Dániel Apai

Magnetic Activity as a Driver of Low-gravity-like Spectral Morphology in Late-M Dwarfs

Chia-Lung Lin, Daniel Apai, Benjamin V. Rackham +7

We present a systematic investigation of the connection between magnetic activity and the low-surface-gravity-like near-infrared spectral morphology of late-M dwarfs. Our sample in…

The Pandora SmallSat: post-launch operations and mission update

Trevor O. Foote, Elisa V. Quintana, Jessie L. Dotson +41

The Pandora SmallSat is a NASA flight project designed to study the atmospheres of exoplanets. Transmission spectroscopy of transiting exoplanets provides our best opportunity to i…

Super-Earth Interiors Shrink by About 10% as They Crystallise

Tim Lichtenberg, Mara Attia, Harrison Nicholls +26

Super-Earth exoplanets are among the most abundant planets known, yet their bulk densities leave the interior state degenerate. The static structure models used to interpret them,…

Multi-Epoch Stability in the Rotational Modulation of the Planetary-Mass Companion Ross 458C

Elena Manjavacas, Jared Bull, Paulo Miles-Paez +7

Spectroscopic variability is detected in brown dwarfs across all spectral types, suggesting atmospheric patchiness in brown dwarf atmospheres. We present JWST/NIRSpec time series o…

Water Cloud and Chemical Modulations in the Coldest Brown Dwarf

Brittany E. Miles, James Mang, Caroline V. Morley +24

We present high signal-to-noise, medium resolution (R ~ 1000), time-series JWST/NIRSpec spectra of WISE 0855 (265K), the coldest known brown dwarf. Medium resolution, time-series s…

A Grid of Contribution Functions to Help the Interpretation of Time-resolved Observations of Brown Dwarfs

Myrla Phillippe, Theodora Karalidi, Elena Manjavacas +4

We present a grid of thermal emission contribution functions and their corresponding atmospheric spectra model for cloudy and cloud-free brown dwarfs, spanning effective temperatur…

Small-Body Science with the Nautilus Space Observatory: From Cislunar Space Resilience to Mapping the Kuiper-Belt-to-Oort-Cloud Transition

J. de Wit, A. Y. Burdanov, P. McGill +3

A new generation of space-based observatories can transform small-body science from the local Earth-Moon environment to the Solar System's dynamical frontier, where planetary contr…

Photometric Variability and Rotation of Beta Pictoris b from JWST NIRCam Coronagraphic Imaging

Yifan Zhou, Beth A. Biller, Aarynn L. Carter +28

We report the detection of photometric variability in the directly imaged super-Jupiter $β$ Pictoris b. Using JWST NIRCam dual-band coronagraphic imaging, we conducted a 16-hour co…

When Stabilizing Feedbacks Wreak Havoc in Habitable Planets: Chaos at the Freezing Point in a Four-Feedback Climate Model

Chaucer Langbert, Dániel Apai, Renu Malhotra

The long-term habitability of Earth-like planets is governed by the balance of positive and negative climate feedbacks that regulate surface temperature and atmospheric composition…

The Interstellar Laser Beacons Hypothesis and the Cosmic Lighthouses Project

Daniel Apai, Chia-Lung Lin, Kevin Wagner

In this paper, we argue that in a realistic, resource-limited scenario senders whose intent is to maximize successful communication at the lowest cost will utilize very long-lived,…

astro-ph.EP2026★ 1 cited

Direct Imaging Discovery of Giant Exoplanet $β$ Pictoris d: A Decade-Long Game of Hide-and-Seek

Ben J. Sutlieff, Markus J. Bonse, Valentin Christiaens +94

We report the direct imaging discovery of a third exoplanet in the $β$ Pictoris system. We detect $β$ Pictoris d ( $β$ Pic d) in non-coronagraphic observations obtained with VLT/ERI…

Nautilus Space Observatory: Unveiling the Diversity and Origin of Sub-Neptunes with the Nautilus Space Observatory

Luis Welbanks, Kylie E. Hall, Julien de Wit +10

Sub-Neptunes are the most common class of planets in the Galaxy, yet they have no Solar System analog and remain poorly understood as a population. JWST observations have revealed…

Mapping Stellar Heterogeneities with the Nautilus Space Observatory

Adina D. Feinstein, Jeff Valenti, Julien de Wit +9

Stellar photospheric heterogeneities, such as starspots and faculae, are a fundamental limitation for exoplanet transmission spectroscopy. Inhomogeneous surfaces can imprint wavele…

Asymmetric nightside CO2 features, inefficient heat transport, and precise evolutionary constraints: Spectroscopic phase curves reveal the past and present of a white dwarf-brown dwarf binary

Daphne Broski-Laing, Yifan Zhou, Joshua D. Lothringer +10

We present the first JWST phase curve of a white dwarf-brown dwarf binary, a NIRSpec PRISM observation of ZTFJ0038+2030. Short-period white dwarf-brown dwarf binaries provide uniqu…

Nautilus: Fast Time-Resolved Spectroscopy of GKM Stellar Flares and Their Implications for Planetary Habitability

Chia-Lung Lin, Adina D. Feinstein, Jeff Valenti +10

Low-mass GKM dwarfs are prime targets for finding habitable-zone Earth-sized planets, but their frequent flares, especially on M~dwarfs, can strongly affect planetary atmospheres t…

Nautilus Space Observatory: The Evolution of Planets and their Atmospheres

Ilaria Pascucci, Noah Tuchow, Yifan Zhou +11

We are just beginning to explore the billion-year evolution from nascent planets in disks to mature planetary systems. Recent discoveries hint at demographic and atmospheric differ…

A Scalable Path to Astrometric Exomoon Discoveries with the Nautilus Space Observatory

Kevin Wagner, Sumin Seung, Dániel Apai +13

Moons orbiting exoplanets (exomoons) can be detected through the reflex motion they impart to their host planet, which is recoverable in relative star-planet astrometric time serie…

A single power law for the TRAPPIST-1 flare distribution across four orders of magnitude in energy

Valeriy Vasilyev, Alexander I. Shapiro, Nadiia Kostogryz +10

TRAPPIST-1 is an ultra-cool dwarf that flares frequently. These flares shape the surrounding planets' high-energy irradiation environments, with consequences for atmospheric chemis…

NASA's Pandora SmallSat Mission: Simulating the Impact of Stellar Photospheric Heterogeneity and Its Correction

Benjamin V. Rackham, Aishwarya R. Iyer, Dániel Apai +28

Stellar photospheric heterogeneity is a dominant astrophysical systematic impacting exoplanet transmission spectroscopy. NASA's Pandora SmallSat Mission is designed to address this…

Unlocking HST's Stellar Treasure Trove: Stellar Activity Minima for HAT-P-11 Offer Prime Windows for Transmission Spectroscopy

Prajwal Niraula, Benjamin V. Rackham, Julien de Wit +4

HAT-P-11 is a well-studied, active K dwarf hosting an eccentric, misaligned transiting sub-Neptune. As part of the HST Stellar Treasure Trove program (HST-AR-17551), we analyze abs…