A detailed spectroscopic study of tidal disruption events

Spectroscopically, tidal disruption events (TDEs) are characterized by broad (∼10 4 km s −1 ) emission lines and show a large diversity as well different line profiles. After carefully consistently performing series of data reduction tasks including host galaxy light subtraction, we present here the first detailed, spectroscopic population study 16 optical UV TDEs. We number prominent among TDEs Hydrogen, Helium, Bowen quantify their evolution with time in terms luminosities, velocity widths, offsets. report lag between peaks curves peak luminosity H α spanning ∼7 45 days. If interpreted echoes, these lags correspond to distances ∼2 − 12 × 10 cm, which one two orders magnitudes larger than estimated blackbody radii ( R BB same discuss possible origin this surprisingly discrepancy. also for He I 5876 Å line, smaller ones similar or N III that have lower widths compared rest our sample find strong X-ray ratio might imply weakening widths. Furthermore, luminosities ratios respect temperatures T ). linear relationship L ∝ potentially an inverse power-law relation −β ), leading weaker ≥ 25 000 K. The II /He becomes at temperatures, possibly pointing ionization effect. /H photospheric radius recedes, implying stratified photosphere where Helium lies deeper Hydrogen. suggest features seen along properties can be attributed viewing angle effects.