Reflecting on naked singularities: iron line fitting as a probe of the cosmic censorship conjecture

Abstract

We demonstrate that the X-ray iron line fitting technique can be leveraged as a powerful probe of the cosmic censorship conjecture. We do this by extending existing emission line models to arbitrary spin parameters of the Kerr metric, no longer restricted to black hole metrics with $|a_{\bullet }|<1$. We show that the emission lines from naked singularity metrics ($|a_{\bullet }|>1$) show significant differences to their black hole counterparts, even for those metrics with identical locations of the innermost stable circular orbit, i.e., emission line fitting does not suffer from the degeneracy which affects continuum fitting approaches. These differences are entirely attributable to the disappearance of the event horizon for $|a_{\bullet }|>1$. We highlight some novel emission line features of naked singularity metrics, such as ``inverted'' emission lines (with sharp red wings and extended blue wings) and ``triple lines''. The lack of detection of any of these novel features provides support of the cosmic censorship conjecture. We publicly release {\tt XSPEC} packages {\tt skline} and {\tt skconv} which can now be used to probe the cosmic censorship conjecture in Galactic X-ray binaries and Active Galactic Nuclei. The inclusion of super-extremal spacetimes can be alternatively posed as a way of stress-testing conventional models of accretion.

arXiv commentVersion accepted in MNRAS. 11 pages, 12 figures. XSPEC models available at https://github.com/andymummeryastro/superkerrline

References in corpus (40)

• Broad iron lines in Active Galactic Nuclei
• X-ray reflected spectra from accretion disk models. III. A complete grid of ionized reflection calculations
• Multi-Temperature Blackbody Spectrum of a Thin Accretion Disk around a Kerr Black Hole: Model Computations and Comparison with Observations
• Relativistic X-ray Lines from the Inner Accretion Disks Around Black Holes
• Irradiation of an Accretion Disc by a Jet: General Properties and Implications for Spin Measurements of Black Holes
• XMM-EPIC observation of MCG-6-30-15: Direct evidence for the extraction of energy from aspinning black hole?
• Broad emission lines for negatively spinning black holes
• Understanding X-ray reflection emissivity profiles in AGN: Locating the X-ray source
• Evidence for Spin and Energy Extraction in a Galactic Black Hole Candidate: The XMM-Newton/EPIC-pn Spectrum of XTE J1650-500
• The Masses and Spins of Neutron Stars and Stellar-Mass Black Holes
• A Fast New Public Code for Computing Photon Orbits in a Kerr Spacetime
• The Spin of Supermassive Black Holes
• Relativistic iron emission lines in neutron star low-mass X-ray binaries as probes of neutron star radii
• Appearance of Keplerian discs orbiting Kerr superspinars
• Towards precision measurements of accreting black holes using X-ray reflection spectroscopy
• Testing the Kerr black hole hypothesis using X-ray reflection spectroscopy
• The Reflection Component from Cygnus X-1 in the Soft State Measured by NuSTAR and Suzaku
• On the determination of the spin of the black hole in Cyg X-1 from X-ray reflection spectra
• Determination of the X-ray reflection emissivity profile of 1H 0707-495
• Astrophysical Violations of the Kerr Bound as a Possible Signature of String Theory
• The Soft State of Cygnus X-1 Observed with NuSTAR: A Variable Corona and a Stable Inner Disk
• A public relativistic transfer function model for X-ray reverberation mapping of accreting black holes
• Spectral Analysis of 1H0707-495 with XMM-Newton
• X-ray spectral evolution of GS 2023+338 (V404 Cyg) during decline after outburst
• A selection effect boosting the contribution from rapidly spinning black holes to the Cosmic X-ray Background
• Public Release of RELXILL_NK: A Relativistic Reflection Model for Testing Einstein's Gravity
• NuSTAR Observations of the Accreting Atolls GX 3+1, 4U 1702-429, 4U 0614+091, and 4U 1746-371
• A Systematic View of Ten New Black Hole Spins
• Re-estimating the Spin Parameter of the Black Hole in Cygnus X-1
• YNOGK: A new public code for calculating null geodesics in the Kerr spacetime
• Revealing the broad iron Kalpha line in Cygnus X-1 through simultaneous XMM-Newton, RXTE, and INTEGRAL observations
• Venturing beyond the ISCO: Detecting X-ray emission from the plunging regions around black holes
• Over-Rotating Black Holes, Godel Holography and the Hypertube
• Black hole spin: theory and observation
• Distinguishing black holes and naked singularities with iron line spectroscopy
• Accretion within the innermost stable circular orbit: analytical thermodynamic solutions in the adiabatic limit
• Observational Testability of Kerr bound in X-ray Spectrum of Black-Hole Candidates
• Relativistic reflection spectra of super-spinning black holes
• Magnetised accretion discs in Kerr spacetimes
• Testing theories of accretion and gravity with super-extremal Kerr discs

Cited by in corpus (2)

• Sgr A* Shadow Study with KTN Space Time and Investigation of NUT Charge Existence
• Scattering of massive particles from black holes and naked singularities