About

I am a Research Assistant Professor and Faculty Director for Outreach in the University of Washington's Department of Astronomy, and as of 2025 am Director of the DiRAC Institute. My research program focuses on studying time domain, large survey astronomy, with an emphasis on studying magnetically active stars and searching for technosignatures in surveys like Kepler, TESS, and LSST.

Research topics

• Astronomy
• Physics
• Astrophysics
• Geography
• Computer Science
• Data Mining
• Computer Security
• Data science
• Geology
• Cartography
• Database
• Astrobiology

Selected publications

• Gaia-GIC-1: An Evolving Catastrophic Planetesimal Collision Candidate

  The Astrophysical Journal Letters · 2026-03-11

  articleOpen accessSenior author

  Abstract We report the discovery of the optical dipper and low-luminosity infrared stellar transient Gaia20ehk (hereafter, Gaia-GIC-1), which is currently undergoing high-amplitude variability due to transiting dusty material. In this work, we identify Gaia-GIC-1 as a likely young F-type star based on the spectral energy distribution before the onset of the high-amplitude optical variability. We detect a significant periodic modulation of 380.5 days in Gaia G band before the onset of the infrared brightening, consistent with a ∼1.1 au orbit assuming circular orbits and a 1.3 M ⊙ star. The system has remained in an infrared-bright state for >4 yr since the last near-infrared detection, confirmed by recent SPHEREx observations, while continuing to undergo large-amplitude irregular optical dimming. We measure the dust temperature from the freshly generated debris to be ∼900 K based on available Wide-field Infrared Survey Explorer photometry, and the dust clump size to have a minimum cross-sectional area of 0.13 au 2 , and the dust mass 4 × 10 20 kg. Currently, optical follow-up spectroscopy has not revealed any prominent features in the system, likely due to its highly variable nature. We hypothesize that Gaia-GIC-1 represents debris recently formed in a planetary collision, which produced a clumpy dust cloud on a bound orbit, producing the observed dimming events. The ongoing collisional activity in this system presents a unique opportunity for understanding terrestrial planet formation.

  PublisherDOI

• Gas-depleted planet formation occurred in the four-planet system around the red dwarf LHS 1903

  Science · 2026-02-12

  articleOpen access

  The radii of small exoplanets form two populations, super-Earths and sub-Neptunes, separated by a gap known as the radius valley. This feature could be produced by the removal of atmospheres by stellar or internal heating or by the lack of an initial envelope. We used transit photometry and radial velocity measurements to detect and characterize four exoplanets orbiting LHS 1903, a red dwarf star in the Milky Way's thick disk. These four planets have orbital periods ranging from 2.2 to 29.3 days and span the radius valley within a single planetary system. The derived densities indicate that LHS 1903 b is rocky, whereas LHS 1903 c and LHS 1903 d have extended atmospheres. The most distant planet from the host star, LHS 1903 e, has no gaseous envelope, indicating that it formed from gas-depleted material.

  PublisherDOI

• Gas-depleted planet formation occurred in the four-planet system around the red dwarf LHS 1903

  arXiv (Cornell University) · 2026-02-11

  preprintOpen access

  Small exoplanet radii show two populations, referred to as super-Earths and sub-Neptunes, separated by a gap known as the radius valley. This may be produced by the removal of atmospheres due to stellar or internal heating, or lack of an initial envelope. We us transit photometry and radial velocity measurements to detect and characterize four planets orbiting LHS 1903, a red dwarf (M-dwarf) star in the Milky Way's thick disk. The planets have orbital periods between 2.2 and 29.3 days, and span the radius valley within a single planetary system. The derived densities indicate that LHS 1903 b is rocky, while LHS 1903 c and LHS 1903 d have extended atmospheres. Although the most distant planet from the host star, LHS 1903 e, has no gaseous envelope, indicating it formed from gas-depleted material.

  PublisherDOI

• Gaia-GIC-1: An Evolving Catastrophic Planetesimal Collision Candidate

  arXiv (Cornell University) · 2026-03-11

  preprintOpen accessSenior author

  We report the discovery of the optical dipper and low-luminosity infrared stellar transient Gaia20ehk (hereafter, Gaia-GIC-1), which is currently undergoing high-amplitude variability due to transiting dusty material. In this work, we identify Gaia-GIC-1 as a likely young F-type star based on the spectral energy distribution before the onset of the high-amplitude optical variability. We detect a significant periodic modulation of 380.5 days in Gaia-G band before the onset of the infrared brightening, consistent with a $\sim$1.1 AU orbit assuming circular orbits and a 1.3 M$_{\odot}$ star. The system has remained in an infrared bright state for $>$4 years since the last near-infrared detection, confirmed by recent SPHEREx observations, while continuing to undergo large amplitude irregular optical dimming. We measure the dust temperature from the freshly generated debris to be $\sim$900 Kelvin based on available WISE photometry, and the dust clump size to have a minimum cross-sectional area of 0.13 AU$^{2}$, and the dust mass $4\times 10^{20}$ kg. Currently, optical follow-up spectroscopy has not revealed any prominent features in the system, likely due to its highly variable nature. We hypothesize that Gaia-GIC-1 represents debris recently formed in a planetary collision, which produced a clumpy dust cloud on a bound orbit, producing the observed dimming events. The ongoing collisional activity in this system presents a unique opportunity for understanding terrestrial planet formation.

  PublisherDOI

• Prospects of Constraining Equilibrium Tides in Low-mass Binary Stars

  The Astrophysical Journal · 2025-10-09

  articleOpen accessSenior author

  Abstract The dynamical evolution of short-period low-mass binary stars (with mass M &lt; 1.5 M ⊙ , from formation to the late main sequence, and with orbital periods less than ∼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 (typically parameterized by the tidal quality factor <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi class="MJX-tex-calligraphic" mathvariant="script">Q</mml:mi> </mml:math> ) 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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi class="MJX-tex-calligraphic" mathvariant="script">Q</mml:mi> </mml:math> , we use global sensitivity analysis and simulation-based inference to examine how the initial conditions and tidal <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi class="MJX-tex-calligraphic" mathvariant="script">Q</mml:mi> </mml:math> influence the observable orbital and rotational states. Our results show that, even under the simplest and most tractable models of tides, the path toward inferring <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi class="MJX-tex-calligraphic" mathvariant="script">Q</mml:mi> </mml:math> from individual systems is severely hampered by inherent degeneracies between tidal <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi class="MJX-tex-calligraphic" mathvariant="script">Q</mml:mi> </mml:math> 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.

  PublisherDOI

• Tidal Synchronization of TESS Eclipsing Binaries

  The Astrophysical Journal · 2025-09-03 · 4 citations

  articleOpen access

  Abstract 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, rotation 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 ( P orb and P rot ) measured from the Transiting Exoplanet Satellite Survey (TESS). We first classify 4584 light curves from the TESS EB catalog according to out-of-eclipse stellar variability type: starspot modulation, ellipsoidal variability, nonperiodic variability, and “other” variability (e.g., pulsations). We then manually validate each light curve’s classification, resulting in a sample of 1039 candidates with 584 high-confidence EBs that exhibit detectable starspot modulation. From there, we measure and compare the rotation period of each starspot-modulated EB using three methods: a Lomb–Scargle periodogram, 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 P orb ≈ P rot ), and a subsynchronous population (with 8 P orb ≈ 7 P rot ). Using Bayesian model comparison, we find that a bimodal distribution is a significantly better fit than a unimodal distribution for the Kepler and TESS samples, both individually or combined, confirming that the subsynchronous population is statistically significant.

  PublisherDOI

• A Search for Radio Technosignatures from Interstellar Object 3I/ATLAS with the Allen Telescope Array

  arXiv (Cornell University) · 2025-12-19

  preprintOpen access

  In 2025 July, the third-ever interstellar object, 3I/ATLAS, was discovered on its ingress into the Solar System. Similar to the NASA Voyager missions sent in 1977, science probes by extraterrestrial life ("artifact technosignatures") could be sent to explore other stellar systems like our own. In this campaign, we used the SETI Institute's Allen Telescope Array to observe 3I/ATLAS from 1-9 GHz. We detected nearly 74 million narrowband hits in 7.25\,hr of data using the newly-developed search pipeline bliss. We then blanked hits by frequency and drift rate to mitigate radio frequency interference in our dataset, narrowing the dataset down to ~2 million hits. These hits were further filtered by the localization code NBeamAnalysis, and the remaining 211 hits were visually inspected in the time-frequency domain. We did not find any signals worthy of additional follow-up. Accounting for the Doppler drift correction and given the non-detection, we are able to set an effective isotropic radiated power upper limit of 10-110 W on radio technosignatures from 3I/ATLAS across the frequency and drift rate ranges covered by our survey.

  PublisherDOI

• Crowded Field Photometry with Rubin: Exploring 47 Tucanae with Data Preview 1

  Research Notes of the AAS · 2025-07-14 · 2 citations

  articleOpen access

  Abstract We analyze imaging from Data Preview 1 of the Vera C. Rubin Observatory to explore the performance of early LSST pipelines in the 47 Tucanae field. The coadd- object catalog demonstrates the depth and precision possible with Rubin, recovering well-defined color–magnitude diagrams for 47 Tuc Small Magellanic Cloud. Unfortunately, the existing pipelines fail to recover sources within ∼28 pc of the cluster center, due to the extreme source density. Using Rubin’s forced photometry on stars identified via Difference Imaging, we can recover sources down to ∼14 pc from the cluster center, and find 14,744 potential cluster members with this extended data set. While this forced photometry has significant systematics, our analysis showcases the potential for detailed structural studies of crowded fields with the Rubin Observatory.

  PublisherDOI

• First Temperature Profile of a Stellar Flare Using Differential Chromatic Refraction

  The Astrophysical Journal Letters · 2025-10-23

  articleOpen access

  Abstract We present the first derivation of a stellar flare temperature profile from single-band photometry. Stellar flare DWF 030225.574−545707.45129 was detected in 2015 by the Dark Energy Camera as part of the Deeper, Wider, Faster program. The brightness (Δ m g = −6.12) of this flare, combined with the high air mass (1.45 ≲ X ≲ 1.75) and blue filter (DES g , 398–548 nm) in which it was observed, provided ideal conditions to measure the zenithward apparent motion of the source due to differential chromatic refraction (DCR) and, from that, infer the effective temperature of the event. We model the flare’s spectral energy distribution as a blackbody to produce the constraints on flare temperature and geometric properties derived from single-band photometry. We additionally demonstrate how simplistic assumptions on the flaring spectrum, as well as on the evolution of flare geometry, can result in solutions that overestimate the effective temperature. Exploiting DCR enables studying chromatic phenomena with ground-based astrophysical surveys, and stellar flares on M dwarfs are a particularly enticing target for such studies due to their ubiquity across the sky and the heightened color contrast between their red quiescent photospheres and the blue flare emission. Our novel method will enable similar temperature constraints for a large sample of objects in upcoming photometric surveys like the Vera C. Rubin Legacy Survey of Space and Time.

  PublisherDOI

• Crowded Field Photometry with Rubin: Exploring 47 Tucanae with Data Preview 1

  ArXiv.org · 2025-07-04

  preprintOpen access

  We analyze imaging from Data Preview 1 of the Vera C. Rubin Observatory to explore the performance of early LSST pipelines in the 47 Tucanae field. The coadd-\texttt{object} catalog demonstrates the depth and precision possible with Rubin, recovering well-defined color magnitude diagrams for 47 Tuc Small Magellanic Cloud. Unfortunately, the existing pipelines fail to recover sources within $\sim$28 pc of the cluster center, due to the extreme source density. Using Rubin's forced photometry on stars identified via Difference Imaging, we can recover sources down to $\sim$14 pc from the cluster center, and find 14744 potential cluster members with this extended dataset. While this forced photometry has significant systematics, our analysis showcases the potential for detailed structural studies of crowded fields with the Rubin Observatory.

  PublisherOA PDF

Recent grants

• Measuring the Ages of Stars in the Era of Big Data Time-Domain Astronomy

  NSF · $278k · 2015–2018

Frequent coauthors

• Suzanne L. Hawley

  91 shared

• Sarah J. Schmidt

  42 shared

• Adam F. Kowalski

  Laboratory for Atmospheric and Space Physics

  35 shared

• Yuta Notsu

  Japan Aerospace Exploration Agency

  30 shared

• É. Aubourg

  Laboratoire AstroParticule et Cosmologie

  29 shared

• Kevin R. Covey

  27 shared

• Nicolás G. Busca

  26 shared

• John J. Bochanski

  26 shared

Labs

• DiRACPI