Using High-resolution Optical Spectra to Measure Intrinsic Properties of Low-mass Stars: New Properties for KOI-314 and GJ 3470

We construct high signal-to-noise "template" spectra by co-adding hundreds of spectra of nearby dwarfs spanning K7 to M4, taken with Keck/HIRES as part of the California Planet Search. We identify several spectral regions in the visible (370-800 nm) that are sensitive to the stellar luminosity and metallicity. We use these regions to develop a spectral calibration method to measure the mass, metallicity, and distance of low-mass stars, without the requirement of geometric parallaxes. Testing our method on a sample of nearby M dwarfs, we show that we can reproduce stellar masses to about 8%-10%, metallicity to ~0.15 dex, and distance to 11%. We were able to make use of HIRES spectra obtained as part of the radial velocity monitoring of the star KOI-314 to derive a new mass estimate of 0.57 ± 0.05 M_☉, a radius of 0.54 ± 0.05 R_☉, a metallicity, [Fe/H], of –0.28 ± 0.10, and a distance of 66.5 ± 7.3 pc. Using HARPS archival data and combining our spectral method with constraints from transit observations, we are also able to derive the stellar properties of GJ 3470, a transiting planet hosting M dwarf. We estimate a mass of 0.53 ± 0.05 M_☉, a radius of 0.50 ± 0.05 R_☉, a metallicity, [Fe/H], of 0.12 ± 0.12, and a distance of 29.9±_(3.4)^(3.7)pc

Resolving the delta Andromedae spectroscopic binary with direct imaging

We present a direct image of the innermost companion to the red giant delta Andromedae using the Stellar Double Coronagraph at the Palomar Observatory. We use a Markov chain Monte Carlo based algorithm to simultaneously reduce the data and perform astrometry and photometry of the companion. We determine that the companion is most likely a main-sequence K-type star and is certainly not the previously hypothesized white dwarf.Comment: ApJ, accepted. 10 pages, 3 figure

Optimizing Doppler Surveys for Planet Yield

One of the most promising methods of discovering nearby, low-mass planets in the habitable zones of stars is the precision radial velocity technique. However, there are many challenges that must be overcome to efficiently detect low-amplitude Doppler signals. This is both due to the required instrumental sensitivity and the limited amount of observing time. In this article, we examine statistical and instrumental effects on precision radial velocity detection of extrasolar planets, an approach by which we maximize the planet yield in a fixed amount of observing time available on a given telescope. From this perspective, we show that G and K dwarfs observed at 400–600 nm are the best targets for surveys complete down to a given planet mass and out to a specified orbital period. Overall we find that M dwarfs observed at 700–800 nm are the best targets for habitable-zone planets, particularly when including the effects of systematic noise floors. Also, we give quantitative specifications of the instrumental stability necessary to achieve the required velocity precision

KELT-11b: A Highly Inflated Sub-Saturn Exoplanet Transiting the V = 8 Subgiant HD 93396

We report the discovery of a transiting exoplanet, KELT-11b, orbiting the bright (V = 8.0) subgiant HD 93396. A global analysis of the system shows that the host star is an evolved subgiant star with T_(eff) = 5370±51 K, M∗ = 1.438^(+0.061)_(−0.052) M⊙, R∗ = 2.72^(+0.21)_(−0.17) R⊙, log g∗= 3.727^(+0.040)_(−0.046), and [Fe/H]= 0.180 ± 0.075. The planet is a low-mass gas giant in a P = 4.736529 ± 0.00006 day orbit, with M_P = 0.195 ± 0.018 M_J, R_P = 1.37^(+0.15)_(−0.12) R_J, ρ_P = 0.093^(+0.028)_(−0.024) g cm^(−3) , surface gravity log g_P = 2.407^(+0.080)_(−0.086), and equilibrium temperature T_(eq) = 1712^(+51)_(−46) K. KELT-11 is the brightest known transiting exoplanet host in the southern hemisphere by more than a magnitude, and is the 6th brightest transit host to date. The planet is one of the most inflated planets known, with an exceptionally large atmospheric scale height (2763 km), and an associated size of the expected atmospheric transmission signal of 5.6%. These attributes make the KELT-11 system a valuable target for follow-up and atmospheric characterization, and it promises to become one of the benchmark systems for the study of inflated exoplanets

Miniature Exoplanet Radial Velocity Array I: design, commissioning, and early photometric results

The Miniature Exoplanet Radial Velocity Array (MINERVA) is a U.S.-based observational facility dedicated to the discovery and characterization of exoplanets around a nearby sample of bright stars. MINERVA employs a robotic array of four 0.7-m telescopes outfitted for both high-resolution spectroscopy and photometry, and is designed for completely autonomous operation. The primary science program is a dedicated radial velocity survey and the secondary science objective is to obtain high-precision transit light curves. The modular design of the facility and the flexibility of our hardware allows for both science programs to be pursued simultaneously, while the robotic control software provides a robust and efficient means to carry out nightly observations. We describe the design of MINERVA, including major hardware components, software, and science goals. The telescopes and photometry cameras are characterized at our test facility on the Caltech campus in Pasadena, California, and their on-sky performance is validated. The design and simulated performance of the spectrograph is briefly discussed as we await its completion. New observations from our test facility demonstrate sub-mmag photometric precision of one of our radial velocity survey targets, and we present new transit observations and fits of WASP-52b—a known hot-Jupiter with an inflated radius and misaligned orbit. The process of relocating the MINERVA hardware to its final destination at the Fred Lawrence Whipple Observatory in southern Arizona has begun, and science operations are expected to commence in 2015

Commissioning and first light results of an L'-band vortex coronagraph with the Keck II adaptive optics NIRC2 science instrument

On March 2015 an L'-band vortex coronagraph based on an Annular Groove Phase Mask made up of a diamond sub-wavelength grating was installed on NIRC2 as a demonstration project. This vortex coronagraph operates in the L' band not only in order to take advantage from the favorable star/planet contrast ratio when observing beyond the K band, but also to exploit the fact that the Keck II Adaptive Optics (AO) system delivers nearly extreme adaptive optics image quality (Strehl ratios values near 90%) at 3.7μm. We describe the hardware installation of the vortex phase mask during a routine NIRC2 service mission. The success of the project depends on extensive software development which has allowed the achievement of exquisite real-time pointing control as well as further contrast improvements by using speckle nulling to mitigate the effect of static speckles. First light of the new coronagraphic mode was on June 2015 with already very good initial results. Subsequent commissioning nights were interlaced with science nights by members of the VORTEX team with their respective scientific programs. The new capability and excellent results so far have motivated the VORTEX team and the Keck Science Steering Committee (KSSC) to offer the new mode in shared risk mode for 2016B

Speckle nulling wavefront control for Palomar and Keck

We present a speckle nulling code currently being used for high contrast imaging at the Palomar and Keck telescopes. The code can operate in open and closed loop and is self-calibrating, requiring no system model and minimal hand-coded parameters. Written in a modular fashion, it is straightforward to port to different instruments. It has been used with systems operating in the optical through thermal infrared, and can deliver nearly an order of magnitude improvement in raw contrast. We will be releasing this code to the public in the near future