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1.
Based on high-resolution observations (R = 60 000 and 75 000), we have studied the optical spectral variability of the star BD + 48°1220, identified with the IR source IRAS 05040+4820. We have measured the equivalent widths of numerous absorption lines of neutral atoms and ions at wavelengths from 4500 Å to 6760 Å, as well as the corresponding radial velocities. We use model atmospheres to determine the effective temperature T eff = 7900 K, surface gravity log g = 0.0, microturbulence velocity ξ t = 6.0, and the abundances for 16 elements. The star’s metallicity differs little from the solar value: [Fe/H] = ?0.10 dex. The main peculiarity of the chemical composition of the star is a large helium excess, derived from the Hel λ 5876 Å absorption, [He/H] = +1.04, and the equally large oxygen excess, [O/Fe] = +0.72 dex. The carbon excess is small, [C/Fe] = +0.09 dex, and the ratio [C/O] < 1. We obtained an altered relation for the light-metal abundances: [Na/Fe] = +0.87 dex with [Mg/Fe] = ?0.31 dex. The barium abundance is low, [Ba/Fe] = ?0.84 dex. It is concluded that the selective separation of elements onto dust grains of the envelope is probably efficient. The radial velocity of the star measured from photospheric absorption lines over three years of observations varies in the interval V ⊙ = ?(7–15) km/s. Time-variable differential line shifts have been revealed. The entire set of available data (the luminosity M v ≈ ?5 m , velocity V lsr ≈ ?20 km/s, metallicity [Fe/H] = ?0.10, and peculiarities of the optical spectrum and chemical composition) confirms the status of BD + 48°1220 as a post-AGB star with He and O excesses belonging to the Galactic disk.  相似文献   

2.
The basic parameters and detailed chemical compositions of three asymptotic giant branch stars with similar effective temperatures and surface gravities have been determined using CCD spectra obtained with the échelle spectrometers of the SAO 6-m telescope. The metallicity and chemical composition of the optical counterpart of the OH/IR star IRAS 18123 + 0511 have been derived for the first time. The abundance [X/H]⊙ of the iron group elements (V, Cr, Fe) is ?0.45 dex. An overabundance of oxygen, [O/Fe]⊙=1.44 dex, is detected in the atmosphere of this star. The abundances of s-process heavy elements are not enhanced, and are instead underabundant with respect to the metallicity: the average value of [X/Fe]⊙ for Y, Zr, Ba, La, Ce, Pr, Nd is ?0.25. The derived abundances confirm that IRAS 18123 + 0511 is in the AGB stage of its evolution. The metallicity of the object, together with its radial velocity V r=78.0 km/s and Galactic latitude |b|=11°, suggest that it belongs to the old disk population. The expansion velocity of the circumstellar envelope, V exp≈21 km/s, is derived from the positions of circumstellar absorption bands. The set of parameters obtained for the low-metallicity, highlatitude supergiants BD + 18° 2757 and BD + 18° 2890 (with iron abundances [Fe/H]⊙=2.10 and ?1.48, respectively) confirm that they are evolved halo stars, and probably UU Her-type stars.  相似文献   

3.
Based on long-term spectral monitoring with high spectral resolution, the optical spectrum of the weak central star of the IR source RAFGL 5081 has been studied for the first time. The spectral type of the star is close to G5–8 II, and its effective temperature is Teff ≈ 5400 K. An unusual spectral phenomenon was discovered: splitting of the profiles of broad, stationary absorption lines of medium and low intensity. The heliocentric radial velocities V r of all components of metal absorption lines, the Na I D lines, and the Hα line were measured for all the observation epochs. The constancy of the absorption lines rules out the possibility that the line splitting is due to binarity. The radial velocities of the wind components in the profiles of the Na I D and Hα lines reach ?250 and ?600 km/s, respectively. These profiles have narrow components, whose number, depth, and position vary with time. The time variability and multicomponent structure of the profiles of the Na I D and Hα lines indicates inhomogeneity and instability of the circumstellar envelope of RAFGL 5081. The presence of components with velocity V r (IS) = ?65 km/s in the Na I (1) lines provides evidence that RAFGL 5081 is located behind the Perseus arm, i.e, no closer than 2 kpc. It is noted that RAFGL 5081 is associated with the reflection nebula GN 02.44.7.  相似文献   

4.
Multiple observations of the yellow hypergiant ρ Cas obtained in 2007–2011 in a wide wavelength range with spectroscopic resolving power R ≥ 60 000 have enabled studies of features of its optical spectrum in detail and brought to light previously unknown characteristics of the star’s extended atmosphere. The radial velocity measured from symmetric absorption lines of metals varies with an amplitude of about ±7 km/s around the systemic velocity V sys = ?47 km/s, due to low-amplitude pulsations of the atmospheric layers near the photosphere. At some times, a velocity gradient was observed in deep atmospheric layers of the star. A slight velocity stratification in the stellar atmosphere was detected for the first time, manifest as a difference of 3–4 km/s in the velocities measured from absorption lines of neutral metals and of ions. The long-wavelength components of split absorption lines of BaII, SrII, TiII, and other strong lines with low excitation potentials for their lower levels are distorted by nearby emission lines. It is suggested that the short-wavelength components, whose locations correspond to the narrow velocity range V r (blue) from approximately ?60 to ?70 km/s, are formed in a circumstellar envelope; one component of the D NaI doublet and the emission components of the FeII 6369.46 and 6432.68 Å ions are also formed there.  相似文献   

5.
Multi-epoch observations with high spectral resolution acquired in 1998–2008 are used to study the time behavior of the spectral-line profiles and velocity fields in the atmosphere and circumstellar shell of the post-AGB star V448 Lac. Asymmetry of the profiles of the strongest absorption lines with lower-level excitation potentials χ low < 1 eV and time variations of these profiles have been detected, most prominently the profiles of the resonance lines of BaII, YII, LaII, SiII. The peculiarities of these profiles can be explained using a superposition of stellar absorption line and shell emission lines. Emission in the (0; 1) 5635 Å Swan system band of the C2 molecule has been detected in the spectrum of V448 Lac for the first time. The core of the Hα line displays radial-velocity variations with an amplitude of ΔV r ≈ 8 km/s. Radial-velocity variations displayed by weak metallic lines with lower amplitudes, ΔV r ≈ 1–2 km/s, may be due to atmospheric pulsations. Differential line shifts, ΔV r = 0–8 km/s have been detected on various dates. The position of the molecular spectrum is stationary in time, indicating a constant expansion velocity of the circumstellar shell, V exp = 15.2 km/s, as derived from the C2 and NaI lines.  相似文献   

6.
We present the results of monitoring the H2O masers in the IR sources IRAS 18265-1517 and IRAS 18277-1516 associated with the cool molecular cloud L 379, which contains high-velocity bipolar molecular jets. The sources were observed in the 1.35 cm H2O line using the 22-m radio telescope of the Pushchino Radio Astronomy Observatory (Russia) during 1991–2004. We detected H2O maser emission from IRAS 18265-1517 at radial velocities of 17.8 and 18.4 km/s, virtually coincident with the velocity of the molecular cloud derived from CO-line observations (18.4 km/s). The maser emission towards the other source, IRAS 18277-1516, was at higher velocities than the central velocity of the CO molecular cloud. The H2O maser spots are most likely associated with a redshifted region of CO emission. Cyclic variability of the integrated H2O maser emission that may be related to cyclic activity of the central star was detected for IRAS 18277-1516. The strongest and most long-lived component (VLSR ≈ 20.6 km/s) displays a radial-velocity drift, which could be due to deceleration of a dense clump of matter (maser condensation) in the circumstellar medium during the descending branch of a strong flare. We found numerous emission features for both IRAS 18265-1517 and IRAS 18277-1516, providing evidence for fragmentation of the medium surrounding their central objects.  相似文献   

7.
We have carried out a detailed identification of lines in the optical spectrum of the post-AGB star V510 Pup associated with the infrared source IRAS 08005-2356 based on observations with high spectral resolution. Absorption lines of the ions FeII, TiII, CrII, and YII are present at wavelengths from 4549 to 8546 Å. The absorption by YII and other s-process elements is anomalously strong, and the absorption is also strong in the circumstellar C2 Swan bands. The profiles of most of the lines (of hydrogen and metals) display P Cygni absorption-emission profiles. All the absorption lines are shifted toward the blue, suggesting an outflow of stellar material. The expansion velocity of the envelope derived from the Swan bands arising there is V exp =42 km/s. The highest wind velocity determined from the absorption wings of the FeII(42) P Cygni profiles reaches 240 km/s. Based on the star’s kinematic characteristics and the amount of interstellar absorption, it is at a distance of d≈3?4 kpc, which corresponds to an absolute magnitude of Mv≈?6m.  相似文献   

8.
We present new spectroscopic observations of the peculiar supergiant IRC+10420. In 1997–2000, we obtained three high signal-to-noise ratio spectra of the object at 4300–8000 Å with a spectral resolution of 15 000 (20 km/ s) using the 6-m telescope of the Special Astrophysical Observatory. From our 2000 spectrum, we estimate the spectral type of IRC+10420 to be A2, corresponding to a temperature of ～9200 K. Many emission lines were detected, identified with lines of Fe I; Fe II, Ti II, Cr II, and Sc II ions; and [O I], [Fe II], and [Ca II] forbidden lines. The radial velocity derived from absorption lines without obvious emission components (He I λ5876, O I, N I, Si II) and from absorption components of the Balmer lines is 93±1 km/s. The redshift of photospheric lines relative to the star’s center-of-mass velocity is interpreted as a consequence of scattering in the expanding, optically thick dust envelope. Both emission and absorption lines show a correlation between radial velocity and oscillator strength. We found variability in the relative intensities of the H α and H β emission components. We conclude that IRC+10420 is rapidly evolving towards a Wolf-Rayet stage; the current rate of the photospheric temperature increase is ～120 K per year. Based on the intensity of the O I (λ7773) triplet, we estimate the star’s luminosity to be M bol=?9.5m. In all 1997–2000 spectra of IRC+10420, the He I λ5876 line has a significant equivalent width of at least 200 mÅ; this may be possible in the presence of such a low temperature due to the star’s high luminosity and the enhanced helium abundance in the supergiant’s atmosphere.  相似文献   

9.
We present a detailed analysis of the optical spectrum of the post-AGB star HD 56126 (IRAS 07134+1005) based on observations made with the echelle spectrographs of the 6-m telescope of the Special Astrophysical Observatory with resolutions of R = 25 000 and 60 000 at 4012-8790 Å. The profiles of strong lines (HI; FeII, YII, BaII absorption lines, etc.) formed in the expanding atmosphere at the base of the stellar wind display complex and variable shapes. To study the kinematics of the atmosphere, the velocities of individual features in these profiles must be measured. Differential line shifts of up to ΔV r = 15–30 km/s have been detected from the lines of metals and molecular fetures. The stellar atmosphere simultaneously contains both expanding layers and layers falling onto the star. A comparison of the data for different times demonstrates that both the radial velocity and the overall velocity pattern are variable. The position of the molecular spectrum is stable, implying stability of the expansion velocity of the circumstellar envelope around HD 56126 detected in observations in the C2 and NaI lines.  相似文献   

10.
Results of a study of the shell of Nova V2659 Cyg based on spectrophotometric observations carried out over a year and a half after its eruption are presented. The physical conditions in the nova shell have been studied. The electron temperature (9000 K) and density (5 × 106 cm?3) in the nebular stage have been estimated, together with the abundances of helium, oxygen, nitrogen, neon, argon, and iron. The abundances of nitrogen, oxygen, neon, and argon are enhanced relative to the solar values. The relative abundances are [N/H] = 2.26 ± 0.25 dex, [O/H] = 1.66 ± 0.35 dex, [Ne/H] = 0.78 ± 0.25 dex, and [Ar/H] = 0.32 ± 0.38 dex. The estimated mass of oxygen and total mass of the emitting shell are ≈1 × 10?4M⊙ and ≈3 × 10?4M⊙, respectively. In the period of chaotic brightness oscillations, the maximum velocity of the shell expansion derived from the radial velocities of the absorption components of the HI and FeII line profiles increased by ≈400 km/s 41 days after the maximum, and by ≈200 km/s 101 days after the maximum, reaching 1600 km/s in both cases.  相似文献   

11.
Data on the global magnetic field (GMF) of the Sun as a star for 1968–1999 are used to determine the correlation of the GMF with the radial component of the interplanetary magnetic field (IMF) |B r|; all data were averaged over a half year. The time variations in the GMF |H| are better correlated with variations in |B r|; than the results of extrapolating the field from the “source surface” to the Earth’s orbit in a potential model based on magnetic synoptic maps of the photosphere. Possible origins for the higher correlation between the GMF and IMF are discussed. For both the GMF and IMF, the source surface actually corresponds to the quiet photosphere—i.e., background fields and coronal holes—rather than to a spherical surface artificially placed ≈2.5 R ⊙ from the center of the Sun, as assumed in potential models (R ⊙ is the solar radius). The mean effective strength of the photospheric field is about 1.9 G. There is a nearly linear dependence between |H| and |B r|. The strong correlation between variations in |H| and |B r| casts doubt on the validity of correcting solar magnetic fields using the so-called “saturation” factor δ?1 (for magnetograph measurements in the λ 525.0 nm FeI line).  相似文献   

12.
The fine structure of the active region in the Orion KL gas-dust complex has been measured in polarized H2O maser emission (epoch December 12, 1998) with an angular resolution of 0.15 mas, or 0.07 AU, and a velocity resolution of 0.05 km/s. The maser emission is concentrated in a line with ΔV = 0.45 km/s, V LSR = 7.65 km/s, and a flux density of F = 2.1 MJy. The structure consists of a compact source (ejector), highly collimated bipolar outflow, and a toroidal component. The brightness temperature of the ejector is T b = 2 × 1016 K, and its degree of linear polarization reaches m ≈ 20%. The variation of the polarization angle across the profile is dX/dV = ?23°/(km/s), which considerably exceeds the Faraday rotation in the HII region foreground to the molecular cloud. The observed “rotation” is explained as an effect of different orientations for the polarization of the ejected outflows. The brightness temperature of the bipolar outflow is T b ≈ 1014 K, while that of individual components is T b ≈ 1015 K. The degree of polarization in the components exceeds that of the ejector and reaches m ≈ 50%. The position angle of the polarization is X ≈ 45° relative to the outflow. The torus, which is observed edge-on, has a diameter of 0.38 AU and a thickness of 0.08 AU. The brightness temperature of the tangential directions in the torus is T b ≈ 5 × 1015 K, and the rotational velocity is V rot ≈ 0.02 km/s. The degree of polarization is m ≈ 40%, and its position angle relative to the azimuthal plane is X ≈ 43°. The relative deviations of the polarization plane in the bipolar outflow and torus relative to the pumping direction are nearly the same and are determined by Faraday rotation within the HII region.  相似文献   

13.
We have studied variability of the spectral lines of the OB star δOri A—the brightest component of the δOri triple system. Forty spectra with signal-to-noise ratios ≈500–800 and a time resolution of four minutes were obtained. We detected variability in the HeIIλ4686, HeIλ4713, and Hβ absorption and the CIIIλ5696 emission profiles. The amplitude of the variability is ≈(0.5–1)% of the continuum intensity. The dynamical wavelet spectrum of the profile variations reveals large-scale components in the interval 25–50 km/s that move within the-V sin i to V sin i band for the primary star of the system, Aa1, with a band crossing time of 4h–5h. However, some of the variable features go outside the band, presumably due to either imhomogeneities in the stellar wind from δOri Aa1 or nonradial pulsations of the weaker components of the system, Aa2 or Ab. The detected variability may be cyclic with a period of ≈4h. We suggest that it is associated with nonradial pulsations of the primary in the sector mode (l,m) = (2, ?2).  相似文献   

14.
A new OH maser was detected in January 2008 toward the infrared source IRAS 05338-0624 in the dark cloud L1641N. The observations were carried out on the Nan cay Radio Telescope (France) in the 1667 and 1665 MHz OH lines. In the spectra of both lines, thermal OH emission from the surrounding molecular cloud is present at radial velocities V LSR = 6–9 km/s. In addition, a narrow maser feature is present in both lines at V LSR = 2 km/s in the profiles obtained on January 7, 2008; the peak flux densities at 1667 and 1665 MHz are 1.5 and 0.4 Jy, respectively. No OH maser emission was detected in February–July 2008. Then, a maser feature was again observed in the 1665 MHz line on August 20, 2008, at the same velocity as in January, V LSR = 2 km/s, with a peak flux density of 0.4 Jy. No 1667 MHz counterpart was observed with an upper limit of ～0.1 Jy. Emission in both OH lines was again absent on September 18. The source was also observed in the H2O line at λ = 1.35 cm on the 22-m radio telescope of the Pushchino Radio Astronomy Observatory (Russia) on February 7 and 13, 2008. In both cases, a maser feature was detected at V LSR = 9 km/s, with peak flux densities of 35 and 15 Jy, respectively. After the its apparent absence in April, H2O maser emission reappeared on May 14, 2008, at V LSR = 7 km/s with a flux density of about 15 Jy. The history of previous observations of the object in the OH and H2O lines is traced. The maser displays strong and rapid flux variability in the lines of both molecules, as is typical of young low-luminosity stellar objects at early stages of their evolution.  相似文献   

15.
Our long-time monitoring of the B[e] star and transient X-ray source CI Cam during quiescence following the 1998 outburst demonstrates that the complex, stratified circumstellar envelope has tended to stabilize after this structure was perturbed by the passage of a shock wave from the outburst. The star’s U BV R brightness shows slow, possibly cyclic, variations with an amplitude of about 0.2m. We determined the spectral type of the primary, B4III-V, based on the widths of the absorption wings of high-numbered Balmer lines. A Doppler shift of 460 km/s was detected for the Hell λ4686 Å emission line. The shifts in this line yield an orbital period of 19.41 days, which is also manifested itself in the photometric data as a wave with a V amplitude of 0.034m. The orbit is elliptical, with an eccentricity of 0.62. It is most likely that the secondary is a white dwarf surrounded by an accretion disk. The primary’s mass exceeds 12 M ⊙ . The system may be at a late stage of its evolution, after the stage of mass exchange.  相似文献   

16.
Radio interferometric observations of an H2O maser flare in the Orion Nebula at epoch 1982.9 have been used to determine the flare’s spatial structure. Antennas in the Crimea, Effelsberg, and Onsala were used. The emission region consists of three groups of components. The angular sizes of the components are 0.2–0.9 mas, and the widths of the emitted lines are 0.2–0.7 km/s. The velocities of the components are correlated with their relative positions, which correspond to expanding concentric rings. Assuming a 1 M⊙ protostar in a Keplerian approximation, the radius of the inner ring R is 15 AU, the velocity of its rotation Vrot is 8.98 km/s, and the radial component of the velocity Vrad is 1.79 km/s. For the outer ring, R=15.7 AU, Vrot=8.79 km/s, and Vrad=2.61 km/s.  相似文献   

17.
We present the results of our CCD photometric and moderate-dispersion spectroscopic observations of the binary system V4641 Sgr, which contains a black hole of mass ≈9.5M⊙ and a normal B9III star. The photometric light curve reveals an ellipticity effect with very high amplitudes in V and R, 0.40m and 0.37m, and the color curve shows that the surface temperature is nonuniform. All this testifies to tidal distortion of the normal star's surface due to the massive companion and to a high inclination of the orbit to the line of sight. In June and July 2002, during quiescence, we obtained data during three flares with amplitudes up to 0.26m. In particular, spectroscopic observations were acquired near the time of the black hole's inferior conjunction. One hour before conjunction, a depression by EW=0.5 Å was observed in the red wing of the Hα absorption line, interpreted as absorption by gas flowing in the direction from the observer toward the normal star. This flow is apparently associated with a rarefied gas disk around the black hole, and the conjunction grazes the stellar surface if the orbital inclination is close to 70.7°. The maximum velocity along a circular Keplerian orbit is 650 km/s at a distance of R=0.15–0.20a from the black hole (where a is the component separation). Thus, we find the mass of the black hole to be M BH =7.1–9.5M⊙, confirming the model of Orosz et al. (2001).  相似文献   

18.
AIA/SDO data in the 193 Å channel preceding a coronal mass ejection observed at the solar limb on June 13, 2010 are used to simultaneously identify and examine two different shock fronts. The angular size of each front relative to the CME center was about 20°, and their propagation directions differed by ≈25° (≈4° in position angle). The faster front, called the blast shock, advanced the other front, called the piston shock, by R ≈ (0.02-0.03)R⊙ (R⊙ is the solar radius) and had a maximum initial speed of VB ≈ 850 km/s (with VP ≈ 700 km/s for the piston shock). The appearance and motion of these shocks were accompanied by a Type II radio burst observed at the fundamental frequency F and second harmonic H. Each frequency was split into two close frequencies f1 and f2 separated by Δf = f2 - f1 ? F, H. It is concluded that the observed frequency splitting Δf of the F and H components of the Type II burst could result from the simultaneous propagation of piston and blast shocks moving with different speeds in somewhat different directions displaying different coronal-plasma densities.  相似文献   

19.
The atmospheric abundances of 30 chemical elements in the halo star HD 221170 are analyzed by fitting synthetic spectra to observed spectra (i) with a resolution of 60 000 and signal-to-noise ratios of about 200 taken with the 1.93-m telescope of the Observatoire de Haute Provence and (ii) with a resolution of 35 000 and signal-to-noise ratios of more than 100 taken with the 2-m telescope of the Terskol Peak Observatory. The derived parameters of the stellar atmosphere are Teff=4475 K, log g=1.0, [Fe/H]=?2.03, Vmicro=1.7 km/s, and Vmacro=4 km/s. The parameters Teff, log g, [Fe/H], and Vmicro can be determined by analyzing the variations of the rms error of the mean iron abundance derived using different model atmospheres. The chemical composition of the star’s atmosphere is analyzed. The abundances of a total of 35 elements in HD 221170 have been derived in this paper and in previous studies. Overall, the abundances of elements lighter than praseodymium are consistent with the elemental abundances in the atmospheres of stars with similar metal deficits. Copper and manganese are underabundant by ?2.9 and ?2.6 dex, respectively, relative to the Sun (when the analysis includes the effects of hyperfine structure). Heavy r-process elements (starting from praseodymium) are overabundant compared to iron-group elements. This can be explained by an enrichment in r-process elements of the material from which the star was formed.  相似文献   

20.
Results of observations of the H2O maser in S269 carried out from October 1980 to February 2001 on the 22-m telescope (RT-22) of the Pushchino Radio Astronomy Observatory are presented. During the monitoring of S269, variability of the integrated flux of the maser emission with a cyclic character and an average period of 5.7 years was observed. This may be connected with cyclic activity of the central star during its formation. Emission at radial velocities of 4–7 km/s was detected. Thus, the H2O maser emission in S269 extends from 4 to 22 km/s, and is concentrated in three radial-velocity intervals: 4–7, 11–14, and 14–22 km/s. In some time intervals, the main group of emission features (14–22 km/s) had a triplet structure. The central velocity of the total spectrum is close to the velocity of the CO molecular cloud and HII region, differing from it by an amount that is within the probable dispersion of the turbulent gas velocities in the core of the CO molecular cloud. A radial-velocity drift of the component at V LSR≈20 km/s with a period of ≈26 years has been detected. This drift is likely due to turbulent (vortical) motions of material.  相似文献   

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