Fig. 2: Optical spectrum of the host galaxy 2MASX J02301709+2836050 obtained with the NOT on day 132.
From: Monthly quasi-periodic eruptions from repeated stellar disruption by a massive black hole
Top, the black line shows the observed spectrum, while the orange line shows the fit to the stellar continuum provided by STARLIGHT. The vertical lines mark prominent emission and absorption features, which together allowed us to measure the redshift z = 0.03657 ± 0.00002 (1σ confidence). Bottom, the residuals between the observed data (stellar + nebular spectrum) and the fit (stellar continuum), which single out the nebular emission. The emission-line fluxes were measured from the residual spectrum and allowed us to place the galaxy on a BPT plot (Extended Data Fig. 3).
