arXiv subjects

Emily K. Deibert

Publications and source records attributed to Emily K. Deibert.

11 recordsLinked to original sources

arXiv2026

High-Resolution Dayside Spectroscopy of the Ultra-Hot Jupiter WASP-178b with GHOST/Gemini South

We present high-resolution dayside spectroscopy of the ultra-hot Jupiter WASP-178b obtained with the Gemini High-resolution Optical SpecTrograph (GHOST) at the Gemini South Observatory. The observations cover pre- and post-eclipse orbital phases, lasting approximately 9 hours in total, and represent the first published high-resolution optical dayside emission spectroscopy of WASP-178b's atmosphere, complementing previous near-infrared dayside spectroscopy. We verify the presence of a thermal inversion in the dayside atmosphere with a high-significance (8.3$σ$) detection of neutral iron emission via the Doppler cross-correlation technique, alongside hints of neutral Si and Ca emission. We also carry out model injection/recovery tests for other atmospheric species, which indicate that we do not expect to detect the majority of species searched for in this work, assuming our models are accurate representations of the planet's atmosphere. Finally, we place our results into context with previous work, showing how our tentative detection of neutral Si complements existing space-based observations and adds a new data point to previous detections of Si in ultra-hot Jupiter atmospheres. Our high-resolution observations provide important context about the dayside of WASP-178b, shedding light on 3D atmospheric processes and the extreme conditions present in ultra-hot Jupiter atmospheres.

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arXiv2026

TESS Photometry and Radial Velocity Analysis of the sub-Neptune Exoplanet π Mensae c and the Wider π Mensae Planetary System

Exoplanet characterization relies on precise measurements of planetary orbital and physical parameters. This is particularly important for planetary dynamics and atmospheric evolution, as orbital parameters help constrain system evolution, resolve ambiguities, and gauge atmospheric retention. The first exoplanet discovered by the Transiting Exoplanet Survey Satellite (TESS), $π$ Men c, is a warm sub-Neptune orbiting a bright Sun-like star in a system containing (at least) one other planet with a wildly different period and size. Lying near the 1.5-2.0 $R_{\oplus}$ radius gap, $π$ Men c is expected to have lost its primordial hydrogen and helium, but kept heavier compounds like H$_2$O and CO$_2$. The $π$ Men system is well observed with decades of radial velocity measurements, and TESS has continued to observe $π$ Men c, yielding six years and 21 sectors of photometry. We present a comprehensive analysis of these TESS data and 22 years of radial velocity measurements to provide updated orbital ephemerides for $π$ Men b, c, and the proposed third planet, $π$ Men d. Our newly derived $π$ Men c period error margins are an order of magnitude improved from previous estimates, and we estimate the mass range of $π$ Men d to be 13.4 $\leq$ M$_d$ $<$ 20 M$_{\oplus}$. We find that $π$ Men c is a uniquely interesting target for future transmission spectroscopy studies with JWST, and that existing radial velocity data are consistent with the existence of a third planet.

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arXiv2026

The Roasting Marshmallows Program with IGRINS on Gemini South V: Atmosphere of MASCARA-1b is Enriched in Refractory Elements

Ultra-hot Jupiters (UHJs; $T_{\rm eq} \gtrsim 2000$ K) enable simultaneous detection of volatile (ice-forming) and refractory (rock-forming) species in planetary atmospheres, providing a powerful diagnostic of planet formation and atmospheric processing. We present a comprehensive high-resolution cross-correlation spectroscopy (HRCCS) analysis of the UHJ MASCARA-1b ($T_{\rm eq} \approx 2600$ K) using the IGRINS and IGRINS-2 spectrographs. We detect robust (SNR$>$4) signals from H$_2$O, CO, OH, Fe I, Mg I, Ca I, and Ti I, marking the most complete atmospheric inventory of MASCARA-1b to date. Using a chemically consistent atmospheric inference framework, we constrain elemental abundances to a typical precision of $\approx$0.2 dex, retrieving a solar atmospheric metallicity ([M/H]$_\odot$ $= 0.07^{+0.17}_{-0.13}$ $\approx 1.2\times$ solar), a C/O ratio (C/O $= 0.65^{+0.08}_{-0.08}$) consistent with solar value (C/O $=$ 0.59), an enhanced refractory abundance ([R/H]$_\odot$ $= 0.40^{+0.23}_{-0.17} \approx 2.5\times$ solar; $\approx 3.8\times$ stellar), and a moderately super-solar refractory-to-volatile ratio ([R/V]$_\odot$ $= 0.36^{+0.11}_{-0.09}$ $\approx 2.3\times$ solar). Comparison with formation models suggests that MASCARA-1b most likely accreted material between the soot-H$_2$O or H$_2$O-CO snowlines (at 68$\%$ confidence). We additionally find stellar values for atmospheric Ti/Mg and Ca/Mg ratios (at 68$\%$ confidence). The Mg/Fe is also found to be consistent with stellar value at 95$\%$ confidence. Therefore, we do not find strong indication of nightside cold trapping in MASCARA-1b. As homogeneous refractory-to-volatile measurements expand across the UHJ population, particularly with upcoming Extremely Large Telescopes, these diagnostics will enable statistically robust tests of emerging trends in giant planet formation and atmospheric evolution.

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arXiv2025

ExoGemS The Effect of Offsets from True Orbital Parameters on Exoplanet High-Resolution Transmission Spectra

High-resolution spectroscopy (HRS) plays a crucial role in characterizing exoplanet atmospheres, revealing detailed information about their chemical composition, temperatures, and dynamics. However, inaccuracies in orbital parameters can affect the result of HRS analyses. In this paper, we simulated HRS observations of an exoplanet's transit to model the effects of an offset in transit midpoint or eccentricity on the resulting spectra. We derived analytical equations to relate an offset in transit midpoint or eccentricity to shifted velocities, and compared it with velocities measured from simulated HRS observations. Additionally, we compared velocity shifts in the spectrum of the ultra-hot Jupiter WASP-76b using previously reported and newly measured transit times. We found that transit midpoint offsets on the order of minutes, combined with eccentricity offsets of approximately $0.1$, lead to significant shifts in velocities, yielding measurements on the order of several kilometers per second. Thus, such uncertainties could conflate derived wind measurements.

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arXiv2025

A Time-Resolved High-Resolution Spectroscopic Analysis of Ionized Calcium and Dynamical Processes in the Ultra-Hot Jupiter HAT-P-70 b

We present the first transmission spectroscopy study of an exoplanet atmosphere with the high-resolution mode of the new Gemini High-resolution Optical SpecTrograph (GHOST) instrument at the Gemini South Observatory. We observed one transit of HAT-P-70 b - an ultra-hot Jupiter with an inflated radius - and made a new detection of the infrared Ca II triplet in its transmission spectrum. The depth of the strongest line implies that a substantial amount of Ca II extends to at least 47% above the bulk planetary radius. The triplet lines are blueshifted between ~ 3 to 5 km/s, indicative of strong dayside-to-nightside winds common on highly irradiated gas giants. Comparing the transmission spectrum with atmospheric models that incorporate non-local thermodynamic equilibrium effects suggests that the planetary mass is likely between 1 to 2 $M_{\rm J}$, much lighter than the upper limit previously derived from radial velocity measurements. Importantly, thanks to the the high signal-to-noise ratio achieved by GHOST/Gemini South, we are able to measure the temporal variation of these signals. Absorption depths and velocity offsets of the individual Ca II lines remain mostly consistent across the transit, except for the egress phases, where weaker absorption and stronger blueshifts are observed, highlighting the atmospheric processes within the trailing limb alone. Our study demonstrates the ability of GHOST to make time-resolved detections of individual spectral lines, providing valuable insights into the 3D nature of exoplanet atmospheres by probing different planetary longitudes as the tidally locked planet rotates during the transit.

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arXiv2024

High-Resolution Dayside Spectroscopy of WASP-189b: Detection of Iron during the GHOST/Gemini South System Verification Run

With high equilibrium temperatures and tidally locked rotation, ultra-hot Jupiters (UHJs) are unique laboratories within which to probe extreme atmospheric physics and chemistry. In this paper, we present high-resolution dayside spectroscopy of the UHJ WASP-189b obtained with the new Gemini High-resolution Optical SpecTrograph (GHOST) at the Gemini South Observatory. The observations, which cover three hours of post-eclipse orbital phases, were obtained during the instrument's System Verification run. We detect the planet's atmosphere via the Doppler cross-correlation technique, and recover a detection of neutral iron in the planet's dayside atmosphere at a significance of 7.5$σ$ in the red-arm of the data, verifying the presence of a thermal inversion. We also investigate the presence of other species in the atmosphere and discuss the implications of model injection/recovery tests. These results represent the first atmospheric characterization of an exoplanet with GHOST's high-resolution mode, and demonstrate the potential of this new instrument in detecting and studying ultra-hot exoplanet atmospheres.

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arXiv2023

ExoGemS High-Resolution Transmission Spectroscopy of WASP-76b with GRACES

We present high-resolution transmission spectroscopy of WASP-76b with GRACES/Gemini North obtained as part of the ExoGemS survey. With a broad spectral range of 400-1050 nm and a relatively high resolution of ~66,000, these observations are particularly well-suited to searching for atomic and molecular atmospheric species via the Doppler cross-correlation technique. We recover absorption features due to neutral iron (Fe I), sodium (Na I), and ionized calcium (Ca II) at high significance (>5$σ$), and investigate possible atmospheric temperatures and wind speeds. We also report tentative (>3$σ$) detections of Li I, K I, Cr I, and V I in the atmosphere of WASP-76b. Finally, we report non-detections of a number of other species, some of which have previously been detected with other instruments. Through model injection/recovery tests, we demonstrate that many of these species are not expected to be detected in our observations. These results allow us to place GRACES and the ExoGemS survey in context with other high-resolution optical spectrographs.

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arXiv2021

Detection of Ionized Calcium in the Atmosphere of the Ultra-Hot Jupiter WASP-76b

Recent observations of the ultra-hot Jupiter WASP-76b have revealed a diversity of atmospheric species. Here we present new high-resolution transit spectroscopy of WASP-76b with GRACES at the Gemini North Observatory, serving as a baseline for the Large and Long Program "Exploring the Diversity of Exoplanet Atmospheres at High Spectral Resolution" (Exoplanets with Gemini Spectroscopy, or ExoGemS for short). With a broad spectral range of $400 - 1050$ nm, these observations allow us to search for a suite of atomic species. We recover absorption features due to neutral sodium (Na I), and report a new detection of the ionized calcium (Ca II) triplet at ~ $850$ nm in the atmosphere of WASP-76b, complementing a previous detection of the Ca II H & K lines. The triplet has line depths of $0.295 \pm 0.034$% at ~ $849.2$ nm, $0.574 \pm 0.041$% at ~ $854.2$ nm, and $0.454 \pm 0.024$% at ~ $866.2$ nm, corresponding to effective radii close to (but within) the planet's Roche radius. These measured line depths are significantly larger than those predicted by model LTE and NLTE spectra obtained on the basis of a pressure-temperature profile computed assuming radiative equilibrium. The discrepancy suggests that the layers probed by our observations are either significantly hotter than predicted by radiative equilibrium and/or in a hydrodynamic state. Our results shed light on the exotic atmosphere of this ultra-hot world, and will inform future analyses from the ExoGemS survey.

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arXiv2021

A Near-Infrared Chemical Inventory of the Atmosphere of 55 Cancri e

We present high-resolution near-infrared spectra taken during eight transits of 55 Cancri e, a nearby low-density super-Earth with a short orbital period (< 18 hours). While this exoplanet's bulk density indicates a possible atmosphere, one has not been detected definitively. Our analysis relies on the Doppler cross-correlation technique, which takes advantage of the high spectral resolution and broad wavelength coverage of our data, to search for the thousands of absorption features from hydrogen-, carbon-, and nitrogen-rich molecular species in the planetary atmosphere. Although we are unable to detect an atmosphere around 55 Cancri e, we do place strong constraints on the levels of HCN, NH${}_3$, and C${}_2$H${}_2$ that may be present. In particular, at a mean molecular weight of 5 amu we can rule out the presence of HCN in the atmosphere down to a volume mixing ratio (VMR) of 0.02%, NH${}_3$ down to a VMR of 0.08%, and C${}_2$H${}_2$ down to a VMR of 1.0%. If the mean molecular weight is relaxed to 2 amu, we can rule out the presence of HCN, NH${}_3$, and C${}_2$H${}_2$ down to VMRs of 0.001%, 0.0025%, and 0.08% respectively. Our results reduce the parameter space of possible atmospheres consistent with the analysis of HST/WFC3 observations by Tsiaras et al. (2016), and indicate that if 55 Cancri e harbors an atmosphere, it must have a high mean molecular weight and/or clouds.

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arXiv2020

Arid or Cloudy: Characterizing the Atmosphere of the super-Earth 55 Cancri e using High-Resolution Spectroscopy

The nearby super-Earth 55 Cnc e orbits a bright (V = 5.95 mag) star with a period of ~ 18 hours and a mass of ~ 8 Earth masses. Its atmosphere may be water-rich and have a large scale-height, though attempts to characterize it have yielded ambiguous results. Here we present a sensitive search for water and TiO in its atmosphere at high spectral resolution using the Gemini North telescope and the GRACES spectrograph. We combine observations with previous observations from Subaru and CFHT, improving the constraints on the presence of water vapor. We adopt parametric models with an updated planet radius based on recent measurements, and use a cross-correlation technique to maximize sensitivity. Our results are consistent with atmospheres that are cloudy or contain minimal amounts of water and TiO. Using these parametric models, we rule out a water-rich atmosphere (VMR >= 0.1%) with a mean molecular weight of <= 15 g/mol at a 3 sigma confidence level, improving on the previous limit by a significant margin. For TiO, we rule out a mean molecular weight of <= 5 g/mol with a 3 sigma confidence level for a VMR greater than 10^-8; for a VMR of greater than 10^-7, the limit rises to a mean molecular weight of <= 10 g/mol. We can rule out low mean-molecular-weight chemical equilibrium models both including and excluding TiO/VO at very high confidence levels (> 10 sigma). Overall, our results are consistent with an atmosphere with a high mean molecular weight and/or clouds, or no atmosphere.

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arXiv2018

High-Resolution Transit Spectroscopy of Warm Saturns

We present high-resolution optical transmission spectroscopy of two sub-Saturn mass transiting exoplanets, HAT-P-12b and WASP-69b. With relatively low densities and high atmospheric scale heights, these planets are particularly well-suited to characterization through transit spectroscopy, and serve as ideal candidates for extending previously-tested methods to lower planetary masses. Using a single transit for each planet, we take advantage of the Doppler cross-correlation technique to search for sodium, potassium, and water absorption features. Our analysis reveals a likely ($3.2σ$) detection of sodium absorption features in the atmosphere of HAT-P-12b, and enables us to place constraints on the presence of alkaline and molecular species in the atmospheres of both planets. With our results, we highlight the efficacy of ground-based campaigns for characterizing exoplanetary atmospheres, and pave the way for future analyses of low-mass planets.

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