arXiv subjects

Phil Hinz

Publications and source records attributed to Phil Hinz.

32 records · Page 2Linked to original sources

arXiv2019

Status of commissioning stabilized infrared Fizeau interferometry with LBTI

The Large Binocular Telescope Interferometer (LBTI) has the longest baseline in the world, 22.7 m, for performing astronomical interferometry in Fizeau mode, which involves beam combination in a focal plane and preserves a wide field-of-view. LBTI can operate in this mode at wavelengths of 1.2 to 5 and 8 to 12 μm, making it a unique platform for carrying out high-resolution imaging of circumstellar disks, evolved stars, solar system objects, and possibly searches for planets, in the thermal infrared. Over the past five years, LBTI has carried out a considerable number of interferometric observations by combining the beams near a pupil plane to carry out nulling interferometry. This mode is useful for measuring small luminosity level offsets, such as those of exozodiacal dust disks. The Fizeau mode, by contrast, is more useful for generating an image of the target because it has more (u, v) (Fourier) plane coverage. However, the Fizeau mode is still in an ongoing process of commissioning. Sensitive Fizeau observations require active phase control, increased automation, and the removal of non-common-path aberrations (NCPA) between the science and phase beams. This increased level of control will increase the fringe contrast, enable longer integrations, and reduce time overheads. We are in the process of writing a correction loop to remove NCPA, and have carried out tests on old and synthetic data. We have also carried out on-sky Fizeau engineering tests in fall 2018 and spring 2019. In this article, we share lessons learned and strategies developed as a result of these tests.

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arXiv2018

Speckle statistics in adaptive optics images at visible wavelengths

Residual speckles in adaptive optics (AO) images represent a well-known limitation on the achievement of the contrast needed for faint source detection. Speckles in AO imagery can be the result of either residual atmospheric aberrations, not corrected by the AO, or slowly evolving aberrations induced by the optical system. We take advantage of the high temporal cadence (1 ms) of the data acquired by the System for Coronagraphy with High-order Adaptive Optics from R to K bands-VIS forerunner experiment at the Large Binocular Telescope to characterize the AO residual speckles at visible wavelengths. An accurate knowledge of the speckle pattern and its dynamics is of paramount importance for the application of methods aimed at their mitigation. By means of both an automatic identification software and information theory, we study the main statistical properties of AO residuals and their dynamics. We therefore provide a speckle characterization that can be incorporated into numerical simulations to increase their realism and to optimize the performances of both real-time and postprocessing techniques aimed at the reduction of the speckle noise.

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arXiv2018

MagAO-X: project status and first laboratory results

MagAO-X is an entirely new "extreme" adaptive optics system for the Magellan Clay 6.5 m telescope, funded by the NSF MRI program starting in Sep 2016. The key science goal of MagAO-X is high-contrast imaging of accreting protoplanets at H$α$. With 2040 actuators operating at up to 3630 Hz, MagAO-X will deliver high Strehls (>70%), high resolution (19 mas), and high contrast ($< 1\times10^{-4}$) at H$α$ (656 nm). We present an overview of the MagAO-X system, review the system design, and discuss the current project status.

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arXiv2018

Towards controlled Fizeau observations with the Large Binocular Telescope

The Large Binocular Telescope Interferometer (LBTI) can perform Fizeau interferometry in the focal plane, which accesses spatial information out to the LBT's full 22.7-m edge-to-edge baseline. This mode has previously been used to obtain science data, but has been limited to observations where the optical path difference (OPD) between the two beams is not controlled, resulting in unstable fringes on the science detectors. To maximize the science return, we are endeavoring to stabilize the OPD and tip-tilt variations and make the LBTI Fizeau mode optimized and routine. Here we outline the optical configuration of LBTI's Fizeau mode and our strategy for commissioning this observing mode.

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arXiv2018

The Orbit of the Companion to HD 100453A: Binary-Driven Spiral Arms in a Protoplanetary Disk

HD 100453AB is a 10+/-2 Myr old binary whose protoplanetary disk was recently revealed to host a global two-armed spiral structure. Given the relatively small projected separation of the binary (1.05", or ~108 au), gravitational perturbations by the binary seemed to be a likely driving force behind the formation of the spiral arms. However, the orbit of these stars remained poorly understood, which prevented a proper treatment of the dynamical influence of the companion on the disk. We observed HD 100453AB between 2015-2017 utilizing extreme adaptive optics systems on the Very Large Telescope and Magellan Clay Telescope. We combined the astrometry from these observations with published data to constrain the parameters of the binary's orbit to a=1.06"+/-0.09", e=0.17+/-0.07, and i=32.5+/- 6.5 degrees. We utilized publicly available ALMA CO data to constrain the inclination of the disk to i~28 degrees, which is relatively co-planar with the orbit of the companion and consistent with previous estimates from scattered light images. Finally, we input these constraints into hydrodynamical and radiative transfer simulations to model the structural evolution of the disk. We find that the spiral structure and truncation of the circumprimary disk in HD 100453 are consistent with a companion-dirven origin. Furthermore, we find that the primary star's rotation, its outer disk, and the companion exhibit roughly the same direction of angular momentum, and thus the system likely formed from the same parent body of material.

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arXiv2017

Precision Time-series Photometry in the Thermal Infrared with a 'Wall-Eyed' Pointing Mode at the Large Binocular Telescope

Time-series photometry taken from ground-based facilities is improved with the use of comparison stars due to the short timescales of atmospheric-induced variability. However, the sky is bright in the thermal infrared (3-5 um), and the correspondingly small fields-of-view of available detectors make it highly unusual to have a calibration star in the same field as a science target. Here we present a new method of obtaining differential photometry by simultaneously imaging a science target and a calibrator star, separated by <2 amin, onto a 10x10 asec field-of-view detector. We do this by taking advantage of the LBT's unique binocular design to point the two co-mounted telescopes apart and simultaneously obtain both targets in three sets of observations. Results indicate that the achievable scatter in Ls-band (3.3 um) is at the percent level for bright targets, and possibly better with heavier sampling and characterization of the systematics.

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arXiv2017

The TWA 3 Young Triple System: Orbits, Disks, Evolution

We have characterized the spectroscopic orbit of the TWA 3A binary and provide preliminary families of probable solutions for the TWA 3A visual orbit as well as for the wide TWA 3A--B orbit. TWA 3 is a hierarchical triple located at 34 pc in the $\sim$10 Myr old TW Hya association. The wide component separation is 1."55; the close pair was first identified as a possible binary almost 20 years ago. We initially identified the 35-day period orbital solution using high-resolution infrared spectroscopy which angularly resolved the A and B components. We then refined the preliminary orbit by combining the infrared data with a re-analysis of our high-resolution optical spectroscopy. The orbital period from the combined spectroscopic solution is $\sim$35 days, the eccentricity is $\sim$0.63, and the mass ratio is $\sim$0.84; although this high mass ratio would suggest that optical spectroscopy alone should be sufficient to identify the orbital solution, the presence of the tertiary B component likely introduced confusion in the blended optical spectra. Using millimeter imaging from the literature, we also estimate the inclinations of the stellar orbital planes with respect to the TWA 3A circumbinary disk inclination and find that all three planes are likely misaligned by at least $\sim$30 degrees. The TWA 3A spectroscopic binary components have spectral types of M4.0 and M4.5; TWA 3B is an M3. We speculate that the system formed as a triple, is bound, and that its properties were shaped by dynamical interactions between the inclined orbits and disk.

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arXiv2017

Improved Constraints on the Disk Around MWC 349A from the 23-Meter LBTI

We present new spatially resolved observations of MWC 349A from the Large Binocular Telescope Interferometer (LBTI), a 23-meter baseline interferometer made up of two, co-mounted 8-meter telescopes. MWC 349A is a B[e] star with an unknown evolutionary state. Proposed scenarios range from a young stellar object (YSO), to a B[e] supergiant, to a tight binary system. Radio continuum and recombination line observations of this source revealed a sub-arcsecond bipolar outflow surrounding a ~100 mas circumstellar disk. Followup infrared studies detected the disk, and suggested that it may have skew and an inner clearing. Our new infrared interferometric observations, which have more than twice the resolution of previously-published datasets, support the presence of both skew and a compact infrared excess. They rule out inner clearings with radii greater than ~14 mas. We show the improvements in disk parameter constraints provided by LBTI, and discuss the inferred disk parameters in the context of the posited evolutionary states for MWC 349A.

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arXiv2016

L-band Spectroscopy with Magellan-AO/Clio2: First Results on Young Low-Mass Companions

L-band spectroscopy is a powerful probe of cool low-gravity atmospheres: The P, Q, and R branch fundamental transitions of methane near 3.3 $μ$m provide a sensitive probe of carbon chemistry; cloud thickness modifies the spectral slope across the band; and H$_{3}^{+}$ opacity can be used to detect aurorae. Many directly imaged gas-giant companions to nearby young stars exhibit L-band fluxes distinct from the field population of brown dwarfs at the same effective temperature. Here we describe commissioning the L-band spectroscopic mode of Clio2, the 1-5 $μ$m instrument behind the Magellan adaptive-optics system. We use this system to measure L-band spectra of directly imaged companions. Our spectra are generally consistent with the parameters derived from previous near-infrared spectra for these late M to early L type objects. Therefore, deviations from the field sequence are constrained to occur below 1500 K. This range includes the L-T transition for field objects and suggests that observed discrepancies are due to differences in cloud structure and CO/CH$_{4}$ chemistry.

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arXiv2016

197 Candidates and 104 Validated Planets in K2's First Five Fields

We present 197 planet candidates discovered using data from the first year of the NASA K2 mission (Campaigns 0-4), along with the results of an intensive program of photometric analyses, stellar spectroscopy, high-resolution imaging, and statistical validation. We distill these candidates into sets of 104 validated planets (57 in multi-planet systems), 30 false positives, and 63 remaining candidates. Our validated systems span a range of properties, with median values of R_P = 2.3 R_E, P=8.6 d, Tef = 5300 K, and Kp=12.7 mag. Stellar spectroscopy provides precise stellar and planetary parameters for most of these systems. We show that K2 has increased by 30% the number of small planets known to orbit moderately bright stars (1-4 R_E, Kp=9-13 mag). Of particular interest are 37 planets smaller than 2 R_E, 15 orbiting stars brighter than Kp=11.5, five receiving Earth-like irradiation levels, and several multi-planet systems -- including four planets orbiting the M dwarf K2-72 near mean-motion resonances. By quantifying the likelihood that each candidate is a planet we demonstrate that our candidate sample has an overall false positive rate of 15-30%, with rates substantially lower for small candidates (< 2 R_E) and larger for candidates with radii > 8 R_E and/or with P < 3 d. Extrapolation of the current planetary yield suggests that K2 will discover between 500-1000 planets in its planned four-year mission -- assuming sufficient follow-up resources are available. Efficient observing and analysis, together with an organized and coherent follow-up strategy, is essential to maximize the efficacy of planet-validation efforts for K2, TESS, and future large-scale surveys.

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arXiv2014

Into the Blue: AO Science with MagAO in the Visible

We review astronomical results in the visible (λ<1μm) with adaptive optics. Other than a brief period in the early 1990s, there has been little astronomical science done in the visible with AO until recently. The most productive visible AO system to date is our 6.5m Magellan telescope AO system (MagAO). MagAO is an advanced Adaptive Secondary system at the Magellan 6.5m in Chile. This secondary has 585 actuators with < 1 msec response times (0.7 ms typically). We use a pyramid wavefront sensor. The relatively small actuator pitch (~23 cm/subap) allows moderate Strehls to be obtained in the visible (0.63-1.05 microns). We use a CCD AO science camera called "VisAO". On-sky long exposures (60s) achieve <30mas resolutions, 30% Strehls at 0.62 microns (r') with the VisAO camera in 0.5" seeing with bright R < 8 mag stars. These relatively high visible wavelength Strehls are made possible by our powerful combination of a next generation ASM and a Pyramid WFS with 378 controlled modes and 1000 Hz loop frequency. We'll review the key steps to having good performance in the visible and review the exciting new AO visible science opportunities and refereed publications in both broad-band (r,i,z,Y) and at Halpha for exoplanets, protoplanetary disks, young stars, and emission line jets. These examples highlight the power of visible AO to probe circumstellar regions/spatial resolutions that would otherwise require much larger diameter telescopes with classical infrared AO cameras.

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arXiv2014

LEECH: A 100 Night Exoplanet Imaging Survey at the LBT

In February 2013, the LEECH (LBTI Exozodi Exoplanet Common Hunt) survey began its 100-night campaign from the Large Binocular Telescope atop Mount Graham in Arizona. LEECH nearly complements other high-contrast planet imaging efforts by observing stars in L' band (3.8 microns) as opposed to the shorter wavelength near-infrared bands (1-2.3 microns). This part of the spectrum offers deeper mass sensitivity for intermediate age (several hundred Myr-old) systems, since their Jovian-mass planets radiate predominantly in the mid-infrared. In this proceedings, we present the science goals for LEECH and a preliminary contrast curve from some early data.

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arXiv2010

High-Contrast 3.8 Micron Imaging Of The Brown Dwarf/Planet-Mass Companion to GJ 758

We present L' band (3.8 $μm$) MMT/Clio high-contrast imaging data for the nearby star GJ 758, which was recently reported by Thalmann et al. (2009) to have one -- possibly two-- faint comoving companions (GJ 758B and ``C", respectively). GJ 758B is detected in two distinct datasets. Additionally, we report a \textit{possible} detection of the object identified by Thalmann et al as ``GJ 758C" in our more sensitive dataset, though it is likely a residual speckle. However, if it is the same object as that reported by Thalmann et al. it cannot be a companion in a bound orbit. GJ 758B has a H-L' color redder than nearly all known L--T8 dwarfs. Based on comparisons with the COND evolutionary models, GJ 758B has T$_{e}$ $\sim$ 560 K$^{^{+150 K}_{-90K}}$ and a mass ranging from $\sim$ 10--20 M$_{J}$ if it is $\sim$ 1 Gyr old to $\sim$ 25--40 M$_{J}$ if it is 8.7 Gyr old. GJ 758B is likely in a highly eccentric orbit, e $\sim$ 0.73$^{^{+0.12}_{-0.21}}$, with a semimajor axis of $\sim$ 44 AU$^{^{+32 AU}_{-14 AU}}$. Though GJ 758B is sometimes discussed within the context of exoplanet direct imaging, its mass is likely greater than the deuterium-burning limit and its formation may resemble that of binary stars rather than that of jovian-mass planets.

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arXiv2006

High Contrast L' Band Adaptive Optics Imaging to Detect Extrasolar Planets

We are carrying out a survey to search for giant extrasolar planets around nearby, moderate-age stars in the mid-infrared L' and M bands (3.8 and 4.8 microns, respectively), using the Clio camera with the adaptive optics system on the MMT telescope. To date we have observed 7 stars, of a total 50 planned, including GJ 450 (distance about 8.55pc, age about 1 billion years, no real companions detected), which we use as our example here. We report the methods we use to obtain extremely high contrast imaging in L', and the performance we have obtained. We find that the rotation of a celestial object over time with respect to a telescope tracking it with an altazimuth mount can be a powerful tool for subtracting telescope-related stellar halo artifacts and detecting planets near bright stars. We have carried out a thorough Monte Carlo simulation demonstrating our ability to detect planets as small as 6 Jupiter masses around GJ 450. The division of a science data set into two independent parts, with companions required to be detected on both in order to be recognized as real, played a crucial role in detecting companions in this simulation. We mention also our discovery of a previously unknown faint stellar companion to another of our survey targets, HD 133002. Followup is needed to confirm this as a physical companion, and to determine its physical properties.

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