English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Models for tidal disruption events (TDEs) in which a supermassive black holedisrupts a star commonly assume that the highly eccentric streams of boundstellar debris promptly form a circular accretion disk at the pericenter scale.However, recent numerical simulations (Shiokawa et al., 2015) demonstrated thatdissipation via hydrodynamical shocks is insufficient to circularize debris,and the flow retains its initial semi-major axis scale throughout the first ~10orbits of the event. The bolometric peak luminosity of most TDE candidates, afew x 10^{44} erg/s, implies that we observe only ~1% of the energy expectedfrom radiatively efficient accretion. Motivated by these results, (Piran etal., 2015) suggested that the observed optical TDE emission is powered byshocks at the apocenter between freshly infalling material and earlier arrivingmatter. This model explains the small radiated energy, the low temperature, andthe large radius implied by the observations as well as the t^{-5/3} lightcurve. However the question of the system's low {bolometric} efficiency remainsunanswered. We suggest that the high orbital energy and low angular momentum ofthe flow make it possible for magnetic stresses to reduce the matter's alreadysmall angular momentum to the point at which it can fall ballistically into theSMBH before circularization. As a result, the efficiency is only ~1--10% of astandard accretion disk's efficiency. Thus, the intrinsically high eccentricityof the tidal debris naturally explains why most TDE candidates are fainter thanexpected.

Elliptical accretion and inefficient highly eccentric accretion and the low luminosity of stellar tidal disruption events