分类： 天文学 >> 天文学 提交时间： 2023-02-19
Guobin Mou
Dongze Sun
Taotao Fang
Wei Wang
Ruiyu Zhang
Feng Yuan
Yoshiaki Sofue
Tinggui Wang
Zhicheng He
摘要： The eROSITA bubbles are detected via the instrument with the same name. The northern bubble shows noticeable asymmetric features, including distortion to the west and enhancement in the eastern edge, while the southern counterpart is significantly dimmer. Their origins are debated. Here, we performed hydrodynamic simulations showing that asymmetric eROSITA bubbles favor a dynamic, circumgalactic medium wind model, but disfavor other mechanisms such as a non-axisymmetric halo gas or a tilted nuclear outflow. The wind from the east by north direction in Galactic coordinates blows across the northern halo with a velocity of about 200 km s$^{-1}$, and part of it enters the southern halo. This creates a dynamic halo medium and redistributes both density and metallicity within. This naturally explains the asymmetric bubbles in both the morphology and surface brightness. Our results suggest that our Galaxy is accreting low-abundance circumgalactic medium from one side while providing outflow feedback.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Chuan Li
Cheng Fang
Zhen Li
MingDe Ding
PengFei Chen
Ye Qiu
Wei You
Yuan Yuan
MinJie An
HongJiang Tao
XianSheng Li
Zhe Chen
Qiang Liu
Gui Mei
Liang Yang
Wei Zhang
WeiQiang Cheng
JianXin Chen
ChangYa Chen
Qiang Gu
摘要： The Chinese H{\alpha} Solar Explorer (CHASE), dubbed "Xihe" - Goddess of the Sun, was launched on October 14, 2021 as the first solar space mission of China National Space Administration (CNSA). The CHASE mission is designed to test a newly developed satellite platform and to acquire the spectroscopic observations in the H{\alpha} waveband. The H{\alpha} Imaging Spectrograph (HIS) is the scientific payload of the CHASE satellite. It consists of two observational modes: raster scanning mode and continuum imaging mode. The raster scanning mode obtains full-Sun or region-of-interest spectral images from 6559.7 to 6565.9 {\AA} and from 6567.8 to 6570.6 {\AA} with 0.024 {\AA} pixel spectral resolution and 1 minute temporal resolution. The continuum imaging mode obtains photospheric images in continuum around 6689 {\AA} with the full width at half maximum of 13.4 {\AA}. The CHASE mission will advance our understanding of the dynamics of solar activity in the photosphere and chromosphere. In this paper, we present an overview of the CHASE mission including the scientific objectives, HIS instrument overview, data calibration flow, and first results of on-orbit observations.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We conduct a detailed analysis of an M1.3 limb flare occurring on 2017 July 3, which have the X-ray observations recorded by multiple hard X-ray telescopes, including Hard X-ray Modulation Telescope (Insight-HXMT), Ramaty High Energy Solar Spectroscopic Imager (RHESSI), and The Fermi Gamma-ray Space Telescope (FERMI). Joint analysis has also used the EUV imaging data from the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamic Observatory. The hard X-ray spectral and imaging evolution suggest a lower corona source, and the non-thermal broken power law distribution has a rather low break energy $\sim$ 15 keV. The EUV imaging shows a rather stable plasma configuration before the hard X-ray peak phase, and accompanied by a filament eruption during the hard X-ray flare peak phase. Hard X-ray image reconstruction from RHESSI data only shows one foot point source. We also determined the DEM for the peak phase by SDO/AIA data. The integrated EM beyond 10 MK at foot point onset after the peak phase, while the $>$ 10 MK source around reconnection site began to fade. The evolution of EM and hard X-ray source supports lower corona plasma heating after non-thermal energy dissipation. The combination of hard X-ray spectra and images during the limb flare provides the understanding on the interchange of non-thermal and thermal energies, and relation between lower corona heating and the upper corona instability.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： With the rapid development of deep learning technology, more and more researchers apply it to gravitational wave (GW) data analysis. Previous studies focused on a single deep learning model. In this paper we design an ensemble algorithm combining a set of convolutional neural networks (CNN) for GW signal recognition. The whole ensemble model consists of two sub-ensemble models. Each sub-ensemble model is also an ensemble model of deep learning. The two sub-ensemble models treat data of Hanford and Livinston detectors respectively. Proper voting scheme is adopted to combine the two sub-ensemble models to form the whole ensemble model. We apply this ensemble model to all reported GW events in the first observation and second observation runs (O1/O2) by LIGO-VIRGO Scientific Collaboration. We find that the ensemble algorithm can clearly identify all binary black hole merger events except GW170818. We also apply the ensemble model to one month (August 2017) data of O2. There is no false trigger happens although only O1 data are used for training. Our test results indicate that the ensemble learning algorithms can be used in real-time GW data analysis.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Tidal disruption events (TDEs) that occur in active galactic nuclei (AGN) with dusty tori are a special class of sources. TDEs can generate ultrafast and large opening-angle wind, which will almost inevitably collide with the preexisting AGN dusty tori a few years later after the TDE outburst. The wind-torus interactions drive two kinds of shocks: the bow shocks at the windward side of the torus clouds, and the cloud shocks inside the torus clouds. In a previous work, we proved that the shocked clouds will give rise to considerable X-ray emissions which can reach $10^{41-42}$ erg s$^{-1}$ (so called \emph{years delayed X-ray afterglows}). In this work, we focus on the radiations of high energy particles accelerated at both shocks. Benefitting from the strong radiation field at the inner edge of the torus, the inverse Compton scatterings of AGN photons by relativistic electrons at bow shocks dominate the overall gamma-ray radiation. The gamma-ray luminosity can reach $10^{41}~{\rm erg s^{-1}} (L_{\rm kin}/10^{45}{\rm erg s^{-1}})$, where $L_{\rm kin}$ is the kinetic luminosity of TDE wind. Synchrotron radiation at bow shocks contributes to the radio afterglow with a luminosity of 10$^{38-39} ~{\rm erg s^{-1}} (L_{\rm kin}/10^{45}{\rm erg s^{-1}})$ at 1-10 GHz if the magnetic field is 100 mGauss, and extends to infrared with a luminosity of $\sim 10^{39-40}~{\rm erg s^{-1}} (L_{\rm kin}/10^{45}{\rm erg s^{-1}})$. Our scenario provides a prediction of the years delayed afterglows in multiple wavebands for TDEs and reveals their connections.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Cosmic filaments are the largest collapsing structure in the Universe. Recently both observations and simulations inferred that cosmic filaments have coherent angular momenta (spins). Here we use filament finders to identify the filamentary structures in cosmological simulations and study their physical origins, which are well described by the primordial tidal torque of their Lagrangian counterpart regions -- protofilaments. This initial angular momenta statistically preserve their directions to low redshifts. We further show that a spin reconstruction method can predict the spins of filaments and potentially relate their spins to the initial conditions of the Universe. This correlation provides a new way of constraining and obtaining additional information of the initial perturbations of the Universe.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Patrick Huber
Kate Scholberg
Elizabeth Worcester
Jonathan Asaadi
A. Baha Balantekin
Nathaniel Bowden
Pilar Coloma
Peter B. Denton
André de Gouvêa
Laura Fields
Megan Friend
Steven Gardiner
Carlo Giunti
Julieta Gruszko
Benjamin J. P. Jones
Georgia Karagiorgi
Lisa Kaufman
Joshua R. Klein
Lisa W. Koerner
Yusuke Koshio
摘要： This report summarizes the current status of neutrino physics and the broad and exciting future prospects identified for the Neutrino Frontier as part of the 2021 Snowmass Process.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We report the discovery of CXOU J191100-595621 and CXOU J191012-595619, two galaxy clusters serendipitously detected in the direction of globular cluster NGC 6752, based on archival {\it Chandra} observations with a total exposure time of $\sim 344$ ks. The deep {\it Chandra} X-ray data enabled us to measure properties of both systems, which result in a redshift of $z=0.239\pm0.013$ and $z=0.375\pm0.016$, a temperature of $kT=3.32^{+0.57}_{-0.46}$ keV and $kT=3.71^{+1.18}_{-0.86}$ keV, an iron abundance of $Z_{\rm Fe}=0.64^{+0.34}_{-0.29}Z_{\rm Fe\odot}$ and $Z_{\rm Fe}=1.29^{+0.97}_{-0.65}Z_{\rm Fe\odot}$, and a rest-frame full band (0.5-7 keV) luminosity of $L_{\rm X}=9.2^{+1.2}_{-1.1}\times 10^{43} {\rm \, erg\, s^{-1}}$ and $L_{\rm X}=9.9^{+2.7}_{-2.2}\times 10^{43} {\rm \, erg\, s^{-1}}$ for CXOU J191100-595621 and CXOU J191012-595619, respectively. The temperature profile of CXOU J191100-595621 is found to decreases with decreasing radius, indicating a cool core in this cluster. The hydrostatic equilibrium estimation suggests the clusters are moderately weighted, with $M_{500}=(1.3\pm0.4)\times 10^{14}\, M_{\odot}$ and $M_{500}=(2.0\pm1.5)\times 10^{14}\, M_{\odot}$, respectively. We search for optical and radio counterparts of X-ray point sources in the clusters. Three active galactic nuclei are found, among which one is identified with a narrow-angle-tail radio galaxy, and one is found to associated with the brightest central galaxy (BCG) of CXOU J191100-595621.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Satellites are not randomly distributed around their central galaxies but show polar and planar structures. In this paper, we investigate the axis-asymmetry or lopsidedness of satellite galaxy distributions around isolated galaxies in a hydrodynamic cosmological simulation. We find a statistically significant lopsided signal by studying the angular distribution of the satellite galaxies' projected positions around isolated central galaxies in a two-dimensional plane. The signal is dependent on galaxy mass, color and large-scale environment. Satellites that inhabit low-mass blue hosts, or located further from the hosts show the most lopsided signal. Galaxy systems with massive neighbors exhibit stronger lopsidedness. This satellite axis-asymmetry signal also decreases as the universe evolves. Our findings are in agreement with recent observational results, and they provide a useful perspective for studying galaxy evolution, especially on the satellite accretion, internal evolution and interaction with the cosmic large-scale structure.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： As a dedicated solar radioheliograph, the MingantU SpEctral RadioHeliograph (MUSER) has a maximum baseline of more than 3000 meters and a frequency range of 400 MHz -- 15 GHz. According to the classical radio interferometry theory, the non-coplanar baseline effect (i.e., w-term effect) would be considered and calibrated for such a radio instrument. However, little previous literature made the qualitative or quantitative analyses on w-term effects of solar radioheliograph in-depth. This study proposes a complete quantitative analysis of w-term effects for the MUSER. After a brief introduction of the MUSER, we systematically investigate the baseline variations over a year and analyze the corresponding variations of w-term. We further studied the effects of the w-term in the imaging for the specified extended source, i.e., the Sun. We discussed the possible effects of the w-term, such as image distortion and so on. The simulated results show that the w-term is an essential and unavoidable issue for solar radio imaging with high spatial resolution.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Cassiopeia A (Cas A) supernova remnant shows strong radiation from radio to gamma-ray bands. The mechanism of gamma-ray radiation in Cas A and its possible contribution to PeV cosmic rays are still under debate. The X-ray imaging reveals an asymmetric profile of Cas A, suggesting the existence of a jet-like structure. In this work, we propose an asymmetrical model for Cas A, consisting of a fast moving jet-like structure and a slowly expanding isotropic shell. This model can account for the multi-wavelength spectra of Cas A, especially for the power-law hard X-ray spectrum from $\sim$ 60 to 220 keV. The GeV to TeV emission from Cas A should be contributed by both hadronic and leptonic processes. Moreover, the jet-like structure may produce a gamma-ray flux of $\sim 10^{-13}\rm erg\ cm^{-2}\ s^{-1}$ at $\sim 100$ TeV, to be examined by LHAASO and CTA.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
JUNO Collaboration
Jie Zhao
Baobiao Yue
Haoqi Lu
Yufeng Li
Jiajie Ling
Zeyuan Yu
Angel Abusleme
Thomas Adam
Shakeel Ahmad
Rizwan Ahmed
Sebastiano Aiello
Muhammad Akram
Abid Aleem
Tsagkarakis Alexandros
Fengpeng An
Qi An
Giuseppe Andronico
Nikolay Anfimov
Vito Antonelli
摘要： The physics potential of detecting $^8$B solar neutrinos is exploited at the Jiangmen Underground Neutrino Observatory (JUNO), in a model independent manner by using three distinct channels of the charged-current (CC), neutral-current (NC) and elastic scattering (ES) interactions. Due to the largest-ever mass of $^{13}$C nuclei in the liquid-scintillator detectors and the potential low background level, $^8$B solar neutrinos would be observable in the CC and NC interactions on $^{13}$C for the first time. By virtue of optimized event selections and muon veto strategies, backgrounds from the accidental coincidence, muon-induced isotopes, and external backgrounds can be greatly suppressed. Excellent signal-to-background ratios can be achieved in the CC, NC and ES channels to guarantee the $^8$B solar neutrino observation. From the sensitivity studies performed in this work, we show that one can reach the precision levels of 5%, 8% and 20% for the $^8$B neutrino flux, $\sin^2\theta_{12}$, and $\Delta m^2_{21}$, respectively, using ten years of JUNO data. It would be unique and helpful to probe the details of both solar physics and neutrino physics. In addition, when combined with SNO, the world-best precision of 3% is expected for the $^8$B neutrino flux measurement.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The Mingantu Spectral Radioheliograph (MUSER), a new generation of solar dedicated radio imaging-spectroscopic telescope, has realized high-time, high-angular, and high-frequency resolution imaging of the sun over an ultra-broadband frequency range. Each pair of MUSER antennas measures the complex visibility in the aperture plane for each integration time and frequency channel. The corresponding radio image for each integration time and frequency channel is then obtained by inverse Fourier transformation of the visibility data. In general, the phase of the complex visibility is severely corrupted by instrumental and propagation effects. Therefore, robust calibration procedures are vital in order to obtain high-fidelity radio images. While there are many calibration techniques available -- e.g., using redundant baselines, observing standard cosmic sources, or fitting the solar disk -- to correct the visibility data for the above-mentioned phase errors, MUSER is configured with non-redundant baselines and the solar disk structure cannot always be exploited. Therefore it is desirable to develop alternative calibration methods in addition to these available techniques whenever appropriate for MUSER to obtain reliable radio images. In the case that a point-like calibration source containing an unknown position error, we have for the first time derived a mathematical model to describe the problem and proposed an optimization method to calibrate this unknown error by studying the offset of the positions of radio images over a certain period of the time interval. Simulation experiments and actual observational data analyses indicate that this method is valid and feasible. For MUSER's practical data the calibrated position errors are within the spatial angular resolution of the instrument. This calibration method can also be used in other situations for radio aperture synthesis observations.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Tidal disruption event (TDE) can launch an ultrafast outflow. If the black hole is surrounded by large amounts of clouds, outflow-cloud interaction will generate bow shocks, accelerate electrons and produce radio emission. Here we investigate the interaction between a non-relativistic outflow and clouds in active galaxies, which is manifested as outflow-BLR (broad line region) interaction, and can be extended to outflow-torus interaction. This process can generate considerable radio emission, which may account for the radio flares appearing a few months later after TDE outbursts. Benefitting from efficient energy conversion from outflow to shocks and the strong magnetic field, outflow-cloud interaction may play a non-negligible, or even dominating role in generating radio flares in a cloudy circumnuclear environment if the CNM density is no more than 100 times the Sgr A*-like one. In this case, the evolution of radio spectra can be used to directly constrain the properties of outflows.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Guobin Mou
Dongze Sun
Taotao Fang
Wei Wang
Ruiyu Zhang
Feng Yuan
Yoshiaki Sofue
Tinggui Wang
Zhicheng He
摘要： The eROSITA bubbles are detected via the instrument with the same name. The northern bubble shows noticeable asymmetric features, including distortion to the west and enhancement in the eastern edge, while the southern counterpart is significantly dimmer. Their origins are debated. Here, we performed hydrodynamic simulations showing that asymmetric eROSITA bubbles favor a dynamic, circumgalactic medium wind model, but disfavor other mechanisms such as a non-axisymmetric halo gas or a tilted nuclear outflow. The wind from the east by north direction in Galactic coordinates blows across the northern halo with a velocity of about 200 km s$^{-1}$, and part of it enters the southern halo. This creates a dynamic halo medium and redistributes both density and metallicity within. This naturally explains the asymmetric bubbles in both the morphology and surface brightness. Our results suggest that our Galaxy is accreting low-abundance circumgalactic medium from one side while providing outflow feedback.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Fan Yang
Wei Wang
Xing Wei
Hui Zhang
Ji-Lin Zhou
Su-Su Shan
Jie Zheng
Wei-Kai Zong
Ming Yang
Yu Bai
Song Wang
Jia-Chen Zheng
Yu-Ru Xu
Yu-Feng Li
You-Jun Lu
Ji-Feng Liu
摘要： Transit Timing Variation (TTV) of hot Jupiters provides direct observational evidence of planet tidal dissipation. Detecting tidal dissipation through TTV needs high precision transit timings and long timing baselines. In this work, we predict and discuss the potential scientific contribution of SiTian Survey in detecting and analyzing exoplanet TTV. We develop a tidal dissipation detection pipeline for SiTian Survey that aims at time-domain astronomy with 72 1-meter optical telescopes. The pipeline includes the modules of light curve deblending, transit timing obtaining, and TTV modeling. SiTian is capable to detect more than 25,000 exoplanets among which we expect $\sim$50 sources showing evidence of tidal dissipation. We present detection and analysis of tidal dissipating targets, based on simulated SiTian light curves of XO-3b and WASP-161b. The transit light curve modeling gives consistent results within 1$\sigma$ to input values of simulated light curves. Also, the parameter uncertainties predicted by Monte-Carlo Markov Chain are consistent with the distribution obtained from simulating and modeling the light curve 1000 times. The timing precision of SiTian observations is $\sim$ 0.5 minutes with one transit visit. We show that differences between TTV origins, e.g., tidal dissipation, apsidal precession, multiple planets, would be significant, considering the timing precision and baseline. The detection rate of tidal dissipating hot Jupiters would answer a crucial question of whether the planet migrates at an early formation stage or random stages due to perturbations, e.g., planet scattering, secular interaction. SiTian identified targets would be constructive given that the sample would extend tenfold.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Jian Ge
Hui Zhang
Weicheng Zang
Hongping Deng
Shude Mao
Ji-Wei Xie
Hui-Gen Liu
Ji-Lin Zhou
Kevin Willis
Chelsea Huang
Steve B. Howell
Fabo Feng
Jiapeng Zhu
Xinyu Yao
Beibei Liu
Masataka Aizawa
Wei Zhu
Ya-Ping Li
Bo Ma
Quanzhi Ye
摘要： We propose to develop a wide-field and ultra-high-precision photometric survey mission, temporarily named "Earth 2.0 (ET)". This mission is designed to measure, for the first time, the occurrence rate and the orbital distributions of Earth-sized planets. ET consists of seven 30cm telescopes, to be launched to the Earth-Sun's L2 point. Six of these are transit telescopes with a field of view of 500 square degrees. Staring in the direction that encompasses the original Kepler field for four continuous years, this monitoring will return tens of thousands of transiting planets, including the elusive Earth twins orbiting solar-type stars. The seventh telescope is a 30cm microlensing telescope that will monitor an area of 4 square degrees toward the galactic bulge. This, combined with simultaneous ground-based KMTNet observations, will measure masses for hundreds of long-period and free-floating planets. Together, the transit and the microlensing telescopes will revolutionize our understandings of terrestrial planets across a large swath of orbital distances and free space. In addition, the survey data will also facilitate studies in the fields of asteroseismology, Galactic archeology, time-domain sciences, and black holes in binaries.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Yongheng Zhou
Kaiyue He
Huamin Hu
Gang Ouyang
Chao Zhu
Wei Wang
Sichen Qin
Ye Tao
Runfeng Chen
Le Zhang
Run Shi
Chun Cheng
Han Wang
Yanjun Liu
Zheng Liu
Taihong Wang
Wei Huang
Lin Wang
Xiaolong Chen
摘要： Magneto-optical effect has been widely used in light modulation, optical sensing and information storage. Recently discovered two-dimensional (2D) van der Waals layered magnets are considered as promising platforms for investigating novel magneto-optical phenomena and devices, due to the long-range magnetic ordering down to atomically-thin thickness, rich species and tunable properties. However, majority 2D antiferromagnets suffer from low luminescence efficiency which hinders their magneto-optical investigations and applications. Here, we uncover strong light-magnetic ordering interactions in 2D antiferromagnetic MnPS3 utilizing a newly-emerged near-infrared photoluminescence (PL) mode far below its intrinsic bandgap. This ingap PL mode shows strong correlation with the Neel ordering and persists down to monolayer thickness. Combining the DFT, STEM and XPS, we illustrate the origin of the PL mode and its correlation with Neel ordering, which can be attributed to the oxygen ion-mediated states. Moreover, the PL strength can be further tuned and enhanced using ultraviolet-ozone treatment. Our studies offer an effective approach to investigate light-magnetic ordering interactions in 2D antiferromagnetic semiconductors.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： When considered as orthogonal bases in distinct vector spaces, the unit vectors of polarization directions and the Laguerre-Gaussian modes of polarization amplitude are inseparable, constituting a so-called classical entangled light beam. Equating this classical entanglement to quantum entanglement necessary for computing purpose, we show that the parallelism featured in Shor's factoring algorithm is equivalent to the concurrent light-path propagation of an entangled beam or pulse train. A gedanken experiment is proposed for executing the key algorithmic steps of modular exponentiation and Fourier transform on a target integer $N$ using only classical manipulations on the amplitudes and polarization directions. The multiplicative order associated with the sought-after integer factors is identified through a four-hole diffraction interference from sources obtained from the entangled beam profile. The unique mapping from the fringe patterns to the computed order is demonstrated through simulations for the case $N=15$.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Simultaneous wireless information and power transfer (SWIPT) is a remarkable technology to support both the data and the energy transfer in the era of Internet of Things (IoT). In this paper, we proposed a long-range optical wireless information and power transfer system utilizing retro-reflectors, a gain medium, a telescope internal modulator to form the resonant beam, achieving high-power and high-rate SWIPT. We adopt the transfer matrix, which can depict the beam modulated, resonator stability, transmission loss, and beam distribution. Then, we provide a model for energy harvesting and data receiving, which can evaluate the SWIPT performance. Numerical results illustrate that the proposed system can simultaneously supply 0$\sim$9 W electrical power and 18 bit/s/Hz spectral efficiency over 20 m distance.
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