DIRECT IMAGING CONFIRMATION AND CHARACTERIZATION OF A DUST-ENSHROUDED CANDIDATE EXOPLANET ORBITING FOMALHAUT

Abstract

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