A Super-Jupiter Microlens Planet

A Super-Jupiter Microlens Planet Characterized by High-Cadence KMTNet Microlensing Survey Observations

Authors:

Shin et al

Abstract:

We report the characterization of a massive planet m_p=4.4 +- 1.6 M_jup orbiting an M dwarf host M=0.37 +- 0.14 M_sun at a distance of 0.6 +- 0.3 kpc toward the Galactic bulge, with planet host projected separation a_perp ~ 1.2 AU. The characterization was made possible by the wide-field (4 deg^2) high cadence (6/hr) monitoring of the Korea Microlensing Telescope Network (KMTNet), which had two of its three telescopes in commissioning operations at the time of the planetary anomaly. The source crossing time, t_* ~ 16 min, is among the shortest ever published. The high-cadence, wide-field observations that are the hallmark of KMTNet are the only way to routinely capture such short crossings. High-cadence resolution of short caustic crossings will preferentially lead to mass and distance measurements for the lens. This is because the short crossing time typically implies a nearby lens, which enables the measurement of additional effects (bright lens and/or microlens parallax). When combined with the measured crossing time, these effects can yield complete solutions.

KMT-2015-1b: a 2 Jupiter Mass Exoplanet Orbiting a M Dwarf Beyond the Snowline

KMT-2015-1b: a Giant Planet Orbiting a Low-mass Dwarf Host Star Discovered by a New High-cadence Microlensing Survey with a Global Telescope Network

Authors:

Hwang et al

Abstract:

We report the discovery of an extrasolar planet, KMT-2015-1b, that was detected using the microlensing technique. The planetary lensing event was observed by KMTNet survey that has commenced in 2015. With dense coverage by using network of globally distributed telescopes equipped with very wide-field cameras, the short planetary signal is clearly detected and precisely characterized. We find that KMT-2015-1b is a giant planet orbiting a low-mass M-dwarf host star. The planet has a mass about twice that of Jupiter and it is located beyond the snow line of the host star. With the improvement of existing surveys and the advent of new surveys, future microlensing planet samples will include planets not only in greatly increased number but also in a wide spectrum of hosts and planets, helping us to have a better and comprehensive understanding about the formation and evolution of planets.

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⊙.

Korean Microlensing Telescope Network's Potential

Optimal Survey Strategies and Predicted Planet Yields for the Korean Microlensing Telescope Network

Authors:

Henderson et al

Abstract:

The Korean Microlensing Telescope Network (KMTNet) will consist of three 1.6m telescopes each with a 4 deg^{2} field of view (FoV) and will be dedicated to monitoring the Galactic Bulge to detect exoplanets via gravitational microlensing. KMTNet's combination of aperture size, FoV, cadence, and longitudinal coverage will provide a unique opportunity to probe exoplanet demographics in an unbiased way. Here we present simulations that optimize the observing strategy for, and predict the planetary yields of, KMTNet. We find preferences for four target fields located in the central Bulge and an exposure time of t_{exp} = 120s, leading to the detection of ~2,200 microlensing events per year. We estimate the planet detection rates for planets with mass and separation across the ranges 0.1 less than or equal to M_{p}/M_{Earth} less than or equal to 1000 and 0.4 less than or equal to a/AU less than or equal to 16, respectively. Normalizing these rates to the cool-planet mass function of Cassan (2012), we predict KMTNet will be approximately uniformly sensitive to planets with mass 5 less than or equal to M_{p}/M_{Earth} less than or equal to 1000 and will detect ~20 planets per year per dex in mass across that range. For lower-mass planets with mass 0.1 less than or equal to M_{p}/M_{Earth} less than 5, we predict KMTNet will detect ~10 planets per year. We also compute the yields KMTNet will obtain for free-floating planets (FFPs) and predict KMTNet will detect ~1 Earth-mass FFP per year, assuming an underlying population of one such planet per star in the Galaxy. Lastly, we investigate the dependence of these detection rates on the number of observatories, the photometric precision limit, and optimistic assumptions regarding seeing, throughput, and flux measurement uncertainties.