Unprecedentedly bright X-ray flaring in Cygnus X-1 observed by INTEGRAL

Thalhammer P, Bouchet T, Rodriguez J, Cangemi F, Pottschmidt K, Green DA, Rhodes L, Ferrigno C, Nowak MA, Grinberg V, Siegert T, Laurent P, Kreykenbohm I, Perucho M, Tomsick J, Sánchez-Fernández C, Wilms J (2025)

Publication Type: Journal article

Publication year: 2025

Journal

Astronomy & Astrophysics EDP Sciences

Book Volume: 703

Article Number: A109

DOI: 10.1051/0004-6361/202453573

Abstract

We study three extraordinarily bright X-ray flares originating from Cyg X-1 seen on July 10, 2023, detected with INTEGRAL. The flares had a duration on the order of only ten minutes each, and within seconds reached a 1–100 keV peak luminosity of 1.1 − 2.6 × 1038 erg s−1. The associated INTEGRAL/IBIS count rate was approximately ten times higher than usual for the hard state. To our knowledge, this is the first time that such strong flaring has been seen in Cyg X-1, despite the more than 21 years of INTEGRAL monitoring – with almost ∼20 Ms of exposure – and the similarly deep monitoring with RXTE/PCA from 1997 to 2012. The flares were seen in all three X-ray and γ-ray instruments of INTEGRAL. Radio monitoring by the AMI Large Array with observations 6 h before and 40 h after the X-ray flares did not detect a corresponding increase in radio flux. The shape of the X-ray spectrum shows only marginal change during the flares, i.e., photon index and cut-off energy are largely preserved. The overall flaring behavior points toward a sudden and brief release of energy either due to the ejection of material in an unstable jet or due to the interaction of the jet with the ambient clumpy stellar wind.

Authors with CRIS profile

Philipp Thalhammer Dr.Karl-Remeis-Sternwarte Bamberg, Astronomisches Institut Ingo Kreykenbohm Dr.Karl-Remeis-Sternwarte Bamberg, Astronomisches Institut Jörn Wilms Professur für Astronomie und Astrophysik

Involved external institutions

Université Paris-Saclay FR France (FR) Université Sorbonne Paris Cité FR France (FR) National Aeronautics and Space Administration (NASA) US United States (USA) (US) University of Cambridge GB United Kingdom (GB) University of Oxford GB United Kingdom (GB) University of Geneva / Université de Genève (UNIGE) CH Switzerland (CH) Washington University in St. Louis US United States (USA) (US) University of València / Universitat de València ES Spain (ES) European Space Astronomy Centre (ESAC) ES Spain (ES) Julius-Maximilians-Universität Würzburg DE Germany (DE) European Space Research and Technology Centre (ESTEC, ESA) NL Netherlands (NL)

How to cite

APA:

Thalhammer, P., Bouchet, T., Rodriguez, J., Cangemi, F., Pottschmidt, K., Green, D.A.,... Wilms, J. (2025). Unprecedentedly bright X-ray flaring in Cygnus X-1 observed by INTEGRAL. Astronomy & Astrophysics, 703. https://doi.org/10.1051/0004-6361/202453573

MLA:

Thalhammer, Philipp, et al. "Unprecedentedly bright X-ray flaring in Cygnus X-1 observed by INTEGRAL." Astronomy & Astrophysics 703 (2025).

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