arXiv subjects

Maxwell A. Kroft

Publications and source records attributed to Maxwell A. Kroft.

6 recordsLinked to original sources

arXiv2026

Alfred: A Flexible, User-Friendly Python Package for Exoplanet Confirmation

In the era of TESS, exoplanet follow-up and confirmation have become a massive community effort. With only about an eighth of the over 8,000 TESS exoplanet candidates confirmed, astronomers need flexible software to allow them to characterize many different kinds of systems with data from multiple telescopes and instruments. In this work, I present Alfred (the Awesome Library For Robust Exoplanet Detection), an open-source Python package for exoplanet detection and confirmation. Alfred is designed to be flexible and easy to use, allowing users to fit transit and radial velocity data for an arbitrary system of exoplanets. The code is released under an MIT license on GitHub (https://github.com/maxkroft/Alfred ) and is installable via pip, with documentation under active development (https://alfred-exoplanets.readthedocs.io/en/latest/index.html# ).

astro-ph.IM↗

arXiv2026

Discovery and Characterization of the TOI-4468 Planetary System: A Transiting Hot Jupiter With a Lone Nearby Outer Companion

We report the discovery of two planets, a hot Jupiter and a nearby outer sub-Neptune, orbiting the star TOI-4468. This system is unique among the current exoplanet census in that it features a close outer companion to a hot Jupiter without an accompanying inner companion. By jointly fitting radial velocity measurements taken with the NEID spectrograph and transit photometry from TESS and several ground-based observatories, we constrain the orbital periods, masses, and radii of these two planets. We confirm the planetary nature of the hot Jupiter TOI-4468 b ($R = 1.01 R_J$, $m = 0.54 M_J$, $P = 2.77$ days). We also validate the outer planet TOI-4468 c ($R = 0.28 R_J$, $P = 7.01$ days) statistically, incorporating constraints from ground-based observations. We also identify, but cannot confirm, an additional radial velocity signal which may be due to an outer giant in this system with an orbital period of 624 days. From the observed geometry of this system, we argue that it must never have encountered an early secular resonance that is thought to excite the mutual inclination of other hot Jupiter/outer companion systems. We discuss the possibility of an undetected inner companion, as well as potential implications for hot Jupiter formation.

astro-ph.EP↗

arXiv2026

GJ 523b is a Massive, 170 Myr-old Mega-Earth, Likely on a Polar Orbit

We use WIYN/NEID radial velocity measurements to confirm the planetary nature and measure the mass of the TESS transiting exoplanet candidate around the mid-K dwarf GJ 523 ($V=9.23$, $K=6.525$). We find that GJ 523b is on a 17.75 day orbit and has a radius of $2.55\pm0.15\,R_\oplus$, a mass of $23.5\pm3.3\,M_\oplus$, and a zero-albedo equilibrium temperature of 538 K. GJ 523b's high bulk density of $7.8\pm1.8$ g cm$^{-3}$ and position on a mass-radius diagram implies a surprising low atmospheric mass fraction despite its relatively large mass. Additionally, we determine that the system has an age of $169^{+100}_{-48}$ Myr through a gyrochronological analysis of GJ 523 and its comoving companions. We also use the SED-derived stellar radius, the photometric rotation period, and the spectroscopic $v\sin i_\star$ to derive a stellar inclination of $17.6\pm5.0$ degrees, implying that GJ 523b has a minimum orbital obliquity of $71.4_{-5.0}^{+4.7}$ degrees. GJ 523b's high mass, apparent lack of a gas envelope, young age, and high orbital obliquity present a challenge to typical planet formation pathways, and at the moment there is not enough data on the system to definitively determine how GJ 523b formed. Finally, we present a new observational classification for ultra-dense, sub-Neptune-sized exoplanets similar to GJ 523b: the mega-Earths, planets with $R_p \geq2.1\,R_\oplus$ and $ρ_p \geq 5.5$ g cm$^{-3}$.

astro-ph.EP↗

arXiv2025

The TESS Grand Unified Hot Jupiter Survey. III. Thirty More Giant Planets

We present the discovery of 30 transiting giant planets that were initially detected using data from NASA's Transiting Exoplanet Survey Satellite (TESS) mission. These new planets orbit relatively bright ($G \leq 12.5$) FGK host stars with orbital periods between 1.6 and 8.2 days, and have radii between 0.9 and 1.7 Jupiter radii. We performed follow-up ground-based photometry, high angular-resolution imaging, high-resolution spectroscopy and radial velocity monitoring for each of these objects to confirm that they are planets and determine their masses and other system parameters. The planets' masses span more than an order of magnitude ($0.17\,M_J < M_p < 3.3\,M_J$). For two planets, TOI-3593 b and TOI-4961 b, we measured significant non-zero eccentricities of $0.11^{+0.05}_{-0.03}$ and $0.18^{+0.04}_{-0.05}$ respectively, while for the other planets, the data typically provide a 1-$σ$ upper bound of 0.15 on the eccentricity. These discoveries represent a major step toward assembling a complete, magnitude-limited sample of transiting hot Jupiters around FGK stars.

astro-ph.EP↗

arXiv2025

A Pair of Dynamically Interacting Sub-Neptunes Around TOI-6054

We confirm the planetary nature of a pair of transiting sub-Neptune exoplanets orbiting the bright F-type sub-giant star TOI-6054 ($V=8.02$, $K=6.673$) as a part of the OrCAS radial velocity survey using WIYN/NEID observations. We find that TOI-6054b and TOI-6054c have radii of $2.65 \pm 0.15$ $R_{\oplus}$ and $2.81 \pm 0.18$ $R_{\oplus}$, respectively, and masses of $12.4 \pm 1.7$ $M_{\oplus}$ and $9.2 \pm 2.0$ $M_{\oplus}$. The planets have zero-albedo equilibrium temperatures of $1360 \pm 33$ K and $1144 \pm 28$ K. The host star has expanded and will evolve off of the Main Sequence within the next $\sim$500 Myr, and the resulting increase in stellar luminosity has more than doubled the stellar flux the two planets receive compared to the start of the host star's main sequence phase. Consequently, TOI-6054b may be losing some of its primordial H/He atmosphere -- if it has one. Based on dynamical simulations performed using the orbital parameters of the two planets, TOI-6054b, and TOI-6054c are very likely in a 5:3 mean motion resonance. The TOI-6054 system thus has the potential to be an excellent candidate for future atmospheric follow-up observations, with two similarly sized sub-Neptunes around a bright star. We also estimate that if TOI-6054b is currently losing its H/He atmosphere this should be observable from space and from the ground.

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arXiv2024

OrCAS: Origins, Compositions, and Atmospheres of Sub-neptunes. I. Survey Definition

Sub-Neptunes - volatile-rich exoplanets smaller than Neptune - are intrinsically the most common type of planet known. However, the formation and nature of these objects, as well as the distinctions between sub-classes (if any), remain unclear. Two powerful tools to tease out the secrets of these worlds are measurements of (i) atmospheric composition and structure revealed by transit and/or eclipse spectroscopy, and (ii) mass, radius, and density revealed by transit photometry and Doppler spectroscopy. Here we present OrCAS, a survey to better elucidate the origins, compositions, and atmospheres of sub-Neptunes. This radial velocity survey uses a repeatable, quantifiable metric to select targets suitable for subsequent transmission spectroscopy and address key science themes about the atmospheric & internal compositions and architectures of these systems. Our survey targets 26 systems with transiting sub-Neptune planet candidates, with the overarching goal of increasing the sample of such planets suitable for subsequent atmospheric characterization. This paper lays out our survey's science goals, defines our target prioritization metric, and performs light-curve fits and statistical validation using existing TESS photometry and ground-based follow-up observations. Our survey serves to continue expanding the sample of small exoplanets with well-measured properties orbiting nearby bright stars, ensuring fruitful studies of these systems for many years to come.

astro-ph.EP↗