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1.
Kye Hwa Yoo   《New Astronomy》2010,15(2):215-226
The symbiotic variable star CH Cygni went on the deepest minimum phase in December 2006. A high-resolution spectrum of CH Cygni obtained at the Bohyunsan Optical Astronomy Observatory (BOAO) on November 2, 2006, is reported. The spectrum of CH Cygni obtained at the BOAO was calibrated on a scale of an absolute-flux density. Emission lines of H I, [O III], [N II], and [S II] were strong, with several components, and Ca II, H, and K lines had P-Cygni profiles. Removal of the spectrum of the underlying M-type star from the CH Cygni spectrum was completed to obtain the true emission profiles. The radial velocities of all emission and absorption lines were measured. Some of the observed lines were also deconvoluted using multi-Gaussian functions to find the relationship between line shapes and the corresponding sources of these lines. The results obtained are discussed in terms of an accretion disk around the hot star, and in non-spherically extended nebular regions.  相似文献   

2.
《New Astronomy》2007,12(7):569-577
We report in a series on the spectra of CH Cygni obtained in October 2004 in this paper. The spectra showed emission lines of H I, [O I], [O III], [N II], [Ne III] and Fe II: most of them became stronger than those obtained in April 2004. In order to retrieve the intrinsic emission profile, we removed the underlying M-type spectrum and telluric lines of O2 from the spectra. Then, we deconvoluted the resulting Hα and [O III] profiles into several Gaussian functions. Radial velocities of all lines observed in October 2004 were measured.Results are compared with those in April 2004, and are discussed by way of an accretion disk and a circumstellar model.  相似文献   

3.
We present low and high resolution ultraviolet spectra of the Capella spectroscopic binary system from the observations taken by the International Ultraviolet Explorer (IUE) during the period between 1978–1990 and 1978–1995. Thirteen profile of Capella showing variations of line fluxes at different orbital phases are presented. This paper focuses on the C IV emission line at 1550 Å produced in the transition region of the secondary star and Mg II emission lines at 2800 Å produced in the stellar chromosphere of the secondary star by calculating spectral line fluxes. Our results show that there are significant variations of line fluxes with time. These spectral variations are similar to that found in the EUV by Dupree and Brickhouse (in Int. Astron. Union Symp. 176P:184D, 1995) in the UV for H 1 Ly?α by Ayres et al. (in Astrophys. J. 402:710A, 1993), and in the near IR by Katsova (in Astrophys. Space Sci. 252:427K, 1997). We attribute these variations in line fluxes to the variations of both density and temperature in the line emitting regions as a result of the intermediate-scale magnetic fields responsible for stellar activity leading to these spectral variations.  相似文献   

4.
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   

5.
The T Tauri variable V1331 Cyg is characterized by an intensive emission spectrum, by signatures of a high rate of mass loss, and also by presence of a circular reflection nebula. According to these characteristics, the star can be considered as a possible pre-FUor star. Up to the present the photospheric spectrum of the star has not been recorded. In this work we analyze the high-resolution spectra of V1331 Cyg that were obtained by G.H. Herbig with the HIRES spectrograph at the Keck-1 telescope in 2004 and 2007. For the first time the numerous photospheric lines of the star have been detected and the spectral class has been estimated, viz., G7-K0 IV. It is revealed that the projection of the rotation velocity is lower than the width of instrumental profile (vsini < 6 km/s); this means that the angle between the stellar axis of rotation and the line of sight is small. The radial velocity of the star derived from the photospheric lines is RV = ?15.0 ± 0.3 km/s. The difference in radial velocities for 2004 and 2007 is lower than the measurement error. The photospheric spectrum is veiled considerably, but the amount of veiling is not the same in different lines. This depends on the line strength in the template spectrum of the G7 IV star: in the weakest lines (EW = 5–10 mÅ in the template spectrum) VF ≈ 1 and it increases up to 4–5 in stronger lines. The Hα and Hβ lines demonstrate classical P Cyg profiles, which testifies to an intensive wind with a maximal velocity of about 400 km/s. In addition, the emission lines of Fe II, Mg I and K I and of several other elements are accompanied by a narrow blue-shifted absorption at ?150...?250 km/s. The emission spectrum of V1331 Cyg is rich in the narrow (FWHM = 30–50 km/s) lines of neutral and ionized metals showing the excitation temperature T exc = 3800 ± 300 K. The stellar mass M* ≈ 2.8M ⊙ and radius R* ≈ 5R ⊙ are estimated.  相似文献   

6.
M.R. Sanad 《New Astronomy》2010,15(1):113-118
We analyze both long and short high resolution ultraviolet spectrum of Beta Lyrae eclipsing binary system observed with the International Ultraviolet Explorer (IUE) between 1980 and 1989. The main spectral features are P Cygni profiles originating from different environments of Beta Lyrae. A set of 23 Mg II k&h spectral lines at 2800 Å, originating from the extended envelope [Hack, M., 1980. IAUS, 88, 271H], have been identified and measured to determine their fluxes and widths. We found that there is spectral variability for these physical parameters with phase, similar to that found for the light curve [Kondo, Y., McCluskey, G.E., Jeffery, M.M.S., Ronald, S.P., Carolina, P.S. McCluskey, Joel, A.E., 1994. ApJ, 421, 787], which we attribute to the eclipse effects [Ak, H., Chadima, P., Harmanec, P., Demircan, O., Yang, S., Koubský, P., ?koda, P., ?lechta, M., Wolf, M., Bo?i?, H., 2007. A&A, 463, 233], in addition to the changes of density and temperature of the region from which these lines are coming, as a result of the variability of mass loss from the primary star to the secondary [Hoffman, J.L., Nordsieck, K.H., Fox, G.K., 1998. AJ, 115, 1576; Linnell, A.P., Hubeny, I., Harmanec, P., 1998. ApJ, 509, 379]. Also we present a study of Fe II spectral line at 2600 Å, originating from the atmosphere of the primary star [Hack, M., 1980. IAUS, 88, 271H]. We found spectral variability of line fluxes and line widths with phase similar to that found for Mg II k&h lines. Finally we present a study of Si IV spectral line at 1394 Å, originating from the extended envelope [Hack, M., 1980. IAUS, 88, 271H]. A set of 52 Si IV spectral line at 1394 Å have been identified and measured to determine their fluxes and widths. Also we found spectral variability of these physical parameters with phase similar to that found for Mg II k&h and Fe II spectral lines.  相似文献   

7.
Our spectroscopic observation of the Be/X-ray binary LSI+65°010 showed a dramatic variation in November 1992 with an increase by a factor of more than 3 in the equivalent width of the Hα emission line. This supports the view that the primary is a Be star rather than a supergiant. A well-defined double-peaked profile in seen in the spectrum of September 1994: while the red peak remained at 6563 Å, the blue one was −7.2Å to the blue. We suggest that such a profile is caused by the superposition of two emission lines, one from the shell of the Be star, one from an H II region around the neutron star. This provides, for the first time, direct observational evidence for the existence of a H II region around compact object and caused by X-ray emission. On 1992-11-04, the red side of the Hα line did not change while the blue side was greatly enhanced. We suggest that this may be caused by the H II region around the neutron star.  相似文献   

8.
We present the results of spectroscopic and photometric observations for the B star StHα62 with an IR excess, a post-AGB candidate identified with the IR source IRAS 07171+1823. High-resolution spectroscopy has allowed the λ4330–7340 Å spectrum of the star to be identified: it contains absorption lines of an early B star and emission lines of a gaseous shell. The residual line intensities have been measured. The heliocentric radial velocities measured from absorption lines of the star and emission lines of the shell are 〈V r 〉 = +45 ± 1 and +52 ± 1 km s?1, respectively. The line-of-sight velocities of gas-dust clouds determined from the interstellar Na I lines are 12 and 33 km s?1. The He I λ5876 Å line exhibits a P Cyg profile, which is indicative of an ongoing mass loss by the star. The expansion velocity of the outer shell estimated from forbidden lines is 12–13 km s?1. Quantitative classification gives the spectral type B0.51 for the star. The parameters of the gaseous shell have been determined: N e = 3.1 × 103 cm?3 and T e ～ 21 000 K. Over 4 years of its observations, the star showed rapid irregular light variations with the amplitudes ΔV = We present the results of spectroscopic and photometric observations for the B star StHα62 with an IR excess, a post-AGB candidate identified with the IR source IRAS 07171+1823. High-resolution spectroscopy has allowed the λ4330–7340 ? spectrum of the star to be identified: it contains absorption lines of an early B star and emission lines of a gaseous shell. The residual line intensities have been measured. The heliocentric radial velocities measured from absorption lines of the star and emission lines of the shell are 〈V r 〉 = +45 ± 1 and +52 ± 1 km s−1, respectively. The line-of-sight velocities of gas-dust clouds determined from the interstellar Na I lines are 12 and 33 km s−1. The He I λ5876 ? line exhibits a P Cyg profile, which is indicative of an ongoing mass loss by the star. The expansion velocity of the outer shell estimated from forbidden lines is 12–13 km s−1. Quantitative classification gives the spectral type B0.51 for the star. The parameters of the gaseous shell have been determined: N e = 3.1 × 103 cm−3 and T e ∼ 21 000 K. Over 4 years of its observations, the star showed rapid irregular light variations with the amplitudes ΔV = , ΔB = , and ΔU = and no color-magnitude correlation. We estimate the total extinction for the star from our photometric observations as A v = . Near-IR observations have revealed dust radiation with a temperature of ∼1300 K. We estimate the distance to StHα62 to be r = 5.2 ± 1.2 kpc by assuming that the star is a low-mass (M = 0.55 ± 0.05 M ⊙) protoplanetary nebula. Original Russian Text ? V.P. Arkhipova, V.G. Klochkova, E.L. Chentsov, V.F. Esipov, N.P. Ikonnikova, G.V. Komissarova, 2006, published in Pis’ma v Astronomicheskiĭ Zhurnal, 2006, Vol. 32, No. 10, pp. 737–747.  相似文献   

9.
We present photoelectric and spectral observations of a hot candidate proto-planetary nebula—early B-type supergiant with emission lines in spectrum—IRAS 19336-0400. The light and color curves display fast irregular brightness variations with maximum amplitudes \(\Delta V = 0_ \cdot ^m 30\), \(\Delta B = 0_ \cdot ^m 35\), \(\Delta U = 0_ \cdot ^m 40\) and color-brightness correlations. By the variability characteristics IRAS 19336-0400 appears similar to other hot proto-planetary nebulae. Based on low-resolution spectra in the range λ4000–7500 Å we have derived absolute intensities of the emission lines Hα, Hβ, Hγ, [S II], [N II], physical conditions in gaseous nebula: n e = 104 cm?3, T e = 7000 ± 1000 K. The emission line Hα, Hβ equivalent widths are found to be considerably variable and related to light changes. By UBV-photometry and spectroscopy the color excess has been estimated: E B-V = 0.50–0.54. Joint photometric and spectral data analysis allows us to assume that the star variability is caused by stellar wind variations.  相似文献   

10.
We present photoelectric and spectroscopic observations of the protoplanetary object V 1853 Cyg, a B supergiant with an IR excess. Over two years of its observations, the star exhibited rapid irregular light variations with amplitudes $\Delta V = 0\mathop .\limits^m 3$ , $\Delta B = 0\mathop .\limits^m 3$ , $\Delta U = 0\mathop .\limits^m 4$ and no correlation between color and magnitude. Its mean magnitude has not changed since the first UBV observations in 1973 (Drilling 1975). Low-resolution spectroscopic observations show that the spectrum of V 1853 Cyg in 2000 corresponded to that of a B1–B2 star with T eff ～ 20000 K. High-resolution spectroscopic observations confirm the conclusion that the profiles of absorption and emission lines are variable. We identified the star’s spectral lines and measured the equivalent widths of more than 40 lines. The star’s radial velocity is 〈V r 〉= ?49 × 5 km s?1, as measured from absorption lines, and ranges from–50 to–85 km s–1 for different lines, as measured from shell emission lines. The velocity of the dust clouds on the line of sight determined from diffuse interstellar bands (DIBs) and from interstellar Na I lines is 〈V r 〉= ?16 × 5 km s?1. The P Cyg profiles of the He I λ5876 Å and λ6678 Å lines suggest an ongoing mass loss by the star. An analysis of the observational data confirms the conclusion that the star belongs to the class of intermediatemass protoplanetary objects.  相似文献   

11.
We investigated the line profiles of the high dispersion spectra of He?I, He?II, N?III, [N?II], [O?III], [Ar?III], [Ar?IV], [S?II], [S?III ], and [Cl?IV], secured at the center of the planetary nebula NGC 7009 with the fiber-fed Bohyunsan Echelle Spectrograph (BOES). The expansion velocities for the main shell and the faint outer thin shell were derived based on stronger double Gaussian profiles and the fast blue wing component, respectively. With the Keck 2D spectral images, we set the main shell boundaries as R～4″ and 6″ and the faint outer thin shell boundaries as R～11″ and 13″. The radial variation of expansion velocities of both shells does not follow a linear acceleration. The acceleration of the main shell gas seems to be in a retarded mode, while that of the outer faint shell gas seems to be affected by an additional force. The fast wing component appears also in the He?I, He?II, and N?III line profiles which are likely to have been formed in a compact region, located inside the main shell. The additional deceleration factor, such as the rotation of the central star or the dust gas in the gas shell might cause the non-linear acceleration. Based on the line profiles responsible for the three zones, we conclude that there were at least three major changes occurred in the central star temperature since the first outflow from the central star.  相似文献   

12.
Investigation of 38 Zeeman spectrograms of the Be star EW Lac obtained in three successive years, 1978, 1979, and 1980, yield no hints at the occurrence of a global magnetic field larger than 150 Gauß. The temporal variations of the radial velocities of the Balmer and metallic absorption lines indicate a disturbance travelling through the envelope of EW Lac from the inner to the outer parts. The observed variations of the line widths and equivalent widths of the metallic lines suggest that the physical parameters remarkable change. These results together with the measured variations of the radial velocity and intensity of the emission features of Hβ can be explained by a thick elliptical ring surrounding EW Lac.  相似文献   

13.
We present the results of spectroscopic and photometric observations for the young compact planetary nebula Hen 3–1357 and its central star SAO 244567. High-resolution spectroscopy has allowed the expansion velocity of the nebula, V exp = 8.4 ± 1.5 km s?1, and the heliocentric velocity of the object, V r = +12.6 ± 1.7 km s?1, to be determined. The gas shell parameters (N e , T e ), the extinction in the Hβ line, and the O, N, Ne, Ar, S, Cl, He, and C abundances have been determined from low-resolution spectra taken in 1992 and 2011. We have found significant changes in the relative intensities of forbidden lines in the spectrum of Hen 3–1357 within the last 20 years: the low-excitation [O I], [O II], and [N II] lines became stronger relative to Hβ by a factor of ～2, while the [O III] lines weakened by a factor of ～ 2, suggesting a decrease in the excitation class of the nebula. The V-band photometry performed under the ASAS-3 program revealed a decline in the yearly mean brightness of SAO 244 567 from 2001 to 2009 by $0_.^m 5$ and rapid variability with an amplitude of a few tenths of a magnitude. Published observational data in a wide spectral range, from the near ultraviolet to the radio band, suggest an appreciable weakening of the flux from the star and the nebula.  相似文献   

14.
By means of a batch of low-redshift spectral data of AGNs taken from the SDSS, an automated K-nearest neighbor method is developed to classify AGNs into two types: broad-line and narrow-line AGNs. According to the different characteristics of emission lines of broad-line and narrow-line AGNs, the spectral wavebands containing the Hβ, [OIII], H and [NII] emission lines are used separately or in combination in the classification. experiment. The results show that the best results are obtained when only the wavebands of H and [NII] are used, and that for a training set of size 1000 and a testing set of 3313, we can achieve a speed of 32.89 single classifications per second. It is demonstrated that, where the typical spectral features are sufficiently exploited, the automated classification method is feasible for the spectra of AGNs in largescale spectral surveys and provides a fast and straightforward alternative to classification schemes based on using the FWHM values of emission lines or the line strength ratio diagnostic diagrams.  相似文献   

15.
We present ultraviolet spectra of two eclipsing interacting binary systems, W Ser and UX Mon, with good coverage over the 14.16-day and 5.9-day orbital periods, respectively, using observations taken by the International Ultraviolet Explorer (IUE) during the period between 1978–1993 and 1981–1991. Two profiles of W Ser and UX Mon showing variations of line fluxes at two orbital phases are presented. This paper focuses on the N V emission line at 1240 Å, C II emission line at 1336 Å, C IV emission line at 1550 Å, O III emission line at 1666 Å and the Si III emission line at 1892 Å, produced in an extended gaseous envelope around the mass-gaining component by calculating spectral line fluxes. Our results show that there are variations of line fluxes with time, similar to the light curves found for both W Ser and UX Mon. We attribute these spectral variations to eclipse effects and to variations in the mass transfer rate. These results from the IUE observations support the thick disk model around the primary star in which variations of mass transfer affect the observed radiation from the gaseous envelope around the hot star. Future, high-resolution imaging is recommended to confirm the inferred asymmetrical circumstellar envelopes.  相似文献   

16.
We propose a multicomponent analysis of starburst galaxies, based on a model that takes into account the young and evolved stellar components and the gas emission, with their respective extinction, in the frame of a coherent dust distribution pattern. Near-IR signatures are preferentially investigated, in order to penetrate as deep as possible into the dusty starburst cores. We computed the 1.4-2.5 μm spectra of synthetic stellar populations evolving through strong, short timescale bursts of star formation (continuum and lines, R ? 500). The evolution model is specifically sensitive to cool stellar populations (AGB and red supergiant stars). It takes advantage of the stellar library of Lançon & Rocca-Volmerange (1992) [A&ASS, 96, 593], observed with the same instrument (FTS/CFHT) as the analysed galaxy sample, so that the instrumental effects are minimised. The main near-IR observable constraints are the molecular signatures of CO and H2O and the slope of the continuum, observed over a range exceptionally broad for spectroscopic data. The H - K colour determined from the spectra measures the intrinsic stellar energy distribution but also differential extinction, which is further constrained by optical emission line ratios. Other observational constraints are the near-IR emission lines (Brγ, He I 2.06 μm, [Fe II] 1.64 μm, H2 2.12 μm) and the far-IR luminosity. The coherence of the results relies on the interpretation in terms of stellar populations from which all observable properties are derived, so that the link between the various wavelength ranges is secured. The luminosity LK is used for the absolute calibration.We apply this approach to the typical spectrum of the core of NGC 1614. Consistent solutions for the starburst characteristics (star-formation rate, IMF, burst age, morphology) are found and the role of each observational constraint in deriving satisfactory models is extensively discussed. The acceptable contamination of the K band light by the underlying population amounts ≥ 15% even through a 5 arcsec aperture. The model leads to a limit on the direct absorption of Lyman continuum photons by dust situated inside the ionised areas, which in turn, with standard gas-to-dust ratios, translates into small characteristic sizes for the individual coexisting H II regions of the massive starburst area (clusters containing ∼ 102 ionising stars). We show that room is left for IMFs extending to 120 M⊙, rather than truncated at ∼ 60 M⊙ as most conservative studies conclude. High internal velocity dispersions (≥ 20 km s−1) are then needed for the H II regions. An original feature of this work is to base the analysis of near-infrared spectral galaxy observations on a large wavelength range, using models constructed with spectral stellar data observed with the same instrument. However a broader use of this spectral evolution model on other spectral or photometric data samples is possible if the spectral resolution of the model is adapted to observations or if colours are derived from the energy distributions.Catherine J. Cesarsky  相似文献   

17.
The results of investigations of the Hα and Hβ lines in the spectrum of the star HD 206267 are presented. Observations were carried out in 2011–2014 at the Cassegrain focus of the 2-m telescope of the Tusi Shamakhy Astrophysical Observatory of the National Academy of Sciences of Azerbaijan using an echelle spectrometer. The following features have been revealed for the first time: the moving discrete absorption components in the core of the Hα line from the red side to the violet, the stable emission in the violet wing of the Hα line, the antiphase variation of the radial velocities and equivalent widths of the Hα line, and the independence of the changes of the equivalent widths of the Hβ line from the phase of the orbital period. No spectral features according to which this star could be considered as a source of X-ray radiation have been found.  相似文献   

18.
We present the results of a spectral study of 17 galaxies with UV excess from the lists of [1–3]. We determine the equivalent widths of lines, the relative intensities of emission lines for 3 galaxies, the electron densities of the gas components of 9 galaxies, and the gas masses of 2 galaxies. It is shown that the gas component of Galaxy No. 235 has extremely low excitability. In the spectrum of this galaxy the lines [Fell] 4951, 4947 are seen to be distinct, not merging with the line [OIII] 4959. The line H in the spectrum of Galaxy No. 128 has two emission peaks, which seem to have been formed by an absorption component midway between the lines. The line H in the spectrum of Galaxy No. 350 is detected both in emission and absorption, the absorption component lying in the longwave part of the line.Translated fromAstrofizika, Vol. 37, No. 3, 1994.  相似文献   

19.
As part of a study of star formation history along the Hubble sequence, we present here the results for 11 elliptical galaxies with strong nebular emission lines.After removing the dilution from the underlying old stellar populations by use of stellar population synthesis model,we derive the accurate fluxes of all the emission lines in these objects,which are then classified,using emission line ratios, into one Seyfert 2,six LINERs and four HII galaxies.We also identify one HII galaxy (A1216 04)as a hitherto unknown Wolf-Rayet galaxy from the presence of the Wolf- Rayet broad bump at 4650 (?).We propose that the star-forming activities in elliptical galaxies are triggered by either galaxy-galaxy interaction or the merging of a small satellite/a massive star cluster,as has been suggested by recent numerical simulations.  相似文献   

20.
《New Astronomy Reviews》2002,46(2-7):203-205
With objectives to model star formation in radio galaxies, we present results of a starburst model, built by coupling the two codes PÉGASE and CLOUDY. Continuum and emission line data are used to derive the properties of a sample of local starbursts. Data are well reproduced with a new relation between the ionization parameter and the metallicity. Colors and Hα equivalent widths indicate that: (i) an underlying stellar population is needed, and (ii) burst ages span the range [0, 6] Myr.  相似文献   

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