We present BV CCD and APM photometry, accurate astrometry and 1859 radial velocities for 1318 stars within ~36deg of the Galactic globular cluster NGC 3201. The field and cluster populations separate unambiguously in two distinct samples since the systemic radial velocity of NGC 3201 is 494.2km/s. After removal of the 19 known NGC 3201 photometric variables in our sample, we have a database of 930 radial velocities for 420 member giants (276 of which have multiple velocity measurements) with which to identify spectroscopic binaries on the basis of radial velocity variations. The mean time span of the observations is 1.7yr, with coverage up to ~6yr for our best-studied stars. Monte Carlo simulations of the observed velocity variations have provided _upper_limits_ to the cluster binary fraction (for binaries with 0.1<=P<=5-10yr and mass ratios in the range 0.1-1) of 0.06-0.10 (circular orbits) and 0.15-0.18 (eccentric orbits). These results suggest an incidence of binarism for NGC 3201 consistent with the corresponding incidence among nearby solar-type stars having similar periods and mass ratios (0.04-0.08) and that for a small sample of other globular clusters (0.05-0.12) studied by Hut et al. (1992PASP..104..981H). The detailed analysis of the cluster dynamics, based on the data given here, are presented by Cote et al. (1995ApJ...454..788C).
File table2 contains the values of the color indices: (b-y), m1, c1, H{beta}, from the Stroemgren photometry and the observational errors on these indices as given by the Hauck and Mermiliod (1998, Cat. <II/215>). The values of Teff and logg are obtained from the Moon & Dworetsky (1985MNRAS.217..305M) calibration to which we have implemented the corrections by Castelli (1991A&A...251..106C). The errors on the parameters Teff and logg, as explained in section 3.3, are the consequence of the observational error on the photometric indices; SigmaTeff is the total error, on Teff, computed as explained in section 3.3. File table5 contains the values of the parallax, the error on the parallax, the Teff and the luminosity for the early-type star and late type star of each visual binary system. The errors on the Teff and on the luminosity are taken into account to compute for each of these parameters its minimum and maximum value. File table7 gives the values of the ages and masses computed for the early-type stars from the Schaller et al. (1993, Cat. <J/A+AS/96/269>) isochrones and Meynet at al. (1993A&AS...98..477M) models and from the Girardi et al. (2000, Cat. <J/A+AS/141/371>) models. The errors on the Teff and the luminosity are used to compute the minimum and the maximum values for the age and the mass. The last two columns concern only the primary stars with a Teff greater than 15000K for which we also compute the age and the mass using as Teff value: (Teff-500K); 500K corresponds to the systematic shift between Teff derived by using different photometric system (see Sect. 3.3). File table9 gives the values of the ages and masses computed for the late-type components from the isochrones and evolutionary tracks by D'Antona et al. (1998, web page, http://www.mporzio.astro.it/~dantona/ ) Palla and Stahler (1999ApJ...525..772P), Siess et al. (2000A&A...358..593S) and Tout et al. (1999MNRAS.310..360T). When possible, the minimum and the maximum values of these parameters are given by taking into account the errors on the Teff and on the luminosity.
We present the culmination of our near-infrared survey of the optically spectroscopically identified white dwarf stars from the McCook and Sion (1999ApJS..121....1M, see Cat. <III/235>) catalog, conducted using photometric data from the Two Micron All Sky Survey final All Sky Data Release. The color selection technique, which identifies candidate binaries containing a white dwarf and a low-mass stellar (or substellar) companion via their distinctive locus in the near-infrared color-color diagram, is demonstrated to be simple to apply and to yield candidates with a high rate of subsequent confirmation. We recover 105 confirmed binaries, and identify 27 firm candidates (19 of which are new to this work) and 21 tentative candidates (17 of which are new to this work) from the 2MASS data.
We still do not know what causes aspherical planetary nebula (PN) morphologies. A plausible hypothesis is that they are due to the presence of a close stellar or substellar companion. So far, only ~40 binary central stars of PN have been detected, almost all of them with such short periods that their binarity is revealed by photometric variability. Here we have endeavoured to discover binary central stars at any separation, thus determining the unbiased binary fraction of central stars of PN. This number, when compared to the binary fraction of the presumed parent population, can give a first handle on the origin of PN. By detecting the central stars in the I band we have searched for cool companions.
Galaxy mergers play an important role in the growth of galaxies and their supermassive black holes. Simulations suggest that tidal interactions could enhance black hole accretion, which can be tested by the fraction of binary active galactic nuclei (AGNs) among galaxy mergers. However, determining the fraction requires a statistical sample of binaries. We have identified kiloparsec-scale binary AGNs directly from high-resolution radio imaging. Inside the 92deg^2^ covered by the high-resolution Very Large Array survey of the Sloan Digital Sky Survey (SDSS) Stripe 82 field, we identified 22 grade A and 30 grade B candidates of binary radio AGNs with angular separations less than 5" (10kpc at z=0.1). Eight of the candidates have optical spectra for both components from the SDSS spectroscopic surveys and our Keck program. Two grade B candidates are projected pairs, but the remaining six candidates are all compelling cases of binary AGNs based on either emission line ratios or the excess in radio power compared to the H{alpha}-traced star formation rate. Only two of the six binaries were previously discovered by an optical spectroscopic search. Based on these results, we estimate that ~60% of our binary candidates would be confirmed once we obtain complete spectroscopic information. We conclude that wide-area high-resolution radio surveys offer an efficient method to identify large samples of binary AGNs. These radio-selected binary AGNs complement binaries identified at other wavelengths and are useful for understanding the triggering mechanisms of black hole accretion.
Current models predict that binary interactions are a major ingredient in the formation of bipolar planetary nebulae (PNe) and pre-planetary nebulae (PPNe). Despite years of radial velocity (RV) monitoring, the paucity of known binaries amongst the latter systems means data are insufficient to examine this relationship in detail. In this work, we report on the discovery of a long-period (P=2654+/-124d) binary at the centre of the Galactic bipolar PPN IRAS 08005-2356 (V510 Pup), determined from long-term spectroscopic and near-infrared time-series data. The spectroscopic orbit is fitted with an eccentricity of 0.36+/-0.05, which is similar to that of other long-period post-AGB binaries. Time-resolved H{alpha} profiles reveal high-velocity outflows (jets) with deprojected velocities up to 231^+31^_-27_km/s seen at phases when the luminous primary is behind the jet. The outflow traced by H{alpha} is likely produced via accretion on to a main-sequence companion, for which we calculate a mass of 0.63+/-0.13M_{sun}_. This discovery is one of the first cases of a confirmed binary PPN and demonstrates the importance of high-resolution spectroscopic monitoring surveys using large telescopes in revealing binarity among these systems.
Thanks to huge surveys, such as the Sloan Digital Sky Survey (SDSS), the last decade has shown a dramatic increase in the number of known quasars. In the second release of the general compiled catalogue Large Quasar Astrometric Catalogue (LQAC), 187504 objects are recorded. From this catalogue, we carry out statistical studies dealing with several topics: the astrometric accuracy of the quasars, their spatial location, the distribution of the distance to the closest neighbour, the identification of binary quasars, the completness of catalogues at a given magnitude and the estimation of the number of quasars expected to be detected by the astrometric space mission Gaia. We analyse the astrometric improvements brought by the LQAC-2 in terms of equatorial coordinates off-sets. We plot the bi-dimensional spatial distribution of the LQAC-2 quasars according to their equatorial, galactic, and ecliptic coordinates, thus exploring the anisotropy of the distribution. We compare the observed distribution of closest neighbours with the theoretical values based on a Poisson distribution. Moreover, we perform a comparison between two catalogues, the SDSS and the 2dF inside a huge common field. By extrapolating to the whole sky we deduce the number of quasars that will be detected by Gaia.
We present a sample of 221 new quasar pairs with proper transverse separations R_prop_<1h^1^Mpc over the redshift range 0.5<z<3.0, discovered from an extensive follow-up campaign to find companions around the Sloan Digital Sky Survey (Cat. <VII/243>) and 2dF QSO Redshift Survey (Cat. <VII/241>) quasars. This sample includes 26 new binary quasars with separations R_prop_<50h^-1^kpc ({thetas}<10"), more than doubling the number of such systems known. We define a statistical sample of binaries selected with homogeneous criteria and compute its selection function, taking into account sources of incompleteness. The first measurement of the quasar correlation function on scales 10h^-1^kpc<R_prop_<400h^-1^kpc is presented.
The percentage of massive main-sequence OB stars in binary systems is thought to be as high as 100%. However, very few Galactic binary red supergiants (RSGs) have been identified, despite the fact that these stars are the evolved descendants of OB stars. As shown in our recent paper, binary RSGs will likely have B-type companions, as dictated by stellar evolution considerations. Such a system will have a very unique photometric signature due to the shape of the spectral energy distribution. Using photometric cutoffs, it should therefore be possible to detect candidate RSG+B star binary systems. Here we present our spectroscopic follow-up observations of such candidates. Out of our initial list of 280 candidates in M31 and M33, we observed 149 and confirmed 63 as newly discovered RSG+B star binary systems. Additional spectra of four candidate systems in the Small Magellanic Cloud confirmed all of them as new RSG+B star binaries including the first known RSG+Be star system. By fitting BSTAR06 and MARCS model atmospheres to the newly obtained spectra, we place estimates on the temperatures and subtypes of both the B stars and RSGs. Overall, we have found 87 new RSG+B star binary systems in M31, M33 and the Small and Large Magellanic Clouds. Our future studies are aimed at determining the binary fraction of RSGs.
We describe a homogeneous catalog compilation of common proper motion stars based on GaiaDR2. A preliminary list of all pairs of stars within the radius of 100pc around the Sun with a separation less than a parsec was compiled. Also, a subset of comoving pairs, wide binary stars, was selected. The clusters and systems with multiplicity larger than 2 were excluded from consideration. The resulting catalog contains 10358 pairs of stars. The catalog selectivity function was estimated by comparison with a set of randomly selected field stars and with a model sample obtained by population synthesis. The estimates of the star masses in the catalogued objects, both components of which belong to the main-sequence, show an excess of ''twins'', composed by stars with similar masses. This excess decreases with increasing separation between components. It is shown that such an effect cannot be a consequence of the selectivity function only and does not appear in the model where star formation of similar masses is not artificially preferred. The article is based on the talk presented at the conference ''Astrometry yesterday, today, tomorrow'' (Sternberg Astronomical Institute of the Moscow State University, October 14 - 16, 2019).
