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1.
A study of the structure and kinematics of the Galaxy from Tautenburg Schmidt plates taken towards the Galactic centre (l = 17.0°, b = +0.8°) is presented. Proper motions and B, V magnitudes were determined for about 36 500 stars up to the limiting magnitude V = 16m.8 in a field of 8.95 square degrees. Proper motion accuracy of about 3 mas/year has been obtained for stars brighter than V = 15m. The rms errors of stellar magnitudes and (B–V) colours is about 0.1 mag. The majority of field stars in the survey are main sequence stars and red giants of the disk. They belong to the Local or Sagittarius-Carina arms, or they are located between these spiral arms. Comparing the modelled and observed distributions of magnitudes and colours, we specified the interstellar extinction determined in the preceding study of open clusters in this field. The luminosity function towards the Galactic centre was determined for stars with absolute magnitudes from -4m.35 to +9m. Kinematical and spatial distribution parameters up to 4 kpc from the Sun were obtained as a function of galactocentric distance. 相似文献
2.
R.L. Branham Jr. 《Astrophysics and Space Science》2003,288(4):313-325
Use is made of 93,106 parallaxes from the Hipparcos catalog, with a mixture of spectrum-luminosity classes, to derive the
position of the Galactic plane. The reduction technique, mixed total least squares-least squares, takes into account the errors
in the parallaxes, and the condition that the direction cosines of the Galactic pole have unit Euclidean norm is rigorously
enforced. To obtain an acceptable solution it is necessary to eliminate the stars of classes O and B that belong to the Gould
belt. The Sun is found to lie 34.56±0.56 pc above the plane. The coordinates of the Galactic pole, l
g
,
b
g, are found to be: l
g
=0.°004±0.°039;
b
g
=89.°427±0.°035.This agrees well with what radio observations find and demonstrates that the IAU's recommendation in 1960 to use only radio
observations to determine the Galactic pole, although correct at the time because of the paucity of optical observations,
can no longer be justified given the plethora of observations contained in the Hipparcos catalog and an adequate reduction technique, unavailable in 1960. The reduction technique is also demonstrably superior to
others because it involves fewer assumptions and calculates smaller mean errors.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
L. Meillon 《Astrophysics and Space Science》1999,265(1-4):179-180
A large number of high-velocity stars was included in the Hipparcos Input Catalogue for the purpose of determining the galactic
escape velocity in the solar vicinity. However, the `fastest' stars known, listed by Carney et al. (1994, CLLA) were not included because they are too faint. In the intersection between the CLLA list and the Hipparcos Catalogue
(770 common stars), the metal-deficient stars with the most reliable parallaxes (fracσππ)HIP ≤ 0.15) are used for recalibrating CLLA absolute magnitudes and photometric parallaxes, using metallicities and VandenBerg
et al. (1998) isochrones. In this way, about twenty non-Hipparcos stars get improved parallaxes and are added to our primary sample
of Hipparcos high-velocity stars, for a better determination of the escape velocity from the Galaxy.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
E.E. Mamajek 《Astronomische Nachrichten》2010,331(7):704-708
Greaves (2006) proposed that three red, high proper motion stars within 10° of 51 Peg (NLTT 54007, 54064, and 55547) are co‐moving companions to this famous exoplanet host star. While the stars clearly have proper motions similar to 51 Peg, the inferred kinematic parallaxes for these stars produce extremely inconsistent color‐magnitude positions 2 to 4 magnitudes below the main sequence. All three stars are likely to be background stars unrelated to 51 Peg (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
5.
We show that the set of observational characteristics for low-mass X-ray binaries in the optical and X-ray bands can be explained
in terms of the model of an optically thick accretion disk with an atmosphere irradiated by a central X-ray source. We show
that this set of observational data can be successfully used to measure the orbital inclination of a binary, the geometric
parameters of its accretion disk, and the reprocessing time of X-emission to optical one. For the burster GS 1826-238, a low-mass
X-ray binary with a neutron star, we have estimated the binary inclination and the thickness of the disk atmosphere at the
outer edge from the mean optical flux and the amplitude of periodic modulations in the optical light curve: i = 62.5° ± 5.5° and H
d/R
d = 0.145 ± 0.009. The optical response time of the binary to an X-ray burst disagrees with the geometric delay in the propagation
of X-ray photons in the binary. We believe that this points to a finite X-ray reprocessing/reradiation time, 1.0 s ≲ τ
repr ≲ 2.2 s, in the hot atmosphere above the accretion disk. 相似文献
6.
W. Wegner 《Monthly notices of the Royal Astronomical Society》2007,374(4):1549-1556
The absolute visual magnitudes, MV , of A–M stars are based on calculated Hipparcos trigonometric parallaxes. The sample used consists of 30 986 unreddened and reddened A–M stars in luminosity classes Ia, Iab, Ib, II, III, IV and V. The colour excesses of the reddened stars were calculated using the mean colour indices, according to the SIMBAD data base and the intrinsic B − V values calibrated for the given spectral types and luminosity classes by Schmidt-Kaler. The values of the total-to-selective extinction, RV = AV / E ( B − V ) , for all the reddened stars were calculated from previously published near-infrared photometric measurements. The calculated visual magnitudes, MV , of A–M stars compare with the earlier determinations of Schmidt-Kaler. The mean absolute magnitudes published by Schmidt-Kaler are generally brighter (except for the stars in luminosity classes V and IV) than those determined in this paper. 相似文献
7.
While implementing the first stage of the Pulkovo program of research on stars with large proper motions, we determined the
trigonometric parallaxes of 29 stars (12
m
< V < 16
m
) based on CCD observations with a 26-inch refractor. The mean standard error was 3.7 mas. Comparison of the Pulkovo parallaxes
with those obtained at the Observatory of the Yale University and the US Naval Observatory (USNO) has shown that the parallax
differences (Pulkovo-Yale/USNO) lie within the limits of their measurement errors in an overwhelming majority of cases. On
average, they are −0.6 ± 1.0 mas. No systematic dependences on stellar distance, magnitude, and color in this set of differences
have been found. Our comparisons show that the observing and data reduction techniques used in the Pulkovo program of research
on fast stars allow highly accurate trigonometric parallaxes of these objects to be obtained. All program stars are within
50 pc of the Sun; most of them belong to the immediate solar neighborhood (D < 25 pc). For two stars (J0522+3814 and J1202+3636), the trigonometric parallaxes have been determined for the first time. 相似文献
8.
We present relative astrometry and differential photometry measurements for a sample of nearby southern orbital binaries making use of the technique of Adaptive Optics. The observations were made in December 2000, with the ADONIS camera mounted at the 3.6‐m ESO telescope from La Silla Observatory, equipped with the broad‐band near‐infrared filters (J ‐, H ‐, K ‐passbands). Our sample contains stars which do not fit very well the empirical mean mass‐luminosity relation (according to our previous study), but for which accurate parallaxes (determined by the Hipparcos satellite) and high‐quality orbits were available thanks to many previous efforts. We derived accurate positions and J, H, K magnitudes of the individual components of those binaries. The individual stellar components have near‐infrared colour indices well grouped in those plots and are comparable to standard single stars. The data reduction procedure used for deriving those results is described in detail. It is based on a least‐squares fit of Moffat‐Lorentz profiles in direct imaging for well‐resolved systems and on Fourier analysis for very close pairs. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
9.
A sample of subdwarfs with accurate space velocities and standarized metallicities is presented. This was constructed by combining
Hipparcos parallaxes and proper motions with radial velocities and metallicities from Carney et al. (1994; CLLA). The accurate Hipparcos parallaxes lead to an – upward – correction factor of 11% of the photometric distance
scale of CLLA. The kinematical behaviour of the subdwarfs is discussed in particular in relation to their metallicities. Most
of the stars turn out to be thick disk stars, but the sample contains also many genuine halo stars. While the extreme metal
poor halo does not rotate, a population of subdwarfs with metallicities in the range −1.6≤ [Fe/H] ≤ −1.0 dex appears to rotate
around the galactic center with a mean rotation speed of about 100 km s-1.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
10.
The absolute visual magnitudes of 457 Be stars are determined from Hipparcos parallaxes, subsequently the mean absolute visual
magnitudes of Be stars for luminosity classes III, IV and V are obtained. The new Mv calibration is compared with existing
calibrations. It is found that Be stars are generally brighter than B stars of the corresponding spectral types, and that
there is no direct correlation between absolute magnitudes and the stellar rotational velocity, these results are in agreement
with some earlier results. A new and interesting result is that there is no direct correlation between near infrared excess
and absolute visual magnitudes for Be stars. Moreover, possible biases, such as the Malmquist bias and the Lutz–Kelker bias,
are also discussed. 相似文献
11.
12.
W. Wegner 《Monthly notices of the Royal Astronomical Society》2006,371(1):185-192
A new method of determining absolute visual magnitudes of early-type stars, based on averaging Hipparcos parallaxes ( ESA 1997 ) inside samples of the same spectrum and luminosity (Sp/L) classes, is proposed. The used sample consists of 6262 unreddened and reddened OB stars as well as 430 Be stars of luminosity classes Ia, Iab, Ib, II, III, IV and V. The colour excesses of the reddened stars have been calculated using the mean colour indices, according to the SIMBAD data base and the intrinsic ( B − V ) values calibrated for given Sp/L classes by Papaj, Wegner & Krełowski . The values of the total-to-selective extinction RV = AV / E ( B − V ) for all reddened stars were calculated from the published near-infrared photometric measurements. The calculated visual magnitudes MV of OB and Be stars are compared to those published by Wegner in Paper I, and the earlier determinations of Schmidt-Kaler. Generally, the new values of MV agree well with those given in Paper I, except those for O stars which are systematically brighter than the earlier estimates. The mean absolute magnitudes published by Schmidt-Kaler are generally brighter (except OB stars of luminosity class V) than those determined in this paper. 相似文献
13.
We report observations of the radio disk temperatures of Mars and Jupiter made during October 1971, at a wavelength of 1.35 cm. The mean disk temperature of Jupiter is 136 ± 5°K, in good agreement with the value 139 ± 6°K obtained by Wrixon et al. (1971) with the same instrument three years earlier. The disk temperature of Mars is 181 ± 11°K, consistent with an essentially wavelength independent disk temperature for Mars at radio wavelengths. The ratio of the two disk temperatures, 1.33 ± .07, is largely free of the systematic uncertainties: antenna gain, pointing, and atmospheric extinction. 相似文献
14.
Cloud motions were obtained from a number of images acquired in reflected solar ultraviolet light during spring and fall of 1979 from the Pioneer Venus Orbiter Cloud Photopolarimeter (OCPP) to determine the zonal mean circulation of the atmosphere of Venus at the cloud top level. The meridional profile of the zonal component of motion is somewhat different from that previously obtained from Mariner 10 and preliminary Pioneer Venus observations, although the equatorial magnitude is about the same (?94 m/sec). The mean meridional motion is toward the south pole south of about 5° south latitude, and toward the north pole north of this latitude, with peak mean magnitudes of about 7 m/sec polewards of 20° north and 40° south latitudes in the respective hemispheres. From the few measurements obtained at higher latitudes the magnitude of the mean meridional component appears to decrease although it is still directed toward the respective poles. Due to the evolution of the cloud patterns over the duration of the images from which the cloud velocities are obtained, the uncertainties in the mean zonal and meridional components may be as large as 5–10 and 2–4 m/sec, respectively. Preliminary estimates of meridional momentum transport show that the mean circulation dominates the eddy circulation transport completely, in agreement with the estimates obtained from Mariner 10 data, although the uncertainties in both the mean and eddy circulation transports are large. The momentum transports are polewards and their peak magnitudes occur at latitudes between 20° and 40° in both the hemispheres. 相似文献
15.
《New Astronomy》2003,8(7):645-653
In this paper, relation was established for Hyades stars between their apparent magnitudes and parallaxes. The precision criteria of this relation are very satisfactory. The importance of this relation was illustrated through its usages as: (1) A criterion for membership of the cluster, (2) a generating function for evaluating some parameters of the cluster. 相似文献
16.
Naoteru Gouda Takuji Tsujimoto Yukiyasu Kobayashi Tadashi Nakajima Naoki Yasuda Hideo Matsuhara 《Astrophysics and Space Science》2002,280(1-2):89-94
JASMINE is the name of a Japanese infrared (K-band) scanning astrometric satellite. JASMINE (I and/or II-project) is planned to be launched between 2013 and 2017 and will
measure parallaxes and proper motions with the precision of 10μas at K≃ 12 - 15 mag. JASMINE will observe a few hundred million stars belonging to the disk and the bulge components of our Galaxy,
which are hidden by the interstellar dust extinction in optical bands. Furthermore, JASMINE will also obtain photometry of
stars in K, J and H-bands. The main objective of JASMINE is to study the most fundamental structure and evolution of the disk and the bulge components
of the Milky Way Galaxy.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
L. K. Kristensen 《Astronomische Nachrichten》1984,305(4):207-211
The mean diameter D = 147 ± 3 km of (106) Dione is derived from visual observations in Denmark, Germany and the Netherlands of the occultation of AGK3 + 25°0989 on 1983 January 19. Photoelectric magnitudes are: B(1, 2°.4) = 8m.51 ± 0m.06 and B – V = 0m.65 ± 0m.07. The visual albedo is pv = .064. Constraints on the axis of rotation are derived from the observed elliptical contour. 相似文献
18.
Eugene E. Epstein Michael A. Janssen Jeffrey N. Cuzzi William G. Fogarty John Mottmann 《Icarus》1980,41(1):103-118
We have used 3-mm Saturn observations, obtained from 1965 through 1977 and with Jupiter as a reference, to derive a ring brightness temperature of 18 ± 8°K. Thebrightness temperature of the disk of Saturn is 156 ± 9° K. Part of the ring brightness (≈62K) may be accounted for as disk emission which is scattered from the rings; the remainder (12 ± 8° K we attributed to ring particle thermal emission. Because this thermal component brightness temperatures is so much less than the particle physical temperature, limits are placed on the mean size and composition of the ring particles. In particular, as found by others, the particles cannot be rocky, but must be either metallic or composed of extremely low-loss dielectric material such as water ice. If the particles are pure water ice, for example, then a simple slab model and a multiple-scattering model both give upper limits to the particle sizes of ≈ 1 m, a value three times smaller than previously available. The multiple-scattering model gives a particle single-scattering albedo at 3 mm of 0.83±0.13. 相似文献
19.
We present a catalogue of radial velocities of Galactic stars with high precision astrometric data CRVAD which is the result of the cross‐identification of star lists from the General Catalog of Average Radial Velocities (GCRV) and from the homogeneous All‐sky Compiled Catalogue of 2.5Million Stars (ASCC‐2.5). The CRVAD includes accurate J2000 equatorial coordinates, proper motions and trigonometric parallaxes in the Hipparcos system, Johnson's BV photometric data, spectral types, multiplicity and variability flags from the ASCC‐2.5, and radial velocities, stellar magnitudes and spectral types from the GCRV for 34553 ASCC‐2.5 stars. The CRVAD was used for the construction of a sample of standard stars with accurate astrometric, photometric and radial velocity data for the RAVE project. A second application of the CRVAD , the radial velocity determination for 292 open clusters (including 97 with previously unknown radial velocities), using their newly defined members from proper motions and photometry in the ASCC‐2.5, is briefly described. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
20.
M. Scardia 《Astronomische Nachrichten》1981,302(1):35-42
The orbital elements of the visual binary stars ADS 363, -69° 44127 CD and HJ 3423 are given. At last, the dynamical parallaxes and total masses of the systems have been calculated. 相似文献