Non-thermal emission from stellar bow shocks

Abstract

Since the detection of non-thermal radio emission from the bow shock of the massive runaway star BD +43${}^{\circ }$3654 simple models have predicted high-energy emission, at X and gamma-rays, from these Galactic sources. Observational searches for this emission so far give no conclusive evidence but a few candidates at gamma rays. In this work we aim at developing a more sophisticated model for the non-thermal emission from massive runaway star bow shocks. The main goal is to establish whether these systems are efficient non-thermal emitters, even if they are not strong enough to be yet detected. For modeling the collision between the stellar wind and the interstellar medium we use 2D hydrodynamic simulations. We then adopt the flow profile of the wind and the ambient medium obtained with the simulation as the plasma state for solving the transport of energetic particles injected in the system, and the non-thermal emission they produce. For this purpose we solve a 3D (2 spatial + energy) advection-diffusion equation in the test-particle approximation. We find that a massive runaway star with a powerful wind converts 0.16-0.4% of the power injected in electrons into non-thermal emission, mostly produced by inverse Compton scattering of dust-emitted photons by relativistic electrons, and secondly by synchrotron radiation. This represents a fraction of $\sim$ $10^{-5}-10^{-4}$ of the wind kinetic power. Given the better sensibility of current instruments at radio wavelengths theses systems are more prone to be detected at radio through the synchrotron emission they produce rather than at gamma energies.

18 pages, 12 figures. Accepted for publication in ApJ

References in corpus (21)

• Infrared Emission from Interstellar Dust. IV. The Silicate-Graphite-PAH Model in the Post-Spitzer Era
• PLUTO: a Numerical Code for Computational Astrophysics
• The effect of photo-ionization on the cooling rates of enriched, astrophysical plasmas
• The empirical metallicity dependence of the mass-loss rate of O- and early B-type stars
• Computing the dust distribution in the bowshock of a fast moving, evolved star
• A comprehensive search for stellar bowshock nebulae in the Milky Way: a catalog of 709 mid-infrared selected candidates
• Models of the circumstellar medium of evolving, massive runaway stars moving through the Galactic plane
• E-BOSS: An Extensive stellar BOw Shock Survey. II. Catalogue second release
• Bow shock nebulae of hot massive stars in a magnetized medium
• On the observability of bow shocks of Galactic runaway OB stars
• Transport of magnetic turbulence in Supernova remnants
• Coupling hydrodynamics and radiation calculations for star-jet interactions in AGN
• X-ray Observations of Bow Shocks around Runaway O Stars. The case of $\zeta$ Oph and BD+43${}^{\circ }$3654
• Systematic search for high-energy gamma-ray emission from bow shocks of runaway stars
• On the Absence of Non-thermal X-ray emission around Runaway O stars
• X-ray study of bow shocks in runaway stars
• Systematic search for very-high-energy gamma-ray emission from bow shocks of runaway stars
• Runaway stars as cosmic ray injectors inside molecular clouds
• Possible Association of Two Stellar Bowshocks with Unidentified Fermi Sources
• High-energy radiation from collisions of high velocity clouds and the Galactic disk
• Modeling non-thermal emission from stellar bow shocks

Cited by in corpus (19)

• Probing Cosmic Ray Transport with Radio Synchrotron Harps in the Galactic Center
• MHD-shock structures of astrospheres: $\lambda$ Cephei-like astrospheres
• Wind nebulae and supernova remnants of very massive stars
• 3D MHD astrospheres: applications to IRC-10414 and Betelgeuse
• High-energy processes in starburst-driven winds
• PION: Simulating bow shocks and circumstellar nebulae
• MeerKAT discovery of radio emission from the Vela X-1 bow shock
• Skymaps of observables of three-dimensional MHD astrosphere models
• High-sensitivity radio study of the non-thermal stellar bow shock EB27
• Production of secondary particles in heavy nuclei interactions in supernova remnants
• And then they were two: detection of non-thermal radio emission from the bow shocks of two runaway stars
• Probing the non-thermal physics of stellar bow shocks using radio observations
• Searching for Faint X-ray Emission from Galactic Stellar Wind Bow Shocks
• Radio detections of IR-selected runaway stellar bow shocks
• Non-thermal emission in hyper-velocity and semi-relativistic stars
• Simulations of Magnetised Stellar-Wind Bubbles
• Cygnus survey with the Giant Metrewave Radio Telescope at 325 and 610 MHz: the catalog
• Adiabatic-radiative shock systems in YSO jets and novae outflows
• Radio polarization from runaway star bowshocks-I. The general case