High hard X-ray polarization in Cygnus X-1 confined to the intermediate hard state: evidence for a variable jet component

Abstract

Cygnus X-1, the well-known accreting black hole system, exhibits several observational features hinting at an intricate interplay between the accretion disk, its atmosphere known as the corona and the putative relativistic jet. It has been extensively studied using all available observational methods, including using the newly available technique of sensitive X-ray polarimetry. X-ray polarization characteristics are distinct for coronal and jet emissions. The low X-ray polarization measured below $\sim$100 keV is understood as arising from the corona. In contrast, the high polarization measurements reported above $\sim$400 keV required a separate jet-dominated spectral component, which spectroscopy does not demonstrate conclusively. Here we report precise polarization measurements in the 100-380 keV region made during three different sub-classes of spectral states of the source using the CZTI instrument onboard {\em AstroSat}. A high polarization (23$\pm$4 \%) is found mainly in the Intermediate Hard State of the source, and the energy-resolved measurements smoothly connect the coronal and the jet regimes. When high polarization is observed, the simultaneous spectral data hints at a separate power law component above 100 keV. We examine the possible sources of this energy-dependent high polarization in Cygnus X-1.

arXiv commentAccepted for publication in ApJ Letters (ApJL)

References in corpus (40)

• Broad-band gamma-ray and X-ray spectra of NGC 4151 and their implications for physical processes and geometry
• A universal radio/X-ray correlation in low/hard state black hole binaries
• The May 1989 outburst of the Soft X-ray Transient GS 2023+338 (V404 Cyg)
• A jet model for the broadband spectrum of XTE J1118+480: Synchrotron emission from radio to X-rays in the Low/Hard spectral state
• The evolution of the timing properties of the black-hole transient GX 339-4 during its 2002/2003 outburst
• The Two-Phase Pair Corona Model for Active Galactic Nuclei and X-ray Binaries: How to Obtain Exact Solutions
• A relativistic jet from Cygnus X-1 in the low/hard X-ray state
• Cygnus X-1 contains a 21-solar mass black hole -- implications for massive star winds
• Simultaneous X-ray and gamma-ray observations of Cyg X-1 in the hard state by Ginga and OSSE
• Polarized Gamma-ray Emission from the Galactic Black Hole Cygnus X-1
• The Soft Gamma-Ray Spectral Variability of Cygnus X-1
• Polarized x-rays constrain the disk-jet geometry in the black hole x-ray binary Cygnus X-1
• Probing the Inner Region of Cyg X-1 in the Low/Hard State through its X-ray Broad Band Spectrum
• Suzaku Results on Cygnus X-1 in the Low/Hard State
• Separation of two contributions to the high energy emission of Cygnus X-1: Polarization measurements with INTEGRAL SPI
• The synchrotron boiler and the spectral states of black hole binaries
• On the origin of spectral states in accreting black holes
• The broad-band spectrum of Cygnus X-1 measured by INTEGRAL
• A transient relativistic radio jet from Cygnus X-1
• RXTE Observation of Cygnus X-1 In Its High State
• Analysis of NuSTAR and Suzaku observations of Cyg X-1 in the hard state: evidence for a truncated disc geometry
• On the origin of the various types of radio emission in GRS 1915+105
• High-energy gamma-ray emission from Cyg X-1 measured by Fermi and its theoretical implications
• The MeV spectral tail in Cyg X-1 and optically-thin emission of jets
• Detection of gamma rays of likely jet origin in Cygnus X-1
• Jet contributions to the broad-band spectrum of Cyg X-1 in the hard state
• Prompt emission polarimetry of Gamma Ray Bursts with ASTROSAT CZT-Imager
• High-energy gamma-rays from Cyg X-1
• Accretion geometry of the black-hole binary Cygnus X-1 from X-ray polarimetry
• A multiwavelength study of Cygnus X-1: the first mid-infrared spectroscopic detection of compact jets
• The multi-wavelength polarization of Cygnus X-1
• A new lepto-hadronic model applied to the first simultaneous multiwavelength data set for Cygnus X--1
• Spectral differences between the radio-loud and radio-quiet low-hard states of GRS 1915+105: possible detection of synchrotron radiation in X-rays
• Hard X-ray polarization catalog for a 5-year sample of Gamma-Ray Bursts using AstroSat CZT-Imager
• Correlated radio--X-ray variability of Galactic Black Holes: A radio--X-ray flare in Cygnus X-1
• Spectral and Timing Studies of Cyg X-1 in the Low/Hard State with Suzaku
• PoGO+ polarimetric constraint on the synchrotron jet emission of Cygnus X-1
• Improved background model for the Large Area X-ray Proportional Counter (LAXPC) instrument on-board AstroSat
• Distinct accretion modes of Cygnus X-1 revealed from hard X-rays
• Extending the energy range of AstroSat-CZTI up to 380 keV with Compton Spectroscopy

Cited by in corpus (5)

• A hidden quasi-periodic oscillation in Cygnus X-1 revealed by NICER
• Astroparticles from X-ray Binary Coronae
• INTEGRAL/IBIS polarization detection in the hard and soft intermediate states of Swift J1727.8-1613
• A Hidden Pulse: Uncovering a New Timing Signal in Cygnus X-1 with AstroSat
• A kinetic model of jet-corona coupling in accreting black holes