Searching for Hα-emitting sources in the gaps of five transitional disks. SPHERE/ZIMPOL high-contrast imaging
Journal
Date Issued
2022
Author(s)
Huélamo, N.
•
Chauvin, G.
•
Mendigutía, I.
•
Whelan, E.
•
•
Cugno, G.
•
Schmid, H. M.
•
de Gregorio-Monsalvo, I.
•
Zurlo, A.
•
Barrado, D.
•
Benisty, M.
•
Quanz, S. P.
•
Bouy, H.
•
Montesinos, B.
•
Beletsky, Y.
•
Szulagyi, J.
Abstract
(Pre-)transitional disks show gaps and cavities that can be related with
on-going planet formation. According to theory, young embedded planets can
accrete material from the circumplanetary and circumstellar disks, so that they
could be detected in accretion tracers, like the H$_{\alpha}$ emission line. In
this work, we present spectral angular differential imaging AO-assisted
observations of five (pre-)transitional disks obtained with SPHERE/ZIMPOL at
the Very Large Telescope (VLT). They were obtained in the H$_{\alpha}$ line and
the adjacent continuum. We have combined spectral and angular differential
imaging techniques to increase the contrast in the innermost regions close to
the star, and search for the signature of young accreting protoplanets. As a
result, the reduced images do not show any clear H$_{\alpha}$ point source
around any of the targets. We report faint H$_{\alpha}$ emissions around TW Hya
and HD163296: while the former is most probably an artifact related with a
spike, the nature of the latter remains unclear. The spectral and angular
differential images yield contrasts of 6--8 magnitudes at separations of $\sim$
100 mas from the central stars, except in the case of LkCa15, with values of
$\sim$3 mag. We have estimated upper limits to the accretion luminosity of
potential protoplanets, obtaining that planetary models provide an average
value of $L_{\rm acc} \sim 10^{-4}$ $L_{\odot}$ at 200 mas, which is $\sim$2
orders of magnitude higher than the $L_{\rm acc}$ estimated from the
extrapolation of the $L_{H_{\alpha}}$ - $L_{acc}$ stellar relationship. We
explain the lack of protoplanet detections as a combination of different
factors, like e.g. episodic accretion, extinction from the circumstellar and
circumplanetray disks, and/or a majority of low-mass, low-accreting planets.
Volume
668
Start page
A138
Issn Identifier
0004-6361
Rights
open.access
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