Subjects: Astronomy >> Celestial Mechanics Subjects: Physics >> Geophysics, Astronomy, and Astrophysics submitted time 2024-05-16
Abstract： This paper presents a systematic improvement in celestial dynamics theory by introducing a new symmetric form of particle dynamics equation. For open multi-body systems, the symmetric new equation can be applied to any translational reference frame, thus avoiding the need for inertial reference frame approximations and enhancing the accuracy of theoretical predictions. In the case of bound multi-body systems, applying the symmetric new equation allows for an extremely simplified derivation of the planetary perturbation equation in one step. Furthermore, by considering temporary thrust or impact forces acting on planets, or even considering any external forces acting on the bound system further to enhance the computational precision, a new correction equation is now established for the planetary perturbation that can be further imposed with non-perturbative interactions. This will assist in the prediction of the trajectory of asteroids affected by external forces and in the accurate calculation of the orbit of satellites.
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Subjects: Information Science and Systems Science >> Basic Disciplines of Information Science and Systems Science Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics Subjects: Electronics and Communication Technology >> Optoelectronics and Laser Subjects: Physics >> Geophysics, Astronomy, and Astrophysics Subjects: Physics >> The Physics of Elementary Particles and Fields submitted time 2024-04-08
Abstract： The Einstein’s theory of special relativity is based on his two postulates. The first is that the laws of physics are the same in all inertial reference frames. The second is that the velocity of light in the vacuum is the same in all inertial frames. The theory of special relativity is considered to be supported by a large number of experiments. This paper revisits the two postulates according to the new interpretations to the exact solutions of moving sources in the laboratory frame. The exact solutions are obtained using the classic Maxwell’s theory, which clearly show that the propagation velocity of the electromagnetic waves of moving sources in the vacuum is not isotropic; the propagation velocity of the electromagnetic waves and the moving velocity of the sources cannot be added like vectors; the transverse Doppler effect is intrinsically included in the fields of the moving sources. The electromagnetic sources are subject to the Newtonian mechanics, while the electromagnetic fields are subject to the Maxwell’s theory. We argue that since their behaviors are quite different, it is not a best choice to try to bind them together and force them to undergo the same coordinate transformations as a whole, like that in the Lorentz transformations. Furthermore, the Maxwell’s theory does not impose any limitations on the velocity of the electromagnetic waves. To assume that all objects cannot move faster than the light in the vacuum need more examinations. We have carefully checked the main experiment results that were considered as supporting the special relativity. Unfortunately, we found that the experimental results may have been misinterpreted. We here propose a Galilean-Newtonian-Maxwellian relativity, which can give the same or even better explanations to those experimental results.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics Subjects: Physics >> Geophysics, Astronomy, and Astrophysics submitted time 2024-02-29
Abstract： It is hypothesized that, though atomic nuclei are made of nucleons, strongly interacting matter with baryon number from $A simeq 10^{3-9}$ to $ sim 10^{57}$ would be composed of strangeons if Nature favors always the flavor symmetry of quarks. According to that logic, strangeon matter with $A sim 10^{57}$ could manifest in the form of pulsar-like compact stars, and multi-messenger observations with advanced facilities (e.g., China’s FAST) could eventually provide a disproof/proof. It is worth emphasizing that this point of view, based on established “old physics”, may have particular consequences for understanding our material world, for both normal luminous matter and the dark sector.
Peer Review Status:Awaiting Review
Subjects: Physics >> Geophysics, Astronomy, and Astrophysics submitted time 2024-02-01 Cooperative journals: 《Research in Astronomy and Astrophysics》
Abstract： To address the problem of real-time processing of ultra-wide bandwidth pulsar baseband data, we designed and implemented a pulsar baseband data processing algorithm (PSRDP) based on GPU parallel computing technology. PSRDP can perform operations such as baseband data unpacking, channel separation, coherent dedispersion, Stokes detection, phase and folding period prediction, and folding integration in GPU clusters. We tested the algorithm using the J0437-4715 pulsar baseband data generated by the CASPSR and Medusa backends of the Parkes, and the J0332+5434 pulsar baseband data generated by the self-developed backend of the NanShan Radio Telescope. We obtained the pulse profiles of each baseband data. Through experimental analysis, we have found that the pulse profiles generated by the PSRDP algorithm in this paper are essentially consistent with the processing results of Digital Signal Processing Software for Pulsar Astronomy (DSPSR), which verified the effectiveness of the PSRDP algorithm. Furthermore, using the same baseband data, we compared the processing speed of PSRDP with DSPSR, and the results showed that PSRDP was not slower than DSPSR in terms of speed. The theoretical and technical experience gained from the PSRDP algorithm research in this article lays a technical foundation for the real-time processing of QTT (Qi Tai radio Telescope) ultra-wide bandwidth pulsar baseband data.
Subjects: Physics >> Geophysics, Astronomy, and Astrophysics submitted time 2024-02-01 Cooperative journals: 《Research in Astronomy and Astrophysics》
Abstract： We present resolved Giant Metrewave Radio Telescope H i observations of the high gas-phase metallicity dwarf galaxy WISEA J230615.06+143927.9 (z = 0.005) (hereafter J2306) and investigate whether it could be a Tidal Dwarf Galaxy (TDG) candidate. TDGs are observed to have higher metallicities than normal dwarfs. J2306 has an unusual combination of a blue g − r color of 0.23 mag, irregular optical morphology and high-metallicity (12 + log(O/H) = 8.68 ± 0.14), making it an interesting galaxy to study in more detail. We find J2306 to be an H i rich galaxy with a large extended, unperturbed rotating H i disk. Using our H i data we estimated its dynamical mass and found the galaxy to be dark matter (DM) dominated within its H i radius. The quantity of DM, inferred from its dynamical mass, appears to rule out J2306 as an evolved TDG. A wide area environment search reveals J2306 to be isolated from any larger galaxies which could have been the source of its high gas metallicity. Additionally, the H i morphology and kinematics of the galaxy show no indication of a recent merger to explain the high-metallicity. Further detailed optical spectroscopic observations of J2306 might provide an answer to how a seemingly ordinary irregular dwarf galaxy achieved such a high level of metal enrichment.
Subjects: Physics >> Geophysics, Astronomy, and Astrophysics submitted time 2024-02-01 Cooperative journals: 《Research in Astronomy and Astrophysics》
Abstract： Recently, a new radio millisecond pulsar (MSP) J1740−5340B, hosted in the globular cluster (GC) NGC 6397, was reported with a 5.78 ms spin period in an eclipsing binary system with a 1.97 days orbital period. Based on a modified radio ephemeris updated by tool tempo2, we analyze the ∼15 yr γ-ray data obtained from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope and detect PSR J1740−5340B's γ-ray pulsation at a confidence level of ∼4σ with a weighted H-test value of ∼26. By performing a phase-resolved analysis, the γ-ray luminosity in on-pulse interval of PSR J1740−5340B is Lγ ∼ 3.8 × 1033 erg s−1 using NGC 6397's distance of 2.48 kpc. And γ-rays from the on-pulse part of PSR J1740−5340B contribute ∼90% of the total observed γ-ray emissions from NGC 6397. No significant γ-ray pulsation of another MSP J1740−5340A in the GC is detected. Considering that the previous four cases of MSPs in GCs, more data in γ-ray, X-ray, and radio are encouraged to finally confirm the γ-ray emissions from MSP J1740−5340B, especially starving for a precise ephemeris.
Subjects: Physics >> Geophysics, Astronomy, and Astrophysics submitted time 2024-02-01 Cooperative journals: 《Research in Astronomy and Astrophysics》
Abstract： In this paper, new light curves (LCs) of contact eclipsing binary (CEB) systems LX Lyn and V0853 Aur are presented and analyzed by using the 2015 version of the Wilson–Devinney (W-D) code. In order to explain their asymmetric LCs, cool starspots on the components were employed. It is suggested that their fill-out degrees are f = 12.0% (LX Lyn) and f = 26.3% (V0853 Aur). At the same time, we found that LX Lyn is a W-type eclipsing binary (EB) with an orbital inclination of i = 8488 and a mass ratio of q = 2.31. V0853 Aur is also a W-type CEB with a mass ratio of q = 2.77 and an orbital inclination of i = 7926. Based on all available times of light minimum, their orbital period changes are studied by using the O − C method. The O − C diagram of LX Lyn reveals a cyclic oscillation with a period of about 14.84 yr and an amplitude of 0.0019 days, which can be explained by the light-travel time effect (LTTE) due to the presence of a third body with a minimum mass of 0.06M⊙. For V0853 Aur, it is discovered that the O − C diagram of the system also shows a cyclic oscillation with a period of 9.64 yr and an amplitude of 0.03365 days. The cyclic oscillation of V0853 Aur can be attributed to the LTTE by means of a third body with a mass no less than 3.77M⊙. The third body may play an important role in the formation and evolution of these systems.
Subjects: Physics >> Geophysics, Astronomy, and Astrophysics submitted time 2024-02-01 Cooperative journals: 《Research in Astronomy and Astrophysics》
Abstract： The radio telescope possesses high sensitivity and strong signal collection capabilities. While receiving celestial radiation signals, it also captures Radio Frequency Interferences (RFIs) introduced by human activities. RFI, as signals originating from sources other than the astronomical targets, significantly impacts the quality of astronomical data. This paper presents an RFI fast mitigation algorithm based on block Least Mean Square (LMS) algorithm. It enhances the traditional adaptive LMS filter by grouping L adjacent time-sampled points into one block and applying the same filter coefficients for filtering within each block. This transformation reduces multiplication calculations and enhances algorithm efficiency by leveraging the time-domain convolution theorem. The algorithm is tested using baseband data from the Parkes 64 m radio telescope's pulsar observations and simulated data. The results confirm the algorithm's effectiveness, as the pulsar profile after RFI mitigation closely matches the original pulsar profile.
Subjects: Physics >> Geophysics, Astronomy, and Astrophysics submitted time 2024-02-01 Cooperative journals: 《Research in Astronomy and Astrophysics》
Abstract： As the second of Earth's Trojan asteroids, 2020 XL5 is worthy of rendezvous and even sample return missions in many aspects. In this paper, a rendezvous mission to Earth's second Trojan asteroid 2020 XL5 is proposed. However, due to its high inclination and large eccentricity, direct impulsive transfer requires large amounts of fuel consumption. To address this challenge, we explore the benefits of electric propulsion and multi-gravity assist techniques for interplanetary missions. These two techniques are integrated in this mission design. The design of a low-thrust gravity-assist (LTGA) trajectory in multi-body dynamics is thoroughly investigated, which is a complex process. A comprehensive framework including three steps is presented here for optimization of LTGA trajectories in multi-body dynamics. The rendezvous mission to 2020 XL5 is designed with this three-step approach. The most effective transfer sequence among the outcomes involves Earth–Venus–Earth–Venus-2020 XL5. Numerical results indicate that the combination of electric propulsion and multi-gravity assists can greatly reduce the fuel consumption, with fuel consumption of 9.03%, making it a highly favorable choice for this rendezvous mission.
Subjects: Physics >> Geophysics, Astronomy, and Astrophysics submitted time 2024-02-01 Cooperative journals: 《Research in Astronomy and Astrophysics》
Abstract： The simulation of radio frequency interference (RFI) cancellation by applying a spatial filtering technique for phased array feed (PAF) is presented. In order to better reflect the characteristics of PAF, a new signal model is to add the coupling coefficient among elements of PAF to the conventional array signal model. Then the subspace projection (SP) algorithm is used to cancel RFI from the correlation matrix of the signal, and finally, the 2D power image is drawn. The power variation of signal-of-interest direction and RFI direction before and after using the SP algorithm is analyzed. The new signal model and simulation strategy can be used to test and verify the beamformer.
Subjects: Physics >> Geophysics, Astronomy, and Astrophysics submitted time 2024-02-01 Cooperative journals: 《Research in Astronomy and Astrophysics》
Abstract： We present a study of low surface brightness galaxies (LSBGs) selected by fitting the images for all the galaxies in α.40 SDSS DR7 sample with two kinds of single-component models and two kinds of two-component models (disk+bulge): single exponential, single sérsic, exponential+deVaucular (exp+deV), and exponential+sérsic (exp+ser). Under the criteria of the B band disk central surface brightness and the axis ratio b/a > 0.3, we selected four none-edge-on LSBG samples from each of the models which contain 1105, 1038, 207, and 75 galaxies, respectively. There are 756 galaxies in common between LSBGs selected by exponential and sérsic models, corresponding to 68.42% of LSBGs selected by the exponential model and 72.83% of LSBGs selected by the sérsic model, the rest of the discrepancy is due to the difference in obtaining μ0between the exponential and sérsic models. Based on the fitting, in the range of 0.5 ≤ n ≤ 1.5, the relation of μ0 from two models can be written as . The LSBGs selected by disk+bulge models (LSBG_2comps) are more massive than LSBGs selected by single-component models (LSBG_1comp), and also show a larger disk component. Though the bulges in the majority of our LSBG_2comps are not prominent, more than 60% of our LSBG_2comps will not be selected if we adopt a single-component model only. We also identified 31 giant low surface brightness galaxies (gLSBGs) from LSBG_2comps. They are located at the same region in the color–magnitude diagram as other gLSBGs. After we compared different criteria of gLSBGs selection, we find that for gas-rich LSBGs, M⋆ > 1010M⊙ is the best to distinguish between gLSBGs and normal LSBGs with bulge.
Subjects: Physics >> Geophysics, Astronomy, and Astrophysics submitted time 2024-02-01 Cooperative journals: 《Research in Astronomy and Astrophysics》
Abstract： With the development of cutting-edge multi-object spectrographs, fiber positioners located in the focal plane are being scaled down in size, and miniature hollow-cup Permanent Magnet motors are now being considered as a suitable replacement for Faulhaber Precistep stepper motors. However, the small electrical time constant of such coreless motors poses a challenge, as the problem of severe commutation torque ripple in a fiber positioner running a position loop has been tricky. To overcome this challenge, it is advised to increase the Pulse Width Modulation (PWM) frequency as much as possible to mitigate the effects of the current fluctuation. This must be done while ensuring adequate resolution of the PWM generator. By employing a voltage open-loop field-oriented control based on a modulation frequency of 1 MHz, the drive current only costs 25 mA under a 3.3 V power supply. The sine degree of phase current is immaculate, and the repeat positioning accuracy can reach 2 μm. Moreover, it is possible to further shrink the bill of devices and the layout area of the Printed Circuit Board, especially in size-sensitive applications. This device has been developed under the new generation of The Large Sky Area Multi-Object Fiber Spectroscopic Telescope.
Subjects: Physics >> Geophysics, Astronomy, and Astrophysics submitted time 2024-02-01 Cooperative journals: 《Research in Astronomy and Astrophysics》
Abstract： Fast radio bursts (FRBs) are short pulses observed in radio frequencies usually originating from cosmological distances. The discovery of FRB 200428 and its X-ray counterpart from the Galactic magnetar SGR J1935+2154 suggests that at least some FRBs can be generated by magnetars. However, the majority of X-ray bursts from magnetars are not associated with radio emission. The fact that only in rare cases can an FRB be generated raises the question regarding the special triggering mechanism of FRBs. Here we report long time spin evolution of SGR J1935+2154 until the end of 2022. According to ν and , the spin evolution of SGR J1935+2154 could be divided into two stages. The first stage evolves relatively steady evolution until 2020 April 27. After the burst activity in 2020, the spin of SGR J1935+2154 shows strong variations, especially for . After the burst activity in 2022 October, a new spin-down glitch with Δν/ν = (–7.2 ± 0.6) × 10−6 is detected around MJD 59876, which is the second event in SGR J1935+2154. At the end, spin frequency and pulse profile do not show variations around the time of FRB 200428 and radio bursts 221014 and 221021, which supply strong clues to constrain the trigger mechanism of FRBs or radio bursts.
Subjects: Physics >> Geophysics, Astronomy, and Astrophysics submitted time 2024-02-01 Cooperative journals: 《Research in Astronomy and Astrophysics》
Abstract： Gamma-ray bursts (GRBs) are among the brightest objects in the Universe and, hence, can be observed up to a very high redshift. Properly calibrated empirical correlations between intensity and spectral correlations of GRBs can be used to estimate the cosmological parameters. However, the possibility of the evolution of GRBs with redshift is a long-standing puzzle. In this work, we used 162 long-duration GRBs to determine whether GRBs below and above a certain redshift have different properties. The GRBs are split into two groups, and we fit the Amati relation for each group separately. Our findings demonstrate that estimations of the Amati parameters for the two groups are substantially dissimilar. We perform simulations to investigate whether the selection effects could cause the difference. Our analysis shows that the differences may be either intrinsic or due to systematic errors in the data, and the selection effects are not their true origin. However, in-depth analysis with a new data set comprised of 119 long GRBs shows that intrinsic scatter may partly be responsible for such effects.
Subjects: Physics >> Geophysics, Astronomy, and Astrophysics submitted time 2024-02-01 Cooperative journals: 《Research in Astronomy and Astrophysics》
Abstract： The thermal gradient is an important factor that causes degradation to the image quality of telescopes. In order to ensure the accurate alignment of the primary focus unit and the primary mirror, the hexapod platform (as a corrector) is investigated in this paper. First, a ground-based telescope with 2.5 m aperture and 3.5 deg field of view is described. The telescope is under construction, and it is expected to be finished in 2023. Second, the hexapod platform with flexure hinges utilized to adjust the primary focus unit is proposed, which is applied as a corrector. Then, the inverse kinematics of the platform is established and an open-loop control system is built based on it. Finally, the cryogenic performance test for the hexapod platform is performed. The experimental results show that the resolution and repeatability of the translation for the hexapod platform can be achieved at the micrometer level. The resolution and repeatability of the rotation can be achieved at the arc-second level. Therefore, the cryogenic performance of the hexapod platform can meet the optical imaging requirements of the wide-field ground-based telescope. The kinematic analysis and cryogenic performance tests in the paper provide a technical reference for the precise alignment of the primary focus unit and the primary mirror, which can improve the imaging quality of the telescope.
Subjects: Physics >> Geophysics, Astronomy, and Astrophysics submitted time 2024-02-01 Cooperative journals: 《Research in Astronomy and Astrophysics》
Abstract： The Giant Radio Array for Neutrino Detection (GRAND) is a proposed large-scale observatory designed to detect cosmic rays, gamma-rays, and neutrinos with energies exceeding 100 PeV. The GRANDProto300 experiment is proposed as the early stage of the GRAND project, consisting of a hybrid array of radio antennas and scintillator detectors. The latter, as a mature and traditional detector, is used to cross-check the nature of the candidate events selected from radio observations. In this study, we developed a simulation software called G4GRANDProto300, based on the Geant4 software package, to optimize the spacing of the scintillator detector array and to investigate its effective area. The analysis was conducted at various zenith angles under different detector spacings, including 300, 500, 600, 700, and 900 m. Our results indicate that, for large zenith angles used to search for cosmic-ray in the GRAND project, the optimized effective area is with a detector spacing of 500 m. The G4GRANDProto300 software that we developed could be used to further optimize the layout of the particle detector array in future work.
Subjects: Physics >> Geophysics, Astronomy, and Astrophysics submitted time 2024-02-01 Cooperative journals: 《Research in Astronomy and Astrophysics》
Abstract： I analyze a new X-ray image of the youngest supernova remnant (SNR) in the Galaxy, which is the type Ia SNR G1.9+0.3, and reveal a very clear point-symmetrical structure. Since explosion models of type Ia supernovae (SNe Ia) do not form such morphologies, the point-symmetrical morphology must come from the circumstellar material (CSM) into which the ejecta expands. The large-scale point-symmetry that I identify and the known substantial deceleration of the ejecta of SNR G1.9+0.3 suggest a relatively massive CSM of ≳1M⊙. I argue that the most likely explanation is the explosion of this SN Ia into a planetary nebula. The scenario that predicts a large fraction of SN Ia inside PNe (SNIPs) is the core degenerate scenario. Other SN Ia scenarios might lead to only a very small fraction of SNIPs or none at all.
Subjects: Physics >> Geophysics, Astronomy, and Astrophysics submitted time 2024-02-01 Cooperative journals: 《Research in Astronomy and Astrophysics》
Abstract： During the long term evolution of globular clusters (GCs), some member stars are lost to the field. The recently found nitrogen-rich (N-rich) metal-poor field stars are promising candidates of these GC escapees, since N enhancement is the fingerprint of chemically enhanced populations in GCs. In this work, we discuss the possibility of identifying N-rich metal-poor field stars with the upcoming Chinese Space Station Telescope (CSST). We focus on the main survey camera with NUV, u, g, r, i, z, y filters and slitless spectrograph with a resolution about 200. The combination of UV sensitive equipment and prominent N-related molecular lines in the UV band bodes well for the identification: the color–color diagram of (u − g) versus (g − r) is capable of separating N-rich field stars from normal halo stars, if metallicity can be estimated without using the information on u-band photometry. Besides, the synthetic spectra show that a signal-to-noise ratio of 10 is sufficient to identify N-rich field stars. In the near future, a large sample of N-rich field stars found by CSST, combined with state-of-the-art N-body simulations will be crucial to deciphering GC-Galaxy co-evolution.
Subjects: Physics >> Geophysics, Astronomy, and Astrophysics submitted time 2024-02-01 Cooperative journals: 《Research in Astronomy and Astrophysics》
Abstract： Leighton Chajnantor Telescope (LCT), i.e., the former Caltech Submillimeter Observatory telescope, will be refurbished at the new site in Chajnantor Plateau, Chile in 2023. The environment of LCT will change significantly after its relocation, and the telescope will be exposed to large wind disturbances directly because its enclosure will be completely open during observation. The wind disturbance is expected to be a challenge for LCT's pointing control since the existing control method cannot reject this disturbance very well. Therefore, it is very necessary to develop a new pointing control method with good capability of disturbance rejection. In this research, a disturbance observer—based composite position controller (DOB-CPC) is designed, in which an H∞ feedback controller is employed to compress the disturbance, and a feedforward linear quadratic regulator is employed to compensate the disturbance precisely based on the estimated disturbance signal. Moreover, a controller switching policy is adopted, which applies the proportional controller to the transient process to achieve a quick response and applies the DOB-CPC to the steady state to achieve a small position error. Numerical experiments are conducted to verify the good performance of the proposed pointing controller (i.e., DOB-CPC) for rejecting the disturbance acting on LCT.
Subjects: Physics >> Geophysics, Astronomy, and Astrophysics submitted time 2024-02-01 Cooperative journals: 《Research in Astronomy and Astrophysics》
Abstract： A significant excess of the stellar mass density at high redshift has been discovered from the early data release of James Webb Space Telescope (JWST), and it may require a high star formation efficiency. However, this will lead to large number density of ionizing photons in the epoch of reionization (EoR), so that the reionization history will be changed, which can arise tension with the current EoR observations. Warm dark matter (WDM), via the free streaming effect, can suppress the formation of small-scale structure as well as low-mass galaxies. This provides an effective way to decrease the ionizing photons when considering a large star formation efficiency in high-z massive galaxies without altering the cosmic reionization history. On the other hand, the constraints on the properties of WDM can be derived from the JWST observations. In this work, we study WDM as a possible solution to reconcile the JWST stellar mass density of high-z massive galaxies and reionization history. We find that, the JWST high-z comoving cumulative stellar mass density alone has no significant preference for either CDM or WDM model. But using the observational data of other stellar mass density measurements and reionization history, we obtain that the WDM particle mass with keV and star formation efficiency parameter in 2σ confidence level can match both the JWST high-z comoving cumulative stellar mass density and the reionization history.
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