A TEAM of astronomers from the Indian Institute of Astrophysics (IIA), an autonomous institute of the Department of Science and Technology, made a groundbreaking discovery of a vampire star in the star cluster M67 using data from the UltraViolet Imaging Telescope, on board AstroSat, India’s first dedicated space observatory. M67 is a collection of over 500 stars that are loosely gravitationally bound, a grouping known as an open cluster. The vampire star, called WOCS 9005, in the star cluster M67, is located in the constellation Cancer. It has been rejuvenating its youth by sucking up material from a companion.

 

The findings, to be published in The Astrophysical Journal Letters, shed light on a complex rejuvenation process, known as mass transfer in a binary system. Using spectroscopy, a technique where the light ofthestarisdispersedinto itscoloursliketherainbow, the team from IIA studied thesurfacecompositionof WOCS 9005. “This star is expected to show chemistry very similar to our Sun, but we found that its atmosphere is rich in heavy elements such as barium, yttrium, andlanthanum,” saidlead author Harshit Pal, from IIA, who carried the study as a part of his MS thesis project at IISER Berhampur.

 

These heavy elements are rare and are found in a classofstarscalled‘asymptotic giant branch (AGB) stars’, where abundant neutrons for a slowly occurring neutron capture process (s-process) are available to produce these heavy elements from lighterones.But,these AGB stars end their lives as white dwarfs (WDs) by shedding their outer layers which are enriched with heavy elements into their surroundings.However, these AGB starsa re more evolved than WOCS 9005, leading to a puzzle.