tokens: of any other considerations. The best-fitting central masses associated with smaller spins were systematically lower, but always with M > 9 × 10 8 M ⊙ . In general, smaller black hole spins produced poorer fits to the observed light curves. A Schwarzschild black hole (best-fitting mass M = 9 × 10 8 M ⊙ ) produced the worst fit,, and would require a 28.3 M ⊙ solar-type star for disruption (fig. 2, Kesden 2012 ). This makes a low spin value very unlikely. For larger spins, the quality of fit is similar to the near-maximal a / r g = 0.99 case. When a / r g = 0.9, the best-fitting light curve has , with a very similar best-fitting black hole mass M = 1.35 × 10 9 M ⊙ . However, even this slight reduction from maximal spin now requires an 8.3 M ⊙ star for a disruption, compared to M ⋆ = 2.6 M ⊙ for a / r g = 0.99. From the light curves alone, we cannot rule out the possibility of an extremely massive star being disrupted by a more moderately rotating black hole. The strong dependence of TDE rate on stellar mass ( as noted above) clearly favours a near-maximal spin. The light curves of Section 3 were produced assuming a face-on inclination. The best-fitting parameters are, in fact, only weakly sensitive to the disc–observer inclination, with only minor changes to the fitted parameters for θ 20 o . For higher inclination angles, larger black hole masses were required. Taking the uppermost black hole mass allowed from the galactic bulge range as a hard upper limit, we may constrain the inclination to θ 60 o . Given that a relatively massive (∼2 M ⊙ ) star has been disrupted, it is somewhat surprising that the disc component of the evolving light curves is powered by only a relatively small accreted mass M acc ≃ 0.07 M ⊙ . It is important to note that this accreted mass value does not include the matter required to power the (extremely bright) early-time emission (observed in all bands), or the late-time UV emission. Rather, the disc mass represents only a lower bound on the debris mass. Given the likely highly relativistic orbit of the disrupted star, it may well be that a significant portion of the stellar mass was directly accreted in the earliest stages. It has also been argued (Guillochon Ramirez Ruiz 2015 ) that relativistic orbital precession of the tidal disruption streams (induced by a large black hole spin) can lead to inefficient disc formation. 3.2 Radio and X-ray observations No radio emission has been detected from ASASSN-15lh, with upper limits of order ν L ν ≲ 10 38 erg s −1 ( L16 ; Kool et al. 2015 ). Given the likely near-maximal spin of its central black hole, it is perhaps surprising that a jet is not observed. [The observed radio emission is at least two to three orders of magnitude lower than the bright, jetted TDE Swift J1644+57 (Levan et al. 2011 ).] Moreover, unlike other jetted TDEs, ASASSN-15lh is X-ray dim. Initially undetected at X-ray energies ( L16 ), X-ray emission has been more recently detected by Margutti et
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