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A Tale of Nearly 100,000 Wide Binaries as Told by a Lobster, Two Spacecraft and Some Speckles

Presentation #438.03D in the session “Stellar Binaries 2”.

Published onJan 11, 2021
A Tale of Nearly 100,000 Wide Binaries as Told by a Lobster, Two Spacecraft and Some Speckles

Astronomers still do not know how the widest systems with separations larger than 10,000 au form. And yet, these systems have proved invaluable for calibrating metallicity relations and studying Galactic tides. One possible way to gain insight into their formation history is to examine the higher order multiplicity fraction, i.e. how many triples, quadruples, etc. To study this, we present a catalog of 99,203 wide binaries with probabilities greater than 95% of being gravitationally bound pairs. These binaries were identified through a Bayesian analysis of the high proper motion stars (> 40 mas/yr) in the Gaia DR2 catalog, along with supplemental stars from the SUPERBLINK high proper motion survey. Taking advantage of the linearity of the slope of the color-magnitude relationship of the K dwarf main sequence stars, we represent the relative over-luminosity of the components in K+K wide binaries in a plot we call the “Lobster” diagram. This diagram allows us to identify over-luminous components that most likely contain companions unresolved by Gaia DR2. Using this, we place a lower limit on the higher order multiplicity fraction of K+K wide binaries at 39.6%. To further prove that the “lobster” diagram highlights higher order multiples, we use the Lightkurve package in Python to identify eclipsing binary systems in TESS, K2 and Kepler and see where they fall on the diagram. Of the 12 eclipsing binaries identified, 11 were predicted to host an over-luminous component. In addition, we show that the presence of a spot modulation or unperiodic signal in a light curve suggests that system is more likely to show an over-luminous component. Finally, we present the first results of a speckle follow-up campaign examining the widest K+K systems (> 10,000 au) making use of the QWSSI speckle camera for the first time, a new instrument that we built at Lowell Observatory.

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