Stellar statistics along the ecliptic and the impact on the K2 mission concept

Abstract

K2 is the mission concept for a repurposed Kepler mission that uses two reaction wheels to maintain the satellite attitude and provide ∼85 days of coverage for ten 105-deg 2 fields along the ecliptic in the first 2.5 years of operation. We examine stellar populations based on the improved Besançon model of the Galaxy, comment on the general properties for the entire ecliptic plane, and provide stellar occurrence rates in the first 6 tentative K2 campaigns grouped by spectral type and luminosity class. For each campaign we distinguish between main sequence stars and giants and provide their density profile as a function of galactic latitude. We introduce the crowding metric that serves for optimized target selection across the campaigns. For all main sequence stars we compute the expected planetary occurrence rates for three planet sizes: 2-4 R ⊕ , 4-8 R ⊕ , and 8-32 R ⊕ with orbital periods up to 50 days. In conjunction with Gaia and the upcoming TESS and Plato missions, K2 will become a gold mine for stellar and planetary astrophysics.

Kepler Eclipsing Binary Stars. Vii. The Catalog of Eclipsing Binaries Found in the Entire Kepler Data Set

“…These values are only approximate measures and are only as accurate as the polyfits themselves. Nevertheless, they do provide some measure of the signal-to-noise and also allow for an estimate of eccentricities (Prša et al 2015).…”

“…Galaxy population observations and models, however, have long predicted this behavior: the stellar population at lower galactic latitudes (thin disk) contains notably younger stars that are on average larger (i.e. contain more giants in the magnitude-limited sample) than the older, sparser population of the thick disk and halo (Prša et al 2015). In consequence, the geometric probability of eclipses increases towards the galactic disk.…”

Kepler Eclipsing Binary Stars. V. Identification of 31 Candidate Eclipsing Binaries in the K2 Engineering Dataset

“…5), as described in Prša et al (2011). This analytic function is then used to determine the morphology, a value between zero (detached) and one (overcontact), using locally linear embedding (Matijevič et al 2012).…”

“…The Kepler satellite (Batalha et al 2010) observed over 150,000 stars in its original mission, which acquired over 4 yr of high-precision photometry. This dataset was followed by a large effort to study the eclipsing binary (EB) population in the Kepler field, resulting in the detection and characterization of over 2500 EB stars (Prša et al 2011;Slawson et al 2011), the measurements of eclipse timing variations (Conroy et al 2014), and the discovery of several circumbinary planets (Doyle et al 2011;Welsh et al 2012).…”

“…Now that Kepler has transitioned to its repurposed mission, K2, it is providing 80 days of continuous high-precision photometry across each of 10 fields in the ecliptic plane, once again giving great scientific opportunity to identify and characterize EBs (Prša et al 2014). Although the photometric precision compared to the original Kepler mission is expected to be slightly lower due to a decrease in pointing accuracy, K2 is still expected to obtain data an order of magnitude better than is possible from the ground.…”