Natalie H. Allen
A5036911281- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Atmospheric Ozone and Climate
- Astronomical Observations and Instrumentation
- Spectroscopy and Laser Applications
- Astrophysics and Star Formation Studies
- Adaptive optics and wavefront sensing
- Planetary Science and Exploration
- Space Exploration and Technology
- Meteorological Phenomena and Simulations
- Geophysics and Gravity Measurements
- Cosmology and Gravitation Theories
- Gamma-ray bursts and supernovae
- Methane Hydrates and Related Phenomena
- Geological Modeling and Analysis
- Spacecraft and Cryogenic Technologies
- Calibration and Measurement Techniques
- Laser-induced spectroscopy and plasma
- Solar and Space Plasma Dynamics
- Geochemistry and Geologic Mapping
- Spacecraft Design and Technology
- Geology and Paleoclimatology Research
Astronomy and Space
2025
Johns Hopkins University
2022-2024
University of Rochester
2022
Transmission spectroscopy1-3 of exoplanets has revealed signatures water vapour, aerosols and alkali metals in a few dozen exoplanet atmospheres4,5. However, these previous inferences with the Hubble Spitzer Space Telescopes were hindered by observations' relatively narrow wavelength range spectral resolving power, which precluded unambiguous identification other chemical species-in particular primary carbon-bearing molecules6,7. Here we report broad-wavelength 0.5-5.5 µm atmospheric...
Measuring the abundances of carbon and oxygen in exoplanet atmospheres is considered a crucial avenue for unlocking formation evolution exoplanetary systems. Access to an exoplanet's chemical inventory requires high-precision observations, often inferred from individual molecular detections with low-resolution space-based high-resolution ground-based facilities. Here we report medium-resolution (R$\sim$600) transmission spectrum atmosphere between 3-5 $\mu$m covering multiple absorption...
Abstract Carbon dioxide (CO 2 ) is a key chemical species that found in wide range of planetary atmospheres. In the context exoplanets, CO an indicator metal enrichment (that is, elements heavier than helium, also called ‘metallicity’) 1–3 , and thus formation processes primary atmospheres hot gas giants 4–6 . It one most promising to detect secondary terrestrial exoplanets 7–9 Previous photometric measurements transiting planets with Spitzer Space Telescope have given hints presence but not...
Transmission spectroscopy provides insight into the atmospheric properties and consequently formation history, physics, chemistry of transiting exoplanets. However, obtaining precise inferences from transmission spectra requires simultaneously measuring strength shape multiple spectral absorption features a wide range chemical species. This has been challenging given precision wavelength coverage previous observatories. Here, we present spectrum Saturn-mass exoplanet WASP-39b obtained using...
Abstract Measuring the metallicity and carbon-to-oxygen (C/O) ratio in exoplanet atmospheres is a fundamental step towards constraining dominant chemical processes at work and, if equilibrium, revealing planet formation histories. Transmission spectroscopy (for example, refs. 1,2 ) provides necessary means by abundances of oxygen- carbon-bearing species; however, this requires broad wavelength coverage, moderate spectral resolution high precision, which, together, are not achievable with...
Abstract Clouds are prevalent in many of the exoplanet atmospheres that have been observed to date. For transiting exoplanets, we know if clouds present because they mute spectral features and cause wavelength-dependent scattering. While exact composition these is largely unknown, this information vital understanding chemistry energy budget planetary atmospheres. In work, observe one transit hot Jupiter WASP-17b with JWST’s Mid-Infrared Instrument Low Resolution Spectrometer generate a...
Abstract The JWST NIRSpec integral field unit (IFU) presents a unique opportunity to observe directly imaged exoplanets from 3 5 μ m at moderate spectral resolution ( R ∼ 2700) and thereby better constrain the composition, disequilibrium chemistry, cloud properties of their atmospheres. In this work, we present first IFU high-contrast observations substellar companion that requires starlight suppression techniques. We develop specific data-reduction strategies study faint companions around...
Abstract We present the first emission spectrum of hot Jupiter WASP-17 b using one eclipse observation from JWST Near Infrared Imager and Slitless Spectrograph (NIRISS) Single Object Spectroscopy (SOSS) mode. Covering a wavelength range 0.6–2.8 μ m, our retrieval analysis reveals strong detection H 2 O in b’s dayside atmosphere (6.4 σ ). Our retrievals consistently favor supersolar abundance noninverted temperature–pressure profile over large pressure range. Additionally, examination...
Abstract We develop and disseminate effective point-spread functions geometric-distortion solutions for high-precision astrometry photometry with the JWST NIRISS instrument. correct field dependencies detector effects, assess quality temporal stability of calibrations. As a scientific application validation, we study proper motion (PM) kinematics stars in calibration near Large Magellanic Cloud (LMC) center, comparing to first-epoch Hubble Space Telescope (HST) archival catalog 16 yr...
Detecting atmospheres around planets with a radius below 1.6 R$_{\oplus}$, commonly referred to as rocky (Rogers_2015, Rogers_2021), has proven be challenging. However, orbiting M-dwarfs are ideal candidates due their favorable planet-to-star ratio. Here, we present one transit observation of the Super-Earth L98-59d (1.58 2.31 M$_{\oplus}$), at limit rocky/gas-rich, using JWST NIRSpec G395H mode covering 2.8 5.1 microns wavelength range. The extracted spectrum from single deviates flat line...
L 98-59 d is a Super-Earth planet orbiting an M-type star. We performed retrievals on the transmission spectrum of obtained using NIRSpec G395H during single transit, from JWST Cycle 1 GTO 1224. The wavelength range this allows us to detect presence several atmospheric species. found that consistent with high mean molecular weight atmosphere. indicates possible sulfur-bearing species H$_2$S and SO$_2$, which could hint at active volcanism if verified by future observations. also tested for...
Abstract Water has proven to be ubiquitously detected in near-infrared (NIR) transmission spectroscopy observations of hot Jupiter atmospheres, including WASP-17b. However, previous analyses WASP-17b’s atmosphere based upon Hubble Space Telescope (HST) and Spitzer data could not constrain the water abundance, finding that subsolar, supersolar, bimodal posterior distributions were all statistically valid. In this work, we observe one transit WASP-17b using JWST’s Near Infrared Imager Slitless...
Abstract Which rocky exoplanets have atmospheres? This presumably simple question is the first that must be answered to understand prevalence of nearby habitable planets. A mere 6.9 pc from Earth, LTT 1445A closest transiting M dwarf system, and its largest known planet, at 1.31 R ⊕ 424 K, one most promising targets in which search for an atmosphere. We use Hubble Space Telescope/Wide Field Camera 3 transmission spectroscopy with G280 G141 grisms study spectrum 1445Ab between 0.2 1.65 μ m....
Abstract We present a new and extended transmission spectrum of the warm Neptune HAT-P-26b spanning wavelengths between 0.29 5.0 μ m. This is derived from HST STIS G430L observations PanCET program, reanalysis previously published G750L data, along with WFC3 IR G102 G141 two Spitzer IRAC photometric points at 3.6 4.5 this analysis as part Sculpting Hubble’s Exoplanet Legacy where goals are to analyze all archival transiting exoplanets using uniform homogeneous reduction technique. With...
Abstract We present the first spectroscopic characterization of dayside atmosphere WASP-17b in mid-infrared using a single JWST MIRI/LRS eclipse observation. From forward-model fits to 5–12 μ m emission spectrum, we tightly constrain heat redistribution factor be 0.92 ± 0.02 at pressures probed by this data, indicative inefficient global redistribution. also marginally detect supersolar abundance water, consistent with previous findings for WASP-17b, but note our weak constraints on...
One of the strongest ${\rm Na~I}$ features was observed in WASP-96b. To confirm this novel detection, we provide a new 475-825nm transmission spectrum obtained with Magellan/IMACS, which indeed confirms presence broad sodium absorption feature. We find same result when reanalyzing 400-825nm VLT/FORS2 data. also utilize synthetic data to test effectiveness two common detrending techniques: (1) Gaussian processes (GP) routine, and (2) common-mode correction followed by polynomial (CMC+Poly)....
Carbon dioxide (CO2) is a key chemical species that found in wide range of planetary atmospheres. In the context exoplanets, CO2 an indicator metal enrichment (i.e., elements heavier than helium, also called "metallicity"), and thus formation processes primary atmospheres hot gas giants. It one most promising to detect secondary terrestrial exoplanets. Previous photometric measurements transiting planets with Spitzer Space Telescope have given hints presence but not yielded definitive...
Abstract The Vredefort impact structure, located in South Africa and formed 2.02 Ga, is the largest confirmed remnant crater on Earth. widely accepted impactor diameter velocity to form this are 15 km km/s, respectively, which produce a of 172 km. This much smaller than most commonly cited estimates (250–280 km), while previous results were able match geologic evidence known at that time, these parameters not consistent with more recent geological constraints. Here, we conduct simulations...
Abstract The Hubble Space Telescope (HST) has been our most prolific tool to study exoplanet atmospheres. As the age of JWST begins, there are a wealth HST archival data that useful strengthen inferences from JWST. Notably, HST/Space Imaging Spectrograph (STIS), with its 0.3–1 μ m wavelength coverage, extends past JWST’s 0.6 cutoff and holds an abundance potential information: alkali (Na, K) molecular (TiO, VO) species opacities, aerosol information, presence stellar contamination. However,...
M dwarf systems offer a unique opportunity to study terrestrial exoplanetary atmospheres due their smaller size and cooler temperatures. However, the extreme conditions these host stars impose, it is unclear whether small, close-in rocky planets are able retain any atmosphere at all. The Hot Rocks Survey aims answer this question by targeting nine different spanning range of planetary stellar properties. LHS 1478 b orbits an M3-type star, has equilibrium temperature Teq = 585 K experiences...
Abstract We present a precise ground-based optical transmission spectrum of the hot Saturn HATS-5b ( T eq = 1025 K), obtained as part ACCESS survey with IMACS multi-object spectrograph mounted on Magellan Baade Telescope. Our spectra cover 0.5–0.9 μ m region and are product five individual transits observed between 2014 2018. introduce usage additional second-order light in our analyses, which allows us to extract an “extra” transit curve, improving overall precision combined spectrum. find...
Abstract We present new optical transmission spectra for two hot Jupiters: WASP-25b ( M = 0.56 J ; R 1.23 P 3.76 days) and WASP-124b 0.58 1.34 3.37 days), with wavelength coverages of 4200–9100 Å 4570–9940 Å, respectively. These are from the ESO Faint Object Spectrograph Camera (v.2) mounted on New Technology Telescope Inamori-Magellan Areal & Magellan Baade. No strong spectral features were found in either spectra, data probing 4 6 scale heights, Exoretrievals PLATON retrievals favor...
The JWST NIRSpec integral field unit (IFU) presents a unique opportunity to observe directly imaged exoplanets from 3-5um at moderate spectral resolution (R~2,700) and thereby better constrain the composition, disequilibrium chemistry, cloud properties of their atmospheres. In this work, we present first IFU high-contrast observations substellar companion that requires starlight suppression techniques. We develop specific data reduction strategies study faint companions around bright stars,...
Measuring the abundances of carbon and oxygen in exoplanet atmospheres is considered a crucial avenue for unlocking formation evolution exoplanetary systems. Access to an exoplanet's chemical inventory requires high-precision observations, often inferred from individual molecular detections with low-resolution space-based high-resolution ground-based facilities. Here we report medium-resolution (R$\sim$600) transmission spectrum atmosphere between 3-5 $μ$m covering multiple absorption...