Pulsars, transients and relativistic astrophysics

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Accretion and outflow in V404 Cyg

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 488:1 (2019) 1356-1365

Authors:

J Casares, T Muñoz-Darias, D Mata Sánchez, PA Charles, MAP Torres, M Armas Padilla, RP Fender, J García-Rojas
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An X-ray reverberation mass measurement of Cygnus X-1

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 488:1 (2019) 348-361

Authors:

Guglielmo Mastroserio, Adam Ingram, Michiel van der Klis

Abstract:

ABSTRACT We present the first X-ray reverberation mass measurement of a stellar-mass black hole. Accreting stellar-mass and supermassive black holes display characteristic spectral features resulting from reprocessing of hard X-rays by the accretion disc, such as an Fe Kα line and a Compton hump. This emission probes the innermost region of the accretion disc through general relativistic distortions to the line profile. However, these spectral distortions are insensitive to black hole mass, since they depend on disc geometry in units of gravitational radii. Measuring the reverberation lag resulting from the difference in path-length between direct and reflected emission calibrates the absolute length of the gravitational radius. We use a relativistic model able to reproduce the behaviour of the lags as a function of energy for a wide range of variability time-scales, addressing both the reverberation lags on short time-scales and the intrinsic hard lags on longer time-scales. We jointly fit the time-averaged spectrum and the real and imaginary parts of the cross-spectrum as a function of energy for a range of Fourier frequencies to Rossi X-ray Timing Exporer data from the X-ray binary Cygnus X-1. We also show that introducing a self-consistently calculated radial ionisation profile in the disc improves the fit, but requires us to impose an upper limit on ionization profile peak to allow a plausible value of the accretion disc density. This limit leads to a mass value more consistent with the existing dynamical measurement.
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A review of quasi-periodic oscillations from black hole X-ray binaries: Observation and theory

New Astronomy Reviews Elsevier 85 (2019) 101524

Authors:

Adam R Ingram, Sara E Motta
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Error formulae for the energy-dependent cross-spectrum

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) (2019)
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TeraHertz Exploration and Zooming-in for Astrophysics (THEZA): ESA Voyage 2050 White Paper

(2019)

Authors:

Leonid I Gurvits, Zsolt Paragi, Viviana Casasola, John Conway, Jordy Davelaar, Heino Falcke, Rob Fender, Sándor Frey, Christian M Fromm, Cristina García Miró, Michael A Garrett, Marcello Giroletti, Ciriaco Goddi, José-Luis Gómez, Jeffrey van der Gucht, José Carlos Guirado, Zoltán Haiman, Frank Helmich, Elizabeth Humphreys, Violette Impellizzeri, Michael Kramer, Michael Lindqvist, Hendrik Linz, Elisabetta Liuzzo, Andrei P Lobanov, Yosuke Mizuno, Luciano Rezzolla, Freek Roelofs, Eduardo Ros, Kazi LJ Rygl, Tuomas Savolainen, Karl Schuster, Tiziana Venturi, Martina Wiedner, J Anton Zensus
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