Pulsars are neutron stars rotating rapidly, emitting electromagnetic radiation in various wavelengths, including radio waves, optical, X-ray, and gamma-ray. In some middle aged pulsars, regions of extended gamma-ray emission in tera electron volt (TeV) energies are documented in recent days. These regions, referred to as TeV halos, were found to be significantly larger than their corresponding pulsar’s wind nebulae. Despite being increasingly documented, the question prevailed if TeV halos are common or rare phenomenon. In a recent study by a large group of researchers from USA and Mexico, suggest that TeV halos are universal features of middle-aged pulsars.
About the study
According to the study, TeV halos are universal features of middle-aged pulsars and could thus be used to identify pulsars that cannot be detected using instruments designed to pick up radio waves or lower-energy gamma rays.
In this study researchers analysed a sky map containing high-energy gamma-ray observations collected over a period of 2,300 days at the HAWC observatory. The HAWC observatory, situated on the slopes of the Sierra Negra volcano in Mexico, specializes in the detection of secondary particles that are produced when high-energy gamma rays originating from space reach Earth’s atmosphere.
The team identified TeV halos around the middle-aged pulsars that were in HAWC’s field of view. Then they used their likelihood profiles to determine how the data indicates the presence of extended gamma-ray emission. Stacking these profiles, they assessed a collective signal that could indicate the widespread presence of TeV halos.
Future implications
The discovery of TeV halos to be a universal phenomenon implies that they could be used to detect the rather undetectable pulsars.
Sara Coutiño De León, co-author of the paper, said to Phys.org, «This suggests that we may need to revisit and revise current models of how high-energy particles travel through the Milky Way. We now plan to conduct detailed studies of individual TeV halos. By doing this, we aim to better understand how particles propagate in and around these sources.»
