Interaction of an outflow with surrounding gaseous clouds as the origin of the late-time radio flares in TDEs

Abstract

Close encounter between a star and a supermassive black hole (SMBH) results in the tidal disruption of the star, known as a tidal disruption event (TDE). Recently, a few TDEs, e.g., ASASSN-15oi and AT2018hyz, have shown late-time (hundreds of days after their UV/optical peaks) radio flares with radio luminosities of $10^{38\sim 39}$ erg/s. The super-Eddington fallback or accretion in a TDE may generate a mass outflow. Here we investigate a scenario that the late-time radio flares come from the interaction of the outflow with the circum-nuclear gaseous clouds, in addition to the slow-evolving emission component due to the outflow-diffuse medium interaction. We calculate the associated radio temporal and spectral signatures and find that they reproduce well the observations. The outflows have the inferred velocity of 0.2$c\sim 0.6$$c$, the total mass of $10^{-3}\sim 10^{-1}$ ${\mathrm{M}}_{\odot }$ and the ejection duration of a month to a year. The distances of the clouds to the SMBH are $0.1\sim 1$ pc. This scenario has advantages in explaining the long delay, sharpness of the rise and the multiplicity of the late radio flares. Future observations may build up a much larger sample of late-time radio flares and enable their use as a probe of the TDE physics and the host circumnuclear environment.

14 pages, 15 figures, accepted for publication in ApJ

References in corpus (22)

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• Delayed Radio Flares from a Tidal Disruption Event
• AT2019azh: an unusually long-lived, radio-bright thermal tidal disruption event
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• Generalized equipartition method from an arbitrary viewing angle
• Detectability of neutron star merger afterglows
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• Lightcurve Evolution of the nearest Tidal Disruption Event: A late-time, radio-only flare
• Could TDE outflows produce the PeV neutrino events?
• Radio emission of tidal disruption events from wind-cloud interaction
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• Years Delayed X-ray Afterglows of TDEs Originated from Wind-Torus Interactions
• Radiative hydrodynamical simulations of super-Eddington accretion flow in tidal disruption event: the accretion flow and wind
• Two-component off-axis jet model for radio flares of tidal disruption events
• Broad-line Region Clouds orbiting an AGN sample
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Cited by in corpus (4)

• Radio emission from tidal disruption events produced by the collision between super-Eddington outflows and the circumnuclear medium
• Infrared observations reveal the reprocessing envelope in the tidal disruption event AT 2019azh
• Numerical Studies on the Radio Afterglows in TDE: Forward Shock
• Radio and X-ray flux rebrightening six years after outburst in a partially-obscured extreme changing-look AGN