Abstract - The SUPERWIDE catalog is an all-sky catalog of ∼90,000 wide binaries with projected orbital separations ∼100 to 100,000 AU, mostly located within 500 pc of the Sun. These consist of common proper motion (CPM) pairs of high proper motion stars (>40 mas/yr). A Bayesian analysis using positions, proper motions and distances from Gaia Data Release 2 (DR2) shows these pairs to have probabilities >99% of being gravitationally bound systems. Here, we examine K+K wide binaries, which allow for easy identification of unresolved higher-order systems because the K dwarf main sequence is narrow and unresolved subsystems are easily identified as over-luminous. We found 980 systems where at least one of the wide components is over-luminous, which means they are higher-order systems (triples and quadruples). Although metallicity efffects generally complicate the identification of over-luminous stars, we show that this can be easily accounted for in wide binaries, making the identification of unresolved subsystems relatively straightforward. Taking these effects into account, we calculate the higher-order multiplicity fraction to be 39.6%.
Talks and presentations
Abstract - We present the results of our search for wide binaries in the SUPERBLINK high proper motion catalog of 2.8 million stars with proper motions >40 mas/yr, which has been recently enhanced with data from the GAIA mission. In a first step, we conduct a Bayesian analysis taking into account angular separations and proper motion differences provided by the SUPERBLINK catalog, and identify all possible common proper motion (CPM) pairs with separations up to 60 arcminutes. In the second step we expand the analysis using parallaxes from the Gaia DR2 release, and calculate probabilities for each pair to be a gravitationally bound system. The result is a list of 18,000 pairs with probabilities of being real binaries greater than 99 percent. We show that the distribution of projected physical separations of these wide, field binaries follows a decreasing power law, and shows no evidence of being bimodal, i.e. there is no evidence of a secondary population of pairs with separations >10(4) AU. In addition, we find clear evidence that at least 30 percent of these wide binaries are triples/multiples, based on one of the components being over-luminous.
The Tale of the Lobster: Over-luminous Stars in Wide Binaries and a Search for Higher Order Multiples
Abstract - We present a search for higher-order multiples (triples, quadruples, etc.) among K+K and K+M wide binaries identified in the SUPERWIDE all-sky catalog of wide binaries. The SUPERWIDE catalog was assembled from a Bayesian analysis of the high proper motion (> 40 mas/yr) stars in Gaia Data Release 2 (DR2) using their positions, proper motions, and parallaxes. Examining the color-magnitude diagram of the primary and secondary components clearly shows a doubling of the main sequence in the K and early-M dwarf regime, consistent with a normal single star main sequence plus an over-luminous sequence due to some of the components being unresolved binaries. To better identify the over-luminous stars in our wide binaries, we define an over-luminosity factor, which measures the difference between the absolute magnitude of a star and a reference line which runs parallel to the main sequence in the K dwarf region. A “lobster” diagram is then created, which plots the over-luminosity factor of the primary as a function of the over-luminosity factor of the secondary. An examination of this plot reveals that for K+K wide binaries, the higher order multiplicity of the selected sample is at least ~40%. We expand this technique to the lower mass regime (mid-M to late-M) by matching subsets of K+M pairs to the apogee catalog, and by assuming the metallicity of the low-mass secondaries is the same as that of the higher mass primaries. Using the resulting metallicity “tracks”, we determine the shape of the main sequence in the M dwarf regime, which allows us to define a proper reference and identify over-luminous components in the M dwarf range as well. To test if our over-luminous components are caused by binarity rather than other potential sources, we crossmatch our sample with TESS, K2 and Kepler to identify eclipsing systems among the over-luminous components and take speckle imaging results from previous observations and the POKEMON survey.
The SUPERWIDE Catalog of Wide Binaries and an Initial Look at the Higher Order Multiplicity of K and M dwarf Wide Binaries
Abstract - We present the SUPERWIDE catalog of wide binaries that were identified through a Bayesian analysis of high proper motions stars (m>40 mas/yr) from the Gaia DR2 catalog. Initially identified through an earlier search of the SUPERBLINK high proper motion catalog, these binaries were found by their proximity on the sky, common proper motion and similar distances. Taking those pairs with a probability of being a “true” binary (i.e. gravitationally bound system) greater than 99%, we identify ~22,000 wide binaries with projected physical separations between ~100 AU to ~1 pc. We present initial results of an ongoing speckle survey of these wide binaries devoted to the identification of higher order multiples. Using data collected through the POKEMON M-dwarf multiplicity survey, we have examined ~15 wide binaries to see if they are in fact triple or quadruple systems. With this information and more to come, we intend to determine the higher order multiplicity fraction for K and M dwarf wide binaries as a function of their physical separation in order to provide constraints for the possible formation mechanisms of these wide systems.
Abstract - We present results from our search for wide binaries in the SUPERBLINK+GAIA all-sky catalog of 2.8 million high proper motion stars (μ>40 mas/yr). Through a Bayesian analysis of common proper motion pairs, we have identified highly probable wide binary/multiple systems based on statistics of their proper motion differences and angular separations. Using a reduced proper motion diagram, we determine whether these wide are part of the young disk, old disk, or Galactic halo population. We examine the relative occurrence rate for very wide companions in these respective populations. All groups are found to contain a significant number of wide binary systems, with about 1 percent of the stars in each group having pairs with separations >1,000 AU.
Abstract - We present initial results from an all-sky search for Common Proper Motion (CPM) binaries in the SUPERBLINK all-sky proper motion catalog of 2.8 million stars with proper motions greater than 40 mas/yr, which has been recently enhanced with data from the GAIA mission. We initially search the SUPERBLINK catalog for pairs of stars with angular separations up to 1 degree and proper motion difference less than 40 mas/yr. In order to determine which of these pairs are real binaries, we develop a Bayesian analysis to calculate probabilities of true companionship based on a combination of proper motion magnitude, angular separation, and proper motion differences. The analysis reveals that the SUPERBLINK catalog most likely contains ~40,000 genuine common proper motion binaries. We provide initial estimates of the distances and projected physical separations of these wide binaries.
Abstract - We report eclipse timings and optical/infrared photometry of a sample of binary stars that include low-mass nondegenerate stars, some of which are post-common envelope (PCE) secondary companions to hot subdwarf B (sdB) stars. We model the reflection effect in the latter systems to characterize the temperature of the heated hemisphere of the secondaries, first from blackbody fits and then by comparison to libraries of the spectral energy distribution of dwarf M stars. We explore how consistent our phenomenological results are with the properties inferred from analysis of light curve shapes, and discuss the prospects for turning these reflection effect systems into double-lined spectroscopic binaries for characterization of the mass-radius relationship of low-mass PCE secondaries.