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מאמרים קשורים
The Classical Algol XZ UMa - Observations and Analysis
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| Establishing Observational Baselines for Two δ Scuti Variables: V966 Herculis and V1438 Aquilae
We have examined the previously understudied δ Scuti stars V966Herculis and V1438 Aquilae. We find that V966 Her is a stable pulsatorwith a refined period of 0.1330302 days with a full V amplitude of 0.096mag. We also find that V966 Her has an average radial velocity of +7.8km s-1, a full radial velocity amplitude of 7.6 kms-1, and a vsini=63.8 km s-1. For V1438 Aql wereport a revised Hipparcos period of 0.1612751 days with a fullamplitude of 0.056. The average radial velocity is found to be -43 kms-1, with full amplitude of 9.7 km s-1, and avsini=76.7 km s-1. Due to some anomalies seen in V1438 Aql wefeel that a much larger photometric and spectroscopic campaign isrequired to determine the true nature of this star.
| The Detached Solar-Type Binary CV Boo
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| Spectroscopy of the post-common envelope binary HW Virginis
We present optical spectroscopy of the post-common envelope binary HWVir covering lambda =3704-8667 Å. We use the low-resolution bluespectra to determine the atmospheric parameters of the sdB primary starand the medium resolution Hα observations to measure its radialvelocity. We find K_1=82.3 +/- 4.0 km s^-1 and gamma = 2.9 +/- 3.1 kms^-1. The effective temperature, gravity and helium abundance of the sdBstar are T_e= 28488 +/- 208 K, log g=5.63 +/- 0.03 and N(He)/N(H)=0.0066+/- 0.0004. These characteristics are typical of a classical sdB star,as is our derived mass of M_1=0.48 +/- 0.09 M_solar. We find thedistance to HW Vir is 171 +/- 19 pc. The predicted value of theprojected orbital velocity of the secondary star is 284 +/- 21 km s^-1.Using previously published photometric light curves of HW Vir wecorrected our spectra to absolute fluxes and extracted the spectrum ofthe secondary star. This spectrum shows Hα absorption lines atphases close to the maximum of the reflection effect, with a measuredradial velocity semi-amplitude of 275+/-15 km s^-1. We attribute theselines to irradiation of the face of the secondary star closest to thesdB star.
| Spectroscopic Orbits for Three Binaries with Low-Mass Companions and the Distribution of Secondary Masses near the Substellar Limit
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJ...466..415M&db_key=AST
| Nine Seasons of Velocity Measurements in the Draco and Ursa Minor Dwarf Spheroidal Galaxies with the MMT Echelle
We have used the Multiple Mirror Telescope echelle spectrograph tomeasure 112 velocities of 42 stars in the Draco and Ursa Minor dwarfspheroidal galaxies and three velocities of three foreground starsbetween 1982 April and 1990 September. We used 11 A resolution spectraobtained with the MX multifiber spectrograph at the Steward 90" to findadditional giant candidates; 5 UMi and 13 Draco stars were then observedat the MMT and added to the original sample of velocity members. Inaddition, the MX spectra were used to eliminate 74 stars in thedirection of UMI and 59 stars in Draco as likely foreground dwarfs. Wedetected 7 velocity variables, defined as those stars whose probabilityof exceeding the measured X^2^ by chance is less than 1.5%. Three ofthese stars are Carbon (C) stars (UMi K and VA 335 and Draco C1); twohave emission lines (Draco CI and UMi M). We show that the C star DracoC4, with a proper motion membership probability of 7%, has a velocityconsistent with membership. It is not surprising that these C (mostlikely CH) stars are binaries because McClure has shown that mostGalactic CH stars are in binary systems. Of the remaining 35 stars, only4 are velocity variables, with measured velocity extrema of 29.1 kms^-1^ (UMi M), 7.2 km s^-1^ (Draco XI-2), 9.0 km s^-1^ (Draco 24), and8.3 km s^-1^ (Draco 473). The velocity dispersions are 10.1 +/- 1.7 kms^-1^ for UMi, and 9.9 +/- 1.4 km s^-1^ for Draco. These dispersionschange to 10.5 +/- 2.0 for UMi, and 8.2 +?- 1.3 for Draco if weeliminate the velocity variables. Our dispersion for UMi differs fromthat of Hargreaves et al. [MNRAS, 271,693 (1994b)] by 1.3σ of thecombined errors. These velocities are combined with the one-componentKing models of Pryor & Kormendy [AJ, 100,127 (1990)] to give M/L =73 for UMi, and 77 for Draco.
| Abundances and velocities for open and globular cluster giants: The data.
We present a large dataset consisting of giants in the field, and inopen and globular clusters. A total of 122 giants were observed in thefields of 8 open clusters. A total of 342 giants were observed in thefields of 25 globular clusters. A total of 36 field stars with wellknown abundances and luminosities were also observed. Radial velocitiesare determined for most giants, some of which have no photometryavailable. We have analyzed several spectral features in order to definea grid that will allow the determination of metal abundances for haloand bulge giants. The errors involved in the determination of radialvelocities and [Fe/H] are carefully examined. We find that field andopen cluster stars on one side, and globular cluster giants on the otherside, do not follow the same calibration. This is possibly due toenhanced [α/Fe] abundances in globular clusters. Therefore, wehave defined a calibration based only on globular cluster giants, validfrom [Fe/H]=-2.0 to +0.5. This calibration is carried out with thepurpose of measuring metallicities for bulge and halo giants, with theunderlying assumption that the abundance ratios of the relevant elementsrelative to iron are similar to the calibrating stars. Adopting asstandards the globular clusters NGC 288, NGC 362, NGC 1851, NGC 6356,NGC 6624, 47 Tuc, M 4 , M 3, and M 22 we derive metallicities forglobular clusters with less well known compositions, like M 28, and NGC6637. In particular, we confirm a low metallicity for M 28([Fe/H]=-1.35+/-0.2), a cluster that has a disk orbit.
| Internal kinematics of the Leo II dwarf spherodial galaxy
We have obtained radial velocities of 31 red giants in the Leo II dwarfspheroidal (dSph) galaxy using the HIRES echelle spectrograph of theKeck 10 m telescope. These stars were selected using CCD photometryobtained with the Palomar 1.5 m telescope. The radial velocity of errorswere determined from repeat measurements of Leo II giants and faintradial velocity standards; the average error for the Leo II giants is2.4 km/s. The systemic velocity of Leo II is 76.0 +/- 1.3 km/s, and thevelocity dispersion is 6.7 +/- 1.1 km/s. Adopting the standardassumptions (mass follows light, isotropy, and equilibrium) we derive aglobal V-band mass-to-light ratio (Msub tot)/Ltot = 11.1 +/-3.8, and a central value rho0/I0 = 11.6 +/- 3.2(both in solar units). These values are larger than the M/L ratiosmeasured for local stellar populations (star clusters or the solarneighborhood). Monte Carlo simulations show that a large population ofbinaries probably has not inflated a small intrinsic velocity dispersionto the observed value. A model-independent lower limit of the centralmass density of Leo II yeilds rho0,min = solar masspc-3, larger than the central luminous mass density in Leo IIfor (M/L)lum = 2.2. This demands an extensive dark halo inthe outer regions of the galaxy to account for the observed dispersion.We conclude that Leo II contains a significant dark matter component.The total mass of the dark halo is 0.9X177 solar mass,consistent with the masses inferred in all well-studied dSph galaxies.Because it is remote from the Galaxy, tide cannot plausibly affect thevelocity dispersion of Leo II. However, we cannot use these results torule out the possibility that tides may influence the kinematics ofother dSph galaxies found closer to the Milky Way.
| A radial velocity survey of the open cluster IC 4665
A radial velocity survey of the open cluster IC 4665 is reported for agroup of candidate members previously identified on the basis of propermotion and photometry. Of those candidates observed, 20 out of 42 haveradial velocities consistent with membership; these cluster memberspopulate the F5-K0 dwarf region and represent the first relativelyconclusive membership determinations for such solar-type stars in IC4665. Three new spectroscopic binary members of the cluster have beenidentified. Rotational velocities have also been derived; the v sin idistribution among IC 4665 members reveals that most apparent G dwarfmembers of IC 4665 are seen to exhibit substantial rotation (v sin igreater than 10 km/s). When compared to evolutionary isochrones, thecurrent list of intermediate-mass members appears to support earliersuggestions that IC 4665 has an age comparable to the Pleiades.
| Spectroscopy of V471 Tau. I - Review of basic properties
Spectroscopic observations of the eclipsing binary V471 Tau are reportedand analyzed. Data obtained mainly in the red band at Mt. WilsonObservatory and KPNO during the period 1975-1983 are compiled inextensive tables and graphs, and the radial velocity of the K dwarfcomponent is determined using a Griffin-mask technique. Resultsdiscussed include: (1) distance 44 + or - 6 pc, (consistent withmembership in the Hyades), (2) apparent period variation consistent witha third component, (3) emissionlike features affecting theradial-velocity determination, (4) transient features consistent withthe presence of flares, and (5) phase-coherent variation in H-alpha(attributed to the action of the white-dwarf Lyman continuum emission onthe K dwarf).
| Spectroscopic orbits of eclipsing binaries - AA UMa
High dispersion and time resolution spectra for the eclipsing binary AAUMa, obtained using an intensified Reticon, were measured bycross-correlation techniques. The spectra of the two components arefound to be very similar, and AA UMa is shown to belong to Subtype W ofW UMa binaries. The orbital elements of the system are determined andcompared with other W UMa binaries. It is found that the orbital periodis 0.48171 days and that the estimated mean mass center velocity for thesystem is -34.8 km/s. The mass ratio between the components isdetermined to be 0.54 and the magnitude difference in the wavelengthobserved is estimated to be 0.36.
| Standard Velocity Stars
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| C1 - A white-dwarf-red-dwarf spectroscopic binary
Emission lines in the spectrum of the DA white dwarf star C1 indicatedthe existence of an unresolved companion, whose spectral type wasdetermined to be approximately dM2. A radial-velocity curve for eachstar was obtained by observing the H-alpha emission line of itscompanion, and by considering the average difference between measuredand standard velocities for each star. The proper motion of C1 issimilar in magnitude to that of the Ursa Major cluster but in the wrongdirection. A lower limit for the mass of the white dwarf component iscomputed by assuming that the M dwarf is a normal main sequence star.The system shows similarities to post-common-envelope binaries.
| The establishment of 21 new ninth magnitude IAU standard radial velocity stars
Not Available
| Colors, luminosities, and motions of the nearer G-type stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1964AJ.....69..570E&db_key=AST
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משמש של הקבוצה הבאה
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | הרקולס |
| התרוממות ימנית: | 16h35m54.28s |
| סירוב: | +29°44'43.3" |
| גודל גלוי: | 8.583 |
| מרחק: | 105.263 פארסק |
| תנועה נכונה: | 4.3 |
| תנועה נכונה: | -22.4 |
| B-T magnitude: | 9.143 |
| V-T magnitude: | 8.63 |
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