Discoveries of Stars, Brown Dwarfs, and Planets Orbiting K Dwarfs within 33 Parsecs

I present results of a survey to map planetary, sub-stellar, and stellar companions orbiting K dwarf systems in the solar neighborhood. Since 2017, we have been searching for companions within 3 AU of a volume-limited sample of 472 K dwarfs within 33 parsecs that are found in an equatorial region between DEC +30d and -30d. We have obtained multi-epoch radial velocities (RVs) using high resolution spectra obtained with the CHIRON spectrograph at the SMARTS 1.5m telescope at CTIO. Each K dwarf has been observed at least nine times in a cadence that samples three timescales — over a week, a month, and a year. The observing campaign has covered 100 percent the systems within 25 parsecs, and 80 percent within 33 parsecs, each with time baseline coverage of at least a year. To date, we have (a) found 4 new giant planet candidates, (b) confirmed 27 sub-stellar/stellar companions, (c) revealed 30 sub-stellar/stellar companion candidates, and (d) found 184 K Dwarfs that have no RV variations down to limits of 10-20 m/sec. These single K dwarfs are key targets to be targeted for terrestrial planets. Combined with known companions reported in the literature, we estimate that 49 percent of the K dwarf primaries have one or more stellar companions. Through this work, we have developed scheduling, observing, and data reduction tools that in combination prove that CHIRON and the SMARTS 1.5m form a stable, reliable, facility for companion discovery that is capable of detecting jupiter-mass companions with orbital periods up to 1000 days. We are living in an exciting era of exoplanet discoveries and new habitable worlds, and our work provides key knowledge about the orbital architectures critical to the exploration of the nearest stars for other solar systems. Our comprehensive approach — all stars are targeted, not just those that are presumed to be single — allows us to provide statistical results that reveal the outcomes to star and planet formation processes as never before. This effort has been supported by the NSF through grants AST-1517413 and AST-1910130 via observations made possible by the SMARTS Consortium.