Surroundings of the B2 star J183124.82−022008.4, showing the arc-shaped structure that points approximately to the direction of the central cluster. Figure 1 shows the position of this area with respect to the overall W40 region. J183124.82−022008.4 is the bright star near the apsis of the arc. The arc is likely a bowshock produced where the ram pressure of the wind of the star balances the ram pressure of the expanding shell. Blue and green correspond respectively to the Spitzer IRAC 3.6 μm and 4.5 μm bands and red corresponds to the MIPS 24 μm band.