Characterizing Host Stars to be Surveyed by the Korean Microlensing Telescope Network

Prospects for Characterizing Host Stars of the Planetary System Detections Predicted for the Korean Microlensing Telescope Network

Author:

Henderson

Abstract:

I investigate the possibility of constraining the flux of the lens (i.e., host star) for the types of planetary systems the Korean Microlensing Telescope Network is predicted to find. I examine the potential to obtain lens flux measurements by 1) imaging a lens once it is spatially resolved from the source, 2) measuring the elongation of the point spread function of the microlensing target (lens+source) when the lens and source are still unresolved, and 3) taking prompt follow-up photometry. In each case I simulate observing programs for a representative example of current ground-based adaptive optics (AO) facilities (specifically NACO on VLT), future ground-based AO facilities (GMTIFS on GMT), and future space telescopes (NIRCAM on JWST). Given the predicted distribution of relative lens-source proper motions, I find that the lens flux could be measured to a precision of σHℓ≤0.1 for ≳60% of planet detections ≥5 years after each microlensing event, for a simulated observing program using GMT that images resolved lenses. NIRCAM on JWST would be able to carry out equivalently high-precision measurements for ∼28% of events Δt = 10 years after each event by imaging resolved lenses. I also explore the effects various blend components would have on the mass derived from prompt follow-up photometry, including companions to the lens, companions to the source, and unassociated interloping stars. I find that undetected blend stars would cause catastrophic failures (i.e., greater than 50% fractional uncertainty in the inferred lens mass) for ≲(16⋅fbin)% of planet detections, where fbin is the binary fraction, with the majority of these failures occurring for host stars with mass ≲0.3M⊙.