The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems I: High Contrast Imaging of the Exoplanet HIP 65426 b from 2-16 $μ$m

Kavli Affiliate: Bruce Macintosh

| First 5 Authors: Aarynn L. Carter, Sasha Hinkley, Jens Kammerer, Andrew Skemer, Beth A. Biller

| Summary:

We present JWST Early Release Science (ERS) coronagraphic observations of the
super-Jupiter exoplanet, HIP 65426 b, with the Near-Infrared Camera (NIRCam)
from 2-5 $mu$m, and with the Mid-Infrared Instrument (MIRI) from 11-16 $mu$m.
At a separation of $sim$0.82" (87$^{+108}_{-31}$ au), HIP 65426 b is clearly
detected in all seven of our observational filters, representing the first
images of an exoplanet to be obtained by JWST, and the first ever direct
detection of an exoplanet beyond 5 $mu$m. These observations demonstrate that
JWST is exceeding its nominal predicted performance by up to a factor of 10,
with measured 5$sigma$ contrast limits of $sim$4$times10^{-6}$ ($sim$2.4
$mu$Jy) and $sim$2$times10^{-4}$ ($sim$10 $mu$Jy) at 1" for NIRCam at 3.6
$mu$m and MIRI at 11.3 $mu$m, respectively. These contrast limits provide
sensitivity to sub-Jupiter companions with masses as low as 0.3
$M_mathrm{Jup}$ beyond separations of $sim$100 au. Together with existing
ground-based near-infrared data, the JWST photometry are well fit by a BT-SETTL
atmospheric model from 1-16 $mu$m, and span $sim$97% of HIP 65426 b’s
luminous range. Independent of the choice of forward model atmosphere we
measure an empirical bolometric luminosity that is tightly constrained between
$mathrm{log}!left(L_mathrm{bol}/L_{odot}right)$=-4.35 to -4.21, which in
turn provides a robust mass constraint of 7.1$pm$1.1 $M_mathrm{Jup}$. In
totality, these observations confirm that JWST presents a powerful and exciting
opportunity to characterise the population of exoplanets amenable to direct
imaging in greater detail.

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