Campaign 9 of the $K2$ Mission: Observational Parameters, Scientific Drivers, and Community Involvement for a Simultaneous Space- and Ground-based Microlensing Survey

TL;DR

K2 Campaign 9 is a combined space and ground-based microlensing survey aiming to measure microlens parallax for over 127 events, including potential free-floating planets, to better understand their frequency and distribution in the galaxy.

Contribution

This paper details the observational setup, scientific goals, and community involvement strategies for the first large-scale simultaneous space-ground microlensing survey with K2, paving the way for future missions like WFIRST.

Findings

Measurement of microlens parallax for over 127 events.

Potential detection of free-floating planets.

Insights into the distribution of exoplanets in the galaxy.

Abstract

$K2$'s Campaign 9 ($K2$C9) will conduct a $\sim$3.7 deg$^{2}$ survey toward the Galactic bulge from 7/April through 1/July of 2016 that will leverage the spatial separation between $K2$ and the Earth to facilitate measurement of the microlens parallax $\pi_{\rm E}$ for $\gtrsim$127 microlensing events. These will include several that are planetary in nature as well as many short-timescale microlensing events, which are potentially indicative of free-floating planets (FFPs). These satellite parallax measurements will in turn allow for the direct measurement of the masses of and distances to the lensing systems. In this white paper we provide an overview of the $K2$C9 space- and ground-based microlensing survey. Specifically, we detail the demographic questions that can be addressed by this program, including the frequency of FFPs and the Galactic distribution of exoplanets, the observational parameters of $K2$C9, and the array of resources dedicated to concurrent observations. Finally, we outline the avenues through which the larger community can become involved, and generally encourage participation in $K2$C9, which constitutes an important pathfinding mission and community exercise in anticipation of $WFIRST$.