Direct Imaging Confirmation and Characterization of a Dust-Enshrouded Candidate Exoplanet Orbiting Fomalhaut

TL;DR

This study confirms the existence of Fomalhaut b as a dust-enshrouded candidate exoplanet through direct imaging, providing new astrometric and spectral data that support its planetary nature and potential orbit.

Contribution

First direct imaging confirmation of Fomalhaut b with multi-epoch optical data, refining its properties and supporting its classification as a planet candidate.

Findings

Fomalhaut b's motion may align with a non debris ring-crossing orbit.

Emission is from starlight scattered by dust, not thermal emission.

Mass estimate of Fomalhaut b is less than 2 Jupiter masses.

Abstract

We present Subaru/IRCS J band data for Fomalhaut and a (re)reduction of archival 2004--2006 HST/ACS data first presented by Kalas et al. (2008). We confirm the existence of a candidate exoplanet, Fomalhaut b, in both the 2004 and 2006 F606W data sets at a high signal-to-noise. Additionally, we confirm the detection at F814W and present a new detection in F435W. Fomalhaut b's space motion may be consistent with it being in an apsidally-aligned, non debris ring-crossing orbit, although new astrometry is required for firmer conclusions. We cannot confirm that Fomalhaut b exhibits 0.7-0.8 mag variability cited as evidence for planet accretion or a semi-transient dust cloud. The new, combined optical SED and IR upper limits confirm that emission identifying Fomalhaut b originates from starlight scattered by small dust, but this dust is most likely associated with a massive body. The Subaru and IRAC/4.5 micron upper limits imply M < 2 Mj, still consistent with the range of Fomalhaut b masses needed to sculpt the disk. Fomalhaut b is very plausibly "a planet identified from direct imaging" even if current images of it do not, strictly speaking, show thermal emission from a directly imaged planet.