Abstract
Context. Asteroids orbiting into the highly magnetized and highly relativistic wind of a pulsar offer a favorable configuration for repeating fast radio bursts (FRB). The body in direct contact with the wind develops a trail formed of a stationary Alfvén wave, called an Alfvén wing. When an element of wind crosses the Alfvén wing, it sees a rotation of the ambient magnetic field that can cause radio-wave instabilities. In the observer’s reference frame, the waves are collimated in a very narrow range of directions, and they have an extremely high intensity. A previous work, published in 2014, showed that planets orbiting a pulsar can cause FRBs when they pass in our line of sight. We predicted periodic FRBs. Since then, random FRB repeaters have been discovered. Aims. We present an upgrade of this theory with which repeaters can be explained by the interaction of smaller bodies with a pulsar wind. Methods. Considering the properties of relativistic Alfvén wings attached to a body in the pulsar wind, and taking thermal consideration into account, we conducted a parametric study. Results. We find that FRBs, including the Lorimer burst (30 Jy), can be explained by small-size pulsar companions (1 to 10 km) between 0.03 and 1 AU from a highly magnetized millisecond pulsar. Some parameter sets are also compatible with a magnetar. Our model is compatible with the high rotation measure of FRB 121102. The bunched timing of the FRBs is the consequence of a moderate wind turbulence. An asteroid belt composed of fewer than 200 bodies would suffice for the FRB occurrence rate measured with FRB 121102. Conclusions. After this upgrade, this model is compatible with the properties discovered since its first publication in 2014, when repeating FRBs were still unknown. It is based on standard physics and on common astrophysical objects that can be found in any type of galaxy. It requires 1010 times less power than (common) isotropic-emission FRB models.
Highlights
Mottez & Zarka (2014, hereafter MZ14) proposed a model of fast radio bursts (FRB) that involves common celestial bodies, neutron stars (NS), and planets orbiting them, well-proven laws of physics, and a moderate energy demand that allows for a narrowly beamed continuous radio-emission from the source that sporadically illuminates the observer
MZ14 is based on the relativistic Alfvén wings theory of Mottez & Heyvaerts (2011), and the authors concluded that planetary companions of standard or millisecond pulsars could be the source of FRBs
Source ET is the blackbody radiation of the neutron star, EP is associated with inductive absorption of the Poynting flux, ENT is caused by the pulsar nonthermal photons, EW is associated with the impact of wind particles, and EJ is caused by the circulation of the Alfvén wing current IA into the companion
Summary
Mottez & Zarka (2014, hereafter MZ14) proposed a model of FRBs that involves common celestial bodies, neutron stars (NS), and planets orbiting them, well-proven laws of physics (electromagnetism), and a moderate energy demand that allows for a narrowly beamed continuous radio-emission from the source that sporadically illuminates the observer. When these ingredients are put together, the model is compatible with the localization of FRB sources at cosmological distances (Chatterjee et al 2017), it can explain the millisecond burst duration, the flux densities above 1 Jy, and the range of observed frequencies. We present a short discussion and the number of asteroids required to explain the observed burst rates
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