13 research outputs found
On-sky speckle nulling through a single-mode fiber with the Keck Planet Imager and Characterizer
The Keck Planet Imager and Characterizer (KPIC) is an instrument at the Keck
II telescope that enables high-resolution spectroscopy of directly imaged
exoplanets and substellar companions. KPIC uses single-mode fibers to couple
the adaptive optics system to Keck's near-infrared spectrometer (NIRSPEC).
However, KPIC's sensitivity at small separations is limited by the leakage of
stellar light into the fiber. Speckle nulling uses a deformable mirror to
destructively interfere starlight with itself, a technique typically used to
reduce stellar signal on a focal-plane imaging detector. We present the first
on-sky demonstration of speckle nulling through an optical fiber with KPIC,
using NIRSPEC to collect exposures that measure speckle phase for
quasi-real-time wavefront control while also serving as science data. We repeat
iterations of measurement and correction, each using at least 5 exposures. We
show a decrease in the on-sky leaked starlight by a factor of 2.6 to 2.8 in the
targeted spectral order, at a spatial separation of 2.0 {\lambda}/D in K-band.
This corresponds to an estimated factor of 2.6 to 2.8 decrease in the required
exposure time to reach a given SNR, relative to conventional KPIC observations.
The performance of speckle nulling is limited by instability in the speckle
phase: when the loop is opened, the null-depth degrades by a factor of 2 on the
timescale of a single phase measurement, which would limit the suppression that
can be achieved. Future work includes exploring gradient-descent methods, which
may be faster and thereby able to achieve deeper nulls. In the meantime, the
speckle nulling algorithm demonstrated in this work can be used to decrease
stellar leakage and improve the signal-to-noise of science observations.Comment: 18 pages, 4 figure
Characterizing a World Within the Hot-Neptune Desert: Transit Observations of LTT 9779 b with the Hubble Space Telescope/WFC3
We present an atmospheric analysis of LTT 9779 b, a rare planet situated in the hot-Neptune desert, that has been observed with Hubble Space Telescope (HST)/WFC3 with G102 and G141. The combined transmission spectrum, which covers 0.8–1.6 μm, shows a gradual increase in transit depth with wavelength. Our preferred atmospheric model shows evidence for H2O, CO2, and FeH with a significance of 3.1σ, 2.4σ, and 2.1σ, respectively. In an attempt to constrain the rate of atmospheric escape for this planet, we search for the 1.083 μm helium line in the G102 data but find no evidence of excess absorption that would indicate an escaping atmosphere using this tracer. We refine the orbital ephemerides of LTT 9779 b using our HST data and observations from TESS, searching for evidence of orbital decay or apsidal precession, which are not found. The phase-curve observation of LTT 9779 b with JWST NIRISS should provide deeper insights into the atmosphere of this planet and the expected atmospheric escape might be detected with further observations concentrated on other tracers such as Lyα
Characterising a World Within the Hot Neptune Desert: Transit Observations of LTT 9779 b with HST WFC3
We present an atmospheric analysis of LTT 9779 b, a rare planet situated in
the hot Neptune desert, that has been observed with HST WFC3 G102 and G141. The
combined transmission spectrum, which covers 0.8 - 1.6 m, shows a gradual
increase in transit depth with wavelength. Our preferred atmospheric model
shows evidence for HO, CO and FeH with a significance of
3.1 , 2.4 and 2.1 , respectively. In an attempt to
constrain the rate of atmospheric escape for this planet, we search for the
1.083 m Helium line in the G102 data but find no evidence of excess
absorption that would indicate an escaping atmosphere using this tracer. We
refine the orbital ephemerides of LTT 9779 b using our HST data and
observations from TESS, searching for evidence of orbital decay or apsidal
precession, which is not found. The phase-curve observation of LTT 9779 b with
JWST NIRISS should provide deeper insights into the atmosphere of this planet
and the expected atmospheric escape might be detected with further observations
concentrated on other tracers such as Lyman .Comment: Accepted for publication in A
Vortex Fiber Nulling for Exoplanet Observations: Implementation and First Light
Vortex fiber nulling (VFN) is a single-aperture interferometric technique for
detecting and characterizing exoplanets separated from their host star by less
than a diffracted beam width. VFN uses a vortex mask and single mode fiber to
selectively reject starlight while coupling off-axis planet light with a simple
optical design that can be readily implemented on existing direct imaging
instruments that can feed light to an optical fiber. With its axially symmetric
coupling region peaking within the inner working angle of conventional
coronagraphs, VFN is more efficient at detecting new companions at small
separations than conventional direct imaging, thereby increasing the yield of
on-going exoplanet search campaigns. We deployed a VFN mode operating in K band
(m) on the Keck Planet Imager and Characterizer (KPIC)
instrument at the Keck II Telescope. In this paper we present the instrument
design of this first on-sky demonstration of VFN and the results from on-sky
commissioning, including planet and star throughput measurements and predicted
flux-ratio detection limits for close-in companions. The instrument performance
is shown to be sufficient for detecting a companion times fainter than a
magnitude host star in 1 hour at a separation of 50 mas
(1.1). This makes the instrument capable of efficiently detecting
substellar companions around young stars. We also discuss several routes for
improvement that will reduce the required integration time for a detection by a
factor 3.Comment: 26 pages, 5 figures; Accepted to JATI
Twinkle -- a small satellite spectroscopy mission for the next phase of exoplanet science
With a focus on off-the-shelf components, Twinkle is the first in a series of
cost competitive small satellites managed and financed by Blue Skies Space Ltd.
The satellite is based on a high-heritage Airbus platform that will carry a
0.45 m telescope and a spectrometer which will provide simultaneous wavelength
coverage from 0.5-4.5 . The spacecraft prime is Airbus Stevenage
while the telescope is being developed by Airbus Toulouse and the spectrometer
by ABB Canada. Scheduled to begin scientific operations in 2025, Twinkle will
sit in a thermally-stable, sun-synchronous, low-Earth orbit. The mission has a
designed operation lifetime of at least seven years and, during the first three
years of operation, will conduct two large-scale survey programmes: one focused
on Solar System objects and the other dedicated to extrasolar targets. Here we
present an overview of the architecture of the mission, refinements in the
design approach, and some of the key science themes of the extrasolar survey.Comment: Presented at SPIE Astronomical Telescopes & Instrumentation 202
Detecting Biosignatures in the Atmospheres of Gas Dwarfs Planets with the James Webb Space Telescope
Mathematical and Physical Sciences: 3rd Place (The Ohio State University Edward F. Hayes Graduate Research Forum)A one-year embargo was granted for this item
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2MASS J04435750+3723031 B : a young companion at the substellar boundary with potential membership in the [beta] Pictoris moving group
We present a detailed characterization of 2MASS J04435750+3723031 B, a low-mass companion orbiting an M2 star at 7.6" (550 AU) with potential membership in the 23 Myr β Pictoris moving group. Using near-infrared spectroscopy of the companion from IRTF/SpeX we have found a spectral type of M6 ± 1 and indications of youth through age-sensitive absorption lines and a low surface gravity index (VL-G). A young age is supported by Hα emission and lithium absorption in the host star. A comparison to atmospheric models reveals an effective temperature of 2800 ± 100 K with a low surface gravity of 4.0 ± 0.5 dex for the companion. This system has been previously proposed as a member of the β Pictoris moving group. Here we re-evaluate the membership of this system and find that it is a marginally consistent kinematic match to the β Pictoris moving group using Gaia parallaxes and new radial velocities for the host and companion. If this object does belong to the β Pictoris moving group, it would be a kinematic outlier and the companion would be over--luminous compared to other similar ultracool objects like PZ Tel B; this would suggest 2M0443+3723 B could be a close brown dwarf binary, and would make it the sixth substellar companion in this group. If 2M0443+3723 AB does not belong to any moving group then its age is more uncertain. In this case it is still young (< 30 Myr), and the implied mass would be between ~ 30--110 M [subscript Jup]. To test this hypothesis, we acquired NIR AO images with Keck II/NIRC2, but they do not reveal a binary to the companion that is resolvable down to the diffraction limit of ~ 3 AUAstronom
Caring for Children With Life-Threatening Illnesses: Impact on White, African American, and Latino Families
Characterising a World Within the Hot Neptune Desert: Transit Observations of LTT 9779 b with HST WFC3
We present an atmospheric analysis of LTT 9779 b, a rare planet situated in the hot Neptune desert, that has been observed with HST WFC3 G102 and G141. The combined transmission spectrum, which covers 0.8 - 1.6 μm, shows a gradual increase in transit depth with wavelength. Our preferred atmospheric model shows evidence for H2O, CO2 and FeH with a significance of 3.1 σ, 2.4 σ and 2.1 σ, respectively. In an attempt to constrain the rate of atmospheric escape for this planet, we search for the 1.083 μm Helium line in the G102 data but find no evidence of excess absorption that would indicate an escaping atmosphere using this tracer. We refine the orbital ephemerides of LTT 9779 b using our HST data and observations from TESS, searching for evidence of orbital decay or apsidal precession, which is not found. The phase-curve observation of LTT 9779 b with JWST NIRISS should provide deeper insights into the atmosphere of this planet and the expected atmospheric escape might be detected with further observations concentrated on other tracers such as Lyman α