共查询到20条相似文献，搜索用时 46 毫秒
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A linear correlation between the ratio of the[CII( $^{\text{2}}$ P A linear correlation between the ratio of the[CII(
P
→
P
)] line intensity to the [
CO(J:1 →0)] line emission, I
/I
and the
equivalent width (EW) is found, over the range 2–71 ? in
EW, for a sample of 21late-Type= galaxies. The latter is comprised of an optically selected sample of 12 normal Virgo Cluster
spiral galaxies with [CII] detections obtained by us with ISOLWS, plus nine late-Type= galaxies with higher star formation
rates (SFRs), for which [CII] data and, especially,
EW data are available in the literature. As a result we infer I
/I
to be a reliable tracer of the current mass-normalized global SFR for non-starburst spiral galaxies. Moreover, the ratio
of the [CII] line to the total far-infrared (FIR) continuum intensity, I
/I
, is found to decrease from ∼0.5% to ∼0.1% with decreasing SFR which we propose is due to a `[CII]-quiet' component of I
from dust heated by the general interstellar radiation field (ISRF). The more `quiescent' galaxies in the sample have values
of I
/I
different from those observed in `compact' Galactic interstellar regions. Their [CII]-emission is interpreted to be dominated
by diffuse regions of the interstellar medium (ISM). For normal `star-forming' galaxies the diffuse component of the [CII]
emission is estimated to account for at least 50% of the total.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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We report the discovery of brightness variability in the IR-excess early F supergiant HD 331319, a candidate post-AGB star.
Over three years of systematic U BV observations, the star showed low-amplitude (up to
in V) quasi-periodic brightness variations on a time scale of ∼45 days. A preliminary analysis of our photometry indicates that
HD 331319 and other typical post-AGBF supergiants have a similar pattern of variability. A study of the extinction toward
HD 331319 leads us to conclude that the fraction of the circumstellar extinction is small for this star. We present low-resolution
spectroscopy for HD 331319 and discuss the spectral classification of post-AGB F supergiants using HD 331319, HD 161796, HD
187885, and HD 56126 as examples. 相似文献
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Stanisław P. Kasperczuk 《Celestial Mechanics and Dynamical Astronomy》2000,76(4):215-227
In a recent paper Ballersteros and Ragnisco (1998) have proposed a new method of constructing integrable Hamiltonian systems.
A new class of integrable systems may be devised using the following sequence:
, where A is a Lie algebra
is a Lie–Poisson structure on R
3, C is a Casimir for
is a reduced Poisson bracket and (A, ▵) is a bialgebra. We study the relation between a Lie-Poisson stucture Λ and a reduced Poisson bracket
, which is a key element in using the Lie algebra A to constructing this sequence. New examples of Lie algebras and their
related integrable Hamiltonian systems are given.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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V. P. Arkhipova V. G. Klochkova E. L. Chentsov V. F. Esipov N. P. Ikonnikova G. V. Komissarova 《Astronomy Letters》2006,32(10):661-670
We present the results of spectroscopic and photometric observations for the B star StHα62 with an IR excess, a post-AGB candidate identified with the IR source IRAS 07171+1823. High-resolution spectroscopy has allowed the λ4330–7340 Å spectrum of the star to be identified: it contains absorption lines of an early B star and emission lines of a gaseous shell. The residual line intensities have been measured. The heliocentric radial velocities measured from absorption lines of the star and emission lines of the shell are 〈V r 〉 = +45 ± 1 and +52 ± 1 km s?1, respectively. The line-of-sight velocities of gas-dust clouds determined from the interstellar Na I lines are 12 and 33 km s?1. The He I λ5876 Å line exhibits a P Cyg profile, which is indicative of an ongoing mass loss by the star. The expansion velocity of the outer shell estimated from forbidden lines is 12–13 km s?1. Quantitative classification gives the spectral type B0.51 for the star. The parameters of the gaseous shell have been determined: N e = 3.1 × 103 cm?3 and T e ～ 21 000 K. Over 4 years of its observations, the star showed rapid irregular light variations with the amplitudes ΔV = We present the results of spectroscopic and photometric observations for the B star StHα62 with an IR excess, a post-AGB candidate
identified with the IR source IRAS 07171+1823. High-resolution spectroscopy has allowed the λ4330–7340 ? spectrum of the star
to be identified: it contains absorption lines of an early B star and emission lines of a gaseous shell. The residual line
intensities have been measured. The heliocentric radial velocities measured from absorption lines of the star and emission
lines of the shell are 〈V
r
〉 = +45 ± 1 and +52 ± 1 km s−1, respectively. The line-of-sight velocities of gas-dust clouds determined from the interstellar Na I lines are 12 and 33
km s−1. The He I λ5876 ? line exhibits a P Cyg profile, which is indicative of an ongoing mass loss by the star. The expansion velocity
of the outer shell estimated from forbidden lines is 12–13 km s−1. Quantitative classification gives the spectral type B0.51 for the star. The parameters of the gaseous shell have been determined:
N
e
= 3.1 × 103 cm−3 and T
e
∼ 21 000 K. Over 4 years of its observations, the star showed rapid irregular light variations with the amplitudes ΔV =
, ΔB =
, and ΔU =
and no color-magnitude correlation. We estimate the total extinction for the star from our photometric observations as A
v
=
. Near-IR observations have revealed dust radiation with a temperature of ∼1300 K. We estimate the distance to StHα62 to be
r = 5.2 ± 1.2 kpc by assuming that the star is a low-mass (M = 0.55 ± 0.05 M
⊙) protoplanetary nebula.
Original Russian Text ? V.P. Arkhipova, V.G. Klochkova, E.L. Chentsov, V.F. Esipov, N.P. Ikonnikova, G.V. Komissarova, 2006,
published in Pis’ma v Astronomicheskiĭ Zhurnal, 2006, Vol. 32, No. 10, pp. 737–747. 相似文献
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A model is presented to explain the observed frequency distribution of flare energies, based on independent flaring at a number of distinct topological structures (separators) within active-region magnetic fields. The model is a modification and generalization of a recent model due to Craig (2001), and reconciles that model with the observed flare waiting-time distribution, and the observed absence of a flare waiting-time versus energy relationship. The basic assumptions of the model are that flares of energy E
2 occur at separators of length
, and that the frequency of flaring at a separator is defined by the Alfvén transit time of the structure. To reproduce the observed distribution of flare energies the model requires a probability distribution P(
)
–1 of separator lengths
within active regions. This prediction of the model is in principle testable. A theoretical origin for this distribution is also discussed. 相似文献
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We report new properties of solar magnetic fields in a quiet region as found from their magnetic power spectra. The power spectra of network and intranetwork fields (non-network fields) are separately calculated from a Big Bear magnetogram obtained with moderately high spatial resolution of 1.5 arc sec and a high sensitivity reaching 2 Mx cm-2. The effect of seeing on the power spectrum has been corrected using Fried's (1966) Modulation Transfer Function with the seeing parameter determined in our previous analysis of the magnetogram. As a result, it is found that the two-dimensional power spectra of network and non-network fields appear in a form: (
1)
-1 and (
1)
-3.5. Here
0 0.47 Mm-1 for network fields and
0 0.69 Mm-1 for non-network fields, the latter of which corresponds to the size of mesogranulation;
1 3.0 Mm-1 for both, which is about the size of a large granule. The network field spectrum below
0 appears nearly flat, whereas that of non-network fields instead decreases towards lower wave numbers as (
)
1.3. The turnover behavior of magnetic field spectra around
1 coincides with that found for the velocity power spectrum, which may justify the kinetic approach taken in previous theoretical studies of the solar magnetic power spectra. 相似文献
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Osman M. Kamel 《Earth, Moon, and Planets》1983,28(3):221-245
In this part we determine the value ofS
1,
and
in terms of the canonical variables of H. Poincaré. A complete solution of the auxiliary system of equations generated by the Hamiltonian
is presented. 相似文献
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E. R. Lancaster 《Celestial Mechanics and Dynamical Astronomy》1970,2(1):60-63
Approximation formulas are found for
and
, wherex(t) satisfies
,x(0)=x
0,x(1)=x
1. The results are applied to an example of two-body motion. 相似文献
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In this paper two sets of improved approximate expressions of emissivity
, absorptivity
, effective temperature Teff, and frequency of peak brightness _p of gyrosynchrotron radiation are presented respectively for the ranges from 5 to 10 and 10 to 100 of harmonic numbers s(= /_B). The expressions are designed for the range from 20° to 80° of viewing angle , and the range 2 to 7 of electron energy spectral index . They are expressed by a power-law function in which the indexes are fitted by polynomial expressions of . Their statistical errors are, respectively, 24% and 32% for
and
for
and 28% for
. Their accuracies are much better than those of linear fitting of the power-law index. 相似文献