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

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 (2013)

Publication Status: Published

Publication Type: Journal article

Publication year: 2013

Journal

Publisher: EDP SCIENCES S A

Book Volume: 554

Article Number: ARTN A88

DOI: 10.1051/0004-6361/201321128

Abstract

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.

Authors with CRIS profile

Involved external institutions

University of Maryland, Baltimore County (UMBC) United States (USA) (US) University of California, Berkeley United States (USA) (US) University of Paris 7 - Denis Diderot / Université Paris VII Denis Diderot France (FR) Massachusetts Institute of Technology (MIT) United States (USA) (US) Max-Planck-Institut für Radioastronomie / Max Planck Institute for Radio Astronomy Germany (DE) La Sierra University United States (USA) (US) University of Cambridge United Kingdom (GB) National Aeronautics and Space Administration (NASA) United States (USA) (US) University of California, San Diego United States (USA) (US) European Space Astronomy Centre (ESAC) Spain (ES)

How to cite

APA:

Grinberg, V., Hell, N., Pottschmidt, K., Boeck, M., Nowak, M.A., Rodriguez, J.,... Wilms, J. (2013). Long term variability of Cygnus X-1 V. State definitions with all sky monitors. Astronomy & Astrophysics, 554. https://doi.org/10.1051/0004-6361/201321128

MLA:

Grinberg, Victoria, et al. "Long term variability of Cygnus X-1 V. State definitions with all sky monitors." Astronomy & Astrophysics 554 (2013).

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