共查询到20条相似文献,搜索用时 625 毫秒
1.
Examination of the stellar spectrum of this star reveals that it has a composite spectrum. It could be classified as (A7V+G5V). It contains three forbidden [Feii] lines which are of the essential features of η Carinae stars. The spectrum also contains H, Hei, Feii, Mni, Tiii, and other different lines. The K-line seems to be sharp double line while other lines appear single ones which suggest early component may be double. This also seems to be true according to radial velocity measurements. 相似文献
2.
G. A. Gurzadyan 《Astrophysics and Space Science》1983,91(1):157-165
The emission doublet 2800 Mgii of stellar chromospheric origin is always stronger than the emission in the Lα line of hydrogen. At the same time, the ratio of their fluxes,Q=F(Mgii)/F(Lα), varies over a wide range— from 2 up to 20 in stars of one and the same type. Assuming that both emission structures, 2800 Mgii and Lα, are excited in one and the same region of the chromosphere, an attempt is made to represent the ratioQ as a function from one physical parameter only—chromospheric electron temperature. Such an approach explains easily the observed behaviour of the ratioQ in different stars. 相似文献
3.
M. Fracassini L. E. Pasinetti F. Castelli E. Antonello L. Pastori 《Astrophysics and Space Science》1983,97(2):323-335
The peculiar δ Del-variable ? Puppis (F6IIp) has been analysed on nine UV high-resolution spectra in the region of Mgii h- and k-lines. This analysis has shown: (1) The Mgii emission is present during the whole pulsation period and increases with increasing luminosity. Maximum emission fluxes seem to occur at phases 0.96–0.12. (2) The phase shift between intensity maxima of Caii and Mgii chromospheric emissions is probably about 0.26. Moreover, it seems that the phase shift between ? Pup and the Cepheid β Dor is longer for the Mgii emission (~0.44) than for the Caii one (~0.27). (3) Violet-red asymmetries are present in emission components. Moreover, the violet component K1V has always an intensity higher than the red one K1R. (4) The averaged radial velocity (RV) curve obtained from three metallic lines is in agreement with that obtained in the optical region. The RV curves of red emission and absorption components are rather similar to that of the metallic lines. Near the minimum of this RV curve, the chromospheric emissions show an intensity enhancement with a negative phase shift similar to that of light curve (~?30 deg). (5) A model with an emitting extended atmosphere around the star is proposed to explain an emission like feature in the self-reversed absorption component K3 and in K1. 相似文献
4.
Absorption lines of Heii, Hei, Mgii, and other ions have been measured in coudé spectral tracings for 59 slowly and rapidly rotating sourthern O, B and A stars on the Main Sequence. All 668 separate line profiles have been analyzed with a procedure of differential corrections by least-squares to yield the following parameters and their error estimates: half-width, central depth, equivalent width, and shape parameter. The shape parameter includes Voigt profiles and also ‘super-Gaussian’ and ‘super-damping’ profiles. In addition, separately-measured line profiles in each star have been superimposed to yield better composite profiles with smaller errors. In addition, a preliminary value ofv sini is derived for each line by deconvolving it with both the intrinsic and instrumental profiles, and a mean value (including error bar) is derived for each star. The resulting mean values ofv sini are only about 2/3 as large as the earlier results presented by Buscombe (1969). The inadequacies of the traditional procedure are discussed, and plans for using calculated non-LTE intrinsic line profiles including line limb darkening and also effects of rotational distortion, will be outlined. 相似文献
5.
Radiative lifetimes for excited states in La ii, Ce ii, Pr ii, Nd ii, Sm ii, Yb i, Yb ii, and Lu ii have been determined by means of the beam-foil technique or the zero-field level-crossing method. The lifetimes for La, Ce, Pr, Nd, Sm, and Yb are shorter than those computed by summing the transition probabilities of Corliss and Bozman by a factor of up to ~5. The large discrepancies between the abundance of La, Ce, Pr, Nd, and Sm in the solar photosphere and in meteorites are eliminated or greatly reduced if the abundance determinations of the solar photosphere are based upon the gf values of Corliss and Bozman, corrected for by the present lifetimes. 相似文献
6.
R. Tousey 《Astrophysics and Space Science》1975,38(2):327-336
A complex eruptive event took place on January 17, 1974 at approximately 19:20 UT in McMath Hulbert Plage No. 12 686, located near N 06o and behind the west limb. The effects were recorded by the XUV spectroheliograph on Skylab from 19:44 UT to 20:46 UT. An eruptive prominence of spray was observed in Heii 304 Å to reach >1R s. It was also photographed in many emission lines at temperatures reaching 1 MK in Mgix. There were at least four other parts of the eruption, each changing character differently with temperature. These first appeared with Ne.vii at 0.6 MK, and were recorded in lines of ions up to Fexvi at 2.6 MK. 相似文献
7.
We present an investigation of line-of-sight (LOS) velocity oscillations in solar faculae and sunspots. To study the phase relations between chromospheric and photospheric oscillations of the LOS velocity, we measured the time lag of the chromospheric signal relative to the photospheric one for several faculae and sunspots in a set of spectral line pairs. The measured time lags are different for different objects. The mean measured delay between the oscillations in the five-minute band in faculae is 50?s for the Si?i 10?827?Å?–?He?i 10?830?Å pair; for the pair Fe?i 6569?Å?–?Hα 6563?Å the mean delay is 20?s; for the pair Fe?i 4551?Å?–?Ba?ii 4554?Å the mean delay is 7?s; for the pair Si?i 8536?Å?–?Ca?ii 8542?Å the mean delay is 20?s. For the oscillations in the three-minute band in sunspot umbrae the mean delay is 55?s for the Si?i 10?827?Å?–?He?i 10?830?Å pair; for the Fe?i 6569?Å?–?Hα 6563?Å pair it was not possible to determine the delay; for the Fe?i 4551?Å?–?Ba?ii 4554?Å pair the mean delay is 6?s; for the Si?i 8536?Å?–?Ca?ii 8542?Å pair the mean delay is 21?s. Measured delays correspond to the wave propagation speed, which significantly exceeds the generally adopted speed of sound in the photosphere. This raises the question of the origin of these oscillations. The possibility that we deal with slow MHD waves is not ruled out. 相似文献
8.
Paolo Molaro 《Astrophysics and Space Science》2014,354(1):75-81
Absorption systems observed along the line of sights to distant quasars are observed at all redshifts and the full range of the electromagnetic spectrum is needed to recover the variety of transitions of different elements. However, some important elements are found within the Lyman forest and their absorption line profiles need to be analyzed against the presence of possible Ly-α contamination. Considering the cosmological evolution of the number density of hydrogen clouds, the probability to detect uncontaminated metal lines is higher in the UV-Optical region exploited by CUBES. The list of these elements includes some important ones such as D, H2, O?i, N?i, O?vi, Ar?i, P?ii, C?ii, S?ii and B?ii. The determination of some of them in the Damped Ly-α galaxies and their astronomical interest are briefly discussed. 相似文献
9.
C. De Jager H. J. G. L. M. Lamers K. A. Van Der Hucht 《Astrophysics and Space Science》1975,38(2):313-325
A progress report is given of investigations related to observations of stellar spectra obtained with the ultraviolet stellar spectrophotometer S59 aboard the ESRO TD-1A satellite. We describe first the processing of the observations: intensity and wavelength calibration, identification of lines, classification of spectra. Thereafter some important groups of lines are dealt with: non-LTE computation of the Mgii lines are presented: apart from the peculiar emission line and shell stars they compare well with the observations; intensity ratios, of Feii and Feiii lines are an important temperature classification criterion. Interstellar UV lines indicate large deficiencies of some metals, as compared to solar values. A new ultraviolet continuous extinction curve is determined. We discuss the strong outstreaming motions observed in α Cygni, and the consequent mass loss of this star (< 3 × 10?10 \(\mathfrak{M}_ \odot \) yr?1and finally we describe the composite spectrum of the (WC8+09I) bnary γ2 Velorum; the ultraviolet continuous spectrum of the WC star is about one magnitude brighter than any theory predicts. 相似文献
10.
It is shown that emission lines, first of all the ultraviolet resonance doublet 2800 Mgii, can be used to decipher the internal dynamic structure of QSOs and active galactic nuclei. The electron temperatures of the emission regions of these objects are determined. A hypothesis is proposed explaining the observed broad profiles of the 2800 Mgii line as a summary effect of emission clouds with a Maxwellian velocity distribution. The main physical parameters of emission clouds in QSOs are obtained. A mechanism of formation of emission clouds is suggested: namely, tidal disruption of stars near to a massive compact object. 相似文献
11.
V. Krishan 《Solar physics》1983,88(1-2):155-161
From the statistical treatment of magnetohydrodynamically turbulent plasma, a steady-state density, temperature and magnetic field structure is derived for a coronal loop emitting in UV and EUV range. Spatial variation of line flux is presented for the lines C ii, C iii, O iv, O vi, Ne vii, and Mgx. It is found that the hotter lines which are emitted near the surface of the loop have larger spatial extents compared to the lines originating in the cool core of the loop, in agreement with the observations. 相似文献
12.
A quiescent prominence observed above the north-west limb on November 20, 1980, is analyzed using data obtained with the Ultraviolet Spectrometer and Polarimeter (UVSP) on the Solar Maximum Mission (SMM). The spectral data include the lines 1215 Å of Hi, 1401 Å of Oiv, 1402 Å of Siiv, 1548 Å of Civ, 1640 Å of Hei, and 1655 Å of Ci. From an analysis of these lines and their emission patterns we deduce physical characteristics of the prominence plasma, and suggest in particular that the prominence consisted of flux tubes at various temperatures. In the hotter parts of the plasma the number density reached values of about 3 × 1011 cm#X2212;3. 相似文献
13.
Ángeles I. Díaz Guillermo F. Hägele Elena Terlevich Roberto Terlevich 《Astrophysics and Space Science》2009,324(2-4):209-214
A study of circumnuclear star-forming regions (CNSFRs) in several early-type spirals has been carried out in order to investigate their main properties: stellar and gas kinematics, dynamical masses, ionising stellar masses, chemical abundances and other properties of the ionised gas. Both high resolution (R~20,000) and moderate resolution (R~5000) have been used. In some cases, these regions (about 100–150 pc in size) are composed of several individual star clusters with sizes between 1.5 and 4.9 pc, estimated from Hubble Space Telescope images. Stellar and gas velocity dispersions are found to differ by about 20 to 30 km?s?1, with the Hβ emission lines being narrower than both the stellar lines and the [Oiii]λ5007 Å lines. The twice ionised oxygen, on the other hand, shows velocity dispersions comparable to those of stars. We have applied the virial theorem to estimate dynamical masses of the clusters, assuming that the systems are gravitationally bounded and spherically symmetric, and using previously measured sizes. The measured values of the stellar velocity dispersions yield dynamical masses of the order of 107 to 108 M⊙ for the full CNSFRs. We obtain oxygen abundances which are comparable to those found in high-metallicity disc Hii regions from direct measurements of electron temperatures and consistent with solar values within the errors. The region with the highest oxygen abundance is R3+R4 in NGC3504, 12+log(O/H)=8.85, about 1.5 times solar. The derived N/O ratios are, on average, larger than those found in high-metallicity disc Hii regions, and they do not seem to follow the trend of N/O vs. O/H which marks the secondary behaviour of nitrogen. On the other hand, the S/O ratios span a very narrow range—between 0.6 and 0.8 times solar. Compared to high-metallicity disc Hii regions, CNSFRs show values of the O23 and the N2 parameters whose distributions are shifted to lower and higher values, respectively. Hence, even though their derived oxygen and sulphur abundances are similar, higher values would in principle be obtained for the CNSFRs if pure empirical methods were used to estimate abundances. CNSFRs also exhibit lower ionisation parameters than their disc counterparts, as derived from [Sii]/[Siii]. Their ionisation structure also seems to be different, with CNSFRs showing radiation-field properties more similar to Hii galaxies than to disc high-metallicity Hii regions. 相似文献
14.
Considering the host galaxy contribution, a spectral decomposition method is used to reanalyzed the archive data of optical spectra for a narrow line Seyfert 1 galaxy, NGC 4051. The light curves of the continuum f λ (5100 Å), and Hβ, He ii, Fe ii emission lines are given. We find strong flux correlations between line emissions of Hβ, He ii, Fe ii and the continuum f λ (5100 Å). These low-ionization lines (Hβ, Fe ii, He ii) have “inverse” intrinsic Baldwin effects. Using the methods of the cross-correlation function and the Monte Carlo simulation, we find the time delays, with respect to the continuum, are $3.45^{+12.0}_{-0.5}~\mbox{days}$ with the probability of 34 % for the intermediate component of Hβ, $6.45^{+13.0}_{-1.0}~\mbox{days}$ with the probability of 65 % for the intermediate component of He ii. From these intermediate components of Hβ and He ii, the calculated central black hole masses are $0.86^{+4.35}_{-0.33}\times 10^{6}$ and $0.82^{+3.12}_{-0.45}\times 10^{6}~M_{\odot }$ . We also find that the time delays for Fe ii are $9.7^{+3.0}_{-5.0}~\mbox{days}$ with the probability of 36 %, $8.45^{+1.0}_{-2.0}~\mbox{days}$ with the probability of 18 % for the total epochs and “subset 1” data, respectively. It seems that the Fe ii emission region is outside of the Hβ emission region. 相似文献
15.
Rosanna Faraggiana Karel A. van der Hucht Marijke Burger 《Astrophysics and Space Science》1975,38(1):243-249
Near-ultraviolet spectra, obtained with the ESRO TD-1A/S59 experiment, of the four Mn stars β Tau, γ Crv, α And, and μ Lep and six normal stars are compared. The normal stars show good agreement with synthetic spectra. The Mn stars have spectra which become hotter at shorter wavelengths. They also show strong Mnii lines and weak Mgii lines. A time-variation for Tiii λ 2828 was noted in γ Crv and α And. 相似文献
16.
Kerstin Fredga 《Solar physics》1969,9(2):358-371
A rocket-borne spectroheliograph designed to take monochromatic pictures of the sun in the Mgii line at 2795.5 Å was successfully launched from White Sands Missile Range on May 20, 1968. A double ?olc birefringent filter with a spectral bandpass of 2.1 Å was used to select the proper wavelength. Pinhole photographs in the soft X-ray region were also secured in the same flight. The Mgii and X-ray photographs are compared with simultaneous Caii and Hα spectroheliograms, radiomaps at 9.1 cm and 3.3 cm, a Fraunhofer map and a magnetogram and some preliminary results are discussed. 相似文献
17.
We present grids of stellar models and their associated oscillation frequencies that have been used by the CoRoT Seismology Working Group during the scientific preparation of the CoRoT mission. The stellar models have been calculated with the CESAM stellar internal structure and evolution code while the oscillation frequencies have been obtained from the CESAM models by means of the ADIPLS adiabatic oscillation programme. The grids cover a range of masses, chemical compositions and evolutionary stages corresponding to those of the CoRoT primary targets. The stellar models and oscillation frequencies are available on line through the Evolution and Seismic Tools Activity (ESTA) web site. 相似文献
18.
N. M. Firstova 《Solar physics》1984,90(2):269-279
Using the Baranger-Mozer method, we explore the possibility of diagnosing the flare plasma of forbidden Hei lines, that permits the determination of the plasma oscillation frequency and noise level. Examination of the Hei lines observed in solar flare has led us to conclude that:
- the appearance of satellites of forbidden components in the flares spectrum, due to turbulent electric fields, is the most probable for Hei 3819.606 Å lines;
- the Baranger-Mozer method is more sensitive to the high-frequency component of turbulent fields than to the low-frequency ones;
- the upper limit of the turbulent oscillation level in flares is evaluated.
19.
Renato Falomo 《Astrophysics and Space Science》1983,91(1):63-69
Reticon spectroscopic observations of the yellow symbiotic star AG Draconis are reported. Small rapid (15–30 min) changes in the intensities of the Hei λ5015 Å and Hei λ6678 Å singlet lines, and of the Hγ line are observed. The first observational evidence of presence of the unidentified band at 7088 Å in this star is also reported. 相似文献
20.
At a spatial resolution of 1″ and with spectral passbands of 0.25–0.47 Å, the chromospheric fine structure was studied with an array of 512 silicon photodiodes. The high quantum efficiency of the diodes in the near infrared allowed low noise spectroheliograms to be constructed from observations in the lines of H i, Ca ii, and He i. Magnetograms of the underlying photosphere were obtained simultaneously. Tachograms in the He 10830 Å line revealed 1″ points and elongated features that are interpreted as spicules seen against the disk. Active regions and filaments at 10830 are compared with Hα and Ca ii (8542 Å) features. Filament contrast increases with the proximity of bright plage. Twelve subflares were studied and in eight cases, 3–5″ kernels of He I emission appeared over small, growing pores or over 5″ patches of magnetic field emerging through the photosphere. All the subflares showed 10830 emission, contrary to established belief that the 10830 line goes into emission only in the largest flares. All the subflares included at least one emission kernel over regions where the photospheric magnetic field, as seen with a resolution of 1–2″, broke down into a mosaic of both polarities with 3–5″ diam. elements. 相似文献