A SURVEY OF THE HIGH ORDER MULTIPLICITY OF NEARBY SOLAR-TYPE BINARY STARS WITH Robo-AO

Abstract

We conducted a survey of nearby binary systems composed of main sequence stars of spectral types F and G in order to improve our understanding of the hierarchical nature of multiple star systems. Using Robo-AO, the first robotic adaptive optics instrument, we collected high angular resolution images with deep and well-defined detection limits in the SDSS i band. A total of 695 components belonging to 595 systems were observed. We prioritized observations of faint secondary components with separations over 10 to quantify the still poorly constrained frequency of their sub-systems. Of the 214 secondaries observed, 39 contain such subsystems; 19 of those were discovered with Robo-AO. The selection-corrected frequency of secondary sub-systems with periods from 10 3.5 to 10 5 days is 0.12±0.03, the same as the frequency of such companions to the primary. Half of the secondary pairs belong to quadruple systems where the primary is also a close pair, showing that the presence of subsystems in both components of the outer binary is correlated. The relatively large abundance of 2+2 quadruple systems is a new finding, and will require more exploration of the formation mechanism of multiple star systems. We also targeted close binaries with periods less than 100 yr, searching for their distant tertiary components, and discovered 17 certain and 2 potential new triples. In a subsample of 241 close binaries, 71 have additional outer companions. The overall frequency of tertiary components is not enhanced, compared to all (non-binary) targets, but in the range of outer periods from 10 6 to 10 7.5 days (separations on the order of 500 AU), the frequency of tertiary components is 0.16±0.03, exceeding by almost a factor of two the frequency of similar systems among all targets (0.09). Measurements of binary stars with Robo-AO allowed us to compute first orbits for 9 pairs and to improve orbits of another 11 pairs.

Relative Orbit Orientation in Several Resolved Multiple Systems

“…The available RVs now cover 1.5 outer periods and lead to the spectroscopic orbits of both inner and outer subsystems. The 19 year outer period found from the RVs matches well the visual orbit that covers almost the full ellipse; the preliminary 21 year orbit of A,B was published by Riddle et al (2015). The pair A,B was observed at SOAR several times, but the inner subsystem has never been resolved.…”

Stellar Companions to the Exoplanet Host Stars Hd 2638 and Hd 164509

“…Prior to submitting this work, we learned that Riddle et al (2015) have detected HD2638ʼs stellar companion. We present our results as an independent detection of this companion.…”

Observations of Binary Stars With the Differential Speckle Survey Instrument. Vi. Measures During 2014 at the Discovery Channel Telescope

“…The structure and physical parameters of binary and multiple stars are informative from a statistical point of view regarding star formation theories, as shown most recently in papers such as Raghavan et al (2010), Tokovinin (2014aTokovinin ( , 2014b, and Riddle et al (2015). In addition, it has been realized in the last couple of years that a significant number of stars that host exoplanet systems also have a stellar companion (e.g., Horch et al 2014;Kane et al 2014;Lillo-Box et al 2014), although there is evidence that the presence of stellar secondaries is suppressed relative to the field at smaller separations (Wang et al 2014a(Wang et al , 2014b.…”