Fermi, Swift, and other observation satellites provided a dataset of 323 Long Gamma-Ray Bursts (LGRBs) with known redshift and well-defined spectral parameters spanning from February 1997 to September 2023. Among these, 123 GRBs (Gamma-Ray Bursts) observed by Fermi-GBM were selected to calibrate the relationship between the isotropic energy Eiso and the peak energy in the cosmological rest frame Ep,i, known as the Amati relation. The analysis revealed that the Eiso of five LGRBs (GRB 980425, GRB 061210, GRB 070714B, GRB 071227, and GRB 080123A) significantly deviated from the Amati relation, suggesting that the jet of them may be off-axis to the line of sight. Utilizing the well-established Eiso−Ep,i and Lorentz factor Γ−Eiso correlations, we estimated the viewing angles θobs′ for these five LGRBs. The results show, θobs′=(0.42−0.14+0.29)∘ for GRB 980425, θobs′=(0.27−0.10+0.21)∘ for GRB 061210, θobs′=(0.10−0.02+0.09)∘ for GRB 070714B, θobs′=(0.13−0.05+0.09)∘ for GRB 071227, and θobs′=(0.12−0.03+0.14)∘ for GRB 080123A. Notably, all five θobs′ values are small, with the maximum angle being 0.42∘ for GRB 980425, the nearest long burst observed (z=0.0085). The results suggest that the majority of Long GRBs are likely detected on-axis, with only a small fraction of nearby Long GRBs being observed slightly outside the jet edge.
当前宇宙学研究已进入精密测量时代,含宇宙学常数的冷暗物质模型ΛCDM被广泛认为是宇宙学的标准模型. 然而,哈勃常数危机、S8危机、詹姆斯·韦伯太空望远镜(JWST)发现的极高红移超大质量星系等观测现象挑战了该模型. 基于此,本文利用引力波探测和JWST高红移观测等最新数据,围绕宇宙学危机问题开展相关研究.
With the development and readiness of inter-satellite link (ISL), it has been widely used in satellite constellations for navigation, communication, and other purposes. As establishing or maintaining ISL can be affected by transits (also known as sun outage), transits of the links need to be calculated and predicted, so the system service can be properly assessed and scheduled. Currently the normal practice to determine and predict the transits, by building scenarios using proven commercial satellite system toolkit or by developing in-house simulation tools, is to calculate the elongation between the ISL and the line-of-sight of the Sun, based on propagated ephemerides. It is simple, straight forward and can be conveniently implemented, however, it bears a significant disadvantage that the computation is extremely CPU-intensive and therefore slow in speed. Although the predicted transits do not have to be very precise in the design phase and the two-body model may suffice, the ephemerides are always limited to small stepsize in order to properly detect the transits. Otherwise transits with short duration may be missed, and the service assessment can be compromised. Regarding the determination and calculation of the transits, a fast algorithm is proposed in this paper. With the equation of the satellite's argument of latitude u at the transit boundary, it can be analytically determined whether a transit may occur or calculated when the transit starts or ends, allowing fast assessment of how transits affect the service. This method is also based on propagated ephemerides, but a much larger stepsize can be accepted. Tests show that the analytical method can outperform the normal practice by detecting more transits while reducing calculation time by two to three orders of magnitude. Even the stepsize of the ephemerides is close to one orbital period, this method is still able to detect more than 99.9% transits. The results are robust against varying stepsizes, where the maximum deviations of calculated start epochs and durations of the transits would not exceed 1 second.
Since the development of planetary science,more than 5000 exoplanets have been discovered.Understanding the evolution of protoplanetary disks is essential to clarify the classification of exoplanets and improve the efficiency of exoplanet detection.At the same time,exoplanet observations can be used to constrain and examine the physical parameters of the interaction between the protoplanetary disk and the planet.Therefore,in this paper,the surface density of the protoplanetary disk is linked to the star mass,combined with the distribution of exoplanet properties,and the interaction process between planets with different masses and specific protoplanetary disks is simulated by using the fluid dynamics code FARGO3D.Simulation results show that:(1)there is a power-law relationship between the relative surface density of the gap structure and the mass of the planet,and the power-law exponent has a strong correlation with the mass of the star;(2)there is a power-law relationship between the duration of the gap structure and the mass of the planet,and the power-law exponent has a weak correlation with the mass of the star;(3)there is a log-linear relationship between the width of the gap structure and the mass of the planet,and the power-law exponent has a weak correlation with the mass of the star.That is,the strength of the interaction between the planet and the protoplanetary disk is not only reflected in the relative surface density of the gap structure in the stable state,but also in the duration and width of the gap structure.
Using the high-resolution data in the TiO band taken by the 1 m New Vacuum Solar Telescope(NVST)at the Fuxian Lake Solar Observatory(FSO),we statistically investigated the effects of different magnetic field structures within the photosphere on granules via the newly developed algorithms for identifying granules.The data of NVST have much higher contrast(9.6％),therefore which is helpful for identifying smaller granules and performing more detailed analyses and studies than before.It is found that two critical scales of granules,D1 and D2,exist,and that the probability density of the equivalent diameter of granules with scales smaller than D1 follows a power law distribution similar to the Kolmogorov spectrum.We classify granules into three groups of different origins:the granules smaller than D1 are turbulent,those larger than D2 are convective,and those with scales between D1 and D2 result from blending of turbulence and convection,which is an intermediate case of the two formers.Meanwhile,we also noticed that the different magnetic field structures within the photosphere impact the critical scale,D1,of the turbulent granule in an apparent way such that the stronger the nearby magnetic field is,the smaller the value of D1 is.On the other hand,magnetic field imposes almost no effect on the mean radiative intensity of its external granules and the corresponding distribution features.
Measuring the interference fringes of scientific and tracking targets simultaneously within an equal optical path angle in the atmosphere can result in the accuracy of astrometry at the micro-arcsecond level through precise optical path difference measurement between the two interference fringes.A phase measurement method based on spatial modulation is proposed for high-precision astrometry using the long baseline stellar interferometer.Synchronous phase shifting is achieved through polarization modulation,providing phase level optical path difference measurement.And the accuracy of optical path difference detection is further improved through multiple measurements and statistical averaging.This article demonstrates the feasibility of the phase detection method through numerical simulation and experiments,with detection accuracy better than 1/18 wavelength and optical path difference statistical measurement accuracy better than 5 nm.Furthermore,the source of error is analyzed through environmental disturbance measurement,laying a technical foundation for achieving the established scientific goal of China's under construction hundred meter long baseline interferometer.
The Fe Low-ionization Broad Absorption Line Quasar (FeLoBALQ) is one of the rarest types of all quasars. Quasars blow out the surrounding violently, forming extreme outflows from which low ionized elements e.g. Fe provide the absorbing feature in FeLoBALQ spectra. Carrying high kinetic energy, the outflows of FeLoBALQ may possibly be enough for powering the M−σ* relationship between the supermassive black hole mass M and the host-galaxy bulge velocity dispersion σ*. On the other hand, evidence has been found for the co-existence of FeLoBALQ with hosts' starburst or recent major merger. However, the FeLoBALQ sample collected so far is not large enough to stand for these theories statistically. This research focuses on digging out hidden FeLoBALQs from large quasar surveys, forming a FeLoBALQ catalog large enough for statistical and physical analyze. Adopting Convolutional Neural Network (CNN) method, 160 FeLoBALQs are newly identified from totally 50931 quasars in the SDSS (Sloan Digital Sky Survey) DR7Q (Data Release 7 Quasar catalog) in the redshift range of 0.8 <z< 2.125, with previous identified FeLoBALQ spectra as training sample. The FeLoBALQs' color is found redder than normal quasars, and previously identified FeLoBALQs are lightly redder than newly identified ones; these differences are more obvious on bluer end than on redder end, and nearly disappear in mid-infrared band. The proportion of FeLoBALQs out of all quasars given is 0.43%, higher than previous prediction, but may still be underestimated. Further researches may expand this method to larger samples e.g. SDSS DR16Q (Data Release 16 Quasar catalog) for larger FeLoBALQ sample, which may help to answer the questions of the relationship between FeLoBALQ and host galaxy star formation, FeLoBALQ and galaxy major merger, and the coevolution of galaxies and central supermassive black holes.
The detection of dark matter remains a paramount scientific objective in modern astronomy and physics.Axions from Quantum Chromodynamics(QCD)have emerged as natural candidates for dark matter due to their theoretical properties.Currently,efforts are focused on detecting axions with micro-electronvolt mass using electromagnetic responses in GHz-band microwave cavities,but these experiments have yielded null results.Therefore,it is imperative to explore detection strategies for lower-mass axions.This paper addresses the need for detecting lighter axions with sub-electronvolt mass by discussing the design and optimization of tunable microwave cavities in the hundreds of MHz band.The study explores the optimal resonant modes,shape factors,and frequency scanning rates for these cavities.Numerical simulations indicate that the proposed eight-rod cavity structure increases the scanning rate nearly a hundredfold compared to standard cavities in the same frequency band,with a reduction in axion detection sensitivity by only about threefold.Although the results presented are based on numerical simulations and require experimental validation,this research offers a forward-looking reference for constructing future experimental setups for QCD axion electromagnetic response detection in the sub-GHz frequency band.
Track-Catalogue correlation is the precondition and foundation of large scale space object cataloging maintenance.The accuracy of correlation not only affects normal cataloging processing,but also affects the utilization of observation data and the effectiveness of space object surveillance system.In this paper,a method is put forward to improve the correlation accuracy of large-batch orbital track data.Firstly,based on the characteristics of orbit error propagation,a model is constructed to estimate the orbital prediction time error and to correct observation residual,aiming to transfer the large scale spatial error to a small scale time-domain error.Secondly,a correlation judgement model involving a four-parameter-joint feature vector is proposed,with threshold setting guidelines and a data correlation processing flow followed.Finally,some examples with regard to large-batch simulated and actual measured tracks are checked to illustrate the effectiveness of the method.
In view of the current situation of inconsistent conclusions among existing asteroid impact monitoring systems, the linear approximation method used in the change line impact monitoring system was studied, and the conclusion is achieved that the deviation of the orbit distribution relative to the theoretical orbit distribution obtained by this method gradually became significant as the orbit propagation time increased. The impact probability of 6 asteroid instances was calculated using the Monte Carlo method. Compared with the results of the existing Monte Carlo impact monitoring system, the maximum difference is 2.1 times the standard deviation. The impact samples of asteroid 2020 VV in October 2056 are analyzed in detail, and the distribution of impact samples with time and space is depicted, and the conclusions are consistent with those of existing impact monitoring systems. As for the comparison between the different impact monitoring systems, it is concluded that the Monte Carlo impact monitoring system and the change line impact monitoring system currently have their own advantages and disadvantages: the former does not introduce the error caused by the linear approximation method, but the computational cost is high. The linear approximation method used in the latter will bring errors, but it can find some virtual impact sources with low impact probability that may be missed by the former, and the computational cost is relatively low.
Compared with normal pulsars,millisecond pulsars are a class of neutron stars with faster rotation speed,and the pulse signals emitted by them have extremely high stability.The stability of the polarization profile of pulsars is one of the important issues in the study of pulsar radiation mechanism and interstellar medium properties.The polarization profile stability of three millisecond pulsars PSR J1022+1001,PSR J1730-2304 and PSR J2129-5721 was studied using the observation data of the Parkes 64 m telescope in Australia.Analysis of the observations shows that the polarization profile changes slightly at different times.The reasons for the changes are analyzed and the possible explanations are proposed,including the effect of the interstellar scintillation and the instability of the intrinsic properties of the pulsars.
The effects of non-Newtonian gravity on the properties of color-flavor-locked strange quark stars are studied using the standard MIT bag model. It is shown that the maximum mass of color-flavor-locked strange quark stars increases not only with the increasing of the value of color-superconducting energy gap, but also with the increasing of the non-Newtonian gravity parameter. Moreover, color-superconducting energy gap and non-Newtonian gravity parameter are constrained by the mass of the second component of the GW190814 event (M= 2.6 M⊙). It turns out that Mmax> 2.6 M⊙ (Mmax is the maximum mass of the stars) can be satisfied only if Δ> 94.5 MeV (Δ is the color-superconducting energy gap) without the consideration of non-Newtonian gravity effects. However, if non-Newtonian gravity effects are included, smaller values of Δ could satisfy Mmax> 2.6 M⊙. Since small color-superconducting energy gap is favored by the surface temperature observation of the central compact object in Hess J1731-347 supernova remnant, the inclusion of non-Newtonian gravity effects is helpful in the explanation of the observed large mass of the second component of the GW190814 event.
When describing the motion of a spacecraft using traditional elliptical orbital elements, if its orbit changes from elliptical to hyperbolic, it becomes difficult to continue the calculation. In order to address this issue, improvements are made upon classical elliptical orbital elements, utilizing a set of orbital elements applicable to any conic section to integrate the equation of motion. The set of elements is applicable for any eccentricity e⩾0 and inclination 0⩽i<180∘, with the singularity occurring only for i=180∘. The basic conversion formulas and equations of perturbed motion are provided. Subsequently, orbit predictions for cislunar objects are conducted, and the results are compared with calculations using Cartesian. The findings indicate that the results obtained from these orbital elements are sufficiently accurate, and the computational efficiency is advantageous when the changes in the elements are not particularly drastic. In addressing the issue of the singularity at i=180∘ that may arise in the practical application of orbital elements, various workarounds are proposed, including changing state variables and fixing integration step sizes, and their applicability is assessed.
J1846-0513 is a millisecond pulsar discovered by the Five-hundred-meter Aperture Spherical radio Telescope (FAST) which is established by China. Data analysis of observation reveals that the pulsar is harbored in a binary with orbital period of Porb= 0.613 d and eccentricity of e=0.208. According to the theory of binary evolution, its eccentricity originates from an asymmetric supernova explosion during which the second neutron star was born. Together with the observed parameters of component mass, the binary is assumed to be a double neutron star system candidate. Considering its importance to understand the evolution of stars and binaries, in current work, we simulated the evolution of neutron star – helium (He) star system with initial mass of 1.345M⊙ and 2.8M⊙, respectively, and initial orbital period of 0.5 day. At the end of the simulation, the total mass of the He star is reduced to 1.556M⊙ with a carbon-oxygen core with mass of 1.431M⊙. A silicon core of mass 0.846M⊙ and an iron/neutron-rich core of mass 0.086M⊙ formed in the He star which illustrate it will end with core collapse supernova, and born a neutron star with mass of measured lower limit. Subsequent simulation of dynamical effects of the supernova explosion indicates that current model may evolve to the observed eccentric double neutron star candidate.
Before being used for scientific research, images obtained by solar telescopes with digital detectors must be corrected for flat-field, which reflects the non-uniformity coming from the non-uniform transmission efficiency of optical components and response of detector pixels. That means flat-field correction is a necessary step in the pipe-line of high-level scientific data. As one of the three payloads of the Kuafu-1 (Advanced Space-based Solar Observatory: ASO-S, Chinese name Kuafu-1) mission, the Lyman-alpha Solar Telescope (LST) consists of three scientific instruments: including a dual-waveband Solar Corona Imager (SCI), and two full-disk solar telescopes which are named the White-light Solar Telescope (WST) and the Solar Disk Imager (SDI). The WST and the SDI use Complementary Metal-Oxide-Semiconductor (CMOS) as image sensors, and the main feature of the flat field is the stripe structure which is caused by laser annealing. When used in the ultraviolet wavelengths, CMOS sensors will be subject to certain degradation and radiation damage, as well as the pollution of water vapor condensation and organic matter accumulation, which will have some influence on the obtained flat field. This paper mainly presents the dither pattern and its optimization used by the WST and the SDI in the in-flight flat field calibration since the launch of the ASO-S mission on 2022 October 9, the computed flat field images and their evolution during the period. We also briefly present the degradation and the radiation damage of the detectors in the WST and the SDI over time.
The Chinese Survey Space Telescope(CSST)is expected to characterize the atmospheres of exoplanets,providing new opportunities for exoplanet observations.At present,the atmospheres of exoplanets have mostly been studied by transmission spectroscopy.However,evidence of stellar activity has been found in several observed transmission spectra,and the results show that it is difficult to accu-rately constrain the stellar contamination.Therefore,how to accurately distinguish and eliminate stellar contamination has become a major challenge in transmission spectroscopy.Consequently,a quantitative as-sessment of the potential stellar contamination and its distinguishability is required when selecting targets for follow-up transmission spectroscopy observations,which requires large-scale simulations to provide the expected data.Here we use multi-color photometry combined with machine learning to identify potential stellar contamination in the transmission spectra of extrasolar gas planets,and design a filter combi-nation with the highest accuracy for stellar contamination discrimination for the CSST Multi-Channel Imager(MCI),which can provide options for developing observing strategies for follow-up observations of exoplanet atmospheric targets.
This paper centers on the technical problem of aperture coupling of multi-layer shielding cavity, and carries out the research on the influence of aperture coupling on the shielding effectiveness to provide technical support for the electromagnetic compatibility design of large radio telescopes. Based on Robinson model and electromagnetic topology theory, this paper establishes the equivalent circuit of a double-layer perforated shielding cavity and its signal flow diagram, and solves the shielding effectiveness using the BLT (Baum-Liu-Tesch) equation, taking into account the case of a 3-layer cavity. The accuracy of the measurement results, simulation values, Robinson's algorithm and this paper's algorithm are compared and analyzed, and the accuracy of this paper's algorithm is verified. On this basis, this method is used to analyze the influence of the layer spacing, the shape of the hole, and the installation position of the radiation source on the shielding effectiveness of the double-layer metal cavity in the 0–1.5 GHz band, and the engineering suggestions are given. In addition, the relationship between the number of layers of the three-layer shielding cavity and the shielding effectiveness is analyzed. The results show that there is a linear relationship between the shielding effectiveness and the number of layers.
Obtaining an accurate distribution map of lunar water hydrogen has significant scientific value for research on detecting water ice and for future deep space exploration. In order to effectively explore the water ice resources on the Moon, it is necessary to accurately detect their distribution. In practical applications, a point spread function with shifting characteristics is constructed based on the detection principle of neutron detectors and the process of satellite image degradation, due to the lack of effective and reliable image sources. The point spread function is based on the kappa function. The image is blurred and made noisy to create a simulated detection image. Then, the maximum entropy algorithm and Richardson-Lucy algorithm are utilized to reconstruct the simulated detection image. The evaluation criteria for comparative study include visual effect, chi-square test, and authenticity test. The experimental results show that direct reconstruction cannot achieve optimal reconstruction results under both low and high levels of noise. After applying denoising preprocessing, ensuring the safety of the chi-square test, the overall effect of the reconstruction results is found to be better than before preprocessing. Additionally, there is a significant reduction in the number of points with large deviation in the authenticity test of the reconstructed image. This indicates that the reconstruction results are now more accurate and reliable. It will provide more accurate data support for the exploration of water ice resources and deep space exploration.
Here we review the six-year Galactic plane scanning survey of the Insight-HXMT(Insight Hard X-ray Modulation Telescope),focusing on the monitoring results and analysis of the known X-ray sources on the Galactic plane.During the first six years of its orbital operation,Insight-HXMT spent approximately 1/4 to 1/3 of its total observation time conducting over 3000 scanning observations of the Galactic plane in the wide energy range of 1-100 keV.Long-term flux monitoring was carried out for>1300 different types of X-ray sources(detecting X-ray signals from approximately 200 celestial bodies),and the monitoring results were compiled and analyzed,including the activity and spectral characteristics of different types of celestial bodies.This paper first introduces the data characteristics and data analysis methods of the Insight-HXMT scanning observations(direct demodulation imaging and light curves fitting),then provides an overall description of the monitoring results of the Insight-HXMT's scanning survey,and finally presents a statistical analysis of the nature of the monitored sources,such as spatial distribution characteristics,variability activity analysis,and hardness ratio analysis.
A large amount of important astrophysical results has been achieved with Insight Hard X-ray Modulation Telescope(Insight-HXMT)since its launch in June 2017.So far Insight-HXMT has been operating smoothly in orbit and is expected to continue to operate in several more years.The purpose of this special issue is to allow a more comprehensive understanding by the Chinese astronomical community on the capability of Insight-HXMT,in order to continue to explore its scientific potential,especially in light of the fact that a series of domestic high-energy astrophysical missions have been launched recently or in development.The 11 papers cover most of the research progresses to date with Insight-HXMT.
