About

Daniel Fabrycky is a professor in the Department of Astronomy and Astrophysics at The University of Chicago. He holds a PhD from Princeton University, obtained in 2007. His research focuses on the dynamics of extrasolar planets, studying how the observations of planets orbiting other stars constrain the configurations of these exoplanetary systems. He investigates how gravitational interactions, tidal effects, and energy dissipation influence the architecture and evolution of planetary systems. As a leader of the Exoplanet Reading Group, Fabrycky actively engages in exploring the theoretical issues posed by the diverse types and system architectures of exoplanets discovered over the past two decades.

Research topics

• Physics
• Astronomy
• Astrophysics

Selected publications

• Transit Timing and Duration Variations for the Discovery and Characterization of Exoplanets in the TESS Era

  2025-01-01 · 1 citations

  book-chapterSenior author
  PublisherDOI

• Accounting for Transit Timing Detectability: Biases in Planetary Radius and Orbital Period

  The Astronomical Journal · 2025-12-02

  articleOpen access

  Abstract Transit Timing Variations (TTVs) are deviations from the time an observer would expect to see an exoplanet transit its host star. In multiplanetary systems, significant TTVs may indicate the presence of another body in the system gravitationally interacting with the transiting exoplanet. T. Holczer et al. catalog 2599 Kepler Objects of Interest (KOIs) and provide a statistical analysis of their TTVs for candidates that have transited at least seven times. However, this conservative limit on the number of transits neglects long-period KOIs. Therefore, we extend the statistical analysis performed by T. Holczer et al. to the population of KOIs that have between three and six transits. We identify six KOIs, three of which have Kepler names (Kepler–103 c, Kepler–90 g, and Kepler–1662 c), with significant TTV signals that were originally overlooked by T. Holczer et al. Additionally, we search for trends regarding the planetary radius and orbital period of KOIs with significant TTVs. Through a survival analysis, we determine that planets with shorter orbital periods require larger TTV signals to be detected compared to longer period planets, regardless of planetary size. Uncovering trends in TTV statistics such as this one will provide targets for future forward modeling of planetary architectures.

  PublisherDOI

• Updated Masses for the Gas Giants in the Eight-planet Kepler-90 System Via Transit-timing Variation and Radial Velocity Observations

  The Astronomical Journal · 2025-08-05 · 1 citations

  articleOpen accessSenior authorCorresponding

  Abstract The eight-planet Kepler-90 system exhibits the greatest multiplicity of planets found to date. All eight planets are transiting and were discovered in photometry from the NASA Kepler primary mission. The two outermost planets, g ( P g = 211 days) and h ( P h = 332 days), exhibit significant transit-timing variations (TTVs), but were only observed six and three times, respectively, by Kepler. These TTVs allow for the determination of planetary masses through dynamical modeling of the pair’s gravitational interactions, but the paucity of transits allows a broad range of solutions for the masses and orbital ephemerides. To determine accurate masses and orbital parameters for planets g and h, we combined 34 radial velocities (RVs) of Kepler-90, collected over a decade, with the Kepler transit data. We jointly modeled the transit times of the outer two planets and the RV time series, then used our two-planet model to predict their future times of transit. These predictions led us to recover a transit of Kepler-90 g with ground-based observatories in 2024 May. We then combined the 2024 transit and several previously unpublished transit times of planets g and h with the Kepler photometry and RV data to update the masses and linear ephemerides of the planets, finding masses for g and h of 15.0 ± 1.3 M ⊕ and 203 ± 16 M ⊕, respectively, from a Markov Chain Monte Carlo analysis. These results enable further insights into the architecturally rich Kepler-90 system and pave the way for atmospheric characterization with space-based facilities.

  PublisherDOI

• Validating the Orbital Periods of the Coolest TESS Planet Candidates

  The Astronomical Journal · 2025-05-09

  articleOpen accessSenior author

  Abstract When an exoplanet passes in front of its host star, the resulting eclipse causes an observable decrease in stellar flux, and when multiple such transits are detected, the orbital period of the exoplanet can be determined. Over the past seven years NASA’s Transiting Exoplanet Survey Satellite (TESS) has discovered thousands of potential planets by this method, mostly with short orbital periods, although some have longer reported values over 100 days. These long orbital periods, however, are not easy to confirm due to frequent lengthy data gaps. Here we show that while many of these long period candidates likely have periods much shorter than reported, there are some TESS candidates with long periods to be found in the data. These candidates generally only have two reported transits, but the periods of duo-transits like this, and even candidates with three or more transits can be confirmed if the data rules out all possible shorter period aliases. Using TESS data, we confirm long orbital periods for nine candidate planets, and present five others that are likely long period ( P > 100 days). Due to their long periods, these planets will also have relatively cool equilibrium temperatures. We present these TESS Objects of Interest, along with a variety of small corrections to other TESS orbital periods and three planet candidates with possible transit timing variations, with the goal of refining the TESS data set and enabling future research with respect to cool transiting planets.

  PublisherDOI

• Updated Masses for the Gas Giants in the Eight-Planet Kepler-90 System Via Transit-Timing Variation and Radial Velocity Observations

  ArXiv.org · 2025-07-18

  preprintOpen accessSenior author

  The eight-planet Kepler-90 system exhibits the greatest multiplicity of planets found to date. All eight planets are transiting and were discovered in photometry from the NASA Kepler primary mission. The two outermost planets, g ($P_g$ = 211 d) and h ($P_h$ = 332 d) exhibit significant transit-timing variations (TTVs), but were only observed 6 and 3 times respectively by Kepler. These TTVs allow for the determination of planetary masses through dynamical modeling of the pair's gravitational interactions, but the paucity of transits allows a broad range of solutions for the masses and orbital ephemerides. To determine accurate masses and orbital parameters for planets g and h, we combined 34 radial velocities (RVs) of Kepler-90, collected over a decade, with the Kepler transit data. We jointly modeled the transit times of the outer two planets and the RV time series, then used our two-planet model to predict their future times of transit. These predictions led us to recover a transit of Kepler-90 g with ground-based observatories in May 2024. We then combined the 2024 transit and several previously unpublished transit times of planets g and h with the Kepler photometry and RV data to update the masses and linear ephemerides of the planets, finding masses for g and h of $15.0 \pm 1.3\, M_\oplus$, and $203 \pm 16\, M_\oplus$ respectively from a Markov Chain Monte Carlo analysis. These results enable further insights into the architecturally rich Kepler-90 system and pave the way for atmospheric characterization with space-based facilities.

  PublisherOA PDFDOI

• Investigating the Atmospheric Mass Loss of the Kepler-105 Planets Straddling the Radius Gap

  The Astronomical Journal · 2024-01-31 · 1 citations

  articleOpen access

  Abstract An intriguing pattern among exoplanets is the lack of detected planets between approximately 1.5 R ⊕ and 2.0 R ⊕ . One proposed explanation for this “radius gap” is the photoevaporation of planetary atmospheres, a theory that can be tested by studying individual planetary systems. Kepler-105 is an ideal system for such testing due to the ordering and sizes of its planets. Kepler-105 is a Sun-like star that hosts two planets straddling the radius gap in a rare architecture with the larger planet closer to the host star ( R b = 2.53 ± 0.07 R ⊕ , P b = 5.41 days, R c = 1.44 ± 0.04 R ⊕ , P c = 7.13 days). If photoevaporation sculpted the atmospheres of these planets, then Kepler-105b would need to be much more massive than Kepler-105c to retain its atmosphere, given its closer proximity to the host star. To test this hypothesis, we simultaneously analyzed radial velocities and transit-timing variations of the Kepler-105 system, measuring disparate masses of M b = 10.8 ± 2.3 M ⊕ ( ρ b = 3.68 ± 0.84 g cm −3 ) and M c = 5.6 ± 1.2 M ⊕ ( ρ c = 10.4 ± 2.39 g cm −3 ). Based on these masses, the difference in gas envelope content of the Kepler-105 planets could be entirely due to photoevaporation (in 76% of scenarios), although other mechanisms like core-powered mass loss could have played a role for some planet albedos.

  PublisherOA PDFDOI

• Updated Catalog of Kepler Planet Candidates: Focus on Accuracy and Orbital Periods

  The Planetary Science Journal · 2024-06-01 · 17 citations

  articleOpen access

  Abstract We present a new catalog of Kepler planet candidates that prioritizes accuracy of planetary dispositions and properties over uniformity. This catalog contains 4376 transiting planet candidates, including 1791 residing within 709 multiplanet systems, and provides the best parameters available for a large sample of Kepler planet candidates. We also provide a second set of stellar and planetary properties for transiting candidates that are uniformly derived for use in occurrence rate studies. Estimates of orbital periods have been improved, but as in previous catalogs, our tabulated values for period uncertainties do not fully account for transit timing variations (TTVs). We show that many planets are likely to have TTVs with long periodicities caused by various processes, including orbital precession, and that such TTVs imply that ephemerides of Kepler planets are not as accurate on multidecadal timescales as predicted by the small formal errors (typically 1 part in 10 6 and rarely >10 −5 ) in the planets’ measured mean orbital periods during the Kepler epoch. Analysis of normalized transit durations implies that eccentricities of planets are anticorrelated with the number of companion transiting planets. Our primary catalog lists all known Kepler planet candidates that orbit and transit only one star; for completeness, we also provide an abbreviated listing of the properties of the two dozen nontransiting planets that have been identified around stars that host transiting planets discovered by Kepler.

  PublisherDOI

• Validating the Orbital Periods of the Coolest TESS Exoplanet Candidates

  arXiv (Cornell University) · 2024-11-26

  preprintOpen accessSenior author

  When an exoplanet passes in front of its host star, the resulting eclipse causes an observable decrease in stellar flux, and when multiple such transits are detected, the orbital period of the exoplanet can be determined. Over the past six years, NASA's Transiting Exoplanet Survey Satellite (TESS) has discovered thousands of potential planets by this method, mostly with short orbital periods, although some have longer reported values over one hundred days. These long orbital periods, however, are note easy to confirm due to frequent lengthy data gaps. Here we show that while the majority of these long period candidates likely have periods much shorter than reported, there are a sizable number of TESS candidates with true long periods. These candidates generally only have two reported transits, but the periods of duo-transits like this, and even candidates with three or more transits, can be confirmed if the data rules out all possible shorter period aliases. Using TESS data, we confirm long orbital periods for nine candidate planets, and present five others that are likely long period. Due to their long periods, these planets will have relatively cool equilibrium temperatures, and may be more likely to host exomoons or rings. We present these TOIs, along with a variety of small corrections to other TESS orbital periods and three planet candidates with possible transit timing variations, with the goal of refining the TESS data set and enabling future research with respect to cool transiting planets.

  PublisherOA PDFDOI

• Updated Catalog of Kepler Planet Candidates: Focus on Accuracy and Orbital Periods

  arXiv (Cornell University) · 2023-11-01 · 2 citations

  preprintOpen access

  We present a new catalog of Kepler planet candidates that prioritizes accuracy of planetary dispositions and properties over uniformity. This catalog contains 4376 transiting planet candidates, including 1791 residing within 709 multi-planet systems, and provides the best parameters available for a large sample of Kepler planet candidates. We also provide a second set of stellar and planetary properties for transiting candidates that are uniformly-derived for use in occurrence rates studies. Estimates of orbital periods have been improved, but as in previous catalogs, our tabulated values for period uncertainties do not fully account for transit timing variations (TTVs). We show that many planets are likely to have TTVs with long periodicities caused by various processes, including orbital precession, and that such TTVs imply that ephemerides of Kepler planets are not as accurate on multi-decadal timescales as predicted by the small formal errors (typically 1 part in $10^6$ and rarely $ > 10^{-5}$) in the planets' measured mean orbital periods during the Kepler epoch. Analysis of normalized transit durations implies that eccentricities of planets are anti-correlated with the number of companion transiting planets. Our primary catalog lists all known Kepler planet candidates that orbit and transit only one star; for completeness, we also provide an abbreviated listing of the properties of the two dozen non-transiting planets that have been identified around stars that host transiting planets discovered by Kepler.

  PublisherOA PDFDOI

• Tidal dissipation in satellites prevents Hill sphere escape

  Monthly Notices of the Royal Astronomical Society · 2023-11-16 · 12 citations

  articleOpen accessSenior author

  ABSTRACT The transit method is a promising means of detecting exomoons, but few candidates have been identified. For planets close to their stars, the dynamical interaction between a satellite’s orbit and the star must be important in their evolution. Satellites beyond synchronous orbit spiral out due to the tide raised on their planet, and it has been assumed that they would likely escape the Hill sphere. Here we follow the evolution with a three-body code that accounts for tidal dissipation within both the planet and the satellite. We show that tidal dissipation in satellites often keeps them bound to their planet, making exomoons more observable than previously thought. The probability of escape depends on the ratio of tidal quality factors of the planet and satellite; when this ratio exceeds 0.5, escape is usually avoided. Instead, the satellite moves to an equilibrium in which the spin angular momentum of the planet is not transferred into the orbit of the satellite, but is transferred into the orbit of the planet itself. While the planet continues spinning faster than the satellite orbits, the satellite maintains a semi-major axis of approximately 0.41 Hill radii. These states are accompanied with modest satellite eccentricity near 0.1 and are found to be stable over long time-scales.

  PublisherOA PDFDOI

Frequent coauthors

• Eric B. Ford

  100 shared

• Jason F. Rowe

  Bishop's University

  97 shared

• Jack J. Lissauer

  Ames Research Center

  97 shared

• Jon M. Jenkins

  90 shared

• Darin Ragozzine

  Brigham Young University

  89 shared

• Matthew J. Holman

  72 shared

• William F. Welsh

  68 shared

• David R. Ciardi

  NASA Exoplanet Science Institute

  67 shared

Education

• Ph.D.

  Princeton University

  2007

Awards & honors

• Faculty Award for Excellence in Graduate Teaching and Mentor…