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Prospects of the Multi-channel Photometric Survey Telescope in the Cosmological Application of Type Ia Supernovae

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Research in Astronomy and Astrophysics 2024年第4期24卷 183-191页

作者： Zhenyu Wang Jujia Zhang Xinzhong Er Jinming Bai Yunnan Observatories Chinese Academy of SciencesKunming 650216China University of Chinese Academy of Sciences Beijing 100049China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China International Centre of Supernovae Yunnan Key LaboratoryKunming 650216China South-Western Institute for Astronomy Research Yunnan UniversityKunming 650500China

The Multi-channel Photometric Survey Telescope(Mephisto)is a real-time,three-color photometric system designed to capture the color evolution of stars and transients *** telescope system can be crucial in cosmological distance measurements of low-redshift(low-z,z■0.1)Type Ia supernovae(SNe Ia).To optimize the capabilities of this instrument,we perform a comprehensive simulation study before its official operation is scheduled to *** considering the impact of atmospheric extinction,weather conditions,and the lunar phase at the observing site involving the instrumental features,we simulate light curves of SNe Ia obtained by *** best strategy in the case of SN Ia cosmology is to take the image at an exposure time of 130 s with a cadence of 3 *** this condition,Mephisto can obtain hundreds of high-quality SNe Ia to achieve a distance measurement better than 4.5%.Given the on-time spectral classification and monitoring of the Lijiang 2.4 m Telescope at the same observatory,Mephisto,in the whole operation,can significantly enrich the well-calibrated sample of supernovae at low-z and improve the calibration accuracy of high-z SNe Ia.

关键词： (stars:)supernovae:general (cosmology:)cosmological parameters telescopes

Compact objects in close orbits as Gravitational Wave Sources: Formation Scenarios and Properties

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arXiv 2024年

作者： Li, Zhenwei Chen, Xuefei Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Science Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China

Gravitational Waves (GWs) provide a unique way to explore our Universe. The ongoing ground-based detectors, e.g., LIGO, Virgo, and KAGRA, and the upcoming next-generation detectors, e.g., Cosmic Explorer and Einstein Telescope, as well as the future space-borne GW antennas, e.g., LISA, TianQin, and TaiJi, cover a wide range of GW frequencies from ∼ 10−4 Hz to ∼ 103 Hz and almost all types of compact objects in close orbits serve as the potential target sources for these GW detectors. The synergistic multi-band GW and EM observations would allow us to study fundamental physics from stars to cosmology. The formation of stellar GW sources has been extensively explored in recent years, and progress on physical processes in binary interaction has been made as well. Furthermore, some studies have shown that the progress in binary evolution may significantly affect the properties of the stellar GW sources. In this article, we review the formation channels of compact objects in close orbits and discuss their implications for GW observations. Copyright © 2024, The Authors. All rights reserved.

关键词： Gravity waves

Optical and X-Ray Observations of MAXI J1820+070 During the Early Outburst Phase in 2018:Zooming in the Low Frequency QPOs

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Research in Astronomy and Astrophysics 2022年第4期22卷 106-113页

作者： Dong-Ming Mao Wen-Fei Yu Ju-Jia Zhang Zhen Yan Stefano Rapisarda Xiao-Feng Wang Jin-Ming Bai Shanghai Astronomical Observatory Chinese Academy of SciencesShanghai 200030China University of Chinese Academy of Sciences Beijing 100049China Yunnan Observatories Chinese Academy of SciencesKunming 650011China Key Laboratory for the Structure and Evolution of Celestial Objects CASKunming 650216China Physics Department Tsinghua UniversityBeijing 100084China Beijing Planetarium Beijing Academy of Sciences and TechnologyBeijing 100044China

We report a further investigation of the optical low frequency quasi periodic oscillations(LF QPOs)detected in the black hole transient MAXI J1820+070 in the 2018 observations with the YFOSC mounted on Lijiang 2.4 m telescope(LJT).In addition,we make use of the Insight-HXMT/HE observations to measure the properties of the quasi-simultaneous X-ray LF QPOs of MAXI J1820+070 on the same *** compared the centroid frequency,the full width at half maximum(FWHM)and the fractional rms of the LF QPOs in both wavelength *** found that the centroid frequency of the optical QPO is at a frequency of 51.58 m Hz,which is consistent with that of the X-ray LF QPO detected on the same day within 1 m *** also found that the FWHM of the optical LF QPO is significantly smaller than that of the X-ray LF QPO,indicating that the optical QPO has a higher *** quasi-simultaneous optical and the X-ray LF QPO at a centroid frequency of about 52 m Hz suggests that the actual mechanisms of these LF QPOs as the Lense-Thirring precession should work in the vicinity of a radius of about 80-117 gravitational radii(R_(g)=GM/c^(2),M is the mass of the black hole)from the black hole if the QPO frequency is related to a proxy of the orbital frequency in the accretion fiow as the Lense-Thirring precession model ***,the apparent higher coherence of the optical QPO favors that it is a more original signal as compared with the X-ray QPO.

关键词： X-ray stars Low mass binary stars X-ray transient sources

Investigation into the origin of the soft excess in Ark 564 using principal component analysis

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arXiv 2024年

作者： Lyu, Ming Fei, Zhenyan Zhang, Guobao Yang, X.J. Department of Physics Xiangtan University Hunan Xiangtan411105 China Key Laboratory of Stars and Interstellar Medium Xiangtan University Hunan Xiangtan411105 China Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China

We combined a principal component analysis (PCA) and spectroscopy to investigate the origin of the soft excess in narrow-line Seyfert 1 galaxy Ark 564 with XMM-Newton observations over a period of ten years. We find that the principal components in different epochs are very similar, suggesting stable variability patterns in this source. More importantly, although its spectra could be equally well fitted by the two soft excess models, simulations show that the principal components from the relativistically smeared reflection model match the data well. At the same time, the principal components from the warm corona model show significant inconsistency. This finding indicates that the soft excess in Ark 564 originates from the relativistically smeared reflection, rather than the Comptonization in the warm corona, thereby favoring the reflection origin or the "hybrid" origin of the soft excess. Furthermore, the presence of the narrow absorption features in the spectra suggests that the soft excess is unlikely to originate from absorptions due to possible outflowing winds. Our results indicate that the PCA coupled with spectral analysis is a promising approach to exploring the origin of the soft excess in active galactic nuclei (AGNs). © 2024, CC BY-NC-ND.

关键词： Principal component analysis

Characterization of the regimes of hydrodynamic escape from low-mass exoplanets

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arXiv 2024年

作者： Guo, J.H. Yunnan Observatories Chinese Academy of Sciences P.O. Box 110 Kunming650011 China University of CAS Beijing China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650011 China

The hydrodynamic escape driven by external or internal energy sources sculpts the population of low mass close-in planets. However, distinguishing between the driving mechanisms responsible for the hydrodynamic escape of hydrogen-rich atmospheres is a complex task due to the involvement of many physical factors. My simulations show that the hydrodynamic escape can be driven solely by thermal energy deposited in the lower layers of the atmosphere due to the heat flux originating from the planetary core or bolometric heating from the star even in the absence of other energy sources, as long as the planet’s Jeans parameter is below 3. Otherwise, stellar extreme ultraviolet irradiation or tidal forces are necessary in driving the escape, which means that the Jeans parameter is incapable of distinguishing the driving mechanisms, as it is only related to the properties of planet. Here, an upgraded Jeans parameter that takes into account tidal forces is introduced, which allows us to accurately categorize the driving mechanisms. The results show that when the upgraded Jeans parameter falls below 3 or exceeds 6, the atmospheric escape is primarily driven by tidal forces or extreme ultraviolet radiation from the host star, respectively. In the range of 3 to 6, both factors can trigger the escape of the atmosphere. I find that planets with high gravitational potential and low stellar irradiation are more likely to undergo subsonic escape, although transonic escape is prevalent among most planets. Moreover, the ionization status is significantly dependent on the gravitational potential. The upgraded Jeans parameter, which is closely related to the underlying physics, provides a concise method to categorize the driving mechanisms of hydrodynamic escape. The results can be applied to planetary evolution calculations. © 2024, CC BY.

关键词： Hydrodynamics

Galaxy Morphology Classification Using Multi-Scale Convolution Capsule Network

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arXiv 2023年

作者： Li, Guangping Xu, Tingting Li, Liping Gao, Xianjun Liu, Zhijing Cao, Jie Yang, Mingcun Zhou, Weihong School of Mathematics and Computer Science Yunnan Minzu University Kunming650504 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy China of Sciences Kunming650011 China

The classification of galaxy morphology is a hot issue in astronomical research. Although significant progress has been made in the last decade in classifying galaxy morphology using deep learning technology, there are still some deficiencies in spatial feature representation and classification accuracy. In this study, we present a multi-scale convolutional capsule network (MSCCN) model for the classification of galaxy morphology. First, this model improves the convolutional layers through using a multi-branch structure to extract multi-scale hidden features of galaxy images. In order to further explore the hidden information in the features, the multi-scale features are encapsulated and fed into the capsule layer. Second, we use a sigmoid function to replace the softmax function in dynamic routing, which can enhance the robustness of MSCCN. Finally, the classification model achieving 97% accuracy, 96% precision, 98% recall, and 97% F1-score under macroscopic averaging. In addition, a more comprehensive model evaluation were accomplished in this study. We visualized the morphological features for the part of sample set, which using the t-distributed stochastic neighbor embedding (t-SNE) algorithm. The results shows that the model has the better generalization ability and robustness, it can be effectively used in the galaxy morphological classification. © 2023, CC BY.

关键词： Galaxies

Binary Stars in the New Millennium

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arXiv 2023年

作者： Xuefei, Chen Zhengwei, Liu Zhanwen, Han Yunnan Observatories The Chinese Academy of Sciences Kunming650296 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China

Binary stars are as common as single stars. Binary stars are of immense importance to astrophysicists because that they allow us to determine the masses of the stars independent of their distances. They are the cornerstone of the understanding of stellar evolutionary theory and play an essential role in cosmic distance measurement, galactic evolution, nucleosynthesis and the formation of important objects such as cataclysmic variable stars, X-ray binaries, Type Ia supernovae, and gravitational wave-producing double compact objects. In this article, we review the significant theoretical and observational progresses in addressing binary stars in the new millennium. Increasing large survey projects have led to the discovery of enormous numbers of binary stars, which enables us to conduct statistical studies of binary populations, and therefore provide unprecedented insight into the stellar and binary evolution physics. Meanwhile, the rapid development of theoretical concepts and numerical approaches for binary evolution have made a substantial progress on the alleviation of some long-standing binary-related problems such as the stability of mass transfer and common envelope evolution. Nevertheless, it remains a challenge to have a full understanding of fundamental problems of stellar and binary astrophysics. The upcoming massive survey projects and increasingly sophisticated computational methods will lead to future progress. © 2023, CC BY.

关键词： Mass transfer

The first photometric investigations of the G-type shallow contact binary IO Cnc

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Research in Astronomy and Astrophysics 2021年第2期21卷 133-141页

作者： Wen-Ping Liao Lin-Jia Li Xiao Zhou Qi-Shan Wang Yunnan Observatories Chinese Academy of SciencesKunming 650216China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China Center for Astronomical Mega-Science Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China

IO Cnc was classified to be a new G-type(G0)W UMa-type eclipsing binary *** first multicolor photometric solutions show that IO Cnc is a new W-subtype shallow contact binary with a fill-out factor of f=16.1%and a low mass ratio of q=3.12(or 1/q=0.32).During orbital period investigations,a cyclic variation and a downward parabolic variation with a rate of(-1.28±0.43)×10^(-7) d yr^(-1) was discovered in the observed–calculated(O-C)*** cyclic variation was analyzed by the light travel time effect(LTTE)via a potential red dwarf companion star,an orbital semi-major axis shorter than 4.88±0.82 AU was ***,we collect physical parameters of a sample of 50 G-type shallow contact binaries(f≤20%),it is suggested that most of the G-type shallow contact binaries are undergoing a longterm and periodic orbital period changes,especially more systems show long-term *** long-term orbital period decrease indicates that IO Cnc is in a mass transferring from the more massive component to the less massive *** the long-term decrease of the orbital period,this shallow contact binary will evolve into a deeper contact one.

关键词： stars binaries close-stars binaries eclipsing-stars individual(IOCnc)-stars solar-type-stars evolution

Radial stellar populations of AGN-host dwarf galaxies in SDSS-Ⅳ MaNGA survey

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Research in Astronomy and Astrophysics 2021年第8期21卷 203-219页

作者： Wei Cai Ying-He Zhao Jin-Ming Bai Yunnan Observatories Chinese Academy of SciencesKunming 652016China University of Chinese Academy of Sciences Beijing 100049China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China Center for Astronomical Mega-Science Chinese Academy of SciencesBeijing 100101China

Based on MaNGA integral field unit(IFU) spectroscopy we search 60 AGN candidates,which have stellar masses M*≤5 × 10^(9) M⊙ and show AGN ionization signatures in the BPT *** these AGN candidates,we derive the spatially resolved stellar population with the stellar population synthesis code STARLIGHT and measure the gradients of the mean stellar age and *** find that the gradients of mean stellar age(metallicity) of individual AGN-host dwarfs are diverse in 0-0.5 Re,0.5-1 Re and 0-1 ***,the overall behavior of the mean stellar age(metallicity) profiles tend to be flat,as the median values of the gradients are close to *** further study the overall behavior of the mean stellar age(metallicity) by plotting the co-added radial profiles for the AGN sample and compare with a control sample with similar stellar *** find that the median values of light-weighted mean stellar ages of the AGN sample are as old as 2-3 Gyr within 2 Re,which are about 4-7 times older than those of the control ***,most of the AGN candidates are low-level AGNs,as only eight sources have L[OⅢ]>1039.5 erg s^(-1).Hence,the AGNs in dwarf galaxies might accelerate the evolution of galaxies by accelerating the consumption of the gas,resulting in an overall quenching of the dwarf galaxies,and the AGNs also become weak due to the lack of *** median values of mass-weighted mean stellar age of both samples within 2 Re are similar and as old as about 10 Gyr,indicating that the stellar mass is mainly contributed by old stellar *** gradients of co-added mean stellar metallicity for both samples tend to be negative but close to zero,and the similar mean stellar metallicity profiles for both samples indicate that the chemical evolution of the host galaxy is not strongly influenced by the AGN.

关键词： galaxies:dwarf galaxies:active galaxies:galaxies stellar content