Searching for low-mass companions at small separations in transition disks with aperture masking interferometry
arxiv(2023)
摘要
Transition disks have large central cavities that have been spatially
resolved during recent years. Cavities and other substructures in circumstellar
disks are often interpreted as signposts to massive companions. We aim to
search for stellar and substellar companions in the central regions of
transition disks. We want to determine if these disks might be circumbinary in
their nature, similar to the HD 142527 system. We observed four systems, HD
100453, HD 100546, HD 135344 B, and PDS 70, with the sparse aperture masking
mode of VLT/SPHERE. We extracted the complex visibilities and bispectra from
the H2 and H3 imaging data. A binary model was fit to the closure phases to
search for companions and estimate detection limits. For validation, we also
analyzed four archival datasets of HD 142527 and inferred the orbital elements
and atmospheric parameters of its low-mass stellar companion. We have not
detected any significant point sources in the four observed systems. With a
contrast sensitivity of ≈0.004, we can rule out stellar companions down
to ≈2 au and partially explore the substellar regime at separations
≳3-5 au. The analysis of HD 142527 B revealed that its projected orbit
is aligned with dust features in the extended inner disk and that the orbit
could be close to coplanar with the outer disk. Atmospheric modeling confirms
the low-gravity and slightly reddened spectral appearance. The bulk parameters
are in agreement with dynamical constraints and evolutionary tracks. In
contrast to HD 142527, we find no evidence that a close-in stellar companion is
responsible for the resolved disk features of HD 100453, HD 100546, HD 135344
B, and PDS 70. Instead, the formation of giant planets or even low-mass brown
dwarfs could be shaping the innermost environment (≲20 au) of these
circumstellar disks, as is the case with the planetary system of PDS 70.
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