Prospects of eLISA for Detecting Galactic Binary Black Holes Similar to GW150914

We discuss the prospects of eLISA for detecting gravitational waves (GWs) from Galactic binary black holes (BBHs) similar to GW150914. For a comoving merger rate that is consistent with current observation, eLISA is likely to identify at least one BBH with a sufficient signal-to-noise ratio. In addition, eLISA has a potential to measure the eccentricity of the BBH as small as $e\sim 0.02$,correspondingtotheresidualvalue$e\sim 10^{-6}$ at 10Hz. Therefore, eLISA could provide us with a crucial information to understand the formation processes of relatively massive BBHs like GW150914. We also derive a simple scaling relation for the expected number of detectable Galactic BBHs.