2020A&A...633A..64V


C.D.S. - SIMBAD4 rel 1.7 - 2021.04.21CEST07:09:19

2020A&A...633A..64V - Astronomy and Astrophysics, volume 633A, 64-64 (2020/1-1)

Polarimetric imaging mode of VLT/SPHERE/IRDIS. II. Characterization and correction of instrumental polarization effects,

VAN HOLSTEIN R.G., GIRARD J.H., DE BOER J., SNIK F., MILLI J., STAM D.M., GINSKI C., MOUILLET D., WAHHAJ Z., SCHMID H.M., KELLER C.U., LANGLOIS M., DOHLEN K., VIGAN A., POHL A., CARBILLET M., FANTINEL D., MAUREL D., ORIGNE A., PETIT C., RAMOS J., RIGAL F., SEVIN A., BOCCALETTI A., LE COROLLER H., DOMINIK C., HENNING T., LAGADEC E., MENARD F., TURATTO M., UDRY S., CHAUVIN G., FELDT M. and BEUZIT J.-L.

Abstract (from CDS):


Context. Circumstellar disks and self-luminous giant exoplanets or companion brown dwarfs can be characterized through direct-imaging polarimetry at near-infrared wavelengths. SPHERE/IRDIS at the Very Large Telescope has the capabilities to perform such measurements, but uncalibrated instrumental polarization effects limit the attainable polarimetric accuracy.
Aims. We aim to characterize and correct the instrumental polarization effects of the complete optical system, that is, the telescope and SPHERE/IRDIS.
Methods. We created a detailed Mueller matrix model in the broadband filters Y, J, H, and Ks and calibrated the model using measurements with SPHERE's internal light source and observations of two unpolarized stars. We developed a data-reduction method that uses the model to correct for the instrumental polarization effects, and applied it to observations of the circumstellar disk of T Cha.
Results. The instrumental polarization is almost exclusively produced by the telescope and SPHERE's first mirror and varies with telescope altitude angle. The crosstalk primarily originates from the image derotator (K-mirror). At some orientations, the derotator causes severe loss of signal (>90% loss in the H- and Ks-band) and strongly offsets the angle of linear polarization. With our correction method we reach, in all filters, a total polarimetric accuracy of ≤0.1% in the degree of linear polarization and an accuracy of a few degrees in angle of linear polarization.
Conclusions. The correction method enables us to accurately measure the polarized intensity and angle of linear polarization of circumstellar disks, and is a vital tool for detecting spatially unresolved (inner) disks and measuring the polarization of substellar companions. We have incorporated the correction method in a highly-automated end-to-end data-reduction pipeline called IRDAP, which we made publicly available online.

Abstract Copyright: © ESO 2020

Journal keyword(s): polarization - techniques: polarimetric - techniques: high angular resolution - techniques: image processing - methods: observational - protoplanetary disks

Simbad objects: 11

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Number of rows : 11

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 V* CE Ant TT* 10 42 30.1021269333 -33 40 16.226774953   12.21 10.91   9.10 M2Ve 161 1
2 V* TW Hya TT* 11 01 51.9054298616 -34 42 17.031550898   11.94 10.50 10.626 9.18 K6Ve 1613 1
3 V* CS Cha Or* 11 02 24.8849252208 -77 33 35.683462615   12.88 11.69   10.123 K2Ve 201 0
4 NAME Cha 1 MoC 11 06 48 -77 18.0           ~ 1014 1
5 V* DZ Cha LM* 11 49 31.8520891363 -78 51 01.058647109     12.832   10.732 M0Ve 67 0
6 V* T Cha Or* 11 57 13.5268556629 -79 21 31.521755129   10.00 11.86     K0e 242 1
7 CD-40 8434 TT* 14 08 10.1545137760 -41 23 52.576649494   13.42 12.18 11.71 10.506 K7IVe 151 0
8 V* PZ Tel BY* 18 53 05.8733807460 -50 10 49.901380086   9.22 8.342   7.464 G9IV 296 0
9 HD 176425 * 19 02 08.5215364642 -41 54 37.822053716   6.199 6.209     A0V 29 0
10 HD 217343 PM* 23 00 19.2872945687 -26 09 13.506860661   8.12 7.48   6.75 G5V 99 0
11 HD 218396 El* 23 07 28.7156905667 +21 08 03.302133882   6.21 5.953     F0+VkA5mA5 947 0

    Equat.    Gal    SGal    Ecl

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