A New Mechanism for Polarizing Light from Obscured Stars

Abstract

Recent spectropolarimetric observations of Herbig AeBe stellar systems show linear polarization variability with wavelength and epoch near their obscured H-alpha emission. Surprisingly, this polarization is not coincident with the H-alpha emission peak but is variable near the absorptive part of the line profile. With a new and novel model we show here that this is evidence of optical pumping - anisotropy of the incident radiation that leads to a linear polarization-dependent optical depth within the intervening hydrogen wind or disk cloud. This effect can yield a larger polarization signal than scattering polarization in these systems.

Submitted to ApJ Letters

References in corpus (3)

• Polarimetric line profiles for scattering off rotating disks
• Polarization from aligned atoms as a diagnostics of circumstellar, AGN and interstellar magnetic fields: II. Atoms with Hyperfine Structure
• The Hanle Effect as a Diagnostic of Magnetic Fields in Stellar Envelopes IV. Application to Polarized P Cygni Wind Lines

Cited by in corpus (15)

• Rotating massive O stars with non-spherical 2D winds
• On the presence and absence of disks around O-type stars
• Atomic alignment and Diagnostics of Magnetic Fields in Diffuse Media
• Spectropolarimetric Observations of Herbig Ae/Be Stars. II. Comparison of Spectropolarimetric Surveys: HAeBe, Be and Other Emission-Line Stars
• On the alignment between the circumstellar disks and orbital planes of Herbig Ae/Be binary systems
• Tracing Magnetic Fields with Ground State Alignment
• Shock-Induced Polarized Hydrogen Emission Lines in the Mira Star omicron Ceti
• Spectropolarimetric observations of Herbig Ae/Be Stars I: HiVIS spectropolarimetric calibration and reduction techniques
• Ubiquitous H-alpha polarized line profiles: absorptive spectropolarimetric effects and temporal variability in Post-AGB, Herbig Ae/Be and other stellar types
• Diagnosis of 3D magnetic field and modes composition in MHD turbulence with Y-parameter
• Linear spectropolarimetry across the optical spectrum of Herbig Ae/Be stars
• Linear line spectropolarimetry of Herbig Ae/Be stars
• Calibrating and Stabilizing Spectropolarimeters with Charge Shuffling and Daytime Sky Measurements
• The Hanle Effect as a Diagnostic of Magnetic Fields in Stellar Envelopes. V. Thin Lines from Keplerian Disks
• The solar-like "Second Spectrum" and the polarised metal lines in emission of the post-AGB binary 89 Herculis