A relativistic jetted outburst from a massive black hole fed by a tidally disrupted star

Abstract: While gas accretion onto some massive black holes (MBHs) at the centers of galaxies actively powers luminous emission, the vast majority of MBHs are considered dormant. Occasionally, a star passing too near a MBH is torn apart by gravitational forces, leading to a bright panchromatic tidal disruption flare (TDF). While the high-energy transient Swift J164449.3+573451 ("Sw 1644+57") initially displayed none of the theoretically anticipated (nor previously observed) TDF characteristics, we show that the observations (Levan et al. 2011) suggest a sudden accretion event onto a central MBH of mass ~10^6-10^7 solar masses. We find evidence for a mildly relativistic outflow, jet collimation, and a spectrum characterized by synchrotron and inverse Compton processes; this leads to a natural analogy of Sw 1644+57 with a smaller-scale blazar. The phenomenologically novel Sw 1644+57 thus connects the study of TDFs and active galaxies, opening a new vista on disk-jet interactions in BHs and magnetic field generation and transport in accretion systems.

• The paper reveals that the tidal disruption of a star triggers a relativistic jet in a massive black hole, as evidenced by Sw 1644+57's variable, high-energy emission.
• The paper employs combined observational data and theoretical modeling to link jet collimation with accretion near the Eddington limit.
• The paper suggests that future radio surveys targeting off-axis events could confirm tidal disruption occurrences and refine jet formation models.

Analysis of Relativistic Jetted Outbursts from Tidal Disruption Events in Massive Black Holes

This study presents an empirical and theoretical exploration of a relativistic jetted outburst originating from a massive black hole (MBH), triggered by the tidal disruption of a nearby star. The focal point of the investigation is the event designated Sw 1644+57, observed as an atypical high-energy transient, diverging from conventional characteristics associated with tidal disruption flares (TDFs).

Observational Basis

Sw 1644+57 was initially catalogued as a long-duration gamma-ray burst (GRB 110328A) but was later identified as divergent due to its extended and variable X-ray afterglow. The transient's positional overlap with the central region of its host galaxy intimates a connection to an accreting MBH. The investigators associate this event with a scenario similar to a blazar, noting the spectral properties characterized by synchrotron and inverse Compton processes.

Accretion Dynamics and Jet Formation

The paper posits that the observed phenomena arise from sudden accretion onto an MBH with a mass estimated between $10^6$ and $10^7$ solar masses. The evidence for a relativistic jet includes the high-energy spectrum and rapid luminosity variations, akin to blazars. The data indicate jet collimation and suggest that the MBH operates near the Eddington limit while exhibiting relativistically beamed emission.

Theoretical Context

The work extends the understanding of TDFs by considering them in the domain of active galactic processes typically reserved for AGNs and blazars. The jet launch mechanisms and relativistic flow dynamics underscore the intricate interaction between disrupted stellar material and the MBH. The upper constraints on the MBH mass align with dynamics that enable the star's tidal disruption beyond the event horizon.

Implications and Predictions

This research conveys implications for models of jet emission and disk-jet interaction in accretion systems. Sw 1644+57 provides a case for studying the in-situ generation of magnetic fields necessary for jet propulsion—fields stronger than those typically proposed in conventional stellar or AGN environments.

Practically, these results offer guidance for future surveys aimed at detecting similar jetted TDFs. The paper forecasts the occurrence of off-axis events detectable primarily in radio wavelengths, positing that such surveys could significantly ratify estimates of TDF occurrence rates. Moreover, the study implies that jetted TDFs could contribute marginally to the cosmic ray flux at ultra-high energies.

Future Directions

The observations provide a pivotal test case for theoretical models of TDFs connected with relativistic jets. Future research should aim to refine the understanding of magnetic field generation in these events and further establish the conditions under which MBHs transition from dormancy to activity. The potential for polarization studies and VLBI-based motion analysis presents avenues for deepening the understanding of such transient phenomena.

This paper bridges observational astrophysics and theoretical models, suggesting a significant role for these events in the broader context of cosmic structure and high-energy astrophysical processes. The coupling of empirical data with simulations provides a basis for enhanced comprehension of MBH dynamics and their cosmic manifestations.