A high-sensitivity polarimeter using a ferro-electric liquid crystal modulator

Bailey, Jeremy; Kedziora-Chudczer, Lucyna; Cotton, Daniel V.; Bott, Kimberly; Hough, J. H.; Lucas, P. W.

doi:10.1093/mnras/stv519

Cited by 62 publications

(111 citation statements)

References 28 publications

(49 reference statements)

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“…Between September 2016 and April 2019 we also made 29 new high-precision polarimetric observations of α Oph in seven photometric bands with a variety of instrument and telescope configurations. The bulk of the observations were made using HIPPI (HIgh Precision Polarimetric Instrument, Bailey et al 2015) and its successor HIPPI-2 (Bailey et al 2020) at the 3.9-m Anglo-Australian Telescope (AAT) at Siding Spring Observatory. Two observations were made at the Gemini North telescope on Mauna Kea with HIPPI-2.…”

Section: Observationsmentioning

confidence: 99%

“…However, subsequent studies using more complete stellar-atmosphere models showed that the expected polarization was small at visible wavelengths (Collins 1970;Sonneborn 1982). It was not until the development of polarimeters that could measure linear polarization to parts-per-million (ppm) levels of precision (Hough et al E-mail: j.bailey@unsw.edu.au 2006; Bailey et al 2015) that the effect was detected (Bailey et al 2010) and confirmed by multiwavelength polarimetry and detailed modelling of the bright star Regulus (α Leo; Cotton et al 2017a).…”

Section: Introductionmentioning

confidence: 99%

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The rotation of α Oph investigated using polarimetry

Bailey

Cotton

Howarth

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Recently we have demonstrated that high-precision polarization observations can detect the polarization resulting from the rotational distortion of a rapidly rotating Btype star. Here we investigate the extension of this approach to an A-type star. Linearpolarization observations of α Oph (A5IV) have been obtained over wavelengths from 400 to 750 nm. They show the wavelength dependence expected for a rapidly-rotating star combined with a contribution from interstellar polarization. We model the observations by fitting rotating-star polarization models and adding additional constraints including a measured v e sin i. However, we cannot fully separate the effects of rotation rate and inclination, leaving a range of possible solutions. We determine a rotation rate (ω = Ω/Ω c ) between 0.83 and 0.98 and an axial inclination i > 60 • . The rotationaxis position angle is found to be 142 • ± 4 • , differing by 16 • from a value obtained by interferometry. This might be due to precession of the rotation axis due to interaction with the binary companion. Other parameters resulting from the analysis include a polar temperature T p = 8725 ± 175 K, polar gravity log g p = 3.93 ± 0.08 (dex cgs), and polar radius R p = 2.52 ± 0.06 R . Comparison with rotating-star evolutionary models indicates that α Oph is in the later half of its main-sequence evolution and must have had an initial ω of 0.8 or greater. The interstellar polarization has a maximum value at a wavelength (λ max ) of 440 ± 110 nm, consistent with values found for other nearby stars.

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Section: Observationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The rotation of α Oph investigated using polarimetry

Bailey

Cotton

Howarth

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…The 20th century data sets used in this analysis included the discovery of the ISMF within 40 pc of the Sun in the fourth galactic quadrant (ℓ = 270°-360°, Piirola 1977;Tinbergen 1982). More recently, high sensitivity polarimeters capable of 3σ detections of polarization strengths <0.01% have become available (Pereyra & Magalhães 2007;Wisniewski et al 2007;Bailey et al 2010Bailey et al , 2015Berdyugin et al 2014;Piirola et al 2014;.…”

Section: Polarization Data Used To Determine the Magnetic Field Direcmentioning

confidence: 99%

CHARTING THE INTERSTELLAR MAGNETIC FIELD CAUSING THEINTERSTELLAR BOUNDARY EXPLORER(IBEX) RIBBON OF ENERGETIC NEUTRAL ATOMS

Frisch

Berdyugin

Piirola

et al. 2015

ApJ

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The interstellar magnetic field (ISMF) near the heliosphere is a fundamental component of the solar galactic environment that can only be studied using polarized starlight. The results of an ongoing survey of the linear polarizations of local stars are analyzed with the goal of linking the ISMF that shapes the heliosphere to the nearby field in interstellar space. We present new results on the direction of the magnetic field within 40 pc obtained from analyzing polarization data using a merit function that determines the field direction that provides the best fit to the polarization data. Multiple magnetic components are identified, including a dominant interstellar field, B POL , that is aligned with the direction ℓ, b = 36°.2, 49°.0 (±16°.0). Stars tracing B POL have the same mean distance as stars that do not trace B POL , but show weaker average polarizations consistent with a smaller column density of polarizing material. B POL is aligned with the ISMF traced by the IBEX Ribbon to within 7.6 7.6 14.9 -+ degrees. The variations in the polarization position angle directions derived from the data that best match B POL indicate a low level of magnetic turbulence, ∼9°±1°. The direction of B POL is obtained after excluding polarization data tracing a separate magnetic structure that appears to be associated with interstellar dust deflected around the heliosphere. The velocities of local interstellar clouds relative to the Local Standard of Rest (LSR) increase with the angles between the LSR velocities and B POL , indicating that the kinematics of local interstellar material is ordered by the ISMF. The Loop I superbubble that extends close to the Sun contains dust that reddens starlight and whose distance is determined by the color excess E(B − V) of starlight. Polarizations caused by grains aligned with respect to B POL are consistent with the location of the Sun in the rim of the Loop I superbubble. An angle of 76.8 27.6 23.5 -+ between B POL and the bulk LSR velocity the local interstellar material indicates a geometry that is consistent with an expanding superbubble. The efficiency of grain alignment in the local interstellar medium has been assessed using stars where both polarization data and hydrogen column density data are available. Nearby stars appear to have larger polarizations than expected based on reddened sightlines, which is consistent with previous results, but uncertainties are large. Optical polarization and color excess E(B − V) data indicate the presence of nearby interstellar dust in the BICEP2 field. Color excess E(B − V) indicates an optical extinction of A V >0.6 in the BICEP2 field, while the polarization data indicate that A V >0.09 mag. The IBEX Ribbon ISMF extends to the boundaries of the BICEP2 region.

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“…Moreover, the "instant" readout allows one to use PMT with the fast polarization modulator such as PEM or FLC. Not surprisingly, the PMT detectors have been used in the most precise polarimeters such as HIPPI (Bailey et al, 2015) and POLISH2 (Wiktorowicz and Nofi, 2015). The major disadvantage of the PMT detectors is their relatively low quantum efficiency which is typically in the range 10-30%.…”

Section: Detectors For Optical Polarimetry: Photomultiplier Tubesmentioning

confidence: 99%

“…HIPPI, a successor to PlanetPol (Bailey et al, 2015), employs the FLC modulator, operated at the frequency of 500 Hz, and PMT detectors. Unlike PlanetPol, it is optimized for high-precision polarimetry in the blue wavelengths, in the spectral region ∼ 400-700 nm.…”

Section: High-precision Double-image Polarimeters With High-frequencymentioning

confidence: 99%

Optical Polarimetry: Methods, Instruments and Calibration Techniques

Berdyugin

Piirola

Poutanen

2019

Astrophysics and Space Science Library

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In this chapter we present a brief summary of methods, instruments and calibration techniques used in modern astronomical polarimetry in the optical wavelengths. We describe the properties of various polarization devices and detectors used for optical broadband, imaging and spectropolarimetry, and discuss their advantages and disadvantages. The necessity of a proper calibration of the raw polarization data is emphasized and methods of the determination and subtraction of instrumental polarization are considered. We also present a few examples of high-precision measurements of optical polarization of black hole X-ray binaries and massive binary stars made with our DiPol-2 polarimeter, which allowed us to constrain the sources of optical emission in black hole X-ray binaries and measure orbital parameters of massive stellar binaries.

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A high-sensitivity polarimeter using a ferro-electric liquid crystal modulator

Cited by 62 publications

References 28 publications

The rotation of α Oph investigated using polarimetry

The rotation of α Oph investigated using polarimetry

CHARTING THE INTERSTELLAR MAGNETIC FIELD CAUSING THEINTERSTELLAR BOUNDARY EXPLORER(IBEX) RIBBON OF ENERGETIC NEUTRAL ATOMS

Optical Polarimetry: Methods, Instruments and Calibration Techniques

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