38 research outputs found
Systematic Multi-Epoch Monitoring of LkCa 15: Dynamic Dust Structures on Solar-System Scales
We present the highest angular resolution infrared monitoring of LkCa 15, a
young solar analog hosting a transition disk. This system has been the subject
of a number of direct imaging studies from the millimeter through the optical,
which have revealed multiple protoplanetary disk rings as well as three
orbiting protoplanet candidates detected in infrared continuum (one of which
was simultaneously seen at H). We use high-angular-resolution infrared
imaging from 2014-2020 to systematically monitor these infrared signals and
determine their physical origin. We find that three self-luminous protoplanets
cannot explain the positional evolution of the infrared sources, since the
longer time baseline images lack the coherent orbital motion that would be
expected for companions. However, the data still strongly prefer a
time-variable morphology that cannot be reproduced by static scattered-light
disk models. The multi-epoch observations suggest the presence of complex and
dynamic substructures moving through the forward-scattering side of the disk at
AU, or quickly-varying shadowing by closer-in material. We explore
whether the previous H detection of one candidate would be inconsistent
with this scenario, and in the process develop an analytical signal-to-noise
penalty for H excesses detected near forward-scattered light. Under
these new noise considerations, the H detection is not strongly
inconsistent with forward scattering, making the dynamic LkCa 15 disk a natural
explanation for both the infrared and H data.Comment: 24 pages, 11 figures, accepted for publication in Ap
End-to-end Simulation of the SCALES Integral Field Spectrograph
We present end-to-end simulations of SCALES, the third generation
thermal-infrared diffraction limited imager and low/med-resolution integral
field spectrograph (IFS) being designed for Keck. The 2-5 micron sensitivity of
SCALES enables detection and characterization of a wide variety of exoplanets,
including exoplanets detected through long-baseline astrometry, radial-velocity
planets on wide orbits, accreting protoplanets in nearby star-forming regions,
and reflected-light planets around the nearest stars. The simulation goal is to
generate high-fidelity mock data to assess the scientific capabilities of the
SCALES instrument at current and future design stages. The simulation processes
arbitrary-resolution input intensity fields with a proposed observation pattern
into an entire mock dataset of raw detector read-out lenslet-based IFS frames
with calibrations and metadata, which are then reduced by the IFS data
reduction pipeline to be analyzed by the user.Comment: 13 pages, 8 figures, Society of Photo-Optical Instrumentation
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Detecting planetary mass companions near the water frost-line using <i>JWST</i> interferometry
JWST promises to be the most versatile infrared observatory for the next two decades. The Near Infrared and Slitless Spectrograph (NIRISS) instrument, when used in the Aperture Masking Interferometry (AMI) mode, will provide an unparalleled combination of angular resolution and sensitivity compared to any existing observatory at mid-infrared wavelengths. Using simulated observations in conjunction with evolutionary models, we present the capability of this mode to image planetary mass companions around nearby stars at small orbital separations near the circumstellar water frost-line for members of the young, kinematic moving groups β Pictoris, TW Hydrae, as well as the Taurus-Auriga association. We show that for appropriately chosen stars, JWST /NIRISS operating in the AMI mode can image sub-Jupiter companions near the water frost-lines with ∼68% confidence. Among these, M-type stars are the most promising. We also show that this JWST mode will improve the minimum inner working angle by as much as ∼50% in most cases when compared to the survey results from the best ground-based exoplanet direct imaging facilities (e.g. VLT/SPHERE). We also discuss how the NIRISS/AMI mode will be especially powerful for the mid-infrared characterization of the numerous exoplanets expected to be revealed by Gaia. When combined with dynamical masses from Gaia, such measurements will provide a much more robust characterization of the initial entropies of these young planets, thereby placing powerful constraints on their early thermal histories
Efficient detection and characterization of exoplanets within the diffraction limit: nulling with a mode-selective photonic lantern
Coronagraphs allow for faint off-axis exoplanets to be observed, but are
limited to angular separations greater than a few beam widths. Accessing
closer-in separations would greatly increase the expected number of detectable
planets, which scales inversely with the inner working angle. The Vortex Fiber
Nuller (VFN) is an instrument concept designed to characterize exoplanets
within a single beam-width. It requires few optical elements and is compatible
with many coronagraph designs as a complementary characterization tool.
However, the peak throughput for planet light is limited to about 20%, and the
measurement places poor constraints on the planet location and flux ratio. We
propose to augment the VFN design by replacing its single-mode fiber with a
six-port mode-selective photonic lantern, retaining the original functionality
while providing several additional ports that reject starlight but couple
planet light. We show that the photonic lantern can also be used as a nuller
without a vortex. We present monochromatic simulations characterizing the
response of the Photonic Lantern Nuller (PLN) to astrophysical signals and
wavefront errors, and show that combining exoplanet flux from the nulled ports
significantly increases the overall throughput of the instrument. We show using
synthetically generated data that the PLN detects exoplanets more effectively
than the VFN. Furthermore, with the PLN, the exoplanet can be partially
localized, and its flux ratio constrained. The PLN has the potential to be a
powerful characterization tool complementary to traditional coronagraphs in
future high-contrast instruments.Comment: 15 pages, 12 figure
Imaging protoplanets: observing transition disks with non-redundant masking
Transition disks, protoplanetary disks with inner clearings, are promising
objects in which to directly image forming planets. The high contrast imaging
technique of non-redundant masking is well posed to detect planetary mass
companions at several to tens of AU in nearby transition disks. We present
non-redundant masking observations of the T Cha and LkCa 15 transition disks,
both of which host posited sub-stellar mass companions. However, due to a loss
of information intrinsic to the technique, observations of extended sources
(e.g. scattered light from disks) can be misinterpreted as moving companions.
We discuss tests to distinguish between these two scenarios, with applications
to the T Cha and LkCa 15 observations. We argue that a static,
forward-scattering disk can explain the T Cha data, while LkCa 15 is best
explained by multiple orbiting companions.Comment: SPIE conference proceedin
The Demographics and Atmospheres of Giant Planets with the ELTs
Gas giants are the most readily detectable exoplanets but fundamental
questions about their system architectures, formation, migration, and
atmospheres have been unanswerable with the current generation of ground- and
space-based facilities. The dominant techniques to detect and characterize
giant planets radial velocities, transits, direct imaging, microlensing,
and astrometry are each isolated to a limited range of planet masses,
separations, ages, and temperatures. These windows into the arrangement and
physical properties of giant planets have spawned new questions about the
timescale and location of their assembly; the distributions of planet mass and
orbital separation at young and old ages; the composition and structure of
their atmospheres; and their orbital and rotational angular momentum
architectures. The ELTs will address these questions by building bridges
between these islands of mass, orbital distance, and age. The angular
resolution, collecting area, all-sky coverage, and novel instrumentation suite
of these facilities are needed to provide a complete map of the orbits and
atmospheric evolution of gas giant planets (0.310 ) across
space (0.1100 AU) and time (1 Myr to 10 Gyr). This white paper highlights
the scientific potential of the GMT and TMT to address these outstanding
questions, with a particular focus on the role of direct imaging and
spectroscopy of large samples of giant planets that will soon be made available
with .Comment: White paper for the Astro2020 decadal surve
Characterization of diamond-turned optics for SCALES
High-contrast imaging has been used to discover and characterize dozens of
exoplanets to date. The primary limiting performance factor for these
instruments is contrast, the ratio of exoplanet to host star brightness that an
instrument can successfully resolve. Contrast is largely determined by
wavefront error, consisting of uncorrected atmospheric turbulence and optical
aberrations downstream of AO correction. Single-point diamond turning allows
for high-precision optics to be manufactured for use in astronomical
instrumentation, presenting a cheaper and more versatile alternative to
conventional glass polishing. This work presents measurements of wavefront
error for diamond-turned aluminum optics in the Slicer Combined with an Array
of Lenslets for Exoplanet Spectroscopy (SCALES) instrument, a 2-5 micron
coronagraphic integral field spectrograph under construction for Keck
Observatory. Wavefront error measurements for these optics are used to simulate
SCALES' point spread function using physical optics propagation software poppy,
showing that SCALES' contrast performance is not limited by wavefront error
from internal instrument optics.Comment: Techniques and Instrumentation for Detection of Exoplanets X