J/A+A/626/A54 HR4796A dust ring Stokes images (Milli+, 2019)
Optical polarised phase function of the HR4796A dust ring.
Milli J., Engler N., Schmid H.M., Olofsson J., Menard F., Kral Q.,
Boccaletti A., Thebault P., Choquet E., Mouillet D., Lagrange A.-M.,
Augereau J.-C., Pinte C., Chauvin G., Dominik C., Perrot C., Zurlo A.,
Henning T., Beuzit J.-L., Avenhaus H., Bazzon A., Moulin T., Llored M.,
Moeller-Nilsson O., Roelfsema R., Pragt J.
<Astron. Astrophys. 626, A54 (2019)>
=2019A&A...626A..54M 2019A&A...626A..54M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Polarization
Keywords: planet-disk interactions - techniques: high angular resolution -
techniques: polarimetric - scattering - stars: individual: HR4796A -
planetary systems
Abstract:
The scattering properties of the dust originating from debris discs
are still poorly known. The analysis of scattered light is however a
powerful remote-sensing tool to understand the physical properties of
dust particles orbiting other stars. Scattered light is indeed widely
used to characterise the properties of cometary dust in the solar
system.
We aim to measure the morphology and scattering properties of the dust
from the debris ring around HR4796A in polarised optical light.
We obtained high-contrast polarimetric images of HR4796A in the
wavelength range 600-900nm with the SPHERE/ZIMPOL instrument on the
Very Large Telescope. We measured for the first time the polarised
phase function of the dust in a debris system over a wide range of
scattering angles in the optical. We confirm that it is incompatible
with dust particles being compact spheres under the assumption of the
Mie theory, and propose alternative scenarios compatible with the
observations, such as particles with irregular surface roughness or
aggregate particles.
Description:
The fits files contain the final reduced images of Stokes Q_phi and
U_phi of HR4796A, obtained with the SPHERE ZIMPOL instrument in the
filter VBB on the night of 2016-05-24. The astrophysical signal of the
disc is contained in the Q_phi image while the U_phi image contains
only the noise. The images have a size of 400x400 pixels and are
expressed in mJy/arcsec^2 with a pixel size of 0.072 arcsec. These 2
images are presented in Fig. 2 of the associated article.
Objects:
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RA (2000) DE Designation(s)
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12 36 01.03 -39 52 10.2 HR 4796 = HD 109573
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 123 2 List of fits images
fits/* . 2 Individual fits images
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 22 I3 --- Nx Number of pixels along X-axis
24- 26 I3 --- Ny Number of pixels along Y-axis
28- 50 A23 "datime" Obs.date Observation date
52- 55 I4 Kibyte size Size of FITS file
57- 88 A32 --- FileName Name of FITS file, in subdirectory fits
90-123 A34 --- Title Title of the FITS file
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Acknowledgements:
Julien Milli, jmilli(at)eso.org
(End) Patricia Vannier [CDS] 09-May-2019