Vampire Star, GALactic Archaeology with HERMES ( GALAH ) & HERMES

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Recently, a team of astronomers from the Indian Institute of Astrophysics (IIA), an autonomous institute of the Department of Science & Technology, Government of India made a groundbreaking discovery of a vampire star in M67, that sheds light on a complex rejuvenation process, known as mass-transfer in a binary system.

Vampire stars, known to astronomers as blue straggler stars (BSS), are identified easily in star clusters. These stars defy simple models of stellar evolution and show many characteristics of younger stars. 

The team made use of the Ultra-Violet Imaging Telescope (UVIT) onboard AstroSat, India's first multi-wavelength satellite launched in 2015, for their study. Using the UVIT on AstroSat, the scientists took images of the vampire star and estimated its UV brightness. 

These heavy elements are rare and are found in a class of stars called ‘asymptotic giant branch (AGB) stars’, where abundant neutrons for a slowly occuring neutron capture process (s-process) are available to produce these heavy elements from lighter ones. This process is responsible for creating approximately half the atomic nuclei heavier than Iron. However, these AGB stars shed their outer layers enriched with heavy elements into their surroundings before ending their lives as white dwarfs (WDs). However, these AGB stars are more massive and evolved than WOCS 9005, leading to a puzzle.

GALactic Archaeology with HERMES (GALAH):

The GALactic Archaeology with HERMES (GALAH) survey is a Large Observing Program using the HERMES instrument with the Anglo-Australian Telescope. HERMES provides simultaneous spectra for 400 stars at a time.

HERMES is a multi-object spectrograph commissioned at the Anglo-Australian Telescope (AAT) in 2014 that covers four optical bands simultaneously at a spectral resolution of ~28,000. 

Blue Straggler Stars (BSS):

Blue stragglers are so named because they seemingly lag behind in the aging process, appearing younger than the population from which they formed. While they have been detected in many distant star clusters, and among nearby stars, they never have been seen inside the core of our galaxy.

It is not clear how blue stragglers form. A common theory is that they emerge from binary pairs. As the more massive star evolves and expands, the smaller star gains material from its companion. This stirs up hydrogen fuel and causes the growing star to undergo nuclear fusion at a faster rate. It burns hotter and bluer, like a massive young star.

  1. PIB
  2. GALAH Survey
  3. HERMES
  4. NASA

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