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1.
Radio noise observations at frequencies of 0·700 Mc and 2·200 Mc were made at altitudes between 3000 and 11,000 km from a Blue Scout Jr. high-altitude rocket probe on 30 July 1963. A steady background flux of (7·5−3+6) × 10−19 W m−2)(c/s)−1 at 0·700 Mc and (1·8+1.0−0.5 × 10−19 W m−2 (c/s)−1 at 2·200 Mc was observed. Assuming a galactic origin of the observed fluxes at both frequencies, the averaged sky brightnesses are b(0·700 Mc) = (6−3+5) × 10−20 W m−2 (c/s)−1 sr−1b(2·200 Mc) = (1.4+1.0−0.5 × 10−20 W m−2 (c/s)−1 sr−1 The observed brightness at 2·200 Mc is in reasonable agreement with the results of other observers. The apparent brightness at 0·700 Mc is, however, greater than was expected from previous observations. An alternative source of the 0·700 Mc flux in the terrestrial exosphere, as well as characteristics of several noise bursts observed during the flight, is briefly discussed.  相似文献   

2.
Using the 13.7 m millimeter-wave telescope at the Qinghai Station of Purple Mountain Observatory, we have made observations of 13CO, C18O, HCO+ and N2H+ molecular lines towards IRAS 02232+6138. As the excitation density of the probe molecule increases from 13CO to HCO+, the size of the cloud core associated with IRAS 02232+6138 decreases from 2.40 pc to 0.54 pc, and the virial mass of the cloud core decreases from 2.2 × 103M to 5.1 × 102M. A bipolar molecular outflow is found towards IRAS 02232+6138. Using the power function n(r) ∝ r− to fit the spatial density structure of the cloud core, we obtain the power-law index  = 2.3 − 1.2; and we find that, as the probed density increases, the power function becomes more flat. The abundance ratio of 13CO to C18O is 12.4 ± 6.9, comparable with the values 11.8 ± 5.9 for dark clouds and the values 9.0–15.6 for massive cores. The abundance of N2H+ molecules is 3.5 ± 2.5 × 10−10, consistent with the value 1.0 − 5.0 × 10−10 for dark cloud cores and the value 1.2 − 12.8 × 10−10 for massive cores. The abundance of HCO+ molecules is 0.9 ± 0.5 × 10−9, close to the value 1.6 − 2.4 × 10−9 for massive cores. An increase of HCO+ abundance in the outflow region was not found. Combining with the IRAS data, the luminosity-mass ratio of the cloud core is obtained in the range 37–163(L/M). Based on the IRAS luminosity, it is estimated that a main-sequence O7.5 star is probably embedded in the IRAS 02232+6138 cloud core.  相似文献   

3.
A numerical analysis of cyclotron instabilities is carried out by computing the dispersion relation for a three component cold plasma-beam system. Rates of growth and damping for various values of the stream density are calculated from the dispersion relation. The rates of growth and damping increase monotonically as the number density of the proton stream increases. It is found that the frequencies at the rates of maximum growth and the damping decrease slightly to lower frequencies and a sharp peak at these frequencies becomes blunt. The minimum e-folding times of an ion cyclotron wave for (a) σs = 10−4, σi = 10−2 and (b) σs = 10−1, σi = 10−2 are about 3·84 and 0·16 sec respectively in the vicinity of the equatorial plane at 6 Re, where σs and σi are the ratios of the beam density Ns and the helium ion (H6+) density Ni to the total positive ions in the plasma-beam system.  相似文献   

4.
N. Hiotelis   《New Astronomy》2002,7(8):531-539
We present density profiles, that are solutions of the spherical Jeans equation, derived under the following two assumptions: (i) the coarse grained phase-density follows a power-law of radius, ρ/σ3 ∝ r−, and (ii) the velocity anisotropy parameter is given by the relation βa(r)=β1+2β2 (r/r*)/[1+(r/r*)2] where β1, β2 are parameters and r* equals twice the virial radius, rvir, of the system. These assumptions are well motivated by the results of N-body simulations. Density profiles have increasing logarithmic slopes γ, defined by γ=−d ln ρ/d ln r. The values of γ at r=10−2.5rvir, a distance where the systems could be resolved by large N-body simulations, lie in the range 1.0–1.6. These inner values of γ increase for increasing β1 and for increasing concentration of the system. On the other hand, slopes at r=rvir lie in the range 2.42–3.82. A model density profile that fits well the results at radial distances between 10−3rvir and rvir and connects kinematic and structural characteristics of spherical systems is described.  相似文献   

5.
《Astroparticle Physics》2002,17(4):1083-475
Using data from the HEGRA air shower array, taken in the period from April 1998 to March 2000, upper limits on the ratio Iγ/ICR of the diffuse photon flux Iγ to the hadronic cosmic ray flux ICR are determined for the energy region 20–100 TeV. The analysis uses a gamma–hadron discrimination which is based on differences in the development of photon- and hadron-induced air showers after the shower maximum. A method which is sensitive only to the non-isotropic component of the diffuse photon flux yields an upper limit of Iγ/ICR (at 54 TeV) <2.0×10−3 (at the 90% confidence level) for a sky region near the inner galaxy (20°< galactic longitude <60° and |galactic latitude |<5°). A method which is sensitive to both the isotropic and the non-isotropic component yields global upper limits of Iγ/ICR (at 31 TeV) <1.2×10−2 and Iγ/ICR (at 53 TeV) <1.4×10−2 (at the 90% confidence level).  相似文献   

6.
On the basis of radial velocity and Hipparcos proper motion data, we have analyzed the galactic kinematics of classical Cepheids. Using the 3-D Ogorodnikov-Milne model we have determined the rotational velocity of the Galaxy to be V0 = 240.5 ± 10.2 km/s, on assuming a glactocentric distance of the Sun of R0 = 8.5 kpc. The results clearly indicate a contracting motion in the solar neighbourhood of (∂Vθ∂θ)/R = −2.60 ± 1.07 km s−1 kpc−1, along the direction of galactic rotation. Possible reason for this motion is discussed. The solar motion found here is S = 18.78 ± 0.86 km/s in the direction l = 54.4° ± 2.9° and b = +26.6° ± 2.6°.  相似文献   

7.
The odd zonal harmonics in the Earth's gravitational potential are determined by analysing the changes in the eccentricities of six satellites having orbital inclinations spaced as uniformly as possible between 28° and 96°. The most satisfactory representation of the potential is found to be in terms of four coefficients, and their values are, in the usual notation: 106J3 = −2.56, 106J5 = −0.15, 106J7 = −0.44, 106J9 = 0.12. The resulting potential is compared with that obtained by other authors. Three and five-coefficient solutions are also presented.  相似文献   

8.
We compute the big bang nucleosynthesis limit on the number of light neutrino degrees of freedom in a model-independent likelihood analysis based on the abundances of 4He and 7Li. We use the two-dimensional likelihood functions to simultaneously constrain the baryon-to-photon ratio and the number of light neutrinos for a range of 4He abundances Yp = 0.225–0.250, as well as a range in primordial 7Li abundances from (1.6 to 4.1) ×10−10. For (7Li/H)p = 1.6 × 10−10, as can be inferred from the 7Li data from Population II halo stars, the upper limit to Nν based on the current best estimate of the primordial 4He abundance of Yp = 0.238 is Nν < 4.3 and varies from Nν < 3.3 (at 95% C.L.) when Yp = 0.225 to Nν < 5.3 when Yp = 0.250. If 7Li is depleted in these stars the upper limit to Nν is relaxed. Taking (7Li/H)p = 4.1 × 10−10, the limit varies from Nν < 3.9 when Yp = 0.225 to Nν 6 when Yp = 0.250. We also consider the consequences on the upper limit to Nν if recent observations of deuterium in high-redshift quasar absorption-line systems are confirmed.  相似文献   

9.
Venera 9, 10 measurements of the nightside ionospheric profile and the night airglow were used for investigating ionosphere formation processes. The upper ionospheric layer may be formed by HeI 584 Å radiation; the lower layer by meteorite ionization. Upper limits on the electron energy flux, <4 × 108eV cm−2 s−1, the helium ion flux <107 cm−2 s−1, the nitric oxide mixing ratio, <1.5 × 10−4 and the atomic sulphur mixing ratio, <10−6, are deduced for ionospheric altitudes.  相似文献   

10.
We discuss the capability of ‘100 GeV’ class imaging atmospheric Cherenkov telescope (IACT) arrays as future powerful instruments of ground-based gamma-ray astronomy. It is assumed that the array is gathered from individually triggered quadrangular 4-IACT ‘cells’ with a linear size of about 100 m. The multi-cell concept allows coverage of large detection areas economically, and at the same time the effective exploitation of the stereoscopic approach of determination of the shower parameters using information obtained by several IACTs simultaneously. Determination of arrival directions of γ-ray primaries on an event-by-event basis with accuracy δθ ≤ 0.1° combined with high suppression efficiency (at both the hardware and software levels) of the background hadronic showers by a factor of ≈ 103, and large, up to 1 km2 collection areas, can provide minimum detectable energy fluxes of ≥ 100 GeV γ-rays from point sources down to 10−13 erg/cm2 s which is about 3 orders of magnitude lower than the current sensitivities achieved by the satellite-borne detectors at MeV and GeV energies. High sensitivities of multi-IACT arrays would partially compensate the limited efficiency of the technique for all-sky surveys, as well as allow study of moderately extended (≤ 1°) γ-ray sources. IACT arrays with minimum detectable fluence of ≥ 100 GeV γ-rays Sγ < 10−8 erg/cm2 are well suited for effective exploration of highly sporadic nonthermal phenomena from different classes of astrophysical objects on time-scales from ≤ 1 s to several minutes.  相似文献   

11.
Recent rocket observations of the N2 V-K (Vegard-Kaplan) system in the aurora have been reinterpreted using an atmospheric model based on mass spectrometer measurements in an aurora of similar intensity at the same time of year. In contrast to the original interpretation, we find that population by cascade from the C3Πu and B3Πg states in the A3Σu+v=0,1 levels, as calculated using recently measured electron excitation cross sections, accurately accounts for the observed relative emission rates (IV-K/12PG0.0). In addition there is no need to change the production rate of A 3 Σ u+ molecules relative to that of C3Πuv=0 as a function of altitude in order to fit the profile of the deactivation probability to the atmospheric model. Quenching of A 3 Σ u+ molecules at high altitudes is dominated by atomic oxygen. The rate constants for the v=0 and v=1 levels are 8 × 10−11 cm3 sec−1 and 1.7 × 10−10 cm3 sec−1 respectively, as determined using the model atmosphere mentioned above. Recent observations with a helium cooled mass spectrometer suggest that conventional mass spectrometer measurements tend to underestimate the atomic oxygen relative concentration. The rate coefficients may therefore be too large by as much as a factor of 3. Below 130 Km we find that it is possible to account for the deactivation in bright auroras by invoking large nitric oxide concentrations, similar to those recently observed mass spectrometrically and using a rate constant of 8 × 10−11 cm3 sec−1 for both the v=1 levels. This rate constant is very nearly the same as that measured in the laboratory (7 × 10−11 cm3 sec−1). Molecular oxygen appears not to play a significant role in deactivating the lower A 3 Σ u+ levels.  相似文献   

12.
If neutrinos have mass, we give reasons for a possible pattern of three (squaed) mass eigenvalues: m12 (2.8−5.8) (eV)2, m22 0.01 (eV)2, m32 (1.5−1) × 10−4 (eV)2. The flavor states νμ and νe are mixtures of the eigenstates with m2 and m3 with a significant mixing, corresponding to an effective mixing angle of about 0.45. The ντ is nearly the state with m1; the other two effective mixing angles are about an order of magnitude smaller than 0.45. There is a marked similarity to mixing in the quark sector.  相似文献   

13.
The MSX infrared dark cloud G79.2+0.38 has been observed over a 11′×′ region simultaneously in the J=1-0 rotational transition lines of the 12CO and its isotopic molecules 13CO and 18CO. The dense molecular cores defined by the C18O line are found to be associated with the two high-extinction patches shown in the MSX A-band image. The two dense cores have the column density N (H2) (5 – 12) × 1022 cm−2 and the mean number density n (3 ± 1) × 104 cm−3. Their sizes are 1.7 and 1.2 pc in 13CO(1-0) line, 1.2 and 0.6 pc in C18O(1-0) line, respectively. The masses of these cloud cores are estimated to be in the range from 2 × 102 to 2 × 103 M. The profile of radial mean density of the cloud core can be described by the exponential function ¯n(p) p−0.34±0.02. Compared with the cases of typical optical dark clouds, the abundances of the CO isotopic molecules 13CO and C18O in this MSX infrared dark cloud appear to be depleted by a factor of 4–11, but at present there is no evidence for any obvious variation of the relative abundance ratio X13/18 between 13CO and C18O with the column density.  相似文献   

14.
We present a quantitative analysis of CO thermal emissions discovered on the nightside of Titan by Baines et al. [2005. The atmospheres of Saturn and Titan in the near-infrared: First results of Cassini/VIMS. Earth, Moon, and Planets, 96, 119–147]. in Cassini/VIMS spectral imagery. We identify these emission features as the P and R branches of the 1-0 vibrational band of carbon monoxide (CO) near 4.65 μm. For CH3D, the prominent Q branch of the ν2 fundamental band of CH3D near 4.55 μm is apparent. CO2 emissions from the strong v3 vibrational band are virtually absent, indicating a CO2 abundance several orders of magnitude less than CO, in agreement with previous investigations. Analysis of CO emission spectra obtained over a variety of altitudes on Titan's nightside limb indicates that the stratospheric abundance of CO is 32±15 ppm, and together with other recent determinations, suggests a vertical distribution of CO nearly constant at this value from the surface throughout the troposphere to at least the stratopause near 300 km altitude. The corresponding total atmospheric content of CO in Titan is 2.9±1.5×1014 kg. Given the long lifetime of CO in the oxygen-poor Titan atmosphere (0.5–1.0 Gyr), we find a mean CO atmospheric production rate of 6±3×105 kg yr−1. Given the lack of primordial heavy noble gases observed by Huygens [Niemann et al., 2005. The abundances of constituents of Titan's atmosphere from the GCMS on the Huygens probe. Nature, 438, 779–784], the primary source of atmospheric CO is likely surface emissions. The implied CO/CH4 mixing ratio of near-surface material is 1.8±0.9×10−4, based on an average methane surface emission rate over the past 0.5 Gyr of 1.3×10−13 gm cm−2 s−1 as required to balance hydrocarbon haze production via methane photolysis [Wilson and Atreya, 2004. Current state of modeling the photochemistry of Titan's mutually dependent atmosphere and ionosphere. J. Geophys. Res. 109, E06002 Doi:10.1029/2003JE002181]. This low CO/CH4 ratio is much lower than expected for the sub-nebular formation region of Titan and supports the hypothesis [e.g., Atreya et al., 2005. Methane on Titan: photochemical-meteorological-hydrogeochemical cycle. Bull. Am. Astron. Soc. 37, 735] that the conversion of primordial CO and other carbon-bearing materials into CH4-enriched clathrate-hydrates occurs within the deep interior of Titan via the release of hydrogen through the serpentinization process followed by Fischer–Tropsch catalysis. The time-averaged predicted emission rate of methane-rich surface materials is 0.02 km3 yr−1, a value significantly lower than the rate of silicate lava production for the Earth and Venus, but nonetheless indicative of significant active geological processes reshaping the surface of Titan.  相似文献   

15.
《Astroparticle Physics》1995,3(4):311-320
We report data taken by the LVD Experiment during a live-time period of 11 556 h. We have measured the muon intensity at slant depths of standard rock from about 3000 hg/cm2 to about 20 000 hg/cm2. This is an exclusive study, namely our data include only events containing single muons. This interval of slant depth extends into the region where the dominant source of underground muons seen by LVD is the interaction of atmospheric neutrinos with the rock surrounding LVD. The interesting result is that this flux is independent of slant depth beyond a slant depth of about 14 000 hg/cm2 of standard rock. Due to the unique topology of the Gran Sasso Laboratory the muons beyond about 14 000 hg/cm2 of standard rock are at a zenithal angle near 90°. Hence we have, for this fixed angle, a muon flux which is independent of slant depth. This is direct evidence that this flux is due to atmospheric neutrinos interacting in the rock surrounding LVD. The value of this flux near 90° is (8.3 ± 2.6) × 10−13 cm−2 s−1 sr−1, which is the first reported measurement at a zenithal angle near 90° and for slant depths between 14 000 and 20 000 hg/cm2. Our data cover over five decades of vertical intensity, and can be fit with just three parameters over the full range of our experiment. This is the first time a single experiment reports the parameters of a fit made to the vertical intensity over such a large range of standard rock slant depth. The results are compared with a Monte Carlo simulation which has as one of the two free parameters γπκ, the power index of the differential energy spectrum of the pions and kaons in the atmosphere. This comparison yields a value of 2.75 ± 0.03 for γπκ, where the error includes the systematic uncertainties. Our data are compared to other measurements made in our slant depth interval. We also report the value of the muon flux in Gran Sasso at θ = 90° as a function of the azimuthal angle.  相似文献   

16.
The energy spectrum of cosmic rays with primary energies between 1014 eV and 1016 eV has been studied with the CASA-MIA air shower array. The measured differential energy spectrum is a power law (dj/dE ∝ E−y) with spectral indices γ of 2.66±0.02 below approximately 1015 eV and 3.00±0.05 above. A new method is used for measuring primary energy derived from ground-based data in a compositionally insensitive way. In contrast with some previous reports, the “knee” of the energy spectrum does not appear sharp, but rather a smooth transition over energies from 1015 eV to 3.0 × 1015 eV.  相似文献   

17.
AC Cnc is a nova-like, eclipsing binary of period 7h13m. I chose it for observation because its eclipses are rather symmetrical. A photometric solution gives inclination i = 74.5° ± 0.8°, mass of white dwarf M1 = 0.74 ± 0.07 M, mass of the late-type companion, M2 = 0.97 ± 0.8 M. Temperature of the accretion disk varies approximately as inverse half-power of the radial distance, the temperature at the edge of the disk is 7600 K. Rate of mass transfer from the late-type star to the white dwarf is 7(−9) M/yr. The distance of AC Cnc is 500 ± 100 pc.  相似文献   

18.
We calculate the event rates induced by a 51Cr νe source and by a 90Sr---90Y source in BOREXINO through elastic scattering on electrons, assuming a nonzero neutrino magnetic moment μν. We consider a source activity of about 2 MCi and estimate the solar ν (“source-off”) background for various oscillation scenarios. It is shown that values of μν as low as 0.5 × 10−10μB ( 0.2 × 10−10μB) can be proved with the 51Cr source (90Sr source) in about 100 days of data taking.  相似文献   

19.
We discuss the possibility of using pure CF4 to fill a 2000 m3 Time Projection Chamber in order to detect the solar neutrinos through the elastic scattering vee− → vee−, with the threshold of 100 keV on the kinetic energy of the recoiling electron. In a volume of 2000 m3 of CF4 at normal pressure and room temperature, which corresponds to a mass of 7.4 ton, we expect ~ 3300 of such events per year. The detector can give the spectrum of the low energy neutrinos from the Sun and it can identify solar neutrinos of different origin: pp, 7Be, and, eventually, 8B. We find that 14C is a possible severe source of background: it is necessary to have a ratio 14C/12C lower than 10−19 in order to be able to identify the pp neutrinos.  相似文献   

20.
Absolute values of the emission cross sections for five vibrational bands in the Meinel system of N2+,A2πu to X2Σg+, excited by electron impact are presented. From these, a value was obtained for the total excitation cross section of the A2πu state at 100 eV of 26·5 × 10−18 cm2. The results are compared with those of other workers and with theory. Collisional transfer of the excitation energy from the levels of the A2πu state was also observed with a transfer cross section of approximately 10−14 cm2.  相似文献   

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