NASA's Chandra observes spider pulsars preying on stellar companions

Using NASA's Chandra X-ray Observatory, astronomers have made an X-ray study of spider pulsars, a group of dead stars that destroy companion stars within their reach. The data collected from the globular cluster Omega Centauri is helping researchers understand the process by which these dead stars hunt their stellar counterparts.

Spider pulsars are a type of millisecond pulsars that emit winds of energetic particles which methodically strip away the outer layers of the companion stars.

Recently, the Parkes and MeerKAT radio telescopes discovered 18 millisecond pulsars in Omega Centauri, about 17,700 light-years away from Earth. Following this discovery, Astronomers from the University of Alberta in Canada analysed the Chandra data to determine whether any of these pulsars emit X-rays. They found 11 millisecond pulsars emitting X-rays, five of which were concentrated near the center of Omega Centauri. The researchers then combined the data of Omega Centauri with Chandra observations of 26 spider pulsars in 12 other globular clusters.

Spider pulsars are classified into two categories, based on the size of the star they destroy. The Redback spider pulsars are damaging companion stars weighing between a tenth and a half the mass of the Sun and the black widow spider pulsars are damaging companion stars with less than 5 percent of the Sun's mass.

The researchers found that the redbacks are brighter in X-rays compared to the black widows, confirming previous work. The team is the first to show a link between X-ray brightness and the mass of the spiders' companions, with pulsars that produce more X-rays being paired with more massive companions, providing clear evidence that the companion's mass affects the amount of X-rays the pulsar receives.

Spider pulsars are usually located very close to their companion stars, at a distance of only one to 14 times that between the Earth and the Moon. This proximity causes energetic particles from pulsars to damage their companion stars.

A group of dead stars known as "spider pulsars" are obliterating nearby companion stars within their reach in Omega Centauri. Data from NASA's Chandra X-ray Observatory is helping scientists understand how these pulsars prey on their stellar companions: https://t.co/NtQLTdENgI pic.twitter.com/lW14AWGcps

— Chandra Observatory (@chandraxray) November 30, 2023