首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
The transformation of the line and molecular spectra of R CrB from absorption to emission at the 1985 minimum is traced from spectroscopic observations, and it is concluded for the first time, from a comparison with light curves and color indices, that the rapid variation of the color index U – B by –0m.6 during fading is due exclusively to this transformation. The transformation of the spectrum can result in an increase in the star's brightness in the UBV photometric bands by about 1m.4, 0m.75, and up to 0m.75, respectively. This removes one of the main objections to using the concept of a homogeneous spherical shell to interpret the R Coronae Borealis phenomenon. High-resolution spectroscopic observations of SV Sge, a star with variability of the R Coronae Borealis type, showed the presence of an intense circumstellar component in Na I D lines with a violet shift corresponding to 240 km/sec, which is unrelated to visible brightness minima. It is suggested that a stream of matter with such a velocity through the star's vicinity is the cause of the excitation not only of the broad emission features observed during brightness minima upon fading of the photospheric emission but also of the narrow ones. Assuming that a brightness minimum is associated with the temporary formation of another spherical screening shell, some characteristics of the permanent shell are determined. Its optical depth and geometrical thickness are 0.2-0.7 and at least 0.4 of its radius, respectively.  相似文献   

2.
A model of the R CrB star chromosphere is calculated on the basis of the observed profiles of the Ca II H and K lines and IR triplet and D lines of Na I and H-alpha. The calculated profiles of Ca II H and K lines and IR triplet and H-alpha are in good agreement with the observed ones both for an undisturbed state and for the light minimum. The line profiles for the light minimum are calculated under the assumption that the minimum is attributed to obscuring of the star disc with a dust cloud. In this case, the chromosphere is not hydrostatic since the column density at the chromosphere base is two orders of magnitude higher as compared to that in a hydrostatic model. The model proposed is more extended, less dense at the chromosphere base, and denser in the upper chromosphere. The extension of the calculated chromosphere is about 3 star radii. The density in the chromosphere is 108–1010 atoms per 1 cm3 and the temperature is 5000–7000 K. Agreement of the calculated and observed profiles of Na I D absorption lines is possible if we assume that, around the star, there is a cold envelope containing Na I atoms which expands with a velocity of about 30 km/s. This envelope is beyond the chromosphere, but near enough for the star and the envelope to be observed as a single whole. The optical thickness of the envelope in the Na I D2 line is 1.8. At the brightness minimum, this envelope illuminated with the star light yields additional emission attributed to resonant scattering in the Na I D lines.  相似文献   

3.
Iye  M.  Ulrich  M. -H. 《Astrophysics and Space Science》1986,118(1-2):523-528
Preliminary results of spectroscopic studies of selected Seyfert galaxies employing a new Cassegrain echelle spectrograph completed at ESO are presented. Subjects reported are the asymmetric profiles of narrow emission lines, spatial variation of narrow emission line profiles, and the interstellar absorption lines.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.  相似文献   

4.
Spectral observations of the eclipsing binary RY Sct during 2005 and 2009 on the 2.6-m telescope at the Byurakan Observatory are reported. Although RY Sct requires further, more detailed study, the present limited observations reveal a number of important aspects of this star. The maxima of the equivalent widths are observed close to the primary minimum, while their minima are detected at the brightness maximum, where the spectral lines have very narrow profiles. Emission in the HeI λ6678? line was seen throughout the observation period, but transforms into weak absorption halfway between the secondary minimum and the maximum. The observed P-Cyg type changes in the profile of some lines indicates a variable outflow of mass from the star. Estimates of the average velocity based on the blue components of the absorption lines yield roughly 400 km/s. The main observational characteristics of RY Sct are closely related to its orbital period. In all likelihood, its complicated spectrum and features are at least partially caused by intense, variable outflows of matter.  相似文献   

5.
A high resolution profile of the solar Oi 1304.9 Å line has been measured from rocket spectrograms. The profile is nearly flat-topped, showing only a slight solar reversal after instrument effects and absorption due to atomic oxygen in the earth's atmosphere have been allowed for. A theoretical analysis of this line, under the assumption of non-LTE conditions and a homogeneous, spherically symmetric chromosphere, predicts a rather deep solar reversal. The theoretical profile may be made consistent with the observed profile if mass motion is present in the chromospheric region where the line is formed. A Gaussian distribution of up and down velocities with a root mean square velocity of about 7 km/sec gives best agreement between the predicted and observed profile. This result is consistent with the conclusion made from a study of high resolution profiles of solar lines in the visible spectrum that mass vertical velocities increase with height above the photosphere.  相似文献   

6.
In this paper we study the main features of the far UV spectrum of the binary star AX Mon, observed with the IUE satellite at phase 0.568.Ions indicating a large range of ionization stages, going fromCi,Oi,Ni toSiv,Civ,Nv are present.The spectrum is dominated by shell absorption lines of Feii, Feiii, Siiii,Cii, Alii, Mgii and Niii.Two satellite components are clearly indicated in all these lines except for Niii which presents only one. Their mean velocities are +10±5 km s–1, –75±10 km s–1, and –260±15 km s–1.Red emission wings are observed in the Mgii resonant doublet at 2800 Å, which shows a P Cygni profile. Each of the absorption lines of the Mgii doublet is formed by a narrow component, which is blended with the Mgii interstellar line and a broad component, which shows a complex structure.Broad and asymmetrical profiles are observed for the Siiv,Civ, andNv resonance lines with blue edge velocities about –700±30 km s–1.  相似文献   

7.
Brynildsen  N.  Brekke  P.  Fredvik  T.  Haugan  S. V. H.  Kjeldseth-Moe  O.  Maltby  P.  Harrison  R. A.  Wilhelm  K. 《Solar physics》1998,181(1):23-50
We present high spatial and spectral resolution observations of one active and one quiet-Sun region, obtained with CDS and SUMER on SOHO. The connections between the line profile parameters are studied and a systematic wavelength shift towards the red with increasing peak line intensity (line broadening) is detected. The large scatter in the data calls for another approach. We apply conditional probability analysis to a series of EUV emission lines and find significant correlations between line profile parameters. For a given interval in wavelength shift we find that: (1) line profiles with large intensities (line widths) and red shifts above the average constitute an increasing fraction of the profiles as the relative wavelength shift increases, (2) line profiles with large intensities (line widths) and blue shifts compared to the average, on the other hand, constitute a decreasing fraction of the profiles as the relative wavelength shift increases. These results extend the findings of an earlier quiet-Sun study from one to several emission lines and expand the validity to include the active region. Interestingly, the active region observations show correlations between peak line intensity and wavelength shift in the coronal lines.The tendency for red-shifted profiles to be more intense than blue-shifted profiles will shift line profiles derived by integrating along the slit towards the red. From the present observations we are not able to determine the fraction of the net red shift that emerges from this correlation. We suggest that the same mechanism is responsible both for the correlation between the line profile parameters and for the differential red shift between the transition region and chromospheric emission lines.  相似文献   

8.
Optical spectra taken in 1997–2008 are used to analyze the spectral peculiarities and velocity field in the atmosphere of the peculiar supergiant 3 Pup. The profiles of strong Fe II lines and of the lines of other iron-group ions have a specific shape: the wings are raised by emissions, whereas the core is sharpened by a depression. The latter feature becomes more pronounced with the increasing line strength, and the increasing wavelength. Line profiles are variable: the magnitude and sign of the absorption asymmetry, and the blue-to-red emission intensity ratios vary from one spectrum to another. The temporal Vr variations are minimal for the forbidden emissions and sharp shell cores of the absorption features of FeII(42), and other strong lines of iron-group ions. The average velocity for the above lines can be adopted as the systemic velocity: Vsys = 28.5 ± 0.5 km/s. The weakest photospheric absorptions and photospheric MgII, Si II absorptions exhibit well-defined day-to-day velocity variations of up to 7 km/s. Quantitative spectral classification yields the spectral type of A2.7±0.3 Ib. The equivalent widths and profiles of Hδ and Hγ, and the equivalent width of the OI 7774 Å triplet yield an absolute magnitude estimate of Mv=?5.5m ± 0.3m, implying the heliocentric distance of 0.7 kpc.  相似文献   

9.
We analyze the peculiarities of the optical spectra of luminous stars with circumstellar gas and dust envelopes: the time variability of the absorption-emission profiles of the Hα line, the presence of stationary emission and absorption molecular bands, multicomponent absorption-emission profiles of the Na I D doublet lines. We show that the peculiarities of the line profiles (the presence of an emission component in the Na I D doublet lines, the specific type of the molecular features, the asymmetry and splitting of the profiles of strong absorption features with low excitation potential of the low level) can be associated with the kinematic and chemical properties of the envelope and its morphological type.  相似文献   

10.
We present the results of our observations of the maser radio emission source G188.946+0.886 in hydroxyl (OH) molecular lines with the radio telescope of the Nançay Observatory (France) and in the H2O line at λ = 1.35 cm with the RT-22 radio telescope at the Pushchino Observatory (Russia). An emission feature in the 1720-MHz satellite line of the OH ground state has been detected for the first time. The radial velocity of the feature, V LSR = 3.6 km s?1, has a “blue” shift relative to the range of emission velocities in the main 1665- and 1667-MHz OH lines, which is 8–11 km s?1. This suggests a probable connection of the observed feature in the 1720-MHz line with the “blue” wing of the bipolar outflow observed in this region in the CO line. We have estimated the magnetic field strength for three features (0.90 and 0.8 mG for 1665 MHz and 0.25 mG for 1720 MHz) from the Zeeman splitting in the 1665- and 1720-MHz lines. No emission and (or) absorption has been detected in the other 1612-MHz satellite OH line. Three cycles of H2O maser activity have been revealed. The variability is quasi-periodic in pattern. There is a general tendency for the maser activity to decrease. Some clusters of H2O maser spots can form organized structures, for example, chains and other forms.  相似文献   

11.
Repeated spectroscopic observations made with the 6-m telescope of SAO RAS yielded new data on the radial-velocity variability of the anomalous yellow supergiant QY Sge. The strongest and most peculiar feature in its spectrum is the complex profile of NaI D lines, which contains a narrow and a very wide emission components. The wide emission component can be seen to extend from ?170 to +120 km/s, and at its central part it is cut by an absorption feature, which, in turn, is split into two subcomponents by a narrow (16 km/s at r=2.5) emission peak. An analysis of all the Vr values leads us to adopt for the star a systemic velocity of Vr=?21.1 km/s, which corresponds to the position of the narrow emission component of NaI. The locations of emission-line features of NaI D lines are invariable, which point to their formation in regions that are external to the supergiant’s photosphere. Differential line shifts of about 10 km/s are revealed. Emission in the Hα line is weaker than in NaI D lines, it fills the photospheric absorption almost completely. The absorption lines in the spectrum of QY Sge have a substantial width of FWHM ≈ 45 km/s. The method of model atmospheres is used to determine the following parameters: the effective temperature T eff =6250±150 K, surface gravity l g g=2.0±0.2, and microturbulence velocity ξ t =4.5±0.5 km/s. The chemical composition of the atmosphere differs only slightly from the solar composition: the metallicity of the star is found to be somewhat higher than the solar metallicity with an average overabundance of iron-peak elements of [Met/H]⊙=+0.20. The star is found to be slightly overabundant in carbon and nitrogen, [C/Fe]=+0.25, [N/Fe]=+0.27. The α-process elements Mg, Si, and Ca are slightly overabundant, on the average by [α/H]⊙=+0.12, and sulfur overabundance is higher, [S/α]=+0.29. The strong overabundance of sodium, [Na/Fe]=+0.75, is likely to be due to the dredge-up of the matter processed in the NeNa cycle. Heavy elements of the s-process are underabundant relative to the Sun. On the whole, the observed properties of QY Sge do not give grounds for including this star into the group of RCrB or RVTau-type objects.  相似文献   

12.
Two outbursts and a minimum phase of the dwarf nova CN Orionis have been observed spectroscopically. One outburst was covered almost completely. The outburst spectra show periodic variations of the absorption lines which are interpreted with the formation of an elliptic disc during outburst stage. During decline from outburst a narrow emission line appears in the core of the broad H absorption line. The balmer decrement in the outburst phase is much steeper than in the minimum phase. This implies that during the outburst the emission line region is located more outward in the disk. The semi amplitude of the radial velocity curve was determined to K1=152 km/s±10 km/s. Using the photometric orbital period and an assumption about the inclination angle the approximate system parameters could be derived.Based on observations colleted at the European Southern Observatory, La Silla, Chile and at Mount Stromlo Observatory, Canberra, Australia.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.  相似文献   

13.
Analyses of broad moustache profiles of Balmer lines and Ca ii H and K lines are performed based upon our spectroscopic observation under good seeing conditions. Hα emission profiles are found to consist of three components, i.e., a central absorption, a Gaussian core and a power-law wing. Each of them has a different Doppler shift from others. From the data of Doppler shifts, mass motions with velocity of about 6 km s?1 are found to be present in chromospheric levels of moustache atmospheres. Computations of Hα emission profiles radiated from a variety of model atmospheres are made. Comparison of computed profiles with the observed ones leads us to the conclusion that a broad Hα profile is due to a formation of heated (ΔT = 1500 K) and condensed (?/? 0 = 5) chromospheric layers relative to the normal.  相似文献   

14.
We describe observations with a new magnetograph capable of recording the whole profile of emission lines in prominences. Two recordings are used simultaneously to study the Zeeman effect in circularly polarized light. The spectral scan is produced by the action of piezo ceramics of a Perot-Fabry inter ferometer combined with a narrow band interference filter.The instrument is calibrated using 100% circularly polarized light and an emission line produced in Laboratory conditions in a simulated longitudinal magnetic field. The magnetograph was attached to the large coronagraph (Ø 53 cm) of Kislovodsk to give a series of measurements of the H line of several quiescent and active prominences. The observed values of the longitudinal component of the magnetic field are between: -25 G + 13 G with a noise level at ±2 G for a corresponding resolution of 8 arc sec.Effects produced by the instrumental polarization are discussed.S.A.S. Institut d'Astrophysique du CNRS, 98bis, Bd Arago, F 75014 Paris.  相似文献   

15.
Innes  D. E.  Curdt  W.  Dwivedi  B. N.  Wilhelm  K. 《Solar physics》1998,181(1):103-112
The Solar Ultraviolet Measurements of Emitted Radiation instrument (SUMER) observations show high Doppler shifts and temporal variations in profiles of ultraviolet lines from low temperature gas in the corona above the active region NOAA 7974. The profiles indicate 100 km s-1 flows coming from an almost stationary source that appears bright in the lines of N III and Si III. The variations in line-of-sight velocities and intensities suggest small knots of cooling plasma emanating from a small region high in the corona. A few arc sec sunward of the region where the cool flows are seen is an elongated region of enhanced higher temperature, low velocity Ne VI and Mg VI line emission.  相似文献   

16.
Fifty-three spectrograms in the optical region (3700–7300 Å) with the spectral resolution ～8 Å have been obtained for the Seyfert nucleus of the galaxy NGC 3227 with the 6-m telescope on January 1977, while the nucleus was in the historically important epoch of its extreme maximum brightness. Width of the slit was 1″, length of the box during the spectra measurements was 1.5″. Data obtained by us and those compiled from literature showed that profiles of the Balmer lines Hα, Hβ and Hγ are different, evidencing that the gas emitting these lines is highly self-absorbed. It was shown that narrow components of the profiles revealed by Rubin and Ford kept their positions (radial velocities) over 25 years. The components showed intensity variations compared to the central one from minimum to maximum of the nucleus brightness. The same variations were observed by us earlier in the emission line profiles of the NGC 7469 nucleus spectrum. Narrow profile components can reflect long-lived flows or jets in the broad line region (BLR). Obtained facts evidenced that long-lived gas streams and flows causing narrow components of broad line profiles presented not only when BLR of accretion disc is strong but when BLR of accretion disc declined. Blue bump at radial velocity of ?5000 km/s in Hγ profile was revealed in spectra of high states of the nucleus, which disappeared in low state. One of the interpretations of this event can be in the framework of a model of one-sided or two-sided gas ejection during the high state of the nucleus, positive radial velocities of which being screened out by a circumnuclear disk.  相似文献   

17.
This work presents spectroscopic observations of Parsamian 21, which has been shown recently by Staude and Neckel to be a fuor-type star. A list of identified absorption lines is given. The results are compared with previous spectroscopic observations over the period 1966–1990. It is shown that the H line profile changed during this period; according to the observations of 1986, the center of the H absorption line was shifted by –140 km/sec from 0 and reached –600 km/sec at the line edge. It follows from the presented lightcurve that the star has undergone brightness variations of nearly three magnitudes and most likely became a fuor before 1902.Translated fromAstrofizika, Vol. 39, No. 2, pp. 227–235, April–June, 1996.  相似文献   

18.
Very-high spectral resolution observations of the neutral Na emission have enabled measurements of the velocity dispersions of the Na atoms within ∼40,000 km of the opto center of Hale-Bopp. Asymmetric Na D line profiles imply both an in situ or core Na source and a secondary Na source at locations within the inner coma. The core velocity distribution had a FWHM of 2 km s-1. The extended source FWHM increased with distance from the nucleus (up to ∼6 km s-1, but appeared smaller in the more dusty regions (∼2.5–3.0 km s-1) of the inner coma. The D2/D1 line strength ratio was consistent with an optically thin inner coma. Within 5,000 km of the opto center the continuum spatial intensity profiles decreased as ∼r-1 while the Na D emission decreased at less than r-1. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

19.
During the total eclipse of ε Aur, 18 spectra in the Hα region were taken in rapid succession on 1983 March 9, and 6 spectra on March 10, with the Reticon at the Coudé focus of the McDonald Observatory 2-metre telescope. The data were processed and plotted by computer. Variations on short time-scales were observed in the radial velocities of the metallic lines and Hα. The radial velocities of individual metallic lines are between 3 and 16 km/s more negative than calculated from the orbital elements. The Hα has 3 emission features with equivalent widths 300 mÅ, 54 mÅ and 1 mÅ and 1 absorption feature with an equivalent width of 1800 mÅ. The profile and the equivalent widths changed only slightly while substantial variations occurred on the blue side of the two stronger emission features. The radial velocities of the emission features are about ?60, +12 and +57 km/s; that of the absorption component is +20 km/s. The radial velocity of the strongest emission feature also varies, but by much smaller amounts than the metallic lines and the variation appears to be periodic. A model in which the secondary is a B-star surrounded by hot, active clouds is proposed.  相似文献   

20.
In an earlier research the employment of a radiation transport model with angle-dependent partial frequency redistribution, self-absorption by interplanetary hydrogen, realistic solar HLyαemission profile, and a time dependent `hot' hydrogen model to analyze 5 interplanetary HLyα glow spectra obtained with theHubble–Space–Telescope–GHRS spectrometer, has not resulted in unequivocal determination of a set of thermodynamical parameters of the interstellar hydrogen The residual discrepancies between the model and the data concern the observations performed within an interval of 1 year close to the solar minimum from very similar lines of sight. In this paper we investigate by calculating interplanetary HLyα lines with the use of a one hydrogen distribution and several solar HLyα line profiles whether this residual may be caused by possible variations in time of the shape of the solar HLyα emission line profile which cause variable illuminations of the interplanetary gas. These variations of illuminations cause variations in Doppler shift of the resonant interplanetary HLyα line that can amount to ≃ 4 km s-1in the line peak. Consequently we conclude that without adequate knowledge of the solar HLyα emission line profile during spectral observations of the interplanetary hydrogen gas it is impossible to obtain an agreement between models and observations better than by this value. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号