Linear line spectropolarimetry of Herbig Ae/Be stars

TL;DR

This paper demonstrates that spectropolarimetry can resolve the inner accretion regions of Herbig Ae/Be stars, revealing rotational modulation effects and providing insights into star formation and angular momentum evolution.

Contribution

It introduces a novel application of spectropolarimetry to map the 3D geometry of accreting gas in Herbig Ae/Be stars and tests theories of their angular momentum evolution.

Findings

Spectropolarimetry can detect changes in polarization on rotational timescales.

Monte Carlo simulations show how accretion column visibility affects polarization.

Rotational modulation is key to understanding mass accretion variability.

Abstract

Accretion is the prime mode of star formation, but the exact mode has not yet been identified in the Herbig Ae/Be mass range. We provide evidence that the the maximum variation in mass-accretion rate is reached on a rotational timescale, which suggests that rotational modulation is the key to understanding mass accretion. We show how spectropolarimetry is uniquely capable of resolving the innermost (within 0.1 AU) regions between the star and the disk, allowing us to map the 3D geometry of the accreting gas, and test theories of angular momentum evolution. We present Monte Carlo line-emission simulations showing how one would observe changes in the polarisation properties on rotational timescales, as accretion columns come and go into our line of sight.