Xinglong Station Research Articles

Two Long-period Giant Planets around Two Giant Stars: HD 112570 and HD 154391

We present the discoveries of two giant plants orbiting the red-giant-branch star HD 112570 and the red-clump star HD 154391, based on the radial-velocity (RV) measurements from the Xinglong station and Okayama Astrophysical Observatory. Spectroscopic and asteroseismic analyses suggest that HD 112570 has a mass of 1.15 ± 0.12 M ☉, a radius of 9.85 ± 0.23 R ☉, a metallicity [Fe/H] of −0.46 ± 0.1, and logg of 2.47 ± 0.1. With the joint analysis of RV and Hipparcos-Gaia astrometry, we obtain a dynamical mass of Mp=3.42−0.84+1.4MJup , a period of P=2615−77+85 days, and a moderate eccentricity of e=0.20−0.14+0.16 for the Jovian planet HD 112570 b. For HD 154391, it has a mass of 2.07 ± 0.03 M ☉, a radius of 8.56 ± 0.05 R ☉, a metallicity [Fe/H] of 0.07 ± 0.1, and logg of 2.86 ± 0.1. The super-Jupiter HD 154391 b has a mass of Mp=9.1−1.9+2.8MJup , a period of P=5163−57+60 days, and an eccentricity of e=0.20−0.04+0.04 . We found that HD 154391 b has one of the longest orbital periods among those ever discovered orbiting evolved stars, which may provide a valuable case in our understanding of planetary formation at wider orbits. Moreover, while a mass gap at 4 M Jup seems to be present in the population of giant stars, there appear to be no significant differences in the distribution of metallicity among giant planets with masses above or below this threshold. Finally, the origin of the abnormal accumulation near 2 au for planets around large evolved stars (R ⋆ > 21 R ☉), remains unclear.

Taxonomic Analysis of Asteroids with Artificial Neural Networks

We study the surface composition of asteroids with visible and/or infrared spectroscopy. For example, asteroid taxonomy is based on the spectral features or multiple color indices in visible and near-infrared wavelengths. The composition of asteroids gives key information to understand their origin and evolution. However, we lack compositional information for faint asteroids due to the limits of ground-based observational instruments. In the near future, the Chinese Space Survey Telescope (CSST) will provide multiple colors and spectroscopic data for asteroids of apparent magnitude brighter than 25 and 23 mag, respectively. With the aim of analyzing the CSST spectroscopic data, we applied an algorithm using artificial neural networks (ANNs) to establish a preliminary classification model for asteroid taxonomy according to the design of the survey module of CSST. Using the SMASS II spectra and the Bus–Binzel taxonomic system, our ANN classification tool composed of five individual ANNs is constructed, and the accuracy of this classification system is higher than 92%. As the first application of our ANN tool, 64 spectra of 42 asteroids obtained by us in 2006 and 2007 with the 2.16 m telescope in the Xinglong station (Observatory Code 327) of National Astronomical Observatory of China are analyzed. The predicted labels of these spectra using our ANN tool are found to be reasonable when compared to their known taxonomic labels. Considering its accuracy and stability, our ANN tool can be applied to analyze CSST asteroid spectra in the future.

Analysis of Airglow Image Classification Based on Feature Map Visualization

All-sky airglow imagers (ASAIs) are used in the Meridian Project to observe the airglow in the middle and upper atmosphere to study the atmospheric perturbation. However, the ripples of airglow caused by the perturbation are only visible in the airglow images taken on a clear night. It is a problem to effectively select images suitable for scientific analysis from the enormous amount of airglow images captured under various environments due to the low efficiency and subjectivity of traditional manual classification. We trained a classification model based on convolutional neural network to distinguish between airglow images from clear nights and unclear nights. The data base contains 1688 images selected from the airglow images captured at Xinglong station (40.4° N, 30.5° E). The entire training process was tracked by feature maps which visualized every resulting classification model. The classification models with the clearest feature maps were saved for future use. We cropped the central part of the airglow images to avoid disturbance from the artificial lights at the edge of the vision field according to the feature maps of our first training. The accuracy of the saved model is 99%. The feature maps of five categories also indicate the reliability of the classification model.

Minute-cadence Observations of the LAMOST Fields with the TMTS: I. Methodology of Detecting Short-period Variables and Results from the first-year Survey

Abstract Tsinghua University-Ma Huateng Telescopes for Survey (TMTS), located at Xinglong Station of NAOC, has a field of view up to 18 deg2. The TMTS has started to monitor the LAMOST sky areas since 2020, with the uninterrupted observations lasting for about 6 hours on average for each sky area and a cadence of about 1 minute. Here we introduce the data analysis and preliminary scientific results for the first-year observations, which covered 188 LAMOST plates (≈1970 deg2). These observations have generated over 4.9 million uninterrupted light curves, with at least 100 epochs for each of them. These light curves correspond to 4.26 million Gaia-DR2 sources, among which 285 thousand sources are found to have multi-epoch spectra from the LAMOST. By analysing these light curves with the Lomb-Scargle periodograms, we identify more than 3700 periodic variable star candidates with periods below ≈7.5 hours, primarily consisting of eclipsing binaries and δ Scuti stars. Those short-period binaries will provide important constraints on theories of binary evolution and possible sources for space gravitational wave experiments in the future. Moreover, we also identified 42 flare stars by searching rapidly-evolving signals in the light curves. The densely-sampled light curves from the TMTS allow us to better quantify the shapes and durations for these flares.

Innovations in science and technology with the LAMOST

<p indent=0mm>The LAMOST (Large Sky Area Multi-Object Fiber Spectroscopic Telescope) is a special reflecting Schmidt telescope with an effective aperture of <sc>3.6–4.9 m,</sc> a focal length of <sc>20 m</sc> and a field of view (FOV) of 5 degrees. Its optical system is designed with three major components, namely Ma, Mb, and a focal surface. The correcting mirror Ma <sc>(5.72 m</sc>×<sc>4.40 m)</sc> is made up of 24 hexagonal plane sub-mirrors; the primary mirror Mb <sc>(6.67 m</sc>×<sc>6.05 m)</sc> has 37 hexagonal spherical sub-mirrors. In the process of observation, Ma is capable of synchronously changing its specific aspherical figure to give excellent optical quality. The focal surface has 4000 precisely positioned fibers connected to 16 spectrographs with a distributive parallel-controllable fiber positioning system, thus LAMOST can observe up to 4000 objects simultaneously. LAMOST adopts an innovative active optics technique, achieved by changing its mirror surface continuously to achieve a series different reflecting Schmidt systems. This novel concept and unique design broke through the bottleneck of former astronomical instruments that could not combine a large clear aperture with a wide FOV. The new active optics system creatively developed in LAMOST is used for correcting Ma, which is a combination of the thin deformable mirror active and segmented active optics. The distributive parallel-controllable fiber positioning technique is also an advanced technology which solved the problem of simultaneously and accurately locating 4000 astronomical objects. LAMOST opened up the ability to have a large scale optical fiber spectroscopic sky survey with as many as 4000 optical fibers. The LAMOST project was approved as a national major science project by the Chinese government in April 1997. LAMOST started to be constructed in August 2001. The installation of all LAMOST systems was completed on time in August 2008. The telescope is located at the Xinglong Station of National Astronomical Observatories, Chinese Academy of Sciences (NAOC). After the two years commissioning period starting in 2009, a pilot spectroscopic survey was performed using LAMOST from October 2011 to June 2012. The regular survey of LAMOST began in September 2012. Up to June 2020, LAMOST has obtained more than 17 million spectra of celestial objects, in which the stellar parameters of 7.7 million stars were obtained. The data archive of LAMOST would be an exceedingly valuable resource for a variety of astronomical fields. It would be used as a “digital Galaxy” to understand our Galaxy. As the telescope of the highest spectrum acquiring rate, LAMOST breaks through the “bottleneck” of spectroscopic observation in astronomy, becoming the most powerful spectroscopic survey telescope for researches of wide field and large sample astronomy. LAMOST yields a unique data set of more than 10 million stellar spectra and makes a substantial contribution to the study of stellar astrophysics and the research of the Galaxy, such as stellar populations, chemical composition, kinematics and structure of the disk and the halo, gravitational potential and dark matter distribution in the Galaxy, interstellar dust extinction, extremely metal-poor and hyper-velocity stars, and to ultimately advance our understanding of the assemblage of the Milky Way and other galaxies and the origin of regularity and diversity of their properties.

Technology on Settlement Control of Large Diameter Shield Traversing Closely Beneath High-pressure Gas Pipeline for Metro Tunnel

Taking the project of sectional tunnel traversing closely beneath high-pressure gas pipeline on Weiqing Line between Xinglong Station and Tianfuxin Station in Chengdu Metro Line 18 for an example, the technology controlling the settlement is studied. Based on the reinforcement isolation grouting with inclined boreholes, driving control parameters of shield and grouting behind the sectional tunnel lining with deep holes, the control technology on the large diameter shield passing closely beneath high-pressure gas pipeline is established for metro tunnels. The application of this technology controls the settlement of high pressure gas pipe within - 4mm, less than - 5mm, which verifies the practicability of this technology. At the same time, it greatly improves the stability of pipeline, guarantees the safety of pipeline operation, and provides the reference for similar projects in the future.

Numerical Simulation Analysis of Cutter Head of Large Diameter Metro Shield with Soft Upper and Hard Bottom

Taking the large-diameter shield cutter head between Xinglong Station and Tianfu new station in Civil Engineering Section 4 of Chengdu metro line 18 as an example, the numerical simulation is carried out by finite element software to analyze the stress and deformation of large-diameter shield cutter head under different loads in upper soft and lower hard strata. The results show that the stress and deformation of cutter head meet the design requirements, which can provide certain reference value for similar projects in the future.

Responses of Multiday Oscillations in the Nighttime Thermospheric Temperature to Solar and Geomagnetic Activities Measured by Fabry‐Perot Interferometer in China

AbstractThe nighttime thermospheric temperature (~250 km) measured by FPI (Fabry‐Perot interferometer) at Xinglong (40.2°N, 117.4°E) station from 2010 to 2018 is used to investigate the responses of the multiday oscillations (periods of 27, 13.5, 9, and 7 days) in thermospheric temperature to oscillations in F10.7 and Ap index. The results show that (1) the 27‐, 13.5‐, 9‐, and 7‐day oscillations in the thermospheric temperature depend on solar phases. The 27‐day oscillations are predominant during solar maximum, while the 13.5‐, 9‐, and 7‐day oscillations are significant during solar ascending phase, and (2) the 27‐day oscillations in the thermospheric temperature are highly correlated (correlation coefficient &gt;0.8) with the F10.7 and Ap index. Especially during solar maximum phase, the high‐correlation occurrence rate between the thermospheric temperature and F10.7 (Ap index) is up to 278.5 (191.0) days per year; (3) the 13.5‐, 9‐, and 7‐day oscillations are highly correlated with Ap index during the solar descending phase; and (4) the phase lags corresponding to the largest high‐correlation occurrence rates are mostly about 0.1π during specific solar phase.

An Hα Imaging Survey of All (Ultra)luminous Infrared Galaxies at Decl. ≥ −30° in the GOALS Sample

Abstract This paper presents the result of Hα imaging for luminous and ultraluminous infrared galaxies. It is a complete subsample of the Great Observatories All-sky LIRG Survey (GOALS) with decl. ≥ −30°, and consists of 148 galaxies with log(L IR/L ☉) ≥ 11.0. All the Hα images were carried out using the 2.16 m telescope at the Xinglong Station of the National Astronomy Observatories, Chinese Academy of Sciences (NAOC), during the year from 2006 to 2009. We obtained the pure Hα luminosity for each galaxy and corrected the luminosity for [N ii] emission, filter transmission, and extinction. We also classified these galaxies based on their morphology and interaction. We found that the distribution of star-forming regions in these galaxies is related to this classification. As the merging process advanced, these galaxies tended to have a more compact distribution of star-forming regions, higher L IR, and warmer IR-color (f 60/f 100). These results imply that the degree of dynamical disturbance plays an important role in determining the distribution of a star-forming region.

Simultaneous optical g, r, i monitoring and IDV periodic analysis for quasar 3C 454.3

With the 1.26 m National Astronomical Observatory-Guangzhou University Infrared/Optical Telescope (NAGIOT) at Xinglong Station of National Astronomical Observatories, Chinese Academy of Sciences, we obtained 419 groups of simultaneous observations at g, r and i bands, for the first time, targeting quasar 3C 454.3 during 15 nights from 2016 October 23 to 2016 December 15. Based on our observations, we investigate the optical variabilities, the relation between brightness and color index, and the periodicity variability. The presented analyses demonstrate that: 1. The maximum variations at the g, r and i bands are Δ mg|max = 1.015 ± 0.042 mag, Δ mr|max = 1.188 ± 0.050 mag and Δ mi|max = 1.305 ± 0.057 mag respectively. 2. During our 15 night monitoring program, intra-day variability was detected on one night (Nov. 2). Also, the brightness increased by A = 15.86% over 50.8 min, then decreased by A = 22.42% over 40.1 min. After a small bright state, its brightness increased again by 18.1% over 55 min at the g band. Similar phenomena happened at r and i bands. The intra-day variabilities at the three bands on 2016 November 2 indicate a period of 105 min, which implies a black hole mass of MBH = (0.3 ∼ 1.85) × 109 M⊙. 3. There is an anti-correlation between color index and magnitude, suggesting the source becomes redder when it brightens.

In-situ measurement of CO2 at the Xinglong regional background station over North China

ABSTRACTHigh-accuracy continuous measurements of atmospheric concentrations of CO2 were made from May 2016 to December 2017 using the Picarro G2301 analyzer at Xinglong station (40°24′N, 117°30′E, ...

Upgraded photometric system on the 85-cm telescope at Xinglong station

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 UBVRI 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 UBVRI 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.

PS Vir: a short-period solar-like contact binary

We present multi-color photometric observations and a one-dimensional spectrum, acquired from March 2016 to May 2017, for the short-period eclipsing binary PS Vir, by using the 2.16-m, 85-cm and 60-cm telescopes at Xinglong station, which is administered by National Astronomical Observatories, Chinese Academy of Sciences. The spectral type was determined as G2V from the one-dimensional spectrum. The photometric solution was reduced from BVRc light curves. The results imply that PS Vir is a W-subtype contact binary with a mass ratio of q=0.305(±0.008) and a fill-out factor of f=14.4(±1.8)%. The orbital period may be undergoing a cyclic oscillation with an amplitude of A=0.0027(±0.0001) d and a modulated period of 11.7(±0.2) yr, which may result from the light-time effect due to a third body. The lower limit on mass for the assumed component is . Moreover, the more massive component of PS Vir may be a bit more evolved star as determined from the mass-luminosity diagram.

Internal Variations in Empirical Oxygen Abundances for Giant H ii Regions in the Galaxy NGC 2403

Abstract This paper presents a spectroscopic investigation of 11 regions in the nearby galaxy NGC 2403. The regions are observed with a long-slit spectrograph mounted on the 2.16 m telescope at XingLong station of National Astronomical Observatories of China. For each of the regions, spectra are extracted at different nebular radii along the slit-coverage. Oxygen abundances are empirically estimated from the strong-line indices R23, , , and N2 for each spectrophotometric unit, with both observation- and model-based calibrations adopted into the derivation. Radial profiles of these diversely estimated abundances are drawn for each nebula. In the results, the oxygen abundances separately estimated with the prescriptions on the basis of observations and models, albeit from the same spectral index, systematically deviate from each other; at the same time, the spectral indices R23 and are distributed with flat profiles, whereas N2 and exhibit apparent gradients with the nebular radius. Because our study naturally samples various ionization levels, which inherently decline at larger radii within individual regions, the radial distributions indicate not only the robustness of R23 and against ionization variations but also the sensitivity of N2 and to the ionization parameter. The results in this paper provide observational corroboration of the theoretical prediction about the deviation in the empirical abundance diagnostics. Our future work is planned to investigate metal-poor regions with measurable T e, in an attempt to recalibrate the strong-line indices and consequently disclose the cause of the discrepancies between the empirical oxygen abundances.

New precise astrometric observations of Nereid in 2012–2017

Nereid is one of the most distinctive natural satellites that we know in the Solar system. The orbit of Nereid is highly eccentric and inclined with respect to the equator of its primary, Neptune. Studying Nereid is one of the inspiring ways to acquire better knowledge of the Solar system. Due to its faintness, the ground-based observations of Nereid have been limited and the observation precisions in the past were generally not high. A total of 150 new observed positions of Nereid in the period 2012–2017 were collected by the 0.8 m reflecting telescope at Xinglong station of National Astronomical Observatory and the 2.4 m reflecting telescope at Lijiang station of Yunnan Astronomical Observatory. Thanks to the high-quality reference catalogue Gaia DR1 and suitable processing methods for images, the precision of our new observations of Nereid is 2–3 times higher than those of the previous observations, and the dispersions of our observations are better than 70 mas.

Mid-latitude thermospheric wind changes during the St. Patrick’s Day storm of 2015 observed by two Fabry-Perot interferometers in China

In this work, we utilize thermospheric wind observations by the Fabry-Perot interferometers (FPI) from the Kelan (KL) station (38.7°N, 111.6°E, Magnetic Latitude: 28.9°N) and the Xinglong (XL) station (40.2°N, 117.4°E, Magnetic Latitude: 30.5°N) in central China during the St. Patrick’s Day storm (from Mar. 17 to Mar. 19) of 2015 to analyze thermospheric wind disturbances and compare observations with the Horizontal Wind Model 2007 (HWM07). The results reveal that the wind measurements at KL show very similar trends to those at XL. Large enhancements are seen in both the westward and equatorward winds after the severe geomagnetic storm occurred. The westward wind speed increased to a peak value of 75 m/s and the equatorward wind enhanced to a peak value of over 100 m/s. There also exist obvious poleward disturbances in the meridional winds during Mar. 17 to Mar. 19. According to the comparison with HWM07, there exist evident wind speed and temporal differences between FPI-winds and the model outputs in this severe geomagnetic storm. The discrepancies between the observations and HWM07 imply that the empirical model should be used carefully in wind disturbance forecast during large geomagnetic storms and more investigations between measurements and numerical models are necessary in future studies.

Pulsations and period variations of the δ Scuti star AN Lyncis in a possible three-body system

Observations for the $\delta$ Scuti star AN Lyn have been made between 2008 and 2016 with the 85-cm telescope at Xinglong station of National Astronomical Observatories of China, the 84-cm telescope at SPM Observatory of Mexico and the Nanshan One meter Wide field Telescope of Xinjiang Observatory of China. Data in $V$ in 50 nights and in $R$ in 34 nights are obtained in total. The bi-site observations from both Xinglong Station and SPM Observatory in 2014 are analyzed with Fourier Decomposition to detect pulsation frequencies. Two independent frequencies are resolved, including one non-radial mode. A number of stellar model tracks are constructed with the MESA code and the fit of frequencies leads to the best-fit model with the stellar mass of $M = 1.70 \pm 0.05~\mathrm{M_{\odot}}$ , the metallicity abundance of $Z = 0.020 \pm 0.001$, the age of $1.33 \pm 0.01$ billion years and the period change rate $1/P\cdot \mathrm{d}P/\mathrm{d}t =1.06 \times 10^{-9} ~\mathrm{yr^{-1}} $, locating the star at the evolutionary stage close to the terminal age main sequence (TAMS). The O-C diagram provides the period change rate of $1/P \cdot \mathrm{d}P /\mathrm{d}t =4.5(8)\times10^{-7}~\mathrm{yr^{-1}}$. However, the period change rate calculated from the models is smaller in two orders than the one derived from the O-C diagram. Together with the sinusoidal function signature, the period variations are regarded to be dominated by the light-travel time effect of the orbital motion of a three-body system with two low-luminosity components, rather than the stellar evolutionary effect.

Transiting Exoplanet Monitoring Project (TEMP). II. Refined System Parameters and Transit Timing Analysis of HAT-P-33b

Abstract We present 10 R-band photometric observations of eight different transits of the hot Jupiter HAT-P-33b, which has been targeted by our Transiting Exoplanet Monitoring Project. The data were obtained by two telescopes at the Xinglong Station of National Astronomical Observatories of China (NAOC) from 2013 December through 2016 January, and exhibit photometric scatter of . After jointly analyzing the previously published photometric data, radial-velocity (RV) measurements, and our new light curves, we revisit the system parameters and orbital ephemeris for the HAT-P-33b system. Our results are consistent with the published values except for the planet to star radius ratio ( ), the ingress/egress duration (τ) and the total duration (T 14), which together indicate a slightly shallower and shorter transit shape. Our results are based on more complete light curves, whereas the previously published work had only one complete transit light curve. No significant anomalies in Transit Timing Variations (TTVs) are found, and we place upper mass limits on potential perturbers, largely supplanting the loose constraints provided by the extant RV data. The TTV limits are stronger near mean-motion resonances, especially for the low-order commensurabilities. We can exclude the existence of a perturber with mass larger than 0.6, 0.3, 0.5, 0.5, and near the 1:3, 1:2, 2:3, 3:2, and 2:1 resonances, respectively.

The empirical correlations between PM2.5, PM10 and AOD in the Beijing metropolitan region and the PM2.5, PM10 distributions retrieved by MODIS

We observed PM2.5, PM10 concentration, aerosol optical depth (AOD), and Ångström exponents (α) in three typical stations, the Beijing city, the Xianghe suburban and the Xinglong background station in the Beijing metropolitan region, from 2009 to 2010, synchronously. The annual means of PM2.5 (PM10) were 62 ± 45 (130 ± 88) μg m−3 and 79 ± 61 (142 ± 96) μg m−3 in the city and suburban region, which were much higher than the regional background (PM2.5: 36 ± 29 μg m−3). The annual means of AOD were 0.53 ± 0.47 and 0.54 ± 0.46 and 0.24 ± 0.22 in the city, suburban and the background region, respectively. The annual means of Ångström exponents were 1.11 ± 0.31, 1.09 ± 0.31 and 1.02 ± 0.31 in three typical stations. Meanwhile, the rates of PM2.5 accounting for PM10 were 44%–54% and 46%–70% in the city and suburban region during four seasons. The pollution of fine particulate was more serious in winter than other seasons. The linear regression functions of PM2.5 (y) and ground-observed AOD (x) were similarly with high correlation coefficient in the three typical areas, which were y = 74x + 18 (R2 = 0.58, N = 337, in the City), y = 80x + 25 (R2 = 0.55, N = 306, in the suburban) and y = 87x + 9 (R2 = 0.64, N = 350, in the background). The functions of PM10 (y) and ground-observed AOD (x) were y = 112x + 57 (R2 = 0.54, N = 337, in the city) and y = 114x + 68 (R2 = 0.47, N = 304, in the suburban). But the functions had large differences in four seasons. The correlations between PM2.5, PM10 and MODIS AOD were similar with the correlations between PM2.5, PM10 and the ground-observed AOD. With MODIS C6 AOD, the distributions of PM2.5 and PM10 concentration were retrieved by the seasonal functions. The absolute retrieval errors of seasonal PM2.5 distribution were less than 5 μg m−3 in the pollutant city and suburb, and less than 7 μg m−3 in the clean background.

An isolated compact galaxy triplet

We report the discovery of an isolated compact galaxy triplet SDSS J084843.45+164417.3, which is first detected by the LAMOST spectral survey and then confirmed by a spectroscopic observation of the BFOSC mounted on the 2.16 meter telescope located at Xinglong Station, which is administered by National Astronomical Observatories, Chinese Academy of Sciences. It is found that this triplet is an isolated and extremely compact system, which has an aligned configuration and very small radial velocity dispersion. The member galaxies have similar colors and show marginal star formation activities. These results support the opinion that the compact triplets are well-evolved systems rather than hierarchically forming structures. This serendipitous discovery reveals the limitations of fiber spectral redshift surveys in studying such a compact system, and demonstrates the necessity of additional observations to complete the current redshift sample.