arXiv subjects

Jessica Birky

Publications and source records attributed to Jessica Birky.

11 recordsLinked to original sources

arXiv2026

The Range of Cumulative XUV Flux on GJ 1132 b

We investigate the plausible history of the XUV luminosity evolution of the planet-hosting M4 star GJ 1132 (~0.2 solar masses) to infer the cumulative incident XUV flux intercepted by the short-period (~1.6 d) Earth-sized transiting planet GJ 1132 b. We include the dominant observational uncertainties, compare two quiescent XUV luminosity evolution models, and simulate the XUV luminosity evolution from flares based on TESS data and a re-analysis of Kepler stars. We find only 4 flares in GJ 1132's TESS 123 day lightcurve, which is relatively few for M dwarfs and, in conjunction with the ~125 day period, suggests that this star is many Gyr old. We find that all model permutations predict that the planet has at least a 95% chance of receiving more than 50 times as much XUV flux as modern Earth, confirming that this planet is a good candidate for permanent atmospheric loss. We also find that an empirical XUV model for M dwarfs predicts 2-3 times more total XUV flux than a commonly used solar twin model and that the empirical model's distribution is 2-3 times narrower. Flares contribute about 20% of the cumulative XUV flux on planet b, which, while modest, ensures the planet lies firmly on the atmosphere-free side of the "cosmic shoreline."

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arXiv2026

ALABI: Active Learning for Accelerated Bayesian Inference

We present Active Learning for Accelerated Bayesian Inference (\texttt{alabi}): an open-source Python package for performing Bayesian inference with computationally expensive models. Given a forward model and observational data to construct a likelihood and priors, \texttt{alabi}\ uses a Gaussian Process (GP) surrogate model trained to predict posterior probability as a function of input parameters, and employs active learning to iteratively improve GP predictive performance in high-likelihood regions where the GP is most uncertain. \texttt{alabi}\ provides a uniform interface for using Markov chain Monte Carlo (MCMC) with different packages, including the affine-invariant sampler \texttt{emcee}, and nested samplers \texttt{dynesty}, \texttt{multinest}, and \texttt{ultranest}. This approach facilitates accurate estimation of the desired posterior distribution, while reducing the number of computationally expensive model evaluations required by factors of thousands. We demonstrate the performance of \texttt{alabi}\ on a variety of test cases, including where inference is challenging due to complex posterior structure or high dimensionality. We show that \texttt{alabi}\ offers a substantial improvement for likelihood functions with evaluation times $\gtrsim 1$\,s, speeding up MCMC computations by a factor of $10-1000\times$ when tested on problems with up to 64 dimensions.

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arXiv2025

Automated Spectroscopic Wavelength Calibration using Dynamic Time Warping

Here we present an automated method for obtaining wavelength calibrations for one-dimensional spectra, using Dynamic Time Warping (DTW). DTW is a flexible and well-understood algorithm for pattern matching, which has not been widely used in astronomy data analysis. Employing a calibrated template spectrum as a reference, DTW can recover non-linear and even discontinuous dispersion solutions without an initial guess. The algorithm is robust against differing spectral resolution between the template and sample data, and can accommodate some spurious or missing features. We demonstrate the effectiveness of DTW in an automated data reduction workflow, using both simulated and real arc lamp spectra in a Python data reduction framework. Finally, we provide a discussion on the utility and best practices with the DTW algorithm for wavelength calibration. We also introduce the PyKOSMOS data reduction toolkit, which includes our DTW calibration methods.

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arXiv2025

Prospects of Constraining Equilibrium Tides in Low-Mass Binary Stars

The dynamical evolution of short-period low-mass binary stars (with mass $M < 1.5M_{\odot}$, from formation to the late main-sequence, and with orbital periods less than $\sim$10 days) is strongly influenced by tidal dissipation. This process drives orbital and rotational evolution that ultimately results in circularized orbits and rotational frequencies synchronized with the orbital frequency. Despite the fundamental role of tidal dissipation in binary evolution, constraining its magnitude of (typically parameterized by the tidal quality factor $\mathcal{Q}$) has remained discrepant by orders of magnitude in the existing literature. Recent observational constraints from time-series photometry (e.g., Kepler, K2, TESS), as well as advances in theoretical models to incorporate a more realistic gravitational response within stellar interiors, are invigorating new optimism for resolving this long-standing problem. To investigate the prospects and limitations of constraining tidal $\mathcal{Q}$, we use global sensitivity analysis and simulation based inference to examine how the initial conditions and tidal $\mathcal{Q}$ influence the observable orbital and rotational states. Our results show that even under the simplest and most tractable models of tides, the path towards inferring $\mathcal{Q}$ from individual systems is severely hampered by inherent degeneracies between tidal $\mathcal{Q}$ and the initial conditions, even when considering the strongest possible constraints (i.e., binaries with precise masses, ages, orbital periods, eccentricities, and rotation periods). Finally as an alternative, we discuss how population synthesis approaches may be a more promising path forward for validating tidal theories.

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arXiv2025

Tidal Synchronization of TESS Eclipsing Binaries

Tidal synchronization plays a fundamental role in the evolution of binary star systems. However, key details such as the timescale of synchronization, efficiency of tidal dissipation, rotational period, and dependence on stellar mass are not well constrained. We present a catalog of rotation periods, orbital periods, and eccentricities from eclipsing binaries (EBs) that can be used to study the role of tides in the rotational evolution of low-mass dwarf (FGKM spectral type) binaries. This study presents the largest catalog of EB orbital and rotational periods (Porb and Prot) measured from the Transiting Exoplanet Satellite Survey (TESS). We first classify 4584 light curves from the TESS Eclipsing Binary Catalog according to out-of-eclipse stellar variability type: starspot modulation, ellipsoidal variability, non-periodic variability, and "other" variability (e.g. pulsations). We then manually validate each light curve classification, resulting in a sample of 1039 candidates with 584 high-confidence EBs that exhibit detectable star-spot modulation. From there, we measure and compare the rotation period of each starspot-modulated EB using three methods: Lomb-Scargle periodograms, autocorrelation function, and phase dispersion minimization. We find that our period distributions are consistent with previous work that used a sample of 816 starspot EBs from Kepler to identify two populations: a synchronous population (with Porb~Prot) and a subsynchronous population (with 8Porb~7Prot). Using Bayesian model comparison, we find that a bimodal distribution is a significantly better fit than a unimodal distribution for Kepler and TESS samples, both individually or combined, confirming that the subsynchronous population is statistically significant.

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arXiv2024

History and Habitability of the LP 890-9 Planetary System

We present numerous aspects of the evolution of the LP 890-9 (SPECULOOS-2/TOI-4306) planetary system, focusing on the likelihood that planet c can support life. We find that the host star reaches the main sequence in 1 Gyr and that planet c lies close to the inner boundary of the habitable zone. We find the magma ocean stage can last up to 50 Myr, remove 8 Earth-oceans of water, and leave up to 2000 bars of oxygen in the atmosphere. However, if the planet forms with a hydrogen envelope as small as 0.1 Earth-masses, no water will be lost during the star's pre-main sequence phase from thermal escape processes. We find that the planets are unlikely to be in a 3:1 mean motion resonance and that both planets tidally circularize within 0.5 Gyr when tidal dissipation is held constant. However, if tidal dissipation is a function of mantle temperature and rheology, then we find that planet c's orbit may require more than 7 Gyr to circularize, during which time tidal heating may reach hundreds of terawatts. We thus conclude that the habitability of planet c depends most strongly on the initial volatile content and internal properties, but no data yet preclude the viability of an active biosphere on the planet.

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arXiv2024

The Implications of Thermal Hydrodynamic Atmospheric Escape on the TRAPPIST-1 Planets

JWST observations of the 7-planet TRAPPIST-1 system will provide an excellent opportunity to test outcomes of stellar-driven evolution of terrestrial planetary atmospheres, including atmospheric escape, ocean loss and abiotic oxygen production. While most previous studies use a single luminosity evolution for the host star, we incorporate observational uncertainties in stellar mass, luminosity evolution, system age, and planetary parameters to statistically explore the plausible range of planetary atmospheric escape outcomes. We present probabilistic distributions of total water loss and oxygen production as a function of initial water content, for planets with initially pure water atmospheres and no interior-atmosphere exchange. We find that the interior planets are desiccated for initial water contents below 50 Earth oceans. For TRAPPIST-1e, f, g, and h, we report maximum water loss ranges of 8.0$^{+1.3}_{-0.9}$, 4.8$^{+0.6}_{-0.4}$, 3.4$^{+0.3}_{-0.3}$, and 0.8$^{+0.2}_{-0.1}$ Earth oceans, respectively, with corresponding maximum oxygen retention of 1290$^{+75}_{-75}$, 800$^{+40}_{-40}$, 560$^{+30}_{-25}$, and 90$^{+10}_{-10}$ bars. We explore statistical constraints on initial water content imposed by current water content, which could inform evolutionary history and planet formation. If TRAPPIST-1b is airless while TRAPPIST-1c possesses a tenuous oxygen atmosphere, as initial JWST observations suggest, then our models predict an initial surface water content of 8.2$^{+1.5}_{-1.0}$ Earth oceans for these worlds, leading to the outer planets retaining $>$1.5 Earth oceans after entering the habitable zone. Even if TRAPPIST-1c is airless, surface water on the outer planets would not be precluded.

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arXiv2021

The Rise and Fall of the Eclipsing Binary HS Hydrae

HS Hydrae is a short period eclipsing binary (P_orb=1.57 day) that belongs to a rare group of systems observed to have rapidly changing inclinations. This evolution is due to a third star on an intermediate orbit, and results in significant differences in eclipse depths and timings year-to-year. Zasche & Paschke (2012) revealed that HS Hydrae's eclipses were rapidly fading from view, predicting they would cease around 2022. Using 25 days of photometric data from Sector 009 of the Transiting Exoplanet Survey Satellite (TESS), we find that the primary eclipses for HS Hydrae were only 0.00173+/-0.00007 mag in depth in March 2019. This data from TESS likely represents the last eclipses detected from HS Hydrae. We also searched the Digitization of the Harvard Astronomical Plate Collection (DASCH) archive for historic data from the system. With a total baseline of over 125 years, this unique combination of data sets - from photographic plates to precision space-based photometry - allows us to trace the emergence and decay of eclipses from HS Hydrae, and further constrain its evolution. Recent TESS observations from Sector 035 confirm that eclipses have ceased for HS Hya, and we estimate they will begin again in 2195.

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arXiv2021

TOI-1259Ab -- a gas giant planet with 2.7% deep transits and a bound white dwarf companion

We present TOI-1259Ab, a 1.0 Rjup gas giant planet transiting a 0.71 Rsun K-dwarf on a 3.48 day orbit. The system also contains a bound white dwarf companion TOI-1259B with a projected distance of approximately 1600 AU from the planet host. Transits are observed in nine TESS sector and are 2.7 per cent deep - among the deepest known - making TOI-1259Ab a promising target for atmospheric characterization. Our follow-up radial velocity measurements indicate a variability of semiamplitude K = 71 m/s, implying a planet mass of 0.44 Mjup. By fitting the spectral energy distribution of the white dwarf we derive a total age of 4.08 (+1.21 -0.53) Gyr for the system. The K-dwarf's light curve reveals a rotational variability with a period of 28 days, which implies a gyrochronology age broadly consistent with the white dwarf's total age.

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arXiv2021

Improved Constraints for the XUV Luminosity Evolution of Trappist-1

We re-examine the XUV luminosity evolution of TRAPPIST-1 utilizing new observational constraints (XUV and bolometric luminosity) from multi-epoch X-ray/UV photometry. Following the formalism presented in Fleming et al. (2020), we infer that TRAPPIST-1 maintained a saturated XUV luminosity, relative to the bolometric luminosity, of $\log_{10}$(L$_{\rm XUV}$/L$_{\rm bol}$) $= -3.03_{-0.23}^{+0.25}$ at early times for a period of $t_{sat} = 3.14_{-1.46}^{+2.22}$ Gyr. After the saturation phase, we find L$_{\rm XUV}$ decayed over time by an exponential rate of $β_{\rm XUV} = -1.17_{-0.28}^{+0.27}$. Compared to our inferred age of the system, ${\rm age} = 7.96_{-1.87}^{+1.78}$ Gyr, our result for $t_{sat}$ suggests that there is only a $\sim4\%$~chance that TRAPPIST-1 still remains in the saturated phase today, which is significantly lower than the previous estimate of 40\%. Despite this reduction in $t_{sat}$, our results remain consistent in the conclusion that the TRAPPIST-1 planets likely received an extreme amount XUV energy -- an estimated integrated XUV energy of $\sim10^{30}-10^{32}$ erg over the star's lifetime.

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arXiv2020

Temperatures and Metallicities of M dwarfs in the APOGEE Survey

M dwarfs have enormous potential for our understanding of structure and formation on both Galactic and exoplanetary scales through their properties and compositions. However, current atmosphere models have limited ability to reproduce spectral features in stars at the coolest temperatures ($T_{\rm eff} < 4200\,$K) and to fully exploit the information content of current and upcoming large-scale spectroscopic surveys. Here we present a catalog of spectroscopic temperatures, metallicities, and spectral types for 5875 M dwarfs in the Apache Point Observatory Galactic Evolution Experiment (APOGEE) and Gaia DR2 surveys using The Cannon: a flexible, data-driven spectral-modeling and parameter-inference framework demonstrated to estimate stellar-parameter labels ($T_{\rm eff}$, log$g$, [Fe/H], and detailed abundances) to high precision. Using a training sample of 87 M dwarfs with optically derived labels spanning $2860 < T_{\rm eff} < 4130\,$K calibrated with bolometric temperatures, and $-0.5 < $[Fe/H]$ < 0.5\,$dex calibrated with FGK binary metallicities, we train a two-parameter model with predictive accuracy (in cross-validation) to $77\,$K and $0.09\,$dex respectively. We also train a one-dimensional spectral classification model using 51 M dwarfs with Sloan Digital Sky Survey optical spectral types ranging from M0 to M6, to predictive accuracy of 0.7 types. We find Cannon temperatures to be in agreement to within $60\,$K compared to a subsample of 1702 sources with color-derived temperatures, and Cannon metallicities to be in agreement to within $0.08\,$dex metallicity compared to a subsample of 15 FGK+M or M+M binaries. Finally, our comparison between Cannon and APOGEE pipeline (ASPCAP DR14) labels finds that ASPCAP is systematically biased toward reporting higher temperatures and lower metallicities for M dwarfs.

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