An Inexpensive Liquid Crystal Spectropolarimeter for the Dominion Astrophysical Observatory Plaskett Telescope

Monin, D.; Bohlender, D.; Hardy, Tim; Saddlemyer, Leslie; Fletcher, Murray

doi:10.1086/665582

Cited by 18 publications

(17 citation statements)

References 27 publications

(42 reference statements)

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“…Twenty-four medium-resolution spectropolarimetric observations were obtained with dimaPol (R 10 000) installed at the Dominion Astrophysical Observatory (DAO) (Monin et al 2012) from Feb. 7, 2009to Feb. 15, 2012 Two of these observations had SNRs 100 and were removed from the analysis. The remaining twenty-two Stokes V observations of Hβ were used to derive longitudinal field measurements; the HJDs, exposure times, SNRs, and longitudinal field measurements are listed in Table 2.…”

Section: Dimapol Spectropolarimetrymentioning

confidence: 99%

HD 35502: a hierarchical triple system with a magnetic B5IVpe primary

Sikora

Wade

Bohlender

et al. 2016

Mon. Not. R. Astron. Soc.

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We present our analysis of HD 35502 based on high-and medium-resolution spectropolarimetric observations. Our results indicate that the magnetic B5IVsnp star is the primary component of a spectroscopic triple system and that it has an effective temperature of 18.4 ± 0.6 kK, a mass of 5.7 ± 0.6 M , and a polar radius of 3.0 +1.1 −0.5 R . The two secondary components are found to be essentially identical A-type stars for which we derive effective temperatures (8.9 ± 0.3 kK), masses (2.1 ± 0.2 M ), and radii (2.1±0.4 R ). We infer a hierarchical orbital configuration for the system in which the secondary components form a tight binary with an orbital period of 5.66866(6) d that orbits the primary component with a period of over 40 yrs. Least-Squares Deconvolution (LSD) profiles reveal Zeeman signatures in Stokes V indicative of a longitudinal magnetic field produced by the B star ranging from approximately −4 to 0 kG with a median uncertainty of 0.4 kG. These measurements, along with the line variability produced by strong emission in Hα, are used to derive a rotational period of 0.853807(3) d. We find that the measured v sin i = 75 ± 5 km s −1 of the B star then implies an inclination angle of the star's rotation axis to the line of sight of 24 +6 −10°. Assuming the Oblique Rotator Model, we derive the magnetic field strength of the B star's dipolar component (14 +9 −3 kG) and its obliquity (63 ± 13°). Furthermore, we demonstrate that the calculated Alfvén radius (41 +17 −6 R * ) and Kepler radius (2.1 +0.4 −0.7 R * ) place HD 35502's central B star well within the regime of centrifugal magnetosphere-hosting stars.

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Section: Dimapol Spectropolarimetrymentioning

confidence: 99%

HD 35502: a hierarchical triple system with a magnetic B5IVpe primary

Sikora

Wade

Bohlender

et al. 2016

Mon. Not. R. Astron. Soc.

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“…The switching can be done at rates up to 100 Hz. The accuracy of polarization measurements is improved by a factor of 2 or more when more than 30 switch cycles are executed (for details see Monin et al 2012). have been used in solar polarimeters before but as far as we know dimaPol is the first night time polarimeter to use such a plate.…”

Section: What Is Dimapol?mentioning

confidence: 99%

The DAO Liquid Crystal Spectropolarimeter dimaPol

Monin¹,

Bohlender²,

Hardy³

et al. 2014

Proc. IAU

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The spectropolarimeter dimaPol measures circular polarization in spectral lines of stellar objects. The instrument is used to simultaneously detect polarization signals in the hydrogen Hβ line as well as nearby metallic lines. A fast switching ferro-electric liquid crystal waveplate synchronized with charge shuffling on the CCD is employed to greatly reduce instrumental systematics. dimaPol has been in use on the DAO 1.8-m Plaskett telescope since 2007. In this presentation we show the capabilities of the instrument as well as some of the main results obtained with it to date.

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“…Although this method of deriving B z from the hydrogen lines relies on the same basic assumptions as the widely used photopolarimetric technique of Angel & Landstreet (1970), it is not equivalent to the latter method because it is applied to narrow cores of the hydrogen lines instead of the Stark-broadened wings. At the same time, our differential technique is more similar to the hydrogen line measurement approach used by Kudryavtsev & Romanyuk (2012) and Monin et al (2012).…”

Section: Longitudinal Field From the Hydrogen Line Coresmentioning

confidence: 99%

Three-dimensional magnetic and abundance mapping of the cool Ap star HD 24712

Rusomarov

Kochukhov

Piskunov

et al. 2013

A&A

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Context. High-resolution spectropolarimetric observations provide simultaneous information about stellar magnetic field topologies and three-dimensional distributions of chemical elements. High-quality spectra in the Stokes IQUV parameters are currently available for very few early-type magnetic chemically peculiar stars. Here we present analysis of a unique full Stokes vector spectropolarimetric data set, acquired for the cool magnetic Ap star HD 24712 with a recently commissioned spectropolarimeter. Aims. The goal of our work is to examine the circular and linear polarization signatures inside spectral lines and to study variation of the stellar spectrum and magnetic observables as a function of rotational phase. Methods. HD 24712 was observed with the HARPSpol instrument at the 3.6-m ESO telescope over a period of 2010-2011. We achieved full rotational phase coverage with 43 individual Stokes parameter observations. The resulting spectra have a signal-to-noise ratio of 300-600 and resolving power exceeding 10 5 . The multiline technique of least-squares deconvolution (LSD) was applied to combine information from the spectral lines of Fe-peak and rare earth elements. Results. We used the HARPSPol spectra of HD 24712 to study the morphology of the Stokes profile shapes in individual spectral lines and in LSD Stokes profiles corresponding to different line masks. From the LSD Stokes V profiles we measured the longitudinal component of the magnetic field, B z , with an accuracy of 5-10 G. We also determined the net linear polarization from the LSD Stokes Q and U profiles. Combining previous B z measurements with our data allowed us to determine an improved rotational period of the star, P rot = 12.45812 ± 0.00019 d. We also measured the longitudinal magnetic field from the cores of Hα and Hβ lines. The analysis of B z measurements showed no evidence for a significant radial magnetic field gradient in the atmosphere of HD 24712. We used our B z and net linear polarization measurements to determine parameters of the dipolar magnetic field topology. We found that magnetic observables can be reasonably well reproduced by the dipolar model, although significant discrepancies remain at certain rotational phases. We discovered rotational modulation of the Hα core and related it to a non-uniform surface distribution of rare earth elements.

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An Inexpensive Liquid Crystal Spectropolarimeter for the Dominion Astrophysical Observatory Plaskett Telescope

Cited by 18 publications

References 27 publications

HD 35502: a hierarchical triple system with a magnetic B5IVpe primary

HD 35502: a hierarchical triple system with a magnetic B5IVpe primary

The DAO Liquid Crystal Spectropolarimeter dimaPol

Three-dimensional magnetic and abundance mapping of the cool Ap star HD 24712

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