Keck and Hubble Observations Show That MOA-2008-BLG-379Lb Is a Super-Jupiter Orbiting an M Dwarf

TL;DR

High-resolution imaging with Keck and Hubble reveals detailed properties of the MOA-2008-BLG-379Lb exoplanet system, including host star and planet masses, distance, and separation, enhancing microlensing analysis methods and future survey accuracy.

Contribution

The paper introduces an image constrained modeling code that improves efficiency and discusses the importance of including higher order effects in microlensing analysis.

Findings

Host star mass: 0.434±0.065 M_sun

Planet mass: 2.44±0.49 M_Jupiter

Distance: 3.44±0.53 kpc

Abstract

We present high angular resolution imaging that detects the MOA-2008-BLG-379L exoplanet host star using Keck adaptive optics and the Hubble Space Telescope. These observations reveal host star and planet masses of $M_{\rm host}=0.434\pm0.065 M_\odot$, and $m_p=2.44 \pm 0.49 M_{\rm Jupiter}$. They are located at a distance of $D_L=3.44\pm0.53\,$kpc, with a projected separation of $2.70\pm 0.42\,$AU. These results contribute to our determination of exoplanet host star masses for the Suzuki et al. (2016) statistical sample, which will determine the dependence of the planet occurrence rate on the mass and distance of the host stars. We also present a detailed discussion of the image constrained modeling version of the eesunhong light curve modeling code that applies high angular resolution image constraints to the light curve modeling process. This code increases modeling efficiency by a large factor by excluding models that are inconsistent with the high angular resolution images. The analysis of this and other events from the Suzuki et al. (2016) statistical sample reveals the importance of including higher order effects, such as microlensing parallax and planetary orbital motion even when these features are not required to fit the light curve data. The inclusion of these effects may be needed to obtain accurate estimates of the uncertainty of other microlensing parameters that affect the inferred properties of exoplanet microlens systems. This will be important for the exoplanet microlensing survey of the Roman Space Telescope, which will use both light curve photometry and high angular resolution imaging to characterize planetary microlens systems.