共查询到20条相似文献，搜索用时 234 毫秒
1.
Claudio Bastos Pereira 《Astrophysics and Space Science》1996,235(2):305-318
EG And is a S-type symbiotic star. Here is present UV observations made by IUE from 1978 to 1991. From these observations the electronic density and the electronic temperature were obtained. The size of He II emitting region was estimated as 7.3R
. Line and continuum variations confirm the binary nature of EG And. 相似文献
2.
R. A. Gulyaev 《Solar physics》1972,24(1):72-78
An analysis of the spectral distribution of intensity of the Hei recombination continuum is probably the only direct method for determination of the electron temperature of helium emission regions on the Sun. On the basis of data on the Hei Lyman continuum, obtained by Dupree and Reeves from OSO-4, the electron temperature of undisturbed helium regions is determined: T
e
= = 12500 K. Such a low T
e
value is a serious argument in favour of the predominant role of UV coronal radiation in the helium ionization on the Sun. Comparison of the Hei Lyman continuum data with results of observations of the 10830 line showed that the visible helium lines and Hei Lyman continuum are produced within the same regions of the undisturbed solar atmosphere at T
e
= 12500 K. 相似文献
3.
K. Avcioğlu 《Astrophysics and Space Science》1984,106(2):341-353
With the aid of the spectra taken in the years 1959–1968, a physical analysis of the atmosphere of P Cygni has been carried out and the motions of the atmosphere have been studied. The variations of radial velocities, the velocity progressions of Balmer and Hei lines, the high rate of mass loss (2×10–5
M
yr–1), the features of the observed line profiles, especially that of H-K lines of Caii andD
1-D
2 lines of Nai confirm the conclusion of Van Blerkom (1978), concerning the assumption of an accelerating atmosphere for P Cygni. The electron density variation with the radius seems to ben
e
r
–5/2, with an average value of 7×1011cm–3 at the lower boundary of the atmosphere.In order to explain the two absorption components of observed lines, an atmospheric model based on the assumption of three envelopes, two of which accelerate gradually with two different velocity laws (up to 11.2r
c
), and the third of which accelerates rapidly with a standard velocity law (beyond 11.2r
c
) has been developed. From this model and the observed profiles, the geometrical thicknesses of the line-forming regions of H, H, H, and H are derived.The observations were obtained at Haute Provence Observatory (CNRS). 相似文献
4.
Slitless flash spectrograms in heights below 8000 km above the solar limb were obtained by the University of Kyoto Expedition at Atar, Mauritania. The integrated intensities of Fexiv
5303, Fex
6374, Fexi
7892, and the continuum are measured as a function of height above the solar limb at eleven points (P.A. = 284–300°) around the third contact point. It is found that a significant amount of the emission in Fex
6374 originates in chromospheric levels well below 8000 km. This implies that the interspicular region of the chromosphere is occupied by coronal material. The average values of the electron temperature and the electron density in the interspicular region are derived from the Fex
6374 and the Fexi
7892 intensities on the assumption of spherical symmetry: T
e = 0.9–1.1 × 106 K and N
e = 9–10 × 108 cm–3. The intensity variations of the coronal lines and the continuum with position angle are also studied. Strong correlations between Fexiv
5303 and the continuum and between Fex
6374 and Fexi
7892 are found. From the Fex
6374 intensities it is inferred that there is a density fluctuation in the innermost corona by at least a factor of two.Contributions from the Kwasan and Hida Observatories, University of Kyoto, No. 271. 相似文献
5.
R. J. García López R. Rebolo J. E. Beckman C. D. McKeith 《Astrophysics and Space Science》1990,169(1-2):67-75
We give the first results of a study in F-type MS stars using the Hei
D
3 absorption feature at 5876 Å as an indicator of stellar activity and structure. The observations were obtained with the QUB echelle spectrograph at the Cassegrain focus of the 4.2 m William Herschel telescope, and have spectral resolution /6×104, and signal-to-noise ratios 200. We chose as a first sample 17 F-stars of the Hyades Main Sequence. It was found that Hei
D
3 and X-ray emission appear aroundB-V 0.3, indicating the onset of sub-surface convection zones. Below this value, in stars withB-V0.42–0.44 the behaviour of the Hei
D
3 equivalent width against Rossby number is different from that observed in later type stars, indicating that the presence of nonradiative mechanisms other than dynamo must be important in heating the chromospheres of these hotter stars.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.Based on observations made with the William Herschel telescope, operated on the island of La Palma by the Royal Greenwich Observatory, in the Spanish Observatorio del Roque de Los Muchachos of the Instituto de Astrofisica de Canarias. 相似文献
6.
The physical properties in the coronal disturbance (CD) (W90, N25°) associated with an active prominence are investigated on the basis of the intensities and profiles of 5694 Å Caxv and 6702 Å Nixv lines and continuum measured in the eclipse coronal spectra of 31 July, 1981. The spectrograms have been taken with a dispersion of between 7 to 10 Å mm-1 and a solar image of 15 mm in diameter. The following characteristics of the CD have been deduced. The CD occurred cospatially with an active prominence and consisted of two discrete regions with different temperatures penetrating each other. (1) Caxv region: T
e= 3.8 × 106 K, the length along the slit of the spectrograph Z 65000 km, the effective line-of-sight length L 20000 km, the average electron density
, nonthermal velocities V
t= (20–32) km s-1. (2)Nixv-Caxiii region: T
e= 2.3 × 106 K, Z 37000 km, L 35000 km, n
e 1 × 109 cm-3, V
t= (23–30) km s-1. A macroscopic mass motion has been discovered within the Nixv region of the CD from the Doppler shifts of the 6702 Å Nixv line: V
r= + 27 km s-1 on the lower and V
r= - 12 km s-1 on the upper border of the CD. The average height of the CD was H 0.08 R
. The radial velocities in the prominence found from the emission line tilts are + 12 and - 8 km s-1 on its lower and upper borders. A similar picture of the mass motion in the CD and the prominence speaks in favour of an intimate relation between them. 相似文献
7.
In order to study the electron density at the scale of the most encountered structures in coronal active regions a new multichannel coronagraph associated with a photoelectric spectrograph is now used at the Pic-du-Midi Observatory. In its quasi-routine mode this instrument, which is described in this paper, works with a 30 field aperture in a parallel manner with aK-polarimeter. On each observed region it obtains maps of intensities of the
3388, 10747, and 10798 Å emission lines due to Fexiii ion. Each measurement point is associated with a quasi-simultaneous image of the emission corona structures viewed in the light of the5303 Å line of Fexiv. Three examples of observations are given and the capabilities are discussed.Measuring electron density in coronal active regions. II A multichannel photoelectric coronagraph with a photo-electric spectrograph and a reflex monitor at5303 Å.LA du CNRS No. 040285. 相似文献
8.
B. N. Dwivedi 《Solar physics》1994,153(1-2):199-203
Emission lines from an active region, observed by SERTS, have been used to determine electron densities from theoretical curves for Mgvii, Siviii, and Siix density-sensitive line ratios. Density diagnostics of Alviii 285.46/323.52 line emissivity ratio has also been investigated. 相似文献
9.
A. I. Poland M. E. Machado C. J. Wolfson K. J. Frost B. E. Woodgate R. A. Shine P. J. Kenny C. C. Cheng E. A. Tandberg-Hanssen E. C. Bruner W. Henze 《Solar physics》1982,78(2):201-213
Simultaneous observations of a solar limb flare in the X-ray and ultraviolet regions of the spectrum are presented. Temporal and spectral X-ray observations were obtained for the 25–300 keV range while temporal, spectral, and spatial X-ray observations were obtained for the 30–0.3 keV range. The ultraviolet observations were images with a 10 spatial resolution in the lines of O v (T
e 2.5 × 105 K) and Fe xxi (T
e 1.1 × 107 K). The hard X-ray and O v data indicate that the impulsive phase began in the photosphere or chromosphere and continued for several minutes as material was ejected into the corona. Impulsive excitation was observed up to 30 000 km above the solar surface at specific points in the flare loop. The Fe xxi observations indicate a preheating before the impulsive phase and showed the formation of hot post-flare loops. This later formation was confirmed by soft X-ray observations. These observations provide limitations for current flare models and will provide the data needed for initial conditions in modeling the concurrent coronal transient. 相似文献
10.
George L. Withbroe 《Solar physics》1971,18(3):458-473
Characteristics of the emission observed above the solar limb in four EUV lines, Sixii
499, Mgx
625, Neviii
770, and Ovi
1032 are discussed. The mean temperature of the corona derived from the ratios of the intensities of Sixii
499 and Mgx
625 is 1.8 million K. There do not appear to be significant temperature differences in regions with low EUV intensities and those with high EUV intensities, suggesting that the EUV emission from the lithium-like ions depends primarily on the integral of n
e
2 along the line of sight.The EUV data are compared with K-coronameter measurements in order to yield new estimates of the abundances of Si, Mg, Ne and O relative to hydrogen. Within the uncertainties of the analysis, these coronal abundances are in agreement with the corresponding photospheric values. 相似文献
11.
I. N. Azcárate 《Astrophysics and Space Science》1992,194(2):225-228
SeveralHii regions were observed in the Instituto Argentina de Radioastronomía (IAR) in the H166 line and 1.4 GHz radio continuum. Resulting physical parameters derived from low-frequency (H166 line) and high-frequency (H110, H109, H76 line, made by other authors) observations ofHii regions are compared. Low-frequency derived parameters describe better the low-density ionized gas conditions, whereas high-frequency observations are more sensitive to high density ionized gas located in the central parts of the nebulae. 相似文献
12.
The data on the spectrum of the cosmic-ray electron component near the earth, on the radio-spectra of radio-galaxies, quasars and the Crab Nebula, as well as the data pertaining to the X-ray spectrum of the cosmic background, all agree that the sources of cosmic-ray electrons (such as supernovae and galactic nuclei) inject particles characterized by a power spectrumN(E)=KE
–0, with 01.5–2.5. A mechanism is known in which the source emits a proton-nuclear component of cosmic rays with a spectrumN
n
(E)=K
n
E
–
n, n = + 2, =w
cr/(w–w
cr), wherew
cr is the cosmic-ray energy density in the source, andw=w
cr+w
n+w
turb, the total energy density. We obtain =2.5 in agreement with observations on the natural assumption that =0.5. Within the framework of the same model with some additional assumptions, the electrons in the source, as well as those ejected by the source, are shown to have a power-spectrum characterized with 0 n = + 2. Thus the model discussed gives an adequate spectrum for both the proton-nuclear and the electron components of cosmic rays. 相似文献
13.
From high-resolution maps of the spiral galaxies NGC 3992 and NGC 4321, obtained with the TAURUS camera at the 4.2 m William Herschel Telescope, we have inferred: (a) The total number of separately identifiableHii regions in their discs classified according to their membership of a spiral arm or the interarm disc, (b) the radial distribution ofHii regions, (c) the frequency distribution of diameters ofHii regions, (d) the luminosity function; each parameter rpesented separately for theHii regions in the arms and in the interarm region, showing the differences between them. From these observations we have also derived the radial dependence of the product of the filling factor, the electron density, and the ionized hydrogen density, which does not appear to change between arm and interarm disc.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.
Electron density in a coronal hole is rediscussed using the new calculation for the Mgviii 436.62/430.47 density-sensitive theoretical line ratio and with the help of available observations. 相似文献
15.
We compute a new grid of plage models to determine the difference in temperature versus mass column density structure T(m) between plage regions and the quiet solar chromosphere, and to test whether the solar chromosphere is geometrically thinner in plages. We compare partial redistribution calculations of Mg ii h and k and Ca ii K to NRL Skylab observations of Mg ii h and k in six active regions and Ca ii K intensities obtained from spectroheliograms taken at approximately the same time as the Mg ii observations. We find that the plage observations are better matched by models with linear (in log m) temperature distributions and larger values of m
0 (the mass column density at the 8000 K layer in the chromosphere), than by models with larger low chromosphere temperature gradients but values of m
0 similar to the quiet Sun. Our derived temperature structures are in agreement with the grid originally proposed by Shine and Linsky, but our analysis is in contrast to the study by Kelch which implies that stellar chromospheric geometrical thickness is not affected by chromospheric activity. We conclude that either the stellar Mg ii observations upon which the Kelch study was based are of poorer quality than had been assumed, or that the spatial averaging of inhomogeneous structures, which is inherent in the stellar data, does not lead to a best fit one-component model similar in detail to that of a stellar or a solar plage.Visiting Astronomer at Kitt Peak National Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.Staff member, Quantum Physics Division, National Bureau of Standards. 相似文献
16.
Recent R-matrix calculations of electron impact excitation rates in Fe xii are used to derive the theoretical emission line ratio R
1 = I(195.1 Å)/I(1242 Å), which is potentially a useful electron density diagnostic for the solar inner corona (r 1.05 61-01). These results are found to be significantly different from the earlier estimates of Withbroe and Raymond (1984), but are in good agreement with the observed values of R
1, for the quiet Sun and an active region. Adoption of the R-matrix atomic data for the 1242 Å line in the coronal iron abundance determination removes an existing discrepancy between results derived from the EUV transition and other iron lines in the solar XUV spectrum. The R-matrix calculations confirm the prediction of Withbroe and Raymond that the earlier discrepancies in R
1 and the iron abundance were due to the 1242 Å line excitation rates being underestimated by a factor of ~2. Withbroe and Raymond's paper is, therefore, an excellent example of how astronomical observations can be used to accurately predict atomic physics data. 相似文献
17.
Previously published solar abundances of oxygen and carbon can be corrected to be logN(O) = 8.93 and logN(C) = 8.60 on the hydrogen log-scale when new accurate forbidden electric quadrupole transition probabilities A
Q(s–1) are used. Such A
Q's, based on the new atomic structure and electron correlation theory, developed recently by Sinanolu and coworkers, are reported for the (1
S
0-1
D
2) lines of [C i], [N ii, [O i] and [O iii] and the (2
P-2
D) lines of [N i] and [O ii]. The available experimental values are also given for comparison.Work supported by Grant No. GP-29471 from the U.S. National Science Foundation. 相似文献
18.
We have calculated for extragalactic Hii regions, the expected relationship between the radio flux at 11 cm and the infrared flux at 11 and 20 m based on the grain models and the parameters which fit the observations of galactic Hii regions. It is shown that the measured infrared fluxes of extragalactic Hii regions are consistent with the expected infrared fluxes for these objects. 相似文献
19.
Taking into account the effect of roughness (or local departures from sphericity) of the emitting layers in the chromosphere-corona transition zone (CCT) allows one to determine the optical depths of layers responsible for resolved structures in Cii, Ciii, Oiv, and Ovi lines. The result, at the top of the irregularities, is of the order of respectively 1 3.5,2.0, 1.6,0.5, and for the bottom of these irregularities, 2 = 0.7, 0.4, 0.3, 0.25. The characteristic angle of these irregularities is, respectively, of the order of 35 °, 33 °, 35 °, and 41 °. For unresolved structures of Civ and Ovi (already analyzed in the spherical symmetry hypothesis in Paper III), one finds 1 0.6; 0.9 and 2 0.12; 0.2 in the case of quiet areas; in the case of active areas, the range is broader for Civ and Ovi, from 1.0 to 1.7 for 1 and from 0.2 to 0.9 for 2. The values obtained from Ovi are in reasonable agreement with each other for resolved and unresolved structures. And the obtained values of 1 and 2 correspond not too badly with the determinations made in Paper III, by methods not exceedingly influenced by the spherical symmetry hypothesis. 相似文献
20.
Calculations of electron temperature (T
e) and density (N
e) sensitive line ratios in Sixi involving transitions in the 358–604 wavelength range are presented. These are shown in the form of ratio-ratio diagrams, which should in principle allow bothN
e andT
e to be deduced for the Sixi line-emitting region of a plasma. However a comparison of these with observational data for two solar flares, obtained with the Naval Research Laboratory's S082A spectrograph on boardSkylab, reveals that the experimental ratios are much larger than expected from theory, which is probably due to the Sixi lines in the S082A spectra being blended with transitions from species including Nev, Fexi, and Fexii. Possible future applications of the Sixi results to spectral data from the Coronal Diagnostic Spectrometer on the Solar and Heliospheric Observatory are briefly discussed. 相似文献