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A Statistical Study of Magnetic Flux Emergence in Solar Active Regions Prior to Strongest Flares

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Research in Astronomy and Astrophysics 2024年第4期24卷 147-160页

作者： Alexander S.Kutsenko Valentina I.Abramenko Andrei A.Plotnikov Crimean Astrophysical observatory p/o NauchnyCrimea298409Russia

Using the data on magnetic field maps and continuum intensity for Solar Cycles 23 and 24,we explored 100 active regions(ARs)that produced M5.0 or stronger *** focus on the presence/absence of the emergence of magnetic flux in these ARs 2-3 days before the strong flare *** found that 29 ARs in the sample emerged monotonically amidst quiet-Sun.A major emergence of a new magnetic flux within a pre-existing AR yielding the formation of a complex flare-productive configuration was observed in another 24 *** 30 ARs,an insignificant(in terms of the total magnetic flux of pre-existing AR)emergence of a new magnetic flux within the pre-existing magnetic configuration was observed;for some of them the emergence resulted in a formation of a configuration with a small δ-sunspot;11 out of 100 ARs exhibited no signatures of magnetic flux emergence during the entire interval of *** six cases the emergence was in progress when the AR appeared on the Eastern limb,so that the classification and timing of emergence were not *** conclude that the recent flux emergence is not a necessary and/or sufficient condition for strong flaring of an *** flux emergence rate of flare-productive ARs analyzed here was compared with that of flare-quiet ARs analyzed in our previous *** revealed that the flare-productive ARs tend to display faster emergence than the flare-quiet ones do.

关键词： Sun:activity Sun:flares Sun:magnetic fields

VLBI with SKA: Possible Arrays and Astrometric Science

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Research in Astronomy and Astrophysics 2024年第7期24卷 4-36页

作者： Yingjie Li Ye Xu Jingjing Li Shuaibo Bian Zehao Lin Chaojie Hao Dejian Liu Purple Mountain observatory Chinese Academy of Sciences University of Science and Technology of China

The next generation of very long baseline interferometry(VLBI) is stepping into the era of microarcsecond(μas)astronomy, and pushing astronomy, especially astrometry, to new heights. VLBI with the Square Kilometre Array(SKA), SKA-VLBI, will increase current sensitivity by an order of magnitude, and reach astrometric precision routinely below 10 μas, even challenging 1 μas. This advancement allows precise parallax and proper motion measurements of various celestial objects. Such improvements can be used to study objects(including isolated objects, and binary or multiple systems) in different stellar stages(such as star formation, main-sequence stars,asymptotic giant branch stars, pulsars, black holes, white dwarfs, etc.), unveil the structure and evolution of complex systems(such as the Milky Way), benchmark the international celestial reference frame, and reveal cosmic expansion. Furthermore, the theory of general relativity can also be tested with SKA-VLBI using precise measurements of light deflection under the gravitational fields of different solar system objects and the perihelion precession of solar system objects.

关键词： astrometry galaxies: kinematics and dynamics Galaxy: kinematics and dynamics gravitation ISM: kinematics and dynamics parallaxes stars: kinematics and dynamics

Identifying Three New AGNs among Fermi Unidentified Gigaelectronvolt Sources

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Research in Astronomy and Astrophysics 2024年第7期24卷 260-270页

作者： Shun-Hao Ji Zhong-Xiang Wang Qiang-Meng Huang Ruo-Heng Yang Department of Astronomy School of Physics and AstronomyYunnan University Shanghai Astronomical observatory Chinese Academy of Sciences

We report our identification of three gigaelectronvolt γ-ray sources, 4FGL J0502.6+0036, 4FGL J1055.9+6507,and 4FGL J1708.2+5519, as Active Galactic Nuclei(AGNs). They are listed in the latest Fermi-Large Area Telescope source catalog as unidentified ones. We find that the sources all showed γ-ray flux variations in recent years. Using different survey catalogs, we are able to find a radio source within the error circle of each source's position. Further analysis of optical sources in the fields allows us to determine the optical counterparts, which showed similar variation patterns to those seen in γ-rays. The optical counterparts have reported redshifts of 0.6,1.5, and 2.3, respectively, estimated from photometric measurements. In addition, we also obtain an X-ray spectrum of 4FGL J0502.6+0036 and a flux upper limit on the X-ray emission of 4FGL J1055.9+6507 by analyzing the archival data. The broadband spectral energy distributions of the three sources from radio to γ-rays are constructed. Comparing mainly the γ-ray properties of the three sources with those of different sub-classes of AGNs, we tentatively identify them as blazars. Followup optical spectroscopy is highly warranted for obtaining their spectral features and thus verifying the identification.

关键词： (galaxies:) BL Lacertae objects: general (galaxies:) quasars: general gamma-rays: galaxies

Investigation of WZ Sge-type Dwarf Nova ASASSN-19oc: Optical Spectroscopy and Multicolor Light Curve Analysis

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Research in Astronomy and Astrophysics 2024年第8期24卷 22-33页

作者： Viktoriia Krushevska Sergey Shugarov Paolo Ochner Yuliana Kuznyetsova Mykola Petrov Peter Kroll Astronomical Institute of the Slovak Academy of Sciences Main Astronomical observatory of NAS of Ukraine INAF—Osservatorio Astronomico di Padova Department of Physics and Astronomy University of Padova Max Planck Computing and Data Facility (MPCDF) Sonneberg observatory

In this study,we present an investigation of the newly discovered dwarf nova ASASSN-19oc during its superoutburst on 2019 June *** carried out detailed UBVRcIc-photometric observations and also obtained a spectrum on day 7 of the outburst,which shows the presence of hydrogen absorption lines commonly found in dwarf nova *** of photometric data reveals the occurrence of early superhumps in the initial days of observations,followed by ordinary and late *** have accurately calculated the period of the ordinary superhumps as Pord=0.05681（10） days and determined the periods at different stages,as well as the rate of change of the superhump period (Pdot=（5）P/P=8.1×10-5).Additionally,we have derived the mass ratio of the components （q=0.09）,and estimated the color temperature during the outburst as～11,000 K,the distance to the system （d=560 pc） and absolute magnitude of the system in outburst （MV=5.3）.We have shown that outbursts of this star are very rare:based on brightness measurements on 600 archival photographic plates,we found only one outburst that occurred in *** fact,as well as the properties listed above,convincingly shows that the variable ASASSN-19oc is a dwarf nova of WZ Sge type.

关键词： (stars:) binaries (including multiple): close (stars:) novae cataclysmic variables stars: dwarf novae

Design and Application of an S-band Fast Radio Bursts Search Pipeline for the Nanshan 26 m Radio Telescope

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Research in Astronomy and Astrophysics 2024年第7期24卷 114-120页

作者： Yan-Ling Liu Mao-Zheng Chen Jian Li Jian-Ping Yuan Rai Yuen Zhi-Yong Liu Hao Yan Wen-Long Du Nan-Nan Zhai Xinjiang Astronomical observatory Chinese Academy of Sciences Xinjiang Key Laboratory of Microwave Technology University of Chinese Academy of Sciences

Fast radio bursts(FRBs) are among the most studied radio transients in astrophysics, but their origin and radiation mechanism are still unknown. It is a challenge to search for FRB events in a huge amount of observational data with high speed and high accuracy. With the rapid advancement of the FRB research process, FRB searching has changed from archive data mining to either long-term monitoring of the repeating FRBs or all-sky surveys with specialized equipments. Therefore, establishing a highly efficient and high quality FRB search pipeline is the primary task in FRB research. Deep learning techniques provide new ideas for FRB search processing. We have detected radio bursts from FRB 20201124A in the L-band observational data of the Nanshan 26 m radio telescope(NSRT-26m) using the constructed deep learning based search pipeline named dispersed dynamic spectra search(DDSS). Afterwards, we further retrained the deep learning model and applied the DDSS framework to S-band observations. In this paper, we present the FRB observation system and search pipeline using the S-band *** carried out search experiments, and successfully detected the radio bursts from the magnetar SGR J1935+2145and FRB 20220912A. The experimental results show that the search pipeline can complete the search efficiently and output the search results with high accuracy.

关键词： methods: data analysis methods: observational radio continuum: general

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

Enrichment of Chemical Element ^(7)Li in the Rotating Red Clump Star

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Chinese Physics Letters 2024年第8期41卷 121-125页

作者： Fang-Wen Wu Han-Feng Song Qing-Li Li Yun He Xin-Yue Qu Zhuo Han College of Physics Guizhou UniversityGuiyang 550025China Geneva observatory University of GenevaCH-1290 SauvernySwitzerland

About 2 percent of red clump stars are found to be the lithium-rich and thus the surface lithium increases obviously in some red clump *** physical mechanism of the lithium enrichment in these stars has not yet been explained satisfactorily by the evolutionary models of single *** flash induced internal gravity wave mixing(i.e.,IGW)could play a primary role in explaining the red clump star with lithium enrichment and it has a very significant impact on the internal structure and surface compositions of a *** can significantly increase the mixing efficiency of the internal gravity wave because the timescale for the enrichment event has been *** mixing can explain the observed behavior of lithium on red giant stars that are more luminosity than the RGB ***,it has a very small effect on the diffusion of elements because its diffusion coefficient is much smaller than the one of IGW induced mixing after the core helium flash.

关键词： flash stars lithium

Cosmology-Independent Photon Mass Limits from Localized Fast Radio Bursts by Using Artificial Neural Networks

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Chinese Physics Letters 2024年第5期41卷 177-183页

作者：冉景遇王宝魏俊杰 Purple Mountain observatory Chinese Academy of SciencesNanjing 210023China School of Astronomy and Space Sciences University of Science and Technology of ChinaHefei 230026China

A hypothetical photon mass m_(γ) can produce a frequency-dependent vacuum dispersion of light, which leads to an additional time delay between photons with different frequencies when they propagate through a fixed distance. The dispersion measure and redshift measurements of fast radio bursts(FRBs) have been widely used to constrain the rest mass of the photon. However, all current studies analyzed the effect of the frequency-dependent dispersion for massive photons in the standard ΛCDM cosmological context. In order to alleviate the circularity problem induced by the presumption of a specific cosmological model based on the fundamental postulate of the masslessness of photons, here we employ a new model-independent smoothing technique, artificial neural network(ANN), to reconstruct the Hubble parameter H(z) function from 34 cosmic-chronometer *** combining observations of 32 well-localized FRBs and the H(z) function reconstructed by ANN, we obtain an upper limit of m_(γ) ≤ 3.5 × 10^(-51)kg, or equivalently m_(γ) ≤ 2.0 × 10^(-15)eV/c^(2)(m_(γ) ≤ 6.5 × 10^(-51)kg, or equivalently m_(γ) ≤ 3.6 × 10^(-15)eV/c_(2)) at the 1σ(2σ) confidence level. This is the first cosmology-independent photon mass limit derived from extragalactic sources.

关键词： dispersion limit Independent

Disorder effects in NbTiN superconducting resonators

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Chinese Physics B 2024年第2期33卷 482-486页

作者：吕伟涛支强胡洁李婧史生才 Purple Mountain observatory Chinese Academy of SciencesNanjing 210034China GEPI Observatoire de ParisPSL UniversitéCNRSParis 75014France

Disordered superconducting materials like NbTiN possess a high kinetic inductance fraction and an adjustable critical temperature, making them a good choice for low-temperature detectors. Their energy gap(D), critical temperature(T_(c)),and quasiparticle density of states(QDOS) distribution, however, deviate from the classical BCS theory due to the disorder effects. The Usadel equation, which takes account of elastic scattering, non-elastic scattering, and electro–phonon coupling,can be applied to explain and describe these deviations. This paper presents numerical simulations of the disorder effects based on the Usadel equation to investigate their effects on the △, Tc, QDOS distribution, and complex conductivity of the NbTiN film. Furthermore, NbTiN superconducting resonators with coplanar waveguide(CPW) structures are fabricated and characterized at different temperatures to validate our numerical simulations. The pair-breaking parameter α and the critical temperature in the pure state T_(c)^(P) of our NbTiN film are determined from the experimental results and numerical simulations. This study has significant implications for the development of low-temperature detectors made of disordered superconducting materials.

关键词： effects of disorder NbTiN superconducting film Usadel equation complex conductivity superconducting resonator