Explanipedia

The rapidly changing period of the QPE source 1ES 1927+654 Open

A. R. King · 2025

Several low-mass galaxy nuclei are observed to produce quasi-periodic eruptions (QPEs). Recently one of these systems, 1ES 1927+654, changed its quasi-period drastically, from ∼18 to ∼7.1 min, over a span of just 2 yr. I suggest that this …

Joining the dots: high redshift black holes Open

A. R. King · 2024

A recent paper suggested that emission from the central supermassive black holes in high-redshift galaxies must be tightly collimated by the effects of partly expelling a super-Eddington mass supply. I show here that this idea predicts tha…

Joining the Dots: High Redshift Black holes Open

A. R. King · 2024

A recent paper (King, 2024) suggested that emission from the central supermassive black holes in high-redshift galaxies must be tightly collimated by the effects of partly expelling a super-Eddington mass supply. I show here that this idea…

The Perils of Pdot Open

A. R. King, J. P. Lasota · 2024

Schaefer (2024) has recently published observations of binary period derivatives $\dot P$ for 52 cataclysmic variables, and concluded that these strongly conflict with all proposed evolutionary pictures for these systems. We point out once…

The black hole masses of high-redshift QSOs Open

A. R. King · 2024

Observations of high-redshift quasars frequently promote suggestions of large black hole masses, whose presence so early in cosmic time is not easily explicable. I consider the parallel with ultraluminous X-ray sources (ULXs) – now known t…

The Black-Hole Masses of High-Redshift QSOs Open

A. R. King · 2024

Observations of high-redshift quasars frequently promote suggestions of large black hole masses, whose presence so early in cosmic time is not easily explicable. I consider the parallel with ultraluminous X-ray sources (ULXs) -- now known …

Supermassive Black Hole Winds in X-rays: SUBWAYS Open

V. E. Gianolli, S. Bianchi, P-O Petrucci, M. Brusa, G. Chartas , et al. · 2024

The detection of blueshifted absorption lines likely associated with ionized iron K-shell transitions in the X-ray spectra of many active galactic nuclei (AGNs) suggests the presence of a highly ionized gas outflowing with mildly relativis…

SN 2022jli: The ultraluminous birth of a low-mass X-ray binary Open

A. R. King, J. P. Lasota · 2024

Observations show that the 12.4 d binary system descending from the recent supernova SN 2022jli closely fits hypotheses of how low-mass X-ray binaries form, but requires an apparently super-Eddington accretion luminosity from the accreting…

Ultraluminous X-ray sources are beamed Open

J. P. Lasota, A. R. King · 2023

We show that magnetar models for ultraluminous X-ray sources (ULXs) have serious internal inconsistencies. The magnetic fields required to increase the limiting luminosity for radiation pressure above the observed (assumed isotropic) lumin…

Why are Quasiperiodic Eruptions only Found in Low-Mass Galaxies? Open

A. R. King · 2023

I consider the current sample of galaxy nuclei producing quasiperiodic eruptions (QPEs). If the quasiperiod results from the orbital motion of a star around the central black hole, the dearth of associated black hole masses $\gtrsim 10^6\m…

Why are quasi-periodic eruptions only found in low-mass galaxies? Open

A. R. King · 2023

I consider the current sample of galaxy nuclei producing quasi-periodic eruptions (QPEs). If the quasi-period results from the orbital motion of a star around the central black hole, the dearth of associated black hole masses ≳106 M⊙ place…

QPE or QPO? – Quasiperiodic activity in low-mass galaxy nuclei Open

A. R. King · 2023

Quasiperiodic eruptions (QPEs) from low-mass galaxy centres may result from accretion from a white dwarf in a very eccentric orbit about the central massive black hole. Evolution under gravitational radiation losses reduces the separation …

QPE or QPO? -- Quasiperiodic Activity in Low-Mass Galaxy Nuclei Open

A. R. King · 2023

Quasiperiodic eruptions (QPEs) from low-mass galaxy centres may result from accretion from a white dwarf in a very eccentric orbit about the central massive black hole. Evolution under gravitational radiation losses reduces the separation …

Supermassive Black Holes Open

A. R. King · 2023

Written by an international leader in the field, this is a coherent and accessible account of the concepts that are now vital for understanding cutting-edge work on supermassive black holes. These include accretion disc misalignment, disc …

The role of root hairs in root water uptake - Insights from an image-based 3D model Open

Patrick Duddek, Mutez Ali Ahmed, Mathieu Javaux, Jan Vanderborght, Goran Lovrić , et al. · 2023

Root hairs, tubular protrusions of epidermal root cells, are considered a key rhizosphere feature: by substantially increasing the contact area between roots and soil, they enhance the ability of plants to capture soil resources. Hence, th…

Melting properties and melting phase relations of the Martian mantle from in-situ measurements on iron-rich mineralogical assemblages Open

Rémy Pierru, Serena Dominijanni, Paraskevas Parisiadis, Léon Andriambariarijaona, Bin Zhao , et al. · 2023

Mars’ mantle dynamical history has certainly been dominated by a stagnant-lid regime, with limited mixing and homogenization. Accordingly, the chemical and mineralogical signatures of early processes, including the crystallization of…

Angular Momentum Transfer in QPEs from Galaxy Nuclei Open

A. R. King · 2023

A suggested model for quasi--periodic eruptions (QPEs) from galaxy nuclei invokes a white dwarf in an eccentric orbit about the central massive black hole. I point out that the extreme mass ratio allows the presence of strong Lindblad reso…

Ultraluminous X-ray sources Open

A. R. King, J. P. Lasota, Matthew Middleton · 2023

Angular momentum transfer in QPEs from galaxy nuclei Open

A. R. King · 2022

A suggested model for quasi-periodic eruptions (QPEs) from galaxy nuclei invokes a white dwarf in an eccentric orbit about the central massive black hole. I point out that the extreme mass ratio allows the presence of strong Lindblad reson…

Supermassive Black Hole Winds in X-rays: SUBWAYS Open

G. A. Matzeu, M. Brusa, G. Lanzuisi, M. Dadina, S. Bianchi , et al. · 2022

We present a new X-ray spectroscopic study of 22 luminous (2 × 10 45 ≲ L bol /erg s −1 ≲ 2 × 10 46 ) active galactic nuclei (AGNs) at intermediate redshifts (0.1 ≲ z ≲ 0.4), as part of the SUpermassive Black hole Winds in the x-rAYS (SUBWA…

Supermassive Black Hole Winds in X-rays: SUBWAYS Open

M. Mehdipour, G. A. Kriss, M. Brusa, G. A. Matzeu, M. Gaspari , et al. · 2022

We present a UV spectroscopic study of ionized outflows in 21 active galactic nuclei (AGN), observed with the Hubble Space Telescope (HST). The targets of the Supermassive Black Hole Winds in X-rays (SUBWAYS) sample were selected with the …

Quasi-periodic eruptions from galaxy nuclei Open

A. R. King · 2022

I consider quasi-periodic eruptions (QPEs) from galaxy nuclei. All the known cases fit naturally into a picture of accretion from white dwarfs (WDs) in highly eccentric orbits about the central black holes which decay through gravitational…

AGN light echoes and the accretion disc self-gravity limit Open

A. Lobban, A. R. King · 2022

Accretion disc theory predicts that an AGN disc becomes self-gravitating and breaks up into stars at an outer radius Rsg ≃ 12 light-days, with effectively no free parameter. We present evidence that the longest observed AGN light echoes ar…

One for the Future: measuring the mass transfer rate in the ULX M82 X-2 by using orbital period changes will take millenia Open

A. R. King, J. P. Lasota · 2021

Bachetti et al. (2021) have recently claimed to measure the mass transfer rate in the pulsing ULX system M82 X-2 by following the change of its orbital period over 7 yr. We reiterate the known point that this method cannot give a reliable …

Can the Blandford–Znajek Mechanism Power Steady Jets? Open

A. R. King, J. E. Pringle · 2021

We consider the Blandford-Znajek (BZ) mechanism for extracting black hole spin energy to drive astrophysical jets. Analyses of the BZ mechanism generally take no account of any electric charge on the black hole. But, as noted by Wald and o…

High-redshift SMBHs can grow from stellar-mass seeds via chaotic accretion Open

Kastytis Zubovas, A. R. King · 2021

Extremely massive black holes, with masses $M_{\rm BH} \gt 10^9 {\, \rm M_{\odot }}$, have been observed at ever higher redshifts. These results create ever tighter constraints on the formation and growth mechanisms of early black holes. H…

Dwarf galaxies and the black hole scaling relations Open

A. R. King, Rebecca Nealon · 2020

The sample of dwarf galaxies with measured central black hole masses M and velocity dispersions σ has recently doubled, and gives a close fit to the extrapolation of the M - σ relation for more massive galaxies. We argue that this is diffi…

Hydrodynamical Simulations of Misaligned Accretion Discs in Binary Systems: Companions tear discs Open

Suzan Doğan, C. J. Nixon, A. R. King, J. E. Pringle, D. Price · 2020

Accretion discs appear in many astrophysical systems. In most cases, these discs are probably not completely axisymmetric. Discs in binary systems are often found to be misaligned with respect to the binary orbit. In this case, the gravita…

Pulsing and non-pulsing ULXs: the iceberg emerges Open

A. R. King, J. P. Lasota · 2020

We show that ultraluminous X-ray sources (ULXs) with coherent X-ray pulsing (PULXs) probably have neutron-star spin axes significantly misaligned from their central accretion discs. Scattering in the funnels collimating their emission and …

GSN 069 – A tidal disruption near miss Open

A. R. King · 2020

I suggest that the quasi-periodic ultrasoft X-ray eruptions recently observed from the galaxy GSN 069 may result from accretion from a low-mass white dwarf in a highly eccentric orbit about its central black hole. At $0.21\,\rm M_{\odot }$…

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