Tidal disruption of a low-mass star in an active galactic nucleus as the origin of the PS16dtm outburst

Résumé fourni par la source

Context. The event PS16dtm, which occurred in the centre of the narrow-line Seyfert 1 (NLS1) galaxy SDSS J015804.75−005221.8(z = 0.080440), is one of the few candidates for a tidal disruption event in an already-accreting active galactic nucleus.Aims. We wish to shed light on the character of the tidal disruption event in this source since it exhibits unusual peculiarities, such asthe double-peak optical/UV light curve and a low blackbody temperature with a lack of X-ray emission.Methods. We performed a spectral analysis of the source before and during the event. We modelled the time evolution of the luminosityprofile using a numerical code that describes the viscous evolution of the flow.Results. Based on the combined spectral and timing studies, we interpret the event as the disruption of a ∼0.3 M main-sequencestar or as the gradual partial disruption of a low-mass giant star. The star is likely on a circular orbit, embedded in the accretion disc.We discuss that the evolution of the star rather suggests that the orbit is counter-rotating. We observe the system at a sufficientlylarge viewing angle that the actual disruption process is not directly observed. The disrupted star and inner disc are shielded from theobserver by a gaseous envelope. Further observations of the system as it returns to the previous NLS1 state, particularly in the X-rayband, are needed to confirm the proposed scenario and to place constraints on the return to a regular NLS1 state. The enclosed data are the luminosity time profile and the subsequent models used for the data fitting. The Table gives the parameters of ech fit.

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