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

Cotton, Daniel V. ; Bailey, Jeremy ; Kedziora-Chudczer, Lucyna ; Bott, Kimberly ; De Horta, Ain Y. ; Filcek, Normandy ; Marshall, Jonathan P. ; Melville, Graeme ; Buzasi, Derek L. and Boiko, Ievgeniia , et al. (2024) In Monthly Notices of the Royal Astronomical Society 535(2). p.1586-1615
Abstract

Observations of polarization position angle (θ) 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 band) observations from many observing runs and re-determine θ 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... (More)

Observations of polarization position angle (θ) 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 band) observations from many observing runs and re-determine θ 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 Car, o Sco, HD 154445, HD 161056, and ι1 Sco, which are stable to ≤0.123◦ . Position angle variability of 0.27–0.82◦ , significant at the 3σ 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 α 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 < 0.1◦ precision in the telescope position angle with similar instrumentation, and allow data sets to be combined more accurately.

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organization
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type
Contribution to journal
publication status
published
subject
keywords
instrumentation: polarimeters, supergiants, techniques: polarimetric
in
Monthly Notices of the Royal Astronomical Society
volume
535
issue
2
pages
30 pages
publisher
Oxford University Press
external identifiers
  • scopus:85209770976
ISSN
0035-8711
DOI
10.1093/mnras/stae2418
language
English
LU publication?
yes
additional info
Publisher Copyright: © 2024 The Author(s).
id
998ca0a4-5708-48d2-a99b-eadd160b4126
date added to LUP
2025-01-09 10:51:29
date last changed
2025-04-04 15:24:52
@article{998ca0a4-5708-48d2-a99b-eadd160b4126,
  abstract     = {{<p>Observations of polarization position angle (θ) 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 band) observations from many observing runs and re-determine θ 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 Car, o Sco, HD 154445, HD 161056, and ι<sup>1</sup> Sco, which are stable to ≤0.123<sup>◦</sup> . Position angle variability of 0.27–0.82<sup>◦</sup> , significant at the 3σ 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 α 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<sup>◦</sup> precision in the telescope position angle with similar instrumentation, and allow data sets to be combined more accurately.</p>}},
  author       = {{Cotton, Daniel V. and Bailey, Jeremy and Kedziora-Chudczer, Lucyna and Bott, Kimberly and De Horta, Ain Y. and Filcek, Normandy and Marshall, Jonathan P. and Melville, Graeme and Buzasi, Derek L. and Boiko, Ievgeniia and Borsato, Nicholas W. and Perkins, Jean and Opitz, Daniela and Melrose, Shannon and Grüning, Gesa and Evensberget, Dag and Zhao, Jinglin}},
  issn         = {{0035-8711}},
  keywords     = {{instrumentation: polarimeters; supergiants; techniques: polarimetric}},
  language     = {{eng}},
  month        = {{12}},
  number       = {{2}},
  pages        = {{1586--1615}},
  publisher    = {{Oxford University Press}},
  series       = {{Monthly Notices of the Royal Astronomical Society}},
  title        = {{Polarization position angle standard stars : a reassessment of θ and its variability for seventeen stars based on a decade of observations}},
  url          = {{http://dx.doi.org/10.1093/mnras/stae2418}},
  doi          = {{10.1093/mnras/stae2418}},
  volume       = {{535}},
  year         = {{2024}},
}