Direct imaging is a powerful exoplanet discovery technique that is complementary to other techniques and offers great promise in the era of 30 meter class telescopes. Space-based transit surveys have revolutionized our understanding of the frequency of planets at small orbital radii around Sun-like stars. The next generation of extremely large ground-based telescopes will have the angular resolution and sensitivity to directly image planets with R < 4R ⊕ around the very nearest stars. Here, we predict yields from a direct imaging survey of a volume-limited sample of Sun-like stars with the Mid-Infrared ELT Imager and Spectrograph (METIS) instrument, planned for the 39 m European Southern Observatory (ESO) Extremely Large Telescope (ELT) that is expected to be operational towards the end of the decade. Using Kepler occurrence rates, a sample of stars with spectral types A-K within 6.5 pc, and simulated contrast curves based on an advanced model of what is achievable from coronagraphic imaging with adaptive optics, we estimated the expected yield from METIS using Monte Carlo simulations. We find the METIS expected yield of planets in the N2 band (10.10 -12.40 µm) is 1.14 planets, which is greater than comparable observations in the L (3.70 -3.95 µm) and M (4.70 -4.90 µm) bands. We also determined a 24.6% chance of detecting at least one Jovian planet in the background limited regime assuming a 1 hour integration. We calculated the yield per star and estimate optimal observing revisit times to increase the yield. We also analyzed a northern hemisphere version of this survey and found there are additional targets worth considering. In conclusion, we present an observing strategy aimed to maximize the possible yield for limited telescope time, resulting in 1.48 expected planets in the N2 band.

No abstract

&lt;p&gt;Direct imaging is a powerful exoplanet discovery technique that is complimentary to other techniques with great promise in the era of 30-meter class telescopes. Space-based transit surveys have revolutionized our understanding of the frequency of planets at small orbital radii around sun-like stars. The next generation of extremely large ground-based telescopes will have the angular resolution and sensitivity to directly image planets with R &lt; 4 Earth radii around the very nearest stars. Here we predict yields from a direct imaging survey of a volume-limited sample of sun-like stars with the Mid-Infrared ELT Imager and Spectrograph (METIS) instrument, planned for the 39-m European Southern Observatory (ESO) Extremely Large Telescope (ELT) that is expected to be operational towards the end of the decade. Using Kepler occurrence rates, a sample of stars with spectral types A-K within 6.5 pc, and simulated contrast curves based on an advanced model of what is achievable from coronagraphic imaging with adaptive optics, we estimate the expected yield from METIS using Monte Carlo simulations. We find the METIS expected yield of small planets in the N2 band (10.10 - 12.40 &amp;#956;m) is 1.15 planets which is greater than similar observations in the L (3.70 - 3.95 &amp;#956;m) and M (4.70 - 4.90 &amp;#956;m) bands. We also determine a 42% chance of detecting at least one Jovian planet in the background limited regime assuming a 1-hour integration. We calculate the yield per star and estimate optimal observing revisit times to increase the yield. We also analyze this survey if performed in the northern hemisphere and find there are additional targets worth considering. Finally, we present an observing strategy in order to maximize the possible yield for limited telescope time, resulting in 1.52 expected planets in the N2 band.&lt;/p&gt;

New mid‐infrared HgCdTe (MCT) detector arrays developed in collaboration with Teledyne Imaging Sensors (TIS) have paved the way for improved 10‐m sensors for space‐ and ground‐based observatories. Building on the successful development of longwave HAWAII‐2RGs for space missions such as NEO Surveyor, we characterize the first 13‐m GeoSnap detector manufactured to overcome the challenges of high‐background rates inherent in ground‐based mid‐IR astronomy. This test device merges the longwave HgCdTe photosensitive material with Teledyne's GeoSnap‐18 (18‐m pixel) focal plane module, which is equipped with a capacitive transimpedance amplifier (CTIA) readout circuit paired with an onboard 14‐bit analog‐to‐digital converter (ADC). The final assembly yields a mid‐IR detector with high QE, fast readout (>85 Hz), large well depth (>1.2 million electrons), and linear readout. Longwave GeoSnap arrays would ideally be deployed on existing ground‐based telescopes as well as the next generation of extremely large telescopes. While employing advanced adaptive optics (AO) along with state‐of‐the‐art diffraction suppression techniques, instruments utilizing these detectors could attain background‐ and diffraction‐limited imaging at inner working angles <10 /D, providing improved contrast‐limited performance compared with JWST MIRI while operating at comparable wavelengths. We describe the performance characteristics of the 13‐m GeoSnap array operating between 38 45 K, including quantum efficiency, well depth, linearity, gain, dark current, and frequency‐dependent () noise profile.

We introduce the Michigan Infrared Test Thermal ELT N-band (MITTEN) Cryostat, a new facility for testing infrared detectors with a focus on mid-infrared (MIR) wavelengths (8-13 microns). New generations of large format, deep well, fast readout MIR detectors are now becoming available to the astronomical community. As one example, Teledyne Imaging Sensors (TIS) has introduced a long-wave Mercury-Cadmium-Telluride (MCT) array, GeoSnap, with high quantum efficiency (> 65 %) and improved noise properties compared to previous generation Si:As blocked impurity band (BIB) detectors. GeoSnap promises improved sensitivities, and efficiencies, for future background-limited MIR instruments, in particular with future extremely large telescopes (ELTs). We describe our new test facility suitable for measuring characteristics of these detectors, such as read noise, dark current, linearity, gain, pixel operability, quantum efficiency, and point source imaging performance relative to a background scene, as well as multiple point sources of differing contrast. MITTEN has an internal light source, and soon an accompanying filter wheel and aperture plate, reimaged onto the detector using an Offner relay. The baseline temperature of the cryostat interior is maintained < 40 K and the optical bench maintains a temperature of 16 K using a two-stage pulse-tube cryocooler package from Cryomech. No measurable background radiation from the cryostat interior has yet been detected.

Transitional disks are protoplanetary disks with large and deep central holes in the gas, possibly carved by young planets. Dong, R., & Dawson, R. 2016, ApJ, 825, 7 simulated systems with multiple giant planets that were capable of carving and maintaining such gaps during the disk stage. Here we continue their simulations by evolving the systems for 10 Gyr after disk dissipation and compare the resulting system architecture to observed giant planet properties, such as their orbital eccentricities and resonances. We find that the simulated systems contain a disproportionately large number of circular orbits compared to observed giant exoplanets. Large eccentricities are generated in simulated systems that go unstable, but too few of our systems go unstable, likely due to our demand that they remain stable during the gas disk stage to maintain cavities. We also explore whether transitional disk inspired initial conditions can account for the observed younger ages of 2:1 resonant systems orbiting mature host stars. Many simulated planet pairs lock into a 2:1 resonance during the gas disk stage, but those that are disrupted tend to be disrupted early, within the first 10 Myr. Our results suggest that systems of giant planets capable of carving and maintaining transitional disks are not the direct predecessors of observed giant planets, either because the transitional disk cavities have a different origin or another process is involved, such as convergent migration that pack planets close together at the end of the transitional disk stage.

No abstract

No abstract