Collisions of red giants in galactic nuclei
[EN] In stellar-dense environments, stars can collide with each other. For collisions close to a supermassive black hole (SMBH), the collisional kinetic energy can be so large that the colliding stars can be destroyed, potentially releasing an amount of energy comparable to that of a supernova. Thes...
| Authors: | , , , |
|---|---|
| Format: | article |
| Publication Date: | 2024 |
| Country: | España |
| Institution: | Universitat Politècnica de València (UPV) |
| Repository: | RiuNet. Repositorio Institucional de la Universitat Politécnica de Valéncia |
| Language: | English |
| OAI Identifier: | oai:riunet.upv.es:10251/229457 |
| Online Access: | https://riunet.upv.es/handle/10251/229457 |
| Access Level: | Open access |
| Keyword: | Hydrodynamics Stars: kinematics and dynamics Galaxy: nucleus Quasars: supermassive black holes Transients |
| Summary: | [EN] In stellar-dense environments, stars can collide with each other. For collisions close to a supermassive black hole (SMBH), the collisional kinetic energy can be so large that the colliding stars can be destroyed, potentially releasing an amount of energy comparable to that of a supernova. These black hole-driven disruptive collisions have been examined mostly analytically, with the non-linear hydrodynamical effects being left largely unstudied. Using the moving-mesh hydrodynamics code arepo, we investigate high-velocity (>103 km s-1) collisions between 1 M circle dot giants with varying radii, impact parameters, and initial approaching velocities, and estimate their observables. Very strong shocks across the collision surface efficiently convert >= 10 per cent of the initial kinetic energy into radiation energy. The outcome is a gas cloud expanding supersonically, homologously, and quasi-spherically, generating a flare with a peak luminosity similar or equal to 10(41)-10(44) erg s(-1) in the extreme ultraviolet band (similar or equal to 10 eV). The luminosity decreases approximately following a power law of t-0.7 initially, then t(-0.4) after t similar or equal to 10 d at which point it would be bright in the optical band (less than or similar to 1eV). Subsequent, and possibly even brighter, emission would be generated due to the accretion of the gas cloud on to the nearby SMBH, possibly lasting up to multiyear time-scales. This inevitable BH-collision product interaction can contribute to the growth of BHs at all mass scales, in particular, seed BHs at high redshifts. Furthermore, the proximity of the events to the central BH makes them a potential tool for probing the existence of dormant BHs, even very massive ones which cannot be probed by tidal disruption events. |
|---|