S. Mark Ammons

The N2K Consortium. IV. New Temperatures and Metallicities for More than 100,000 FGK Dwarfs

We have created specialized target lists for radial velocity surveys that are biased toward stars that (1) possess planets and (2) are easiest to observe with current detection techniques. We use a procedure that uniformly estimates fundamental stellar properties of Tycho 2 stars, with errors, using spline functions of broadband photometry and proper motion found in Hipparcos/Tycho 2 and 2MASS. We provide estimates of Teff and distance for 2.4 × 106 Tycho 2 stars that lack trigonometric distances. For stars that appear to be FGK dwarfs, we also derive [Fe/H] and identify unresolved binary systems with mass ratios 1.25 < M1/M2 < 3.0. For FGK dwarfs with photometric error σV < 0.05, or V < 9, our temperature model gives a 1 σ error of σT = +58.7/ - 65.9 K and our metallicity model gives a 1 σ error of σ[Fe/H] = +0.13/ - 0.14 dex. The binarity model can be used to remove 70% of doubles with 1.25 < M1/M2 < 3.0 from a magnitude-limited sample of dwarfs at a cost of cutting 20% of the sample. Our estimates of distance and spectral type enable us to isolate 354,822 Tycho 2 dwarfs, 321,996 absent from Hipparcos, with giant contamination of 2.6% and 7.2%, respectively. Roughly 100,000 of these stars, not in Hipparcos, have sufficiently low photometric errors to retain 0.13-0.3 dex [Fe/H] accuracy and 80-100 K temperature accuracy (1 σ). Our metallicity estimates have been used to identify targets for N2K, a large-scale radial velocity search for hot jupiters, which has verified the errors presented here. The catalogs that we publish can be used to further large-scale studies of Galactic structure and chemical evolution and to provide potential reference stars for narrow-angle astrometry programs such as the Space Interferometry Mission and large-aperture optical interferometry.

The N2K Consortium. IV. New temperatures and metallicities for 100,000+ FGK dwarfs

We have created specialized target lists for radial velocity surveys that are biased toward stars that (1) possess planets and (2) are easiest to observe with current detection techniques. We use a procedure that uniformly estimates fundamental stellar properties of Tycho 2 stars, with errors, using spline functions of broadband photometry and proper motion found in Hipparcos/Tycho 2 and 2MASS. We provide estimates of Teff and distance for 2.4 × 106 Tycho 2 stars that lack trigonometric distances. For stars that appear to be FGK dwarfs, we also derive [Fe/H] and identify unresolved binary systems with mass ratios 1.25 < M1/M2 < 3.0. For FGK dwarfs with photometric error σV < 0.05, or V < 9, our temperature model gives a 1 σ error of σT = +58.7/ - 65.9 K and our metallicity model gives a 1 σ error of σ[Fe/H] = +0.13/ - 0.14 dex. The binarity model can be used to remove 70% of doubles with 1.25 < M1/M2 < 3.0 from a magnitude-limited sample of dwarfs at a cost of cutting 20% of the sample. Our estimates of distance and spectral type enable us to isolate 354,822 Tycho 2 dwarfs, 321,996 absent from Hipparcos, with giant contamination of 2.6% and 7.2%, respectively. Roughly 100,000 of these stars, not in Hipparcos, have sufficiently low photometric errors to retain 0.13-0.3 dex [Fe/H] accuracy and 80-100 K temperature accuracy (1 σ). Our metallicity estimates have been used to identify targets for N2K, a large-scale radial velocity search for hot jupiters, which has verified the errors presented here. The catalogs that we publish can be used to further large-scale studies of Galactic structure and chemical evolution and to provide potential reference stars for narrow-angle astrometry programs such as the Space Interferometry Mission and large-aperture optical interferometry.

β PICTORIS' INNER DISK in POLARIZED LIGHT and NEW ORBITAL PARAMETERS for β PICTORIS b

© 2015. The American Astronomical Society. All rights reserved. We present H-band observations of β Pic with the Gemini Planet Imagers (GPIs) polarimetry mode that reveal the debris disk between ∼0.″3 (6 AU) and ∼1.″7 (33 AU), while simultaneously detecting β Pic b. The polarized disk image was fit with a dust density model combined with a Henyey-Greenstein scattering phase function. The best-fit model indicates a disk inclined to the line of sight () with a position angle (PA) (slightly offset from the main outer disk, ), that extends from an inner disk radius of to well outside GPIs field of view. In addition, we present an updated orbit for β Pic b based on new astrometric measurements taken in GPIs spectroscopic mode spanning 14 months. The planet has a semimajor axis of , with an eccentricity The PA of the ascending node is offset from both the outer main disk and the inner disk seen in the GPI image. The orbital fit constrains the stellar mass of β Pic to Dynamical sculpting by β Pic b cannot easily account for the following three aspects of the inferred disk properties: (1) the modeled inner radius of the disk is farther out than expected if caused by β Pic b; (2) the mutual inclination of the inner disk and β Pic b is when it is expected to be closer to zero; and (3) the aspect ratio of the disk () is larger than expected from interactions with β Pic b or self-stirring by the disks parent bodies.

The open-loop control of MEMS: modeling and experimental results

As adaptive optics (AO) technology progresses, both wide-field and high-order wavefront correction systems become reachable. Deformable mirrors (DMs) in these advanced architectures must exhibit exemplary performance to give low wavefront error. Such DMs must be economically attainable, meet stroke as well as flatness requirements, and show stable and repeatable actuation. Micro-electrical mechanical systems (MEMS) deformable mirrors, undergoing testing and characterization in the Laboratory for Adaptive Optics (LAO) at the University of California at Santa Cruz, show promise on these fronts. In addition to requiring advanced deformable mirror technology, these progressive AO architectures require advanced DM control algorithms. We therefore present a formulation for accurate open-loop control of MEMS deformable mirrors. The electrostatic actuators in a discrete-actuator MEMS device are attached via posts to a thin reflective top plate. The plate itself can be well-modeled by the thin plate equation. The actuators, although nonlinear in their response to applied voltage and deformation, are independent of each other except through forces transmitted by the top plate and can be empirically modeled via a calibration procedure we will describe. In this paper we present the modeling and laboratory results. So far in the lab we have achieved open loop control to approximately 15 nm accuracy in response to arbitrary commands of approximately 500 nm amplitude. Open-loop control enables a wealth of new applications for astronomical adaptive optics instruments, particularly in multi-object integral field spectroscopy, which we will describe.

Astrometric performance of the Gemini multiconjugate adaptive optics system in crowded fields

The Gemini multiconjugate adaptive optics system (GeMS) is a facility instrument for the Gemini South telescope. It delivers uniform, near-diffraction-limited image quality at near-infrared wavelengths over a 2 arc min field of view. Together with the Gemini South Adaptive Optics Imager (GSAOI), a near-infrared wide-field camera, GeMS/GSAOIs combination of high spatial resolution and a large field of view will make it a premier facility for precision astrometry. Potential astrometric science cases cover a broad range of topics including exoplanets, star formation, stellar evolution, star clusters, nearby galaxies, black holes and neutron stars, and the Galactic Centre. In this paper, we assess the astrometric performance and limitations of GeMS/GSAOI. In particular, we analyse deep, mono-epoch images, multi-epoch data and distortion calibration. We find that for single-epoch, undithered data, an astrometric error below 0.2 mas can be achieved for exposure times exceeding 1 min, provided enough stars are available to remove high-order distortions. We show however that such performance is not reproducible for multi-epoch observations, and an additional systematic error of similar to 0.4 mas is evidenced. This systematic multi-epoch error is the dominant error term in the GeMS/GSAOI astrometric error budget, and it is thought to be due to time-variable distortion induced by gravity flexure.

Optimal Mass Configurations for Lensing High-redshift Galaxies

We investigate the gravitational lensing properties of lines of sight containing multiple cluster-scale halos, motivated by their ability to lens very high redshift (z ~ 10) sources into detectability. We control for the total mass along the line of sight, isolating the effects of distributing the mass among multiple halos and of varying the physical properties of the halos. Our results show that multiple-halo lines of sight can increase the magnified source-plane region compared to the single cluster lenses typically targeted for lensing studies and thus are generally better fields for detecting very high redshift sources. The configurations that result in optimal lensing cross sections benefit from interactions between the lens potentials of the halos when they overlap somewhat on the sky, creating regions of high magnification in the source plane not present when the halos are considered individually. The effect of these interactions on the lensing cross section can even be comparable to changing the total mass of the lens from 1015 M ? to 3 ? 1015 M ?. The gain in lensing cross section increases as the mass is split into more halos, provided that the lens potentials are projected close enough to interact with each other. A nonzero projected halo angular separation, equal halo mass ratio, and high projected halo concentration are the best mass configurations, whereas projected halo ellipticity, halo triaxiality, and the relative orientations of the halos are less important. Such high-mass, multiple-halo lines of sight exist in the Sloan Digital Sky Survey.

The N2K consortium. VII. Atmospheric parameters of 1907 metal-rich stars: Finding planet-search targets

We report high-precision atmospheric parameters for 1907 stars in the N2K low-resolution spectroscopic survey, designed to identify metal-rich FGK dwarfs likely to harbor detectable planets. Of these stars, 284 are in the ideal temperature range for planet searches, Teff ≤ 6000 K, and have a 10% or greater probability of hosting planets based on their metallicities. The stars in the low-resolution spectroscopic survey should eventually yield >60 new planets, including 8-9 hot Jupiters. Short-period planets have already been discovered orbiting the survey targets HIP 14810 and HD 149143.

Visible light laser guidestar experimental system (Villages): on-sky tests of new technologies for visible wavelength all-sky coverage adaptive optics systems

The Lick Observatory is pursuing new technologies for adaptive optics that will enable feasible low cost laser guidestar systems for visible wavelength astronomy. The Villages system, commissioned at the 40 inch Nickel Telescope this past Fall, serves as an on-sky testbed for new deformable mirror technology (high-actuator count MEMS devices), open-loop wavefront sensing and control, pyramid wavefront sensing, and laser uplink correction. We describe the goals of our experiments and present the early on-sky results of AO closed-loop and open-loop operation. We will also report on our plans for on-sky tests of the direct-phase measuring pyramid-lenslet wavefront sensor and plans for installing a laser guidestar system.

THE ORBIT and TRANSIT PROSPECTS for β PICTORIS b CONSTRAINED with ONE MILLIARCSECOND ASTROMETRY

Gemini Observatory; National Science Foundation [NSF AST-1518332]; NASA [NNX15AC89G, NNX15AD95G]; U.S. Department of Energy by Lawrence Livermore National Laboratory [DE-AC52-07NA27344]

Performance of the Gemini Planet Imager’s adaptive optics system

The Gemini Planet Imagers adaptive optics (AO) subsystem was designed specifically to facilitate high-contrast imaging. A definitive description of the systems algorithms and technologies as built is given. 564 AO telemetry measurements from the Gemini Planet Imager Exoplanet Survey campaign are analyzed. The modal gain optimizer tracks changes in atmospheric conditions. Science observations show that image quality can be improved with the use of both the spatially filtered wavefront sensor and linear-quadratic-Gaussian control of vibration. The error budget indicates that for all targets and atmospheric conditions AO bandwidth error is the largest term.