Venturing beyond the ISCO: Detecting X-ray emission from the plunging regions around black holes

Abstract

We explore how X-ray reverberation around black holes may reveal the presence of the innermost stable circular orbit (ISCO), predicted by General Relativity, and probe the dynamics of the plunging region between the ISCO and the event horizon. Being able to directly detect the presence of the ISCO and probe the dynamics of material plunging through the event horizon represents a unique test of general relativity in the strong field regime. X-ray reverberation off of the accretion disc and material in the plunging region is modelled using general relativistic ray tracing simulations. X-ray reverberation from the plunging region has a minimal effect on the time-averaged X-ray spectrum and the overall lag-energy spectrum, but is manifested in the lag in the highest frequency Fourier components, above 0.01 c^3 (GM)^-1 (scaled for the mass of the black hole) in the 2-4keV energy band for a non-spinning black hole or the 1-2keV energy band for a maximally spinning black hole. The plunging region is distinguished from disc emission not just by the energy shifts characteristic of plunging orbits, but by the rapid increase in ionisation of material through the plunging region. Detection requires measurement of time lags to an accuracy of 20 per cent at these frequencies. Improving accuracy to 12 per cent will enable constraints to be placed on the dynamics of material in the plunging region and distinguish plunging orbits from material remaining on stable circular orbits, confirming the existence of the ISCO, a prime discovery space for future X-ray missions.

arXiv comment20 pages, 12 figures. Accepted for publication in MNRAS

References in corpus (34)

• First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
• Constraining Black Hole Spin Via X-ray Spectroscopy
• X-ray reverberation around accreting black holes
• X-ray reflected spectra from accretion disk models. I. Constant density atmospheres
• Simulations of Magnetized Disks Around Black Holes: Effects of Black Hole Spin, Disk Thickness, and Magnetic Field Geometry
• Magnetic Stress at the Marginally Stable Orbit: Altered Disk Structure, Radiation, and Black Hole Spin Evolution
• The corona contracts in a black-hole transient
• Understanding X-ray reflection emissivity profiles in AGN: Locating the X-ray source
• Measuring the Spins of Accreting Black Holes
• A global look at X-ray time lags in Seyfert Galaxies
• Iron fluorescence from within the innermost stable orbit of black hole accretion disks
• Broad iron L-line and X-ray reverberation in 1H0707-495
• Broad iron K-alpha emission lines as a diagnostic of black hole spin
• The Spin of Supermassive Black Holes
• High-Density Effects in X-ray Reflection Models from Accretion Disks
• X-ray iron line reverberation from black hole accretion disks
• Relativistic iron K X-ray Reverberation in NGC 4151
• Magnetically Driven Accretion Flows in the Kerr Metric IV: Dynamical Properties of the Inner Disk
• The NuSTAR spectrum of Mrk 335: Extreme relativistic effects within 2 gravitational radii of the event horizon?
• Modelling the broad Fe Kα reverberation in the AGN NGC 4151
• Determination of the X-ray reflection emissivity profile of 1H 0707-495
• Driving extreme variability: The evolving corona and evidence for jet launching in Markarian 335
• The Eye of the Storm: Light from the Inner Plunging Region of Black Hole Accretion Discs
• The 1.5 Ms Observing Campaign on IRAS 13224-3809: X-ray Spectral Analysis I
• The origin of the lag spectra observed in AGN: Reverberation and the propagation of X-ray source fluctuations
• Towards modelling X-ray reverberation in AGN: Piecing together the extended corona
• The high-Eddington NLS1 Ark 564 has the coolest corona
• Exploring The Effects Of Disk Thickness On The Black Hole Reflection Spectrum
• The remarkable X-ray variability of IRAS 13224-3809 I: The variability process
• A blurred reflection interpretation for the intermediate flux state in Mrk 335
• Origin of the X-ray disc-reflection steep radial emissivity
• Revealing structure and evolution within the corona of the Seyfert galaxy I Zw 1
• Multiple X-ray reflection from ionized slabs
• Steep X-ray reflection emissivity profiles in AGN as the result of radially-structured disc ionisation

Cited by in corpus (21)

• Towards precision measurements of accreting black holes using X-ray reflection spectroscopy
• Orbital mechanics and quasiperiodic oscillation resonances of black holes in Einstein-Æther theory
• Testing General Relativity with NuSTAR data of Galactic Black Holes
• A New Spin on an Old Black Hole: NuSTAR Spectroscopy of EXO 1846-031
• Returning radiation in strong gravity around black holes: Reverberation from the accretion disc
• Maximum Observable Blueshift from Circular Equatorial Kerr Orbiters
• Impact of the returning radiation on the analysis of the reflection spectra of black holes
• Null and time-like geodesics in Kerr-Newman black hole exterior
• Acceleration and cooling of the corona during X-ray flares from the Seyfert galaxy I Zw 1
• Modeling uncertainties in X-ray reflection spectroscopy measurements II: Impact of the radiation from the plunging region
• Accretion within the innermost stable circular orbit: analytical thermodynamic solutions in the adiabatic limit
• Impact of the reflection model on the estimate of the properties of accreting black holes
• The peculiar spectral evolution of the new X-ray transient MAXI J0637-430
• The X-ray Luminosity Function Evolution of Quasars and the Correlation Between the X-ray and Ultraviolet Luminosities
• Testing the Weak Equivalence Principle near black holes
• Relativistic X-ray reverberation from super-Eddington accretion flow
• Exploring higher order images with Fe K_α-lines from relativistic disks: black hole spin determination and bias
• A rapid black hole spin or emission from the plunging region?
• Reflecting on naked singularities: iron line fitting as a probe of the cosmic censorship conjecture
• Morphology of Relativistically Broadened Line Emission from Axisymmetric Equatorial Accretion Disks
• Polarization Signatures of Inspiraling Hotspots around Kerr Black Holes