Tracking the path of a runaway star can shed light on the supermassive black hole at the center of the Milky Way or activity within a stellar cluster. Researchers tracking the runaway binary star system LP400-22 were hoping to learn more about the galactic center’s black hole and discovered some unusual features of the only known runaway white dwarf pair.
Researchers from the Harvard-Smithsonian Center for Astrophysics, CfA, tracked LP400-22 using spectroscopy, astrometry, radio, and X-ray data. The study was published in the Monthly Notices of the Royal Astronomical Society.
Stars traveling at a higher speed, or velocity, than their surrounding environment are classified as runaway stars. Hypervelocity stars are traveling much faster than runaway stars and researchers from CfA previously discovered such a star, traveling at speeds over three million kilometers per hour, close to two million miles per hour. That star was once part of a binary star system but the second star was devoured by the supermassive black hole at the center of the Milky Way. The star was ejected from the around the black hole approximately 80 million years ago.
With LP400-22 being the only known runaway pair of white dwarf stars, the researchers wanted to learn more about the star system, its origin and what mechanism was responsible for its increased velocity. According to the researchers, there are two mechanisms associated with runaway star: within a binary star system one star going supernova thus freeing the second star or getting ejected from a dense stellar cluster.
Over the course of five years, researchers observed LP400-22, approximately 1,400 light-years from Earth, and discovered that it did not originate black hole at the galactic center. The researchers believe the runaway binary stars were originally from a dense stellar cluster and have traced its path back to likely globular clusters.
As for what caused the increase in speed, researchers ruled out a supernova as evidence of a supernova remnant, based on X-ray observations. LP400-22 may have been involved in an interaction with other star systems inside the stellar cluster or was once part of a trinary star system that was disrupted by a black hole within the cluster.
Runaway Stars Could Lead To New Insights On The Galactic Center’s Black Hole, Stellar Clusters
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