分类： 天文学 >> 天文学 提交时间： 2024-12-06 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： In spite of the importance of studying the cosmic generation of heavy elements through the r-process, the detection of a kilonova resulting from the merger of a neutron star binary is still a challenging task. In this paper, we show that the Visible Telescope (VT) onboard the ongoing SVOM space mission is powerful for identifying kilonova candidates associated with short gamma-ray bursts up to a distance of 600 Mpc. A significant color variation, turning blue and then turning red, is revealed by calculating the light curves in both red and blue channels of VT by a linear combination of an afterglow and an associated kilonova. The maximum color variation is as high as ∼0.5–1 mag, which is far larger than the small photometry error of ∼0.2 mag of VT for a point source with a brightness of 23 mag. Up to a distance of 600 Mpc, ∼1–2 kilonova candidates per year are predicted to be identified by VT.
分类： 天文学 >> 天文学 提交时间： 2024-05-10 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： The triggering mechanism for radio lobes from late-type galaxies is not fully understood. More samples are desired for a thorough investigation and statistics. By utilizing the optical data from the newly released Dark Energy Spectroscopic Instrument imaging surveys and the radio sources from the NRAO VLA Sky Survey and the Faint Images of the Radio Sky at Twenty-centimeter, we identify four Late-type Galaxies with double Radio Lobes (LaGRLs): J0217−3645, J0947+6220, J1412+3723 and J1736+5108. Including previously known LaGRLs, we confirm the correlation between radio power P1.4 GHz and stellar mass M* of host galaxies. Most (25/35) LaGRLs belong to the blue cloud galaxies, while the newly identified cases in this work are located within the region of the red sequence. We find a clear correlation between the differential radio power, i.e., the offset from the P1.4 GHz − M* relation, and the galaxy color, indicating that bluer galaxies at a fixed M* tend to host more powerful radio lobes. Furthermore, the majority (31/36) of LaGRLs are either located in a galaxy group or displaying a disturbed morphology. We suggest that all of the galaxy mass, color and surrounding environment could play important roles in triggering radio lobes in late-type galaxies.
分类： 天文学 >> 天文学 提交时间： 2025-02-25 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： Binary millisecond pulsars with a massive white dwarf (WD) companion are intermediate-mass binary pulsars (IMBPs). They are formed via the Case BB Roche-lobe overflow evolution channel if they are in compact orbits with an orbital period of less than 1 day. They are fairly rare in the known pulsar population; only five such IMBPs have been discovered before, and one of them is in a globular cluster. Here we report six IMBPs in compact orbits: PSRs J0416+5201, J0520+3722, J1919+1341, J1943+2210, J1947+2304 and J2023+2853, discovered during the Galactic Plane Pulsar Snapshot survey by using the Five-hundred-meter Aperture Spherical radio Telescope, doubling the number of such IMBPs due to the high survey sensitivity in the short survey time of 5 minutes. Follow-up timing observations show that they all have either a CO WD or an ONeMg WD companion with a mass greater than about 0.8 M⊙ in a very circular orbit with an eccentricity in the order of ≲10−5. PSR J0416+5201 should be an ONeMg WD companion with a remarkable minimum mass of 1.28 M⊙. These massive WD companions lead to a detectable Shapiro delay for PSRs J0416+5201, J0520+3722, J1943+2210, and J2023+2853, indicating that their orbits are highly inclined. From the measurement of the Shapiro delay, the pulsar mass of J1943+2210 was constrained to be 1.84
分类： 天文学 >> 天文学 提交时间： 2025-06-13 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： Imaging is an important method for astronomy research. In practice, original images acquired by a telescope are often convolved and blurred by the point-spread function (PSF), which is a very unfavorable situation for many scientific studies including astronomy. This paper introduced a single equation iterative method for solving complex linear equations, and this method can deconvolute dirty images, eliminate the effects of the PSF well. With different PSFs, this algorithm shows very good results in deconvolution. Also, with a giant PSF of aperture synthesis imaging, this algorithm improves the peak signal-to-noise ratio and structural similarity of the dirty images by 41.0% and 33.9% on average. In addition, this paper proves that the algorithm can deconvolute the dirty image by making full use of the information of each pixel in the image, even if the dirty image has salt and pepper noise or even lost areas; by its excellent properties of flexible operation to a single pixel, all these bad situations can be dealt with and the image can be restored.
分类： 天文学 >> 天文学 提交时间： 2025-02-25 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： The Five-hundred-meter Aperture Spherical radio Telescope (FAST) is the most sensitive telescope at the L-band (1.0–1.5 GHz) and has been used to carry out the FAST Galactic Plane Pulsar Snapshot (GPPS) survey in the last 5 yr. Up to now, the survey has covered one-fourth of the planned areas within ±10∘ from the Galactic plane visible by FAST, and discovered 751 pulsars. After the first publication of the discovery of 201 pulsars and one rotating radio transient (RRAT) in 2021 and 76 RRATs in 2023, here we report the discovery of 473 new pulsars from the FAST GPPS survey, including 137 new millisecond pulsars and 30 new RRATs. We find 34 millisecond pulsars discovered by the GPPS survey which can be timed with a precision better than 3 μs by using FAST 15 minute observations and can be used for pulsar timing arrays. The GPPS survey has discovered eight pulsars with periods greater than 10 s including one with 29.77 s. The integrated profiles of pulsars and individual pulses of RRATs are presented. During the FAST GPPS survey, we also detected previously known pulsars and updated parameters for 52 pulsars. In addition, we discovered two fast radio bursts plus one probable case with high dispersion measures indicating their extragalactic origin.
分类： 天文学 >> 天文学 提交时间： 2025-02-25 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： Magnetars are slowly rotating, highly magnetized young neutron stars that can show transient radio phenomena for radio pulses and fast radio bursts. We conducted radio observations from two magnetars SGR J1935+2154 and 3XMM J185246.6+003317 and a high-magnetic field pulsar PSR J1846–0258 using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). We performed single pulse and periodicity searches and did not detect radio signals from them. From the piggyback data recorded by other FAST telescope beams when we observed the magnetar SGR 1935+2154, we serendipitously discovered a new radio pulsar, PSR J1935+2200. We carried out the follow-up observations and obtained the timing solution based on these new observations and the archive FAST data. PSR J1935+2200 is an isolated old pulsar, with a spin period of 0.91 s, a spin-period derivative of 9.19 × 10−15 s s−1, and a characteristic age of 1.57 Myr. It is a weak pulsar with a flux density of 9.8 μJy at 1.25 GHz. Discovery of a new pulsar from the long FAST observations of 30 minutes implies that there may be more weak older pulsars in the Galactic disk to be discovered.
分类： 天文学 >> 天文学 提交时间： 2025-01-07 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： We have examined most of the astrophysical properties of the two star clusters, FSR-163 and Majaess 215, using the third data release of the Gaia space mission (Gaia DR3). We utilized the pyUPMASK method to allocate the probabilities of stars' membership candidates. Using the clusters' trigonometric parallaxes of the members with probabilities P > 50%, we calculated the distance to the clusters of 3290 (±140) and 2833 (±140) pc, respectively, which match well with our isochrone fitting results on the color–magnitude diagrams. We determined the age of the clusters, and they are 1.00 (±0.15) and 3.55 (±0.15) Gyr for FSR-163 and Majaess 215, respectively. We evaluated the following photometric parameters: reddenings, distances, galactic geometrical distances, luminosity–mass functions, and total masses of the two clusters. On studying the dynamic state of the two clusters, we found that Majaess 215 is more relaxed than FSR-163.
分类： 天文学 >> 天文学 提交时间： 2025-01-07 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： An extreme ultraviolet (EUV) close-up view of the Sun offers unprecedented detail of heating events in the solar corona. Enhanced temporal and spatial images obtained by the Solar Orbiter during its first science perihelion enabled us to identify clustered EUV bright tadpoles (CEBTs) occurring near the footpoints of coronal loops. Combining SDO/AIA observations, we determine the altitudes of six distinct CEBTs by stereoscopy, ranging from ∼1300 to 3300 km. We then notice a substantial presence of dark, cooler filamentary structures seemingly beneath the CEBTs, displaying periodic up-and-down motions lasting 3–5 minutes. This periodic behavior suggests an association of the majority of CEBTs with Type I spicules. Out of the ten selected CEBTs with fast downward velocity, six exhibit corrected velocities close to or exceeding 50 km s−1. These velocities notably surpass the typical speeds of Type I spicules. We explore the generation of such velocities. It indicates that due to the previous limited observations of spicules in the EUV wavelengths, they may reveal novel observational features beyond our current understanding. Gaining insights into these features contributes to a better comprehension of small-scale coronal heating dynamics.
分类： 天文学 >> 天文学 提交时间： 2025-02-25 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： Finding pulsars in binaries is important for measurements of the masses of neutron stars (NSs), for tests of gravity theories, and for studies of star evolution. We are carrying out the Galactic Plane Pulsar Snapshot survey (GPPS) by using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). Here we present the Keplerian parameters for 116 newly discovered pulsars in the FAST GPPS survey and obtain timing solutions for 29 pulsars. Companions of these pulsars are He white dwarfs (WDs), CO/ONe WDs, NSs, main sequence stars and ultra light objects or even planets. Our observations uncover eclipses of eight binary systems. The optical counterpart for the companion of PSR J1908+1036 is identified. The Post-Keplerian parameter �˙for the double NS systems PSR J0528+3529 and J1844-0128 have been measured, with which the total masses of the binary systems are determined.
分类： 天文学 >> 天文学 提交时间： 2025-01-07 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： It is generally believed that coronal mass ejections (CMEs) have magnetic flux rope structures because of their helical shapes. However, only about 30%–40% of interplanetary CMEs (ICMEs) have a local magnetic flux rope structure. The usual explanations are that the spacecraft only crossed the flank of the ropes and failed to detect the complete magnetic flux rope structure or that some processes destroyed these magnetic flux rope structures. Several studies suggest that some ICMEs inherently possess disordered magnetic fields and consequently exhibit no magnetic flux-rope structures. We introduce a special kind of ICME which has a low magnetic field magnitude and stable magnetic field direction, relatively fast expansion speed, and lower proton temperature and density. All three of the measured magnetic field components are relatively stable. We want to know whether these ICMEs also have magnetic flux rope structures or not. We identified 20 special ICMEs and analyzed their evolution based on their observed characteristics. We took a special ICME as an example, which had an apparent rope configuration at 1 au but evolved to a special ICME at 5.4 au, to illustrate that this kind of ICME could come from magnetic clouds (MCs) whose rope structure had been being stretched due to expansion. We inferred that the missing obvious flux rope structure may be due to the expansion of MCs, not the flank crossing effect. However, more than 50% of the events were associated with the dominant x-component of the magnetic field, which indicates a leg crossing. Therefore, the detection of part of these special ICMEs may also be the result of the leg-crossing effect.
分类： 天文学 >> 天文学 提交时间： 2025-03-11 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： We present the essential stellar parameters of the close visual triple system HD 2893 using Al-Wardat's method for analyzing binary and multiple star systems in conjunction with Kurucz's model atmospheres. This method accurately computes the spectrophotometric stellar masses through a combined synthetic spectral energy distribution approach that compares the results with observed data. The vigorous approach uses spectroscopic, photometric, and dynamical analysis to yield precise results. The method implements Gaia DR3 measurements and other measurements like those of Hipparcos and 2MASS All-Sky Catalog as a guide for the best fit between the synthetic spectra and observed photometry. The analysis gives precise spectrophotometric stellar masses for the system being , , and . It shows that the three components are main sequence stars with an estimated age of around 1.0 Gyr. When integrated with the dynamical analysis, a new dynamical parallax for the system is obtained, πdyn = 13.8528 ± 0.20 mas. Additionally, the discussion covers the formation and evolution of the triple system.
分类： 物理学 >> 核物理学 提交时间： 2025-07-02
Kolokolchikov, Mr. Sergey
Senichev, Yu. V.
Melnikov, Mr. Alexey
Aksentev, A. E.
Palamarchuk, Miss Patricia
摘要： A novel experimental setup with spatially separated magnetic and electrostatic fields is proposed for proton and deuteron electric dipole moment (EDM) studies. The lattice design, which employs a spin compensator to achieve the “quasi-frozen” spin condition for precise measurements, demonstrates adaptability to existing facilities for high energy physics research.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-11-02 合作期刊: 《热科学学报》
摘要： The development of heat recovery methods for dry granulation processes from blast furnace slag in the iron and steel industry is limited because of the high consumption of granulation energy during these processes. To determine the factors that influence the diameter of granulated particles, a paraffin test platform for gas quenching granulation was established. The influences of air velocity, air flow rate, liquid mass flow rate, and liquid pipe diameter on the final particle size and mass distribution were studied. Experimental results showed that the final particle size decreased (from 1.07 mm to 0.81 mm) with increasing air velocity (from 28.3 m/s to 113.2 m/s). However, when air velocity was higher than 60 m/s, its influence on particle diameter decreased significantly. The experimental data were analyzed using SPSS Statistics software, which indicated that the effect of air velocity on particle diameter was the most significant, followed by those of air flow and liquid pipe diameter. The effect of liquid mass flow was the least significant.
分类： 生物学 >> 植物学 >> 植物生物化学、植物生物物理学 提交时间： 2016-05-03
Maria Elisa Sabatini
Mattia Donà
Paola Leonetti
Andrea Minio
Massimo Delledonne
Daniela Carbonera
Massimo Confalonieri
Giorgio Giraffa and Alma Balestrazzi
摘要： The role of plant tyrosyl-DNA phosphodiesterase 1 in genome stability is studied using a Medicago truncatula MtTdp1-depleted line. Lack of MtTdp1 results in a 39% reduction of methylated cytosines as compared to control. RNA-Seq analyses revealed that 11 DNA transposons and 22 retrotransposons were differentially expressed in the Tdp1-2a line. Among them all, DNA transposons (MuDR, hAT, DNA3-11_Mad) and seven retrotransposons (LTR (Long Terminal Repeat)/Gipsy, LTR/Copia, LTR and NonLTR/L1) were down-regulated, while the 15 retrotransposons were up-regulated. Results suggest that the occurrence of stress-responsive cis-elements as well as changes in the methylation pattern at the LTR promoters might be responsible for the enhanced retrotransposon transcription.
分类： 核科学技术 >> 核科学与技术 提交时间： 2025-03-29
摘要： This study explores the phenomenon of shape coexistence in nuclei around ^{172}Hg, with a focus on the isotopes ^{170}Pt, ^{172}Hg, and ^{174}Pb, as well as the ^{170}Pt to ^{180}Pt isotopic chain. Utilizing a macro-microscopic approach that incorporates the Lublin-Strasbourg Drop model combined with a Yukawa-Folded potential and pairing corrections, we analyze the potential energy surfaces (PESs) to understand the impact of pairing interaction.For^{170}Pt, the PES exhibited a prolate ground-state, with additional triaxial and oblate-shaped isomers. In ^{172}Hg, the ground-state deformation transitions from triaxial to oblate with increasing pairing interaction, demonstrating its nearly \gamma-unstable nature. Three shape isomers (prolate, triaxial, and oblate) were observed, with increased pairing strength leading to the disappearance of the triaxial isomer.^{174}Pb exhibited a prolate ground-state that became increasingly spherical with stronger pairing. While shape isomers were present at lower pairing strengths, robust shape coexistence was not observed. For realistic pairing interaction, the ground-state shapes transitioned from prolate in ^{170}Pt to a coexistence of \gamma-unstable and oblate shapes in ^{172}Hg, ultimately approaching spherical symmetry in ^{174}Pb. A comparison between Exact and Bardeen-Cooper-Schrieffer (BCS) pairing demonstrated that BCS pairing tends to smooth out shape coexistence and reduce the depth of the shape isomer, leading to less pronounced deformation features.The PESs for even-even ^{170-180}Pt isotopes revealed significant shape evolution. ^{170}Pt showed a prolate ground-state, whereas^{172}Pt exhibited both triaxial and prolate shape coexistence. In ^{174}Pt, the ground-state was triaxial, coexisted with a prolate minimum. For ^{176}Pt, a \gamma-unstable ground-state coexists with a prolate minimum. By ^{178}Pt and ^{180}Pt, a dominant prolate minimum emerged. These results highlight the role of shape coexistence and \gamma-instability in the evolution of nuclear structure, especially in the mid-shell region.These findings highlight the importance of pairing interactions in nuclear deformation and shape coexistence, providing insights into the structural evolution of mid-shell nuclei.
分类： 核科学技术 >> 粒子加速器 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： The computed tomography was applied to setting STIM (Scanning Transmission Ion Microscopy) projections recorded at the Fudan Ion Beam Laboratory. In this work, in order to visualize the three-dimensional mass density distribution in several specimens, example for a test structure of hollow gold cyliner was presented together with a detailed description of the developed system, including data reconstruction code (Tomorebuild 2) and image display software (AMIRA�). Future development will allow the particle induced X-ray emission tomography for elemental analysis of micrometer-sized samples.
分类： 生物学 >> 生物工程 提交时间： 2019-01-17 合作期刊: 《中国生物工程杂志》
摘要： 固定化酶作为一种绿色高效的生物催化剂，其性能远超游离酶。目前酶的固定化技术适用范围仍然较小，酶的研究范围多停留在模型酶阶段，扩大固定化酶的研究范围具有十分重要的意义。金属有机骨架材料（MOFs）作为酶固定化的载体在近些年得到了广泛的探索，但是具有生物功能的酶-MOFs复合材料的许多特性仍有待挖掘。本文采用仿生矿化的合成方法将5-羟甲基糠醛氧化酶（HMFO）固定到以沸石咪唑酯（ZIF-8）为代表的MOFs材料中，制备得到一种新的生物催化剂HMFO@ZIF-8，扫描电子显微镜表征其形态区别于经典的菱形十二面体。采用考马斯亮蓝法测定蛋白质浓度，计算得到酶的固定化效率达到89.0%。HMFO@ZIF-8催化5-羟甲基糠醛的转化率达到84.3%，收率和选择性均高于游离酶。本文拓展了MOFs固定化酶的研究范围，为研究其他生物大分子复合材料的生物催化剂提供一定的借鉴意义。
分类： 物理学 >> 核物理学 提交时间： 2016-09-14
J. Comparat
C.-H. Chuang
S. Rodr韌uez-Torres
M. Pellejero-Ibanez
F. Prada
G. Yepes
H. M. Courtois
G.-B. Zhao
Y. Wang
J.Sanchez
C. Maraston
Benton Metcalf
J. Peiro-Perez
F. S. Kitaura
E.P閞ez
R. M. Gonz醠ez Delgado
摘要： The Baryon Acoustic Oscillation (BAO) feature in the power spectrum of galaxies provides a standard ruler to measure the accelerated expansion of the Universe. To extract all available information about dark energy, it is necessary to measure a standard ruler in the local, z<0.2, universe where dark energy dominates most the energy density of the Universe. Though the volume available in the local universe is limited, it is just big enough to measure accurately the long 100 Mpc/h wave-mode of the BAO. Using cosmological N-body simulations and approximate methods based on Lagrangian perturbation theory, we construct a suite of a thousand light-cones to evaluate the precision at which one can measure the BAO standard ruler in the local universe. We find that using the most massive galaxies on the full sky (34,000 sq. deg.), i.e. a K(2MASS)<14 magnitude-limited sample, one can measure the BAO scale up to a precision of 4\% and 1.2\% using reconstruction). We also find that such a survey would help to detect the dynamics of dark energy.Therefore, we propose a 3-year long observational project, named the Low Redshift survey at Calar Alto (LoRCA), to observe spectroscopically about 200,000 galaxies in the northern sky to contribute to the construction of aforementioned galaxy sample. The suite of light-cones is made available to the public.
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