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1.
Theoretical distributions of pulsar dispersion measures (times sinb II) are computed for various assumed pulsar spatial distributions above (and below) the galactic plane, assuming a distribution for the ionized gas. The statistics on the twelve high-latitude pulsars lead to the conclusion that the pulsar distribution inz is at least as broad as the distribution of the ionized gas. The value derived for the local mean interstellar electron density in the galactic plane is 0.12 cm–3 and is interpreted to be due to a uniform ionized intercloud medium.Interstellar absorption of radio waves at low frequencies and cosmic X-rays at low energies are considered with regard to irregularities in the distribution of ionized gas. It is shown that if the obervations are made with a wide angle receiver the effective absorption optical deph is –2/2 where is the mean value and is the dispersion in . This relation assumes is much larger than . Analysis of recent low-frequency radio measurements from a satellite-borne receiver, however, leads to the conclusion that effects of irregulatirities are large.  相似文献   

2.
The ninth list of objects from the BIG (Byurakan-IRAS Galaxies) sample is presented; 87 galaxies are identified with 60 point sources from the IRAS PSC catalog in the region +69° +73° and 03h50m 09h50m with an area of 117 deg2. Most of the identified galaxies are compact with bright bulges and faint peripheries. The identified objects include 7 Sy candidates, 8 interacting pairs (of which one is a merger candidate), and 6 LSB galaxies. The optical coordinates and their deviations from the IR coordinates, the V magnitudes, morphological types, angular dimensions, and position angles are given. The identified galaxies are of morphological types Sa-Sc and have optical stellar magnitudes in the range 15.5m-21.5m with angular sizes in the range 3-26. Finding charts from DSS2 are provided for these objects.  相似文献   

3.
. .  相似文献   

4.
The emission spectra and their time variations of gyro-synchrotron emission from an ensemble of energetic electrons are computed for some initial power-law distributions of the electron energies N()d= – with =2 or 4. The spectra and decay curves of the emission are compared with solar microwave bursts in order to separately estimate the magnetic field H and . From a limited number of observations, we have 3 and H 103 gauss for the microwave impulsive bursts, and 2 and H (500–1000) gauss for the microwave type-IV bursts.  相似文献   

5.
Brosius  J.W.  Thomas  R.J.  Davila  J.M.  Thompson  W.T. 《Solar physics》2000,193(1-2):117-129
We used slit spectra from the 18 November 1997 flight of Goddard Space Flight Center's Solar EUV Rocket Telescope and Spectrograph (SERTS-97) to measure relative wavelength shifts of coronal emission lines as a function of position across NOAA active region 8108. The shifts are measured relative to reference wavelengths derived from spectra of the region's nearby quiet surroundings (not necessarily at rest) because laboratory rest wavelengths for the coronal EUV lines have not been measured to sufficient accuracy for this work. An additional benefit to this approach is that any systematic uncertainties in the wavelength measurements are eliminated from the relative shifts by subtraction. We find statistically significant wavelength shifts between the spatially resolved active region slit spectra and the reference spectrum. For He ii 303.78 Å the maximum measured relative red shift corresponds to a Doppler velocity +13 km s–1, and the maximum relative blue shift corresponds to a Doppler velocity –3 km s–1. For Si x 347.40 Å, Si xi 303.32 Å, Fe xiv 334.17 Å, and Fe xvi 335.40 Å the corresponding maximum relative Doppler velocities are +19 and –14, +23 and –7, +10 and –10, and +13 and –5 km s–1, respectively. The active region appears to be divided into two different flow areas; hot coronal lines are predominantly red-shifted in the northern half and either blue-shifted or nearly un-shifted in the southern half. This may be evidence that material flows up from the southern part of the region, and down into the northern part. Qualitatively similar relative wavelength shifts and flow patterns are obtained with SOHO/CDS spectra.  相似文献   

6.
The relevant data for the known 147 pulsars are presented in graphical and tabular forms. Various data correlations are discussed, and a detailed analysis of pulsar dispersion measures and distances is given. The range of the electron densities in the diffuse interstellar medium is found to be 0.01 cm–3n e0.1 cm–3, and n e0.03 cm–3. The dispersion scale height for pulsars is found to be 5.9±0.7 pc cm–3 implying a linear scale height of 200 pc, which is much smaller than the electron scale height of our Galaxy.Astrophysics and Space Science Review Paper.  相似文献   

7.
i , i i , , . i . : (T e 0,5MeV) (T e 0,5 MeV) . - i 2.3 keV i , i : . i , , 2c/ pi . , . - .  相似文献   

8.
A list of objects of the BIG (Byurakan-IRAS galaxies) sample is given: 89 galaxies identified with 55 point sources from the IRAS Point Source Catalog. The identifications were based on the Digital Sky Survey (DSS), the First Byurakan Survey, blue and red maps of the Palomar Observatory Sky Survey, and infrared fluxes at wavelengths of 12, 25, 60, and 100 mm in the region of +61° +65° and 05h30m 18h 00m with an area of 340 deg2 (additional IR sources were identified). The optical coordinates of the identified galaxies, their departure from the IR coordinates, the V stellar magnitude, morphological type, angular size, and position angle were determined. The objects have optical magnitudes in the range of 12 m .5 - 21 m .5 and angular sizes in the range of 3 - 43. Finder charts for these objects from the DSS are given.  相似文献   

9.
The aim of this paper has been to study the neutral helium triplet emission lines identified in the spectrum of the envelope of Nova Delphini. By comparing the observed flux of the neutral helium lines with that calculated theoretically by Robbins, we find that the optical thickness in the center of the line 3889 is of the order of 21.50 for summer 1969. The optical thickness obtained by this method is here denoted tran(3889).On the other hand, we obtain the number of neutral helium atoms in the 23S state [N(23S)] by considering the equilibrium between the mechanisms that populate and depopulate this state. We then find that the depopulation by photoionization due to the radiation of Ly (Hi), transitions to the 21S, 21p and 23p states by electron collision, photoionization due to the continuum radiation of the central star, are 82.70%, 13.20%, 2.40%, 0.90% and 0.80% respectively. We find that the mechanism of the photoionization by Ly is the dominant mechanism of depopulation of 23S state. We calculated ( 3889) of the order of 82.37, fromN(23S), obtained in the preceding paragraph. The optical thickness obtained by this method is here denoted bal(3889).The difference between tran(3889) and bal(3889) is very large and it cannot be attributed to calculation errors. We have considered all the mechanisms that can depopulate the 23S state, so we then conclude that the difference between tran(3889) and bal(3889) is due to the heterogeneity of the envelope of the Nova, already found by us in our previous study of the profiles of the permitted and forbidden lines. Finally, we find from this study a filling factor of the order of 0.30.  相似文献   

10.
The Einstein Field Equations for homogeneous cosmologies are considered within the viscosity approximation. It is shown that some power laws T m (whereT is the temperature) for the cross-section lead to collisionless behavior near the initial singularity in a big bang model. Under some circumstances one may have two viscous phases, as the cosmic fluid passes from collisionless to collisional to collisionless again, while the universe expands.Research was sponsored in part by the Aerospace Research Laboratories, Office of Aerospace Research, United States Air Force, Contract F33615-68-C-1675.  相似文献   

11.
The velocity gradients of the contrastreaming electron beams observed in the Earth's magnetosphere can excite three types of ordinary mode instabilities, namely (i) B-resonance electron instability, (ii) ion cyclotron instability, and (iii) unmagnetized ion instability. The B-resonance electron instability occurs at small values of the shear parameter 10–4<S<10–3, whereS = [(1/e){dU o(x)}/(dx)] (U 0(x) and e being the streaming velocity of the electron beams and the electron cyclotron frequency, respectively). Near the equatorial plane of the bouncing electron beams region, this instability can generate electromagnetic waves having frequenciesf(0.045–0.2) Hz and wavelentghs (0.5–10)km, and the wave magnetic field is polarised in a radial direction. This instability can also occur in the plasma sheet region during the earthwards and tailwards plasma flows events and can generate waves, with wave magnetic field polarised along north-south direction, in the frequency rangef(0.007–0.02) Hz with (10–100)km nearR=–35R E . For 10–3<S<10–2, the ion cyclotron instability is excited and it can generate waves up to 5th harmonic or so of ion cyclotron frequency. ForS>10–2, the unmagnetized ion instability is excited which can generate electromagnetic waves having frequences from 5 to 50 Hz and typical wavelengths (0.5–6)km. The growth rates of all the three velocity shear driven instabilities are reduced in the presence of cold background plasma. The turbulence generated by these instabilities may give rise to enhanced effective electron-electron and electron-ion collisions and broaden the bouncing electron beams.  相似文献   

12.
The electro-optic deflector as an analyzer of circular polarization in the photoelectric magnetograph is described. The electro-optic deflector consists of an electro-optic crystal and a polarizing beamsplitter. The plane bifurcation of this beamsplitter coincides with the spectrograph dispersion direction. The beamsplitter bifurcates a spectral line in two components. The distance between them is 0. The photometer slit is situated between these components. Both components of Zeeman splitting fall on the photometer slit but the distance between them varies from 0 + 2 H to 0 – 2 H (where H is the Zeeman splitting) with the electric voltage frequency applied to the electro-optic crystal. The intensity variations at the photometer slit are proportional to 4 H .  相似文献   

13.
Observations of C100 and C125 atomic carbon recombination lines were made at the Algonquin Radio Observatory, towards the neutral interface separating theHii region DR21 (at RA=20h37m14s, Dec=+42°0900) from its associated molecular cloud. An analysis of the Cn observations in conjunction with a simple model of a neutral interface enabled the derivation of the following parameters: electron density of 300 cm–3, electron temperature of 30 K, microturbulent velocity of 2.3 km s–1, and depth of the neutral interface of 0.01 pc. A single,stimulated emission model is sufficient to reproduce the Cn observations in the wavelength range from 4.6 cm (C100) to 21 cm (C166). All the known Cn data do support a pressure equilibrium between the neutral interface and theHii region, after the usual allowance is made for carbon depletion on grains.  相似文献   

14.
The potential energy curves for the electronic ground states of astrophysically important YO, CrO, BN, ScO, SiO and AlO molecules are constructed techniques using the five-parameter Hulburt-Hirschfelder function. The estimated dissociation energies are 7.235±0.15, 4.337 ± 0.09, 3.917 ± 0.09, 6.899 ± 0.14, 8.181 ± 0.17 and 5.202 ± 0.11 eV for YO, CrO, BN, ScO, SiO and AlO, respectively. The estimated D0 values are in reasonably good agreement with literature values. The r-Centroids and Franck-Condon factors for the bands of B2 + – X2 + of YO, B5 –X5 > of CrO, A3 – X3 of BN, B2 + –X2 + of ScO, E1 + – X1 + of SiO and D2 + – X2 + and B2 + –X2 + of AlO molecules have been determined. The Franck-Condon factors are evaluated by the approximate analytical method of Jarmain and Fraser. The absence of the bands in these systems is explained.  相似文献   

15.
The radiation of ultrarelativistic particles is examined in a quasi-uniform magnetic field superimposed by a wide spectrum of magnetic, electric, and electron density inhomogeneities created in a turbulent plasma. The radiation spectrum from a particle of a given energy is shown to acquire a high-frequency power-law tail with the same spectral index as the index of small-scale turbulence. For a power-law spectrum of ultrarelativistic electrons, dN()/d ~ –, with a cut-off at some energy max, the radiation spectrum consists of a few power-law ranges; the radiation intensity may suffer jumps at frequencies which separate these ranges.In the high-frequency range the spectral index is determined by small-scale magnetic and electric fields. At intermediate frequencies the main contribution comes from the synchrotron radiation in a large-scale field; the radiation spectrum has an index =(–1)/2. The same index may be produced by large-scale Langmuir waves. At lower frequencies the radiation spectrum increases owing to the transition radiation caused by electron density fluctuations; in this case the spectral index is equal to +1–.The possibility of diagnostics of high-frequency cosmic plasma turbulence from radiation of high-energy particles is discussed. It is shown that the proposed theory may explain some features in the spectra of several cosmic objects.  相似文献   

16.
We have observed 10 solar bursts during the thermal phase using the Haystack radio telescope at 22 GHz. We show that these high frequency flux observations, when compared with soft X-ray band fluxes, give useful information about the temperature profile in the flare loops. The microwave and X-ray band fluxes provide determinations of the maximum loop temperature, the total emission measure, and the index of the differential emission measure (q(T)/T = cT–1). The special case of an isothermal loop ( = ) has been considered previously by Thomas et al. (1985), and we confirm their diagnostic calculations for the GOES X-ray bands, but find that the flare loops we observed departed significantly from the isothermal regime. Our results ( = 1–3.5) imply that, during the late phases of flares, condensation cooling ( 3.5) competes with radiative cooling ( 1.5). Further, our results appear to be in good agreement with previous deductions from XUV rocket spectra ( 2–3).  相似文献   

17.
The observed energy spectra in synchrotron sources are power laws,N (E)=KE –, with the distribution in peaked around 2.5. These are consistent with initially injected spectra with between 1 and 2, subsequently steepened by synchrotron losses. Contrary to the results of Kardashev (1962), it is shown that statistical acceleration when coupled with synchrotron losses lead naturally to the formation of flat stationary spectra with 1. These stationary spectra have bends near the energy at which synchrotron losses balance the energy gains by acceleration. Above this bend the spectrum tends to =2. The time evolution of an initial spectrum towards the stationary spectrum is investigated. It is suggested that the initially flat spectra with 1 to 1.5 observed in some variable sources result from an incomplete approach to the stationary spectrum, and that in sources with constant acceleration spectra with 2 are to be expected.  相似文献   

18.
Quasi simultaneous H and radio observations of LSI+61o303 during August-September 1993 are presented. The radio data show that during the studied epoch the outburst has peaked at radio phase 0.6, at level100 mJy. No significant variations in the H profile at phases 0.5 to 0.65 have been detected. A remarkable increase of the EW and FWHM of the H blue peak is observed at radio phase 0.23. Possible reasons are considered.  相似文献   

19.
A model of -bursts is considered that treats the flares of neutron stars as a result of convectiveoscillation instability associated with the stars having strong internal magnetic fields ( 1013 to 1014 G). In the context of this model only sufficiently old (104 to 107 yr), drastically cooled-down neutron stars may be sources of -bursts. The paper shows that major characteristics of a -burster in the Supernova N 49 remnant (energy release during burst up to 1044 erg, age 104 yr, burst-to-burst interval (I to 3)×106s; rotation period P=8 s) may be explained under the assumption that the mass of the neutron star is about 0.14M · while its mean magnetic field strength is 1.5×1014 G abd 1013 G within the star and on its surface, respectively. The observational tests of the model discussed conclude the paper.  相似文献   

20.
A sixth list of objects from the BIG (Byurakan—IRAS galaxies) sample is given: 87 galaxies identified with 60 point sources from the IRAS Point Source Catalog. The identifications were based on the Digital Sky Survey (DSS), the First Byurakan Survey, blue and red maps from the Palomar Observatory Sky Survey, and infrared fluxes at 12, 25, 60, and 100 µm in the region of +65° +69° and 9h15m 14h00m with an area of 111 deg2. We determined the optical coordinates of the identified galaxies, their departures from the IR coordinates, and their V magnitudes, morphological types, angular sizes, and position angles. The objects have optical magnitudes in the range of 12 m .5-21 m .5 and angular sizes in the range of 2-29. Finder charts from the DSS are given for these objects.  相似文献   

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