Title: Retrieving the true mass of gravitational-wave sources

　　Speaker: Xian Chen (Peking University)

　　Time：3pm, October 26 (Thursday)

　　Location:Lecture Hall, 3rd floor

　　Abstract:Retrieving the mass of a gravitational-wave (GW) source is a difficult problem because it is degenerate with redshift. In astronomy three types of redshift exist, namely cosmological, Doppler, and gravitational redshift, but the latter two are often neglected in the analysis of GW data. We study the effects of Doppler and gravitational redshifts on GWs, motivated by recent proposals that the binary black hole mergers detected by the Laser Interferometer GW Observatory (LIGO) could have happened in the vicinity of supermassive black holes. We find that they together can contribute an effective redshift as large as 1.9 <(1 + z)<3.4. Our results imply that black holes of 10 solar massescould masquerade as much bigger ones. Distinguishing them requires simultaneous observation of GWs in both (10 ? 102) Hertz and milli-Hertz bands.