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1.
Jean Audouze 《Journal of Astrophysics and Astronomy》1987,8(2):81-82
The abundances of very light elements D,3He,4He and7Li in low-mass stars and their cosmological implications are discussed. 相似文献
2.
E. Caffau M. Steffen P. Bonifacio H.‐G. Ludwig L. Monaco G. Lo Curto I. Kamp 《Astronomische Nachrichten》2014,335(1):59-64
The measurement of isotopic ratios provides a privileged insight both into nucleosynthesis and into the mechanisms operating in stellar envelopes, such as gravitational settling. In this article, we give a few examples of how isotopic ratios can be determined from high‐resolution, high‐quality stellar spectra. We consider examples of the lightest elements, H and He, for which the isotopic shifts are very large and easily measurable, and examples of heavier elements for which the determination of isotopic ratios is more difficult. The presence of 6Li in the stellar atmospheres causes a subtle extra depression in the red wing of the 7Li 670.7 nm doublet which can only be detected in spectra of the highest quality. But even with the best spectra, the derived 6Li abundance can only be as good as the synthetic spectra used for their interpretation. It is now known that 3D non‐LTE modelling of the lithium spectral line profiles is necessary to account properly for the intrinsic line asymmetry, which is produced by convective flows in the atmospheres of cool stars, and can mimic the presence of 6Li. We also discuss briefly the case of the carbon isotopic ratio in metal‐poor stars, and provide a new determination of the nickel isotopic ratios in the solar atmosphere. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
3.
In this paper we review the chemical evolution models for the Galactic bulge: in particular, we discuss the predictions of
models as compared with the available abundance data and infer the mechanism as well as the time scale for the formation of
the Galactic bulge. We show that good chemical evolution models reproducing the observed metallicity distribution of stars
in the bulge predict that the [α/Fe] >0 over most of the metallicity range. This is a very important constraint indicating
that the bulge of our Galaxy formed at the same time and even faster than the inner Galactic halo. We also discuss predictions
for the evolution of light elements such as D and 7Li and conclude that the D astration should be maximum due to the high star formation rate required for the bulge whereas
the evolution of the abundance of Li should be similar to that observed in the solar neighbourhood, but with an higher Li
abundance in the interstellar medium at the present time.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
The problem of lithium in chemically peculiar Ap-CP stars has been the subject of debate for many years. The main reason for
this is a lack of spectral observations of Ap stars in the neighborhood of the lithium resonance doublet Li I 6708 Å. An international
cooperation project on “Lithium in cool CP stars with magnetic fields” was started in 1996. Systematic observations of CP
stars in spectral regions of the 6708 Å and 6103 Å lines at the ZTSh (CrAO), CAT (ESO), Feros (ESO), and the 74″ telescope
of the Mount Stromlo Observatory (Australia) have been used to analyze spectra of several CP stars studied by the way the
6708 Å lithium line varies with the stars’ rotational phase. Monitoring of the spectra of the oscillating CP stars (group
I) HD 83368, HD 60435, and HD 3980, for which significant Doppler shifts of the Li I 6708 Å line are observed led to the discovery
of “lithium spots” on the surface of these stars whose positions are related to the magnetic field structure. Models of the
surfaces of these stars with the special program “ROTATE” based on the profiles of the Li I 6708 Å line are used to estimate
the size of the spots, their positions on the stars’ surface, and the lithium abundances in these spots. A detailed analysis
and modelling of the spectra of slowly rotating oscillating CP stars with strong, invariant lithium 6708 Å emission, including
blending with lines of the rare earth elements, reveals an enhanced lithium abundance, with the abundance determined from
the lithium 6103 Å line being higher than that determined from the 6708 Å line for all the stars. This may indicate vertical
stratification of lithium in the atmospheres of CP stars with an anomalous isotopic composition (6Li/7Li = 0.2–0.5). HD 101065, an ultraslow rotator (vsini ≈ 1.5) visible from the poles and with powerful oscillations which cause pulsating line broadening in its spectrum, is unique
among these stars. The amount of lithium in the atmosphere of HD 101065 logN(Li) = 3.1 on a scale of logN(H) = 12.0 and the isotope ratio 6Li/7Li ≈ 0.3. The high estimates of 6Li/7Li may be explained by the production of lithium in spallation reactions and the preservation of surface 6Li and 7Li by strong magnetic fields in the upper layers of the atmosphere near the magnetic poles.
__________
Translated from Astrofizika, Vol. 50, No. 3, pp. 463–492 (August 2007). 相似文献
5.
Light element nucleosynthesis is an important chapter of nuclear astrophysics. Specifically, the rare and fragile light nuclei
Lithium, Beryllium and Boron (LiBeB) are not generated in the normal course of stellar nucleosynthesis (except 7Li) and are, in fact, destroyed in stellar interiors. This characteristic is reflected in the low abundance of these simple
species. Up to recently, the most plausible interpretation was that Galactic Cosmic Rays (GCR) interact with interstellar
CNO to form LiBeB. Other origins have been also identified: primordial and stellar (7Li) and supernova neutrino spallation (7Li and 11B). In contrast, 9Be, 10B and 6Li are pure spallative products. This last isotope presents a special interest since the 6Li/7Li ratio has been measured recently in a few halo stars offering a new constraint on the early galactic evolution of light
elements. Optical measurements of the beryllium and boron abundances in halo stars have been achieved by the 10 meter KECK
telescope and the Hubble Space Telescope. These observations indicate a quasi linear correlation between Be and B vs Fe, at
least at low metallicity, which, at first sight, is contradictory to a dominating GCR origin of the light elements which predicts
a quadratic relationship. As a consequence, the theory of the origin and evolution of LiBeB nuclei has to be refined. Aside
GCRs, which are accelerated in the general interstellar medium (ISM) and create LiBeB through the break up of CNO by fast
protons and alphas, Wolf-Rayet stars (WR) and core collapse supernovae (SNII) grouped in superbubbles could produce copious
amounts of light elements via the fragmentation in flight of rapid carbon and oxygen nuclei colliding with H and He in the
ISM. In this case, LiBeB would be produced independently of the interstellar medium chemical composition and thus a primary
origin is expected. These different processes are discussed in the framework of a galactic evolutionary model. More spectroscopic
observations (specifically of O, Fe, Li, Be, B) in halo stars are required for a better understanding of the relative contribution
of the various mechanisms. Future tests on the injection and acceleration of nuclei by supernovae and Wolf Rayet relying on
gamma-ray line astronomy will be invoked in the perspective of the European INTEGRAL satellite.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
Li abundance is determined for 23 halo subdwarfs. About half of the stars show [Fe/H] < −1.4 and a space velocityV > 160 km s−1 Li appears to be present in all our halo stars, with an abundance within about ± 0.2 dex of the value logn (Li) = 2.0 found by Spite & Spite (1982). Thus our results provide confirmation of the main conclusion of Spite & Spite. 相似文献
7.
The space velocities and Galactic orbital elements of stars calculated from the currently available high-accuracy observations in our compiled catalog of spectroscopic magnesium abundances in dwarfs and subgiants in the solar neighborhood are used to identify thick-disk objects. We analyze the relations between chemical, spatial, and kinematic parameters of F–G stars in the identified subsystem. The relative magnesium abundances in thick-disk stars are shown to lie within the range 0.0 < [Mg/Fe] < 0.5 and to decrease with increasingmetallicity starting from [Fe/H] ≈ ?1.0. This is interpreted as evidence for a longer duration of the star formation process in the thick disk. We have found vertical gradients in metallicity (gradZ[Fe/H] = ?0.13 ± 0.04 kpc?1) and relative magnesium abundance (gradZ[Mg/Fe] = 0.06 ± 0.02 kpc?1), which can be present in the subsystem only in the case of its formation in a slowly collapsing protogalaxy. However, the gradients in the thick disk disappear if the stars whose orbits lie in the Galactic plane, but have high eccentricities and low azimuthal space velocities atypical of the thin-disk stars are excluded from the sample. The large spread in relative magnesium abundance (?0.3 < [Mg/Fe] < 0.5) in the stars of the metal-poor “tail” of the thick disk, which constitute ≈8% of the subsystem, can be explained in terms of their formation inside isolated interstellar clouds that interacted weakly with the matter of a single protogalactic cloud. We have found a statistically significant negative radial gradient in relative magnesium abundance in the thick disk (gradR[Mg/Fe] = ?0.03 ± 0.01 kpc? 1) instead of the expected positive gradient. The smaller perigalactic orbital radii and the higher eccentricities for magnesium-richer stars, which, among other stars, are currently located in a small volume of the Galactic space near the Sun, are assumed to be responsible for the gradient inversion. A similar, but statistically less significant inversion is also observed in the subsystem for the radial metallicity gradient. 相似文献
8.
Data from our compiled catalog of spectroscopically determined magnesium abundances in stars with accurate parallaxes are used to select thin-disk dwarfs and subgiants according to kinematic criteria. We analyze the relations between the relative magnesium abundances in stars, [Mg/Fe], and their metallicities, Galactic orbital elements, and ages. The [Mg/Fe] ratios in the thin disk at any metallicity in the range ?1.0 dex <[Fe/H] < ?0.4 dex are shown to be smaller than those in the thick disk, implying that the thin-disk stars are, on average, younger than the thick-disk stars. The relative magnesium abundances in such metal-poor thin-disk stars have been found to systematically decrease with increasing stellar orbital radii in such a way that magnesium overabundances ([Mg/Fe] > 0.2 dex) are essentially observed only in the stars whose orbits lie almost entirely within the solar circle. At the same time, the range of metallicities in magnesium-poor stars is displaced from ?0.5 dex < [Fe/H] < +0.3 dex to ?0.7 dex < [Fe/H] < +0.2 dex as their orbital radii increase. This behavior suggests that, first, the star formation rate decreases with increasing Galactocentric distance and, second, there was no star formation for some time outside the solar circle, while this process was continuous within the solar circle. The decrease in the star formation rate with increasing Galactocentric distance is responsible for the existence of a negative radial metallicity gradient (grad R[Fe/H] = ?0.05 ± 0.01 kpc?1) in the disk, which shows a tendency to increase with decreasing age. At the same time, the relative magnesium abundance exhibits no radial gradient. We have confirmed the existence of a steep negative vertical metallicity gradient (grad Z[Fe/H] = ?0.29 ± 0.06 kpc?1) and detected a significant positive vertical gradient in relative magnesium abundance (grad Z[Mg/Fe] = 0.13 ± 0.02 kpc?1); both gradients increase appreciably in absolute value with decreasing age. We have found that there is not only an age-metallicity relation, but also an age-magnesium abundance relation, in the thin disk. We surmise that the thin disk has a multicomponent structure, but the existence of a negative trend in the star formation rate along the Galactocentric radius does not allow the stars of its various components to be identified in the immediate solar neighborhood. 相似文献
9.
《New Astronomy》2007,12(4):265-270
Surface lithium abundance and rotation velocity can serve as powerful and mutually complementary diagnostics of interior structure of stars. So far, the processes responsible for the lithium depletion during pre-main sequence evolution are still poorly understood. We investigate whether a correlation exists between equivalent widths of Li (EW(Li)) and rotation period (Prot) for weak-line T Tauri stars (WTTSs). We find that rapidly rotating stars have lower EW(Li) and the fast burning of Li begins at the phase when star’s Prot evolves towards 3 days among 0.9M⊙ to 1.4M⊙ WTTSs in Taurus–Auriga. Our results support the conclusion by Piau and Turch-Chiéze about a model for lithium depletion with age of the star and by Bouvier et al. in relation to rotation evolution. The turn over of the curve for the correlation between EW(Li) and Prot is at the phase of zero-age main sequence (ZAMS). The EW(Li) decreases with decreasing Prot before the star reaches the ZAMS, while it decreases with increasing Prot (decreasing rotation velocity) for young low-mass main sequence stars. This result could be explained as an age effect of Li depletion and the rapid rotation does not inhibit Li destruction among low-mass PMS stars. 相似文献
10.
Based on the Ogorodnikov-Milne model, we analyze the proper motions of Tycho-2 and UCAC2 stars. We have established that the model component that describes the rotation of all stars under consideration around the Galactic y axis differs significantly from zero at various magnitudes. We interpret this rotation found using the most distant stars as a residual rotation of the ICRS/Tycho-2 system relative to the inertial reference frame. For the most distant (d≈900 pc) Tycho-2 and UCAC2 stars, the mean rotation around the Galactic y axis has been found to be M 13 ? =?0.37±0.04 mas yr?1. The proper motions of UCAC2 stars with magnitudes in the range 12–15m are shown to be distorted appreciably by the magnitude equation in μα cos δ, which has the strongest effect for northern-sky stars with a coefficient of ?0.60±0.05 mas yr?1 mag?1. We have detected no significant effect of the magnitude equation in the proper motions of UCAC2 stars brighter than ≈11m. 相似文献
11.
The relationship between the depletions of 6Li and 7Li is studied for two models of lithium burning, below the convective zone. The parametersof the depletion models are submitted
to the constraint that the slope ofthe 7Li theoretical depletion curve agrees with the slope of theobserved depletion curve, for cool subdwarfs. Other less restrictive
modelsare also considered.In all cases, a 6Li depletion less than 0.5 dex implies a 7Lidepletion less than 0.1 dex. With the constraint on the slope of the7Li curve, the depletion of 7Li for the same depletion of 6Li is below 0.05 dex.
The still unsolved problem for the true 7Li abundance in subdwarfs is the possible influence of temperature inhomogeneities, raised by Kurucz,subsequently shown to
be small in the solar case, but not yet computed withthe inclusion of departure from LTE for metal-poor stars.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
12.
A. I. Yatsenko 《Astrophysics and Space Science》1988,142(1-2):85-88
Summary In this paper the results of the research of the stars proper motions Trapezium components are reported. They are: the galactic
coordinates of the solar aprx and the Sun velocity (L
⊙=43±18°,B
⊙=+28±13°,V
⊙=13±4 km s−1), the dispersion of peculiar velocities in the direction of the galactic coordinates for the above mentioned stars (σ
l
=±11 km s−1, σ
b
=±7 km s−1).The attained accuracy of the proper motions (±0.005″ yr−1) is shown to be insufficient to the study of internal space motions in these systems. At present the work to increase the
relative proper motions accuracy for multiple system components and to improve reductions from the relative to absolute proper
motions, is being carried out in the Main Astronomical Observatory (Academy of Sciences of the Ukrainian SSR). The new catalogue
of the AGK3 stars is composed now in the vicinity of the galactic equator in order to improve reductions from the relative
to absolute proper motions. The r.m.s. errors of the proper motions, obtained in the AGK3 system, are ±0.005″ yr−1. 相似文献
13.
Using LTE calculations of the structure of T Tauri stellar atmospheres heated by radiation from an accretion shock (Dodin and Lamzin 2012), we have calculated the spectrum of the hot spot emerging on the stellar surface by taking into account non-LTE effects for He I, He II, Ca I, and Ca II. Assuming the pre-shock gas density N 0 and velocity V 0 to be the same at all points of the accretion stream cross section, we have calculated the spectrum of the star+circular spot system at various N 0, V 0, and parameters characterizing the star and the spot. Using nine stars as an example, we show that the theoretical optical spectra reproduce well the observed veiling of photospheric absorption lines as well as the profiles and intensities of the so-called narrow components of He II and Ca I emission lines with an appropriate choice of parameters. The accreted gas density in all of the investigated stars except DK Tau has been found to be N 0 > 1012 cm?3. We have managed to choose the parameters for eight stars at a calcium abundance in the accreted gas ξ Ca equal to the solar one, but we have been able to achieve agreement between the calculations and observations for TW Hya only by assuming ξ Ca to be approximately a factor of 3 lower than the solar one. The estimated parameters do not depend on interstellar extinction, because they have been determined from the spectra normalized to the continuum level. The calculated intensity of Ca II lines has turned out to be lower than the observed one, but this contradiction can be eliminated by assuming that, in addition to the accreted gas with a high density N 0, a more rarefied gas also falls onto the star. The theoretical equivalent widths and relative intensities of the subordinate He I lines disagree significantly with the observations. This is apparently because non-LTE effects should be taken into account when calculating the structure of the upper layers of the hot spot, the accuracy of the cross sections for collisional processes from upper levels is insufficient, and the spot inhomogeneity should probably be taken into account. 相似文献
14.
The absolute proper motions of about 275 million stars from the Kharkov XPM catalog have been obtained by comparing their
positions in the 2MASS and USNO-A2.0 catalogs with an epoch difference of about 45 yr for northern-hemisphere stars and about
17 yr for southern-hemisphere stars. The zero point of the system of absolute proper motions has been determined using 1.45
million galaxies. The equatorial components of the residual rotation vector of the ICRS/UCAC2 coordinate system relative to
the system of extragalactic sources have been determined by comparing the XPM and UCAC2 stellar proper motions: ω
x,y,z = (−0.06, 0.17, −0.84) ± (0.15, 0.14, 0.14) mas yr−1. These parameters have been calculated using about 1 million faintest UCAC2 stars with magnitudes R
UCAC2 > 16
m
and J > 14
m
. 7, for which the color and magnitude equation effects are negligible. 相似文献
15.
We study the effects of possible deviations of fundamental physical constants on the yields of light nuclides, 2D, 3He, 4He, 7Li, and others during primordial nucleosynthesis. The deviations of fundamental constants from their current values are considered in the low-energy approximation of string theories; the latter predict the existence of a scalar field, which, apart from the tensor gravitational field, determines the space geometry. A two-parameter (η, δ) model is constructed for primordial nucleosynthesis: η = n B /n γ is the baryon-to-photon density ratio, and Ω is the relative deviation of fundamental physical constants at the epoch of primordial nucleosynthesis from their current values. A dependence of η on the deviation of coupling constants Ω has been derived on condition that the primordial helium abundance is Y p = f(η, δ) = const, where const corresponds to experimental values. We thus showed that the relative baryonic density (and hence ΩB could vary over a much wider range than allowed by the standard nucleosynthesis model. Considering this result, we discuss the recently found mismatch between ΩB obtained from an analysis of CMBR anisotropy and from the standard primordial nucleosynthesis model. 相似文献
16.
R. Faraggiana 《Astrophysics and Space Science》1987,134(2):381-403
Chemically peculiar (CP) stars are mainly found among B and A stars. Present theories are not able to account fully for the observed spectrum anomalies, suggesting that in the atmospheres of stars in the range ofT
e
, where mass loss is no longer very large and convection is still not very important, the present theoretical approach needs further refinement. Moreover, the lack of laboratory data is responsible, at least partly, for the discrepancies between observed and computed stellar energy distributions.The choice for quick detection of CP stars among faint objects is reviewed; the measure of the flux depression at 5200 appears to be very powerful, and the identification of this complex feature is urgently needed.The need to separate the various subclasses of the He abnormal stars in a standard way is underlined and further analyses of the characteristics of the Boo stars are required.The problem of the determination ofT
e
and consequently of realistic atmospheric abundance anomalies of CP stars is discussed. 相似文献
17.
We have used two robotic telescopes to obtain time‐series high‐resolution optical echelle spectroscopy and VI and/or by photometry for a sample of 60 active stars, mostly binaries. Orbital solutions are presented for 26 double‐lined systems and for 19 single‐lined systems, seven of them for the first time but all of them with unprecedented phase coverage and accuracy. Eighteen systems turned out to be single stars. The total of 6609 R = 55000 échelle spectra are also used to systematically determine effective temperatures, gravities, metallicities, rotational velocities, lithium abundances and absolute Hα‐core fluxes as a function of time. The photometry is used to infer unspotted brightness, V – I and/or b – y colors, spot‐induced brightness amplitudes and precise rotation periods. An extra 22 radial‐velocity standard stars were monitored throughout the science observations and yield a new barycentric zero point for our STELLA/SES robotic system. Our data are complemented by literature data and are used to determine rotation‐temperature‐activity relations for active binary components. We also relate lithium abundance to rotation and surface temperature. We find that 74% of all known rapidly‐rotating active binary stars are synchronized and in circular orbits but 26% (61 systems) are rotating asynchronously of which half have Prot > Porb and e > 0. Because rotational synchronization is predicted to occur before orbital circularization active binaries should undergo an extra spin‐down besides tidal dissipation. We suspect this to be due to a magnetically channeled wind with its subsequent braking torque. We find a steep increase of rotation period with decreasing effective temperature for active stars, Prot α T–7eff, for both single and binaries, main sequence and evolved. For inactive, single giants with Prot > 100 d, the relation is much weaker, Prot α T‐1.12eff. Our data also indicate a period‐activity relation for Hα of the form RHα α P0.24rot for binaries and RHα α P‐0.14rot for singles. Its power‐law difference is possibly significant. Lithium abundances in our (field‐star) sample generally increase with effective temperature and are paralleled with an increase of the dispersion. The dispersion for binaries can be 1–2 orders of magnitude larger than for singles, peaking at an absolute spread of 3 orders of magnitude near Teff ≈ 5000 K. On average, binaries of comparable effective temperature appear to exhibit 0.25 dex less surface lithium than singles, as expected if the depletion mechanism is rotation dependent. We also find a trend of increased Li abundance with rotational period of form log n (Li) α –0.6 log Prot but again with a dispersion of as large as 3‐4 orders of magnitude (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
18.
The results of computing the evolution of a disk subsystem of a spiral galaxy taking into account radial gradients of chemical elements (D,4He,12C,13C,14N,16O,7Li, Fe) are presented. It is shown that flow of intergalactic matter accreting on to the galaxy results in smoothing the radial gradients of gas and chemical elements, especially at the latest stage of the evolution. The final gradients depend weakly on the age of the galaxy and value of the Hubble constanth. The best agreement between calculated and observed abundance of4He is revealed if the primordial yield isY
0=0.25. The small decrease of the primordial deuterium abundance confirms the conclusion that the baryon density parameter is small:
b
h
50
2
1. Therefore, the nature of dark matter should be non-baryonic. 相似文献
19.
N. Polosukhina A. Shavrina N. Drake D. Kudryavtsev M. Smirnova 《Bulletin of the Crimean Astrophysical Observatory》2010,106(1):57-62
New spectral observations of chemically peculiar (CP) magnetic stars were obtained using an NES echelle spectrometer with a BTA telescope in the Special Astrophysical Observatory (Russian Academy of Sciences). Several stars were shown to have anomalous Li abundances. Testing and monitoring the stars with Doppler shifts Vsini > 10 km/s indicated that the lithium 6708 Å line was variable in the spectra of some roaAP-CP stars. To distinguish variable features in the spectra, the dispersogram technique was used. The most peculiar among the stars studied is HD 12098. The strong and variable lithium 6708 Å line was detected in the spectrum of this star. The star has been shown to have greatly different lithium abundances in two rotation phases corresponding to opposite surface areas. As mentioned earlier, a similar behavior of the Li blend was found in the spectra of HD 83368 and HD 60435 which have lithium spots on their surface. Spectral observations of slowly rotating CP stars with the Doppler shifts Vsini < 10 km/s revealed the strong and nonvariable lithium 6708 Å line in the spectra of these stars. Quantitative spectral analysis using the Li I 6708 Å resonance doublet and the Li I 6103 Å line shows the lithium abundance, as determined by the 6103 Å line, to be somewhat greater than that determined by the 6708 Å line. A higher ratio of 6Li/7Li amounting to ～0.3–0.5 was found in these stars. 6Li production is assumed to be due to spallation reactions on the surface of magnetic CP stars; this isotope ratio remained in strong magnetic fields. 相似文献
20.
C. Travaglio S. Randich D. Galli C. Abia J. Lattanzio 《Astrophysics and Space Science》2002,281(1-2):219-220
Different stellar sources may have contributed to the 7Li enrichmentof the Galaxy: type-II supernovae, novae, and AGB stars. In the latter case, the interplay between the Hot Bottom
Burning (HBB) process (via the Cameron-Fowler mechanism) and a very high mass-loss rate before the evolution off the AGB (the
so-called ‘superwind’ phase), can lead to a significant production of 7Li from low- and intermediate-mass AGB stars (Travaglio et al., 2001). We have now undertaken an observational campaign aimed
at constraining our stellar and Galactic models, with a twofold goal: (i) to assemble a compilation of high-resolution spectra of Galactic, unevolved (i.e. dwarfs), warm(spectral type F) stars,
in a selected metallicity range (-1.0 ≤>[Fe/H] ≤ -0.3), using the ESO 1.5m telescope and the FEROS spectrograph; (ii) to carry out a Li survey among a sample of selected AGB stars, to investigate the possible correlation between7Li abundance (when detected) and mass-loss rate.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献