Testing the no-hair theorem with observations in the electromagnetic spectrum. IV. Relativistically broadened iron lines

Tim Johannsen, Dimitrios Psaltis

Research output: Contribution to journalArticle

80 Citations (Scopus)

Abstract

According to the no-hair theorem, astrophysical black holes are fully characterized by their masses and spins and are described by the Kerr metric. This theorem can be tested observationally by measuring (at least) three different multipole moments of the spacetimes of black holes. In this paper, we calculate the profiles of fluorescent iron lines emitted from the accretion flows around black hole candidates within a framework that allows us to perform the calculation as a function of its mass and spin as well as of a free parameter that measures potential deviations from the Kerr metric. We show that such deviations lead to line profiles that are significantly altered and may exhibit a modified flux ratio of the two peaks in their characteristic double-peaked shape. We also show that the disk inclination can be measured independently of the spin and the deviation parameter at low to intermediate inclination angles, as in the case of Kerr black holes. We estimate the precision that near-future X-ray missions such as Astro-H and ATHENA+ are required to achieve in order to resolve deviations from the Kerr metric in iron line profiles and show that constraints on such deviations will be strongest for rapidly spinning black holes. More generally, we show that measuring the line profile with a precision of ∼5% at disk inclinations of 30° or 60°constrains the deviation parameter to order unity for values of the spin a ≳ 0.5M.

Original languageEnglish (US)
Article number57
JournalAstrophysical Journal
Volume773
Issue number1
DOIs
StatePublished - Aug 10 2013

Fingerprint

electromagnetic spectra
hair
theorems
deviation
iron
inclination
profiles
accretion
metal spinning
multipoles
parameter
unity
astrophysics
moments
measuring
estimates
x rays

Keywords

  • accretion, accretion disks
  • black hole physics
  • galaxies: active
  • gravitation
  • line: profiles
  • relativistic processes

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Testing the no-hair theorem with observations in the electromagnetic spectrum. IV. Relativistically broadened iron lines. / Johannsen, Tim; Psaltis, Dimitrios.

In: Astrophysical Journal, Vol. 773, No. 1, 57, 10.08.2013.

Research output: Contribution to journalArticle

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