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|Title:||New constraints on the disk characteristics and companion candidates around T Chamaeleontis with VLT/SPHERE||Authors:||Pohl, A.
van Holstein, R. G.
Maire, A. -L.
van Boekel, R.
de Boer, J.
Lagrange, A. -M.
|Issue Date:||2017||Journal:||ASTRONOMY & ASTROPHYSICS||Number:||605||First Page:||A34||Abstract:||Context. The transition disk around the T Tauri star T Cha possesses a large gap, making it a prime target for high-resolution imaging in the context of planet formation. <BR /> Aims: We aim to find signs of disk evolutionary processes by studying the disk geometry and the dust grain properties at its surface, and to search for companion candidates. <BR /> Methods: We analyze a set of VLT/SPHERE data at near-infrared and optical wavelengths. We performed polarimetric imaging of T Cha with IRDIS (1.6 μm) and ZIMPOL (0.5-0.9 μm), and obtained intensity images from IRDIS dual-band imaging with simultaneous spectro-imaging with IFS (0.9-1.3 μm). <BR /> Results: The disk around T Cha is detected in all observing modes and its outer disk is resolved in scattered light with unprecedented angular resolution and signal-to-noise. The images reveal a highly inclined disk with a noticeable east-west brightness asymmetry. The significant amount of non-azimuthal polarization signal in the U<SUB>φ</SUB> images, with a U<SUB>φ</SUB>/Q<SUB>φ</SUB> peak-to-peak value of 14%, is in accordance with theoretical studies on multiple scattering in an inclined disk. Our optimal axisymmetric radiative transfer model considers two coplanar inner and outer disks, separated by a gap of 0.̋28 ( 30 au) in size, which is larger than previously thought. We derive a disk inclination of 69 deg and PA of 114 deg. In order to self-consistently reproduce the intensity and polarimetric images, the dust grains, responsible for the scattered light, need to be dominated by sizes of around ten microns. A point source is detected at an angular distance of 3.5'' from the central star. It is, however, found not to be co-moving. <BR /> Conclusions: We confirm that the dominant source of emission is forward scattered light from the near edge of the outer disk. Our point source analysis rules out the presence of a companion with mass larger than 8.5 M<SUB>jup</SUB> between 0.̋1 and 0.̋3. The detection limit decreases to 2 M<SUB>jup</SUB> for 0.̋3 to 4.0''. <P />Based on observations made with European Southern Observatory (ESO) telescopes at the Paranal Observatory in Chile, under program IDs 095.C-0298(B), 096.C-0248(B) and 096.C-0248(C).||URI:||http://hdl.handle.net/20.500.12386/26811||URL:||https://www.aanda.org/articles/aa/abs/2017/09/aa30234-16/aa30234-16.html||ISSN:||0004-6361||DOI:||10.1051/0004-6361/201630234||Bibcode ADS:||2017A&A...605A..34P||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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checked on Jan 28, 2021
checked on Jan 28, 2021
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