The polarization of Sigma Orionis E - A curious eclipsing binary

Kemp, J. C.; Herman, L. C.

doi:10.1086/155733

Cited by 23 publications

(16 citation statements)

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“…The primary method of analysis employed in this work is χ 2 fitting of the multi-band measurements to Serkowski curves. For this we use the Python language's 'scipy' package (Jones et al 2001 ), specifically the 'curve fit' function.…”

Section: Discussionmentioning

confidence: 99%

The wavelength dependence of interstellar polarization in the Local Hot Bubble

Cotton

Marshall

Frisch

et al. 2018

Monthly Notices of the Royal Astronomical Society

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The properties of dust in the interstellar medium (ISM) nearest the Sun are poorly understood because the low column densities of dust toward nearby stars induce little photometric reddening, rendering the grains largely undetectable. Stellar polarimetry offers one pathway to deducing the properties of this diffuse material. Here we present multi-wavelength aperture polarimetry measurements of seven bright stars chosen to probe interstellar polarization near the edge of the Local Hot Bubble (LHB) -an amorphous region of relatively low density interstellar gas and dust extending ∼70-150 pc from the Sun. The measurements were taken using the HIgh Precision Polarimetric Instrument (HIPPI) on the 3.9-m Anglo-Australian Telescope. HIPPI is an aperture stellar polarimeter with a demonstrated sensitivity of 4.3 parts-per-million (ppm). Of the stars observed two are polarized to a much greater degree than the others; they have a wavelength of maximum polarization (λ max ) of ∼550 ± 20 nm -similar to that of stars beyond the LHB -and we conclude that they are in the wall of the LHB. The remaining five stars have polarizations of ∼70 to 160 ppm, of these four have a much bluer λ max , ∼350 ± 50 nm. Bluer values of λ max may indicate grains shocked during the evolution of the Loop I Superbubble. The remaining star, HD 4150 is not well fit by a Serkowski curve, and may be intrinsically polarized.

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Section: Discussionmentioning

confidence: 99%

The wavelength dependence of interstellar polarization in the Local Hot Bubble

Cotton

Marshall

Frisch

et al. 2018

Monthly Notices of the Royal Astronomical Society

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“…These findings, however, stand contrary to a number of observational results indicating that σ Ori E is a bona fide member of the cluster rather than a background star. The reddening of σ Ori E is the same as σ Ori AB (Sherry et al 2008), and likewise for the interstellar polarization (Kemp & Herman 1977;Carciofi et al 2013). The radial velocity and proper motion of σ Ori E are indistinguishable from those of the cluster (Caballero 2007).…”

Section: Discussionmentioning

confidence: 99%

MOSTOBSERVATIONS OF σ Ori E: CHALLENGING THE CENTRIFUGAL BREAKOUT NARRATIVE

Townsend

Rivinius

Rowe

et al. 2013

ApJ

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We present results from three weeks' photometric monitoring of the magnetic helium-strong star σ Ori E using the MOST microsatellite. The star's light curve is dominated by twice-per-rotation eclipse-like dimmings arising when magnetospheric clouds transit across and occult the stellar disk. However, no evidence is found for any abrupt centrifugal breakout of plasma from the magnetosphere, either in the residual flux or in the depths of the light minima. Motivated by this finding we compare the observationally inferred magnetospheric mass against that predicted by a breakout analysis. The large discrepancy between the values leads us to argue that centrifugal breakout does not play a significant role in establishing the magnetospheric mass budget of σ Ori E.

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“…This bright star is characterized by rapid rotation, a strong magnetic field, and variable circumstellar Hα emission. Observations show modulation according to the 1.19 d rotation period in longitudinal magnetic field (Landstreet & Borra 1978), Hα emission (Walborn 1974), He line strength (Pedersen & Thomsen 1977), photometry (Hesser, Walborn & Ugarte 1976), UV line strength (Smith & Groote 2001), 6‐cm radio emission (Leone & Umana 1993), and linear polarization (Kemp & Herman 1977). σ Ori E has long been known as the prototypical magnetic Bp star.…”

Section: Introductionmentioning

confidence: 99%

Revisiting the Rigidly Rotating Magnetosphere model for Ori E - I. Observations and data analysis★

Oksala¹,

Wade²,

Townsend³

et al. 2011

Monthly Notices of the Royal Astronomical Society

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We have obtained 18 new high‐resolution spectropolarimetric observations of the B2Vp star σ Ori E with both the Narval and ESPaDOnS spectropolarimeters. The aim of these observations is to test, with modern data, the assumptions of the Rigidly Rotating Magnetosphere (RRM) model of Townsend & Owocki, applied to the specific case of σ Ori E by Townsend, Owocki & Groote. This model includes a substantially offset dipole magnetic field configuration, and approximately reproduces previous observational variations in longitudinal field strength, photometric brightness and Hα emission. We analyse new spectroscopy, including H i, He i, C ii, Si iii and Fe iii lines, confirming the diversity of variability in photospheric lines, as well as the double S‐wave variation of circumstellar hydrogen. Using the multiline analysis method of least‐squares deconvolution (LSD), new, more precise longitudinal magnetic field measurements reveal a substantial variance between the shapes of the observed and RRM model time‐varying field. The phase‐resolved Stokes V profiles of He i 5876 and 6678 Å lines are fitted poorly by synthetic profiles computed from the magnetic topology assumed by Townsend et al.. These results challenge the offset dipole field configuration assumed in the application of the RRM model to σ Ori E, and indicate that future models of its magnetic field should also include complex, higher order components.

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The polarization of Sigma Orionis E - A curious eclipsing binary

Cited by 23 publications

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The wavelength dependence of interstellar polarization in the Local Hot Bubble

The wavelength dependence of interstellar polarization in the Local Hot Bubble

MOSTOBSERVATIONS OF σ Ori E: CHALLENGING THE CENTRIFUGAL BREAKOUT NARRATIVE

Revisiting the Rigidly Rotating Magnetosphere model for Ori E - I. Observations and data analysis★

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