Discovery of powerful millisecond flares from Cygnus X-1

Abstract

We have found a large number of very strong flares in the available XTE PCA data of Cyg X-1 (also seen in available HEXTE and BATSE data) with 13 flares satisfying our chosen threshold criterion, occuring both in the hard and the soft states. We analyze here in detail two of them. The strongest one took place in the soft state, with the 3-30 keV energy flux increasing 30 times with respect to the preceding 16-s average. The e-folding time is ~ 7 ms for the main flare and ~ 1 ms for its precursor. The spectrum strongly hardens during the flare. On the other hand, flares in the hard state have generally lower amplitudes and longer e-folding times, and their spectra soften during the flare, with the hardness of the spectrum at the flare peak similar for both types of the flares. The presence of the flares shows unusually dramatic events taking place in the accretion flow of Cyg X-1. On the other hand, the rate of occurence of hard-state flares shows they may represent a high-flux end of the distribution of shots present in usual lightcurves of Cyg X-1.

Accepted for publication in MNRAS

References in corpus (5)

• The Soft Gamma-Ray Spectral Variability of Cygnus X-1
• Understanding the long-term spectral variability of Cygnus X-1 with BATSE and ASM observations
• Accretion of low angular momentum material onto black holes: 2D magnetohydrodynamical case
• Global Three-Dimensional Simulations of Black Hole Accretion Disks: X-ray Flares in the Plunging Region
• The X-ray/gamma-ray spectrum of XTE J1550--564 in the very high state

Cited by in corpus (30)

• Non-linear X-ray variability in X-ray binaries and active galaxies
• Investigating a Fluctuating-accretion Model for the Spectral-timing Properties of Accreting Black Hole Systems
• Very High Energy Gamma-ray Radiation from the Stellar-mass Black Hole Cygnus X-1
• Long Term Variability of Cygnus X-1. IV. Spectral Evolution 1999-2004
• Radiative magnetic reconnection near accreting black holes
• Long Term Variability of Cyg X-1, II. The rms-Flux Relation
• High-energy gamma-ray emission from Cyg X-1 measured by Fermi and its theoretical implications
• Periodic long-term X-ray and radio variability of Cygnus X-1
• Long Term X-ray Monitoring Of The TeV Binary LS I +61 303 with RXTE
• SAX J1808.4-3658 and the origin of X-ray variability in X-ray binaries and active galactic nuclei
• Gamma-ray observations of Cygnus X-1 above 100 MeV in the hard and soft states
• Spinning black holes magnetically connected to a Keplerian disk -- Magnetosphere, reconnection sheet, particle acceleration and coronal heating
• An intense state of hard X-ray emission of Cyg X-1 observed by INTEGRAL coincident with TeV measurements
• Observations of giant outbursts from Cygnus X-1
• Black hole Spin Measurement Based on Time-domain VLBI Observations of Infalling Gas Cloud
• Radiative plasma simulations of black hole accretion flow coronae in the hard and soft states
• New method for black-hole spin measurement based on flux variation from an infalling gas ring
• Doppler disc tomography applied to low mass AGN spin
• Wavelet analysis of millisecond variability of Cygnus X-1 during its failed state transition
• Damped harmonic oscillator interpretation of the soft-state power spectra of Cyg X-1
• Viscous propagation of mass flow variability in accretion discs
• Hard X-ray/Soft gamma-ray experiments and missions: overview and prospects
• Similar phenomena at different scales: Black Holes, the Sun, Gamma-ray Bursts, Supernovae, Galaxies and Galaxy Clusters
• Time Domain Studies of X-ray Shot Noise in Cygnus X-1
• Fast Spectral Variability from Cygnus X-1
• High-energy Emission from Turbulent Electron-ion Coronae of Accreting Black Holes
• A year-long AGILE observation of Cygnus X-1 in hard spectral state
• Simultaneous optical and X-ray high speed photometry of Cyg X-2
• Unprecedentedly bright X-ray flaring in Cygnus X-1 observed by INTEGRAL
• Pair-Regulated Klein-Nishina Relativistic Magnetic Reconnection with Applications to Blazars and Accreting Black Holes