Phase-locked polarization by photospheric reflection in the semidetached eclipsing binary ${\mu }^1$ Sco

Abstract

We report the detection of phase-locked polarization in the bright ($m_V$=2.98-3.24) semidetached eclipsing binary ${\mu }^1$ Sco (HD 151890). The phenomenon was observed in multiple photometric bands using two different HIPPI-class (HIgh Precision Polarimetric Instrument)polarimeters with telescopes ranging in size from 35-cm to 3.9-m. The peak-to-trough amplitude of the polarization is wavelength dependent and large, $\sim$700 parts-per-million in green light, and is easily seen with even the smallest telescope. We fit the polarization phase curve with a SYNSPEC/VLIDORT polarized radiative transfer model and a Wilson-Devinney geometric formalism, which we describe in detail. Light from each star reflected by the photosphere of the other, together with a much smaller contribution from tidal distortion and eclipse effects, wholly accounts for the polarization amplitude. In the past polarization in semidetached binaries has been attributed mostly to scattering from extra-stellar gas. Our new interpretation facilitates determining masses of such stars in non-eclipsing systems.

16 pages, 8 figures, 8 tables. Accepted to MNRAS

References in corpus (9)

• Binary Population and Spectral Synthesis Version 2.1: construction, observational verification and new results
• Southern Massive Stars at High Angular Resolution: Observational Campaign and Companion Detection
• New Grids of ATLAS9 Model Atmospheres
• A high-sensitivity polarimeter using a ferro-electric liquid crystal modulator
• HIPPI-2: A Versatile High Precision Polarimeter
• A high precision polarimeter for small telescopes
• Absolute Parameters of YOung Stars: GG Lup and mu^1 Sco
• Polarization measurements of the polluted white dwarf G29-38
• The polarization of the binary system Spica, and the reflection of light from stars

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