Kavli Affiliate: Bruce Macintosh
| First 5 Authors: Shrishmoy Ray, Steph Sallum, Sasha Hinkley, Anand Sivamarakrishnan, Rachel Cooper
| Summary:
We present aperture masking interferometry (AMI) observations of the star HIP
65426 at $3.8,rm{mu m}$ as a part of the JWST Direct Imaging Early Release
Science (ERS) program obtained using the Near Infrared Imager and Slitless
Spectrograph (NIRISS) instrument. This mode provides access to very small inner
working angles (even separations slightly below the Michelson limit of
$0.5lambda/D$ for an interferometer), which are inaccessible with the
classical inner working angles of the JWST coronagraphs. When combined with
JWST’s unprecedented infrared sensitivity, this mode has the potential to probe
a new portion of parameter space across a wide array of astronomical
observations. Using this mode, we are able to achieve a $5sigma$ contrast of
$Delta m{sim}7.62{pm}0.13$ mag relative to the host star at separations
${gtrsim}0.07{"}$, and the contrast deteriorates steeply at separations
${lesssim}0.07{"}$. However, we detect no additional companions interior to
the known companion HIP 65426 b (at separation ${sim}0.82{"}$ or,
$87^{+108}_{-31},rm{au}$). Our observations thus rule out companions more
massive than $10{-}12,rm{M_{Jup}}$ at separations ${sim}10{-}20,rm{au}$
from HIP 65426, a region out of reach of ground or space-based coronagraphic
imaging. These observations confirm that the AMI mode on JWST is sensitive to
planetary mass companions at close-in separations (${gtrsim}0.07{"}$), even
for thousands of more distant stars at $sim$100 pc, in addition to the stars
in the nearby young moving groups as stated in previous works. This result will
allow the planning and successful execution of future observations to probe the
inner regions of nearby stellar systems, opening an essentially unexplored
parameter space.
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