Searching for Faint X-Ray Emission from Galactic Stellar Wind Bow Shocks

Abstract

Abstract We present a stacking analysis of 2.61 Ms of archival Chandra observations of stellar wind bow shocks. We place an upper limit on the X-ray luminosity of infrared-detected bow shocks of <2 × 1029 erg s−1, a more stringent constraint than has been found in previous archival studies and dedicated observing campaigns of nearby bow shocks. We compare the X-ray luminosities and L X/L bol ratios of bow shock driving stars to those of other OB stars within the Chandra field of view. Driving stars are, on average, of later spectral type than the field-of-view OB stars, and we do not observe any unambiguously high L X/L bol ratios indicative of magnetic stars in our sample. We additionally assess the feasibility of detecting X-rays from stellar wind bow shocks with the proposed Lynx X-ray Observatory. If the X-ray flux originating from the bow shocks is just below our Chandra detection limit, the nearest bow shock in our sample (at ∼0.4 kpc with an absorbing column of ∼1021 cm−2) should be observable with Lynx in exposure times on the order of ∼100 ks.