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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
| Effective temperature scale and bolometric corrections from 2MASS photometry
We present a method to determine effective temperatures, angularsemi-diameters and bolometric corrections for population I and II FGKtype stars based on V and 2MASS IR photometry. Accurate calibration isaccomplished by using a sample of solar analogues, whose averagetemperature is assumed to be equal to the solar effective temperature of5777 K. By taking into account all possible sources of error we estimateassociated uncertainties to better than 1% in effective temperature andin the range 1.0-2.5% in angular semi-diameter for unreddened stars.Comparison of our new temperatures with other determinations extractedfrom the literature indicates, in general, remarkably good agreement.These results suggest that the effective temperaure scale of FGK starsis currently established with an accuracy better than 0.5%-1%. Theapplication of the method to a sample of 10 999 dwarfs in the Hipparcoscatalogue allows us to define temperature and bolometric correction (Kband) calibrations as a function of (V-K), [m/H] and log g. Bolometriccorrections in the V and K bands as a function of T_eff, [m/H] and log gare also given. We provide effective temperatures, angularsemi-diameters, radii and bolometric corrections in the V and K bandsfor the 10 999 FGK stars in our sample with the correspondinguncertainties.
| Statistical Constraints for Astrometric Binaries with Nonlinear Motion
Useful constraints on the orbits and mass ratios of astrometric binariesin the Hipparcos catalog are derived from the measured proper motiondifferences of Hipparcos and Tycho-2 (Δμ), accelerations ofproper motions (μ˙), and second derivatives of proper motions(μ̈). It is shown how, in some cases, statistical bounds can beestimated for the masses of the secondary components. Two catalogs ofastrometric binaries are generated, one of binaries with significantproper motion differences and the other of binaries with significantaccelerations of their proper motions. Mathematical relations betweenthe astrometric observables Δμ, μ˙, and μ̈ andthe orbital elements are derived in the appendices. We find a remarkabledifference between the distribution of spectral types of stars withlarge accelerations but small proper motion differences and that ofstars with large proper motion differences but insignificantaccelerations. The spectral type distribution for the former sample ofbinaries is the same as the general distribution of all stars in theHipparcos catalog, whereas the latter sample is clearly dominated bysolar-type stars, with an obvious dearth of blue stars. We point outthat the latter set includes mostly binaries with long periods (longerthan about 6 yr).
| Properties of the close binary and circumbinary torus of the Red Rectangle
New diffraction-limited speckle images of the RedRectangle in the wavelength range 2.1-3.3 mu m with angularresolutions of 44-68 mas (Tuthill et al. \cite{Tuthill_etal2002}) andprevious speckle images at 0.7-2.2 mu m (Osterbart et al.\cite{Osterbart_etal1997}; Men'shchikov et al.\cite{Men'shchikov_etal1998}) revealed well-resolved bright bipolaroutflow lobes and long X-shaped spikes originating deep inside theoutflow cavities. This set of high-resolution images stimulated us toreanalyze all infrared observations of the RedRectangle using our two-dimensional radiative transfer code.The high-resolution images imply a geometrically and optically thicktorus-like density distribution with bipolar conical cavities and areinconsistent with the flat disk geometry frequently used to visualizebipolar nebulae. The new detailed modeling, together with estimates ofthe interstellar extinction in the direction of the RedRectangle enabled us to more accurately determine one of thekey parameters, the distance D ~ 710 pc with model uncertainties of 70pc, which is twice as far as the commonly used estimate of 330 pc. Thecentral binary is surrounded by a compact, massive (M ~ 1.2Msun), very dense dusty torus with hydrogen densitiesreaching nH ~ 2.5 x 1012 cm-3(dust-to-gas mass ratio \rhod/\rho ~ 0.01). The model impliesthat most of the dust mass in the dense torus is in very large particlesand, on scales of more than an arcsecond, the polar outflow regions aredenser than the surrounding medium. The bright component of thespectroscopic binary HD 44179 is a post-AGB star withmass M\star ~ 0.57 Msun, luminosityL\star ~ 6000 Lsun, and effective temperatureT\star ~ 7750 K. Based on the orbital elements of the binary,we identify its invisible component with a helium white dwarf withMWD ~ 0.35 Msun, LWD ~ 100Lsun, and TWD ~ 6 x 104 K. The hotwhite dwarf ionizes the low-density bipolar outflow cavities inside thedense torus, producing a small H II region observed at radiowavelengths. We propose an evolutionary scenario for the formation ofthe Red Rectangle nebula, in which the binaryinitially had 2.3 and 1.9 Msun components at a separation of~ 130 Rsun. The nebula was formed in the ejection of a commonenvelope after Roche lobe overflow by the present post-AGB star.
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