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1.
During the period 1979–1999, we investigated the hyperfine structure of the H2O supermaser region located in the core of the molecular cloud OMC-1 in Orion KL. The angular resolution is 0.1 mas, which corresponds to 0.045 AU. The detected structure, which consists of a central object, an accretion disk, a bipolar outflow, and an envelope, corresponds to the initial formation stage of a low-mass star. The accretion disk is at the stage of separation into groups of concentric rings. The bipolar outflow is a neutral, highly collimated jet of accreted material that includes H2O molecules and dust grains in the icy envelope. The injector is a bright compact source with a size <0.05 AU and a brightness temperature Tb≈1017 K. The velocity of the bipolar outflow is v≈10 km s?1. The rotation velocity of the jet is vrot≈1.5 km s?1. The jet has the shape of a conical helix due to the precession of the rotation axis. Occasionally, dense blobs (comet-shaped bullets) are ejected. The envelope amplifies the radio emission from the structures in a ～0.5 km s?1 maser window band with velocities v≈7.65 km s?1 by more than two orders of magnitude.  相似文献   

2.
We analyze the superfine structure of the supermaser H2O emission region in Orion KL over the period 1979–1999. The angular resolution reached 0.1 mas, which corresponds to 0.045 AU at a distance to Orion KL of 450 pc. We determined the velocity of the local standard of rest, VLSR = 7.65 km s?1. The formation of a protostar is accompanied by a structure that consists of an accretion disk, a bipolar outflow, and a surrounding envelope. The disk is at the stage of separation into protoplanetary rings. The disk plane is warped like the brim of a hat. The disk is 27 AU in diameter and ～0.3 AU in thickness. The rings contain ice granules. Radiation and stellar wind sublimate and blow away the water molecules to form halos around the rings, maser rings. The radiation from the rings is concentrated in the azimuthal plane, and its directivity reaches 10?3. The relative velocities of the rings located in the central part of the disk 15 AU in diameter correspond to rigid-body rotation, Vrot = ΩR. The rotation period is T ≈ 170 yr. The injector is surrounded by a toroidal structure 1.2 AU in diameter. The diameter of the injected flow does not exceed 0.05 AU. A highly collimated bipolar outflow with a diameter of ～0.1 AU is observed at a distance as large as 3 AU. Precession of the injector axis with a period of ～10 yr forms a spiral flow structure. The flow velocity is ～10 km s?1. The kinetic energy of the accreting matter and the disk is assumed to be transferred to the bipolar outflow, causing the rotation velocity distribution of the rings to deviate from the Keplerian velocity. The surrounding envelope amplifies the emission from the structure at a velocity of 7.65 km s?1 in a band of ～0.5 km s?1 by more than two orders of magnitude, which determines the supermaser emission.  相似文献   

3.
The superfine structure of the bulge of the galaxy NGC 4258 has been investigated in H2O maser emission at the epochs on February 4, 2013, and November 29, 2013. The peak intensities of the spectral components reached F ≈ 5 Jy. The emission of the component at v = 476 km s-1 dominated at the beginning of this period; the second component at v = 487 km s-1 was observed at the end of the period. The structure is a chain of compact components up to 200 µas or 7mpc in extent. The velocity of the local standard of rest is v LSR = 482 km s-1. Two bright compact components with a separation between them Δρ ≈ 35 µas or 1.3 mpc and a pair of components spaced 13 µas apart, whose brightness reaches 30% of the peak value corresponding to a brightness temperature T b ≈ 1018 K, are located at the center. The sizes of the components are ~2–3 µas. A splitting and a shift of the two pairs of components relative to each other by 8 µas or 0.3 mpc in the 45° direction are observed at the end of the period. The velocity gradient of the structure is dV/dρ = 224 km s-1 mas-1, suggesting a solid-body rotation with a period T ≈ 760 years. The compact components correspond to the tangential directions of the arm. Two parallel chains of components corresponding to the tangential directions of the walls of the bipolar outflow carrying away an excess angular momentum are ejected from the central part of the bulge, two sources. The outflow is oriented at an angle X ≈ 15° relative to the disk axis. The brightness of the outflow fragments does not exceed 1.5% of the peak value. The ejection of material from the central part in the northward direction at a level up to 0.2%, T b ≈ 1015 K, is observed at the epoch on February 4, 2013, at v = 478 km s-1. The core structure suggests a double system: parallel disks–vortices spaced 0.25 mpc apart.  相似文献   

4.
The extra fine structure of the active region of H2O supermaser emission of Orion KL (angular resolution is 0.1 mas) is studied. A central body / accretion disk / bipolar outflow / bullets / envelope is discovered, that corresponds to the earliest stage of the small-mass star formation. The ejector – a compact bright source ≤0.05 AU, Tb ≈ 1017K. The bipolar outflow, vej ≈ 10km/s is a highly-collimated stream with a ration length/diameter～ 60, rotation period is ～ 0.5 yr, precession period ～ 10 yrs, precession angle ～ 33°. Precession forms a conical helix jet. The envelope amplified radio emission by about three orders of magnitude at velocity at v=7.65 km/s.  相似文献   

5.
We analyze the spectra of DR Tau in the wavelength range 1200 to 3100 Å obtained with the GHRS and STIS spectrographs from the Hubble Space Telescope. The profiles for the C IV 1550 and He II 1640 emission lines and for the absorption features of some lines indicate that matter falls to the star at a velocity ～300 km s?1. At the same time, absorption features were detected in the blue wings of the N I, Mg I, Fe II, Mg II, C II, and Si II lines, suggesting mass outflow at a velocity up to 400 km s?1. The C II, Si II, and Al II intercombination lines exhibit symmetric profiles whose peaks have the same radial velocity as the star. This is also true for the emission features of the Fe II and H2 lines. We believe that stellar activity is attributable to disk accretion of circumstellar matter, with matter reaching the star mainly through the disk and the boundary layer. At the time of observations, the accretion luminosity was Lac ? 2L⊙ at an accretion rate ?10?7M⊙ yr?1. Concurrently, a small (<10%) fraction of matter falls to the star along magnetospheric magnetic field lines from a height ～R*. Within a region of size ?3.5R*, the disk atmosphere has a thickness ～0.1R* and a temperature ?1.5 × 104 K. We assume that disk rotation in this region significantly differs from Keplerian rotation. The molecular hydrogen lines are formed in the disk at a distance <1.4 AU from the star. Accretion is accompanied by mass outflow from the accretion-disk surface. In a region of size <10R*, the wind gas has a temperature ～7000 K, but at the same time, almost all iron is singly ionized by H I L α photons from inner disk regions. Where the warm-wind velocity reaches ?400 km s?1, the gas moves at an angle of no less than 30° to the disk plane. We found no evidence of regions with a temperature above 104 K in the wind and leave open the question of whether there is outflow in the H2 line formation region. According to our estimate, the star has the following set of parameters: M* ? 0.9M⊙, R* ? 1.8R⊙, L* ? 0.9L⊙, and \(A_V \simeq 0\mathop .\limits^m 9\). The inclination i of the disk axis to the line of sight cannot be very small; however, i≤60°.  相似文献   

6.
We present the results of our study of the poorly known B[e] star AS 160=IRAS 07370-2438. The high-resolution spectrum obtained with the 6-m BTA telescope exhibits strong emission in the Hα line with a two-component profile, indicating that the gaseous envelope of the star is nonspherical. Previously nonanalyzed photometric data suggest the presence of a compact dust envelope. The fundamental parameters of the star (log L/L⊙ = 4.4 ± 0.2, v sin i = 200 km s?1 and its distance (3.5±0.5 kpc) have been determined for the first time and are in agreement with published estimates of the MK spectral type of the object (B1.5 V:). Analysis of the object's properties leads us to suggest that this is a binary system that belongs to our recently identified type of Be stars with warm dust.  相似文献   

7.
The superfine structure of the active region in Orion KL has been investigated in the H2O maser line at two epochs, December 23, 1998, and April 24, 1999, with an angular resolution as high as 0.01 mas. A bright central source, a bipolar outflow ejector with two nozzles spaced 0.008 mas apart, has been identified. The impact of the ejected flows causes precession of the rotation axis and gives rise to a jet structure in the shape of diverging helixes of opposite signs. The longitudinal velocities of the flows differ by 0.12 km s?1. The flow emission at the exit from the nozzles is linearly polarized and oriented at an angle of 22° relative to the rotation axis or parallel to the flow velocities. Their brightness temperature exceeds T b > 1018 K. The width of the emission line profiles is 0.43 km s?1, their relative shift is ±0.06 km s?1, and the orientations of the polarization planes differ by 45°, which determines the extraordinary rotation of the polarization plane, 25°/km s?1.  相似文献   

8.
We present the results of the reduction of our photometric and spectroscopic observations for the eclipsing binary SZ Cam performed with the telescopes at the Astronomical Observatory of the Ural Federal University and the Special Astrophysical Observatory of the Russian Academy of Sciences in 1996–2014. Based on an 11-year-long photometric monitoring of SZ Cam, we have obtained new elements of its photometric orbit and parameters of its components. We have detected low-amplitude periodic light variations in SZ Cam that are possibly related to the ellipsoidal shape of the components of the spectroscopic binary third body. Based on published data and our new spectroscopy, we have found new values for the mass ratio, q = 0.72 ± 0.01, and parameters of the radial velocity curves of the components, V 0 = ?3.6 ± 1.7 km s?1, K 1 = 190.2 ± 1.9 km s?1, and K 2 = 263.0 ± 2.4 km s?1. The component masses have been estimated to be M 1 = 16.1 M ⊙ and M 2 = 11.6 M ⊙. We have obtained new light elements and parameters of the radial velocity curves for the third body, V 0 3b = 4.2 ± 0.6 km s?1 and K 1 3b = 26.6 ± 0.8 km s?1. We have improved the period of the relative orbit of SZ Cam and the third body, P orb = 55.6 ± 1.5 yr.  相似文献   

9.
We consider stars with radial velocities, proper motions, and distance estimates from the RAVE4 catalogue. Based on a sample of more than 145 000 stars at distances r < 0.5 kpc, we have found the following kinematic parameters: \({\left( {U,{\kern 1pt} V,{\kern 1pt} W} \right)_ \odot }\) = (9.12, 20.80, 7.66) ± (0.10, 0.10, 0.08) km s?1, Ω0 = 28.71 ± 0.63 km s?1 kpc?1, and Ω0 ’ = ?4.28 ± 0.11 km s?1 kpc?2. This gives the linear rotation velocity V 0 = 230 ± 12 km s?1 (for the adopted R 0 = 8.0 ± 0.4 kpc) and the Oort constants A = 17.12 ± 0.45 km s?1 kpc?1 and B = ?11.60 ± 0.77 km s?1 kpc?1. The 2D velocity distributions in the UV, UW, and VW planes have been constructed using a local sample, r < 0.25 kpc, consisting of ~47 000 stars. A difference of the UV velocity distribution from the previously known ones constructed from a smaller amount of data has been revealed. It lies in the fact that our distribution has an extremely enhanced branch near the Wolf 630 peak. A previously unknown peak at (U, V) = (?96, ?10) km s?1 and a separate new feature in the Wolf 630 stream, with the coordinates of its center being (U, V) = (30, ?40) km s?1, have been detected.  相似文献   

10.
We present the results of JHKLM-photometry for the symbiotic Mira star candidate V 335 Vul. Based on the average flux data, supplemented by IRAS, MSX, AKARI, and WISE mid-IR observations, we calculated a model of a spherically symmetric dust envelope of the star, made up of amorphous carbon and silicon carbide particles. The optical depth of the envelope in the visible range with a dust temperature at the inner boundary of T1 = 1300 K is τ V = 0.58. For an envelope expansion velocity of 26.5 km s?1, the estimated mass loss rate is equal to 5.7 × 10?7M⊙ yr?1.  相似文献   

11.
We perform a kinematic analysis of the Hipparcos and TRC proper motions of stars by using a linear Ogorodnikov-Milne model. All of the distant (r>0.2 kpc) stars of the Hipparcos catalog have been found to rotate around the Galactic y axis with an angular velocity of M 13 ? =?0.36±0.09 mas yr?1. One of the causes of this rotation may be an uncertainty in the lunisolar precession constant adopted when constructing the ICRS. In this case, the correction to the IAU (1976) lunisolar precession constant in longitude is shown to be Δp1=?3.26±0.10 mas yr?1. Based on the TRC catalog, we have determined the mean Oort constants: A=14.9±1.0 and B=?10.8±0.3 km s?1 kpc?1. The component of the model that describes the rotation of all TRC stars around the Galactic y axis is nonzero for all magnitudes, M 13 ? =?0.86±0.11 mas yr?1.  相似文献   

12.
Polarization measurements of the H2O maser emission from the active region in Orion KL were carried out at epoch 2011?C2012 on the Svetloe-Zelenchukskaya radio interferometer. The bipolar outflow structure and polarized emission parameters have been determined. The emission from the components at v = 7.6 and 7.0 km s?1 dominates in the line profile; the relative contribution of the former component has increased. The velocity of the bipolar outflow ejector region is almost equal to that of the local standard of rest v LSR = 7.65 km s?1, while the velocity of the remote component is v = 7.0 km s?1. The emission from the bipolar outflow is observed at a distance up to 11 mas from the ejector. Its diameter does not exceed 0.3 mas. The outflow orientation in the plane of the sky is ?37°. The outflow velocity components along the line of sight differ by ??v = 0.3 km s?1. The polarization levels of the bipolar outflow and the remote component reach m = 62 and 39%, respectively.  相似文献   

13.
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14.
In this paper of the series we analyze three stars listed among stars with discrepant v sin i: HD9531 and HD31592, which also show radial velocity variations inherent to spectroscopic binaries, and HD129174 which is an Mn-type star with a possible magnetic field. In HD9531 we confirm the radial velocity derived fromthe hydrogen lines as well as fromthe Ca II line at 3933 Å as variable. The profile of the calcium line also appears variable, and with the estimated magnetic induction Be = ?630 ± 1340 G, this suggests that the abundance of calcium possibly varies over the surface of the star. We identified the lines of the secondary component in the spectrum of HD31592 revealing thus it is an SB2 binary with B9.5V and A0V components. While the primary star rotates with v sin i = 50 km s?1, the secondary star is faster with v sin i = 170 km s?1. We find that only 60% of the Mn lines identified in the spectrum of HD129174 can be fitted with a unique abundance value, whereas the remaining lines are stronger or fainter. We also identified two Xe II lines at 5339.33 Å and 5419.15 Å and estimated their log g f.  相似文献   

15.
Photometric and spectroscopic observations of the nearby type-IIP supernova 2004dj are presented. The 56Ni mass in the envelope of SN 2004dj was estimated from the light curve to be ≈0.02M⊙. This estimate is confirmed by modeling the Hα luminosity. The Hα emission line exhibits a strong asymmetry characterized by the presence of a blue component in the line with a shift of ?1600 km s?1 at the early nebular phase. A similar asymmetry was found in the Hβ, [O I], and [Ca II] lines. The line asymmetry is interpreted as being the result of asymmetric 56Ni ejecta. The Hα profile and its evolution are reproduced in the model of an asymmetric bipolar 56Ni structure for a spherical hydrogen distribution. The mass of the front 56Ni jet is comparable to that of the central component and twice that of the rear 56Ni jet. We point out that the asymmetric bipolar structure of 56Ni ejecta is also present in SN 1999em, a normal type-IIP supernova.  相似文献   

16.
We have selected and analyzed a sample of OB stars with known line-of-sight velocities determined through ground-based observations and with trigonometric parallaxes and propermotions from the Gaia DR2 catalogue. Some of the stars in our sample have distance estimates made from calcium lines. A direct comparison with the trigonometric distance scale has shown that the calcium distance scale should be reduced by 13%. The following parameters of the Galactic rotation curve have been determined from 495 OB stars with relative parallax errors less than 30%: (U, V,W)⊙ = (8.16, 11.19, 8.55)± (0.48, 0.56, 0.48) km s?1, Ω0 = 28.92 ± 0.39 km s?1 kpc?1, Ω'0 = ?4.087 ± 0.083 km s?1 kpc?2, and Ω″ 0 = 0.703 ± 0.067 km s?1 kpc?3, where the circular velocity of the local standard of rest is V0 = 231 ± 5 km s?1 (for the adopted R0 = 8.0 ± 0.15 kpc). The parameters of the Galactic spiral density wave have been found from the series of radial, VR, residual tangential, ΔVcirc, and vertical, W, velocities of OB stars by applying a periodogram analysis. The amplitudes of the radial, tangential, and vertical velocity perturbations are fR = 7.1± 0.3 km s?1, fθ = 6.5 ± 0.4 km s?1, and fW = 4.8± 0.8 km s?1, respectively; the perturbation wavelengths are λR = 3.3 ± 0.1 kpc, λθ = 2.3 ± 0.2 kpc, and λW = 2.6 ± 0.5 kpc; and the Sun’s radial phase in the spiral density wave is (χ⊙)R = ?135? ± 5?, (χ⊙)θ = ?123? ± 8?, and (χ⊙)W = ?132? ± 21? for the adopted four-armed spiral pattern.  相似文献   

17.
We consider two samples of OB stars with different distance scales that we have studied previously. The first and second samples consist of massive spectroscopic binaries with photometric distances and distances determined from interstellar calcium lines, respectively. The OB stars are located at heliocentric distances up to 7 kpc. We have identified them with the Gaia DR1 catalogue. Using the proper motions taken from the Gaia DR1 catalogue is shown to reduce the random errors in the Galactic rotation parameters compared to the previously known results. By analyzing the proper motions and parallaxes of 208 OB stars from the Gaia DR1 catalogue with a relative parallax error of less than 200%, we have found the following kinematic parameters: (U, V)⊙ = (8.67, 6.63)± (0.88, 0.98) km s?1, Ω0 = 27.35 ± 0.77 km s?1 kpc?1, Ω′0 = ?4.13 ± 0.13 km s?1 kpc?2, and Ω″0 = 0.672 ± 0.070 km s?1 kpc?3, the Oort constants are A = ?16.53 ± 0.52 km s?1 kpc?1 and B = 10.82 ± 0.93 km s?1 kpc?1, and the linear circular rotation velocity of the local standard of rest around the Galactic rotation axis is V 0 = 219 ± 8 km s?1 for the adopted R 0 = 8.0 ± 0.2 kpc. Based on the same stars, we have derived the rotation parameters only from their line-of-sight velocities. By comparing the estimated values of Ω′0, we have found the distance scale factor for the Gaia DR1 catalogue to be close to unity: 0.96. Based on 238 OB stars of the combined sample with photometric distances for the stars of the first sample and distances in the calcium distance scale for the stars of the second sample, line-of-sight velocities, and proper motions from the Gaia DR1 catalogue, we have found the following kinematic parameters: (U, V, W)⊙ = (8.19, 9.28, 8.79)± (0.74, 0.92, 0.74) km s?1, Ω0 = 31.53 ± 0.54 km s?1 kpc?1, Ω′0 = ?4.44 ± 0.12 km s?1 kpc?2, and Ω″0 = 0.706 ± 0.100 km s?1 kpc?3; here, A = ?17.77 ± 0.46 km s?1 kpc?1, B = 13.76 ± 0.71 km s?1 kpc?1, and V 0 = 252 ± 8 km s?1.  相似文献   

18.
Open star clusters from the MWSC (Milky Way Star Clusters) catalogue have been used to determine the Galactic rotation parameters. The circular rotation velocity of the solar neighborhood around the Galactic center has been found from data on more than 2000 clusters of various ages to be V 0 = 236 ± 6 km s?1 for the adopted Galactocentric distance of the Sun R 0 = 8.3 ± 0.2 kpc. The derived angular velocity parameters are Ω 0 = 28.48 ± 0.36 km s?1 kpc?1, Ω’0 = ?3.50 ± 0.08 km s?1 kpc?2, and Ω″0 = 0.331 ± 0.037 km s?1 kpc?3. The influence of the spiral density wave has been detected only in the sample of clusters younger than 50 Myr. For these clusters the amplitudes of the tangential and radial velocity perturbations are f θ = 5.6 ± 1.6 km s?1 and f R = 7.7 ± 1.4 km s?1, respectively; the perturbation wavelengths are λ θ = 2.6 ± 0.5 kpc (i θ = ?11? ± 2?) and λ R = 2.1 ± 0.5 kpc (i R = ?9? ± 2?) for the adopted four-armed model (m = 4). The Sun’s phase in the spiral density wave is (χ⊙)θ = ?62? ± 9? and (χ⊙)R = ?85? ± 10? from the residual tangential and radial velocities, respectively.  相似文献   

19.
A sample of classical Cepheids with known distances and line-of-sight velocities has been supplemented with proper motions from the Gaia DR1 catalogue. Based on the velocities of 260 stars, we have found the components of the peculiar solar velocity vector (U, V, W)⊙ = (7.90, 11.73, 7.39) ± (0.65, 0.77, 0.62) km s?1 and the following parameters of the Galactic rotation curve: Ω0 = 28.84 ± 0.33 km s?1 kpc?1, Ω′0 = ?4.05 ± 0.10 km s?1 kpc?2, and Ω″0 = 0.805 ± 0.067 km s?1 kpc?3 for the adopted solar Galactocentric distance R 0 = 8 kpc; the linear rotation velocity of the local standard of rest is V 0 = 231 ± 6 km s?1.  相似文献   

20.
The evolution of a Population-I star with an initial mass M ZAMS = 60 M ⊙ has been calculated. At the stage when a red giant turns into an early-type helium star, the vast bulk of the stellar mass is concentrated in a compact core surrounded by an extended envelope that is unstable with respect to radial oscillations. The range of effective temperatures within which the instability arises extends to T eff ? 105 K. For the models corresponding to the Wolf-Rayet evolutionary stage (5 × 104 K ≤ T eff ≤ 1.05 × 105 K), hydrodynamic calculations of self-exciting radial stellar pulsations have been performed. The pulsational instability develops in a time interval comparable to the dynamic timescale. Once the amplitude has ceased to grow, the pulsational motions are nonlinear traveling waves propagating from the core boundary to the stellar surface. The velocity amplitude of the outer layers is 500 km s?1 < ΔU < 103 km s?1, depending on the effective temperature. During the evolution of a helium star, the mean ratio of the maximum expansion velocity of the outer layers to the local escape velocity decreases and lies within the range 0.25 < U max/v esc < 0.6 for the models considered. The nonlinearity of the stellar pulsations is responsible for the increase in the mean radius \(\bar r\) of the Lagrangian layers compared to the equilibrium radius r eq. The effect of the increase in mean radius decreases with rising effective temperature from\(\bar r\)/r ～ 10 at T eff = 7 × 104 K to \(\bar r\)/r ≈ 2 at T eff = 105 K. The radial pulsation periods for the models considered lie within the range 0.1 day ≤ Π ≤ 1.6 day and the amplitude of the bolometric magnitude variations does not exceed 0 . m 2.  相似文献   

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