Mapping Circumstellar Magnetic Fields of Late-type Evolved Stars with the Goldreich-Kylafis Effect: CARMA Observations at λ1.3 mm of R Crt and R Leo (original) (raw)
ADS
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Abstract
Mapping magnetic fields is the key to resolving the unclear physical picture of circumstellar magnetic fields in late-type evolved stars. Observations of linearly polarized emission from thermal molecular line transitions due to the Goldreich-Kylafis (G-K) effect provide valuable insights into the magnetic field geometry in these sources that are complementary to other key studies. In this paper, we present the detection of spectral-line polarization from both the thermal J = 2-1 CO line and the v = 1, J = 5-4 SiO maser line toward two thermal-pulsating asymptotic giant branch stars, R Crt and R Leo. The observed fractional linear polarization in the CO emission is measured as ml ∼ 3.1% and ml ∼ 9.7% for R Crt and R Leo, respectively. A circumstellar envelope (CSE) model profile and the associated parameters are estimated and used as input to a more detailed modeling of the predicted linear polarization expected from the G-K effect. The observed thermal line polarization level is consistent with the predicted results from the G-K model for R Crt; additional effects need to be considered for R Leo.
Publication:
The Astrophysical Journal
Pub Date:
August 2020
DOI:
arXiv:
Bibcode:
Keywords:
- Asymptotic giant branch stars;
- Polarimetry;
- Stellar magnetic fields;
- CO line emission;
- Circumstellar masers;
- 2100;
- 1278;
- 1610;
- 262;
- 240;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Astrophysics of Galaxies
E-Print:
doi:10.3847/1538-4357/aba122