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1.
We have performed speckle interferometry with the 6-m telescope of the Special Astrophysical Observatory and spectroscopy (at 3700–9200 Å) with the 2-m telescope at Peak Terskol of the spectroscopic and interferometric binary 9 Cyg, which is a composite-spectrum star with an orbital period of 4.3 yrs. The atmosphere of the system’s primary component is analyzed in detail. The luminosities of both components estimated to be L 1 = 103.8 L ⊙, L 2 = 55.2 L ⊙, where L ⊙ is the solar luminosity, and their effective temperatures to be T e (1) = 5300 K and T e (2) = 9400 K. The abundances of C, N, O, Fe, and other elements in the primary’s atmosphere have been derived. The chemical composition shows signatures of mixing of material from its atmosphere and the region of nuclear reactions. The evolutionary status of 9 Cyg has been determined. The binary’s age is about 400 million years; the brighter star is already in the transition to becoming a red giant, while the secondary is still in the hydrogen-burning stage near the zero-age main sequence. We suggest an evolutionary model for the binary’s orbit that explains the high eccentricity, e = 0.79. 相似文献
2.
Data from the revised Geneva-Copenhagen catalog are used to study the influence of radial migration of stars on the age dependences
of parameters of the velocity ellipsoids for nearby stars in the thin disk of the Galaxy, assuming that the mean radii of
the stellar orbits remain constant. It is demonstrated that precisely the radial migration of stars, together with the negative
metallicity gradient in the thin disk, are responsible for the observed negative correlation between the metallicities and
angular momenta of nearby stars, while the angular momenta of stars that were born at the same Galactocentric distances do
not depend on either age or metallicity. The velocity components of the Sun relative to the Local Standard of Rest derived
using data for stars born at the solar Galactocentric distance are (U
⊙, V
⊙, W
⊙)
LSR
= (5.1 ± 0.4, 7.9 ± 0.5, 7.7 ± 0.2) km/s. The two coordinates of the apex of the solar motion remain equal to 〈l
⊙〉 = 70° ± 7° and 〈b
⊙〉 = 41° ± 2°, within the errors. The indices for the power-law age dependences of them ajor, middle, and minor semi-axes become
0.26±0.04, 0.32±0.03, and 0.07±0.03, respectively. As a result, with age, the velocity ellipsoid for thin-disk stars born
at the solar Galactocentric distance increases only in the plane of the disk, remaining virtually constant in the perpendicular
direction. Its shape remains far from equilibrium, and the direction of the major axis does not change with age: the ellipsoid
vertex deviation remains constant and equal to zero within the errors (〈L〉 = 0.7° ± 0.6°, 〈B〉 = 1.9° ± 1.1°). Such a small increase in the velocity dispersion perpendicular to the Galactic plane with age can probably
be explained by “heating” of the stellar system purely by spiral density waves, without a contribution from giant molecular
clouds. 相似文献
3.
E. P. Kurbatov 《Astronomy Reports》2010,54(7):590-598
The ejection of stars from spheroidal and disk dwarf galaxies resulting from the decay of OB associations is studied. This
has substantial observational consequences for disk galaxies with escape velocities up to 20 km/s, or dynamical masses up
to 108
M
⊙. The ejection of stars can (i) reduce the abundances of the products of Type Ia supernovae and, to a lesser degree, Type
II supernovae, in disk stars, (ii) chemically enrich the galactic halo and intergalactic medium, (iii) lead to the loss of
50% of the stellar mass in galaxies with masses ∼107
M
⊙ and the loss of all stars in systems with masses ≲105
M
⊙, (iv) increase the mass-to-luminosity ratio of the galaxy. 相似文献
4.
Results of JHKLM photometry for the protoplanetary nebula candidate V1027 Cyg obtained in 1991–2008 are reported. In all bands, the brightness
variations did not exceed 0.2
m
. Estimated linear trends demonstrate no significant changes in the mean brightness and color indices of the object, with
the possible exception of the L-M color index, which showed a small decrease. A search for possible periodicities in the brightness variations yielded the
most probable period of 237d. A model for a spherically-symmetric dust shell has been calculated based on the photometric results supplemented with data
on the mid- and far-infrared fluxes. The estimated mass-loss rate of the star is 1.3 × 10−5
M
⊙/year. 相似文献
5.
S. Feth G. V. Gibbs M. B. Boisen Jr. F. C. Hill 《Physics and Chemistry of Minerals》1998,25(3):234-241
Bond critical point properties calculated for the MN bonds in a number of geometry optimized nitride molecules containing first- and second-row M cations are compared with those calculated for a number of oxide molecules. As reported for the oxides, the value of the
electron density, ρ(r
c
), at the bond critical points, r
c
, increases with decreasing bond length while for the more electronegative cations, the local energy density, H(r
c
) decreases nonlinearly in value as the relative electronegativities of the M-cations, χ
M
, tend to increase. In the majority of cases, χM, |λ1|/λ3 and ∇2ρ(r
c
) increase with decreasing minimum energy bond lengths. The bond lengths adopted by the molecules are indicated to be an important
determinant of the critical point properties of the electron density distributions. The relative electronegativities derived
from the electron density distributions of the nitrides agree with those derived for the oxides and Pauling’s electronegativities
to within ∼5%, on average.
Received: 3 February 1997 / Revised, accepted: 11 July 1997 相似文献
6.
Ashwani Kumar S. C. Gupta A. K. Jindal Sanjay Jain Vandana 《Journal of Earth System Science》2003,112(3):391-395
Following a large-sized Bhuj earthquake (M
s = 7.6) of January 26th, 2001, a small aperture 4-station temporary local network was deployed, in the epicentral area, for
a period of about three weeks and resulted in the recording of more than 1800 aftershocks (-0.07 ≤M
L <5.0). Preliminary locations of epicenters of 297 aftershocks (2.0 ≤M
L <5.0) have brought out a dense cluster of aftershock activity, the center of which falls 20 km NW of Bhachau. Epicentral
locations of after-shocks encompass a surface area of about 50 × 40 km2 that seems to indicate the surface projection of the rupture area associated with the earthquake. The distribution of aftershock
activity above magnitude 3, shows that aftershocks are nonuniformly distributed and are aligned in the north, northwest and
northeast directions. The epicenter of the mainshock falls on the southern edge of the delineated zone of aftershock activity
and the maximum clustering of activity occurs in close proximity of the mainshock. Well-constrained focal depths of 122 aftershocks
show that 89% of the aftershocks occurred at depths ranging between 6 and 25 km and only 7% and 4% aftershocks occur at depths
less than 5 and more than 25 km respectively. The Gutenberg-Richter (GR) relationship, logN = 4.52 - 0.89ML, is fitted to the aftershock data (1.0<-M
L<5.0) and theb-value of 0.89 has been estimated for the aftershock activity. 相似文献
7.
An analysis of SOHO/LASCO C3 data shows that there are discontinuities in the radial profiles of the plasma density within limited regions in front of
each of ten coronal mass ejections, which represent shocks. The shock velocities in various events reach V ≈ 800–2500 km/s. A comparison of the dependence of the AlfvenicMach numberM
A
on the shock strength ρ
2/ρ
1 detected at distancesR > 10R⊙ from the center of the Sun with calculations carried out using ideal magnetic hydrodynamics shows that the effective ratio
of specific heats γ describing processes inside the shock front varies from 2 to 5/3 (ρ
1 and ρ
2 are the densities in front of and behind the shock, and R⊙ is the solar radius). This corresponds to an effective number of degrees of freedom between two and three. A similar dependenceMA(ρ
2
/ρ
1) was found for near-Earth bow shocks and interplanetary collisionless shocks. These features support the hypothesis that
the studied discontinuities preceding coronal mass ejections are collisionless shocks. 相似文献
8.
Results of numerical simulations of a collision of the gaseous components of two identical disk galaxies during a head-on
collision of the galaxies in the polar direction are presented. When the relative velocity of the galaxy collision is small,
their gaseous components merge. At high relative velocities (100–500 km/s), the massive stellar components of the galaxies
(M
g
= 109
M
⊙) pass through each other nearly freely, leaving behind the gaseous components, which are decelerated and heated by the collision.
If the overall gaseous component of the colliding galaxies is able to cool to the virial temperature during the collision,
a new galaxy forms. At velocities V ≥ 500 km/s, the gaseous component does not have time to cool, and the gas is scattered into intergalactic space, supplying
it with heavy elements produced in supernovae in the colliding galaxies. High-velocity (V ≥ 100 km/s) collisions of identical low-mass galaxies (M
g
≤ 109
M
⊙) whose mass is dominated by the mass of gas lead to the disruption of their stellar components. The overall gaseous component
forms a new galaxy when V ≤ 500 km/s, and is scattered into intergalactic space if the velocity becomes higher than this. A galaxy collision increases
the star-formation rates in the disk galaxies by nearly a factor of 100. Rotation of the colliding galaxies in the same direction
increases the changes of the disruption of both the stellar and gaseous components of the galaxies. The merger of galaxies
during their collision can explain the presence of gaseous disks rotating opposite to the rotation of the stellar component
in some ordinary elliptical galaxies. Moreover, galaxy mergers can help explain the origin of a comparatively young stellar
population in some elliptical galaxies. 相似文献
9.
We present images of the star-forming regionG23.01–0.41 at 6.7GHz in the Class II methanol maser transition 51–60
A
+, produced from archival observations on the European VLBI Network. Our map of the source and its maser spots contains 24
maser components. The data for each spot—absolute coordinates, coordinates relative to the calibration feature, peak flux
and flux integrated over the spot, size, position angle, velocity along the line of sight, and line full width at half-maximum—are
collected in tabular form. The spatial region occupied by the maser spots is approximated by a 200×130 milliarcsec ellipse
in position angle PA = −0.40°, centered on the absolute coordinates α
0 = 18h34m40.282s, δ
0 = −09°00′38.27″ (J2000). If the source is a protoplanetary disk, then, for the distance estimate derived from trigonometric
parallax, its diameter is 1800 AU, and the mass of the central protostar is 23.5M
⊙. 相似文献
10.
R. Ya. Zhuchkov E. V. Malogolovets O. V. Kiyaeva V. V. Orlov I. F. Bikmaev Yu. Yu. Balega 《Astronomy Reports》2012,56(7):512-523
We analyze the physical parameters, orbital elements, and dynamic stability of the multiple system ?? UMa (HD 76644 = ADS 7114). We have used the positions from the WDS catalog and our own observations on the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences and the 1.5-m Russian-Turkish Telescope (Antalya, Turkey). We have obtained more precise orbital parameters of the subsystems, and spectral types, absolute magnitudes, and masses of the components. The primary has Sp = F0 V?CIV, M = 1.7 ± 0.1M ??, T eff = 7260 ± 70 K, and log g = 4.30 ± 0.07. The companion in the close Aa subsystem is most likely a white dwarf with a mass of approximately 1.0 ± 0.3M ??. The spectral types and masses of the components in the BC subsystem are M3V, M4V and 0.35 ± 0.05M ??, 0.30 ± 0.05M ??, respectively. The total mass is 3.4 ± 0.4M ??. The Aa subsystem probably has an orbital period of 4470d = 12.2y and an eccentricity of approximately 0.6. The outer subsystem seems to have a period of approximately 2084 yrs and an eccentricity of approximately 0.9. We have carried out simulations using the stability criteria and shown that for all possible variations in the component parameters, the multiple system is unstable on a time scale of less than 106 years with a probability exceeding 0.98. Possible reasons for this instability are discussed. 相似文献
11.
The LTE lithium abundances, logN (Li), have been determined for the atmospheres of the four carbon giants AQ And, HK Lyr, UX Dra, and WZ Cas, applying the
synthetic-spectrum technique to the LiI λ670.8 nm resonance doublet. We used estimates of the effective temperatures T
eff, metallicities, elemental abundances, and carbon-isotope ratios for these stars from the literature [12C/13C]. The resulting
lithium abundances depend significantly on the adopted T
eff, so that we can find each star’s range of possible logN(Li) values for a given range of effective temperatures (ΔT
eff = 200−300 K). The uncertainty in the derived logN(Li) values is 1.3 for AQ And and UX Dra, 0.5 for HK Lyr, and 0.8 for WZ Cas. Our most probable logN(Li) values (or ranges) are −1.25 for AQ And, −1.2 for HK Lyr, −1.0 ≤ logN(Li) ≤ +0.3 for UX Dra, and 4.3 ≤ logN(Li) ≤ 4.8 for WZ Cas. The derived C/O ratios for the stellar atmospheres also depend on T
eff. Possible uncertainties in other atmospheric parameters do not change logN(Li) by more than 0.2. 相似文献
12.
13.
Possible paths for the formation of Ap/Bp stars—massive main-sequence stars with strong magnetic fields—are analyzed based
on modern theories for the evolution of single and binary stars. Assuming that the strong magnetic fields of these stars are
the main reason for their comparatively slow axial rotation and the observed anomalies in the chemical compositions of their
atmospheres, possible origins for these high magnetic fields are considered. Analysis of several possible scenarios for the
formation of these stars leads to the conclusion that their surface magnetic fields are probably generated in the convective
envelopes of the precursor stars. These precursors may be young, single stars with masses 1.5–3 M
⊙ that formed at the peripheries of forming star clusters and ended their accretion at the Hayashi boundary, or alternatively
close binaries whose components have convective envelopes, whose merger leads to the formation of an Ap/Bp star. Arguments
are presented supporting the view that the merger of close binaries is the main channel for the formation of Ap/Bp stars,
and a detailed analysis of this scenario is presented. The initial major axes of the merging binary systems must be in the
range 6–12 R
⊙, and the masses of their components in the range 0.7–1.5 M
⊙. When the merging components possess developed convective envelopes and fairly strong initial magnetic fields, these can
generate powerful magnetic fields “inherited” by the products of the merger—Ap/Bp stars. The reason the components of the
close binaries merge is a loss of angular momentum via the magnetic stellar winds of the components. 相似文献
14.
We present JHKLM photometry of the carbon stars ST And and T Lyn acquired in 2000–2010. Along with brightness variations due to pulsations,
changes on timescales of 2000–3000 days are also observed. Our combined light curves can be satisfactorily represented with
light elements derived from visual observations, but the maxima are delayed relative to the calculated times. A color-index
analysis demonstrates that the dust shell of ST And is fairly weak, and is manifest only episodically, while the presence
of hot dust was always detected for T Lyn. These results confirm models of spherically symmetric stellar dust shells based
on mean-flux data, supplemented with observations in the intermediate IR from the IRAS and AKARI satellites. The visual optical
depth of the relatively cool dust shell of ST And assuming a dust temperature at the inner edge of T
1 = 510 K is very low: τ
V = 0.047. The dust shell of T Lyn is considerably hotter (T
1 = 940 K), with τ
V = 0.95. We estimate the mass-loss rate to be 1.8 × 10−7
M
⊙/year for ST And and 3.7 × 10−7
M
⊙/year for T Lyn. 相似文献
15.
Based on 70 years of published photoelectric observations, we have detected quasi-periodic cophased oscillations of the times of the primary and secondary minima of RR Lyn, one of the brightest and nearest eclipsing binaries in the northern sky ( $V = 5\mathop m\limits_. 54$ ; r=74 pc). Approximating these oscillations using the light equation yields estimates of the orbital parameters of the third body in the system and imposes constraints on its mass, M 3. In the most probable case when the orbits of the eclipsing and triple systems are coplanar, M 3=1.10±0.02M ⊙, and the semimajor axis of the orbit A 3=17.4±3.5 AU, with a substantial eccentricity, e 3=0.96±0.02. We have carried out a detailed study of the apsidal rotation of this eclipsing and now multiple system, which was suggested by Koch as a test of general relativity as far back as 1973. Our high-precision W BV R photoelectric photometry $(\sigma _{obs} \cong 0\mathop m\limits_. 0032)$ has removed some contradictions. At the same time, the proximity of the longitude of periastron ω 180°; the close correlation between the jointly estimated values of ω, e and the limb-darkening coefficients for the component disks, u 1 and u 2; and microfluctuations in the brightnesses of the stars prevent determination of the rate of rotation of the elliptical orbit in the system, even using the most accurate measurements. 相似文献
16.
M. V. Eselevich 《Astronomy Reports》2010,54(2):173-183
The perturbed zones and shocks preceding coronal mass ejections (CMEs) are studied using the data of the Mark 4, LASCO C2,
and LASCO C3 coronagraphs. Detection of the perturbed zone indicating the presence or absence of the shock is most reliable
in a frame moving with the frontal structure of the CME. The ability to correctly measure the width δ
F
of the shock front using the Mark 4 and LASCO C2 data is established. The front width δ
F
observed along the streamer belt at distances R < 5 R
⊙ from the center of the Sun is of the order of the mean free path of protons. This means that the energy dissipation in the
shock front is collisional at such distances. At distances R ≥ (10 − 15) R
⊙, a new discontinuity with a front δ*
F
≪ δ
F
is formed in the leading portion of the front. Within the errors, δ*
F
≈ (0.1–0.2) R
⊙ is independent of the distance R and is determined by the LASCO C3 spatial resolution. Initially, the discontinuity on the scale δ*
F
is weak and coexists with the front with width δ
F
. The relative amplitude of this discontinuity increases and the brightness profile behind it flattens as long as the distance
R increases. This transformation of the brightness profile from a front of width δ
F to a discontinuity of width δ*
F
≪ δ
F
is explained as a transition from a collisional to a collisionless shock. 相似文献
17.
We have determined the main parameters of the old precataclysmic variable stars MS Peg and LM Com. The radial velocities of the components, reflection effects in the spectra, and light curves of the systems are studied based on model stellar atmospheres subject to external irradiation. Forty-seven moderate-resolution spectra for MS Peg and 57 for LM Com obtained with the 6-m telescope of the Special Astrophysical Observatory are used to derive the refined orbital periods of 0.1736660 days and 0.2586873 days, respectively; the orbital eccentricities do not exceed e=0.04. The mass (M w =0.49e⊙) and radius (e w =0.015R⊙) of the MS Peg primary calculated using the gravitational redshift correspond to those for a cooling carbon white dwarf with a thin hydrogen envelope. The parameters of the red dwarf (M r =0.19M⊙, Teff=3560 K, R r =0.18R⊙) are close to those derived from evolutionary tracks for main-sequence M stars with solar chemical composition. The radius (R r =0.22R⊙) and temperature (Teff=3650 K) of the LM Com secondary exceed theoretical estimates for main-sequence stars with masses of M r =0.17M⊙. The luminosity excess of the red dwarf in LM Com can be explained by a prolonged (T>5×106 yrs) relaxation of the M star to its normal state after the binary leaves the common-envelope stage. For both systems, theoretical U, B, V, and R light curves and spectra calculated using the adopted sets of parameters are generally consistent with the observations. This confirms the radiative origin of the hot spots, the unimportance of horizontal radiative transport, and the absence of large-scale velocity fields with high values (Vtrans>50 km/s) at the surfaces of the secondaries. Most of the emission lines in the spectra of these objects are formed under conditions close to thermalization, enabling modeling of their pro files in an LTE approximation. A strong λ3905 Å emission line has been identified as the 3s23p4s 1P0-3s23p2 1S SiI λ3905.52 Å line formed in the atmosphere of the hot spot. The observed intensity can be explained by non-LTE “superionization” of SiI atoms by soft UV radiation from the white dwarf. We suggest a technique for identifying binaries whose cool components are subject to UV irradiation based on observations of λ3905 Å emission in their spectra. 相似文献
18.
A data set of three-component short-period digital seismograms recorded in Friuli after the strong earthquake of 6th May 1976, allowed the local magnitude ML and the seismic moment M0 to be estimated in the range 0 < ML < 2. The data set including the same parameters for the higher-magnitude Friuli events (ML 5) shows two different slopes for the relation Log M0 = CML + d for the two different ranges of ML. One finds C ~ 1.0 (for 0 < ML < 2) and C ~1.5 (for5 ML 6.2), respectively.This implies that apparent stress release increases at low magnitudes, while it appears to be comparatively independent of the magnitude and to have an average value of about 100 bar for higher-magnitude earthquakes. Conversely, the fault dimensions do not appear to be magnitude-dependent for ML < 2; for higher-magnitude events the linear fault dimensions range from about 1 km at ML ~ 5 to about 12 km for the strong earthquake of 6th May 1976 (ML = 6.2). 相似文献
19.
Some properties of the development of the perturbed zone and shock preceding a coronal mass ejection
SOHO/LASCO C2 and C3 data have been used to carry out a detailed study of the perturbed zone and shock that form as a coronal
mass ejection (CME) moves away from the Sun, as a result of its interaction with the ambient solar wind. The event of January
4, 2002 is used as an example. The perturbed zone is most extensive along the direction of propagation of the CME, decreases
away from this direction, and reaches its minimum values perpendicular to this direction. The mass of the perturbed zone is
≥0.1 of the total mass of the CME. The condition for the formation of a shock preceding the CME (in the direction of propagation
of the CME) is V − V
SW
> V
A
, where V, V
SW
, and V
A
are the CME, solar wind, and Alfvén velocities, respectively. Perpendicular to the CME axis, at distances of ≈4–6R
⊙ fromthe center of the Sun, the condition for the formation of shock is V/2 > V
A
. 相似文献
20.
Minimum energy geometries and electron density distributions, ϱ(r), for ∼40 polyatomic oxide molecules containing first and second row M-cations have been calculated at the Hartree-Fock level with a 6-311++G** basis set. The nature of the bonded interactions
in these molecules is examined in terms of the relative electronegativities, χ
M
, of the M-cations and the properties of the electron density distribution, ϱ(r
c
), evaluated at the bond critical points, r
c
, along each MO bond. As ϱ(r
c
) and the Laplacian of ϱ(r
c
) increase, χ
M
increases indicating an increase in the covalent character of the bonded interactions between M and O. The ratios of the curvatures of ϱ(r
c
) indicate that the NO bond is predominantly covalent, that the CO and SO bonds are of intermediate type and that the remaining
MO bonds are indicated to be predominantly ionic in character. A comparison of the critical point properties of ϱ(r
c
) and χ
M
indicates that the minimum energy MO bond length is an important determinate of the properties of ϱ(r
c
) and the character of the MO bonds.
On the other hand, values of the local energy density, H(r
c
), indicate that the LiO, BeO, NaO, MgO and AlO bonds are predominantly ionic and that the BO, CO, NO, SiO, PO and SO bonds
are predominantly covalent in character. The χ
M
-values provided by the properties of ϱ(r
c
) indicate that the covalent component of a bond increases with decreasing bond length, coordination number and increasing
bond strength. Each MO bond seems to represent a unique entity and to possess a distinct set of ϱ(r
c
) properties, the distinction being greater for the more electronegative cations.
The bonded radius of the oxide ion, r
b
(O), and the χ
M
-values determined from ϱ(r
c
) correlate with values determined from promolecule electron density distributions. In addition, r
b
(O) and χ
M
-values determined from experimental electron density distributions for crystals correlate with values determined from procrystal
electron density distributions. The number of critical points and bond paths are modeled rather faithfully by procrystal and
promolecule electron density distributions, despite the neglect of the binding forces in their constructions.
Received: October 15, 1996/Revised, accepted: February 10, 1997 相似文献