29 research outputs found
A Visible-light Lyot Coronagraph for SCExAO/VAMPIRES
We describe the design and initial results from a visible-light Lyot
coronagraph for SCExAO/VAMPIRES. The coronagraph is comprised of four
hard-edged, partially transmissive focal plane masks with inner working angles
of 36 mas, 55 mas, 92 mas, and 129 mas, respectively. The Lyot stop is a
reflective, undersized design with a geometric throughput of 65.7%. Our
preliminary on-sky contrast is 1e-2 at 0.1" to 1e-4 at 0.75" for all mask
sizes. The coronagraph was deployed in early 2022 and is available for open
use.Comment: Proceedings of SPIE 2022 Astronomical Instrumentation and Telescopes
conference (#12184-163
SCExAO as a precursor to an ELT exoplanet direct imaging instrument
The Subaru Coronagraphic Extreme AO (SCExAO) instrument consists of a high
performance Phase Induced Amplitude Apodisation (PIAA) coronagraph combined
with an extreme Adaptive Optics (AO) system operating in the near-infrared (H
band). The extreme AO system driven by the 2000 element deformable mirror will
allow for Strehl ratios >90% to be achieved in the H-band when it goes closed
loop. This makes the SCExAO instrument a powerful platform for high contrast
imaging down to angular separations of the order of 1lambda/D and an ideal
testbed for exploring coronagraphic techniques for ELTs. In this paper we
report on the recent progress in regards to the development of the instrument,
which includes the addition of a visible bench that makes use of the light at
shorter wavelengths not currently utilized by SCExAO and closing the loop on
the tip/tilt wavefront sensor. We will also discuss several exciting guest
instruments which will expand the capabilities of SCExAO over the next few
years; namely CHARIS which is a integral field spectrograph as well as
VAMPIRES, a visible aperture masking experiment based on polarimetric analysis
of circumstellar disks. In addition we will elucidate the unique role extreme
AO systems will play in enabling high precision radial velocity spectroscopy
for the detection of small companions.Comment: 7 pages, 2 figures Proceedings of AO4ELTs3 conference, paper 13396,
Florence, Italy, May 201
High Contrast Imaging at the Photon Noise Limit with WFS-based PSF Calibration
Speckle Noise is the dominant source of error in high contrast imaging with
adaptive optics system. We discuss the potential for wavefront sensing
telemetry to calibrate speckle noise with sufficient precision and accuracy so
that it can be removed in post-processing of science images acquired by high
contrast imaging instruments. In such a self-calibrating system, exoplanet
detection would be limited by photon noise and be significantly more robust and
efficient than in current systems. We show initial laboratory and on-sky tests,
demonstrating over short timescale that residual speckle noise is indeed
calibrated to an accuracy exceeding readout and photon noise in the high
contrast region. We discuss immplications for the design of space and ground
high-contrast imaging systems.Comment: 12 pages, 7 figures, To appear in SPIE Proceedings of Astronomical
Telescopes + Instrumentation, 2022. arXiv admin note: text overlap with
arXiv:2109.1395
Planet(esimal)s Around Stars with TESS (PAST) III: A Search for Triplet He I in the Atmospheres of Two 200 Myr-old Planets
We report a search for excess absorption in the 1083.2 nm line of ortho
(triplet) helium during transits of TOI-1807b and TOI-2076b, 1.25 and
2.5R planets on 0.55- and 10.4-day orbits around nearby
200~Myr-old K dwarf stars. We limit the equivalent width of any
transit-associated absorption to 4 and 8 mA, respectively. We limit the
escape of solar-composition atmospheres from TOI-1807b and TOI-2076b to
1 and 0.1M Gyr, respectively,
depending on wind temperature. The absence of a H/He signature for TOI-1807b is
consistent with a measurement of mass indicating a rocky body and the
prediction by a hydrodynamic model that any H-dominated atmosphere would be
unstable and already have been lost. Differential spectra obtained during the
transit of TOI-2076b contain a He I-like feature, but this closely resembles
the stellar line and extends beyond the transit interval. Until additional
transits are observed, we suspect this to be the result of variation in the
stellar He I line produced by rotation of active regions and/or flaring on the
young, active host star. Non-detection of escape could mean that TOI-2076b is
more massive than expected, the star is less EUV-luminous, the models
overestimate escape, or the planet has a H/He-poor atmosphere that is primarily
molecules such as HO. Photochemical models of planetary winds predict a
semi-major axis at which triplet He I observations are most sensitive to mass
loss: TOI-2076b orbits near this optimum. Future surveys could use a distance
criterion to increase the yield of detections.Comment: Accepted to MNRA
Absence of extended atmospheres in low-mass star radius-gap planets GJ 9827 b, GJ 9827 d and TOI-1235 b
\textit{Kepler} showed a paucity of planets with radii of 1.5 - 2 around solar mass stars but this radius-gap has not been well
studied for low-mass star planets. Energy-driven escape models like
photoevaporation and core-powered mass-loss predict opposing transition regimes
between rocky and non-rocky planets when compared to models depicting planets
forming in gas-poor environments. Here we present transit observations of three
super-Earth sized planets in the radius-gap around low-mass stars using
high-dispersion InfraRed Doppler (IRD) spectrograph on the Subaru 8.2m
telescope. The planets GJ 9827 b and d orbit around a K6V star and TOI-1235 b
orbits a M0.5 star. We limit any planet-related absorption in the 1083.3 nm
lines of triplet He I by placing an upper-limit on the equivalent width of
14.71 m{\AA}, 18.39 m{\AA}, and 1.44 m{\AA}, for GJ 9827 b (99% confidence), GJ
9827 d (99% confidence) and TOI-1235 b (95% confidence) respectively. Using a
Parker wind model, we cap the mass-loss at 0.25
Gyr and 0.2 Gyr for GJ 9827 b and d,
respectively (99% confidence), and 0.05 Gyr for
TOI-1235 b (95\% confidence) for a representative wind temperature of 5000 K.
Our observed results for the three planets are more consistent with the
predictions from photoevaporation and/or core-powered mass-loss models than the
gas-poor formation models. However, more planets in the radius-gap regime
around the low-mass stars are needed to robustly predict the atmospheric
evolution in planets around low-mass stars.Comment: Accepted for MNRAS. 12 pages, 15 figure
The path to detecting extraterrestrial life with astrophotonics
Astrophysical research into exoplanets has delivered thousands of confirmed
planets orbiting distant stars. These planets span a wide ranges of size and
composition, with diversity also being the hallmark of system configurations,
the great majority of which do not resemble our own solar system.
Unfortunately, only a handful of the known planets have been characterized
spectroscopically thus far, leaving a gaping void in our understanding of
planetary formation processes and planetary types. To make progress,
astronomers studying exoplanets will need new and innovative technical
solutions. Astrophotonics -- an emerging field focused on the application of
photonic technologies to observational astronomy -- provides one promising
avenue forward. In this paper we discuss various astrophotonic technologies
that could aid in the detection and subsequent characterization of planets and
in particular themes leading towards the detection of extraterrestrial life.Comment: 9 pages, 2 figures, SPIE Optics and Photonics conferenc
The MKID Exoplanet Camera for Subaru SCExAO
We present the MKID Exoplanet Camera (MEC), a z through J band (800 - 1400
nm) integral field spectrograph located behind The Subaru Coronagraphic Extreme
Adaptive Optics (SCExAO) at the Subaru Telescope on Maunakea that utilizes
Microwave Kinetic Inductance Detectors (MKIDs) as the enabling technology for
high contrast imaging. MEC is the first permanently deployed near-infrared MKID
instrument and is designed to operate both as an IFU, and as a focal plane
wavefront sensor in a multi-kHz feedback loop with SCExAO. The read noise free,
fast time domain information attainable by MKIDs allows for the direct probing
of fast speckle fluctuations that currently limit the performance of most high
contrast imaging systems on the ground and will help MEC achieve its ultimate
goal of reaching contrasts of at 2. Here we outline the
instrument details of MEC including the hardware, firmware, and data reduction
and analysis pipeline. We then discuss MEC's current on-sky performance and end
with future upgrades and plans.Comment: To be published in Publications of the Astronomical Society of the
Pacifi
Direct Imaging Explorations for Companions around Mid-Late M Stars from the Subaru/IRD Strategic Program
The Subaru telescope is currently performing a strategic program (SSP) using
the high-precision near-infrared (NIR) spectrometer IRD to search for
exoplanets around nearby mid/late-M~dwarfs via radial velocity (RV) monitoring.
As part of the observing strategy for the exoplanet survey, signatures of
massive companions such as RV trends are used to reduce the priority of those
stars. However, this RV information remains useful for studying the stellar
multiplicity of nearby M~dwarfs. To search for companions around such
``deprioritized" M~dwarfs, we observed 14 IRD-SSP targets using Keck/NIRC2
observations with pyramid wavefront sensing at NIR wavelengths, leading to high
sensitivity to substellar-mass companions within a few arcseconds. We detected
two new companions (LSPM~J1002+1459~B and LSPM~J2204+1505~B) and two new
candidates that are likely companions (LSPM~J0825+6902~B and LSPM~J1645+0444~B)
as well as one known companion. Including two known companions resolved by the
IRD fiber injection module camera, we detected seven (four new) companions at
projected separations between ~au in total. A comparison of the
colors with the spectral library suggests that LSPM~J2204+1505~B and
LSPM~J0825+6902~B are located at the boundary between late-M and early-L
spectral types. Our deep high-contrast imaging for targets where no bright
companions were resolved did not reveal any additional companion candidates.
The NIRC2 detection limits could constrain potential substellar-mass companions
() at 10~au or further. The failure with Keck/NIRC2
around the IRD-SSP stars having significant RV trends makes these objects
promising targets for further RV monitoring or deeper imaging with JWST to
search for smaller-mass companions below the NIRC2 detection limits.Comment: 16 pages, 8 figures, accepted for publication in A
Images of Embedded Jovian Planet Formation At A Wide Separation Around AB Aurigae
Direct images of protoplanets embedded in disks around infant stars provide
the key to understanding the formation of gas giant planets like Jupiter. Using
the Subaru Telescope and Hubble Space Telescope, we find evidence for a jovian
protoplanet around AB Aurigae orbiting at a wide projected separation (93 au),
likely responsible for multiple planet-induced features in the disk. Its
emission is reproducible as reprocessed radiation from an embedded protoplanet.
We also identify two structures located at 430-580 au that are candidate sites
of planet formation. These data reveal planet formation in the embedded phase
and a protoplanet discovery at wide, > 50 au separations characteristic of most
imaged exoplanets. With at least one clump-like protoplanet and multiple spiral
arms, the AB Aur system may also provide the evidence for a long-considered
alternative to the canonical model for Jupiter's formation: disk
(gravitational) instability.Comment: Author's personal version: 19 pages, 5 Figures, 1 Table; 32
Supplementary pages, 18 Supplementary Figures, 1 Supplementary Table;
Accepted for Publication in Nature Astronomy. Published version:
https://www.nature.com/articles/s41550-022-01634-