Detecting Gravitational Scattering of Interstellar Objects Using Pulsar Timing

TL;DR

This paper explores how pulsar timing can detect gravitational scattering events caused by interstellar objects, potentially revealing asteroid-mass dark matter and acting as false positives in gravitational wave searches.

Contribution

It characterizes the timing signals from gravitational scattering events and assesses the detection prospects with current pulsar timing precision.

Findings

Detection of objects as small as 10^{-10} solar masses is possible.

Timing signals resemble glitches or gravitational wave bursts with memory.

Gravitational scattering signals can constrain dark matter models and mimic gravitational wave signals.

Abstract

Gravitational scattering events, in which the path of an interstellar object is deflected by a pulsar or the solar system, give rise to reflex motion which can potentially be detected using pulsar timing. We determine the form of the timing signal expected from a gravitational scattering event, which is ramp-like and resembles the signal produced by a glitch or a gravitational wave burst with memory (BWM), and investigate the prospects for detecting such a signal using a pulsar timing array. The level of timing precision currently achieved for some millisecond pulsars makes it possible to detect objects as small as $10^{-10}$ solar masses, less than the mass of the dwarf planet Ceres, at impact parameters as large as 1 AU. The signals produced by gravitational scattering could provide independent constraints on models of dark matter involving asteroid-mass objects or subhalos, and should be considered as potential false positives in searches for BWMs.