Competitive X-ray and Optical Cooling in the Collisionless Shocks of WR 140

Abstract

WR 140 is a long-period, highly eccentric Wolf-Rayet star binary system with exceptionally well-determined orbital and stellar parameters. Bright, variable X-ray emission is generated in shocks produced by the collision of the winds of the WC7pd+O5.5fc component stars. We discuss the variations in the context of the colliding-wind model using broad-band spectrometry from the RXTE, SWIFT, and NICER observatories obtained over 20 years and nearly 1000 observations through 3 consecutive 7.94-year orbits including 3 periastron passages. The X-ray luminosity varies as expected with the inverse of the stellar separation over most of the orbit: departures near periastron are produced when cooling shifts to excess optical emission in CIII $\lambda 5696$ in particular. We use X-ray absorption to estimate mass-loss rates for both stars and to constrain the system morphology. The absorption maximum coincides closely with inferior conjunction of the WC star and provides evidence of the ion-reflection mechanism that underlies the formation of collisionless shocks governed by magnetic fields probably generated by the Weibel instability. Comparisons with K-band emission and HeI $\lambda$10830 absorption show that both are correlated after periastron with the asymmetric X-ray absorption. Dust appears within a few days of periastron suggesting formation within shocked gas near the stagnation point. X-ray flares seen in $\eta$ Carinae have not occurred in WR 140, suggesting the absence of large-scale wind inhomogeneities. Relatively constant soft emission revealed during the X-ray minimum is probably not from recombining plasma entrained in outflowing shocked gas.

arXiv comment52 pages, 17+1 figures, Accepted for publication in The Astrophysical Journal 23 August 2021

References in corpus (39)

• On the Absorption of X-rays in the Interstellar Medium
• Binary interaction dominates the evolution of massive stars
• Collisional Plasma Models with APEC/APED: Emission Line Diagnostics of Hydrogen-like and Helium-like Ions
• SB9: The Ninth Catalogue of Spectroscopic Binary Orbits
• Calibration of the Rossi X-ray Timing Explorer Proportional Counter Array
• The effect of massive binaries on stellar populations and supernova progenitors
• Stellar evolution with rotation X: Wolf-Rayet star populations at solar metallicity
• Progenitors of gravitational wave mergers: Binary evolution with the stellar grid-based code ComBinE
• The microphysics of collisionless shock waves
• The MiMeS survey of magnetism in massive stars: Magnetic analysis of the O-type stars
• Non-relativistic Collisionless Shocks in Unmagnetized Electron-Ion Plasmas
• High resolution radio observations of the colliding-wind binary WR140
• Radio, X-ray, and gamma-ray Emission Models of the Colliding Winds Binary WR 140
• Electron-Ion Temperature Equilibration in Collisionless Shocks: the Supernova Remnant-Solar Wind Connection
• 3D models of radiatively driven colliding winds in massive O+O star binaries - III. Thermal X-ray emission
• Constraining the Absolute Orientation of Eta Carinae's Binary Orbit: A 3-D Dynamical Model for the Broad [Fe III] Emission
• X-ray Spectral Variation of Eta Carinae through the 2003 X-ray Minimum
• Wind clumping and the wind-wind collision zone in the Wolf-Rayet binary gamma Velorum
• SNR 1E 0102.2-7219 as an X-ray Calibration Standard in the 0.5-1.0 keV Bandpass and Its Application to the CCD Instruments aboard Chandra, Suzaku, Swift and XMM-Newton
• Orbitally modulated dust formation by the WC7+O5 colliding-wind binary WR140
• A Clumping Independent Diagnostic of Stellar Mass-loss Rates: Rapid Clump Destruction in Adiabatic Colliding Winds
• First visual orbit for the prototypical colliding-wind binary WR 140
• He II $\lambda$4686 emission from the massive binary system in $\eta$ Car: constraints to the orbital elements and the nature of the periodic minima
• Advances in the RXTE Proportional Counter Array Calibration: Nearing the Statistical Limit
• Asymptotic Opening Angles for Colliding-Wind Bow Shocks: the Characteristic-Angle Approximation
• The orbit and stellar masses of the archetype colliding-wind binary WR 140
• The dominant X-ray wind in massive star binaries
• On the formation of CIII 4647-50-51 and CIII 5696 in O star atmospheres
• Colliding Stellar Winds Structure and X-ray Emission
• Understanding the X-ray Flaring from Eta Car
• Investigating the X-ray emission from the massive WR+O binary WR 22 using 3D hydrodynamical models
• V444 Cyg X-ray and polarimetric variability: Radiative and Coriolis forces shape the wind collision region
• The Dynamics of a High Mach Number Quasi-Perpendicular Shock: MMS Observations
• Suzaku monitoring of the Wolf-Rayet binary WR140 around periastron passage: An approach for quantifying the wind parameters
• Modelling the Central Constant Emission X-ray component of eta Carinae
• Colliding stellar wind modelling of the X-ray emission from WR 140
• Direct Evidence for Magnetic Reflection of Heavy Ions from High Mach Number Collisionless Shocks
• Conditions in the WR 140 wind-collision region revealed by the 1.083-micron He I line profile
• Separated Fringe Packet Observations with the CHARA Array III. The Very High Eccentricity Binary HR 7345

Cited by in corpus (8)

• Radiation-driven acceleration in the expanding WR140 dust shell
• From Dust to Nanodust: Resolving Circumstellar Dust from the Colliding-Wind Binary Wolf-Rayet (WR) 140
• The orbital kinematics of eta Carinae over three periastra with a possible detection of the elusive secondary's motion
• Exploring dust growth in the episodic WCd system WR140
• Inverse Compton cooling of thermal plasma in colliding-wind binaries
• X-ray plasma flow and turbulence in the colliding winds of WR140
• Revealing the accelerating wind in the inner region of the colliding-wind binary WR 112
• Particle Acceleration in Colliding Flows: Binary Star Winds and Other Double-Shock Structures