Assessing Ariel's capabilities to observe free-floating brown dwarfs

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Auteurs principaux: Akhmetshyn, Roman, Cowan, Nicolas B, Casewell, Sarah
Format: Preprint
Publié: 2026
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author Akhmetshyn, Roman
Cowan, Nicolas B
Casewell, Sarah
author_facet Akhmetshyn, Roman
Cowan, Nicolas B
Casewell, Sarah
contents The primary goal of the Ariel space telescope is to conduct the biggest spectroscopic survey of transiting exoplanets to characterize their atmospheres and weather. We propose to extend the Ariel survey to another domain of alien atmospheres - rogue planets and free-floating brown dwarfs. Their isolated nature means the observations are uncontaminated by light from a host star, and their short rotation periods, often similar to hot Jupiter orbital periods, provide an opportunity to study time-varying meteorology. Phase curve observations would especially help scientists understand atmospheric dynamics at the L/T transition, where multiple cloud species at different altitudes influence the time-varying spectra of brown dwarfs. Inferring timescales and length scales of these atmospheric features is key to understanding the meteorology of sub-stellar objects. We quantify how many isolated cool objects that Ariel's fine guidance sensor (FGS) is able to guide on. Among 2744 selected targets, none are bright enough under the planned 10 Hz FGS cadence; however, with a "slow" fine guidance mode of 1 Hz, Ariel could study 98 L0- to L5-type brown dwarfs. We simulate single-epoch and time-series spectroscopic observations of the brightest isolated brown dwarfs given currently known instrumental specifications. We show that the resolution and sensitivity of Ariel instruments in the 1.1-7.8 micron regime can measure cloud-induced variability at the sub-percent level. A survey of brown dwarf phase curve observations, unavailable to ground-based telescopes, would be the perfect complement to Ariel's survey of atmospheric variability in hot Jupiters.
format Preprint
id arxiv_https___arxiv_org_abs_2605_28924
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Assessing Ariel's capabilities to observe free-floating brown dwarfs
Akhmetshyn, Roman
Cowan, Nicolas B
Casewell, Sarah
Earth and Planetary Astrophysics
Instrumentation and Methods for Astrophysics
Solar and Stellar Astrophysics
The primary goal of the Ariel space telescope is to conduct the biggest spectroscopic survey of transiting exoplanets to characterize their atmospheres and weather. We propose to extend the Ariel survey to another domain of alien atmospheres - rogue planets and free-floating brown dwarfs. Their isolated nature means the observations are uncontaminated by light from a host star, and their short rotation periods, often similar to hot Jupiter orbital periods, provide an opportunity to study time-varying meteorology. Phase curve observations would especially help scientists understand atmospheric dynamics at the L/T transition, where multiple cloud species at different altitudes influence the time-varying spectra of brown dwarfs. Inferring timescales and length scales of these atmospheric features is key to understanding the meteorology of sub-stellar objects. We quantify how many isolated cool objects that Ariel's fine guidance sensor (FGS) is able to guide on. Among 2744 selected targets, none are bright enough under the planned 10 Hz FGS cadence; however, with a "slow" fine guidance mode of 1 Hz, Ariel could study 98 L0- to L5-type brown dwarfs. We simulate single-epoch and time-series spectroscopic observations of the brightest isolated brown dwarfs given currently known instrumental specifications. We show that the resolution and sensitivity of Ariel instruments in the 1.1-7.8 micron regime can measure cloud-induced variability at the sub-percent level. A survey of brown dwarf phase curve observations, unavailable to ground-based telescopes, would be the perfect complement to Ariel's survey of atmospheric variability in hot Jupiters.
title Assessing Ariel's capabilities to observe free-floating brown dwarfs
topic Earth and Planetary Astrophysics
Instrumentation and Methods for Astrophysics
Solar and Stellar Astrophysics
url https://arxiv.org/abs/2605.28924