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1.
Bengt Edĺen 《Solar physics》1972,24(2):356-367
Values of the level intervals in the ground configurations 2s
2 2p
2, 2s
2 2p
3 and 2s
2 2p
4 have been critically compiled from laboratory observations and from observations of nebular and coronal forbidden transitions. The data are represented within experimental errors by means of semi-empirical extrapolation formulae which contain from 3 to 5 adjusted parameters. The results provide means for checking laboratory and astrophysical identifications and measurements. Tables of best level values are given for the configurations concerned. 相似文献
2.
Results of H interferometric observations of NGC 7793 are reported. This galaxy contains about 93 HII regions and a general emission background. Its radial velocity is 215 km s–1.The total mass is low, 2–3×109 solar masses, as well as the average density; the meanM/L is 0.4 suggesting a high proportion of young objects. 相似文献
3.
Richard C. Canfield 《Solar physics》1976,50(2):239-254
Previous observations of spatially-resolved vertical velocity variations in ten lines of Fe i spanning the height range 0 h 1000 km are re-analyzed using velocity weighting functions. The amplitudes and scale heights of granular and oscillatory velocities are determined, as well as those of the remaining unresolved velocities. I find that the optimal representation of the amplitude of the outward-decreasing granular velocities is an exponentially decreasing function of height, with a scale height of 150 km and a velocity at zero height of 1.27 km s–1. The optimal representation of the same quantities for oscillatory velocities is an exponential increase with height, with a scale height of 1100 km and a velocity at zero height of 0.35 km s–1. The remaining unresolved velocities decrease with height, with a scale height of 380 km and a velocity at zero height of 2.3 km s–1. 相似文献
4.
The revised Mount Wilson synoptic magnetic data for the period September 1987 through March 1996 are used as the basis of numerical simulations of the evolution of both the northern and southern polar magnetic fields during the reversal and declining phases of cycle 22. The simulations are based on numerical solutions of the flux-transport equation which involve, as parameters, the maximum meridional flow speed, v
0, and the supergranule diffusivity, . By matching characteristics of the observed and simulated fields, such as the observed reversal times, the evolution of the net flux above 60 °, and the migration of the polar crown, empirical values of these parameters, i.e., v
0=11 m s–1,=600 km2 s–1, may be determined. Further, the observed decrease in the mean net flux above 60 ° during the late declining phase of cycle 22 can be simulated only by increasing the diffusivity to 900 km2 s–1. However, direct observations of the supergranule velocities yield values of the diffusivity of order 200 km2 s–1, and we show that the inclusion of a pattern of emerging bipoles in the simulations can increase the diffusion of these fields and that, together with a more realistic value of the diffusivity, it is possible to reproduce qualitatively the features of the observed polar field reversals. 相似文献
5.
Keenan F.P. Pinfield D.J. Mathioudakis M. Aggarwal K.M. Thomas R.J. Brosius J.W. 《Solar physics》2000,197(2):253-262
Theoretical electron density sensitive emission line ratios involving a total of eleven 2s
22p
2–2s2p
3 transitions in Sxi between 187 and 292 Å are presented. A comparison of these with solar active region observations obtained during rocket flights by the Solar EUV Rocket Telescope and Spectrograph (SERTS) reveals generally good agreement between theory and experiment. However, the 186.87 Å line is masked by fairly strong Fexii emission at the same wavelength, while 239.83 Å is blended with an unknown feature, and 285.58 Å is blended with possibly Niv 285.56 Å. In addition, the 191.23 Å line appears to be more seriously blended with an Fexiii feature than previously believed. The presence of several new Sxi lines is confirmed in the SERTS spectra, at wavelengths of 188.66, 247.14 and 291.59 Å, in excellent agreement with laboratory measurements. In particular, the detection of the 2s
22p
2
3
P
1 –2s2p
3
3
P
0,1 transitions at 242.91 Å is the first time (to our knowledge) that this feature has been identified in the solar spectrum. The potential usefulness of the Sxi line ratios as electron density diagnostics for the solar transition region and corona is briefly discussed. 相似文献
6.
F.P. Keenan M. Mathioudakis A.C. Katsiyannis C.A. Ramsbottom K.L. Bell R.J. Thomas J.W. Brosius 《Solar physics》2002,205(2):265-277
R-matrix calculations of electron impact excitation rates in N-like Mgvi are used to derive theoretical electron-density-sensitive emission line ratios involving 2s
22p
3–2s2p
4transitions in the 269–403 Å wavelength range. A comparison of these with observations of a solar active region, obtained during the 1989 flight of the Solar EUV Rocket Telescope and Spectrograph (SERTS), reveals good agreement between theory and observation for the 2s
22p
3
4
S–2s2p
4
4
Ptransitions at 399.28, 400.67, and 403.30 Å, and the 2s
22p
3
2
P–2s2p
4
2
Dlines at 387.77 and 387.97 Å. However, intensities for the other lines attributed to Mgvi in this spectrum by various authors do not match the present theoretical predictions. We argue that these discrepancies are not due to errors in the adopted atomic data, as previously suggested, but rather to observational uncertainties or mis-identifications. Some of the features previously identified as Mgvi lines in the SERTS spectrum, such as 291.36 and 293.15 Å, are judged to be noise, while others (including 349.16 Å) appear to be blended. 相似文献
7.
A. M. I. Osman 《Astrophysics and Space Science》1986,124(2):345-357
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
8.
A rocket-borne coronagraph utilizing external occulting disks was used to photograph the solar corona from 3 to 9 R
s at 1931 UT on 7 March, 1970. Comparison of the rocket and ground-based observations shows a one-to-one correspondence between major streamers from the inner to the outer corona. In particular streamers over the poles are clearly visible against the background corona from 3 to 8 R
s. These rocket data had a scattered light level of 1.2 × 10–10
B
s. The derived quiet equatorial and polar K + F corona was within 10% of the absolute brightness of standard coronal models and displayed identical radial gradients to those models. The photometric profiles of the NE limb streamer were analyzed assuming a model in which the core density follows a Gaussian distribution in directions perpendicular to the radius vector. This streamer was assumed to be rooted on the visible disk at 55 to 60° from the plane-of-the-sky as based on K-coronameter and XUV data. An uncertainty of as much as a factor of three still remains for the value of the axis density owing to uncertainty in the line-of-sight dimension of the streamer. 相似文献
9.
Spectrophotometric observations of the RS CVn binary system V711 Tau (HR 1099), convering the wavelength interval 3300–7100 Å, have been presented. A comparison of the standard spectral scans of V711 Tau with the spectral scans of the stars of known spectral types and luminosity classes taken from the Breger (1976) catalogue shows that, at all phases shown in the diagram, the spectral-luminosity type of the star is K0IV or K0III. The magnitude of the system fluctuates from 5
m
.71 to 5
m
.79 average being 5
m
.75 approximately, the faintest being near 0
p
.43 and the brightest near 0
p
.78. The region around Balmer jump and near H region is apparently variable. 相似文献
10.
On the basis of the possibility of sight-line velocity observations by a special equatorial solar spectrograph, a research programme for detection of photospheric large-scale velocities has been initiated. The first series of observations in the FeI 6302 Å absorption line has been limited to the central meridian.The combined limb effect assumed to incorporate an unresolved stationary photospheric motion, has been evaluated. The observed asymmetry of the obtained curve is mainly explained by dB
0/dt.The remaining sight-line velocities along the central meridian, taken as random, gave an r.m.s. value of 32 m s–1. In a few cases a certain kinematic situation in some areas along the central meridian lasted for 2 to 4 consecutive days. It is assumed that such velocity features belong to the kinematic picture of a large-scale photospheric motion which, as a whole, has not yet been clearly seen. 相似文献
11.
The Monoceros ring, a circular optical nebulosity 3°.5 in diameter and centred at R.A.=6h37m, Dec.=6°30 (l
ii
=205°.5,b
ii
=0°.2) is in good structural agreement with radio observations. A neutral hydrogen shell is also accurately projected on the ring. These observations are consistent with the Monoceros ring being a supernova remnant 90–100 pc in diameter expanding at about 45 km s–1 and having an age of the order of a million years. Bright Hii regions containing early-type stars (e.g., galactic cluster NGC 2244 in the Rosette nebula) and extremely young stars of the OB association Mon OB2 lie at the edges of the ring. The positional and temporal coincidence of the Mon OB2 association with a supernova remnant suggests that probably the star formation in this region is induced or speeded up by the passage of a supernova shock wave through the clumpy interstellar medium. 相似文献
12.
It is the objective of the present study to establish an absolute scale for flows in the solar transition region in observations obtained with the UVSP/SMM. By use of the polar limbs as reference one finds that the downflows range between 3 and 10 km s–1. The brighter regions show the largest downward flows.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
13.
Using the archival ROSAT PSPC observations, AB Dor is found to be variable in X-rays. The periodic variations are consistent with previously reported rotational period of 0
d
.514. The average spectrum of AB Dor is best represented with two-temperature Raymond-Smith model with kT values of 0.19±0.07 and 1.17±0.02 keV. The quiescent luminosity of the system is found to be 4.36±0.6×1030 ergs s–1. A flare with a rise time of 350 seconds is detected during which X-ray luminosity rises from 5.8±1.6×1030 to 15.8±4.9×1030 ergs s–1. We conclude that AB Dor is very similar to the active components of RS CVn binaries and other active classes. In view of the wide separation from the binary companion Rst 137B, this activity must be intrinsic to the active star. 相似文献
14.
The sidereal rotation rate of the high-latitude solar regions is examined using long-lived photospheric polar faculae. The observations were carried out with the photoheliograph of Kislovodsk Mountain Station of the Pulkovo Observatory from 1982 to 1986. The following facts have been established: (a) There is a differential rotation of the polar faculae close to the maximum of solar activity, while the amount of latitude gradient of solar rotation decreases towards the sunspot minimum; (b) small differences of rotation in the northern and southern hemispheres of the Sun are observed; (c) some deviations of differential rotation curves constructed for each Carrington rotation from the mean curve of differential rotation are revealed. The total amplitude of the maximum positive and negative excesses is about 40–50 m s–1. The positive surplus velocities of solar rotation (the amplitude of which is about 20–25 m s–1) move in the form of a wave from heliographic latitudes 40° with a velocity of 1.6 m s–1. The latitude width of this flow is B 15°. This wave of abnormally high velocity starts in the year of minimum solar activity and reaches the pole 11 years later. The picture is symmetrical relative to the equator. 相似文献
15.
Charles H. Nelson Douglas S. Hall Francis C. Fekel Robert E. Fried Richard E. Lines Helen C. Lines 《Astrophysics and Space Science》1991,182(1):1-17
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
16.
Matthew J. Penn Donald L. Mickey Richard C. Canfield Barry J. Labonte 《Solar physics》1991,135(1):163-177
The Mees CCD (MCCD) instrument is an imaging spectroscopy device which uses the 25 cm coronagraph telescope and the 3.0 m Coudé spectrograph at Mees Solar Observatory (MSO) on Haleakala, Maui. The instrument works with resolving power up to R 200 000 with significant throughput from 3934 Å (Caii K) to 10 000 Å. A fast guiding active mirror stabilizes the image during observations. A rapidly writing magnetic tape storage system allows observations to be recorded at 256 kbytes s–1. Currently, the MCCD is used for imaging spectroscopy of solar flares at 6563 Å (H), and velocity measurements of umbral oscillations; future plans include emission line studies of active region coronae, and photospheric studies of solar oscillations. 相似文献
17.
R. G. Giovanelli 《Solar physics》1979,62(2):253-268
A first-order theory is developed for the radiative dissipation of compressive waves in the chromosphere above T
min, where line radiation becomes dominant. The radiative relaxation time, which is the key to dissipation, is shown to depend on wave amplitude, falling greatly for amplitudes 2 km s–1 or more. For a given amplitude, dissipation is greatest for high frequencies, 0.1 s–1, periods 1 min. The observed short-period r.m.s. velocities ~2.4 km s–1 at the D1, level are adequate to provide dissipation balancing chromospheric emission losses.Predictions for the temperature-velocity phase difference and the phase velocity are compatible with observations. 相似文献
18.
N. A. Lipunova 《Astrophysics and Space Science》1985,109(1):57-62
Two sets of observations of the WR-eclipsing binary CV Ser were carried out in 1982 and 1983 in the standard photometric systemUBV. Since 1982, the depth of the atmospheric eclipse has changed and does not show in theV data obtained in 1983. There is significant intrinsic variability (0
.
m
05) in the light curves of CV Ser over both sets of observations and it is suggested that this is due to the changing mass-loss rate from the envelope of the WC8 star on time-scales from days to months. The observed mass-loss rate can change the mass by some 10–5
M
y–1. An orbital inclinationi=72±2° is obtained. 相似文献
19.
In this paper, we present VRc photometric observations of four dwarf cepheids: YZ Boo (P = 0
.
d
104, V = 0
.
m
5), AD CMi (P = 0
.
d
123, V = 0
.
m
5), XX Cyg (P = 0
.
d
135, V = 0
.
m
5), EH Lib (P = 0
.
d
088, V = 0
.
m
7). The light curves were obtained at West Mountain Observatory, Provo, Utah on 14 nights from 1983 through 1986 and contain 589 data points in each of theV andR bands in the Cousin photometric system. A detailed study of these stars, based on the present light curves, will be published separately. 相似文献
20.
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