Polarization position angle standard stars: a reassessment of θ and its variability for seventeen stars based on a decade of observations

ABSTRACT Observations of polarization position angle ($\theta$) standards made from 2014 to 2023 with the High Precision Polarimetric Instrument (HIPPI) and other HIPPI-class polarimeters in both hemispheres are used to investigate their variability. Multiband data were first used to thoroughly recalibrate the instrument performance by bench-marking against carefully selected literature data. A novel co-ordinate difference matrix (CDM) approach – which combines pairs of points – was then used to amalgamate monochromatic ($g^\prime$ band) observations from many observing runs and re-determine $\theta$ for 17 standard stars. The CDM algorithm was then integrated into a fitting routine and used to establish the impact of stellar variability on the measured position angle scatter. The approach yields variability detections for stars on long time-scales that appear stable over short runs. The best position angle standards are $\ell$ Car, o Sco, HD 154445, HD 161056, and $\iota ^1$ Sco, which are stable to $\le$0.123$^\circ$. Position angle variability of 0.27–0.82$^\circ$, significant at the 3$\sigma$ level, is found for 5 standards, including the Luminous Blue Variable HD 160529 and all but one of the other B/A-type supergiants (HD 80558, HD 111613, HD 183143, and 55 Cyg), most of which also appear likely to be variable in polarization magnitude (p) – there is no preferred orientation for the polarization in these objects, which are all classified as $\alpha$ Cygni variables. Despite this we make six key recommendations for observers – relating to data acquisition, processing and reporting – that will allow them to use these standards to achieve $\lt $ 0.1$^\circ$ precision in the telescope position angle with similar instrumentation, and allow data sets to be combined more accurately.

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Publication Details

Journal
Monthly Notices of the Royal Astronomical Society
Published
2024-10-24
DOI
https://doi.org/10.1093/mnras/stae2418
Citations
2
Primary Topic
Stellar, planetary, and galactic studies
Type
article
Field-Weighted Citation Impact
0.66

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article

Polarization position angle standard stars: a reassessment of θ and its variability for seventeen stars based on a decade of observations

Lucyna Kedziora‐Chudczer, Kimberly Bott, Daniel V. Cotton, Gesa Grüning et al.
2 citations
Monthly Notices of the Royal Astronomical Society
Stellar, planetary, and galactic studies
0.66
article

Polarization position angle standard stars: a reassessment of θ and its variability for seventeen stars based on a decade of observations

Lucyna Kedziora‐Chudczer, Kimberly Bott, Daniel V. Cotton, Gesa Grüning, Jean Perkins, Ievgeniia Boiko, Jinglin Zhao, J. P. Marshall, Graeme Melville, A. Y. De Horta, Jeremy Bailey, Daniela Opitz, Derek L. Buzasi, Dag Evensberget, Nicholas W. Borsato, Shannon Melrose, Normandy Filcek
article en
2 citations

Abstract

ABSTRACT Observations of polarization position angle ($\theta$) standards made from 2014 to 2023 with the High Precision Polarimetric Instrument (HIPPI) and other HIPPI-class polarimeters in both hemispheres are used to investigate their variability. Multiband data were first used to thoroughly recalibrate the instrument performance by bench-marking against carefully selected literature data. A novel co-ordinate difference matrix (CDM) approach – which combines pairs of points – was then used to amalgamate monochromatic ($g^\prime$ band) observations from many observing runs and re-determine $\theta$ for 17 standard stars. The CDM algorithm was then integrated into a fitting routine and used to establish the impact of stellar variability on the measured position angle scatter. The approach yields variability detections for stars on long time-scales that appear stable over short runs. The best position angle standards are $\ell$ Car, o Sco, HD 154445, HD 161056, and $\iota ^1$ Sco, which are stable to $\le$0.123$^\circ$. Position angle variability of 0.27–0.82$^\circ$, significant at the 3$\sigma$ level, is found for 5 standards, including the Luminous Blue Variable HD 160529 and all but one of the other B/A-type supergiants (HD 80558, HD 111613, HD 183143, and 55 Cyg), most of which also appear likely to be variable in polarization magnitude (p) – there is no preferred orientation for the polarization in these objects, which are all classified as $\alpha$ Cygni variables. Despite this we make six key recommendations for observers – relating to data acquisition, processing and reporting – that will allow them to use these standards to achieve $\lt $ 0.1$^\circ$ precision in the telescope position angle with similar instrumentation, and allow data sets to be combined more accurately.

Monthly Notices of the Royal Astronomical SocietyVol. 535(2)
University of California, Riverside (US), University of Central Florida (US), Leiden University (NL), Monterey Institute for Research in Astronomy (US), Carl von Ossietzky Universität Oldenburg (DE), Pennsylvania State University (US), Institute of Astronomy and Astrophysics, Academia Sinica (TW), Universidad del Desarrollo (CL), Willamette University (US), University of Southern Queensland (AU), Monterey Peninsula College (US), Lund University (SE), University of Washington (US), University of Wollongong (AU), Florida Gulf Coast University (US), UNSW Sydney (AU), California State University, Long Beach (US), Western Sydney University (AU), Macquarie University (AU)
National Aeronautics and Space Administration, University of New South Wales, Western Sydney University, National Science and Technology Council, Australian Astronomical Optics-Macquarie
Openalex Percentile: Top 27%
Stellar, planetary, and galactic studies
0.66
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