Long term variability of Cygnus X-1 V. State definitions with all sky monitors

Journal article

Publication Details

Author(s): Grinberg V, Hell N, Pottschmidt K, Boeck M, Nowak MA, Rodriguez J, Bodaghee A, Bel MC, Case GL, Hanke M, Kühnel M, Markoff SB, Pooley GG, Rothschild RE, Tomsick JA, Wilson-Hodge CA, Wilms J
Journal: Astronomy & Astrophysics
Publication year: 2013
Volume: 554
ISSN: 0004-6361


We present a scheme for determining the spectral state of the canonical black hole Cyg X-1 using data from previous and current X-ray all sky monitors (RXTE-ASM, Swift-BAT, MAXI, and Fermi-GBM). Determinations of the hard/intermediate and soft state agree to better than 10% between different monitors, facilitating the determination of the state and its context for any observation of the source, potentially over the lifetimes of different individual monitors. A separation of the hard and the intermediate states, which strongly differ in their spectral shape and short-term timing behavior, is only possible when data in the soft X-rays (<5 keV) are available. A statistical analysis of the states confirms the different activity patterns of the source (e.g., month- to year-long hard-state periods or phases during which numerous transitions occur). It also shows that the hard and soft states are stable, with the probability of Cyg X-1 remaining in a given state for at least one week to be larger than 85% in the hard state and larger than 75% in the soft state. Intermediate states are short lived, with a 50% probability that the source leaves the intermediate state within three days. Reliable detection of these potentially short-lived events is only possible with monitor data that have a time resolution better than 1 d.

FAU Authors / FAU Editors

Grinberg, Victoria
Dr.Karl-Remeis-Sternwarte Bamberg, Astronomisches Institut
Hanke, Manfred
Dr.Karl-Remeis-Sternwarte Bamberg, Astronomisches Institut
Hell, Natalie
Dr.Karl-Remeis-Sternwarte Bamberg, Astronomisches Institut
Wilms, Jörn Prof. Dr.
Professur für Astronomie und Astrophysik

External institutions with authors

European Space Astronomy Centre (ESAC)
La Sierra University
Massachusetts Institute of Technology (MIT)
Max-Planck-Institut für Radioastronomie / Max Planck Institute for Radio Astronomy
National Aeronautics and Space Administration (NASA)
University of California, Berkeley
University of California, San Diego
University of Cambridge
University of Maryland, Baltimore County
University of Paris 7 - Denis Diderot / Université Paris VII Denis Diderot

Last updated on 2019-08-06 at 05:08