首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 46 毫秒
1.
BUSS observations of the profiles of two well observed spectral lines in the ultraviolet spectrum of CMi (Procyon; F5 IV–V) are analysed with a Fourier transform method in order to determine values of various parameters of the velocity field of the upper photosphere. We find a microturbulent line-of-sight velocity componentL = 0.9 ± 0.4 km s–1, a macroturbulent velocity componentL M = 5.3 ± 0.2 km s–1, and a rotational velocity componentv R sini=10.0±1.2 km s–1. In these calculations a single-moded sinusoidal isotropic macroturbulent velocity function was assumed. The result appears to be sensitive to the assumed shape of the macroturbulence function: for an assumed Gaussian shape the observations can be described withv R sini=4 km s–1 andL M = 11.6 ± 2.7 km s–1. A comparison is made with other results and theoretical predictions.  相似文献   

2.
In the region of the formation of weak and medium-strong lines, the microturbulence increases with height (V ver=0.7–0.9 km s-1, V hor= 1.1–1.5 km s-1), the macroturbulence decreases (V ver=1.6–1.4 km s-1, V hor= 2.4–1.5 km s-1), and the total velocity field (vertical component) is depth-independent (1.7 km s-1). The empirical damping constants for Fe, Ti, Cr, Ni lines are equal 1.36, 1.76, 1.66, 1.66, respectively. The correlation length (the Kubo-Anderson process has been used) in the solar photosphere is 520–550 km.  相似文献   

3.
A search for neutral hydrogen in the velocity range –300>V>–1000 km s–1 has been made in the zone around the galactic nucleus. Observations of 100 points reveal no neutral hydrogen at such high velocities, with brightness temperatures exceeding 0.25 K in the latitude range |b|<1°, and 0.20 K for |b|1°.  相似文献   

4.
A substantial concentration of galaxies towardl ii =320°,b ii =+7°, with a mean radial velocity of 4000 km s–1, has earlier been nicknamed the Great Attractor — it is a nearby supercluster of galaxies. Here, an attempt is made to detect an excess Faraday rotation measure that could be attributed to the magnetic field and thermal gas in the space between the galaxies inside the Great Attractor supercluster. Only an upper limit to the rotation measure, of at most 8 rad m–2, could be placed on the Great Attractor supercluster, implying in turn an upper limit on the supercluster magnetic field, of at most 0.1 microgauss (ordered component only).  相似文献   

5.
Detailed surface photometry for the SB(s)a galaxy NGC 7771 has been carried out in the blue spectral band. Isophotes, luminosity profiles, and photometric parameters are obtained from photographs collected with the 74 inch telescope of Kottamia Observatory, Egypt. The total apparent magnitudem T =13.08 with maximum dimensions 3.6±0.5×2.7±0.5 (at threshold µ m = 27.38 mag s–2). The absolute magnitude isM T =–21.70 if the distance is =90.2 Mpc. The major axis is in position angle =69°.5±1° and the mean axis ratio of the outer regionsq=b/a=0.45 corresponds to an inclinationi=66°. The equivalent effective radiusr e * =0.29 and the effective surface brightness µ e = 22.30 mag s–2.The equivalent luminosity distribution has been decomposed into two main components, anr 1/4 spheroid and an exponential disk. The total apparent magnitudes of the spheroidal and disk components are 14.36 and 13.48, which correspond to contributions of 31 and 69% to the total blue luminosity, respectively.  相似文献   

6.
We measure the separation velocity of opposite poles from 24 new bipoles on the Sun. We find that the measured velocities range from about 0.2 to 1 km s–1. The fluxes of the bipoles range over more than two orders of magnitude, and the mean field strength and the sizes range over one order of magnitude. The measured separation velocity is not correlated with the flux and the mean field strength of the bipole. The separation velocity predicted by the present theory of magnetic buoyancy is between 7.4Ba –1/4 cot and 13 cot km s–1, where is the elevation angle of the flux tube at the photosphere (see Figure 9), B is the mean field strength, and a is the radius of the observed bipole. The rising velocity of the top of flux tubes predicted by the theory of magnetic buoyancy is between 3.7Ba –1/4 and 6.5 km s–1. The predicted separation velocity is about one order of magnitude higher than those measured, or else the flux tubes are almost vertical at the photosphere. There is no correlation between the measured separation velocity and the theoretical value, 7.4Ba –1/4. The predicted rising velocity is also higher than the vertical velocity near the line of inversion in emerging flux regions observed by other authors.  相似文献   

7.
Summary The status of the cosmic distance scale problem in early 1989 is reviewed. Internally consistent distances to Local Group galaxies are given in Tables 5 and 6. Within the Local Group the distance scale is found to be 11±5% smaller than that previously adopted by Sandage and Tammann. Distances to nearby galaxies are used as stepping stones to the Virgo cluster. The interpretation of the Tully-Fisher observations of Virgo spirals is found to be ambiguous because it is not yet clear which spirals are cluster members and which are background objects. Distance estimates of the Virgo cluster obtained by different techniques are listed in Table 11. The distance modulus of the Virgo cluster is found to be 31.5±0.2, corresponding to a distance of 20±2 Mpc. The elliptical galaxies in the core of the Virgo cluster haveV 0=1200±46 kms–1, which corresponds toV LG=1082±48 km s–1. With an infall velocity of 250±50 km s–1 this yields a cosmological redshiftV=1332±69 km s–1, from which a Hubble parameter H0=67±8 km s–1 Mpc–1 is obtained. Space Telescope observations of distant Cepheids, Tully-Fisher observations of spirals in the Hercules eluster, and interference filter observations of Virgo planetary nebulae in the light of [OIII], should soon result in a major improvement in the accuracy with which H0 is known.  相似文献   

8.
According to the tangential method the productAR 0 is determined with 145.7 km s–1 from measurements of the line profiles of the 21-cm line of the neutral hydrogen by Weaver and Williams (1973). The recent individual measurements of Oort's constantA and of the distanceR 0 of the Sun from the galactic centre yields 138.5 km s–1. The mean value 142.1 kms–1 leads toA=14.56 km s–1 kpc–1 andR 0=9.76 kpc. At the galactocentric distanceR nearR 0 the angular velocity is represented by (R)=25.84–2.98 (R–9.76)+0.075 (R–9.76)2. The mass of the Galaxy amounts to 1-92×1011 .

Herrn Kollegen Prof. Dr W. Gleisberg zum 70. Geburtstag am 26.12.1973 gewidmet.

Mitteilungen Serie A.  相似文献   

9.
Horizontal proper motions of penumbral structure and umbral dots have been measured from a 17-min-long time series of sunspot images by numerical techniques. In the penumbra, inflows are seen to occur predominantly in the inner region, with an average velocity of 290 m s–1. Penumbral outflows take place mostly in the outer part, where they reach velocities as high as 1.5 km s–1, with an average velocity of 500 m s–1. In the umbra, proper motions of 28 bright dots have been measured with an accuracy better than 50 m s–1. The mean velocity of the umbral dots is 210 m s–1. Most of the umbral dots display the well-known inward motion away from the peripheral umbra.  相似文献   

10.
Seismic data from the Apollo Passive Seismic Network stations are analyzed to determine the velocity structure and to infer the composition and physical properties of the lunar interior. Data from artificial impacts (S-IVB booster and LM ascent stage) cover a distance range of 70–1100 km. Travel times and amplitudes, as well as theoretical seismograms, are used to derive a velocity model for the outer 150 km of the Moon. TheP wave velocity model confirms our earlier report of a lunar crust in the eastern part of Oceanus Procellarum.The crust is about 60 km thick and may consist of two layers in the mare regions. Possible values for theP-wave velocity in the uppermost mantle are between 7.7 km s–1 and 9.0 km s–1. The 9 km s–1 velocity cannot extend below a depth of about 100 km and must decrease below this depth. The elastic properties of the deep interior as inferred from the seismograms of natural events (meteoroid impacts and moonquakes) occurring at great distance indicate that there is an increase in attenuation and a possible decrease of velocity at depths below about 1000 km. This verifies the high temperatures calculated for the deep lunar interior by thermal history models.Paper presented at the Lunar Science Institute Conference on Geophysical and Geochemical Exploration of the Moon and Planets, January 10–12, 1973.  相似文献   

11.
The 25-meter radio telescope of the Netherlands Foundation for Research in Astronomy in Dwingeloo has been engaged full-time during the past 5 years in a survey of galactic 21-cm emission from the entire sky accessible from the Netherlands. The new material provides coverage of the sky at -30° on a 0°.5 grid sampled with a 35 main beam, over a velocity range of 1000 km s–1 at 1 km s–1 resolution, to a limiting brightness-temperature sensitivity typically better than 0.07 K. The data have been corrected for stray radiation entering both the near and far sidelobes of the antenna.  相似文献   

12.
From high precision computer controlled tracings of bright Ca+-mottles we investigated differential rotation, meridional and random motions of these chromospheric fine structures. The equatorial angular velocity of the Ca+-mottles agrees well with that of sunspots (14°.50 per day, sidereal) and is 5 % higher than for the photosphere. The slowing down with increasing latitude is larger than for sunspots. Hence in higher latitudes Ca+-mottles rotate as fast as the photospheric plasma. A systematic meridional motion of about 0.1 km s–1 for latitudes around 10° was found. The Ca+-mottles show horizontal random motions due to the supergranular flow pattern with an rms velocity of about 0.15 km s–1. We finally investigated the correctness of the solar rotation elements i and derived by Carrington (1863).  相似文献   

13.
Photometry of HD 155638=V792 Her has been analyzed to determine the elements of this totally eclipsing RS CVn binary. The light variation outside eclipse was found to have a period of 27d.07±0d.07, which is slightly different from the 27d.5384±0d.0045 orbital period. Analysis of the eclipses was achieved by a modification of the Russell-Merrill technique. With the aid of radial velocity measures, absolute elements were obtained for the hot and cool stars, respectively;R h=2.58R ,R c=12.28R ,M h=1.40M ,M c=1.46M ,i=80o.61 and velocity semi-amplitudesK c=48.36 km s–1±0.79 km s–1, andK h=50.50 km s–1±0.33 km s–1. The apparent magnitudes areV h=9 m .73 andV c=8 m .48. The distance to HD 155638 was estimated to be 310 parsecs.  相似文献   

14.
Schleicher  H.  Balthasar  H.  Wöhl  H. 《Solar physics》2003,215(2):261-280
For the leading part of sunspot group NOAA 8323, which rapidly changed its complex structure, a time series of the line-of-sight (LOS) component of the velocity field was obtained. With a two-dimensional Fabry–Pérot spectrometer, the magnetically insensitive line Fei 557.6 nm was scanned. The inclination of the LOS (heliographic angle) to the vertical was =28.5°. The umbra of the observed spot was divided by a system of light bridges into several parts. The spatial and temporal velocity field also exhibits a considerable complexity: in one extended umbral area there is a downward flow of 1 km s–1 relative to other dark sub-umbrae. At the center-side penumbra, with a line-of-sight Evershed outflow of 1.5 km s–1, a persistent patch, somewhat darker than the average penumbra, has a LOS velocity of 1.3 km s–1 in opposite direction, probably a downflow. At the limb-side penumbra, a photosphere-like area is interspersed, interrupting the Evershed flow which resumes with typical strength beyond this feature towards the outer penumbral boundary. Most interesting is the behavior of the light bridges, which have a slight blue shift, interrupted by short events of strong blue or red shifts which – within the time resolution of 35 s – instantly affect a considerable part of a light bridge.  相似文献   

15.
Hari Om Vats 《Solar physics》1992,138(2):379-386
Characteristics of flare-associated high-speed solar plasma streams are investigated using measurements from space probes and Earth-orbiting spacecraft for the period 1964–1982. The maximum observed velocity (V m) of these streams range from 400 to 850 km s–1} with peak probability for 600 km s–1}. These remain for the period of 1–10 days with the peak occurrence 3 days. The difference between the pre-stream velocity (V 0) and the maximum velocity (V m) of any high-speed stream serves as the measure of its intensity. For about 60% of the flare associated streams, (V m-V 0) is well in excess of 200 km s–1} and in some cases becomes as large as 450 km s–1}. The yearly percentage occurrence, total duration and the product of mean (V m - V 0) with total duration of the high-speed streams during the year correlates well with solar activity, e.g., maximum during high solar activity period and minimum during low solar activity. The study suggests that presence of sunspots plays a significant role in the generation of flare associated high-speed solar streams.  相似文献   

16.
High-velocity resolution (V=0.07 km s–1) H12CO+ (J=1–0) and H13CO+ (J=1–0) observations have been carried out towards L1551 by use of the Metsähovi 14-m radio telescope. The observations reveal a bipolar H12CO+ outflow from the pre-Main-Sequence star IRS-5 which is centred on a flattened, 3 long H13CO+ cloud clump. This disk-like cloud structure has a velocity gradient ranging from 6.56 km s–1 in the SE to 7.06 km s–1 in the NW. It is noteworthy that the direction of the H12CO+ ion outflow is oriented E-W, and not along the NE-SW axis of the more extended CO outflow. In the disk area the H12CO+ spectra show to distinct velocity components. The right-hand H12CO+ velocity component agrees with the velocity of the H13CO+ disk. The left-hand H12CO+ component seems to belong to the outflow and the dense lobe material. The H12CO+ isovelocity contour map indicates that the dense lobe material is rotating (V rot 0.6 km s–1) in the same sense as the H13CO+ disk. This supports hydromagnetic outflow models.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   

17.
Observations of line-of-sight velocities of gases in magnetic fields in weak plages near disk centre confirm the systematic downward velocity of 0.5 km s–1, and show fluctuations about this mean by a rather uncertain 0.2 km s–1. Some of the fluctuations show a fairly regular period around 5.5 min.  相似文献   

18.
Large-scale morphological waves with wavelengths of order 30° and amplitude=1/8 exist in several long Hi filaments in a 540 square degrees of sky aroundl=230°,b=+40°. The extent of the longest filament is greater than 72°, the limit set by the boundaries of the area surveyed. TheHi gas appears to be controlled by magnetic fields and the motion within flux tubes, determined by analysis of velocity along the filament axes, shows the presence of wave patterns with amplitude 5 to 6 km s–1 on an angular scale similar to that seen in the spatial structure projected on the sky.  相似文献   

19.
Strong absorption satellite lines of CaI 6572 were found on spectrograms taken on three successive days just after the fourth contact of the 1971–72 eclipse of Zeta Aurigae. The radial velocities of the satellite lines are –88 km s–1, –74 km s–1, and –180 km–1, respectively, relative to the K-type primary star (K4 Ib). These absorptions should be due to a circumstellar cloud in which the column density of neutral calcium atoms is 1×1017 cm–2 and the turbulent velocities come to 20–50 km s–1. It is suggested that the cloud may be formed by the rocket-effect of the Lyman quanta of the B-type component (B6 V). We estimate the density in the cloud to be 2×1011 atoms cm–3 fors=10R K and 2×1010 atoms cm–3 fors=102 R K, wheres denotes the distance of the cloud from the K star andR K the K star's radius. The mass loss rate of the K-type component is also estimated to be about 10–7 M yr–1, assuming that the expansion of the K star occurs isotropically.  相似文献   

20.
R. Muller 《Solar physics》1976,48(1):101-102
It is confirmed that the penumbral bright grains are moving towards the sunspots umbra. At the umbra-penumbra boundary their horizontal velocity is about 0.5 km s–1 and their displacement is inclined downwards with an angle of 5° to 20°.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号