We present revised stellar properties for 172 K2 target stars that were identified as possible hosts of transiting planets during Campaigns 1–17 .
Using medium-resolution near-infrared spectra acquired with the NASA Infrared Telescope Facility/SpeX and Palomar/TripleSpec , we found that 86 of our targets were bona fide cool dwarfs , 74 were hotter dwarfs , and 12 were giants .
Combining our spectroscopic metallicities with Gaia parallaxes and archival photometry , we derived photometric stellar parameters and compared them to our spectroscopic estimates .
Although our spectroscopic and photometric radius and temperature estimates are consistent , our photometric mass estimates are systematically \Delta M _ { \star } = 0.11 { M _ { \odot } } ( 34 % ) higher than our spectroscopic mass estimates for the least massive stars ( M _ { \star,phot } < 0.4 { M _ { \odot } } ) .
Adopting the photometric parameters and comparing our results to parameters reported in the Ecliptic Plane Input Catalog , our revised stellar radii are \Delta R _ { \star } = 0.15 { R _ { \odot } } ( 40 \% ) larger and our revised stellar effective temperatures are roughly \Delta T _ { eff } = 65 K cooler .
Correctly determining the properties of K2 target stars is essential for characterizing any associated planet candidates , estimating the planet search sensitivity , and calculating planet occurrence rates .
Even though Gaia parallaxes have increased the power of photometric surveys , spectroscopic characterization remains essential for determining stellar metallicities and investigating correlations between stellar metallicity and planetary properties .