Groundbreaking Discovery of Vampire Star in M67 Cluster

Astrosat and Vampire star

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Context:

Researchers have made a groundbreaking discovery of a vampire star in the star cluster M67 located in the constellation Cancer, that has been rejuvenating its youth by sucking up material from a companion.
The study provides rare insights into the binary star evolution process and provides an important missing link in the rejuvenation in these stars.

Details:

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.
Scientists studied the vampire star WOCS 9005 in the M67 cluster using spectroscopy, revealing its surface chemistry is rich in heavy elements like barium, yttrium, and lanthanum.
The team used data from the GALAH survey and the HERMES spectrograph, finding the heavy elements typical of asymptotic giant branch (AGB) stars, which are more evolved and massive than WOCS 9005.
The presence of these heavy elements suggested WOCS 9005 was polluted by a companion star that had gone through its AGB phase and become a white dwarf.
This makes WOCS 9005 the first barium blue straggler star discovered in the M67 cluster.
The team confirmed a small white dwarf companion using the Ultra-Violet Imaging Telescope (UVIT) on AstroSat, detecting significant UV brightness from the companion.
Theoretical calculations validated that mass transfer from the AGB star through the wind was responsible for the heavy element pollution and rejuvenation of WOCS 9005.

What is Mass transfer in a Binary system?

Mass transfer in a binary system occurs when material from one star, an evolved star like an asymptotic giant branch (AGB) star, is transferred to its companion star. This process can suggestively alter the companion's composition and appearance, often rejuvenating it, as seen in the case of blue straggler stars.

About Vampire Star:

Vampire stars, also known as blue straggler stars (BSS), are found in star clusters and appear younger than their neighboring stars, challenging simple stellar evolution models. These stars are naturally in pairs, known as symbiotic binaries, where the smaller star consumes material from its companion. Over time, the sucking star becomes larger and turns into a blue straggler.

Recent Findings:

Object of Study	Vampire star in M67, called WOCS 9005
Location	Open cluster in the constellation Cancer
Key Discovery	Atmosphere rich in heavy elements like barium, yttrium, and lanthanum
Significance of Elements	Naturally associated with older, more massive stars in their final stages
Expected Chemistry	Similar to our Sun
Actual Chemistry	Rich in heavy elements, indicating pollution from a companion star
Detection Method	AstroSat’s Ultraviolet Imaging Telescope (UVIT)
Ultraviolet Emissions	Significant emissions detected
Conclusion	WOCS 9005 consumed barium-rich material, appearing as a rejuvenated blue straggler star

About ASTROSAT

Launch Date	September 2015
Mission	India’s first dedicated multi-wavelength space observatory
Major ISRO Missions Preceding ASTROSAT	Chandrayaan-I and Mangalyaan
Orbit	Low earth equatorial orbit at altitude of 650 km
Key Instruments on Astrosat	Ultraviolet Imaging Telescope (UVIT) Large Area X-ray Proportional Counter (LAXPC) Soft X-ray Telescope (SXT) Cadmium Zinc Telluride Imager (CZTI) Scanning Sky Monitor (SSM)
Observation Capabilities	Celestial bodies like cosmic X-ray sources and distant stars in different wavelengths simultaneously
Spectral Observation Range	Ultraviolet, optical, low and high energy X-ray components of the electromagnetic spectrum
Mission Life	5 years
Significance	Made India a member of an elite group of nations with space observatories (US, Japan, Russia, Europe)

READ IN DETAIL ABOUT- AstroSat MISSION

About Indian Institute of Astrophysics (IIA)

Headquarters	Bengaluru, India
Funding	Wholly funded by the Department of Science and Technology, Government of India
Primary Research Areas	Astronomy, Astrophysics, and related fields
Network of Laboratories and Observatories	Kodaikanal Solar Observatory, Vainu Bappu Observatory (Kavalur), Gauribidanur Radio Observatory, Indian Astronomical Observatory (Hanle), Hosakote
Contribution to Astrosat	Developed the Ultra-Violet Imaging Telescope (UVIT)
Areas of Research	Sun & Solar System Stellar Astronomy Galactic Astronomy Extragalactic Astronomy & Cosmology Theoretical Astrophysics & Physics Techniques & Instrumentation Space Astronomy