Red giant - jet collisions in galactic nuclei I: 3D hydrodynamical model of a few stellar orbits

Abstract

Several models have been proposed to explain missing red giants (RGs) near the Galactic centre. Recently, a scenario has been suggested that predicts, among other processes, a long-term ablation of the surface layers of RGs during their repetitive passages through the Galactic jet (Zajaček et al., 2020). In this study, we perform detailed three-dimensional numerical modelling of this phenomenon. We calculate the ablation rate of the surface layers of a RG orbiting the supermassive black hole (SMBH) as it passes through the nuclear jet. In particular, we model the jet-star interaction for approximately 10 passages for the closer orbital distance of $10^{-3}\text{pc}$ and 2 passages for $10^{-2}\text{pc}$. We find that the mass loss due to ablation by the jet behaves with time as $\Delta M_{\star }\propto \sqrt{t}$ and the total ablated mass during a single active galactic nucleus (AGN) phase ($10^5$ years) is $\sim 10^{-4}{M}_{\odot }$. We arrive at similar rates of the stellar ablation for the relatively smaller jet luminosity $10^{42}\text{erg}{\text{s}}^{-1}$ as in the previous analytical calculations. For larger jet luminosities of $10^{44}$ and $10^{48}\text{erg}{\text{s}}^{-1}$, the ablation rates inferred from $\sim 10$ interactions as well as extrapolated power-law fits are significantly lower than analytical values. Overall, the mass ablation rate per interaction and the extrapolated cumulative mass loss during the jet activity are comparable to the stellar-wind mass loss. For the smallest orbital distance of $10^{-3}\text{pc}$, we also track the thermal behaviour of the stellar surface layer, whose temperature appears to grow rapidly during the first 10 passages from $\sim 3600\mathrm{K}$ (spectral type M) to $\sim 8500\mathrm{K}$ (spectral type A). RG-jet interactions can thus lead to observable changes in the nuclear stellar population during the jet existence.

22 pages, 23 figures, 2 tables; accepted by the MNRAS Main journal

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Cited by in corpus (2)

• On the Missing Red Giants near the Galactic Center
• Evolution of Quasi-Periodic Eruptions in the post-TDE Accretion Disk Perturbed by an Orbiting Star