The Astronomy and Astrophysics Review最新文献

{"title":"What happened before?","authors":"Per-Gunnar Valegård, L. Waters, C. Dominik","doi":"10.1051/0004-6361/202039802","DOIUrl":"https://doi.org/10.1051/0004-6361/202039802","url":null,"abstract":"We seek to find the precursors of the Herbig Ae/Be stars in the solar vicinity within 500 pc from the Sun. We do this by creating an optically selected sample of intermediate mass T-Tauri stars (IMTT stars) here defined as stars of masses $1.5 M_{odot}leq M_* leq 5 M_{odot}$ and spectral type between F and K3, from literature. We use literature optical photometry (0.4-1.25$mu$m) and distances determined from Gaia DR2 parallax measurements together with Kurucz stellar model spectra to place the stars in a HR-diagram. With Siess evolutionary tracks we identify intermediate mass T-Tauri stars from literature and derive masses and ages. We use Spitzer spectra to classify the disks around the stars into Meeus Group I and Group II disks based on their [F$_{30}$/F$_{13.5}$] spectral index. We also examine the 10$mu$m silicate dust grain emission and identify emission from Polycyclic Aromatic Hydrocarbons (PAH). From this we build a qualitative picture of the disks around the intermediate mass T-Tauri stars and compare this with available spatially resolved images at infrared and at sub-millimeter wavelengths to confirm our classification. We find 49 intermediate mass T-Tauri stars with infrared excess. The identified disks are similar to the older Herbig Ae/Be stars in disk geometries and silicate dust grain population. Spatially resolved images at infra-red and sub-mm wavelengths suggest gaps and spirals are also present around the younger precursors to the Herbig Ae/Be stars. Comparing the timescale of stellar evolution towards the main sequence and current models of protoplanetary disk evolution the similarity between Herbig Ae/Be stars and the intermediate mass T-Tauri stars points towards an evolution of Group I and Group II disks that are disconnected, and that they represent two different evolutionary paths.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"68 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80685778","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Stability of solar atmospheric structures harboring standing slow waves","authors":"M. Geeraerts, T. Van Doorsselaere","doi":"10.1051/0004-6361/202140534","DOIUrl":"https://doi.org/10.1051/0004-6361/202140534","url":null,"abstract":"Context. In the context of the solar coronal heating problem, one possible explanation for the high coronal temperature is the release of energy by magnetohydrodynamic (MHD) waves. The energy transfer is believed to be possible, among others, by the development of the Kelvin-Helmholtz instability (KHI) in coronal loops. Aims. Our aim is to determine if standing slow waves in solar atmospheric structures such as coronal loops, and also prominence threads, sunspots, and pores, can trigger the KHI due to the oscillating shear flow at the structure’s boundary. Methods. We used linearized nonstationary MHD to work out an analytical model in a cartesian reference frame. The model describes a compressible plasma near a discontinuous interface separating two regions of homogeneous plasma, each harboring an oscillating velocity field with a constant amplitude which is parallel to the background magnetic field and aligned with the interface. The obtained analytical results were then used to determine the stability of said interface, both in coronal and photospheric conditions. Results. We find that the stability of the interface is determined by a Mathieu equation. In function of the parameters of this equation, the interface can either be stable or unstable. For coronal as well as photospheric conditions, we find that the interface is stable with respect to the KHI. Theoretically, it can, however, be unstable with respect to a parametric resonance instability, although it seems physically unlikely. We conclude that, in this simplified setup, a standing slow wave does not trigger the KHI without the involvement of additional physical processes.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"55 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77441313","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Revisiting the archetypical wind accretor Vela X-1 in depth","authors":"P. Kretschmar, I. Mellah, S. Mart'inez-N'unez, F. Furst, Victoria Grinberg, Andreas A. C. Sander, J. Eijnden, N. Degenaar, Jes'us Ma'iz-Apell'aniz, Francisco Jim'enez Esteban, M. Ramos-Lerate, E. Utrilla","doi":"10.1051/0004-6361/202040272","DOIUrl":"https://doi.org/10.1051/0004-6361/202040272","url":null,"abstract":"Context: Vela X-1 is one of the best studied X-ray binaries. Frequently though, specific values for its parameters have been used in subsequent studies without considering alternatives. Aims: We aim to provide a robust compilation and synthesis of the accumulated knowledge about Vela X-1 as a solid baseline for future studies and identify specific avenues of possible future research. Methods: We explore the literature for Vela X-1 and on modelling efforts, describing the evolution of the system knowledge. We also add information derived from public data, especially the Gaia EDR3 release. Results: We update the distance to Vela X-1, the spectral classification for HD 77518 and find that the supergiant may be very close to filling its Roche lobe. Constraints on the clumpiness of the stellar wind have improved. The orbit is very well determined, but the uncertain inclination limits information on the neutron star mass. Estimates for the stellar wind have evolved towards lower velocities, supporting the idea of transient wind-captured disks around the neutron star. Hydrodynamic models and observations are consistent with an accretion wake trailing the neutron star. Conclusions: Vela X-1 is an excellent laboratory, but a lot of room remains to improve. Well-coordinated multi-wavelength observations and campaigns addressing the intrinsic variability are required. New opportunities will arise through new instrumentation. Models of the stellar wind should account for the orbital eccentricity and the non-spherical shape of HD 77581. Realistic multi-dimensional models of radiative transfer in the UV and X-rays are needed, but remain very challenging. Improved MHD models covering a wide range of scales would be required to improve understanding of the plasma-magnetosphere coupling. A full characterization of the accretion column remains another open challenge. (Abbreviated for arXiv)","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"48 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84998211","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"General-relativistic instability in rapidly accreting supermassive stars: The impact of rotation","authors":"L. Haemmerl'e","doi":"10.1051/0004-6361/202140893","DOIUrl":"https://doi.org/10.1051/0004-6361/202140893","url":null,"abstract":"Supermassive stars (SMSs) collapsing via the general-relativistic (GR) instability are invoked as the possible progenitors of supermassive black holes. Their mass and angular momentum at the onset of the instability are key in many respects, in particular regarding the possibility for observational signatures of direct collapse. Here, we study the stability of rotating, rapidly accreting SMSs against GR and derive the properties of these stars at death. On the basis of hylotropic structures, relevant for rapidly accreting SMSs, we define rotation profiles under the assumption of local angular momentum conservation in radiative regions, which allows for differential rotation. We find that rotation favours the stability of rapidly accreting SMSs as soon as the accreted angular momentum represents a fraction f > 0.1% of the Keplerian angular momentum. For f = 0.3%-0.5% the maximum masses consistent with GR stability are increased by an order of magnitude compared to the non-rotating case. For f = 1%, the GR instability cannot be reached if the stellar mass does not exceed 10^7-10^8 Msun. These results imply that, like in the non-rotating case, the final masses of the progenitors of direct collapse black holes range in distinct intervals depending on the scenario considered: 10^5 Msun < M < 10^6 Msun for primordial atomically cooled haloes; 10^6 Msun < M < 10^9 Msun for metal-rich galaxy mergers. The models suggest that the centrifugal barrier is inefficient to prevent the direct formation of a supermassive black hole at the collapse of a SMS. Moreover, the conditions of galaxy mergers appear as more favorable than those of atomically cooled haloes for detectable gravitational wave emission and ultra-long gamma-ray bursts at black hole formation.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"79 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91214044","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"LoTSS jellyfish galaxies. I. Radio tails in low redshift clusters","authors":"I. Roberts, R. Weeren, S. McGee, A. Botteon, A. Drabent, A. Ignesti, H. Rottgering, T. Shimwell, C. Tasse","doi":"10.1051/0004-6361/202140784","DOIUrl":"https://doi.org/10.1051/0004-6361/202140784","url":null,"abstract":"In this paper we present a large sample of jellyfish galaxies in low redshift clusters (z<0.05), identified through 120-168 MHz radio continuum from the LOFAR Two-metre Sky Survey (LoTSS). From a parent sample of 29 X-ray-detected SDSS galaxy clusters and their spectroscopic members, we visually identify 95 star-forming, LoTSS jellyfish galaxies with 144 MHz radio tails. Star formation rates (SFRs) and stellar masses are obtained for all galaxies from SED fits. For each jellyfish galaxy we determine the tail orientation with respect to the cluster centre and quantify the prominence of the radio tails with the 144 MHz shape asymmetry. After carefully accounting for redshift-dependent selection effects, we find that the frequency of jellyfish galaxies is relatively constant from cluster to cluster. LoTSS jellyfish galaxies are preferentially found at small clustercentric radius and large velocity offsets within their host clusters and have radio tails that are oriented away from the cluster centre. These galaxies also show enhanced star formation, relative to both 'normal' cluster galaxies and isolated field galaxies, but generally fall within the scatter of the L144MHz - SFR relation. The properties of the LoTSS jellyfish galaxies identified in this work are fully consistent with expectations from ram pressure stripping. This large sample of jellyfish galaxies will be valuable for further constraining ram pressure stripping and star formation quenching in nearby galaxy clusters. We show that LOFAR is a powerful instrument for identifying ram pressure stripped galaxies across extremely wide fields. Moving forward we will push the search for jellyfish galaxies beyond this initial cluster sample, including a comprehensive survey of the galaxy group regime.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"130 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85264231","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The effects of the initial mass function on Galactic chemical enrichment","authors":"S. Goswami, A. Slemer, P. Marigo, A. Bressan, L. Silva, M. Spera, L. Boco, V. Grisoni, L. Pantoni, A. Lapi","doi":"10.1051/0004-6361/202039842","DOIUrl":"https://doi.org/10.1051/0004-6361/202039842","url":null,"abstract":"Context. There is mounting evidence that the stellar initial mass function (IMF) could extend much beyond the canonical Mi ∼ 100M limit, but the impact of such hypothesis on the chemical enrichment of galaxies still remains to be clarified. Aims. We aim to address this question by analysing the observed abundances of thinand thick-disc stars in the Milky Way with chemical evolution models that account for the contribution of very massive stars dying as pair instability supernovae. Methods. We built new sets of chemical yields from massive and very massive stars up to Mi ∼ 350M , by combining the wind ejecta extracted from our hydrostatic stellar evolution models with explosion ejecta from the literature. Using a simple chemical evolution code we analyse the effects of adopting different yield tables by comparing predictions against observations of stars in the solar vicinity. Results. After several tests, we focus on the [O/Fe] ratio which best separates the chemical patterns of the two Milky Way components. We find that with a standard IMF, truncated at Mi ∼ 100M , we can reproduce various observational constraints for thin-disc stars, but the same IMF fails to account for the [O/Fe] ratios of thick-disc stars. The best results are obtained by extending the IMF up to Mi = 350M and including the chemical ejecta of very massive stars, in the form of winds and pair instability supernova explosions. Conclusions. Our study indicates that PISN could have played a significant role in shaping the chemical evolution of the Milky Way thick disc. By including their chemical yields it is easier to reproduce not only the level of the α-enhancement but also the observed slope of thick-disc stars in the [O/Fe] vs. [Fe/H] diagram. The bottom line is that the contribution of very massive stars to the chemical enrichment of galaxies is potentially quite important and should not be neglected in chemical evolution models.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"33 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79840212","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Two-body model for the spatial distribution of dust ejected from an atmosphereless body","authors":"A. Ershova, J. Schmidt","doi":"10.1051/0004-6361/202140624","DOIUrl":"https://doi.org/10.1051/0004-6361/202140624","url":null,"abstract":"We present a model for the configuration of noninteracting material that is ejected in a continuous manner from an atmosphereless gravitating body for a given distribution of sources. The model is applicable to material on bound or unbound trajectories and to steady and nonsteady modes of ejection. For a jet that is inclined to the surface normal, we related the distributions of ejection direction, velocity, and size to the phase-space number density at the distance from the source body. Integrating over velocity space, we obtained an expression from which we inferred the density, flux, or optical depth of the ejected material. As examples for the application of the code, we calculate profiles of the dust density in the Enceladus plume, the pattern of mass deposition rates around a plume on Europa, and images of optical depth following the nonstationary emission of material from a volcano on Io. We make the source code of a Fortran-95 implementation of the model freely available.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"15 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90519769","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Star formation histories of Coma cluster galaxies matched to simulated orbits hint at quenching around first pericenter","authors":"A. Upadhyay, K. Oman, S. Trager","doi":"10.1051/0004-6361/202141036","DOIUrl":"https://doi.org/10.1051/0004-6361/202141036","url":null,"abstract":"We study the relation between star formation history of galaxies falling into a high-density cluster environment and their likely orbital histories using both observational and simulation data. We use high-resolution spectra of 12 galaxies of the Coma Cluster around NGC 4874 (the X-ray center of the Coma Cluster). The stellar and kinematic properties of the galaxies are modeled using STECKMAP. We extract the probability distribution of two orbital parameters - infall and pericenter times - of these galaxies from N-body dark matter only simulations extending up to z = -1/2 ( ~10 Gyr in the future). The probability distribution of orbital parameters is compensated for the interloper probabilities of the satellites. We carry out a probability-based study to compare the cumulative (probability) distribution of the two orbital parameters with the star formation rates and the fraction of stellar mass formed. We find that massive galaxies (M_* > 10^10 M_sun) are quenched even before falling into the cluster environment. This may be due to internal quenching mechanisms or group pre-processing, although it is hard to ascertain the individual contribution of various processes. Lower mass galaxies form stars between infall and first pericenter passage and all the galaxies in our sample are quenched by the time of their first pericentric passage. Ram pressure and tidal stripping are likely to be the dominant processes as they peak with proximity to the cluster center.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"109 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90300781","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The CH radical at radio wavelengths: Revisiting emission in the 3.3 GHz ground-state lines","authors":"A. Jacob, K. Menten, H. Wiesemeyer, G. N. Ortiz-Le'on","doi":"10.1051/0004-6361/202140419","DOIUrl":"https://doi.org/10.1051/0004-6361/202140419","url":null,"abstract":"Context. The intensities of the three widely observed radio-wavelength hyperfine structure (HFS) lines between the Λ-doublet components of the rotational ground state of CH are inconsistent with local thermodynamic equilibrium (LTE) and indicate ubiquitous population inversion. While this can be qualitatively understood assuming a pumping cycle that involves collisional excitation processes, the relative intensities of the lines and in particular the dominance of the lowest frequency satellite line has not been well understood. This has limited the use of CH radio emission as a tracer of the molecular interstellar medium. Aims. We aim to investigate the nature of the (generally) weak CH ground state masers by employing synergies between the ground state HFS transitions themselves and with the far-infrared lines, near 149 μm (2 THz), that connect these levels to an also HFS split rotationally excited level. Methods. We present the first interferometric observations, with the Karl G. Jansky Very Large Array, of the CH 9 cm ground state HFS transitions at 3.264 GHz, 3.335 GHz, and 3.349 GHz toward the four high mass star-forming regions (SFRs) Sgr B2 (M), G34.26+0.15, W49 (N), and W51. We combine this data set with our high spectral resolution observations of the N, J =2, 3/2→1, 1/2 transitions of CH near 149 μm observed toward the same sources made with the upGREAT receiver on SOFIA, which share a common lower energy levels with the HFS transitions within the rotational ground state. Results. Toward all four sources, we observe the 3.264 GHz lower satellite line in enhanced emission with its relative intensity higher than its expected value at LTE by a factor between 4 and 20. Employing recently calculated collisional rate coefficients, we perform statistical equilibrium calculations with the non-LTE radiative transfer code MOLPOP-CEP in order to model the excitation conditions traced by the ground state HFS lines of CH and to infer the physical conditions in the emitting regions. The models account for effects of far-infrared line overlap with additional constraints provided by reliable column densities of CH estimated from the 149 μm lines. Conclusions. The derived gas densities indicate that the CH radio emission lines (and the far-infrared absorption) arise from the diffuse and translucent outer regions of the SFRs’ envelopes as well as in such clouds located along the lines of sight. We infer temperatures ranging from 50 to 125 K. These elevated temperatures, together with astrochemical considerations, may indicate that CH is formed in material heated by the dissipation of interstellar turbulence, which has been invoked for other molecules. The excitation conditions we derive reproduce the observed level inversion in all three of the ground state HFS lines of CH over a wide range of gas densities with an excitation temperature of ∼−0.3 K, consistent with previous theoretical predictions.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"36 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89595329","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"N-body simulations of planet formation via pebble accretion. II. How to form various giant planets","authors":"S. Matsumura, R. Brasser, S. Ida","doi":"10.1051/0004-6361/202039210","DOIUrl":"https://doi.org/10.1051/0004-6361/202039210","url":null,"abstract":"Aims. The connection between initial disc conditions and final orbital and physical properties of planets is not well-understood. In this paper, we numerically study the formation of planetary systems via pebble accretion and investigate the effects of disc properties such as masses, dissipation timescales, and metallicities on planet formation outcomes. Methods. We improved the N-body code SyMBA that was modified for our paper I by taking account of new planet-disc interaction models and type II migration. We adopted the ‘two-α’ disc model to mimic the effects of both the standard disc turbulence and the mass accretion driven by the magnetic disc wind. Results. We successfully reproduced the overall distribution trends of semi-major axes, eccentricities, and planetary masses of extrasolar giant planets. There are two types of giant planet formation trends, depending on whether or not the disc’s dissipation timescales are comparable to the planet formation timescales. When planet formation happens fast enough, giant planets are fully grown (Jupiter mass or higher) and are distributed widely across the disc. On the other hand, when planet formation is limited by the disc’s dissipation, discs generally form low-mass cold Jupiters (CJs). Our simulations also naturally explain why hot Jupiters (HJs) tend to be alone and how the observed eccentricity-metallicity trends arise. The low-metallicity discs tend to form nearly circular and coplanar HJs in situ, because planet formation is slower than high-metallicity discs, and thus protoplanetary cores migrate significantly before gas accretion. The high-metallicity discs, on the other hand, generate HJs in situ or via tidal circularisation of eccentric orbits. Both pathways usually involve dynamical instabilities, and thus HJs tend to have broader eccentricity and inclination distributions. When giant planets with very wide orbits (’super-cold Jupiters’) are formed via pebble accretion followed by scattering, we predict that they belong to metal-rich stars, have eccentric orbits, and tend to have (∼ 80%) companions interior to their orbits.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"13 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85342498","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}