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1.
P. S. Negi 《Astrophysics and Space Science》2011,332(1):145-153
We construct for the first time, the sequences of stable neutron star (NS) models capable of explaining simultaneously, the
glitch healing parameters, Q, of both the pulsars, the Crab (Q≥0.7) and the Vela (Q≤0.2), on the basis of starquake mechanism of glitch generation, whereas the conventional NS models cannot give such consistent
explanation. Furthermore, our models also yield an upper bound on NS masses similar to those obtained in the literature for
a variety of modern equations of state (EOSs) compatible with causality and dynamical stability. If the lower limit of the
observational constraint of (i) Q≥0.7 for the Crab pulsar and (ii) the recent value of the moment of inertia for the Crab pulsar (evaluated on the basis of
time-dependent acceleration model of the Crab Nebula), I
Crab,45≥1.93 (where I
45=I/1045 g cm2), both are imposed together on our models, the models yield the value of matching density, E
b
=9.584×1014 g cm−3 at the core-envelope boundary. This value of matching density yields a model-independent upper bound on neutron star masses,
M
max≤2.22M
⊙, and the strong lower bounds on surface redshift z
R
≃0.6232 and mass M≃2.11M
⊙ for the Crab (Q≃0.7) and the strong upper bound on surface redshift z
R
≃0.2016, mass M≃0.982M
⊙ and the moment of inertia I
Vela,45≃0.587 for the Vela (Q≃0.2) pulsar. However, for the observational constraint of the ‘central’ weighted mean value Q≈0.72, and I
Crab,45>1.93, for the Crab pulsar, the minimum surface redshift and mass of the Crab pulsar are slightly increased to the values
z
R
≃0.655 and M≃2.149M
⊙ respectively, whereas corresponding to the ‘central’ weighted mean value Q≈0.12 for the Vela pulsar, the maximum surface redshift, mass and the moment of inertia for the Vela pulsar are slightly decreased
to the values z
R
≃0.1645, M≃0.828M
⊙ and I
Vela,45≃0.459 respectively. These results set an upper and lower bound on the energy of a gravitationally redshifted electron-positron
annihilation line in the range of about 0.309–0.315 MeV from the Crab and in the range of about 0.425–0.439 MeV from the Vela
pulsar. 相似文献
2.
Low noise photoelectric measurements of the line profile of the g = 0 Fe line gl 5576.097 combined with determinations of the wavelength shift of its centre calibrated by use of an I
2 absorption tube are reported. Measurements taken at various limb distances (1.0 cos 0.2) and along 4 different diameters of the Sun are used to investigate the behaviour of the line asymmetry (C-shape) and wavelength shift of the line centre as functions of cos and of latitude and to search for possible pole-equator differences.An accuracy of approx. 0.8 mÅ r.m.s. is achieved for the determination of the centre of the solar line relative to the iodine lines and of 0.3 mÅ to 1 mÅ r.m.s. for the relative variations of the C-shape. The analysis shows a significant difference between the limb-effect curves along polar and equatorial diameters for cos 0.4 and changes of the C-shape for 0.9 cos 0.6 with a rather strong indication of a latitude dependence of the C-shape. This latitude dependence may account for the so-called ears observed by Howard et al. (1980) who used the well-known Doppler compensator method which integrates the line asymmetry from the line wings to the core.Mitteilungen aus dem Kiepenheuer-Institut Nr. 207. 相似文献
3.
The infrared emission observed for dust in the Trapezium nebula over the waveband 8–40 m cannot be explained on the basis of a simple silicate model involving either terrestrial or lunar silicates. Laboratory measurements were carried out to determine the opacity coefficient of finely crushed Murchison meteorite material. Murchison material (including organics within it) provides a better fit to the Trapezium data than any known silicate, but the agreement is inferior to that obtained for a diatom model. 相似文献
4.
V. A. Bronshten 《Astronomy Letters》2000,26(5):328-330
We consider the history of discovery and justify the existence in the Solar system of a new class of bodies—minicomets, i.e., bodies of cometary nature and composition but of low mass. Two classes of minicomets are distinguished: icy ones similar to the Tunguska meteorite, and snow ones, which break up at high altitudes. 相似文献
5.
S.-I. Akasofu 《Planetary and Space Science》1979,27(7):1039-1041
When the interplanetary parameter exceeds the amount that can be dissipated by the ionosphere in terms of the Joule heat production, the excess energy is absorbed by the ring current belt, resulting in abnormal growth of the Dst index. 相似文献
6.
Zhen-Yu Wu Jia-Ji Wang Li ChenShanghai Astronomical Observatory Chinese Academy of Sciences Shanghai National Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2002,2(3):216-225
We examine 14 plates of the globular cluster M3 (NGC 5272) taken with the 40 cm refractor at the Sheshan station of Shanghai Astronomical Observatory. The plates span over a period of about 77 years. The positions and absolute proper motions of eight stars in the Hipparcos Catalogue and of 49 stars in the Tycho-2 Catalogue are used as the reference frame. The astrometric reduction is made with the central overlapping principle. The absolute proper motions of 534 stars in a region of about 100' × 100' around the cluster are measured. With the new proper motion data the membership probabilities of the stars are determined. The average absolute proper motion obtained for the cluster is -0.06@0.30 mas yr-1 in R.A. and -2.6@0.30 mas yr-1 in Decl. By combining this result with the known distance and radial velocity of the cluster, we also obtained the Galactic orbit of M3 for a chosen three-component Galactic potential. 相似文献
7.
M. Catelan 《Astrophysics and Space Science》2009,320(4):261-309
We review and discuss horizontal branch (HB) stars in a broad astrophysical context, including both variable and non-variable
stars. A reassessment of the Oosterhoff dichotomy is presented, which provides unprecedented detail regarding its origin and
systematics. We show that the Oosterhoff dichotomy and the distribution of globular clusters in the HB morphology-metallicity
plane both exclude, with high statistical significance, the possibility that the Galactic halo may have formed from the accretion
of dwarf galaxies resembling present-day Milky Way satellites such as Fornax, Sagittarius, and the LMC—an argument which,
due to its strong reliance on the ancient RR Lyrae stars, is essentially independent of the chemical evolution of these systems
after the very earliest epochs in the Galaxy’s history. Convenient analytical fits to isochrones in the HB type–[Fe/H] plane
are also provided. In this sense, a rediscussion of the second-parameter problem is also presented, focusing on the cases
of NGC 288/NGC 362, M13/M3, the extreme outer-halo globular clusters with predominantly red HBs, and the metal-rich globular
clusters NGC 6388 and NGC 6441. The recently revived possibility that the helium abundance may play an important role as a
second parameter is also addressed, and possible constraints on this scenario discussed. We critically discuss the possibility
that the observed properties of HB stars in NGC 6388 and NGC 6441 might be accounted for if these clusters possess a relatively
minor population of helium-enriched stars. A technique is proposed to estimate the HB types of extragalactic globular clusters
on the basis of integrated far-UV photometry. The importance of bright type II Cepheids as tracers of faint blue HB stars
in distant systems is also emphasized. The relationship between the absolute V magnitude of the HB at the RR Lyrae level and metallicity, as obtained on the basis of trigonometric parallax measurements
for the star RR Lyr, is also revisited. Taking into due account the evolutionary status of RR Lyr, the derived relation implies
a true distance modulus to the LMC of (m–M)0=18.44±0.11. Techniques providing discrepant slopes and zero points for the M
V
(RRL)–[Fe/H] relation are briefly discussed. We provide a convenient analytical fit to theoretical model predictions for the
period change rates of RR Lyrae stars in globular clusters, and compare the model results with the available data. Finally,
the conductive opacities used in evolutionary calculations of low-mass stars are also investigated.
M. Catelan is John Simon Guggenheim Memorial Foundation Fellow. 相似文献
8.
Juan Garcia Escudero 《中国天文和天体物理学报》2003,3(3):235-240
We present an application of the methods recently developed for the study of quasicrystal structures to the analysis of multiperiodicity of semiregular variables. A light curve analysis of UW Her shows frequencies that can be included within the general scheme characterizing the Fourier spectra of Fibonacci quasiperiodic sequences. The analysed data come from the BAA Variable Star Section computerised archive. 相似文献
9.
10.
Donald V. Reames 《Solar physics》2018,293(3):47
We find that the element abundances in solar energetic particles (SEPs) and in the slow solar wind (SSW), relative to those in the photosphere, show different patterns as a function of the first ionization potential (FIP) of the elements. Generally, the SEP and SSW abundances reflect abundance samples of the solar corona, where low-FIP elements, ionized in the chromosphere, are more efficiently conveyed upward to the corona than high-FIP elements that are initially neutral atoms. Abundances of the elements, especially C, P, and S, show a crossover from low to high FIP at \({\approx}\,10~\mbox{eV}\) in the SEPs but \({\approx}\,14~\mbox{eV}\) for the solar wind. Naively, this seems to suggest cooler plasma from sunspots beneath active regions. More likely, if the ponderomotive force of Alfvén waves preferentially conveys low-FIP ions into the corona, the source plasma that eventually will be shock-accelerated as SEPs originates in magnetic structures where Alfvén waves resonate with the loop length on closed magnetic field lines. This concentrates FIP fractionation near the top of the chromosphere. Meanwhile, the source of the SSW may lie near the base of diverging open-field lines surrounding, but outside of, active regions, where such resonance does not exist, allowing fractionation throughout the chromosphere. We also find that energetic particles accelerated from the solar wind itself by shock waves at corotating interaction regions, generally beyond 1 AU, confirm the FIP pattern of the solar wind. 相似文献
11.
Eckhard Sturm 《天文研究与技术》2003,(Z1)
1 IntroductionDeepsurveyscarriedoutbyfutureinfraredmissions (suchasSIRTForSOFIA)willsampleinfraredbrightgalaxiesoverawiderangeofredshiftsandluminosities.Quantitativespectroscopyofmid infraredemissionlineswillbeanimportantdiagnostictoolfordeterminingthedetailedpropertiesofdistant,dustygalaxies ,thesourceoftheextragalacticbackground ,andtheoriginofnuclearactivityingalaxies.Manyofthefundamentalquestionsofgalaxyformationandevolutiondependsubstantiallyonthefractionofthetotalenergyoutputofdista… 相似文献
12.
Coronal holes (CH) emit significantly less at coronal temperatures than quiet-Sun regions (QS), but can hardly be distinguished in most chromospheric and lower transition region lines. A key quantity for the understanding of this phenomenon is the magnetic field. We use data from SOHO/MDI to reconstruct the magnetic field in coronal holes and the quiet Sun with the help of a potential magnetic model. Starting from a regular grid on the solar surface we then trace field lines, which provide the overall geometry of the 3D magnetic field structure. We distinguish between open and closed field lines, with the closed field lines being assumed to represent magnetic loops. We then try to compute some properties of coronal loops. The loops in the coronal holes (CH) are found to be on average flatter than in the QS. High and long closed loops are extremely rare, whereas short and low-lying loops are almost as abundant in coronal holes as in the quiet Sun. When interpreted in the light of loop scaling laws this result suggests an explanation for the relatively strong chromospheric and transition region emission (many low-lying, short loops), but the weak coronal emission (few high and long loops) in coronal holes. In spite of this contrast our calculations also suggest that a significant fraction of the cool emission in CHs comes from the open flux regions. Despite these insights provided by the magnetic field line statistics further work is needed to obtain a definite answer to the question if loop statistics explain the differences between coronal holes and the quiet Sun. 相似文献
13.
Zhan-Le Du Hua-Ning Wang Xiang-Tao He National Astronomical Observatories Chinese Academy of Sciences Beijing Department of Astronomy Beijing Normal University Beijing 《中国天文和天体物理学报》2006,6(4):489-494
The maximum amplitudes of solar activity cycles are found to be well anti-correlated (r = -0.72) with the newly defined solar cycle lengths three cycles before (at lag -3) in 13-month running mean sunspot numbers during the past 190 years. This result could be used for predicting the maximum sunspot numbers. The amplitudes of Cycles 24 and 25 are estimated to be 149.5±27.6 and 144.3±27.6, respectively. 相似文献
14.
G. S. Kurbasova S. V. Kurbasov M. N. Rybalova G. N. Shlikar’ 《Bulletin of the Crimean Astrophysical Observatory》2008,104(1):150-154
By means of spectral analysis, oscillations have been detected in many-year time series of deviations in the duration of days from the standard that cannot be explained within the framework of existing gravitational theory. The solution of the problem of the origin and structure of these oscillations is associated with the essence of the phenomena taking place inside the Earth and the mechanisms of energy transfer by external fields and the Sun. The effect of the Sun on the Earth’s rotation also leads to the formation of a unified cyclic background, resulting in correlated oscillations in all shells of the Earth, as well as in its atmosphere and its nucleus. Ground magnetic fields of the Earth and the Sun play the leading role in the abovementioned unified cyclic process. The results of spectral autoregressive and wavelet analyses of experimental data concerning deviations in the duration of days from the standard in the years 1832–2006, ground geomagnetic field intensities in 1832–2006, and the mean magnetic field of the Sun during the period from 1975 to 2005 have been discussed in this paper to reveal and compare correlating oscillations. To analyze a short-period (31-yr-long) series of daily data on the mean magnetic field of the Sun, the results of wavelet transformations (the Morlet wavelet) of the detected amplitude of a burst envelope with a carrier frequency of 13 cycles/yr have been obtained. 相似文献
15.
《天文和天体物理学研究(英文版)》2017,(10)
XB 1254–690 is a dipping low mass X-ray binary system hosting a neutron star and showing type I X-ray bursts. We aim at obtaining a more accurate orbital ephemeris and at constraining the orbital period derivative of the system for the first time. In addition, we want to better constrain the distance to the source in order to locate the system in a well defined evolutive scenario. We apply, for the first time, an orbital timing technique to XB 1254–690, using the arrival times of the dips present in the light curves that have been collected during 26 yr of X-ray pointed observations acquired from different space missions. We estimate the dip arrival times using a statistical method that weights the count-rate inside the dip with respect to the level of persistent emission outside the dip. We fit the obtained delays as a function of the orbital cycles both with a linear and a quadratic function. We infer the orbital ephemeris of XB 1254–690, improving the accuracy of the orbital period with respect to previous estimates. We infer a mass of M_2 = 0.42 ± 0.04 M_⊙for the donor star, in agreement with estimations already present in literature, assuming that the star is in thermal equilibrium while it transfers part of its mass via the inner Lagrangian point, and assuming a neutron star mass of 1.4 M_⊙. Using these assumptions, we also constrain the distance to the source, finding a value of 7.6±0.8 kpc. Finally, we discuss the evolution of the system, suggesting that it is compatible with a conservative mass transfer driven by magnetic braking. 相似文献
16.
G. A. krasinsky 《Celestial Mechanics and Dynamical Astronomy》1999,75(1):39-66
Analytical expressions for tidal torques induced by a tide‐arising planet which perturbs rotation of a nonrigid body are derived.
Corresponding expressions both for secular and periodic perturbations of the Euler's angles are given for the case of the
earth's rotation. Centennial secular rates of the nutation angle θ and of the earth's angular velocity ω, as well as the centennial
logarithmic decrement ν of the Chandler wobble are evaluated:
mas,
.
In the Universal Time (UT) a large out‐of‐phase (sine) dissipative term with the period 18.6 years and the amplitude 2.3 ms
is found. Corrections to nutation coefficients, which presumably have not been taken into account in IAU theory, are given.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
Xi-Yun Hou Hai-Hong Wang Lin Liu Department of Astronomy Nanjing University Nanjing : Institute of Space Environment Astronautics Nanjing University Nanjing 《中国天文和天体物理学报》2006,6(3):372-378
Collinear libration points play an important role in deep space exploration because of their special positions and dynamical characteristics. Since motion around them is unstable, we need to control the spacecraft if we wish to keep them around such a libration point for a long time. Here we propose a continuous low-thrust control strategy, illustrated with numerical simulations combined with the orbit design and control of the World Space Observatory/UltraViolet (WSO/UV). 相似文献
18.
The effects of solid and ocean tides have been computed on the right ascension of the ascending node of the two LAGEOS and LARES satellites and on the argument of pericenter of LAGEOS II. Their effects—together with the possible mis-modeling related to systematic errors in the estimate of the tidal coefficients, especially in the case of ocean tides—are quite important to be well established for the key role of the LAGEOS satellites, as well as of the newly LARES, in space geodesy and geophysics as well as in fundamental physics measurements. In the case of the measurement of the Lense–Thirring effect, the mis-modeling of long-period tides may mimic a secular effect on the cited orbital elements, thus producing a degradation in the measurement of the relativistic precession. A suitable combination of the orbital elements of the three satellites can help in avoiding the effects of the long-period tides of degree \(\ell =2\) (as for the Lunar solid tides with periods of 18.6 and 9.3 years) and \(\ell =4\), but other long-period tides, as the ocean \(K_1\) tide, which has the same periodicities of the right ascension of the ascending node \(\varOmega \) of the satellites, may strongly influence the measurement, especially if it is performed over a relatively short time span. These results are particularly important in the case of LARES, since they are new and because of the role that the orbit of LARES, and especially of its ascending node right ascension, will have in a new measurement of the Lense–Thirring effect by the joint analysis of its orbit with that of the two LAGEOS. 相似文献
19.
Rui-Jing Lu~ 《中国天文和天体物理学报》2006,(1)
We investigate the relationship between the rise width and the full width of gamma-ray burst pulses.Theoretical analysis shows that either width is proportional to Γ~(-2)Δ_(Тθ),FWHM(RRc)/c(Γ the Lorentz factor of the bulk motion,Δ_(Тθ),FWHM a local pulse's width,R_c the radius of fireballs and c the velocity of light).We study the relationship for four samples of observed pulses.We find:(1)merely the curvature effect could reproduce the relationship between the rise and full widths with the same slope as derived from the model of Qin et al.;(2)gamma-ray burst pulses,selected from both the short and long GRBs,follow the same sequence in the rise width vs. full width diagram,with the shorter pulses at one end;(3)all GRBs may intrinsically result from local Gaussian pulses.These features place constraints on the physical mechanism(s)for producing long and short GRBs. 相似文献