共查询到20条相似文献，搜索用时 15 毫秒
1.
S. Yu. Gorda 《Astrophysical Bulletin》2016,71(1):64-74
The results of quasi-simultaneous spectroscopic and photometric observations of a W UMatype eclipsing variable star AM Leo are presented. The observations were carried out with a 1.2-m telescope equipped with a high-resolution echelle spectrometer, and a telescope-reflector (D = 0.45m) of the Kourovka Astronomical Observatory of Ural Federal University. New values of semi-amplitudes of the radial velocity curves of the components, K1 = 109.6kms?1 and K2 = 252.4kms?1 and the systemic radial velocity V0 =-9.3 kms?1 are obtained, comparable to the data published in the literature. The semi-amplitude of the radial velocity curve of a more massive component K1 and the mass ratio of the components q = 0.412 appeared to be slightly smaller than the values obtained by other authors. An assumption wasmade that a possible reason of this is the presence of hot and/or cold spots on the surface of the components, shifting the effective center of brightness of the visible disk of the component with respect to its center of mass position. It was shown that the AM Leo light curve variations on the time scales of one and more days, registered within the photometric part of the study may be described by the choice of appropriate model of the spot structure. 相似文献
2.
A. H. Gabriel 《Solar physics》1971,21(2):392-400
As a result of a collaborative rocket experiment carried out during the solar eclipse on 7 March, 1970, measurements have been made of the brightness of Lyman from the corona, at heights between 5 × 104 and 5 × 105 km above the limb. The emission is shown to occur primarily through the resonance scattering of chromospheric Lyman from the residual neutral hydrogen in the corona. Both the absolute value and radial fall-off of the brightness agree well with calculations based on solar density models. The Lyman emission has similar variations around the limb to the white light corona, showing in particular an equatorial enhancement. 相似文献
3.
The brightness of the solar corona due to Thomson scattering depends linearly on the electron density, while the brightness due to the Balmer continuum is proportional to its square. As a consequence, information on the distribution of the electron density in the corona can be obtained by comparing the radial profiles of the surface brightness in both continua. This idea was explored for the first time in the solar eclipse of November 03, 1994, in Foz do Iguaçu, PR, Brazil. Pictures of the corona were obtained with interference filters, one centered at 477 nm (Thomson continuum) and another one at 347 nm (Balmer continuum). The second filter also transmits the Thomson continuum through its spectral window, so that the Balmer images contain Thomson contamination. This paper reports on the observational results and presents their preliminary analysis. It was found that in certain radial directions, the normalized profiles of both continua (Thomson and contaminated Balmer) coincide, but in other directions they differ significantly. The non-coincident profiles may only occur if Balmer emission becomes important in relation to the Thomson scattering. A simple calculation shows that in such cases the electron density in the inner corona must exceed the values of standard models by up to 6.1 × 104 times, maintaining however the total number of electrons along the line of sight in agreement with the prediction of standard models. It is concluded that the corona contains high electron concentration in cloudlets of subtelescopic sizes down to 106 cm. The varied behavior of the radial profiles of both continua in different radial directions, suggests that the subtelescopic structures might be related to the spatially variable topology of coronal magnetic flux tubes. 相似文献
4.
J. P. Mehltretter 《Solar physics》1971,16(2):253-271
Continuum brightness and Doppler velocity fluctuations in the lines 6301.5 and 6302.5 Å of Fei, measured in two selected spectrograms, are analysed by standard statistical (power- and coherence spectrum) methods. It is shown qualitatively that the oscillatory component of the velocity fluctuations (at spatial wavelengths > 4) decreases, while the supposedly granular component (at spatial wavelengths < 4) as well as the coherence between brightness and velocity fluctuations increases with optical depth.The spatial resolution of the spectrograms is estimated by comparing the observed power spectrum of brightness fluctuations with spectra found in the literature, assuming the combined instrumental and seeing spread function to be Gaussian. The resolution thus determined is = 1.24 ± 0.07. If the measured values are corrected accordingly, we obtain a true brightness rms of 10 to 14%, depending upon the shape of the power spectrum chosen for comparison, and a velocity rms at continuum optical depth of 1.3 km/sec. It is shown, however, that using the same correction function for the velocity power spectrum as for the brightness possibly gives rise to misestimating the velocity rms.Mitteilungen aus dem Fraunhofer Institut Nr. 100. 相似文献
5.
6.
I. H. Urch 《Solar physics》1969,10(1):219-228
A steady state, inviscid, single fluid model of the solar win d in the equatorial plane is developed using magneto-hydrodynamics and including the heat equation wit h thermal conduction but no non-thermal heating (i.e. a conduction model). The effects of solar rotation and magnetic field are included enabling both radial and azimuthal components of the velocity and magnetic fields to be found in a conduction model for the first time.The magnetic field cuts off the thermal conduction far from the sun and leads to an increased temperature at 1 AU and relatively small changes to the radial velocity and density. Models have been found which fit the experimental electron densities in 2 R
< r < 16 R
. These models predict at 1 AU a radial velocity of 300–380 km·sec-1 and a density of 8 protons·cm-3. The latter velocity corresponds to a density profile obtained by Blackwell and Petford (1966) during the last sunspot minimum, and is about 100 km·sec-1 above that found in previous conduction models which fit the coronal electron densities. The radial velocities are now consistent with the mean quiet solar wind, as are the densities when the experimental values are averaged over a magnetic sector. However, the azimuthal velocity at 1 AU is only 1–2 km·sec-1 which is low compared to the experimental values, as found by previous authors. 相似文献
7.
We have made high resolution observations of HCN (1-0) emission from the carbon star Y Canum Venaticorum using the Nobeyama Millimeter Array. We find that the emission region is not well resolved by the synthesized beam of 3.7 × 4.6 over the entire velocity range (VLSR =10 to 35 km s–1). We find that the true brightness temperature probably exceeds 200 K at many velocity channels as well as at the 26 km s–1 maser spike. The broad emission component may be the result of superimposed maser spikes. The high brightness requires an unreasonably high HCN fractional abundance if LTE is assumed. It is likely that the HCN abundance previously reported for the star is considerably affected by the maser action. A new maser spike has been found at VLSR = 29 km s–1 相似文献
8.
The Advanced Technology Solar Telescope site survey Sky Brightness Monitor simultaneously images the solar disk and the sky to about 8 solar radii in four wavelengths at 450, 530, 890 and 940 nm. One day of data from Mees Solar Observatory on Haleakala and from the National Solar Observatory at Sacramento Peak (Sunspot, New Mexico) are analyzed. Both sites show strong Rayleigh extinction, but while Haleakala shows a larger aerosol component, Sunspot shows a large variation in the aerosol component. Overall the Haleakala extinction varies as –2 whereas the Sunspot extinction changes from about –3.5 to about –2, suggesting an increasing aerosol component during the day. Water vapor absorption measurements from both sites are similar, though Sunspot shows larger time variations than Haleakala. The instrument-corrected sky brightness from both sites show comparable values, and again the Sunspot data show more variations. The sky brightness values show a radial dependence of sky brightness of r
–0.1 at Haleakala, but a dependence of r
–1.0 at Sunspot. The wavelength variation of the sky brightness at Haleakala is relatively constant at –1.5 but varies at Sunspot from –1.5 to –0.1 again suggesting an increasing aerosol contribution during the day at Sunspot. Finally, dust measurements near the ground are compared with the extinction wavelength exponent for data taken at Haleakala on 24 Feb. 2003. The measurements suggest more large dust particles are present near the ground than averaged over the whole air column. 相似文献
9.
M. P. Nakada 《Solar physics》1979,62(2):343-346
An attempt is made to specify coronal hole boundaries in the brightness of 284 of Fe xv. This is done by evaluating brightnesses of 284 at boundaries selected by various groups. These results are in quite good agreement and suggest a brightness value of (0.8±0.4)×1012 photons cm–2 s–1 sr–1 for coronal hole boundaries in 284. The examination of a number of isophote maps near this boundary brightness shows no consistent brightness gradient. 相似文献
10.
We present and discuss the results of our long-term JHKLM photometry for two RV Tau stars (R Sge and RV Tau) and the yellow supergiant V1027 Cyg, a candidate for protoplanetary nebulae. The amplitude of the infrared brightness variations in R Sge and RV Tau over fourteen years of observations was 0 . m 9?1 m ; the infrared brightness variations in V1027 Cyg over eighteen years did not exceed 0 . m 25. The infrared brightness and color of R Sge fluctuated about their gradually changing mean values; the infrared brightness variations agree with a period of 70.77 days. The periodic J brightness and J-H color variations in R Sge can be explained by temperature pulsations with ΔT ≤ 200 K and radial pulsations with [ΔR/R] ≤ 0.2. From 1995 to 2008, the mean J brightness of RV Tau increased, while its mean J-H color index decreased; the variations in the mean J brightness can be associated mainly with stellar temperature variations; a periodic component with P = 78.73 days is observed in the infrared brightness and color fluctuations. The variations in the mean J brightness and J-H color index of the supergiant V1027 Cyg over eighteen years of observations did not exceed a few hundredths of a magnitude; both temperature and radial pulsations may be present in the observed J brightness variations. The most probable period of the infrared brightness fluctuations in V1027 Cyg is 237 ± 2 days. The dust shell of R Sge may consist of two layers with grain temperatures of ～1000 and ～700 K; the optical depth at 1.25 µm is ～0.02 and ～0.24, respectively. The grain temperatures in the circumstellar dust shells of the supergiants RV Tau and V1027 Cyg are ～600 K (RV Tau) and ～700 K (V1027 Cyg). Their optical depths at 1.25 µm are ～0.24 (RV Tau) and ～0.008 (V1027 Cyg). 相似文献
11.
Mahipal Singh 《Astrophysics and Space Science》1982,87(1-2):269-277
The H profile in the spectrum of Orionis shows phase-dependent changes, with a period of variation equal to the orbital period fo the binary system. The profile shape changes from a normal absorption profile at zero phase to a P Cygni-type at a later phase, to an absorption profile having emission at the centre of the profile, to a normal absorption profile at the end of the period. The spectra have been obtained at the Cassegrain focus of Kavalur Observatory telescopes (50 and 100 cm) at 17.2 Å mm–1 reciprocal dispersion and resolution 0.3 Å at 6562.817 Å. Assuming that the P Cygni profile is formed by a spherically-symmetrical region, the analysis gives a shell radius of 2.18 stellar radius and an electron density in the shell equal to 6.54×10–9 cm–3, with the observed expansion velocity of 50 km/s–1, a mass loss of 1.3×10–7
M
per year.An analysis has been carried on the radial velocity data of earlier observers and the present radial velocity data. It is found that the orbital elements change. The presence of apsidal motion is confirmed by the increasing value of . The radial velocity of the centre of mass, , shows periodic variation. These observations confirm the presence of a third body. The values ofK (mean amplitude),P (period),a sini, and mass functionf(m), indicate a regular decrease, thereby confirming the mass transfer/mass loss from the system. 相似文献
12.
J. Roosen 《Solar physics》1969,7(3):448-462
The quiet component of the 9.1-cm solar radio emission is studied from the Stanford radioheliograms covering the period April–October 1964. The distribution of the brightness temperature in heliographic coordinates is not entirely uniform, but positive and negative departures from the average value appear at a number of stable locations. The most important negative departure crosses the central meridian 4 days before the maximum of the recurrent geomagnetic activity. Two out of three less important brightness depressions are connected with geomagnetic disturbances in the same manner. It is suggested that the brightness depressions are identical with M-regions.The result is confirmed by the construction of polytrope models for the solar wind, for various values of the parameters (the polytrope index) and T (the temperature in the inner corona). The velocities near the earth's orbit and in the inner corona are computed as functions of the model parameters, the density results from the observed proton flux at 1 AU. For quiet conditions the model with T = 1.26 × 106 K and = 1.10 is appropriate. The corresponding density and temperature in the corona lead to a value of 4000 K for the contribution of the corona to the 9-cm brightness. For disturbed conditions the suitable model has the parameters T 2.0 × 106 K, a 1.04. It being given that the proton flux at 1 AU is relatively constant, the equation of continuity leads to a low coronal density because of the high solar-wind velocity. The corresponding coronal contribution to the 9-cm brightness is of the order of 10 K. This confirms that the brightness temperature is considerably reduced in the regions where the enhanced solar wind originates. We suggest the name coronal depression for such regions.Papers II and III will appear in forthcoming issues of this journal. 相似文献
13.
We determine the radial component of the supergranular flow velocity by examining the center-to-limb variation of the Doppler velocity signal. We acquire individual Doppler images obtained with the MDI instrument on the SOHO spacecraft and process them to remove the p-mode oscillation signal, the axisymmetric flows, the convective blueshift signal, and instrumental artifacts. The remaining Doppler signal contains only non-axisymmetric flow structures. The Doppler signal from the horizontal flows in these structures varies like sin, where is the heliocentric angle from disk center. The Doppler signal from radial flows varies like cos. We fit the center-to-limb variation of the mean squared velocity signal to a straight line in sin2 over the central portion of the disk. The intercept of this line at disk center gives the amplitude of the radial component of the flow. The slope of the line gives the amplitude of the horizontal component. We find that the radial flows for typical supergranules have speeds about 10% that of their associated horizontal flows or about 30 m s–1. The ratio of the radial to horizontal flow speed increases from 9% to about 18% as the size of the structure decreases from >60 Mm to 5 Mm. We use data simulations to check these results and find a ratio that increases from 5% to only about 12% over the same range of sizes. These smaller ratios are attributed to an underestimation of the horizontal flow speeds due to the fact that the transverse component of the horizontal flow is not detected by Doppler measurements. 相似文献
14.
B. F. Yudin 《Astrophysics and Space Science》1985,110(2):277-291
An analysis of the results of observations of the symbiotic star Z And has shown that no definite model can be derived at present on their basis. If the hot component is essentially an accreting white dwarf with a hydrogen-burning shell source, then the gas envelope must be optically thin for Lc-emission and itsT
e must be in the neighborhood of 2.6×104K. And if the hot component is a Main-Sequence star with an accretion disk around it, then it is classified with red dwarfs. The electron temperature of the gas envelope must be 1.5×104K. The luminosity of the hot component at the minimum of its visual brightness is only a few times lower than its Eddington limit. Therefore, as the accretion rate goes up, the initial increase in its brightness (U1
m
.5), unaccompanied by any perceptible changes in the spectrum of Z And, will be followed by disintegration of the regular disk and flare of the star in the visible range. In the same model, partial eclipses of the hot source must occur. They seem to be observable on the star's light curve in theU band. Substitution of a solar-type star for the first-named component in the binary red dwarf + red giant system will lead to a significant decrease in the excitation of the combination spectrum. 相似文献
15.
Simultaneous observations of radial velocities in a quiescent prominence seen in H on the disk and in the underlaying photosphere have been obtained in the Meudon Observatory: Doppler shifts in photospheric lines are weaker than in the surrounding regions (<0.3 km s-1); the scale of velocity structures is smaller (<104 km). The vertical component of velocities cannot be neglected. H Doppler shifts show that: (a) Highest velocities are often correlated with high brightness horizontal gradients, which suggests that filament and surrounding bright regions belong to the same geometrical and dynamical structure. (b) Fast motions (7 km s-1) have short life-times (a few minutes). (c) Slow motions in dark regions (<3 km s-1) are associated with blue shifts and may last several hours. This behaviour was confirmed in many other cases by filament observations with the 3-wavelength H patrol. This is consistent with EUV observations of the transition zone around prominences, but disagrees with downward motions as seen at the limb, unless these motions do not refer to material velocities. 相似文献
16.
A limb, two-ribbon H flare on June 4, 1991, associated with a white-light flare and followed by an emission spray and post-flare loops, is studied. A region of rapidly enhanced brightness at the bottom of the H ribbon above the white-light flare is revealed. The energy released by the white-light flare at eff = 4100 is estimated to be about 1.5 × 1028 erg s–1. 相似文献
17.
Massimo Fracassini Laura E. Pasinetti Livio Pastori 《Astrophysics and Space Science》1977,49(1):145-167
The results of qualitative analysis and radial velocity (RV) determinations from 1967 to 1976 are given. These analyses show sometimes the presence of a thin variable shell also in the years 1967–1974, before the appearance of the envelope. Intensity variations of the metallic lines seem to indicate that in the same period changes of temperature and/or electron pressure may occur in the photospheric layers. In the period 1975–76, the considerable range ofRV and the variability of the shell features show that the shell is rather active. Some conspicuousRV variations seem to be correlated to brightness changes. TheRV do not confirm the periods suggested by the photometric observations. A periodogram analysis givesRV curves with a poor evidence of periodicity. However, the periodP=1d.5845 obtained from this analysis, close to that of Schmidt, seems to confirm Schmidt's hypothesis of a contact binary system. The periodogram analysis of theRV during the years 1900–1976 and some physical arguments, suggest a probable photospheric activity or an invisible companion with the observed shell period of 30 yr. The duplicity, suggested by Kí and Harmanec (1975) for all the Be stars, could be yet questioned foro And.Thesis for the degree of Applied Physics. 相似文献
18.
A spectroscopic investigation of a quiescent prominence has been performed: the line profiles of the H and K lines have been carefully determined in all regions of the prominence where these emissions are likely to originate in optically thin layers. Therefore we have been able to study the electron temperature T
e and the microturbulent velocity in the outer parts of the prominence. We find that on the average, T
e = 5700 K (Figure 1) and = 6.7 km s-1 (Figure 2) which are in very good agreement with classical data. Figure 3 represents the radial velocity measurements and Figure 4 the ratio of the total intensity of H to K lines. Thus the prominence we have observed does not show for T
e and the regular increase outward which has been described by Hirayama (1971). On the other hand increases towards the Equator, in the dynamically active part of the prominence, which could indicate that represents the effect of macroturbulence rather than microturbulence (Kawaguchi, 1966). In this part of the prominence only the K line is in emission and the average value of the microturbulence is 9.4 km s-1, the radial velocity is also generally increasing. At last, according to the absolute intensities of the H and K lines, the electron density in the outer layers of the prominence is no more than 1 × 1010 cm-3. 相似文献
19.
The radial velocity measurements of the single line spectroscopic binary and Cephei star NU Centauri made during 1985, 1987, and 1988 are presented. New ephemeris with a pulsation period of 0d.1696401 has been derived by combining the three season data. The new ephemeris also fits well for the earlier data published in the literature. 相似文献
20.
Jan Trulsen 《Astrophysics and Space Science》1972,18(1):3-20
The dynamics of two dimensional jetstreams have been studied by following the evolution of simulation particle populations for different collision models. Collisions, independent of details of the collision model, rapidly lead to the establishment of a distribution of perihelion vectors of the form ~exp(–(P–)2), the characteristic time for this process being of the order of magnitude equal to the mean free collision time. Under appropriate conditions a radial focusing takes place. In terms of the varians of semi-major axis a focusing exceeding a factor 2 has been achieved. Necessary conditions for the existence of this radial focusing are a sufficient degree of inelasticity and the requirement that the dominant part of the velocity change in a typical collision is along the pre-collisional relative velocity vector. The properties of grazing collisions are especially important in this respect. 相似文献