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1.
IUE ultraviolet spectral recording for a low excitating planetary nebula NGC 6369 is obtained. The very strong doublet 2800 Mgii in emission as well as not less strong absorption line 2852 Mgi are discovered in the spectrum of this nebula. It is shown that the resonance line 2852 Mgi may originate only in a neutral envelope, around the nebula, consisting of neutral hydrogen, neutral magnesium, and dust particles (Hi+Mgi). The importance of this absorption line as a powerful indicator of the discovery of neutral envelopes around the planetary nebulae is outlined.The possibility of the existence of one more envelope—transition zone—immediately contacting with the bright that is ionized part of nebula (Hii+Mgii) is also shown. The transition zone consists of neutral hydrogen, ionized magnesium, and dust particles (Hi+Mgii), main parameters of this zone are also obtained (Table IV).The temperature of the central star of this nebula is obtained for the first time:T
*=48000 K. Continuous background in the interval 2600–3000 Å is identified with Balmer continuum with electron temperatureT
e
=12500 K. 相似文献
2.
We have obtained IUE ultraviolet spectra of the low-excitation planetary nebula CN 3-1. The recordings show the well-known doublet 2800 MgII and resonance line 2852 MgI as strong absorption lines. We show that these lines cannot be of interstellar origin and that they may be formed in two envelopes surrounding the main nebula: in the transition zone (doublet 2800 MgII) and in the neutral envelope (line 2852 MgI). These envelopes possess an important property: they contain dust particles, and even a moderate amount of such particles may influence the strength of the absorption lines of MgII and MgI.The emission line 4686 HeII has no relation to the nebula CN 3-1 and belongs to its nucleus, a star of type WR. It is very probable that the nucleus of this nebula is a binary system with a WR component (T
*=50 000 K), exciting the helium lines, and a star of B0 or B2 type (T
*=26 000 K) exciting the nebular linesN
1+N
2 [OIII], 3727 [OII], hydrogen lines, etc. 相似文献
3.
We present the results of an analysis of the winds of two WC10 central stars of planetary nebulae, CPD-56°8032 and He 2-113. These two stars have remarkably similar spectra, although the former exhibits somewhat broader emission line widths. High resolution spectra (up to R=50 000) were obtained in May 1993 for both objects at the 3.9 m AAT, using the UCL Echelle Spectrograph. The fluxes in individual Cii auto-ionising multiplet components, many of which were blended, were derived. Lines originating from auto-ionising resonance states situated in the C2+ continuum are very sensitive to the electron temperature, since the population of the these levels is close to LTE. The measured widths and profile shapes of these transitions are presented and are in excellent agreement with those predicted on the basis of their calculated auto-ionising lifetimes. The wind electron temperature is derived for both stars from the ratio of the fluxes in four such transitions (T
e
=18 500 K±1 500 K for CPD-56° 8032 andT
e
=13 600 K±800 K for He 2-113). Optical depth effects are investigated using normal recombination lines to obtain an independent wind electron temperature estimate in excellent agreement with the dielectronic line analysis. 相似文献
4.
A ring of compact radio continuum sources was found atl=24°.6b=0°.0, which we call the Scutum ring. Radio continuum,Hi line, and CO line observations are suggested that it is a star-forming region triggered by an expanding diffuseHii region.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.NRO, a branch of the Tokyo Astronomical Observatory, University of Tokyo, is a cosmic radio observing facility open for outside users. 相似文献
5.
Miriam Peña Manuel Peimbert Silvia Torres-Peimbert Maria Teresa Ruiz Jose Maza 《Astrophysics and Space Science》1996,238(1):55-58
The recent evolution of the central star of the planetary nebula LMC-N66 is presented. Before 1987, it showed a weak continuum with aT
eff120 000 K andL
bol25 000L
and in a few years it developed strong WR features (P Cygni line profiles in N v at 124.0 nm and C IV at 155.0 nm, wide Heii emission, etc.) typical of a WN 4.5. Additionally the stellar continuum increased by a large factor and the absolute visual magnitude of the star changed from + 1.24 in 1987 to–2.57 in January, 1995. The WR features and enhanced continuum, evidencing a powerful mass-loss event remained with small variations for more than 5 years. Recent ultraviolet and optical data shows that the mass-loss seems to have diminished abruptly in the last three months. 相似文献
6.
S. Mizuno 《Astrophysics and Space Science》1982,87(1-2):121-148
The surface photometry of S254–S257 has been carried out by means of a wide range image processing technique in the reduction system. The photographic plates in the H+[NII] andV-bands are taken with the Schmidt telescope. Especially, we have obtained the calibrated map of theHii region, superposing two or more plates with different exposure times, and removing the star images. Three kinds of calibrated maps of theHii regions are drawn: (1)E-map in the (H+[NII]+continuum) (2)V-map in the continuum atV-band, (3)(E-V)-map in the (H+[NII]) line emission. The intensity profiles across the nebular centers were also obtained. Based on calibrated maps, the morphological structure and mass distribution of S255 and S257 are discussed. The location of observed nebulae on the (m
H–m
v) diagram, wherem
H andm
v denote the surface brightness, expressed in the magnitude per square arcmin, is shown together with that of some other nebulae. Some arguements on the age sequence of observedHii regions are presented. 相似文献
7.
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
8.
M. V. F. Copetti 《Astrophysics and Space Science》1989,156(1-2):103-106
Integrated photoelectric measurements of the equivalent widthW
H, the [Oiii]/H ratio and the H emission line flux were obtained for 30Hii regions in the SMC. Physical properties of theHii regions and their ionizing stellar associations were derived. Some aspects of the recent star formation in the SMC and the evolution ofHii regions are discussed. 相似文献
9.
New electron excitation rates for O vii calculated by Tayal and Kingston using the R-matrix method are used to determine theoretical emission line strengths. Values of the electron density sensitive ratio R (forbidden line to intercombination line) are found to be very similar to those deduced by other authors. However the temperature sensitive ratios G (intercombination plus forbidden lines to resonance line) are approximately 20% lower than the best previous estimates. The observed value of G for solar active regions (G = 1.0 ± 0.1) predicts an electron temperature in the range 1.1 × 106 K < T
e
< 1.8 × 106 K, which overlaps that of maximum O vii emissivity, T
M
= 1.8 × 106 K. In addition, the theoretical G versus T
e
curve is in excellent agreement with that observed for a Tokamak plasma. 相似文献
10.
V. P. Merezhin 《Astrophysics and Space Science》1990,174(2):181-193
The observational data analysis indicates that the star is enveloped into a nebula considerably stretched along the equatorial plane. Vega is a star with B9.5IV-V characteristics withT
e
=10.105±230 K andR=2.69±0.25R. The cover deforms energy distribution in Vega spectrum. As a result, the energy from with distribution corresponding to an A0V star is imitated in the direction towards the observer. 相似文献
11.
R-matrix calculations of electron impact excitation rates for transitions in Si iii are used to derive the electron-density-sensitive emission line ratios R
1 = I(1113.2 Å)/I(1206.3 Å), R
2 = I(1298.9 Å)/I(1206.3 Å), and R
3 = I(1296.7 Å)/I(1206.3 Å). A comparison of these with observational data for several solar features obtained with the Harvard S-055 spectrometer on board Skylab reveals that theory and experiment are compatible if the electron temperature of the Si iii emitting region of the solar atmosphere is log T
e
= 4.5, but not if log T
e
= 4.7. The implication of the choice of a lower temperature on the electron energy distribution function is also briefly discussed. 相似文献
12.
V. V. Krymkin 《Astrophysics and Space Science》1978,58(2):347-352
Observations of the ionized hydrogen region NGC 1499 have been carried out with the radio telescope UTR-2 at frequencies 12.6, 14.7, 16.7, 20 and 25 MHz. The half-power resolution of the instrument to zenith is 28×34 at 25 MHz. The average volume density of the non-thermal radio emission between the Sun and the nebula (1.75×10–40 W m–3 Hz–1 ster–1 at 25 MHz), the electron temperature of the HII nebula (T
e
=4400 K), the measure of emission (ME=1500 cm–6 pc) and other parameters have been obtained. Maps of brightness distribution over the source are presented for each observation frequency. The results are compared with previously obtained data. 相似文献
13.
In the preceding paper by Vengeret al. (1984) the results of observations of neutral gas in the vicinity of some galacticHii regions were considered; and it was demonstrated that 17 of the regions observed are surrounded by expandingHi envelopes. This paper describes a model of interaction between theHii regions and the surrounding interstellar medium constructed on the basis of the said results. It is assumed that the main dynamic factor in the envelope formation mechanism is the total stellar wind from the stars which ionze theHii regions. The employment of the observations of the line at =21 cm, of the radio continuum and IR dust continuum made it possible to determine the differential mass spectra of the stars exciting theHii zones and calculate some characteristics of the stellar population. The mass spectrum index of the objects considered turned out to be much higher than that for the mass spectra of background stars and scattered clusters of stars. 相似文献
14.
A variety of new optical observations have been made over the bright core of the supermassiveHii region 30 Doradus and the ionized filamentary material surrounding this object. In addition, a more detailed analysis of previously published interstellar absorption andHi emission profiles has been undertaken.The velocity and density structure of this complex region is discussed and the new results analysed here shown to be compatible to the model of 30 Doradus presented in Cantóet al. (1980) and Meaburn (1980). 相似文献
15.
In this paper we discuss the ionization equilibrium of hydrogen and helium in a nebula with an arbitrary gas density distribution. If we consider the spectral characteristics of hot stars, a power law is found to provide a good approximation to the Lyman continuum spectrum for stars withT eff≤100 000 K. With this simplification the ionization equilibrium equation is analytically solved first for a pure hydrogen nebula, then for the general case of a nebula containing H, He, and heavy elements. A simple and quite general formula for the determination of the size and the emission of the He+ zone is obtained. Finally, the ionization equilibrium He++?He+ is considered. This problem can be decoupled from that of the ionization of H0 and He0 if the stellar spectrum is steeper thanv ?0.9 or, equivalently, if the star effective temperature is lower than 200 000 K. Within this limit, which surely includes all classicalHii regions and the low-medium excitation planetary nebulae, an analytical solution of the problem can be used. 相似文献
16.
Takara Nishikawa 《Solar physics》1984,93(1):37-51
The weakening of EUV line emission due to continuum absorptions of neutral hydrogen and neutral helium is investigated to examine its wavelength-dependence. After convolving the intensities predicted from multilevel calculations over an instrumental profile, we found a systematic, linear weakening for lines shortward of 912 Å, which can be attributed to Lyman continuum absorption in the cool chromospheric cloud. The degree of the weakening at the quiet Sun seems to be constant in the temperature range of 4.3 < log T < 5.4. We also find that the lines shortward of 504 Å are somewhat weakened by He i continuum absorption. From the comparison of both weakenings the temperature of the absorber is estimated to be rather low (T
e 7 × 103 K). 相似文献
17.
HD 147010, which is in the reflection nebula vd B 102, has been found to be a hot Ap silicon star rather than a normal A supergiant.
From theUBV and JHK photometry of the star, colour excessE(B - V) of 0.29 and the ratio of total-to-selective absorptionR of 4.3 have been obtained. The high value ofR implies bigger grain size and also confirms the association of the star with the nebula. The dereddened colours of the star
can be fitted to a theoretical energy distribution with Teff = 13000 ± 500 K and logg = 3.6 ± 0.2. HD 147010 has also been found to be a spectrum variable; in particular, lines of Cr II show large intensity
variations. 相似文献
18.
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
19.
Profiles of the K line of Caii are computed for a two component solar chromosphere, chosen to simulate with a simple geometry the chromospheric supergranular network. Each component rises above the BCA photosphere, the boundary component representing the bright network with a sharp temperature rise and the cell component representing the darker region with an extended temperature minimum. Theoretical intensity profiles of the Can K core, calculated as weighted averages over the projected areas of the components, are produced for = 0.6 and 0.3. The line source function and the optical depth are obtained from a self-consistent treatment of the steady state and radiative transfer equations, with complete redistribution assumed for scattering in the line. The atomic model consists of two bound levels and a continuum. It is found that a 4600 K minimum can lead to the successful theoretical prediction of the observed limb darkening and 4300 K radiation temperature of the K1 feature only when very large values of turbulent velocity are assumed to exist in the cell region.Publications of the Goethe Link Observatory, Indiana University, No. 95. 相似文献
20.
Nine of the cataloguedHii regions in the southern hemisphere have been selected for correlation with neutral hydrogen observed at the 21 cm line.The radiotelescope used for theHi line observations was the 30 m Carnegie telescope of the Instituto Argentino de Radioastronomía and the 56 channel, 10 KHz bandwidth receiver.The observational results are analyzed for eachHii region. They are compared with previous optical and radio results.For three of the nine observed regions it has been possible to find neutral hydrogen in absorption with similar velocities. In three cases absorption has been found but no component at theHii region velocity is seen. Finally in three cases, it has not been possible to find any absorption at all.Member of the Carrera del Investigador Científico del Cosejo Nacional de Investigaciones Científicas y Técnicas. 相似文献