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Astrometric CCD observations of visual components of double and multiple stars were performed using the RI MAO Axial Meridian Circle (AMC) with new Apogee Alta AI-F8300 CCD camera mounted at the telescope in 2018. Observations were carried out automatically in drift- scan mode using a standard R filter. Objects for observational program were selected from the Washington Double Star Catalog (WDS). During the 23 nights, 983 observations of 579 double and multiple systems from the WDS catalog were obtained. Astrometric reductions of the observations showed high accuracy, with an average error of one position about 0.1" in right ascension and declination for stars up to 16 mag , which were observed more than 3 times. The purpose of our study was to measure the parameters of the mutual configuration of pairs from the original images and to draw some conclusions about the physical connection of the components in the selected systems. The measurement array that will be sent to the WDS database includes values of positional angle, angular separation, stellar magnitude difference, and epoch of the observation. A detailed analysis of the pairs of stars in the selected 5 systems to clarify their composition and the nature of the link between them was made. Positional data from the Hipparcos, Tycho2, UCAC4, Gaia DR2, and Pan-STARRS (PS1) catalogs were used as sources of additional information about the investigated stars. The search for possible invisible stars in the selected systems was performed using the statistical Wielen method, based on the analysis of the differences of instantaneous and long-term averaged proper motions of the stars. The proper motions of the space Gaia DR2 catalog were considered to be instantaneous, the long-term averaged proper motions were used from Tycho-2 and UCAC4 catalogs. Obtained values of the statistical parameter in some cases indicate a high probability of existence of invisible close components in the studied systems. Detailed comments of the results for each of the selected systems are provided.

The angle between the stellar spin-axis and the orbital plane of a stellar or planetary companion has important implications for the formation and evolution of such systems. A study by Hale (1994) found that binaries with separations $a < 30$ au are preferentially aligned while binaries on wider orbits are frequently misaligned. We aim to test the robustness of the Hale (1994) results by reanalysing the sample of visual binaries with measured rotation periods using independently derived stellar parameters and a Bayesian formalism. Our analysis is based on a combination of data from Hale (1994) and newly obtained spectroscopic data from the Hertzsprung SONG telescope, combined with astrometric data from Gaia DR2 and the Washington Double Star Catalog. We combine measurements of stellar radii and rotation periods to obtain stellar rotational velocities $v$. Rotational velocities $v$ are combined with measurements of projected rotational velocities $v\sin i$ to derive posterior probability distributions of stellar inclination angles $i$. We determine line-of-sight projected spin-orbit angles by comparing stellar inclination angles with astrometric orbital inclination angles. We find that the precision of the available data is insufficient to make inferences about the spin-orbit alignment of visual binaries. The data are equally compatible with alignment and misalignment at all orbital separations. We conclude that the previously reported trend that binaries with separations $a < 30$ au are preferentially aligned is spurious. The spin-orbit alignment distribution of visual binaries is unconstrained. Based on simulated observations, we predict that it will be difficult to reach the sufficient precision in $v\sin i$, rotation periods, and orbital inclination required to make robust statistical inferences about the spin-orbit alignment of visual binaries., Accepted for publication in A&A. 10 pages, 5 figures, 1 table

The star phi Dra comprises a spectroscopic binary and a third star that together form a visual triple system. It is one of the brightest chemically peculiar (CP) stars of the upper main sequence. Despite these facts, no comprehensive study of its multiplicity has been performed yet. In this work, we present a detailed analysis of the triple system based on available measurements. We use radial velocities taken from four sources in the literature in a re-analysis of the inner spectroscopic binary (Aab). An incorrect value of the orbital period of the inner system Aab about 27 days was accepted in literature more than forty years. A new solution of orbit with the 128-day period was determined. Relative position measurements of the outer visual binary system (AB) from Washington Double Star Catalog were compared with known orbital models. Furthermore, it was shown that astrometric motion in system AB is well described by the model of Andrade (2005) with a 308-year orbital period. Parameters of A and B components were utilized to estimate individual brightness for all components and their masses from evolutionary tracks. Although we found several facts which support the gravitational bond between them, unbound solution cannot be fully excluded yet.

In this paper, some statistical distributions of wide pairs included in Double Star Catalogue are investigated. Frequency distributions and testing hypothesis are derived for some basic parameters of visual binaries. The results reached indicate that, it was found that the magnitude difference is distributed exponentially, which means that the majority of the component of the selected systems is of the same spectral type. The distribution of the mass ratios is concentrated about 0.7 which agree with Salpeter mass function. The distribution of the linear separation appears to be exponentially, which contradict with previous studies for close binaries., 15 pages, 6 figures and 12 tables

We present an updated spectroscopic orbit and a new visual orbit for the double-lined spectroscopic binary \sigma^2 Coronae Borealis based on radial velocity measurements at the Oak Ridge Observatory in Harvard, Massachusetts and interferometric visibility measurements at the CHARA Array on Mount Wilson. \sigma^2 CrB is composed of two Sun-like stars of roughly equal mass in a circularized orbit with a period of 1.14 days. The long baselines of the CHARA Array have allowed us to resolve the visual orbit for this pair, the shortest period binary yet resolved interferometrically, enabling us to determine component masses of 1.137 \pm 0.037 M_sun and 1.090 \pm 0.036 M_sun. We have also estimated absolute V-band magnitudes of MV (primary) = 4.35 \pm 0.02 and MV(secondary) = 4.74 \pm 0.02. A comparison with stellar evolution models indicates a relatively young age of 1-3 Gyr, consistent with the high Li abundance measured previously. This pair is the central component of a quintuple system, along with another similar-mass star, \sigma^1 CrB, in a ~ 730-year visual orbit, and a distant M-dwarf binary, \sigma CrB C, at a projected separation of ~ 10 arcmin. We also present differential proper motion evidence to show that components C & D (ADS 9979C & D) listed for this system in the Washington Double Star Catalog are optical alignments that are not gravitationally bound to the \sigma CrB system., Comment: 40 pages, 14 figures. Accepted by ApJ

We thank Robert Wilson (University of Florida) for providing a custom version of his code to compute images of spotted stellar surfaces and for his help with using it. This work is based upon observations obtained with the Georgia State University (GSU) Center for High Angular Resolution Astronomy (CHARA) array at Mount Wilson Observatory. The CHARA array is supported by the National Science Foundation under grant numbers AST-1211929 and AST-1411654. Institutional support has been provided by the GSU College of Arts and Sciences and the GSU Office of the Vice President for Research and Economic Development. The MIRC instrument at the CHARA array was funded by the University of Michigan. F.B., R.R., and J.D.M. acknowledge support from NSF-AST 1210972 and 1108963. G.T. acknowledges partial support from NSF grant AST-1509375. S.K. acknowledges support from an STFC Rutherford Fellowship (ST/J004030/1) and ERC Starting Grant (grant agreement no. 639889). This work is also based on observations made with the Nordic Optical Telescope (NOT), operated by the Nordic Optical Telescope Scientific Association at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofisica de Canarias. This research has made use of the SIMBAD database, operated at the CDS, Strasbourg, France. This research has made use of the Jean-Marie Mariotti Center SearchCal service13 codeveloped by FIZEAU and LAOG/IPAG and of the CDS astronomical databases SIMBAD and VIZIER.14 This research has made use of the Washington Double Star Catalog, maintained at the U.S. Naval Observatory. We thank Nicholas Elias II for discussions. We thank Dimitri Pourbaix for maintaining and providing access to the SB9 database of RV measurements of spectroscopic binaries.

The Washington Double Star Catalog (WDS), maintained by the US Naval Observatory, is the world's principal database of astrometric double and multiple star information. The WDS contains positions (J2000), discoverer designations, epochs, position angles, separations, magnitudes, spectral types, proper motions, and, when available, Durchmusterung numbers and notes for the components of 84,486 systems based on 563,326 means. The current version, available on-line, is updated nightly. This catalog is one of four USNO double star catalogs to be included on a new CD-ROM. A brief summary and statistical analysis of the contents of the catalog are presented.

The Tycho-2 Catalogue provides astrometric and photometric information for 2.5 million stars. Within the Tycho-2 Catalogue, while there is no separate listing of double-star parameters, there is a wealth of double-star data. For all measured double-star systems, each component has its own entry in Tycho-2 (this corresponds to the Hipparcos ii double-entry systems ˇˇ), and the classical double-star parameters of separation, position angle, and magnitude diUerence can be calculated for these systems. Most double stars in the Tycho-2 Catalogue are identi—ed by a code indicating a double, failed double, or photo- centric solution. Stars —agged in this manner include 6251 known double stars and 1234 new double-star systems (designated in the Washington Double Star Catalog (WDS) with a ii TDS ˇˇ discovery code). Also, 4726 systems solved via Tycho-2 ii single-star treatment ˇˇ not only matched one component of a WDS pair but also had a nearby star that closely approximated the position and magnitude of the other WDS component. Finally, 1133 WDS systems were seen as single in Tycho-2 whose historical double- star parameters would indicate that Tycho-2 should have measured them. The observational statistics of these various classes of objects are presented together with catalog statistics for those with single-star solutions. A quantitative assessment of Tycho-2 double-star measures is provided via a comparison of Tycho-2 O(C residuals to known orbits. Finally, a subset of systems measured by Tycho-2 have been veri—ed via speckle interferometry using the 82 inch (2 m) telescope of McDonald Observatory. These results are presented here.

In the Guide Star Catalog (GSC) 223 new trapezia have been found. A new, more complete list of trapezia, including 637 objects, has been compiled on the basis of the GSC and the Washington Double Star Catalog.

LP 876-10 is a nearby active M4 dwarf in Aquarius at a distance of 7.6 pc. The star is a new addition to the 10-pc census, with a parallax measured via the Research Consortium on Nearby Stars (RECONS) astrometric survey on the Small & Moderate Aperture Research Telescope System's (SMARTS) 0.9-m telescope. We demonstrate that the astrometry, radial velocity, and photometric data for LP 876-10 are consistent with the star being a third, bound, stellar component to the Fomalhaut multiple system, despite the star lying nearly 6 degrees away from Fomalhaut A in the sky. The 3D separation of LP 876-10 from Fomalhaut is only 0.77+-0.01 pc, and 0.987+-0.006 pc from TW PsA (Fomalhaut B), well within the estimated tidal radius of the Fomalhaut system (1.9 pc). LP 876-10 shares the motion of Fomalhaut within ~1 km/s, and we estimate an interloper probability of ~10^{-5}. Neither our echelle spectroscopy nor astrometry are able to confirm the close companion to LP 876-10 reported in the Washington Double Star Catalog (WSI 138). We argue that the Castor Moving Group to which the Fomalhaut system purportedly belongs, is likely to be a dynamical stream, and hence membership to the group does not provide useful age constraints for group members. LP 876-10 (Fomalhaut C) has now risen from obscurity to become a rare example of a field M dwarf with well-constrained age (440+-40 Myr) and metallicity. Besides harboring a debris disk system and candidate planet, Fomalhaut now has two of the widest known stellar companions., 43 pages, 5 figures, AJ, in press, emulateapj version can be downloaded at: http://www.pas.rochester.edu/~emamajek/fomc/index.html

We present the results of a speckle interferometric survey of Galactic massive stars that complements and expands upon a similar survey made over a decade ago. The speckle observations were made with the KPNO and CTIO 4 m telescopes and USNO speckle camera, and they are sensitive to the detection of binaries in the angular separation regime between 0.03" and 5" with relatively bright companions (Delta V < 3). We report on the discovery of companions to 14 OB stars. In total we resolved companions of 41 of 385 O-stars (11%), 4 of 37 Wolf-Rayet stars (11%), and 89 of 139 B-stars (64%; an enriched visual binary sample that we selected for future orbital determinations). We made a statistical analysis of the binary frequency among the subsample that are listed in the Galactic O Star Catalog by compiling published data on other visual companions detected through adaptive optics studies and/or noted in the Washington Double Star Catalog and by collecting published information on radial velocities and spectroscopic binaries. We find that the binary frequency is much higher among O-stars in clusters and associations compared to the numbers for field and runaway O-stars, consistent with predictions for the ejection processes for runaway stars. We present a first orbit for the O-star Delta Orionis, a linear solution of the close, apparently optical, companion of the O-star Iota Orionis, and an improved orbit of the Be star Delta Scorpii. Finally, we list astrometric data for another 249 resolved and 221 unresolved targets that are lower mass stars that we observed for various other science programs., 76 pages, 6 figures, 11 tables

We present results of a reconnaissance for stellar companions to all 131 radial-velocity-detected candidate extrasolar planetary systems known as of July 1, 2005. CPM companions were investigated using the multi-epoch DSS images, and confirmed by matching the trigonometric parallax distances of the primaries to companion distances estimated photometrically. We also attempt to confirm or refute companions listed in the Washington Double Star Catalog, the Catalogs of Nearby Stars, in Hipparcos results, and in Duquennoy & Mayor (1991). Our findings indicate that a lower limit of 30 (23%) of the 131 exoplanet systems have stellar companions. We report new stellar companions to HD 38529 and HD 188015, and a new candidate companion to HD 169830. We confirm many previously reported stellar companions, including six stars in five systems that are recognized for the first time as companions to exoplanet hosts. We have found evidence that 20 entries in the Washington Double Star Catalog are not gravitationally bound companions. At least three, and possibly five, of the exoplanet systems reside in triple star systems. Three exoplanet systems have potentially close-in stellar companions ~ 20 AU away from the primary. Finally, two of the exoplanet systems contain white dwarf companions. This comprehensive assessment of exoplanet systems indicates that solar systems are found in a variety of stellar multiplicity environments - singles, binaries, and triples; and that planets survive the post-main-sequence evolution of companion stars., 52 pages, 7 figures, Accepted for publication in ApJ

In reviewing observations taken of binary stars used as calibration objects for non-astronomical purposes with adaptive optics on the 3.5 m Starfire Optical Range telescope over the past 2 years, one-fifth of them were found to be off-orbit. In order to understand such a high number of discrepant position angles and separations, all previous observations in the Washington Double Star Catalog for these rogue binaries were obtained from the Naval Observatory. Adding our observations to these yields new orbits for all, resolving the discrepancies. We have detected both components of γ Gem for the first time, and we have shown that 7 Cam is an optical pair, not physically bound.

The newly completed Fourth USNO CCD Astrographic Catalog (UCAC4) has proven to be a rich source of double star astrometry and photometry. Following initial comparisons of UCAC4 results against those obtained by speckle interferometry, the UCAC4 catalog was matched against known double stars in the Washington Double Star Catalog in order to provide additional differential astrometry and photometry for these pairs. Matches to 58,131 pairs yielded 61,895 astrometric and 68,935 photometric measurements. Finally, a search for possible new common proper motion (CPM) pairs was made using new UCAC4 proper motion data; this resulted in 4755 new potential CPM doubles (and an additional 27,718 astrometric and photometric measures from UCAC and other sources).

In this paper, we analyze seven components of system ADS 48. Its number in the Washington Double Star Catalog is 00057+4549. We use the measuring results from our CCD frames obtained between 1994 and 2011. Our aim is to establish which of these components are gravitationally bound, i.e., have an orbital motion around the mass center, and which of them are mutually very distant in space so that only their projections are close in the field of view. In addition to the measurements, we also apply different criteria based on celestial mechanics. Out of seven considered components, only the closest pair STT 547 AB is in orbital motion around the mass center. The other components, except that with the largest separation, are merely projected stars. The most distant component has common proper motion with pair AB.

Context. Massive stars have high-multiplicity fractions, and many of them have still undetected components, thus hampering the study of their properties. Aims. I study a sample of massive stars with high angular resolution to better characterize their multiplicity. Methods. I observed 138 fields that include at least one massive star with AstraLux, a lucky imaging camera at the 2.2 m Calar Alto telescope. I also used observations of 3 of those fields with ACS/HRC on HST to obtain complementary information and to calibrate the AstraLux data. The results were compared with existing information from the Washington Double Star Catalog, Tycho-2, 2MASS, and other literature results. Results. I discover 16 new optical companions of massive stars, the majority of which are likely to be physically bound to their primaries. I also improve the accuracy for the separation and magnitude difference of many previously known systems. In a few cases the orbital motion is detected when comparing the new data with existing ones and constraints on the orbits are provided. Conclusions. The analysis indicate that the majority of the AstraLux detections are bound pairs. For a range of separations of 0.

A major revision of the Washington Double Star (WDS) catalog containing data for the com- ponents of 78 100 systems is now available from the data centers and via the World Wide Web (http://aries.usno.navy.mil/ad/wds/).

We present interferometric observations of the sigma Orionis triple system using the CHARA Array, NPOI, and VLTI. Using these measurements, we spatially resolve the orbit of the close spectroscopic binary (Aa,Ab) for the first time and present a revised orbit for the wide pair (A,B). Combining the visual orbits with previously published radial velocity measurements and new radial velocities measured at CTIO, we derive dynamical masses for the three massive stars in the system of M_Aa = 16.99 +/- 0.20 Msun, M_Ab = 12.81 +/- 0.18 Msun, and M_B = 11.5 +/- 1.2 Msun. The inner and outer orbits in the triple are not coplanar, with a relative inclination of 120-127 deg. The orbital parallax provides a precise distance of 387.5 +/- 1.3 pc to the system. This is a significant improvement over previous estimates of the distance to the young sigma Orionis cluster., Accepted by the Astronomical Journal. 23 pages, 11 figures, 11 tables