共查询到20条相似文献，搜索用时 109 毫秒
1.
K. T. Alfriend 《Celestial Mechanics and Dynamical Astronomy》1971,4(1):60-77
The stability ofL
4 and the motion aboutL
4 in the restricted problem of three bodies is investigated when there is three-to-one commensurability between the long and short periods of motion, that is, when the mass ratio has the value =0.013516.... The two time scale method is used (1) to show thatL
4 is an unstable equilibrium point when =3, (2) to determine for what initial conditions periodic orbits occur when 3, (3) to determine the stability of the periodic orbits, and (4) to investigate the boundedness of the motions aboutL
4 when 3. 相似文献
2.
Synoptic photoelectric observations of the coronal Fexiv and Fex emission lines at 530.3 nm and 637.4 nm, respectively, are analyzed to study the rotational behavior of the solar corona as a function of latitude, height, time and temperature between 1976 (1983 for Fex) and 2001. An earlier similar analysis of the Fexiv data at 1.15 R
over only one 11-year solar activity cycle (Sime, Fisher, and Altrock, 1989, Astrophys. J.
336, 454) found suggestions of solar-cycle variations in the differential (latitude-dependent) rotation. These results are tested over the longer epoch now available. In addition, the new Fexiv 1.15 R
results are compared with those at 1.25 R
and with results from the Fex line. I find that for long-term averages, both ions show a weakly-differential rotation period that may peak near 80° latitude and then decrease to the poles. However, this high-latitude peak may be due to sensing low-latitude streamers at higher latitudes. There is an indication that the Fexiv rotation period may increase with height between 40° and 70° latitude. There is also some indication that Fex may be rotating slower than Fexiv in the mid-latitude range. This could indicate that structures with lower temperatures rotate at a slower rate. As found in the earlier study, there is very good evidence for solar-cycle-related variation in the rotation of Fexiv. At latitudes up to about 60°, the rotation varies from essentially rigid (latitude-independent) near solar minimum to differential in the rising phase of the cycle at both 1.15 R
and 1.25 R
. At latitudes above 60°, the rotation at 1.15 R
appears to be nearly rigid in the rising phase and strongly differential near solar minimum, almost exactly out of phase with the low-latitude variation. 相似文献
3.
A. M. I. Osman 《Astrophysics and Space Science》1985,116(2):299-311
Surface photometry of the UV continuum galaxy NGC 838 has been carried out in theB, V system using photographic plates obtained with the 74 Kottamia telescope, Egypt. Isophotes, luminosity profiles, integrated photographic magnitudes, effective diameters and other photometric parameters are derived.The photoelectrically calibrated total apparent magnitudes areB
T
=13.57 with maximum diameters 1.57×1.34 (at threshold
m
=27.7 mag.//) andV
T
=12.91 with maximum diameters 1.54×1.32 (at threshold
m
=27.7 mag./). The integrated colour index(B–V)
T
=0.66 and the effective surface brightness
e
(B=19.0 mag./) and
e
(V=19.7 mag./. The major axis is at position angle =85°±1°.The nucleus of NGC 838 is quite blue (integrated colour(B–V)=0.41 forr
*<0.1) compared to normal galaxies while the colour becomes redder from the nucleus outwards. The UV excess, H emission and radio continuum emission previously observed from this galaxy by other investigators may be attributed to a recent burst of star formation in the nucleus of the galaxy of duration slightly greater than 2×107 yr. 相似文献
4.
Suresh Chandra 《Astrophysics and Space Science》1986,123(1):205-208
The Oppenheimer-Penney theory to calculate the polarization of L lines from hydrogen-like ions, when the impact electrons are distributed such that their probability is more in the regions close to the magnetic field (f(cos
n
), is applied by Chandra and Joshi (1984). The work of Chandra and Joshi (1984) has been reinvestigated for the pitch-angle distributionf()sin
n
. The degrees of polarization are still found to be independent of the atomic number of a hydrogen-like ion. 相似文献
5.
6.
В. М. Чаругин 《Astrophysics and Space Science》1975,37(2):441-447
, . N/E, E
r, (E
r)=1. , (, ) . . 相似文献
7.
We use the Cerenkov line emission mechanism to give a new explanation of the observed intensity ratios, particularly the L/H ratio, of the emission lines of quasars. We give equations that restrict the choice of the parameter values. The parameters are the characteristic energy of the relativistic electrons, the number density of neutral hydrogen and its relative level populations. With reasonable choice of the parmaeters, we can obtain calculated L/H, H/H, P/H ratios in agreement with observed values. Our estimate for the gas density in the broad line region of quasars is 1015 cm–3, very different from previous estimates. Unlike previous theories, such a high density causes no difficulties with the Cerenkov line emission. 相似文献
8.
We have detected 1.1 mm continuum emission from 24 of 53 Herbig Ae/Be stars surveyed with the JCMT. Survival analysis shows that 1.1 mm luminosity is correlated with bolometric luminosity and with IRAS 25µm luminosity. For those stars that were also detected at 0.45 or 0.8 mm we find a typical flux dependence of the form S
#x03BD;
3, which is steeper than that of most classical T Tauri stars. 相似文献
9.
High-energy proton (E
p > 55 MeV) and electron (E
e > 50 keV) events were observed by University of Iowa experiments on the satellites Explorer 33 and 35. The solar X-ray (2–12 Å) flares associated with the energetic proton events were found to have in general higher peak fluxes, considerably longer decay times (t) and smaller rise to decay time ratios (r) than the X-ray flares associated with the electron events. The most common decay times and rise to decay time ratios are: 80 t 100 min, 0.1 r 0.2 for the proton X-ray flares and t 20 min, 0.3 r 0.7 for the electron ones. 相似文献
10.
, ii (2000–3000 Å) i . , i . i (. 2). i i i i + ( 7–10). ii (. 13). ii i i (, 2400 Å) (. 14 15). i i i , iu , i (. 1). i i ii i i . . 相似文献
11.
Vibrational transition probabilities, namely Franck—Condon factors and
-centroids have been evaluated by an approximate analytical method for the (A–X), (A–X), and (A–X) system of YO molecule. Morse potential energy curves forX
2+,A
22,A22, andA22, states of YO have been constructed using the latest spectroscopic data. The value of
-centroids for the band have been found to decrease linearly with the corresponding wavelengths. We show results for two new transitions of (A–X) and (A–X) and five new bands of (A–X) of YO in the umbral spectrum of the Sun. 相似文献
12.
Р. М. Мурадян 《Astrophysics and Space Science》1980,69(2):325-337
, J=(m/m
p)1+1/n
, n=2 , n=3 , . , . , , . - wc m
P, G c . -. 相似文献
13.
Roberto Viotti Giovanni Battista Baratta Anna Rosa Marenzi Marcello Ranieri 《Astrophysics and Space Science》1990,169(1-2):95-100
We give an overview of the Car phenomenon on the basis of ground and space observations. We discuss in particular the IRAS images. We conclude that Car, initially with a mass > 100M
, is presently an intermediate-type hypergiant withL=5×106
L
, in a rapid evolutionary stage. This phase started with a large increase of mass loss in mid-1800 followed by dust condensation and a large visual fading, at constant bolometric luminosity.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain. 相似文献
14.
A fifth list of point sources from the IRAS Point Source Catalog (PSC) that are optically identified with stars of late spectral types is given. The list contains data on 75 objects. 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 the wavelengths 12, 25, 60, and 100 m in the regions of +73° +80° and 03h30m 18h30m and of +80° +90° and 00h00m 20h00m. Of the 99 objects, which are given in the IRAS PSC as unidentified sources of infrared emission, 24 are associated with known stars in existing catalogs while 75 sources proved to be unknown in the optical range. The optical coordinates, their departures from the IR coordinates, the V stellar magnitudes, the color indices CI, and the preliminary spectral subtypes have been determined. The objects have optical magnitudes in the range of 6
m
.5-17
m
.2. Finder charts from the DSS are given for the 69 new objects. 相似文献
15.
, , , , . , . , () (), , , . — . 相似文献
16.
Jiann-Tsorng Horng 《Astrophysics and Space Science》1975,34(2):L1-L5
Cyclotron waves in the solar wind near 1 AU with frequencies well below the electron cyclotron frequency and wavelengths much larger than the electron cyclotron radius but less than the proton cyclotron radius are considered. The cyclotron radii are defined from parallel thermal velocity of electron component and proton component with respect to the interplanetary magnetic field. No LH cyclotron waves are found to propagate for
p
< 0, where
p
1 –T
p/T
p is the temperature anisotropy of the proton component with respect to the interplanetary magnetic field. The damping or growth of RH cyclotron waves is found to depend on the frequency range and the temperature anisotropy of the proton component. The RH cyclotron waves are damped in the frequency range
r
|
p
|
p
for
p
< 0, where
p
is the proton cyclotron frequency. RH cyclotron instabilities occur in the frequency range |
p
|
p
>
r
> |
p
|
p
/(1–
r
) for
p
< 0. The marginal state is at
r
=|
p
|
p
.Abstract presented at theInternational Symposium on Solar-Terrestrial, São Paulo, Brazil, 17–22 June, 1974 相似文献
17.
The location and the stability of the libration points in the restricted problem have been studied when small perturbation and are given to the Coriolis and the centrifugal forces respectively. It is seen that the pointsL
4 andL
5 form nearly equilateral triangles with the primaries and the pointsL
1,L
2,L
3 remain collinear. It is further observed that for the pointsL
4 andL
5, the range of stability increases or decreases depending upon whether the point (, ) lies in one or the other of the two parts in which the (, ) plane is divided by the line 36-19=0 and the stability of the collinear points is not influenced by the perturbations and they remain unstable. 相似文献
18.
One-armedglobal oscillations in a non-selfgravitating polytropic disk rotating around a star are investigated. The unperturbed disk is axisymmetric, geometrically thin, and extends infinitely in the radial direction keeping its thickness constant. Perturbations considered are inviscid and adiabatic. It is found that there are one-armed retrograde wave modes which are trapped in an inner region of the disk. The eignefrequency of the lowest order mode is given by K(r
s)(z
0/r
s)2, wherer
s is the radius of the central star,z
0 is the half-thickness of the disk, and K(r
s) is the Keplerian angular frequency at the surface of the star.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984. 相似文献
19.
Vassiliki Tsikoudi 《Astrophysics and Space Science》1990,170(1-2):69-73
IRAS has detected 70% of the 66 F, G, K nearby dwarf stars investigated here. The sample included chromospherically active as well as non-active dwarfs. The detected stars show emission at 12 and 25 m. Their 12 m luminosity is in the range 1–13×1030 erg s–1 and it is strongly correlated to the star's total luminosity (L
bol).There are indications that some of the stars possess IR emission in excess of that expected from a stellar photosphere.Paper presented at the 11th European Regional Astronomical Meeting of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain. 相似文献
20.
A comparison is made between the stability criteria of Hill and that of Laplace to determine the stability of outer planetary orbits encircling binary stars. The restricted, analytically determined results of Hill's method by Szebehely and co-workers and the general, numerically integrated results of Laplace's method by Graziani and Black are compared for varying values of the mass parameter =m
2/(m
1+m
2). For 00.15, the closest orbit (lower limit of radius) an outer planet in a binary system can have and still remain stable is determined by Hill's stability criterion. For >0.15, the critical radius is determined by Laplace's stability criterion. It appears that the Graziani-Black stability criterion describes the critical orbit within a few percent for all values of . 相似文献