December 18, 2023 In the grand finale of massive stars, their deaths unfold as spectacular supernovae, illuminating the cosmos with brilliance surpassing entire galaxies. Yet, within this cosmic spectacle, scientists have long observed a mysterious absence of hydrogen in a significant number of supernovae, hinting at an elusive population of hydrogen-poor stars. Now, a dedicated survey has unveiled 25 of these elusive stars, shedding light on their existence and providing a crucial key to understanding the mechanisms behind such supernovae.
Researchers from the University of Toronto and the Institute of Science and Technology Austria, led by astronomers Maria Drout and Ylva Götberg, conducted an extensive survey to identify stripped-envelope supernovae, characterized by their hydrogen-poor nature. The study focused on binary star systems, where one star siphons off the hydrogen envelope from its companion, resulting in a helium-rich star that contributes to the hydrogen-poor supernova phenomenon.
The team utilized the Swift Ultra-Violet/Optical Telescope to survey millions of stars in the Large and Small Magellanic Clouds, dwarf galaxies orbiting the Milky Way, between 2018 and 2022. The survey identified 25 candidates with unusual ultraviolet profiles, and follow-up observations using the Magellan Telescopes confirmed their distinct chemical compositions.
The stripped-envelope stars, located in the mid-range of stellar mass (between 8 and 25 times that of the Sun), have proven challenging to detect due to the diminished visible light emitted after losing their outer layers. Observations in ultraviolet light provided the necessary sensitivity to uncover these elusive stars, offering crucial insights into their characteristics.
The discovery challenges existing theoretical frameworks and underscores the importance of these intermediate-mass helium stars, which serve as precursors to neutron stars and potential progenitors of neutron star mergers. The team emphasizes that while this work marks a significant step forward, further studies are underway to delve deeper into the nature of these stars and expand the search for additional helium-rich candidates.
Götberg notes, “Our work may be one of the first attempts, but there should be other ways possible,” emphasizing the collaborative nature of astronomical research as the scientific community continues to explore the mysteries of the cosmos.
The research, published in Science, represents a milestone in understanding the missing population of intermediate-mass, stripped helium stars and their role in the captivating dance of supernovae.
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