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1.
Srinivasan G. Bhattacharya D. Dwarakanath K. S. 《Journal of Astrophysics and Astronomy》1984,5(4):403-423
We conclude that pulsar-driven supernova remnants (SNRs) are extremely rare objects. Indeed an analysis of the known sample
of plerions suggests a very low birthrate ∼ 1 in 240 years. Long-lived and bright plerions like the Crab nebula are likely
to be produced only when the pulsar has an initial period ∼ 10–20 milliseconds and a field ∼ 1012 G. Such pulsars inside rapidly expanding shell remnants should also produce detectable plerions. The extreme rarity of SNRs
with such hybrid morphology leads us to conclude that these pulsars must have been born with an initial period larger than
∼ 35–70 milliseconds.
Joint Astronomy Program, Department of Physics, Indian Institute of Science, Bangalore 560012. 相似文献
2.
We have reanalysed a homogeneous catalogue of shell-type supernova remnants and we find that the radio data are consistent
with a birthrate of one in 22±3 yr. Our approach is based on the secular decrease of surface brightness of the historical
remnants whose ages are precisely known. The abovementioned birthrate is significantly higher than most previous estimates
which range from one in 50–150 yr, and is consistent with the supernova rate in our galaxy derived from historical observations,
as well as with recent estimates of the pulsar birthrate. 相似文献
3.
We use the recently introduced concept of a ‘window’ of magnetic field strengths in which pulsars can be active to explain
the variation in morphology of supernova remnants. The striking difference between shell-type and filled-type remnants is
attributed to differences in he magnetic field strengths of the neutron stars left by the respective Supernovae. Field strengths
of a value permitting pulsar activity result in particle production and Crab-like centrally concentrated remnants. Other field
values lead to strong magnetic dipole radiation and consequent shell formation (e.g. Cas A). Several apparent inconsistencies concerning pulsar-supernova associations appear to find a logical explanation on
the basis of this hypothesis. 相似文献
4.
The Fermi γ-ray space telescope reported the observation of several Galactic supernova remnants recently, with the γ-ray spectra well described by hadronic pp collisions. The possible neutrino emissions from these Fermi detected supernova remnants are discussed in this work, assuming the hadronic origin of the γ-ray emission. The muon event rates induced by the neutrinos from these supernova remnants on typical km3 neutrino telescopes, such as the IceCube and the KM3NeT, are calculated. The results show that for most of these supernova remnants the neutrino signals are too weak to be detected by the on-going or up-coming neutrino experiment. Only for the TeV bright sources RX J1713.7-3946 and possibly W28 the neutrino signals can be comparable with the atmospheric background in the TeV region, if the protons can be accelerated to very high energies. The northern hemisphere based neutrino telescope might detect the neutrinos from these two sources. 相似文献
5.
The role of nearby galactic sources, the supernova remnants, in formation of observed energy spectrum and large-scale anisotropy of high-energy cosmic rays is studied. The list of these sources is made up based on radio, X-ray and gamma-ray catalogues. The distant sources are treated statistically as ensemble of sources with random positions and ages. The source spectra are defined based on the modern theory of cosmic ray acceleration in supernova remnants while the propagation of cosmic rays in the interstellar medium is described in the frameworks of galactic diffusion model. Calculations of dipole component of anisotropy are made to reproduce the experimental procedure of “two-dimensional” anisotropy measurements. The energy dependence of particle escape time in the process of acceleration in supernova remnants and the arm structure of sources defining the significant features of anisotropy are also taken into account. The essential new trait of the model is a decreasing number of core collapse SNRs being able to accelerate cosmic rays up to the given energy, that leads to steeper total cosmic ray source spectrum in comparison with the individual source spectrum. We explained simultaneously the new cosmic ray data on the fine structure of all particle spectrum around the knee and the amplitude and direction of the dipole component of anisotropy in the wide energy range 1 TeV–1 EeV. Suggested assumptions do not look exotic, and they confirm the modern understanding of cosmic ray origin. 相似文献
6.
The case is made for most cosmic rays having come from galactic sources. ‘Structure’, i.e. a lack of smoothness in the energy spectrum, is apparent, strengthening the view that most cosmic rays come from discrete sources, supernova remnants being most likely. 相似文献
7.
We argue that the cosmic ray positron excess observed in ATIC-2, Fermi LAT, PAMELA, HESS and recently in the precision AMS-02 experiment can be attributed to production in a local, middle-aged supernova remnant (SNR). Using the prediction of our model of cosmic ray acceleration in SNR we estimate that the SNR responsible for the observed positron excess is located between 250 and 320pc from the Sun and is 170–380 kyear old. The most probable candidate for such a source is the SNR which gave birth to the well-known Geminga pulsar, but is no longer visible. Other contenders are also discussed. 相似文献
8.
We have used the enhanced MERLIN at 1.5 and 5 GHz to image the central 700pc of the nearby starburst galaxy M82. Of order 40 discrete sources are detected and it appears that most of these sources are supernova remnants. Not only do many show shell structure and have a non-thermal radio spectrum, but they also follow a surface brightness/diameter relation consistent with that found in the LMC and Galactic supernova remnants. The detected M82 remnants are more compact and brighter than Galactic remnants which implies that they must be less than a few hundred years old and hence supernova rates are of order 0.05 per year. The 1.5 GHz measurements have shown that many of the remnants have low-frequency spectral turnovers which are probably due to free-free absorption in localised ionised gas with emission measures > 106 pc cm–6. 相似文献
9.
X. Ribeyre L. Hallo V. T. Tikhonchuk S. Bouquet J. Sanz 《Astrophysics and Space Science》2007,307(1-3):169-172
The Rayleigh-Taylor instability (RTI) plays an important role in the dynamics of several astronomical objects, in particular,
in the supernovae (SN) evolution. In the present paper we examine the dynamics of a shell (representing a type II SN remnant)
blown-up by a wind emitted by a central pulsar. The shell is accelerated by the pulsar wind and its inner surface experiences
the RTI. We develop an analytical approach by using a specific transformation into the coordinate frame co-moving with the
SN ejecta. We first derive a non-stationary spherically symmetric solution describing an expansion of a gas shell under the
pressure of a central source (pulsar). Then, we analyze its 3D stability with respect to a small perturbation on the inner
shell surface. The dispersion relation is derived in the co-moving reference frame. The growth rate of the perturbation is
found and its temporal evolution is discussed. We compare our result with the previous published studies and apply it to the
Crab nebula evolution. 相似文献
10.
In this paper, we present high-energy neutrino spectra from 21 Galactic supernova remnants (SNRs), derived from gamma-ray measurements in the GeV–TeV range. We find that only the strongest sources, i.e. G40.5-0.5 in the north and Vela Junior in the south could be detected as single point sources by IceCube or KM3NeT, respectively. For the first time, it is also possible to derive a diffuse signal by applying the observed correlation between gamma-ray emission and radio signal. Radio data from 234 supernova remnants listed in Green’s catalog are used to show that the total diffuse neutrino flux is approximately a factor of 2.5 higher compared to the sources that are resolved so far. We show that the signal at above 10 TeV energies can actually become comparable to the diffuse neutrino flux component from interactions in the interstellar medium. Recently, the IceCube collaboration announced the detection of a first diffuse signal of astrophysical high-energy neutrinos. Directional information cannot unambiguously reveal the nature of the sources at this point due to low statistics. A number of events come from close to the Galactic center and one of the main questions is whether at least a part of the signal can be of Galactic nature. In this paper, we show that the diffuse flux from well-resolved SNRs is at least a factor of 20 below the observed flux. 相似文献
11.
We investigated the kinematics of the pulsar wind nebula (PWN) in the old supernova remnant CTB 80 using the Fabry-Perot interferometer of the 6-m Special Astrophysical Observatory telescope. In addition to the previously known expansion of the system of bright filaments with a velocity of 100–200 km s?1, we detected weak high-velocity features in the Hα line at least up to velocities of 400–450 km s?1. We analyzed the morphology of the PWN in the Hα, [S II], and [O III] lines using HST archival data and discuss its nature. The shape of the central filamentary shell, which is determined by the emission in the [O III] line and in the radio continuum, is shown to be consistent with the bow-shock model for a significant (about 60°) inclination of the pulsar’s velocity vector to the plane of the sky. In this case, the space velocity of the pulsar is twice as high as its tangential velocity, i.e., it reaches ?500 km s?1, and PSR B1951+32 is the first pulsar whose radial velocity about 40 km s?1 has been estimated from PWN observations. The shell-like Hα-structures outside the bow shock front in the east and the west could be associated with both the pulsar’s jets and the pulsar wind breakthrough due to the layered structure of the extended CTB 80 shell. 相似文献
12.
R. K. Kochhar 《Journal of Astrophysics and Astronomy》1981,2(1):87-93
We propose that single stars in the mass range 4–6·5M
⊙, that explode as Supernovae of Type I, are totally disrupted by the explosion and form shell-type remnants. More massive
single stars which explode as Supernovae of Type II also give rise to shell-type remnants, but in this case a neutron star
or a black hole is left behind. The first supernova explosion in a close binary also gives rise to a shell-type supernova
remnant. The Crab-like filled-centre supernova remnants are formed by the second supernova explosion in a close binary. The
hybrid supernova remnants, consisting of a filled centre surrounded by a shell, are formed if there is an active neutron star
inside the shell. 相似文献
13.
N. N. Kalinichenko 《Astrophysics and Space Science》2009,319(2-4):131-138
Interplanetary scintillation observations of eleven supernova remnants and the pulsar J1939+2134, around which the existence of a supernova remnant remains obscure, were carried out with the largest in the world decameter radio telescope UTR-2 at 20, 25 and 30 MHz to determine if any of them contain compact radio sources with the angular size θ<5″. The sample included the young Galactic remnants and the other powerful SNRs. The interplanetary scintillations of the compact radio source in the Crab Nebula associated with the well-known pulsar J0534+2200 and the pulsar J1939+2134 were observed. Apart from the Crab Nebula, we have not detected a compact radio source in supernova remnants with the angular size θ<5″ and the flux density more than 10 Jy. The observations do not confirm the existence of the low frequency compact source in Cassiopeia A that has remained controversial. 相似文献
14.
宇宙线的起源是高能天体物理的核心问题之一.一直以来,超新星爆发被认为是能谱膝区以下宇宙线的主要来源.多波段观测表明,超新星遗迹有能力加速带电粒子至亚PeV (10~(15)eV)能量.扩散激波加速被认为是最有效的天体高能粒子加速机制之一,而超新星遗迹的大尺度激波正好为这一机制提供平台.近年来,一系列较高精度的地面和空间实验极大地推动了对宇宙线以及超新星遗迹的研究.新的观测事实挑战着传统的扩散激波加速模型以及其在银河系宇宙线超新星遗迹起源学说上的应用,深化了人们对宇宙高能现象的认识.结合超新星遗迹辐射能谱的时间演化特性,构建的时间依赖的超新星遗迹粒子加速模型,不仅能够解释200 GV附近宇宙线的能谱反常,还自然地形成能谱膝区,甚至可以将超新星遗迹粒子加速对宇宙线能谱的贡献延伸至踝区.该模型预期超新星遗迹中粒子的输运行为表现为湍流扩散,这需要未来的观测以及与粒子输运相关的等离子体数值模拟工作来进一步验证. 相似文献
15.
In this paper, we discuss known discrepancies between theoretically derived and empirically measured relations between the radio surface brightness Σ and the diameter D of supernova remnants (SNRs): these relations are commonly known as the Σ–D relations. We argue that these discrepancies may be at least partially explained by taking into account thermal emission at radio frequencies from SNRs at particular evolutionary stages and located in particular environments. The major contributions of this paper may be summarized as follows: (i) we consider thermal emission at radio frequencies from SNRs in the following scenarios: a relatively young SNR evolving in a dense molecular cloud environment (n 100–1000 cm−3) and an extremely evolved SNR expanding in a dense warm medium (n 1–10 cm−3). Both of these SNRs are assumed to be in the adiabatic phase of evolution. We develop models of the radio emission from both of these types of SNRs and each of these models demonstrate that through the thermal bremsstrahlung process significant thermal emission at radio frequencies is expected from both types of SNR. Based on a literature search, we claim that thermal absorption or emission at radio frequencies has been detected for one evolved Galactic SNR and four young Galactic SNRs with similar properties to our modelled evolved and young SNRs. (ii) We construct artificial radio spectra for both of these two types of SNRs: in particular, we discuss our simulated spectrum for the evolved Galactic SNR OA 184. By including thermal emission in our simulated spectra, we obtain different slopes in Σ–D relations: these new slopes are in closer agreement to empirically obtained relations than the theoretically derived relations which do not take thermal emission into account. (iii) Lastly, we present an additional modification to the theoretical Σ–D relation for SNRs in the adiabatic expansion phase. This modification is based on the convolution of the synchrotron emissivity with the emissivity derived in this paper for thermal bremsstrahlung emission from an ionized gas cloud (that is, a theoretical construct of an SNR). 相似文献
16.
Sidney Van den Bergh 《Journal of Astrophysics and Astronomy》1980,1(1):67-70
A massive binary, in which the primary becomes a supernova, should leave a luminous secondary near the centre of its remnant.
Contrary to expectation no statistically significant excess of OB stars is, however, found near the centres of optically visible
galactic supernova remnants. 相似文献
17.
We study the self-similar magnetohydrodynamics (MHD) of a quasi-spherical expanding void (viz. cavity or bubble) surrounding the centre of a self-gravitating gas sphere with a general polytropic equation of state. We show various analytic asymptotic solutions near the void boundary in different parameter regimes and obtain the corresponding void solutions by extensive numerical explorations. We find novel void solutions of zero density on the void boundary. These new void solutions exist only in a general polytropic gas and feature shell-type density profiles. These void solutions, if not encountering the magnetosonic critical curve (MCC), generally approach the asymptotic expansion solution far from the central void with a velocity proportional to radial distance. We identify and examine free-expansion solutions, Einstein–de Sitter expansion solutions, and thermal-expansion solutions in three different parameter regimes. Under certain conditions, void solutions may cross the MCC either smoothly or by MHD shocks, and then merge into asymptotic solutions with finite velocity and density far from the centre. Our general polytropic MHD void solutions provide physical insight for void evolution, and may have astrophysical applications such as massive star collapses and explosions, shell-type supernova remnants and hot bubbles in the interstellar and intergalactic media, and planetary nebulae. 相似文献
18.
Radio observations shows that young supernova remnants such as Tycho and Cas A generally exhibit a circular clumpy shell. This shell shows a radial magnetic field whose equipartition strength is 2 to 3 orders of magnitude higher than the interstellar field. A simple compression of the ambient field by the shock can explain neither of these observations. We show that the Rayleigh-Taylor instability which occurs at the ejecta/ISM interface can explain these observations. We have done MHD simulations of the instability in the shell of Type-I supernova remnants for the first time by utilizing moving grid technique. Our simulation shows that Rayleigh-Taylor and Kelvin-Helmholtz instabilities amplify ambient magnetic fields locally and produce the clumpy radio shell. Strong magnetic field lines draped around the Rayleigh-Taylor fingers produce the radial B-vector polarization, whereas thermal bremsstrahlung from the dense fingers themselves produce the clumpy X-ray emission. 相似文献
19.
D. Michielsen S. De Rijcke H. Dejonghe W. W. Zeilinger G. K. T. Hau 《Astrophysics and Space Science》2003,284(2):635-638
We present deep Hα+[NII] narrowband imaging of FCC046 and FCC207, two dwarf ellipticals (dEs) in the Fornax Cluster. Although
one does not expect much of an interstellar medium (ISM) to be present in dEs, FCC207 shows a central emission region, whereas
FCC046 also contains fainter emission regions. The central emission can be explained as photo-ionization by post-AGB stars.
Some of the emission clouds in FCC046 are resolved and have diameters of the order of 50-150 pc and Hα luminosities of 1030 W, comparable to supernova remnants (SNRs), pointing to recent star formation. Dwarfs like FCC046 could be the evolutionary
link between normal, quiescent dEs and more vigorously starforming blue compact dwarfs (BCDs).
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
20.
Ni Chen-ping 《Chinese Astronomy and Astrophysics》1990,14(4):422-428
The supernova exploded at the boundary of a dense molecular cloud in a diffuse gas. The eastern half of the shock wave entered the diffuse gas and is now in the stage of adiabatic expansion, forming the observed semicircular remnant; the western half entered the dense cloud, moved at a much slower speed and is now in the pressure-driven snowplow phase, the radiation it emits is in the uv, and is completely absorbed by the interstellar gas along the line of sight. 相似文献