Mining Planet Search Data for Binary Stars: The ${\psi }^1$ Draconis system

Abstract

Several planet-search groups have acquired a great deal of data in the form of time-series spectra of several hundred nearby stars with time baselines of over a decade. While binary star detections are generally not the goal of these long-term monitoring efforts, the binary stars hiding in existing planet search data are precisely the type that are too close to the primary star to detect with imaging or interferometry techniques. We use a cross-correlation analysis to detect the spectral lines of a new low-mass companion to ${\psi }^1$ Draconis A, which has a known roughly equal-mass companion at $\sim 680$ AU. We measure the mass of ${\psi }^1$ Draconis C as $M_2=0.70\pm 0.07M_{\odot }$, with an orbital period of $\sim 20$ years. This technique could be used to characterize binary companions to many stars that show large-amplitude modulation or linear trends in radial velocity data.

arXiv comment5 pages, 3 figures, 2 tables. To appear in the Astrophysical Journal. Supplementary material and python code used available at https://github.com/kgullikson88/Companion-Finder

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• An Early Catalog of Planet Hosting Multiple Star Systems of Order Three and Higher
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