Next Article in Journal
Planets, Planetary Nebulae, and Intermediate Luminosity Optical Transients (ILOTs)
Next Article in Special Issue
Hard X-ray and Soft Gamma Ray Polarimetry with CdTe/CZT Spectro-Imager
Previous Article in Journal
Large-Scale Features of the Radio Sky and a Model for Loop I
Previous Article in Special Issue
Instrumentation and Future Missions in the Upcoming Era of X-ray Polarimetry
Article Menu
Issue 2 (June) cover image

Export Article

Open AccessFeature PaperArticle

Probing Black Hole Magnetic Fields with QED

Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, Canada
Author to whom correspondence should be addressed.
Galaxies 2018, 6(2), 57;
Received: 18 March 2018 / Revised: 11 May 2018 / Accepted: 20 May 2018 / Published: 24 May 2018
(This article belongs to the Special Issue The Bright Future of Astronomical X-ray Polarimetry)
PDF [493 KB, uploaded 24 May 2018]


The effect of vacuum birefringence is one of the first predictions of quantum electrodynamics (QED): the presence of a charged Dirac field makes the vacuum birefringent when threaded by magnetic fields. This effect, extremely weak for terrestrial magnetic fields, becomes important for highly magnetized astrophysical objects, such as accreting black holes. In the X-ray regime, the polarization of photons traveling in the magnetosphere of a black hole is not frozen at emission but is changed by the local magnetic field. We show that, for photons traveling along the plane of the disk, where the field is expected to be partially organized, this results in a depolarization of the X-ray radiation. Because the amount of depolarization depends on the strength of the magnetic field, this effect can provide a way to probe the magnetic field in black-hole accretion disks and to study the role of magnetic fields in astrophysical accretion in general. View Full-Text
Keywords: black holes; X-ray polarization; quantum electrodynamics; radiative corrections; magnetic field black holes; X-ray polarization; quantum electrodynamics; radiative corrections; magnetic field

Figure 1

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

Share & Cite This Article

MDPI and ACS Style

Caiazzo, I.; Heyl, J. Probing Black Hole Magnetic Fields with QED. Galaxies 2018, 6, 57.

Show more citation formats Show less citations formats

Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Related Articles

Article Metrics

Article Access Statistics



[Return to top]
Galaxies EISSN 2075-4434 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top