Please use this identifier to cite or link to this item: http://hdl.handle.net/2248/8377
Title: Submillimeter-wavelength Polarimetry of IRC+10216
Authors: Andersson, B -G
Karoly, Janik
Bastien, Pierre
Archana Soam
Coude, Simon
Tahani, Mehrnoosh
Gordon, Michael S
Fox-Middleton, Sydney
Keywords: Circumstellar dust (236)
Magnetic fields (994)
Carbonaceous grains (201)
Asymptotic giant branch stars (2100)
Issue Date: 1-Mar-2024
Publisher: American Astronomical Society
Citation: The Astrophysical Journal, Vol. 963, No. 1, 76
Abstract: We present SCUBA-2/POL-2 850 μm polarimetric observations of the circumstellar envelope (CSE) of the carbon-rich asymptotic giant branch (AGB) star IRC+10216. Both far-IR (FIR) and optical polarization data indicate grains aligned with their long axis in the radial direction relative to the central star. The 850 μm polarization does not show this simple structure. The 850 μm data are indicative, albeit not conclusive, of a magnetic dipole geometry. Assuming such a simple dipole geometry, the resulting 850 μm polarization geometry is consistent with both Zeeman observations and small-scale structure in the CSE. While there is significant spectral-line polarization contained within the SCUBA-2 850 μm passband for the source, it is unlikely that our broadband polarization results are dominated by line polarization. To explain the required grain alignment, grain mineralogy effects, due to either fossil silicate grains from the earlier oxygen-rich AGB phase of the star or due to the incorporation of ferromagnetic inclusions in the largest grains, may play a role. We argue that the most likely explanation is due to a new alignment mechanism wherein a charged grain, moving relative to the magnetic field, precesses around the induced electric field and therefore aligns with the magnetic field. This mechanism is particularly attractive as the optical, FIR, and submillimeter-wave polarization of the carbon dust can then be explained in a consistent way, differing simply due to the charge state of the grains.
Description: Open Access.
Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
URI: http://hdl.handle.net/2248/8377
ISSN: 1538-4357
Appears in Collections:IIAP Publications

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