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Research in Astronomy and Astrophysics 2024年第7期24卷 161-172页

作者： Yining Wang Rui Sun Tianyuan Deng Chenghui Zhao Peixuan Zhao Jiayi Yang Peng Jia Huigen Liu Jilin Zhou College of Electronic Information and Optical Engineering Taiyuan University of Technology School of Astronomy&Space Science Nanjing University Peng Cheng Lab

The China Space Station Telescope(CSST) is a telescope with 2 m diameter, obtaining images with high quality through wide-field observations. In its first observation cycle, to capture time-domain observation data, the CSST is proposed to observe the Galactic halo across different epochs. These data have significant potential for the study of properties of stars and exoplanets. However, the density of stars in the Galactic center is high, and it is a well-known challenge to perform astrometry and photometry in such a dense star field. This paper presents a deep learning-based framework designed to process dense star field images obtained by the CSST, which includes photometry, astrometry, and classifications of targets according to their light curve periods. With simulated CSST observation data, we demonstrate that this deep learning framework achieves photometry accuracy of 2% and astrometry accuracy of 0.03 pixel for stars with moderate brightness mag = 24(i band), surpassing results obtained by traditional methods. Additionally, the deep learning based light curve classification algorithm could pick up celestial targets whose magnitude variations are 1.7 times larger than magnitude variations brought by Poisson photon noise. We anticipate that our framework could be effectively used to process dense star field images obtained by the CSST.

关键词： astrometry methods: data analysis techniques: photometric

Multi-field Split Curvature Wavefront Sensing and its Application in the Large Field Survey Telescope

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Research in Astronomy and Astrophysics 2024年第8期24卷 62-76页

作者： Zhixu Wu Yiming Zhang Jianan Cong Hua Bai Yong Xia Rongxin Tang Ming Li Zhengyang Li Xiangyan Yuan Institute of Space Science and Technology Nanchang University Nanjing Institute of Astronomical Optics&Technology CAS University of Chinese Academy of Sciences

The image quality of a large field survey telescope with a fast focal ratio of the primary mirror is high sensitivity to the optical elements’misalignments and the primary mirror’s *** maintain good optical performance,the perturbations need to be aligned,and the tomographic reconstruction of these perturbations can be derived from wavefront sensing with multi-field points for *** work undertakes a comprehensive examination related to the implementation and optimization of a multi-field split curvature wavefront sensing system,including defocus distance,signal pre-processing,deblending of overlapped doughnuts,field-dependent correction,and distorted coordinate *** also conduct experiments to demonstrate the application and performance of a multi-field split curvature wavefront sensing system in *** the context of the decentering of the secondary mirror,the coefficient of determination (R) attains a high value of 0.993,indicating a robust linearity between the coma coefficients and the decentering of the secondary mirror.A comparative analysis of the simulated and experimental results shows that the difference between them is less than 0.1λ.

关键词： Instrumentation: high angular resolution techniques: image processing techniques: photometric

Pulsations of Three Rapidly Oscillating Ap Stars TIC 96315731, TIC72392575, and TIC 318007796

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Research in Astronomy and Astrophysics 2024年第8期24卷 159-170页

作者： Hai-Jian Zhong Dong-Xiang Shen Chun-Hua Zhu He-Lei Liu Su-Fen Guo Guo-Liang Lü School of Physical Science and Technology Xinjiang University Xinjiang Astronomical Observatory National Astronomical ObservatoriesChinese Academy of Sciences

We analyze the frequencies of three known roAp stars,TIC 96315731,TIC 72392575,and TIC 318007796,using the light curves from the Transiting Exoplanet Survey *** TIC 96315731,the rotational and pulsational frequencies are 0.1498360 day-1and 165.2609 day-1,*** the case of TIC 72392575,the rotational frequency is 0.25551 *** detect a quintuplet of pulsation frequencies with a center frequency of135.9233 day-1,along with two signals within the second pair of rotational sidelobes of the quintuplet separated by the rotation *** two signals may correspond to the frequencies of a dipole *** TIC318007796,the rotational and pulsational frequencies are 0.2475021 day-1,192.73995 day-1,and196.33065 day-1,*** on the oblique pulsator model,we calculate the rotation inclination （i）and magnetic obliquity angle （b） for the stars,which provide the geometry of the pulsation *** the phases of the frequency quintuplets,the pulsation amplitude and phase modulation curves,and the results of spherical harmonic decomposition,we conclude that the pulsation modes of frequency quintuplets in TIC96315731,TIC 72392575,and TIC 318007796 correspond to distorted dipole mode,distorted quadrupole mode,and distorted dipole mode,respectively.

关键词： asteroseismology stars: chemically peculiar stars: oscillations (including pulsations) techniques: photometric

photometric and Spectroscopic Study of Ten Low Mass Ratio Contact Binary Systems: Orbital Stability, O'Connell Effect and Infrared Calcium Line Filling

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Research in Astronomy and Astrophysics 2024年第8期24卷 214-224页

作者： Surjit S.Wadhwa Adam Popowicz Raúl Michel Petar Kosti? Oliver Vince Nick F.H.Tothill Ain Y.De Horta Miroslav D.Filipovi? School of Science Western Sydney University Department of Electronics Electrical Engineering and MicroelectronicsSilesian University of Technology Instituto de Astronomía Astronomical Observatory

Low mass ratio contact binary systems are more likely to have unstable orbits and potentially *** addition,such systems exhibit characteristics such as starspots and high energy emissions (UV) suggestive of chromospheric and magnetic *** curve modeling of ten contact binary systems is *** were found to be of extreme low mass ratio ranging from 0.122 to 0.24 and three were found to be potentially unstable and possible merger *** of the infrared calcium absorption lines is a marker of increased chromospheric *** use the available Large Sky Area Multi-Object Fiber Spectroscopic Telescope spectra along with matched standard spectra (broadened for rotation) to measure the excess filling of the central core depression flux of the two main infrared calcium absorption linesλ8542 andλ*** find that all reported contact binaries have excess filling of the core flux in the infrared calcium *** of the systems reported were also observed by the Galaxy Evolution Explorer mission and we find that all three have features of excess ultraviolet emissions further adding evidence for increased chromospheric activity in low mass ratio contact *** of both orbital stability and absorption line filling is dependent on the determination of geometric and absolute parameters from light curve *** an insignificant number of contact binary light curves exhibit the O’Connell effect,usually attributed to *** discuss the inclusion of starspots in light curve solutions and how they influence the geometric and absolute parameters.

关键词： (stars:) binaries: eclipsing techniques: photometric stars: chromospheres LIGHT-CURVE SOLUTION TRIPLET EXPLANATION UNIQUENESS

Understanding the Activity Performance of Comets 38P/Stephan-Oterma,64P/Swift-Gehrels and C/2017 M4(ATLAS) through Broadband photometric Observations

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Research in Astronomy and Astrophysics 2024年第8期24卷 149-158页

作者： Xuan Zhang Jin-Zhong Liu Le-Tian Wang Xinjiang Astronomical Observatory Chinese Academy of Sciences

In this work,we report observations of three comets:38P/Stephan-Oterma,64P/Swift-Gehrels,and C/2017 M4（ATLAS）,conducted with the Nanshan one-meter wide-field telescope in 2018 August and November,and *** extracted morphological features through image enhancement techniques and calculated the dust activity parameter,Afρ,along with dust mass loss rates and coma color indices using broadband photometric *** morphological analysis uncovered a spectrum of dust characteristics among the observed comets,ranging from a significant twisted structure in comet 38P/Stephan-Oterma’s coma to the regular coma envelope surrounding comet 64P/*** Afρvalues varied between 148.8±0.3 cm for 64P/Swift-Gehrels and1118.5±6.2 cm for C/2017 M4 （ATLAS）(measured within a reference aperture radius ofρ=6″),indicating a range from moderate to high activity *** mass loss rates were estimated from 328.1 kg s-1for comet 64P/Swift-Gehrels to 1395.5 kg s-1for comet C/2017 M4 （ATLAS）.The color indices of comets 38P/Stephan-Oterma and C/2017 M4 （ATLAS） closely resemble the average colors of active short-period comets and active longperiod comets,*** contrast,64P/Swift-Gehrels exhibits a significantly bluer hue than typical Jupiter family comets.

关键词： comets: general comets: individual (38P/Stephan-Oterma, 64P/Swift-Gehrels, C/2017 M4 (ATLAS)) techniques: photometric

Detection of large color variation in the potentially hazardous asteroid(297274) 1996 SK

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Research in Astronomy and Astrophysics 2014年第3期14卷 311-318页

作者： Chien-Hsien Lin Wing-Huen Ip Zhong-Yi Lin Fumi Yoshida Yu-Chi Cheng Space Science Institute Macao University of Science and Technology Institute of Astronomy National Central University National Astronomical Observatory Osawa MitakaTokyo

Low-inclination near-earth asteroid （NEA）（297274） 1996 SK, which isalso classified as a potentially hazardous asteroid, has a highly eccentric orbit. Itwas studied by multi-wavelength photometry within the framework of an NEA colorsurvey at Lulin Observatory. Here, we report the finding of large color variationacross the surface of （297274） 1996 SK within one asteroidal rotation period of4.656 ± 0.122 hours and classify it as an S-type asteroid according to its averagecolors ofB - V = 0.767 ± 0.033, V - R = 0.482 ± 0.021, V - I = 0.801 ± 0.025and the corresponding relative reflectance spectrum. These results might be indica-tive of differential space weathering or compositional inhomogeneity in the surfacematerials.

关键词： minor planets, asteroids: individual: PHA (297274) techniques: photometric

Long-term transit timing monitoring and homogenous study of WASP-32

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Research in Astronomy and Astrophysics 2015年第1期15卷 117-126页

作者： Lei-Lei Sun Sheng-Hong Gu Xiao-Bin Wang Andrew Collier Cameron Dong-Tao Cao Yi-Bo Wang Yue Xiang Ho-Keung Hui Chi-Tai Kwok Bill Yeung Kam-Cheung Leung Yunnan Observatories Chinese Academy of Sciences Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences University of Chinese Academy of Sciences School of Physics and Astronomy University of St Andrews North Haugh St Andrews Fife KY16 9SS UK Ho Koon Nature Education cum Astronomical Centre Hong Kong Astronomical Society

We report new photometric observations of the transiting exoplanetary system WASP-32 made by using CCD cameras at Yunnan Observatories and Ho Koon Nature Education cum Astronomical Centre, China from 2010 to 2012. Following our usual procedure, the observed data are corrected for systematic errors according to the coarse decorrelation and SYSREM algorithms so as to enhance the signal of the transit events. Combined with radial velocity data presented in the literature, our newly observed data and earlier photometric data in the literature are simultaneously analyzed to derive the physical parameters describing the system by employing the Markov chain Monte Carlo technique. The derived parameters are consistent with the result published in the original paper about WASP-32b, but the uncertainties of the new parameters are smaller than those in the original paper. Moreover, our modeling result supports a circular orbit for WASP-32b. Through the analysis of all available mid-transit times, we have refined the orbital period of WASP-32b; no evident transit timing variation is found in these transit events.

关键词： techniques: photometric transiting exoplanetary system individual: WASP-32

The search for roAp stars: null results and new candidates from Strmgren-Crawford photometry

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Research in Astronomy and Astrophysics 2018年第11期18卷 43-54页

作者： Ernst Paunzen Gerald Handler Katerina Honkova Jakub Jurysek Martin Masek Marek Drozdz Jan Janik Waldemar Ogtoza Lars Hermansson Mats Johansson Martin Jelinek Marek Skarka Miloslav Zejda Department of Theoretical Physics and Astrophysics Masaryk UniversityKotlarska 2CZ-61137Czech Republic Nicolaus Copernicus Astronomical Center Bartycka 1800-716WarsawPoland Variable Star and Exoplanet Section of Czech Astronomical Society Vsetinska 941/78CZ-75701Valasske MeziriciCzech Republic Institute of Physics The Czech Academy of SciencesNa Slovance 1999/2CZ-18221PrahaCzech Republic Mt.Suhora Observatory Pedagogical UniversityPodchorazych 230-084KrakowPoland Sandvretens Observatory Linnegatan 5A75332UppsalaSweden Astronomical Institute Czech Academy of Sciences(ASU CAS)OndrejovCzech Republic

The rapidly oscillating Ap(roAp) stars exhibit pulsational photometric and/or radial velocity variations on time scales of several minutes, which are essential to test current pulsation models as well as our assumptions of atmospheric structure characteristics. In addition, their chemical peculiarity makes them very interesting for probing stellar formation and evolution in the presence of a global magnetic field. To date, a limited number of only 61 roAp stars is known to show photometric variability. On the other hand, a literature survey yields 619 unique stars that have unsuccessfully been searched for variability of this kind. Str o¨mgren-Crawford uvbyβ photometry of stars from both subgroups was used to investigate whether there is a selection bias for the investigated stars. We also present new photometric measurements(202 hours on 59 different nights) of 55 roAp candidates. We did not detect any new roAp star. Although our detection limits are comparable to other surveys, we also did not find pulsations in the known roAp star HD 12098, which may be a consequence of temporal amplitude changes. On the other hand, we do find some evidence for photometric variability of beta CrB at its spectroscopically derived pulsation period. From the uvbyβ photometry we conclude that the blue border of the roAp instability strip appears observationally well defined, whereas the red border is rather poorly known and *** these boundaries, a total of 4646 candidates were identified which appear worth investigating for short-term pulsational variability.

关键词： stars: chemically peculiar stars: early-type stars: variables: general techniques: photometric

The correction of diurnal effects on CSTAR photometry

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Research in Astronomy and Astrophysics 2014年第3期14卷 345-356页

作者： Song-Hu Wang Xu Zhou Hui Zhang Ji-Lin Zhou Hui-Gen Liu Ze-Yang Meng Jun Ma Tian-Meng Zhang Zhou Fan Hu Zou Department of Astronomy & Key Laboratory of Modern Astronomy and Astrophysics in Ministry of Education Nanjing University National Astronomical Observatories Chinese Academy of Sciences

In January, 2008 the Chinese Small Telescope ARray （CSTAR） was suc-cessfully deployed at Dome A, Antarctica. Because CSTAR consists of four static14.5 cm telescopes pointing at the same 4.5° x 4.5° field around the south celestialpole, diurnal motion can be seen in its field of view. The stars are centered at differentpositions in different exposure frames. During four months of continuous observationsduring the polar night of 2008, about 0.3 million/-band images were obtained. In thelatest version of the released photometric catalog, the effects of diurnal motion of thestars on the static CSTAR optical system can be obviously found. In this work, weupdate the CSTAR catalog by carefully analyzing and correcting the systematic errorscaused by diurnal motion of stars on imperfectly flat-fielded frames.

关键词： methods: data analysis techniques: photometric

Discovery of Four Peculiar Variable Stars

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Chinese Journal of Astronomy and Astrophysics 2003年第4期3卷 311-315页

作者： Xiao-BinZhang Rong-XianZhang CAS-PKUJointBeijingAstrophysicsCenter Beijing100871 NationalAstronomicalObservatories ChineseAcademyofSciencesBeijing100012

Four stars, GSC 1258–0143, GSC 1986–1665, GSC 3045–0892 and GSC 2983–1597 were found to be new variables during a campaign of CCD photometric monitoring of short-period eclipsing binary stars. The variabilities of these new variables are reported. The main characteristics and probable classifications of the variables are discussed through a preliminary analysis on their light curves. Among these stars, GSC 1258–0143 is classified as a RR Lyr star of sub-type a. Its pulsation period is determined to be about 0.5206 days. The other three stars, are definite variables, but their periods and types of light variations remain unknown.

关键词： techniques: photometric stars: variables: RR Lyr stars: individual: GSC1258-0143, GSC 1986-1665, GSC 3045-0892, GSC 2983-1597