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Luis A. Manzaneda

Publications and source records attributed to Luis A. Manzaneda.

3 recordsLinked to original sources

Tidal disruption of stellar binaries as a pathway to exotic transients

Tidal disruption event (TDE) progenitors are commonly modelled as single stars on parabolic orbits around a supermassive black hole (SMBH), yet observations point to a richer diversity of dynamical pathways. We show that the tidal separation of stellar binaries by a $10^6\,M_\odot$ SMBH provides a natural mechanism for producing eccentric TDEs. Using restricted three-body dynamics and smoothed particle hydrodynamics (SPH) simulations, we model a binary composed of a solar-like star (SLS) and a white dwarf (WD) on a parabolic orbit. The binary orbital phase governs the outcome: one component is captured onto a tightly bound orbit while the other is ejected as a hypervelocity object, naturally producing TDEs with eccentricities $e \neq 1$. We classify the resulting events into Elliptical TDEs (eTDEs) and Hyperbolic TDEs (hTDEs), which occur with equal probability. For $\sim 88\%$ of binary orientations the disruption is clean, with no mass accreted by the WD. The remaining $\sim 12\%$ lies in two narrow windows of binary phase in which the WD captures material and becomes a WD with debris envelope (WDDE). About a third of that range, $\sim 4\%$ of all orientations, involves a direct WD--SLS collision near pericenter, giving fallback that peaks up to five times earlier and twenty times higher than in the single-star case; for the innermost $\sim 1.5\%$ the total WDDE mass exceeds $1.4\,M_\odot$, although the degenerate core itself does not, since the captured material forms a non-degenerate envelope. This suggests outcomes ranging from nova-like events to peculiar red giant-like objects. Depending on the binary phase, the mechanism may also produce repeating partial TDEs (rTDEs) and quasi-periodic eruptions (QPEs). Binary--SMBH encounters thus provide a robust channel for generating diverse TDEs with distinct observational signatures.

astro-ph.HE

A benchmark for binary star interaction with a supermassive black hole in general relativity

Most galaxies have supermassive black holes (SMBH) at their centres, surrounded by stars with binary systems also present in this environment. We use two schemes - post-Newtonian (PN) and a scalar perturbation to a background metric to numerically solve the three-body problem of a binary with a SMBH. We test three different PN formulations for the PN scheme: The Einstein-Infeld-Hoffman equation, pair-wise implementation of two-body PN-terms for three bodies and the Arnowitt-Deser-Misner Hamiltonian. We compare these approaches for one million solar mass and one billion solar mass black holes, and find a statistical match between the two approximations for stellar mass binary interacting with a million solar mass black hole. We also perform a statistical study for encounters with this black hole, and find that the higher order PN formulation matches with metric-with-perturbation scheme. However, we find a decrease in separation of the binary, and eccentricity variations between different schemes around the billion solar mass black hole. This behaviour is not present if binary has a large separation or is further away from the black hole due to decreased general-relativistic effects. We find that the pair-wise PN method results in a decrease in separation at pericentre in all test cases irrespective of the distance from the black hole or mass of the black hole, making this the least reliable method for solving this problem. Our work highlights the need for caution when interpreting the results in different formulations around SMBHs. This also shows that when understanding extreme mass ratio inspirals (EMRIs) using simulations, one should beware as the binary gets closer to the black hole.

astro-ph.IM

Relativistic tidal separation of binary stars by supermassive black holes

A binary stellar system that ventures too close to a supermassive black hole can become tidally separated. In this article, we investigate the role of relativistic effects in these encounters through 3-body simulations. We use the Hybrid Relativistic-Newtonian Approximation (HRNA), which combines the exact relativistic acceleration from a Schwarzschild black hole with a Newtonian description of the binary's self-gravity. This method is compared against Newtonian and Post-Newtonian (1PN) simulations. Our findings show good agreement between HRNA and 1PN results, both of which exhibit substantial differences from Newtonian simulations. This discrepancy is particularly pronounced in retrograde encounters, where relativistic simulations predict up to $30\%$ more separation events and an earlier onset of binary separation ($β=2$ compared to $2.5$ in Newtonian simulations, with $β$ the impact parameter). Additionally, the HRNA model predicts about 15$\%$ more potential extreme mass ratio inspirals and generate a higher number of hypervelocity star candidates, with velocities up to 2,000 km/s faster than those predicted from Newtonian simulations. Furthermore, compared to Newtonian cases, relativistic encounters are more likely to result in direct stellar collisions and binary mergers.

astro-ph.HE