J/A+A/648/A110 HD142527 SPHERE polarimetric images (Hunziker+, 2021)
HD 142527: quantitative disk polarimetry with SPHERE.
Hunziker S., Schmid H.M., Ma J., Menard F., Avenhaus H., Boccaletti A.,
Beuzit J.L., Chauvin G., Dohlen K., Dominik C., Engler N., Ginski C.,
Gratton R., Henning T., Langlois M., Milli J., Mouillet D., Tschudi C.,
van Holstein R.G., Vigan A.
<Astron. Astrophys. 648, A110 (2021)>
=2021A&A...648A.110H 2021A&A...648A.110H (SIMBAD/NED BibCode)
ADC_Keywords: Stars, emission ; Polarization
Keywords: stars: individual: HD 142527 -
instrumentation: high angular resolution - techniques: polarimetric -
protoplanetary disks - polarization - scattering
Abstract:
We present high-precision photometry and polarimetry based on visual
and near-infrared imaging data for the protoplanetary disk surrounding
the Herbig Ae/Be star HD 142527, with a strong focus on determining the
light scattering parameters of the dust located at the surface of the
large outer disk.
We re-reduced existing polarimetric differential imaging data of
HD 142527 in the VBB (735nm) and H-band (1625nm) from the ZIMPOL and
IRDIS subinstruments of SPHERE at the VLT. With polarimetry and
photometry based on reference star differential imaging (RDI), we were
able to measure the linearly polarized intensity and the total
intensity of the light scattered by the circumstellar disk with high
precision. We used simple Monte Carlo simulations of multiple light
scattering by the disk surface to derive constraints for three
scattering parameters of the dust: the maximum polarization of the
scattered light Pmax, the asymmetry parameter g, and the
single-scattering albedo ω.
We measure a reflected total intensity of 51.4±1.5mJy and
206±12mJy and a polarized intensity of 11.3±0.3mJy and
55.1±3.3mJy in the VBB and H-band, respectively. We also find in the
visual range a degree of polarization that varies between 28% on the
far side of the disk and 17% on the near side. In the H-band, the
degree of polarization is consistently higher by about a factor of
1.2. The disk also shows a red color for the scattered light intensity
and the polarized intensity, which are about twice as high in the
near-infrared when compared to the visual. We determine with model
calculations the scattering properties of the dust particles and find
evidence for strong forward scattering (g ∝ 0.5-0.75),
relatively low single-scattering albedo (ω ∝ 0.2-0.5),
and high maximum polarization (Pmax ∝ 0.5-0.75) at the
surface on the far side of the disk for both observed wavelengths. The
optical parameters indicate the presence of large aggregate dust
particles, which are necessary to explain the high maximum
polarization, the strong forward-scattering nature of the dust, and
the observed red disk color.
Description:
The presented SPHERE/ZIMPOL and SPHERE/IRDIS images were taken in the
VBB and H-band filter, respectively. The images show the resulting
Qφ and Uφ results for both observations.
Objects:
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RA (2000) DE Designation(s)
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15 56 41.89 -42 19 23.2 HD142527 = HIP 78092
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 116 4 List of fits images
fits/* . 4 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- 23 I4 --- Nx Number of pixels along X-axis
25- 28 I4 --- Ny Number of pixels along Y-axis
30- 33 I4 Kibyte size Size of FITS file
35- 64 A30 --- FileName Name of FITS file, in subdirectory fits
66-116 A51 --- Title Title of the FITS file
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Acknowledgements:
Silvan Hunziker, silvan.hunziker(at)phys.ethz.ch
(End) Patricia Vannier [CDS] 22-Mar-2021