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Proper-motion binaries in the Hipparcos catalogue. Comparison with radial velocity data
Context: .This paper is the last in a series devoted to the analysis ofthe binary content of the Hipparcos Catalogue. Aims: .Thecomparison of the proper motions constructed from positions spanning ashort (Hipparcos) or long time (Tycho-2) makes it possible to uncoverbinaries with periods of the order of or somewhat larger than the shorttime span (in this case, the 3 yr duration of the Hipparcos mission),since the unrecognised orbital motion will then add to the propermotion. Methods: .A list of candidate proper motion binaries isconstructed from a carefully designed χ2 test evaluatingthe statistical significance of the difference between the Tycho-2 andHipparcos proper motions for 103 134 stars in common between the twocatalogues (excluding components of visual systems). Since similar listsof proper-motion binaries have already been constructed, the presentpaper focuses on the evaluation of the detection efficiency ofproper-motion binaries, using different kinds of control data (mostlyradial velocities). The detection rate for entries from the NinthCatalogue of Spectroscopic Binary Orbits (S_B^9) is evaluated, as wellas for stars like barium stars, which are known to be all binaries, andfinally for spectroscopic binaries identified from radial velocity datain the Geneva-Copenhagen survey of F and G dwarfs in the solarneighbourhood. Results: .Proper motion binaries are efficientlydetected for systems with parallaxes in excess of ~20 mas, and periodsin the range 1000-30 000 d. The shortest periods in this range(1000-2000 d, i.e., once to twice the duration of the Hipparcos mission)may appear only as DMSA/G binaries (accelerated proper motion in theHipparcos Double and Multiple System Annex). Proper motion binariesdetected among S_B9 systems having periods shorter than about400 d hint at triple systems, the proper-motion binary involving acomponent with a longer orbital period. A list of 19 candidate triplesystems is provided. Binaries suspected of having low-mass(brown-dwarf-like) companions are listed as well. Among the 37 bariumstars with parallaxes larger than 5 mas, only 7 exhibit no evidence forduplicity whatsoever (be it spectroscopic or astrometric). Finally, thefraction of proper-motion binaries shows no significant variation amongthe various (regular) spectral classes, when due account is taken forthe detection biases.Full Table [see full textsee full text] is only available in electronicform at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/464/377
| uvby-β photometry of high-velocity and metal-poor stars. XI. Ages of halo and old disk stars
New uvby-β data are provided for 442 high-velocity and metal-poorstars; 90 of these stars have been observed previously by us, and 352are new. When combined with our previous two photometric catalogues, thedata base is now made up of 1533 high-velocity and metal-poor stars, allwith uvby-β photometry and complete kinematic data, such as propermotions and radial velocities taken from the literature. Hipparcos, plusa new photometric calibration for Mv also based on theHipparcos parallaxes, provide distances for nearly all of these stars;our previous photometric calibrations give values for E(b-y) and [Fe/H].The [Fe/H], V(rot) diagram allows us to separate these stars intodifferent Galactic stellar population groups, such as old-thin-disk,thick-disk, and halo. The X histogram, where X is our stellar-populationdiscriminator combining V(rot) and [Fe/H], and contour plots for the[Fe/H], V(rot) diagram both indicate two probable components to thethick disk. These population groups and Galactic components are studiedin the (b-y)0, Mv diagram, compared to theisochrones of Bergbusch & VandenBerg (2001, ApJ, 556, 322), toderive stellar ages. The two thick-disk groups have the meancharacteristics: ([Fe/H], V(rot), Age, σW') ≈ (-0.7dex, 120 km s-1, 12.5 Gyr, 62.0 km s-1), and≈(-0.4, 160, 10.0, 45.8). The seven most metal-poor halo groups,-2.31 ≤ [Fe/H] ≤ -1.31, show a mean age of 13.0 ± 0.2(mean error) Gyr, giving a mean difference from the WMAP results for theage of the Universe of 0.7 ± 0.3 Gyr. These results for the agesand components of the thick disk and for the age of the Galactic halofield stars are discussed in terms of various models and ideas for theformation of galaxies and their stellar populations.
| A CCD imaging search for wide metal-poor binaries
We explored the regions within a radius of 25 arcsec around 473 nearby,low-metallicity G- to M-type stars using (VR)I optical filters andsmall-aperture telescopes. About 10% of the sample was searched up toangular separations of 90 arcsec. We applied photometric and astrometrictechniques to detect true physical companions to the targets. The greatmajority of the sample stars was drawn from the Carney-Latham surveys;their metallicities range from roughly solar to [Fe/H] = -3.5 dex. OurI-band photometric survey detected objects that are between 0 and 5 magfainter (completeness) than the target stars; the maximum dynamicalrange of our exploration is 9 mag. We also investigated the literature,and inspected images from the Digitized Sky Surveys to complete oursearch. By combining photometric and proper motion measurements, weretrieved 29 previously known companions, and identified 13 new propermotion companions. Near-infrared 2MASS photometry is provided for thegreat majority of them. Low-resolution optical spectroscopy (386-1000nm) was obtained for eight of the new companion stars. Thesespectroscopic data confirm them as cool, late-type, metal-depleteddwarfs, with spectral classes from esdK7 to sdM3. After comparison withlow-metallicity evolutionary models, we estimate the masses of theproper motion companion stars to be in the range 0.5-0.1Mȯ. They are moving around their primary stars atprojected separations between 32 and 57 000 AU. These orbitalsizes are very similar to those of solar-metallicity stars of the samespectral types. Our results indicate that about 15% of the metal-poorstars have stellar companions in wide orbits, which is in agreement withthe binary fraction observed among main sequence G- to M-type stars andT Tauri stars.Based on observations made with the IAC80 telescope operated on theisland of Tenerife by the Instituto de Astrofísica de Canarias inthe Spanish Observatorio del Teide; also based on observations made withthe 2.2 m telescope of the German-Spanish Calar Alto Observatory(Almería, Spain), the William Herschel Telescope (WHT) operatedon the island of La Palma by the Isaac Newton Group in the SpanishObservatorio del Roque de los Muchachos (ORM) of the Instituto deAstrofísica de Canarias; and the Telescopio Nazionale Galileo(TNG) at the ORM.The complete Table 1 is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/419/167
| The Mass Ratio Distribution in Main-Sequence Spectroscopic Binaries Measured by Infrared Spectroscopy
We report infrared spectroscopic observations of a large well-definedsample of main-sequence, single-lined spectroscopic binaries to detectthe secondaries and derive the mass ratio distribution of short-periodbinaries. The sample consists of 51 Galactic disk spectroscopic binariesfound in the Carney and Latham high proper motion survey, with primarymasses in the range 0.6-0.85 Msolar. Our infraredobservations detect the secondaries in 32 systems, two of which havemass ratios, q=M2/M1, as low as ~0.20. Togetherwith 11 systems previously identified as double-lined binaries byvisible light spectroscopy, we have a complete sample of 62 binaries, ofwhich 43 are double lined. The mass ratio distribution is approximatelyconstant over the range q=1.0-0.3. The distribution appears to rise atlower q values, but the uncertainties are sufficiently large that wecannot rule out a distribution that remains constant. The massdistribution derived for the secondaries in our sample and that of theextrasolar planets apparently represent two distinct populations.
| On the Mass-Ratio Distribution of Spectroscopic Binaries
In this paper we derive the mass-ratio and secondary-mass distributionsof a large, well-defined, complete sample of 129 spectroscopic binarieswith periods between 1 and 2500 days. The binaries, whose orbits werepublished recently, were detected by a systematic radial-velocity surveyof a sample of more than 1400 large proper motion stars. Three featuresstand out in the mass-ratio distribution: a rise as the mass ratio goesdown to q~0.2, a sharp drop below q~0.2, and a smaller peak at q~0.8.Another way to characterize the results is to state that thedistribution includes two ``populations,'' one with a high asymmetricpeak at q~0.2 and another with a smaller peak at q~0.8, while theminimum between the two populations is centered at q~0.55. The size ofthe binary sample allows us to divide it into two subsamples and lookfor differences in the mass-ratio distributions of the two subsamples.We performed two different divisions: one into Galactic halo versus diskpopulations, and the other into high- and low-mass primary stars (aboveand below 0.67 Msolar). The former division yieldsdifferences with moderate statistical significance of 88%, while thelatter is more significant at a level of 97%. Our analysis suggests thatthe rise toward low mass ratios does not appear in the mass-ratiodistribution of the halo binaries. The other separation shows a broadpeak at mass ratio of q~0.8-1 for the subsample of binaries withlow-mass primaries but no corresponding peak in the subsample withhigh-mass primaries. We discuss our findings and their application totheories of binary formation.
| Improved Astrometry and Photometry for the Luyten Catalog. II. Faint Stars and the Revised Catalog
We complete construction of a catalog containing improved astrometry andnew optical/infrared photometry for the vast majority of NLTT starslying in the overlap of regions covered by POSS I and by the secondincremental Two Micron All Sky Survey (2MASS) release, approximately 44%of the sky. The epoch 2000 positions are typically accurate to 130 mas,the proper motions to 5.5 mas yr-1, and the V-J colors to0.25 mag. Relative proper motions of binary components are measured to 3mas yr-1. The false-identification rate is ~1% for11<~V<~18 and substantially less at brighter magnitudes. Theseimprovements permit the construction of a reduced proper-motion diagramthat, for the first time, allows one to classify NLTT stars intomain-sequence (MS) stars, subdwarfs (SDs), and white dwarfs (WDs). We inturn use this diagram to analyze the properties of both our catalog andthe NLTT catalog on which it is based. In sharp contrast to popularbelief, we find that NLTT incompleteness in the plane is almostcompletely concentrated in MS stars, and that SDs and WDs are detectedalmost uniformly over the sky δ>-33deg. Our catalogwill therefore provide a powerful tool to probe these populationsstatistically, as well as to reliably identify individual SDs and WDs.
| Spectroscopic binary orbits from photoelectric radial velocities. Paper 173: HD 111306, HD 113023, HD 117901, and HD 142474.
Not Available
| A Survey of Proper-Motion Stars. XV. Orbital Solutions for 34 Double-lined Spectroscopic Binaries
We present orbital solutions for 34 double-lined spectroscopic binariesfound in the Carney-Latham sample of 1464 stars selected for high propermotion. We use TODCOR, a two-dimensional correlation technique, toextract the velocities for the primary and secondary stars and theirlight ratio. For our single-order echelle spectra, obtained with theCenter for Astrophysics Digital Speedometers, we find that we can reachsecondaries that are as much as 2 mag fainter than their primaries. Theratio of the primary to secondary velocity residuals from the orbitalfit equals approximately the secondary-to-primary light ratio, as wouldbe expected for the photon-limited case. We use our mass and lightratios to evaluate the mass-luminosity relation for metal-poormain-sequence dwarfs in the mass range 0.55-0.8 Msolar. Weassume an L~Mβ relation and find that the exponentat around 5200 Å is 7.4+/-0.6. We find this is in good agreementwith the slope of the corresponding theoretical MV-M 14Gyr isochrones from the VandenBerg & Bell models for metal-poorstars. Some of the results presented here used observations made withthe Multiple Mirror Telescope, a facility operated jointly by theUniversity of Arizona and the Smithsonian Institution.
| beta Centauri: An eccentric binary with two beta Cep-type components
We introduce our observational study of the orbital motion and theintrinsic variability of the double-lined spectroscopic binary beta Cen.Using 463 high signal-to-noise, high-resolution spectra obtained over atimespan of 12 years it is shown that the radial velocity of beta Cenvaries with an orbital period of 357.0 days. We derive for the firsttime the orbital parameters of beta Cen and find a very eccentric orbit(e=0.81) and similar component masses with a mass ratioM1/M2=1.02. beta Cen forms a challenge for currentevolution scenarios in close binaries and it is also a puzzle how amassive binary with such a large eccentricity could have formed in thefirst place. Both the primary and the secondary exhibit line-profilevariations. A period analysis performed on the radial velocityvariations of the primary after prewhitening the orbital motion leads tothe detection of at least 3 pulsation frequencies while the star doesnot show any periodic photometric variability. Based on observationsobtained with the ESO CAT/CES telescope and the Swiss Euler/CORALIEtelescope, both situated at La Silla, Chile.
| The Hyades Binary 51 Tauri: Spectroscopic Detection of the Primary, the Distance to the Cluster, and the Mass-Luminosity Relation
51 Tauri has long been known as a double-lined spectroscopic binary(orbital period = 11 yr) with the peculiarity that only the velocitiesof the secondary component could be measured. We report here newspectroscopic observations of this system that have enabled us tomeasure velocities for the rapidly rotating primary using TODCOR, atwo-dimensional cross-correlation technique, and we have derived adouble-lined orbit. In addition, 51 Tau is a visual binary resolved byspeckle interferometry. By combining the astrometric and spectroscopicdata, we have obtained the first complete visual-spectroscopic solutionfor the system, from which we derive the orbital parallax ( pi orb =0."0179 +/- 0."0006) and the individual masses (MA = 1.80 +/- 0.13Mȯ and MB = 1.46 +/- 0.18 Mȯ). Based on this orbital parallax,we use relative proper motions for a representative sample of clustermembers to obtain a distance modulus for the cluster of m - M = 3.40 +/-0.07 (47.8 +/- 1.6 pc). We compare the empirical mass-luminosityrelation from all available direct mass determinations with recenttheoretical models, and we take advantage of the unusual opportunitythat we have absolute luminosities and colors to derive an age estimateof 600 Myr for the Hyades, by comparing with stellar evolution modelswithout any arbitrary adjustments.
| Study of Spectroscopic Binaries with TODCOR. II. The Highly Eccentric Binary HD 2909
Abstract image available at:http://adsabs.harvard.edu/abs/1995ApJ...449..909M
| A Visual-Spectroscopic Orbit for the Binary Sigma 248
Spectroscopic studies of visual binaries with angular separations lessthan about 1" have so far had great difficulty in providing theindividual radial velocities for the components, because of the smallvelocity differences that are typical in these systems. The recentintroduction of TODCOR, a two-dimensional cross-correlation technique(Zucker and Mazeh 1994), promises to change the situation, bridging thegap between the wider pairs resolvable at the telescope, and theclassical double-lined spectroscopic binaries, with large velocityamplitudes. We present the first example of an application of TODCOR tosuch a case: the study of the close visual pair Sigma 248. We report ourhigh-resolution low signal-to-noise spectroscopic observations of thesystem over the past seven years, which happen to cover the periastronpassage. Using TODCOR, we are able to disentangle the light from the twostars in our composite spectra and obtain radial velocities for bothcomponents despite the small velocity difference. By combining ourvelocities with all available astrometric observations of the pair wederive for the first time a visual-spectroscopic orbital solution, witha period of about 310 years. We obtain also the orbital parallax of thesystem, corresponding to a distance of 60 parsecs, as well as theindividual masses, which are consistent with early K-type dwarfs.(SECTION: Stars)
| A survey of proper motion stars. 12: an expanded sample
We report new photometry and radial velocities for almost 500 stars fromthe Lowell Proper Motion Catalog. We combine these results with ourprior sample and rederive stellar temperatures based on the photometry,reddening, metallicities (using chi squared matching of our 22,500 lowSignal to Noise (S/N) high resolution echelle spectra with a grid ofsynthetic spectra), distances, space motions, and Galactic orbitalparameters for 1269 (kinematics) and 1261 (metallicity) of the 1464stars in the complete survey. The frequency of spectroscopic binariesfor the metal-poor ((m/H) less than or equal to -1.2) stars with periodsshorter than 3000 days is at least 15%. The spectroscopic binaryfrequency for metal-rich stars ((m/H) greater than -0.5) appears to belower, about 9%, but this may be a selection effect. We also discussspecial classes of stars, including treatment of the double-linedspectroscopic binaries, and identification of subgiants. Four possiblenew members of the class of field blue stragglers are noted. We pointout the detection of three possible new white dwarfs, six broad-lined(binary) systems, and discuss briefly the three already knownnitrogen-rich halo dwarfs. The primary result of this paper will beavailable on CD-ROM, in the form of a much larger table.
| The Highly Eccentric Binary HD 2909
TODCOR is a new two-dimensional correlation technique to extract theradial velocities of the two components of double-line spectroscopicbinaries. In this work we apply TODCOR for the first time to a realsystem --- the highly eccentric binary HD 2909. TODCOR has derivedsuccessfully the velocities of the two components, even at phases whenthe velocity difference between the primary and the secondary was verysmall. We present an orbital solution which shows that HD 2909 is aspectroscopic binary with a period of 2127 days and an eccentricity of0.951 +/- 0.002. This value is second only to the highest eccentricityknown for a spectroscopic binary --- 0.9752 +/- 0.0003, which wasrecently found by Duquennoy et al. (A&A, 254, L13, 1992) for Gls 586A.The discovery of the high eccentricity of Gls 586A and HD 2909 raisessome interesting questions with regard to the tidal evolution of suchsystems. These questions and the tidal history of HD 2909 are discussed.We show that the tidal interaction of HD 2909 was not strong enough toproduce throughout the system lifetime any substantial change in thesemimajor axis and the eccentricity of the orbit, nor in the stellarrotation.
| A survey of proper motion stars. IX - The galactic halo's metallicity gradient
Using data already presented for a survey of proper motion stars and theBahcall, Schmidt, and Soneira (1983) model of the Galaxy, Galacticorbital parameters are computed, including planar and three-dimensionaleccentricities, apo- and perigalacticon distances, and maximum distancesreached above/below the plane, based on extreme values for R and theabsolute value of Z over 15 azimuthal periods. The orbital data are usedto bin the survey's stars by apogalacticon and maximum Z distances. Inan attempt to isolate a halo population sample, analyses are restrictedto those stars that lag behind the local standard of the rest's circularorbital velocity by 50, 100, 150, and 200 km/s. The mean metallicitiesof the stars in a variety of Rapo and Zmax bins are compared .
| A survey of proper-motion stars. III - Reddenings, distances, and metallicities
Further data on the Lowell proper-motion stars surveyed by Carney andLatham (1987) are presented. Both new and published photometry aresummarized for 286 of these stars. Included are R-I data for 64 stars,uvby (or by) data for 221 stars (of which are included new results for152 stars), and JHK (or K) data for 238 stars (of which are included newresults for 180 stars). The procedures used to estimate the reddeningand photometric parallax of each star are discussed. The metallicitiesfor 818 stars, based on 5795 spectra, determined using a new method,described in an earlier paper, which compares synthetic spectra to thelow-signal-to-noise spectra obtained for radial velocities are alsopresented. The reddening, distance, and metallicity are interdependentand have been determined in a self-consistent manner.
| Candidates for spectroscopic binaries found in the Mount Wilson Halo-Mapping Program
Forty-six spectroscopic binary candidates found in the radial-velocitydata base of the Mount Wilson Halo-Mapping Project are identified. Acomparison of data obtained by Carney and Latham (1987) and Fouts andSandage (1986) indicates 309 overlapping stars, of which 101 are listedas possible velocity variables by Carney and Latham. The distribution ofresiduals for the 101 suspected binaries is sigma = 8.0 km/s; if theseturn out to be binaries, they will probably be velocity variables ofvery low amplitude.
| New subdwarfs. IV - UBV photometry of 1690 high-proper-motion stars
A photometric list of 1690 stars of known high proper motion is used tosearch for potential high-velocity stars of various metallicity valuesin order to find candidates for trigonometric programs on subdwarfs andto enlarge the sample with which to study the relation between stellarkinematics and metal abundance. A list of 113 stars with tangentialspace velocities of 300 km/s or greater is obtained, the highesttangential velocity relative to the sun being 630 km/s. By using thevariation of the tangential velocity with longitude and adopting thegalactic rotation at the solar circle to be 220 km/s, the rotation ofthe subdwarf system is estimated at 0 + or - 50 km/s from the transversevelocity alone, in agreement with determinations based on other methods.
| Lowell proper motions III : proper motion survey of the Northern Hemisphere with the 13-inch photographic telescope of the Lowell Observatory
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