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At 66 Mpc, AT2019qiz is the closest optical tidal disruption event (TDE) todate, with a luminosity intermediate between the bulk of the population andiPTF16fnl. Its proximity allowed a very early detection and triggering ofmultiwavelength and spectroscopic follow-up well before maximum light. Thevelocity dispersion of the host galaxy and fits to the TDE light curve indicatea black hole mass $\approx 10^6$ M$_\odot$, disrupting a star of $\approx 1$M$_\odot$. Comprehensive UV, optical and X-ray data shows that the earlyoptical emission is dominated by an outflow, with a luminosity evolution $L\propto t^2$, consistent with a photosphere expanding at constant velocity($\gtrsim 2000$ km s$^{-1}$), and a line-forming region producing initiallyblueshifted H and He II profiles with $v=3000-10000$ km s$^{-1}$. The fastestoptical ejecta approach the velocity inferred from radio detections (modelledin a forthcoming companion paper from K.~D.~Alexander et al.), thus the sameoutflow may be responsible for both the fast optical rise and the radioemission -- the first time this connection has been observed in a TDE. Thelight curve rise begins $29 \pm 2$ days before maximum light, peaking when thephotosphere reaches the radius where optical photons can escape. Thephotosphere then undergoes a sudden transition, first cooling at constantradius then contracting at constant temperature. At the same time, theblueshifts disappear from the spectrum and Bowen fluorescence lines (N III)become prominent, implying a source of far-UV photons, while the X-ray lightcurve peaks at $\approx 10^{41}$ erg s$^{-1}$. Assuming that these X-rays arefrom prompt accretion, the size and mass of the outflow are consistent with thereprocessing layer needed to explain the large optical to X-ray ratio in thisand other optical TDEs, possibly favouring accretion-powered overcollision-powered outflow models.

An outflow powers the optical rise of the nearby, fast-evolving tidal disruption event AT2019qiz