Long Period Transients (LPTs): a comprehensive review

TL;DR

Long Period Transients are a newly identified class of periodic radio sources with diverse potential origins, characterized by bright, polarized bursts lasting seconds to minutes, with ongoing debates about their exact physical nature.

Contribution

This review synthesizes current observations and interpretations of Long Period Transients, highlighting the challenges in understanding their physical origins and proposing directions for future research.

Findings

About 12 LPT sources identified with diverse characteristics.

Proposed models include binary systems, magnetars, and white dwarfs.

Current explanations cannot fully account for observed properties.

Abstract

Long Period Transients (LPTs) are a recently identified class of sources characterized by periodic radio bursts lasting seconds to minutes, with flux densities that might reach several tens of Jy. These radio bursts repeat with periodicity from minutes to hours, and they exhibit strong polarization and transient activity periods. To date, about 12 such sources have been identified, which might encompass the same or different physical scenarios. Proposed explanations include binary systems with a white dwarf and a low-mass star companion, slow-spinning magnetars, highly magnetized isolated white dwarfs, and other exotic objects. In a few cases the optical counterpart indeed points toward a white dwarf with a low-mass companion, while in other cases, transient X-ray emission was detected, very common in magnetars. However, despite being able to reproduce partially some of the characteristics of LPTs, all the proposed scenarios find difficulty in explaining the exact physical origin of their bright, highly polarized and periodic radio emission. We review here the state-of-the-art in the observations and interpretation of this puzzling class of radio transients.