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1.
Primordial black holes (PBHs) are known to be produced from collapsing cosmic defects such as domain walls and strings. In this paper we show how PBHs are produced in monopole-string networks.  相似文献   

2.
Formation of primordial black holes (PBHs) on astrophysical mass scales is a natural consequence of inflationary cosmology, if the primordial perturbation spectrum has a large and negative running of the spectral index as observationally suggested today because double inflation is required to explain it and fluctuations on some astrophysical scales are enhanced in the field-oscillation regime in between. It is argued that PBHs thus produced can serve as intermediate-mass black holes (IMBHs), which act as the observed ultraluminous X-ray sources (ULXs) by choosing appropriate values of the model parameters in their natural ranges. Our scenario can be observationally tested in near future because the mass of PBHs is uniquely determined once we specify the values of the amplitude of the curvature perturbation, spectral index and its running on large scales.  相似文献   

3.
Primordial Black Holes (PBHs) are gravitationally collapsed objects that may have been created by density fluctuations in the early universe and could have arbitrarily small masses down to the Planck scale. Hawking showed that due to quantum effects, a black hole has a temperature inversely proportional to its mass and will emit all species of fundamental particles thermally. PBHs with initial masses of ∼5.0 × 1014 g should be expiring in the present epoch with bursts of high-energy particles, including gamma radiation in the GeV–TeV energy range. The Milagro high energy observatory, which operated from 2000 to 2008, is sensitive to the high end of the PBH evaporation gamma-ray spectrum. Due to its large field-of-view, more than 90% duty cycle and sensitivity up to 100 TeV gamma rays, the Milagro observatory is well suited to perform a search for PBH bursts. Based on a search on the Milagro data, we report new PBH burst rate density upper limits over a range of PBH observation times. In addition, we report the sensitivity of the Milagro successor, the High Altitude Water Cherenkov (HAWC) observatory, to PBH evaporation events.  相似文献   

4.
In this work, we study the evolution of primordial black holes within the context of loop quantum cosmology. First we calculate the scale factor and energy density of the Universe for different cosmic era and then taking these as inputs, we study evolution of primordial black holes. From our estimation it is found that accretion of radiation does not affect evolution of primordial black holes in loop quantum cosmology. We also conclude that due to slow variation of scale factor, the upper bound on initial mass fraction of presently evaporating PBHs are much greater in loop quantum cosmology than the standard case.  相似文献   

5.
Primordial black holes(PBHs) are a profound signature of primordial cosmological structures and provide a theoretical tool to study nontrivial physics of the early Universe.The mechanisms of PBH formation are discussed and observational constraints on the PBH spectrum,or effects of PBH evaporation,are shown to restrict a wide range of particle physics models,predicting an enhancement of the ultraviolet part of the spectrum of density perturbations,early dust-like stages,first order phase transitions and stages of superheavy metastable particle dominance in the early Universe.The mechanism of closed wall contraction can lead,in the inflationary Universe,to a new approach to galaxy formation,involving primordial clouds of massive BHs created around the intermediate mass or supermassive BH and playing the role of galactic seeds.  相似文献   

6.
Primordial black holes (PBHs) are a profound signature of primordial cos-mological structures and provide a theoretical tool to study nontrivial physics of the early Universe. The mechanisms of PBH formation are discussed and observational constraints on the PBH spectrum, or effects of PBH evaporation, are shown to re-strict a wide range of particle physics models, predicting an enhancement of the ul-traviolet part of the spectrum of density perturbations, early dust-like stages, first or-der phase transitions and stages of superheavy metastable particle dominance in the early Universe. The mechanism of closed wall contraction can lead, in the inflation-ary Universe, to a new approach to galaxy formation, involving primordial clouds of massive BHs created around the intermediate mass or supermassive BH and playing the role of galactic seeds.  相似文献   

7.
The search for high energy ray bursts (GRBs) from primordial black holes (PBHs) has continued for the past 20 years. We discuss a very interesting group of GRBs of very short time duration and an increasing hard spectrum from the published BATSE catalog. We point out that the trend, i.e. anti-correlation of hardness ratio vs. GRB duration, would be expected if some of the short GRBs came from black holes evaporation. We discuss the possibility that the onset of the quark-gluon plasma can give rise to such GRB from PBH evaporation.  相似文献   

8.
A new PL-relation (10) — Figure 2 for the Cepheids in the Galaxy, the Magellanic Clouds and M31 has been constructed. On deriving this relation both the period-radius (3) and period-colour relations (7), (8) and (9) are essentially used. The PC-relation (7) determined after the colours of 88 galactic cepheids (Table I), which are obtained from the colour-spectrum relation (6) — Figure 1, common for Cepheids and non-variable supergiants, are used also for the M31 Cepheids, whereas (8) and (9) are for the Large and Small MC Cepheids, respectively, all three PC-relations having a common slope. The comparison of the relations (8) and (9) with (7) shows that the LMC and SMC Cepheids are bluer than the galactic ones with 0m.04 and 0m.19, respectively, probably because of their metal-poor abundance. The places of thes-Cepheids in Figure 2 show that these Cepheids possess a dissimilar PL-relation with a different slope. The reason for such a difference is that thes-Cepheids are first harmonic pulsators. The distance moduli of the three galaxies under discussion are obtained from the PL-relation (10). The colour-coefficient of period-colour-luminosity-relation is briefly discussed. The general conclusion based on a comparison of the PL-relation in the present paper with those by other authors (Table V) is that our PL-relation differs in the zero-point by less than 0m.2; therefore, the manner of constructing the PL-relation by means of PR and PC-relations is reasonable and useful.  相似文献   

9.
Formulas describing synchrotron radiation are extended to include the effect of the presence of an ambient medium and the effect of reabsorption and Faraday rotation on the degree of circular polarization. Results are: (1) The onset of Razin-Tsytovich suppression has no significant effect on the degree of circular polarization. (2) The onset of self-absorption in a source subject to weak Faraday rotation (negligible Faraday rotation in an absorption length) causes the degree of circular polarization to reverse its sign and to decrease (by between one half and one quarter for typical parameters) in magnitude. (3) As in (2) but for strong Faraday rotation (many rotations of the plane of polarization in an absorption length) the degree of circular polarization also reverses its sign and becomes slightly smaller in magnitude than for weak Faraday rotation.The transfer equation including the effects of the polarization is discussed in detail.  相似文献   

10.
It is usually assumed that the ions of cosmic rays contribute nothing to the observable electromagnetic radiation. However, this is true only when these ions are moving in a vacuum or a quiet (nonturbulent) plasma. In the case of fast ions in a turbulent plasma, there is an effective nonlinear mechanism of radiation which is discussed in this paper. The fast ion (relativistic or nonrelativistic) moving in the plasma creates a polarization cloud around itself which also moves with the particles. The turbulent plasma waves may scatter on the moving electric field of this polarization cloud. In the process of this scattering an electromagnetic wave with frequency (2.7) is generated. Let 1 and k1 be the frequency and wave vector of turbulent plasma waves,V is the velocity of the ion, and is the angle between the wave vector of electromagnetic radiation and the direction of the ion velocity. The method of calculating the probability of the conversion of plasma waves (k1) into electromagnetic waves (k) by scattering on an ion with velocityV is described in detal in Section 2 (Equation (2.14)).The spectral coefficients of spontaneous radiation in the case of scattering of plasma waves on polarization clouds created by fast nonrelativistic ions are given in (3.6) for an ion energy distribution function (3.4) and in (3.8) for more general evaluations. The Equations (3.9)–(3.13) describe the spectral coefficients of spontaneous emission for different modes of plasma turbulence (Langmuir (3.9), electron cyclotron in a weak (3.10) or strong (3.11) magnetic field and ion acoustic (3.12)–(3.13) waves). The coefficients of reabsorption or induced emission are given by Equations (3.14) and (3.16)–(3.19). There is a maser effect in the case of scattering of plasma waves on a stream of ions. The effective temperature of the spontaneous emission is given by Equation (3.15). The spectral coefficients of radiation due to scattering of plasma waves on relativistic ions are calculated in the same manner (Equations (4.14)–(4.15)). The total energy loss due to this radiation is given in Equations (4.23)–(4.25). The coefficients of induced emission are given in (4.26)–(4.28).The results are discussed in Section 5. It is shown that the loss of energy by nonlinear plasma radiation is much smaller than the ionization loss. However, the coefficients of synchrotron radiation of electrons and nonlinear radiation of ions under cosmic conditions may be comparable in the case of a weak magnetic field and fairly low frequencies (5.5)–(5.6). Usually the spectrum of nonlinear plasma radiation is steeper than in the case of synchroton radiation. Equation (5.10) gives the condition for nonlinear radiation to prevail over thermal radiation.Translated by D. F. Smith.  相似文献   

11.
The size of the region is found, using a method previously applied by Friedjung and Malakpur (1971) to Nova Delphini. The conclusion of Pottasch (1967), that the lines are formed in a circumstellar cloud is supported.  相似文献   

12.
The rotation characteristics of large-scale (global) magnetic fields (GMF) and their relation to the activity of local fields (LMF) are studied over a long time interval (1915–1996). The main results are as follows. The GMF rotation rates and LMF activity vary in anticorrelation. Both variations have similar periods (11 years and a quasi-secular period of about 55–60 years), but are shifted relative to each other by half an 11-year cycle. Therefore, (1) the GMF rotation rate increases at the minimum of the 11-year cycle of LMF activity. (2) The GMF rotation rate is faster in the less active hemisphere. (3) The GMF rotation period slows down at the maximum of the secular LMF activity (cycles 18 and 19).  相似文献   

13.
The photoelectric observations of the eclipsing binary XY Ceti presented by us (see Srivastava and Padalia, 1975) have been analysed by Okazaki (1978) and Ramellaet al. (1980). They presented different sets of elements from the same set of our observations. This necessitated us to obtain the elements of XY Ceti again employing recent method of determination of elements.The revised geometrical elements of the eclipsing binary XY Ceti have been obtained by the method of Fourier analysis of the light changes in the frequency-domain, which was developed by Kopal (1979). These have been compared with our earlier (Srivastava and Padalia, 1975) results obtained by employing Russell and Merrill's (1952) method. The revised absolute dimensions of XY Ceti have been obtained using the spectroscopic elements given by Popper (1971), and the newly derived geometrical elements. The Roche radii have been derived to discuss the evolution of the system. The secondary component lies reasonably near to the Main Sequence, while the primary component falls above it. The evolutionary discussion indicates that the system is a detached one.  相似文献   

14.
The present study investigates the energy and mass distributions of all (11 322) coronal mass ejections (CMEs), 1406 CMEs associated solely with flares (FL CMEs), and 325 CMEs associated solely with filament eruptions (FE CMEs), all of which were observed by the Large Angle and Spectrometric Coronagraph on board the Solar and Heliospheric Observatory (SOHO/LASCO) from January 1996 to December 2009. The results show the following. i) The mean energy of FL CMEs is significantly lower than that of all CMEs. The mean energy of FE CMEs is significantly higher than those of FL CMEs and all CMEs. ii) The mean mass of FL CMEs is slightly larger than that of all CMEs. The mean mass of FE CMEs is significantly larger than those of FL CMEs and all CMEs. Our results suggest that CMEs should shed excess helicity stored in the corona and that the magnetic complexity determines the likelihood of CMEs.  相似文献   

15.
The region planned for performing the Luna-Glob mission is located in the southern part of the swell surrounding the largest South Pole-Aitken (SPA) basin. The photogeological analysis of the surface topography of this region using the LRO-WAC (resolution of 100 Mpxl) photomaps made it possible to define the following groups of morphological units (area types): (1) related to the formation of relatively fresh impact craters; (2) associated with larger (>100 km across) degraded craters including (2a) external and (2b) inner facies; and (3) occupying intercrater spaces. The comparison of the geological map with the map illustrating the distribution of the epithermal neutron flow (Mitrofanov et al., 2012) shows no correlation between them. Consequently, one should not expect development of rock complexes, which would be characterized by elevated concentrations of water in the region chosen for the Luna-Glob mission and, thus, considered among the first-priority targets. The comparison of the neutron flow distribution with the map of circular polarization of the Mini-RF radar beam also shows no correlation. This means that high values of circular polarization reflect elevated concentrations of rock fragments rather than water accumulations. Even though ice fragments are present, their sizes should only slightly be less as compared with the radar wavelength (12.6 cm). The region planned for investigations in the scope of the Luna-Glob mission corresponds to the swell of the largest (and, likely, oldest) preserved basin and offers a potential opportunity to analyze ancient material of this planet and introduce important constraints into the spectrum of models proposed for explaining the Moon’s origin.  相似文献   

16.
The hierarchical substructure of the core of the Perseus cluster of galaxies (A426, A262, A347, N507, and N383) is investigated using the method of S-tree diagrams. In the main system M (100 galaxies), two substructures AM (35 galaxies) and BM (13 galaxies) are determined. The group AM can be identified with the cluster A262 and the group N507; BM can be identified with the group N383; A426 and A347 are in the main system. The axis of symmetry of the system M passes through the Seyfert galaxy N1275 and is parallel to the axis of symmetry of the group AM, which is the core of increased density of the cluster of galaxies. Radial segregation of galaxies by morphological types is observed in the systems M and AM. The distribution of galaxies by position angles is uniform. Translated from Astrofizika, Vol. 41, No. 1, pp. 65–72, January-March, 1998.  相似文献   

17.
The UBV photometric observations of RT Per, from Sanwal and Chaubey (1981), were analyzed by the Wilson and Devinney code (1971). The light curves include reflection effects that for the first time has been suggested by Dugan (1911). RT Per has a semi-detached configuration where the lower-mass component is in contact with its respective Roche surface. The higher-mass component very nearly fills its Roche lobe. It has the characteristic of an Algol type system. The absolute dimensions for the primary and secondary of this system were calculated from its spectral types and by combining the photometric solution with inferred component radial velocities (Lu, 1990).  相似文献   

18.
During the last 40 years, the Crimean Astrophysical Observatory and five other observatories around the world have carried out more than 18 500 (daily) measurements of the mean magnetic field (MMF) of the Sun as a star. The main MMF periodicity is due to the equatorial rotation of the Sun with a synodic period of 26.92 ± 0.02 day (it was stable for decades, but “bifurcated” in the 23rd cycle). It is shown that (a) the average sidereal period of the equator, 25.122 ± 0.010 day, is in close resonant relations with orbital and axial rotations of Mercury (5: 2 and 5: 3, respectively); (b) the most powerful long period, 1.036 ± 0.007 years, is suspiciously close to the orbital period of the Earth and (c) coincides with the average synodic period of revolution of giant planets 1.036 ± 0.020 years; and (d) MMF reveals a significant period of 1.58 ± 0.02 years, which agrees, within errors, with the synodic period of Venus (1.60 years), and (e) a significant periodicity of 19.8 ± 2.5 years probably related to the 22-year magnetic cycle of the Sun. The nature of all these periodicities is mysterious.The assumption is made that the resonances originated at the early stages of formation of the Solar System, and their existence in the modern epoch is due to the specific features of the structure and dynamics of the central core of our star. It is found that the MMF level averaged over 40 years is practically zero, ?0.018 ± 0.015 G. The anomalous behavior of the 23rd cycle is pointed out; this is expressed in (1) violation of the Gnevyshev-Ohl rule for the pair of cycles 22–23, (2) accelerated rotation of the solar equator by 1.2%, and (3) considerable increase in the cycle duration (not smaller than 11.5 years), as compared to the average cycle duration in the 20th century (11.5 years). The problem of the so called magnetic “monopole” of the Sun is briefly discussed.  相似文献   

19.
The average atmospheric transmission factor was calculated for Bahrain by using two methods. One of them is derived from using actual (measured) global radiation results i.e. Sambo's model and the other derived from using the actual direct radiation (i.e., Chauliaguet's model). The average atmospheric transmittance was found to be (0.48 ± 0.28) in using the former method and (0.76 ± 0.0007) in the latter one. The relation between the atmospheric transmittance and some meteorological parameters is discussed and studied.  相似文献   

20.
《Icarus》1986,67(3):391-408
The evolution of the giant planets is calculated under the general hypothesis that the solid cores formed first, by accretion of small particles, and that these cores later gravitationally attracted their gaseous envelopes from the solar nebula. The evolution passes through the following phases. (1) Planetesimals accrete to form a core of rocky and icy material. (2) When the core mass has grown to a few tenths of an Earth mass, a gaseous envelope in hydrostatic equilibrium begins to form around the core. (3) The core and envelope continue to grow until the “critical” core mass is reached, beyond which point the envelope increases in mass much more rapidly than the core. (4) The envelope mass increases quickly to its present value and prodices a relatively high luminosity, derived from gravitational contraction. (5) Accretion of both core and envelope terminates, and the planet contracts and cools to its present state on a time scale of 5 × 109 years. Evolutionary calculations of phases (2) through (5) are presented, based on solutions of the time-dependent stellar structure equations in spherical symmetry. The physical considerations that determine the critical core mass are discussed; its value is found to depend strongly on the core accretion rate but only weakly on surface boundary conditions. Evolutionary tracks up to the present state are presented for objects of Uranus and Saturn mass.  相似文献   

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