Investigation of the asteroid–neutron star collision model for the repeating fast radio bursts

Abstract

The origin of fast radio bursts (FRBs) is still a mystery. One model proposed to interpret the only known repeating object, FRB 121102, is that the radio emission is generated from asteroids colliding with a highly magnetized neutron star (NS). With N -body simulations, we model a debris disc around a central star with an eccentric orbit intruding NS. As the NS approaches the first periastron passage, most of the comets are scattered away rather than being accreted by the NS. To match the observed FRB rate, the debris belt would have to be at least three orders of magnitude more dense than the Kuiper belt. We also consider the rate of collisions on to the central object but find that the density of the debris belt must be at least four orders of magnitude more dense than the Kuiper belt. These discrepancies in the density arise even if (1) one introduces a Kuiper-belt like comet belt rather than an asteroid belt and assume that comet impacts can also make FRBs; (2) the NS moves ∼ 2 orders of magnitude slower than their normal proper-motion velocity due to supernova kicks; and (3) the NS orbit is coplanar to the debris belt, which provides the highest rate of collisions.

Periodic activity from fast radio burst FRB180916 explained in the frame of the orbiting asteroid model

“…Levison et al 1997) we note that the orbit of Jupiter is only ∼ 20 times wider than the orbit assumed here and therefore the (angular) density of asteroids does not need to be larger if the swarms span a similar angular size. This contrasts with the simulations carried out by Smallwood et al (2019) in the context of the colliding asteroid model (Dai et al 2016), which showed that an asteroid belt with a density several orders of magnitude larger than that of the solar system's main belt or Kuiper's belt was necessary for that model.…”

“…In the orbiting asteroid model, the periodicity of activity windows is due to the specific orbital dynamics of the system. This is also the case for a number of other models: Decoene et al (2020) which is also based on the Alfvén wing mechanism, Smallwood et al (2019); Dai & Zhong (2020) for colliding asteroids, Gu et al (2020) for accreted white-dwarf companions, and Lyutikov et al (2020) for either magnetospheric or wind magnetar models. In magnetospheric magnetar models, it has also been proposed that free precession of the neutron star (Zanazzi & Lai 2020;Levin et al 2020), or ultra-long period magnetars (Beniamini et al 2020) might be the cause.…”

“…Another category of models resorts to the release of gravitational and kinetic energy of asteroids colliding with a neutron star (e.g. Dai et al 2016;Bagchi 2017;Smallwood et al 2019;Dai & Zhong 2020;Dai 2020) or, alternatively, of matter accreted from a white-dwarf companion (Gu et al 2016(Gu et al , 2020 which again largely, if briefly, overpowers the spin-down of the neutron star. In the orbiting asteroid model, the periodicity of activity windows is due to the specific orbital dynamics of the system.…”

Fast radio burst repeaters produced via Kozai-Lidov feeding of neutron stars in binary systems

“…Fast radio bursts can be produced if asteroids pass close to the Roche limit of a compact object with an electromagnetic wind (Mottez & Zarka 2014;, or if they undergo collisions with this object (Dai 2016;Smallwood et al 2019). The infall of asteroids from standard belts onto the central compact object can be triggered by Kozai-Lidov oscillations, in the presence of an outer black hole.…”

“…In particular, via the Alfvén wing emission mechanism presented in Mottez & Zarka (2014), this emission could be the source of FRBs. Other authors have proposed that FRBs result from the impact of asteroids and comets on central compact objects (Geng & Huang 2015;Dai 2016;Smallwood et al 2019). Interestingly, the above models could naturally lead to repeating signals, as long as small bodies, such as asteroids, pass by the star at a rate corresponding to the observations.…”