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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.
The coherent 5-min photospheric pressure oscillations with spherical harmonic degrees in the range 100 <l< 1000 were directly imaged over the photosphere with the monochromatic solar telescope FPSS at Meudon Observatory. Movie films were obtained with images spatially filtered to select sizes of increasing wave numbers (or l). Areas with ephemeral concentrations of coherent waves evolve in shape and may move horizontally with velocities of several tenths of km s–1. When a large number of waves are interacting, the maximum vertical velocity V max of the pulsation reaches around 1000 m s–1, irrespective of the size. Extrapolation to the ideal case of a single isolated wave gives V max proportional to size. For the areas of the smallest scale measured (l = 1000), when about 100 waves are interacting, V max is found to be 260 + 25 m s–1 at an altitude of 210 km above the reference level 5000 = 1 and increases vertically with a scale height of 750 ± 400 km.  相似文献   

3.
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   

4.
We use 240 CCD spectra taken in 1998–2000 with the coude echelle spectrograph of the 2-m telescope of the National Academy of Sciences of Azerbaijan to study temporal radial velocity and line profile variations of the ion, HeI, and Hβ lines in the spectrumof the α Cyg supergiant. We demonstrate that these variations are caused by pulsation-type motions in the star’s atmosphere. Ion and HeI lines oscillate in the main fundamental mode with a period of about 12.0 ± 0.5 d and an amplitude of 5.0 ± 0.5 km/s. These ion-line oscillations continue for about 35 days. Then the difference between the radial velocities of strong and weak ion lines results in a gradual decay of oscillations over a time interval of about 5.0 ± 1.0 d . Thereafter the process repeats itself. For the Hβ line we found two significant periods, two amplitudes, and three characteristic radial velocity variability behaviors for the blue and red halves of the absorption profile: with equal variability parameters (period P and amplitude A); with equal P and A, but with a phase shift between the radial velocity variations of the blue and red halves of the absorption profile; with different P and A for the two halves of the absorption profile. The star’s center of mass radial velocity as inferred from the γ-velocity is −4.5 ± 0.5 km/s. The average expansion velocity of the atmospheric layers, where the Hβ line forms, amounts to about −16.5 ± 0.5 km/s and varies temporally with an amplitude of about 3.0 km/s.  相似文献   

5.
Kobanov  N.I.  Makarchik  D.V.  Sklyar  A.A. 《Solar physics》2003,217(1):53-67
In this paper we carry out an analysis of the spatial–temporal line-of-sight velocity variations measured in the chromospheric (H, H) and photospheric (Fei 6569 Å, Fei 4864 Å, Nii 4857 Å) lines at the base of 17 coronal holes. Time series of a duration from 43 to 120 min were recorded with the CCD line-array and the CCD matrix. Rather frequently we observed quasi-stationary upward flows with a measured velocity of up to 1 km s–1 in the photosphere and up to 4–5 km s–1 in the chromosphere (equivalent radial velocity of up to 3 km s–1 and up to 12–15 km s–1 accordingly) near dark points on the chromospheric network boundary inside polar CH. Line-of-sight velocity fluctuation spectra contain meaningful maxima in the low-frequency region clustering around the values 0.4, 0.75, and 1 mHz. Usually, the spatial localization of these maxima mutually coincides and, in our opinion, coincides with the chromospheric network boundary. Acoustic 3- and 5-min oscillations are enhanced in the coronal hole region and reach 1 km s–1 in the photosphere and 3–4 km s–1 in the chromosphere. These oscillations are not localized spatially and are distinguished throughout the entire region observed.  相似文献   

6.
The T Tauri variable V1331 Cyg is characterized by an intensive emission spectrum, by signatures of a high rate of mass loss, and also by presence of a circular reflection nebula. According to these characteristics, the star can be considered as a possible pre-FUor star. Up to the present the photospheric spectrum of the star has not been recorded. In this work we analyze the high-resolution spectra of V1331 Cyg that were obtained by G.H. Herbig with the HIRES spectrograph at the Keck-1 telescope in 2004 and 2007. For the first time the numerous photospheric lines of the star have been detected and the spectral class has been estimated, viz., G7-K0 IV. It is revealed that the projection of the rotation velocity is lower than the width of instrumental profile (vsini < 6 km/s); this means that the angle between the stellar axis of rotation and the line of sight is small. The radial velocity of the star derived from the photospheric lines is RV = ?15.0 ± 0.3 km/s. The difference in radial velocities for 2004 and 2007 is lower than the measurement error. The photospheric spectrum is veiled considerably, but the amount of veiling is not the same in different lines. This depends on the line strength in the template spectrum of the G7 IV star: in the weakest lines (EW = 5–10 mÅ in the template spectrum) VF ≈ 1 and it increases up to 4–5 in stronger lines. The Hα and Hβ lines demonstrate classical P Cyg profiles, which testifies to an intensive wind with a maximal velocity of about 400 km/s. In addition, the emission lines of Fe II, Mg I and K I and of several other elements are accompanied by a narrow blue-shifted absorption at ?150...?250 km/s. The emission spectrum of V1331 Cyg is rich in the narrow (FWHM = 30–50 km/s) lines of neutral and ionized metals showing the excitation temperature T exc = 3800 ± 300 K. The stellar mass M* ≈ 2.8M ⊙ and radius R* ≈ 5R ⊙ are estimated.  相似文献   

7.
The dependence on the temperature of photospheric line‐depth ratios (LDRs) in the spectral range 6190–6280 Å is investigated by using a sample of 174 ELODIE Archive stellar spectra of luminosity class from V to III. The rotational broadening effect on LDRs is also studied. We provide useful calibrations of effective temperature versus LDRs for giant and main sequence stars with 3800 ≃ Teff ≃6000 K and v sin i in the range 0–30 km s–1. We found that, with the exception of very few line pairs, LDRs, measured at a spectral resolution as high as 42 000, depend on v sin i and that, by neglecting the rotational broadening effect, the Teff determination can be wrong by ∼100 K in the worst cases. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

8.
We have carried out an analysis of the (0, 0) vibrational band of the CN molecule in Comet Mrkos 1957d, including the effect of collisions. We found that the sum of the squares of the residuals can be reduced by a factor of ten, if collisions account for 46±3% of the population of the lower level. A rotational temperature can be assigned to the cometary gas. The best value found was 410±40 K. The best fit for the constantR 1 was (1.07±0.10)×10–4. The velocity of the comet was left as a free parameter. We found for it a value of 34.38±0.10 km s–1. This result is in disagreement with the nuclear orbital velocity of 34.74 km s–1. The discrepancy can be explained, if the CN molecules are ejected from the cometary nucleus preferentially in the sunward direction, with a mean velocity that corresponds to the above temperature.  相似文献   

9.
An attempt is made to detect the lines of Mg25H and Mg26H in the photospheric spectrum, using calculated isotope shifts. From comparisons with the Mg24H lines of the 2 –2 transition in the (0, 0) band the ratios Mg25/Mg24 = 0.12 ± 0.04 and Mg26/Mg24 = 0.12 ± 0.02 are derived. These are essentially the same as the terrestrial ratios. The profile of one line of Mgi confirms these values.The wavelengths of MgH and C2 lines, when corrected for the gravitational red shift, indicate that macroturbulent (or streaming) velocities die out near log 0 = – 1.0. From the equivalent widths of the MgH lines a rotational temperature of 5132 ± 200 K is obtained and compared to predictions from various model atmospheres. The band oscillator strength is found to be 0.024 ± 0.002, in serious disagreement with the single laboratory determination.The profiles of MgH, C2, CN and some weak atomic lines are used to derive the variation of the radial component of microturbulence with optical depth, on the assumption of streaming velocities of 2.5–3.0 km/sec. A slow increase with increasing height in the photosphere is found, over the range –1.5 < log0< 0.2.The center-limb variation of the equivalent widths of MgH and C2 lines for a wholly inhomogeneous model is found to be the same as for a model which is homogeneous above log 0 = - 1.0. With such a model as the latter, the center-limb variation of the profiles of the selected molecular and atomic lines is moderately-well reproduced by an anisotropic microturbulent velocity with a tangential component of 3 km/sec which seems to be constant with height over the range considered.  相似文献   

10.
Rutten  R. J.  Hoyng  P.  De Jager  C. 《Solar physics》1974,36(2):321-337
The steady-state vertical-velocity response of an isothermal atmosphere to pressure fluctuations of arbitrary period and horizontal wavelength at its base is derived in the approximation of dissipationless polytropic motion in the atmosphere. It is pointed out that, since only upward modes can be excited in an isothermal atmosphere perturbed from below, the infinite response found by Worrall (1972) at the critical frequency g does not occur. The correct behavior of the response is presented in some detail.Comparison of the response of the model, for the case of isothermal osculations, with observed features of the photospheric oscillations indicates that, in addition to the evanescent photospheric oscillations which occur at the compression-wave propagation cut-off frequencies and which have horizontal wavelengths 3000 km, in the lower photosphere there are also smaller-scale evanescent oscillations which have horizontal wavelengths 1000 km, periods ranging from 200 to 400 s, amplitudes comparable to that of the larger-scale oscillations, and in which the phase of the vertical velocity oscillation leads the phase of the pressure oscillation.  相似文献   

11.
Results of ourmeasurements of the longitudinal magnetic field B z for the young star RWAur A are presented. B z measured from the so-called narrow component of the He I 5876 line varies in the range from −1.47 ± 0.15 to +1.10 ± 0.15 kG. Our data are consistent with a stellar rotation period of }~5.6 days and the model of two hot spots with opposite magnetic field polarities spaced about 180° apart in longitude. Relative to the Earth, the spot with B z < 0 lies in the hemisphere above the midplane of the accretion disk, while the spot with B z > 0 is below the midplane. The upper limit for B z (at the 3σ level) obtained by averaging all observations is 180 G for the photosphere and 220 and 230 G for the Hα and [OI] 6300 line formation regions, respectively. We have also failed to detect a field in the formation region of broad emission line components: the upper limit for B z is 600 G. In two of 11 cases, we have detected a magnetic field in the formation region of the blue absorption wing of the Na I D doublet lines, i.e., in the wind from RW Aur A: B z = −180 ± 50 and −810 ± 80 G. The radial velocity of the photospheric lines in RW Aur A averaged over all our observations is }~+10.5 km s−1, i.e., a value lower than that obtained by Petrov et al. (2001) ten years earlier by 5.5 km s−1. Therefore, we discuss the possibility that RW Aur is not a binary but a triple system.  相似文献   

12.
We observe vertical velocity oscillations in some sunspot umbrae with periods of about 180 s and peak to peak amplitudes up to 1 km s–1. These oscillations are not visible in either the line depth, line width or the continuum intensity. No correlation seems to exist between the occurence of these oscillations and the presence of the chromospheric umbral flashes (Solar Phys. 7, 351, 1069). In the spot penumbra there is an indication of a long period oscillation, the period increasing from about 300 s in the inner penumbra to nearly 1000 s at the penumbra-photosphere boundary. An attempt has been made to interpret these oscillations in terms of gravity or acoustic waves, travelling along the magnetic field lines, taking into account the variation of scale height and magnetic field direction across the sunspot.  相似文献   

13.
Observations of the 1.10- and 1.18-μm nightside windows by the SPICAV-IR instrument aboard Venus Express were analyzed to characterize the various sources of gaseous opacity and determine the H2O mole fraction in the lower atmosphere of Venus. We showed that the line profile model of Afanasenko and Rodin (Afanasenko, T.S., Rodin, A.V. [2007]. Astron. Lett. 33, 203–210) underestimates the CO2 absorption in the high-wavelength wing of the 1.18-μm window and we derived an empirical lineshape that matches this wing well. An additional continuum opacity is required to reproduce the variation of the 1.10- and 1.18-μm radiances with surface elevation as observed by the VIRTIS-M instrument aboard Venus Express. A constant absorption coefficient of 0.7 ± 0.2 × 10−9 cm−1 am−2 best reproduces the observed variation. We compared spectra calculated with different CO2 and H2O line lists. We found that the CDSD line list lacks the 5ν1 + ν3 series of CO2 bands, which provide significant opacity in Venus’ deep atmosphere, and we have constructed a composite line list that best reproduces the observations. We also showed for the first time that HDO brings significant absorption at 1140–1190 nm. Using the best representation of the atmospheric opacity we could reach, we retrieved a water vapor mole fraction of ppmv, pertaining to the altitude range 5–25 km. Combined with previous measurements in the 1.74- and 2.3-μm windows, this result provides strong evidence for a uniform H2O profile below 40 km, in agreement with chemical models.  相似文献   

14.
We have used a 5.5 min time-sequence of spectra in the Fe i lines 5576 (magnetically insensitive), 6301.5 and 6302.5 (magnetically sensitive) to study the association of concentrated magnetic regions and velocity in the quiet Sun. After the elimination of photospheric oscillations we found downflows of 100–300 m s –1, displaced by about 2 from the peaks of the magnetic field; this velocity is comparable to downflow velocity associated with the granulation and of the same order or smaller than the oscillation amplitude. Quasi-periodic time variations of the vertical component of the magnetic field up to ± 40% were also found with a period near 250 s, close to the values found for the velocity field. Finally we report a possible association of intensity maxima at the line center with peaks of the oscillation amplitude.  相似文献   

15.
Photospheric motion shears or twists solar magnetic fields to increase magnetic energy in the corona, because this process may change a current-free state of a coronal field to force-free states which carry electric current. This paper analyzes both linear and nonlinear two-dimensional force-free magnetic field models and derives relations of magnetic energy buildup with photospheric velocity field. When realistic data of solar magnetic field (B 0 103 G) and photospheric velocity field (v max 1 km s–1) are used, it is found that 3–4 hours are needed to create an amount of free magnetic energy which is of the order of the current-free field energy. Furthermore, the paper studies situations in which finite magnetic diffusivities in photospheric plasma are introduced. The shearing motion increases coronal magnetic energy, while the photospheric diffusion reduces the energy. The variation of magnetic energy in the coronal region, then, depends on which process dominates.  相似文献   

16.
In this paper, we analyze the relations between photospheric vector magnetic fields, chromospheric longitudinal magnetic fields and velocity fields in a solar active region. Agreements between the photospheric and chromospheric magnetograms can be found in large-scale structures or in the stronger magnetic structures, but differences also can be found in the fine structures or in other places, which reflect the variation of the magnetic force lines from the photosphere to the chromosphere. The chromospheric superpenumbral magnetic field, measured by the Hline, presents a spoke-like structure. It consists of thick magnetic fibrils which are different from photospheric penumbral magnetic fibrils. The outer superpenumbral magnetic field is almost horizontal. The direction of the chromospheric magnetic fibrils is generally parallel to the transverse components of the photospheric vector magnetic fields. The chromospheric material flow is coupled with the magnetic field structure. The structures of the H chromospheric magnetic fibrils in the network are similar to H dark fibrils, and the feet of the magnetic fibrils are located at the photospheric magnetic elements.  相似文献   

17.
Intensity images and Doppler-velocity maps of the quiet sun in different heights are obtained from simultaneously recorded spectra of different lines. A relation between the intensity images is recognizable up to formation heights of 900 km above continuum, but the correlation coefficient changes sign above 400 km. The core of Hα shows a different pattern without any correlation to the continuum layer. Extreme Doppler velocities as well as the rms-velocities have minima at a height of 400 km, values of about 2 km/s occur in deep photospheric layers and 2.5 km/s in a height of 900 km. The velocities in the lower and in the upper photosphere are well correlated indicating that the pattern of the velocity field is preserved up to higher layers than the intensity pattern. Hα-velocities reach values up to 10 km/s and more, they show no correlation with the continuum intensities and almost no with the line core intensities.  相似文献   

18.
Observations have been made in H of the vertical velocity distribution in a sunspot. Over the umbra the pattern consists of structures of scale-size 2–3. The velocity distribution undergoes oscillations with a period of about 165 s and typical amplitude ±3 km s–1, but the pattern breaks down after one or two cycles because the period of oscillation varies typically by ±20 s from place to place. Transverse waves develop in the outer 0.1 of the umbral radius and propagate outwards with a velocity of about 20 km s–1, becoming gradually invisible by or before the outer penumbral boundary; the amplitude is about ±1 km s–1 at the umbra-penumbra border.The penumbral waves are believed to be basically of the Alfvén type, with 3 × 10–8 g cm–3. The umbral oscillations presumably represent gravity waves. In both cases the fluxes are inadequate by two orders of magnitude to account for the sunspot energy deficit.  相似文献   

19.
Rhodes  Edward J.  Harvey  John W.  Duvall  Thomas L. 《Solar physics》1983,82(1-2):111-111

A brief summary is given of a program which is currently being carried out with the McMath telescope of the Kitt Peak National Observatory in order to study high-degree (l ≳ 150) solar p-mode oscillations. This program uses a 244 × 248 pixel CID camera and the main spectrograph of the McMath telescope to obtain velocity-time maps of the oscillations which can be converted into two-dimensional (k h - ω) power spectra of the oscillations. Several different regions of the solar spectrum have been used in order to study the oscillations at different elevations in the solar atmosphere. The program concentrates on eastward- and westward-propagating sectoral harmonic waves so that measurements can be made of the absolute rotational velocities of the solar photospheric and shallow sub-photospheric layers. Some preliminary results from this program are now available. First, we have been unable to confirm the existence of a radial gradient in the equatorial rotational velocity as was previously suggested. Second, we have indeed been able to confirm the presence of p-mode waves in the solar chromosphere as was first suggested by Rhodes et al. (1977). Third, we have been able to demonstrate differences in photospheric and chromospheric power spectra.

  相似文献   

20.
The present paper is devoted to the interpretation of linear polarization data obtained in 14 quiescent prominences with the Pic-du-Midi coronagraph-polarimeter by J. L. Leroy, in the two lines Hei D3 andH quasi-simultaneously. The linear polarization of the lines is due to scattering of the anisotropic photospheric radiation, modified by the Hanle effect due to the local magnetic field. The interpretation of the polarization data in the two lines is able to provide the 3 components of the magnetic field vector, and one extra parameter, namely the electron density, because the linear polarization of H is also sensitive to the depolarizing effect of collisions with the electrons and protons of the medium. Moreover, by using two lines with different optical thicknesses, namely Hei D3, which is optically thin, and H, which is optically thick ( = 1), it is possible to solve the fundamental ambiguity, each line providing two field vector solutions that are symmetrical in direction with respect to the line of sight in the case of the optically thin line, and which have a different symmetry in the case of the optically thick line.It is then possible to determine without ambiguity the polarity of the prominence magnetic field with respect to that of the photospheric field: 12 prominences are found to be Inverse polarity prominences, whereas 2 prominences are found to be Normal polarity prominences. It must be noticed that in 12 of the 14 cases, the line-of-sight component of the magnetic field vector has a Normal polarity (to the extent that the notion of polarity of a vector component is meaningful; no polarity can be derived in the 2 remaining cases); this may explain the controversy between the results obtained with methods based on the Hanle effect with results obtained through the Zeeman effect. A dip of the magnetic field lines across the prominence has been assumed, to which the optically thick H line is sensitive, and the optically thin Hei D3 line is insensitive.For the Inverse prominences, the average field strength is 7.5±1.2 G, the average angle,, between the field vector and the prominence long axis is 36° ± 15°, the average angle, , between the outgoing field lines and the solar surface at the prominence boundary is 29° ± 20°, and the average electron density is 2.1 × 1010 ± 0.7 × 1010 cm–3. For the Normal prominences, the average field strength is 13.2±2.0 G, the average angle,, between the field vector and the prominence long axis is 53° ± 15°, the average angle, , between the outgoing field lines and the solar surface at the prominence boundary is 0° ± 20° (horizontal field), and the average electron density is 8.7 × 109 ± 3.0 × 109 cm–3.  相似文献   

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