scholarly journals Tidal Circularization Among the Close Binaries in M67

1992 ◽  
Vol 151 ◽  
pp. 471-472
Author(s):  
David W. Latham ◽  
Robert D. Mathieu ◽  
Alejandra A. E. Milone ◽  
Robert J. Davis
Keyword(s):  
Main Sequence ◽  
Open Cluster ◽  
Radial Velocities ◽  
Spectroscopic Binaries ◽  
Close Binaries ◽  
To Come ◽  
Mirror Telescope

In 1971 Roger Griffin and Jim Gunn began monitoring the radial velocities of most of the members brighter than the main-sequence turnoff in the old open cluster M67, primarily using the 200-inch Hale Telescope. In 1982 the torch was passed to Dave Latham and Bob Mathieu, who began monitoring many of the same stars with the 1.5-meter Tillinghast Reflector and the Multiple-Mirror Telescope on Mt. Hopkins. We have successively combined these two sets of data, plus some additional CORAVEL velocities kindly provided by Michel Mayor, to obtain 20 years of time coverage (e.g. Mathieu et al. 1986). Among the stars brighter than magnitude V = 12.7 we have already published orbits for 22 spectroscopic binaries (Mathieu et al. 1990). At Mt. Hopkins an extension of this survey to many of the cluster members down to magnitude V = 15.5 has already yielded thirteen additional orbital solutions, with the promise of many more to come.

scholarly journals Spectroscopic Binaries in the Open Cluster M67

1992 ◽  
Vol 135 ◽  
pp. 155-157 ◽  
Author(s):  
David W. Latham ◽  
Robert D. Mathieu ◽  
Alejandra A.E. Milone ◽  
Robert J. Davis
Keyword(s):  
Circular Orbit ◽  
Main Sequence ◽  
Open Cluster ◽  
Radial Velocities ◽  
Spectroscopic Binaries ◽  
Eccentric Orbit ◽  
Circular Orbits ◽  
Blue Stragglers ◽  
Short Period ◽  
Blue Straggler

AbstractFor almost 400 members of M67 we have accumulated about 5,000 precise radial velocities. Already we have orbital solutions for more than 32 spectroscopic binaries in M67. Many of these orbits were derived by combining the Palomar and CfA observations, thus extending the time coverage to more than 20 years. The distribution of eccentricity versus period shows evidence for tidal circularization on the main sequence. The transition from circular orbits is fairly clean. Excluding the blue stragglers, the first eccentric orbit has a period of 11.0 days, while the last circular orbit has a period of 12.4 days. For longer periods the distribution of eccentricity is the same as for field stars. The blue straggler S1284 has an eccentric orbit despite its short period of 4.2 days.

Spectroscopic Binaries in the Halo

1992 ◽  
Vol 135 ◽  
pp. 158-160 ◽  
Author(s):  
David W. Latham ◽  
Tsevi Mazeh ◽  
Robert P. Stefanik ◽  
Robert J. Davis ◽  
Bruce W. Carney ◽  
...  
Keyword(s):  
Proper Motion ◽  
Main Sequence ◽  
Radial Velocities ◽  
Spectroscopic Binaries ◽  
Variable Velocity ◽  
Short Period ◽  
The Galaxy ◽  
Elliptical Orbits

AbstractFor almost 1500 stars in the Carney-Latham survey of proper-motion stars we have accumulated about 20,000 precise radial velocities. Already we have orbital solutions for more than 150 spectroscopic binaries in this sample, and about 100 additional binary candidates with variable velocity. We find that among the metal-poor halo field stars in this sample the frequency of short-period spectroscopic binaries is indistinguishable from that of the disk. The distribution of eccentricity versus period shows evidence for tidal circularization on the main sequence. For the binaries more metal poor than [m/H] = −1.6 there is a clean transition from circular to elliptical orbits at a period of about 19 days. For longer periods the distribution of eccentricity is the same as for stars in the disk of the Galaxy.

scholarly journals The Cluster NGC 330 in the SMC: Radial Velocities of Individual Stars

1980 ◽  
Vol 85 ◽  
pp. 339-339
Author(s):  
M. W. Feast ◽  
C. Black
Keyword(s):  
Standard Deviation ◽  
Main Sequence ◽  
Velocity Dispersion ◽  
Radial Velocities ◽  
Spectroscopic Binaries ◽  
Early Type ◽  
Late Type ◽  
Main Sequence Stars ◽  
Image Tube ◽  
Cloud Clusters

Radial velocities based on 81 image tube spectra at 30 Å mm−1 are given for 25 stars (17 early type supergiants or upper main sequence stars and 8 late type stars) in the young SMC cluster NGC 330. An upper (one standard deviation) limit to the velocity dispersion is found to be 2 km s−1. The mass-to-light ratio is likely to be less than 0.1 in solar units. Results for other young Magellanic Cloud clusters derived on the assumption that they are tidally limited are consistent with this result. Spectroscopic binaries with semi-amplitudes, K, greater than about 10 km s−1 appear to be rare or absent amongst the stars studied.

scholarly journals NIR Spectroscopy of the Most Massive Open Cluster in the Galaxy: Westerlund 1

2007 ◽  
Vol 3 (S246) ◽  
pp. 113-114 ◽  
Author(s):  
S. Mengel ◽  
L. E. Tacconi-Garman
Keyword(s):  
Cluster Expansion ◽  
Main Sequence ◽  
Velocity Dispersion ◽  
Open Cluster ◽  
Nir Spectroscopy ◽  
Radial Velocities ◽  
Main Sequence Stars ◽  
Central Wavelength ◽  
Cluster Mass ◽  
The Galaxy

AbstractUsing ISAAC/VLT, we have obtained individual spectra of all NIR-bright stars in the central 2′ × 2′ of the cluster Westerlund 1 (Wd 1) with a resolution of R ≈ 9000 at a central wavelength of 2.30 μm. This allowed us to determine radial velocities of ten post-main-sequence stars, and from these values a velocity dispersion. Assuming virial equilibrium, the dispersion of σ = 8.4 km/s leads to a total dynamical cluster mass of 1.25 × 105M⊙, comparable to the photometric mass of the cluster. There is no extra-virial motion which would have to be interpreted as a signature of cluster expansion or dissolution.

scholarly journals Strongly magnetic Ap stars in the Gaia DR2 Hertzsprung-Russell diagram

2019 ◽  
Vol 628 ◽  
pp. A81 ◽  
Author(s):  
R.-D. Scholz ◽  
S. Drew Chojnowski ◽  
S. Hubrig
Keyword(s):  
Main Sequence ◽  
Open Cluster ◽  
Quality Criterion ◽  
Quality Criteria ◽  
Quality Parameters ◽  
Unit Weight ◽  
Close Binaries ◽  
Cluster Membership ◽  
Ap Stars ◽  
Gaia Dr2

Context. Knowing the distribution of strongly magnetic Ap stars in the Hertzsprung-Russell diagram (HRD) allows us to study the evolution of their magnetic fields across the main sequence (MS). With a newly extended Ap star sample from APOGEE and available Gaia DR2 data, we can now critically review the results of previous studies based on HIPPARCOS data. Aims. To investigate our targets in the Gaia DR2 HRD, we need to define astrometric and photometric quality criteria to remove unreliable data from the HRD. Methods. We used the Gaia DR2 renormalised unit weight error RUWE as our main quality criterion. We considered known (close) binaries in our sample compared to their (partly affected) astrometry and used the Gaia DR2 data to find common parallax and proper motion (CPPM) wide companions and open cluster members. We studied G, BP, and RP variability amplitudes and their significance as a function of magnitude. In colour-magnitude diagrams (CMDs) with absolute G magnitude (determined from inverted parallax) versus BP − RP colour and HRDs, where BP − RP is replaced by effective temperature, we studied the appearance of outliers with respect to their astrometric quality, binarity, and variability. Results. We present a catalogue of 83 previously known and 154 new strongly magnetic Ap stars with Gaia DR2 data, including astrometric quality parameters, binary flags, information on cluster membership, variability amplitudes, and data from HIPPARCOS. Our astrometrically cleaned subsamples include 47 and 46 old and new Ap stars with parallaxes > 2 mas. Most of the known 26 binaries among all 237 stars and 14 out of 15 CMD/HRD outliers were excluded by astrometric criteria. The remaining 11 known binaries and a few highly variable objects mainly appear in the bright and red CMD/HRD parts. A CMD based on HIPPARCOS photometry and Gaia DR2 parallaxes shows a much more narrow distribution in the absolute V magnitudes of 75 common Ap stars over the full B − V colour range than the corresponding CMD based on HIPPARCOS parallaxes.

scholarly journals Dynamics of the Open Cluster NGC 188: A Comparison to an N-body Simulation of M67

2007 ◽  
Vol 3 (S246) ◽  
pp. 111-112
Author(s):  
Aaron M. Geller ◽  
Robert D. Mathieu ◽  
Hugh C. Harris ◽  
Robert D. McClure
Keyword(s):  
Radial Velocity ◽  
Binary Stars ◽  
Main Sequence ◽  
Open Cluster ◽  
Spectroscopic Binaries ◽  
Solar Mass ◽  
Dynamical Study ◽  
Data Set ◽  
Spatial Coverage ◽  
Orbital Periods

AbstractWe present a detailed dynamical study of the old (7 Gyr) open cluster NGC 188. Our combined radial-velocity data set spans a baseline of 35 years, a magnitude range of 12 ≤ V ≤ 16.5, and a 1° diameter region on the sky. Our magnitude limits include solar-mass main-sequence stars, subgiants, giants, and blue stragglers, and our spatial coverage extends radially to 11.5 core radii. We have measured radial velocities for 1014 stars in the direction of NGC 188 with a precision of 0.4 km s−1, and have calculated radial-velocity membership probabilities for stars with ≥ 3 measurements. We find 420 stars to be high-probability cluster members, including 137 spectroscopic binaries. These detectable binaries all have orbital periods of less than 104 days, and thus are hard. We have derived orbit solutions for 67 member binary stars, and use our 35 main-sequence binaries with orbit solutions to compare the eccentricity and period distributions with simulated observations of the Hurley et al. (2005) model of M67 (4.5 Gyr). We also compare the spatial distributions of cluster member populations.

scholarly journals Can Evolution in Close Binaries Account for the Blue Stragglers in M67?

1992 ◽  
Vol 151 ◽  
pp. 473-474
Author(s):  
Alejandra A. E. Milone ◽  
David W. Latham ◽  
Robert D. Mathieu ◽  
Jon A. Morse ◽  
Robert J. Davis
Keyword(s):  
Open Cluster ◽  
Radial Velocities ◽  
Close Binaries ◽  
Similar Reduction ◽  
Blue Stragglers ◽  
The Past

For the past 9 years we have been monitoring the radial velocities of 13 blue stragglers in the old open cluster M67. For the 9 blue stragglers with rotational velocities no larger than about 100 km s−1 we have used the CfA digital speedometers to measure more than 500 radial velocities. To get reliable velocity correlations we use synthetic rotating templates computed from a grid of Kurucz model atmospheres. Four of the blue stragglers rotate too rapidly to allow successful velocity correlations with the CfA instruments. For three of these we have used a CCD spectrograph at Kitt Peak and similar reduction procedures (Morse et al. 1991.

Radial Velocities, Binarity, and Kinematic Membership in the Open Cluster NGC 2516

2000 ◽  
Vol 119 (5) ◽  
pp. 2296-2302 ◽  
Author(s):  
Jorge Federico González ◽  
Emilio Lapasset
Keyword(s):  
Open Cluster ◽  
Radial Velocities

scholarly journals A Plan for a New Generation 2 m-Class Telescope in Indonesia

1984 ◽  
Vol 80 ◽  
pp. 409-410
Author(s):  
Karel A. Van Der Hucht
Keyword(s):  
Double Star ◽  
Radial Velocities ◽  
Spectroscopic Binaries ◽  
Theoretical Research ◽  
60Th Anniversary ◽  
Additional Tool ◽  
New Generation

AbstractOne of the prime astrophysical interests of the Observatorium Bosscha is, and has always been, double star research: visual double star research with the double-60 cm Zeiss telescope (dedicated in 1928), and theoretical research of evolved massive spectroscopic binaries (since 1972). For one thing, this is the very reason that this IAU Colloquium No. 80, celebrating the 60th anniversary of the Observatorium Bosscha in Lembang, is devoted to binary astrophysics.Up to now, visual, photographic, and photometric tools have been used for binary research at the Observatorium Bosscha. An important, essential additional tool for binary research is spectrographic equipment, in order to measure radial velocities of binary components.

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