One-meter Wide-field Telescope is a prime focus system that is located at Nanshan Station of Xinjiang Astronomical Observatories.The field of view was designed to 1.5°× 1.5°,and the Johnson-Cousins UBVRI system was chosen as the main filter set.The telescope has been providing observation services for astronomers since September 2013.Variable source searching and time-domain surveys are the main scientific goals.The system’s test results are reported including linearity,dark current,bias,readout noise and gain of the CCD camera.The accurate instrumental calibration coefficients in UBVRI bands were driven with Landolt standard stars during photometric nights.Finally,the limiting magnitudes are given with signal-to-noise ratios and various exposure times for observers.
基金supported by theNational Nature Science Foundation of China(Grant Nos.11873081 and 11603065)the Operation,Maintenance and Upgrading Fund for Astronomical Telescopes and Facility Instruments,budgeted from the Ministry of Finance of China(MOF)and administered by the Chinese Academy of Sciences。
文摘In this article,we present a detailed analysis of the statistical properties of seeing for the Muztaghata site which is a candidate site for hosting the future Chinese Large Optical/infrared Telescope(LOT)project.The measurements were obtained with differential image motion monitors(DIMMs)from April2017 to November 2018 at different heights during different periods.The median seeings at 11 m and6 m are very close but significantly different from that on the ground.We mainly analyzed the seeing at11 m monthly and hourly,having found that the best season for observing was from late autumn to early winter and seeing tended to improve during the night only in autumn.The analysis of the dependence on temperature inversion,wind speed and direction also was made and the best meteorological conditions for seeing are given.
基金partly supported by the Operation,Maintenance and Upgrading Fund for Astronomical Telescopes and Facility Instruments,budgeted from the Ministry of Finance of China(MOF)and administered by the Chinese Academy of Sciences(CAS)supported by the National Natural Science Foundation of China(Grant Nos.11573054,11703065,11603044 and 11873081)+1 种基金support from a CAS PIFIUK STFC grant ST/R006598/1。
文摘A large ground-based optical/infrared telescope is being planned for a world-class astronomical site in China.The cloud-free night percentage is the primary meteorological consideration for evaluating candidate sites.The data from GMS and NOAA satellites and the MODIS instrument were utilized in this research,covering the period from 1996 to 2015.Our data analysis benefits from overlapping results from different independent teams as well as a uniform analysis of selected sites using GMS+NOAA data.Although significant ground-based monitoring is needed to validate these findings,we identify three different geographical regions with a high percentage of cloud-free conditions(~83%on average),which is slightly lower than at Mauna Kea and Cerro Armazones(~85%on average)and were chosen for the large international projects TMT and ELT respectively.Our study finds evidence that cloud distributions and the seasonal changes affected by the prevailing westerly winds and summer monsoons reduce the cloud cover in areas influenced by the westerlies.This is consistent with the expectations from climate change models and is suggestive that most of the identified sites will have reduced cloud cover in the future.
基金partly supported by the Operation,Maintenance and Upgrading Fund for Astronomical Telescopes and Facility Instruments,budgeted from the Ministry of Finance of China (MOF) and administered by the Chinese Academy of Sciences (CAS)supported by the National NaturalScience Foundation of China (Grant Nos.11573054,11703065,11603044 and 11873081)HRAJ acknowledges support from a CAS PIFI and UK STFC grant ST/R006598/1。
文摘Based on previous site testing and satellite cloud data,Ali,Daocheng and Muztagh-ata have been selected as candidate sites for the Large Optical/Infrared Telescope(LOT) in China.We present the data collection,processing,management and quality analysis for our site testing based on using similar hardware.We analyze meteorological data,seeing,background light,cloud and precipitable water vapor data from 2017 March 10 to 2019 March 10.We also investigated the relative usefulness of our all-sky camera data in comparison to that from the meteorological TERRA satellite data based on a night-by-night comparison of the correlation and consistency between them.We find a 6% discrepancy arising from a wide range of factors.
基金support from the National Natural Science Foundation of China(NSFC,Grant Nos.11403088,11873081,U2031209,11833002,12090040,12090042 and 12003020)partially supported by the Open Project Program of the Key Laboratory of Optical Astronomy,National Astronomical Observatories,Chinese Academy of Sciences。
文摘KIC 10417986 is a short orbital period(0.0737 day)ellipsoidal variable star with aδSct andγDor hybrid pulsation component discovered by Kepler.The ground-based spectroscopic observations were carried out in the winters of 2020 and 2021 to investigate the binary nature of this star.We derive the orbital parameters using the rvfit code with a result of K_(1)=29.7±1.5 km s^(-1),γ=-18.7±1.7 km s^(-1),and confirm an orbital period of 0.84495 day instead of the result given by Kepler.The atmospheric parameters of the primary are determined by the synthetic spectral fitting technique with the estimated values of T_(eff)=7411±187 K,log g=4.2±0.3 dex,[M/H]=0.08±0.09 dex and vsini=52±11 km s^(-1).KIC 10417986 is a circular orbit binary system.From the single-lined nature and mass function of the star,the derived orbital inclination is 26°±6°,and the mass of the secondary is 0.52_(-0.09)^(+0.18)M_(⊙),which should be a late-K to early-M type star.Fourteen frequencies are extracted from Kepler light curves,of which six independent frequencies in the high-frequency region are identified as the p-mode pulsations ofδSct star,and one independent frequency in the low-frequency region(f_(2)=1.3033 cd^(-1))is probably the rotational frequency due to the starspots rather than the ellipsoidal effect.
