X-ray study of bow shocks in runaway stars

Abstract

Massive runaway stars produce bow shocks through the interaction of their winds with the interstellar medium, with the prospect for particle acceleration by the shocks. These objects are consequently candidates for non-thermal emission. Our aim is to investigate the X-ray emission from these sources. We observed with XMM-Newton a sample of 5 bow shock runaways, which constitutes a significant improvement of the sample of bow shock runaways studied in X-rays so far. A careful analysis of the data did not reveal any X-ray emission related to the bow shocks. However, X-ray emission from the stars is detected, in agreement with the expected thermal emission from stellar winds. On the basis of background measurements we derive conservative upper limits between 0.3 and 10 keV on the bow shocks emission. Using a simple radiation model, these limits together with radio upper limits allow us to constrain some of the main physical quantities involved in the non-thermal emission processes, such as the magnetic field strength and the amount of incident infrared photons. The reasons likely responsible for the non-detection of non-thermal radiation are discussed. Finally, using energy budget arguments, we investigate the detectability of inverse Compton X-rays in a more extended sample of catalogued runaway star bow shocks. From our analysis we conclude that a clear identification of non-thermal X-rays from massive runaway bow shocks requires one order of magnitude (or higher) sensitivity improvement with respect to present observatories.

15 pages, 6 figures and 9 tables, accepted for publication in MNRAS

References in corpus (5)

• Mass loss from hot massive stars
• Radio, X-ray, and gamma-ray Emission Models of the Colliding Winds Binary WR 140
• Non-thermal emission processes in massive binaries
• E-BOSS: An Extensive stellar BOw Shock Survey. II. Catalogue second release
• Systematic search for high-energy gamma-ray emission from bow shocks of runaway stars

Cited by in corpus (9)

• 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
• MeerKAT discovery of radio emission from the Vela X-1 bow shock
• High-sensitivity radio study of the non-thermal stellar bow shock EB27
• Mixing of materials in magnetised core-collapse supernova remnants
• Searching for Faint X-ray Emission from Galactic Stellar Wind Bow Shocks
• Radio detections of IR-selected runaway stellar bow shocks
• Radio polarization from runaway star bowshocks-I. The general case