Radio Interferometric Planet Search I: First Constraints on Planetary Companions for Nearby, Low-Mass Stars from Radio Astrometry

TL;DR

This study uses radio astrometry to observe nearby low-mass stars, setting new constraints on the presence of planetary companions, and demonstrating the potential of radio techniques for exoplanet detection around M dwarfs.

Contribution

First application of radio astrometry to constrain planetary companions around nearby low-mass stars, providing upper mass limits at specific orbital distances.

Findings

Detected radio emission from 29 out of 172 stars.

Achieved milliarcsecond astrometric precision with VLBA.

Excluded planetary companions more massive than 3-6 M_Jup at ~1 AU.

Abstract

Radio astrometry of nearby, low-mass stars has the potential to be a powerful tool for the discovery and characterization of planetary companions. We present a Very Large Array survey of 172 active M dwarfs at distances of less than 10 pc. Twenty nine stars were detected with flux densities greater than 100 microJy. We observed 7 of these stars with the Very Long Baseline Array at milliarcsecond resolution in three separate epochs. With a detection threshold of 500 microJy in images of sensitivity 1 sigma ~ 100 microJy, we detected three stars three times (GJ 65B, GJ896A, GJ 4247), one star twice (GJ 285), and one star once (GJ 803). Two stars were undetected (GJ 412B and GJ 1224). For the four stars detected in multiple epochs, residuals from the optically-determined proper motions have an rms deviation of ~0.2 milliarcseconds, consistent with statistical noise limits. Combined with previous optical astrometry, these residuals provide acceleration upper limits that allow us to exclude planetary companions more massive than 3-6 M_Jup at a distance of ~1 AU with a 99% confidence level.