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Probing the Kinematic Signatures of Planet Formation in the Gas Disk of MWC 480

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Research in Astronomy and astrophysics 2024年第6期24卷 112-120页

作者： Min Zhao Haochuan Yu Zhengxiang Li department of Astronomy Beijing Normal University Sub-department of astrophysics Department of Physics University of Oxford

The disk around MWC 480 has shown multiple substructures in both dust and gas observations, possibly suggesting ongoing planet formation in situ. In this paper, we explore the gas kinematics of the MWC 480 disk by analyzing the archival Atacama Large Millimeter/submillimeter Array observations of12CO（J = 2-1）,13CO（J = 2-1）, and C18O（J = 2-1）. By modeling the line-of-sight velocities, inferred from the Doppler shifts of the emission lines, we are able to decompose the three-dimensional（3D） velocity field of the disk into rotational,radial, and vertical components. Further analysis reveals the presence of large-scale gas flows in the（r, z） plane.Notably, we identify potential meridional flows across various heights as traced by all three CO isotopologues in the 80–120 au region, possibly associated with ongoing planet formation activities in this region. Moreover, we find upward flows near 200 au for all three CO isotopologues, which may point to the presence of disk winds.

关键词： planet-disk interactions planet-star interactions protoplanetary disks

Pulsar Glitch Activities: The Spin Parameters Approach

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Research in Astronomy and astrophysics 2024年第6期24卷 336-359页

作者： Innocent Okwudili Eya Evaristus Uzochukwu Iyida physics/Electronics Technique—department of Science Laboratory Technology University of Nigeria department of physics and Astronomy University of Nigeria Astronomy and astrophysics Research Lab University of Nigeria

Glitch activity refers to the mean increase in pulsar spin frequency per year due to rotational glitches. It is an important tool for studying super-nuclear matter using neutron star interiors as templates. Glitch events are typically observed in the spin frequency(ν) and frequency derivative( ν) of pulsars. The rate of glitch recurrence decreases as the pulsar ages, and the activity parameter is usually measured by linear regression of cumulative glitches over a given period. This method is effective for pulsars with multiple regular glitch events. However, due to the scarcity of glitch events and the difficulty of monitoring all known pulsars, only a few have multiple records of glitch events. This limits the use of the activity parameter in studying neutron star interiors with multiple pulsars.In this study, we examined the relationship between the activity parameters and pulsar spin parameters(spin frequency, frequency derivative, and pulsar characteristic age). We found that a quadratic function provides a better fit for the relationship between activity parameters and spin parameters than the commonly used linear functions.Using this information, we were able to estimate the activity parameters of other pulsars that do not have records of glitches. Our analysis shows that the relationship between the estimated activity parameters and pulsar spin parameters is consistent with that of the observed activity parameters in the ensemble of pulsars.

关键词： (stars:) pulsars: general methods: statistical stars: neutron

Long Term X-Ray Spectral Variations of the Seyfert-1 Galaxy Mrk 279

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Research in Astronomy and astrophysics 2024年第6期24卷 309-316页

作者： K.Akhila Ranjeev Misra Savithri H.Ezhikode K.Jeena department of physics Providence Women's College University of Calicut Inter-University Centre for Astronomy and astrophysics (IUCAA) department of physics and Electronics CHRIST (Deemed to be University)

We present the results from a long term X-ray analysis of Mrk 279 during the period 2018–2020. We use data from multiple missions–AstroSat, NuSTAR and XMM-Newton, for the purpose. The X-ray spectrum can be modeled as a double Comptonization along with the presence of neutral Fe Kα line emission, at all epochs. We determined the source’s X-ray flux and luminosity at these different epochs. We find significant variations in the source’s flux state. We also investigate the variations in the source’s spectral components during the observation period. We find that the photon index and hence the spectral shape follow the variations only over longer time periods. We probe the correlations between fluxes of different bands and their photon indices, and found no significant correlations between the parameters.

关键词： galaxies: individual (Mrk 335) galaxies: Seyfert X-rays: galaxies

Probing the Gamma-Ray Emission Region of Five TeV Flat Spectrum Radio Quasars

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Research in Astronomy and astrophysics 2024年第6期24卷 158-171页

作者： Hu-Bing Xiao Hai-Tao Cao Rui Xue Jin-Ting Cai Ge-Ge Wang Marina Manganaro Shao-Hua Zhang Zhi-Hao Ouyang Li-Ping Fu Jun-Hui Fan Shanghai Key Lab for astrophysics Shanghai Normal University School of Information Engineering department of physics Zhejiang Normal University College of Mathematics and physics Guangxi Minzu University Key Laboratory of Cosmology and astrophysics (Liaoning) College of Sciences Northeastern University department of physics University of Rijeka Center for astrophysics Guangzhou University Key Laboratory for Astronomical Observation and Technology of Guangzhou Astronomy Science and Technology Research Laboratory of department of Education of Guangdong Province

The location of γ-ray emission of blazars remains a contested topic, inspiring the development of numerous investigative techniques to address this issue. In this work, we analyzed Fermi γ-ray light curves in the GeV and MeV bands, employing the discrete cross-correlation function method to discern time lags between the two bands.For 4C +21.35, Ton 599, B2 1420+32, and PKS 1510-089, we identified a time lag spanning several days, while for PKS 1441+25, the time lag was not statistically found. The results imply that the soft photons necessary for inverse Compton scattering predominantly originate from the dusty torus in the first four sources, whereas for PKS1441+25, they seem to be sourced mainly from the broad-line region. Further analysis of the opacity(τγγ) and the GeV spectra study supports the conclusion that the location of the dissipation region must be beyond the BLR to avoid significant absorption. Notably, for PKS 1441+25, the emission region is also posited to lie outside yet proximate to the BLR. The parameters of describing the emission region were obtained by fitting broadband spectral energy distribution with contemporaneous observation data. Our findings suggest that for the five TeV FSRQs, during Te V flaring events, the jet appears to maintain an equilibrium between the energy density of the magnetic field and that of the particles for all investigated sources, with the exceptions of 4C +21.35 and PKS1441+25. In terms of the overall jet power, particle energy is the dominant contributor, and the observed blazar radiation cannot be solely attributed to the magnetic field, except in the case of 4C +21.35. Consequently,magnetic reconnection is unlikely to be the primary mechanism behind particle acceleration in these systems.

关键词： galaxies: active galaxies: jets gamma-rays: galaxies

New evidence for lack of CMB power on large scales

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Science China(physics,Mechanics & Astronomy) 2010年第3期53卷 567-570页

作者： LIU Hao1 & LI TiPei1,2,3 1 Key Laboratory of Particle astrophysics, Institute of High Energy physics, Chinese Academy of Sciences, Beijing 100049, China 2 department of physics & Center for astrophysics, Tsinghua University, Beijing 100084, China 3 department of Engineering physics & Center for astrophysics, Tsinghua University, Beijing 100084, China Key Laboratory of Particle astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing China department of physics & Center for astrophysics Tsinghua University Beijing China department of Engineering physics & Center for astrophysics Tsinghua University Beijing China

A digitalized temperature map is recovered from the first light sky survey image published by the Planck team, from which an angular power spectrum of the cosmic microwave background (CMB) is derived. The amplitudes of the low multipoles (low-l) measured from the preliminary Planck power spectrum are significantly lower than those reported by the WMAP team. Possible systematical effects are far from enough to explain the observed low-l differences.

关键词： cosmology cosmic microwave background data analysis

Tensor perturbations from bounce inflation scenario in f(Q)gravity

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Science China(physics,Mechanics & Astronomy) 2024年第2期67卷 78-92页

作者： Kun Hu Tanmoy Paul Taotao Qiu Institute of astrophysics Central China Normal UniversityWuhan 430079China School of physics Huazhong University of Science and TechnologyWuhan 430074China National Institute of Technology Jamshedpur Department of PhysicsJamshedpur 831014India

In this paper,we construct a bounce inflation cosmological scenario in the framework of the modified symmetric teleparallel gravity,namely f(Q)theory,and investigate the tensor perturbations therein.As is well-known,the tensor perturbations generated in the very early Universe(inflation and pre-inflation regions)can account for the primordial gravitational waves(PGWs)that are to be detected by the next generation of GW experiments.We discuss the stability condition of the tensor perturbations in the bounce inflation process and investigate in detail the evolution of the perturbation variable.The general form of the tensor power spectrum is obtained both for large as well as small scale modes.As a result,we show both kinds of modes(short or long wavelength modes),and the tensor spectrum may get a positive tilt in the parametric range where the tensor perturbation proves to be stable—this interestingly hints an enhancement of gravitational waves’amplitude in the background of the f(Q)bounce-inflation scenario.Moreover,we study the LQC-like scenario as a specific case of our model,in which,the primordial tensor power spectrum turns out to be nearly scale-invariant on both small and large scales.

关键词： bounce cosmology modified gravity cosmological perturbations

Inconsistency between WMAP data and released map

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Chinese Science Bulletin 2010年第10期55卷 907-909页

作者： LIU Hao1 & LI TiPei1,2,3 1 Key Laboratory of Particle astrophysics,Institute of High Energy physics,Chinese Academy of Sciences,Beijing 100049,China 2 department of physics & Center for astrophysics,Tsinghua University,Beijing 100084,China 3 department of Engineering physics & Center for astrophysics,Tsinghua University,Beijing 100084,China Key Laboratory of Particle astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing China department of physics & Center for astrophysics Tsinghua University Beijing China department of Engineering physics & Center for astrophysics Tsinghua University Beijing China

A remarkable inconsistency between the calibrated differential time-ordered data (TOD) of the Wilkinson Microwave Anisotropy Probe (WMAP) mission,which is the input for map-making,and the cosmic microwave background (CMB) temperature maps published by the WMAP team is revealed,indicating that there must exist a serious problem in the map making routine of the WMAP team.This inconsistency is easy to be confirmed without the use of WMAP map-making software.In view of the importance of this issue for cosmology study,we invite readers to check it by themselves.

关键词：威尔金森微波各向异性探测器 WMAP 地图制作宇宙微波背景有序数据制作软件 TOD CMB

Timing in the Time Domain: Cygnus X-1

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Chinese Journal of Astronomy and astrophysics 2001年第4期1卷 313-332页

作者： Ti-Pei Li (department of physics and Center for astrophysics, Tsinghua University, Beijing 100084 High Energy astrophysics Lab., Institute of High Energy physics, Chinese Academy of Sciences, Beijing 100039)E-mail:litp@*** department of physics and Center for astrophysics Tsinghua University Beijing 100084 High Energy Astrophysics Lab. Institute of High Energy Physics Chinese Academy of Sciences Beijing 100039

Quantities characterizing temporal property, e.g., power density, coherence, and time lag, can be defined and calculated directly in the time domain without using the Fourier transformation. Spectral hardness, variability duration, and correlation between different characteristic quamtities on different time scale can be studied in the time domain as well. The temporal analysis technique in the time domain is a powerful tool, particularly in studying rapid variability on short time scales (or in high frequencies). Results of studying variabilities of X-rays from Cyg X-1 with the analysis technique in the time domain and RXTE data reveal valuable clues to understanding production and propagation processes of X-rays and structure of accretion disk in the black hole system.

关键词： methods: data analysis - stars: individual (Cygnus X-1) - X-rays: stars

Constraints on Cardassian universe from Gamma ray bursts

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Science China(physics,Mechanics & Astronomy) 2010年第9期53卷 1720-1725页

作者： WANG TaiShan1 & LIANG Nan2 1 department of physics & Center for astrophysics,Tsinghua University,Beijing 100084,China 2 department of Astronomy,Beijing Normal University,Beijing 100875,China department of physics & Center for astrophysics Tsinghua University Beijing China department of Astronomy Beijing Normal University Beijing China

Constraints on the original Cardassian model and the modified polytropic Cardassian model are examined from the recently derived 42 gamma-ray bursts(GRBs) data calibrated with the method that can avoid the circularity problem.The results show that GRBs can be an optional observation to constrain the Cardassian models.Combining the GRBs data with the newly de-rived size of baryonic acoustic oscillation peak from the Sloan Digital Sky Survey(SDSS),and the position of the first acoustic peak of the Cosmic Microwave Background radiation(CMB) from Wilkinson Microwave Anisotropy Probe(WMAP),we find Ωm0=0.27+0.02-0.02,n=0.06+0.07-0.08(1σ) for the original Cardassian model,and Ωm0=0.27+0.23-0.02,n=-0.09+0.23-1.91,β=0.82+2.10-0.62(1σ) for the modified polytropic Cardassian model.

关键词： Cardassian Gamma ray burst Cosmic Microwave Background baryonic acoustic oscillation