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S 308 is an X-ray emitting bubble that surrounds the Wolf-Rayet star WR6. Thestructure shines in the optical as well and is thus known as the DolphinNebula. Due to its large angular extent, it has been covered at only 90% withpast XMM-Newton observations. Thanks to the unique dataset provided by theall-sky survey performed in X-rays by SRG/eROSITA, we can show for the firsttime the image of the bubble in its entire extent in this band, together withits spectral characterization. Moreover, we have tried to apply the sameprocedure for other wind-blown bubbles detected in the optical/IR and wesearched for X-ray extended emission around them. We first analyzed the diffuseemission of S308, providing a detailed spectral analysis. We then considered asample of 22 optical/IR selected wind-blown bubbles from a previous study basedon WISE data, providing an estimate of the X-ray flux for the first time. Weobtained the best fit for S308 with a two-temperature non-equilibrium plasmamodel (kT$_{1}=0.8_{-0.3}^{+0.8}$ keV and kT$_{2}=2_{-1}^{+3}$ keV) showingsuper-solar N abundance and low absorption. We did not detect any of the 22optical/IR emitting bubbles in X-rays, but using our best fit model, weestimated the 3$\sigma$ flux upper limits for each bubble. We demonstrate thenew possibility offered by SRG/eROSITA to study known wind-blown bubbles andlook for other ones. A two-temperature plasma description seems to fit the dataquite well for S308. Since all of the 22 bubbles studied still remainundetected by SRG/eROSITA, it is very likely that absorption effects andspatial compactness are responsible for the challenges standing in the way ofdetecting these bubbles in soft X-rays.

S 308 and other X-ray emitting bubbles around Wolf-Rayet stars