Rarity in Space Provides Insights to Evolution


February 1, 2023—A rarity in space has been discovered: the remnants of a quiet supernova. The cause of this oddity is that a Be star in a binary system (CPD-29 2176) accreted enough mass from its companion star that when the companion star eventually exploded, it ejected very little mass. The result of this “ultra-stripped” supernova is the orbit of the system was not significantly changed—the Be star remained in its circular orbit. This discovery is so critical to our understanding of the variability of stellar evolution that today, Nature published the research paper “A high-mass X-ray binary descended from an ultra-stripped supernova,” authored primarily by Dr. Noel Richardson (assistant professor of Physics and Astronomy at Embry-Riddle Aeronautical University).
How did this rare data come to be collected in the first place? An X-ray outburst was observed with the SWIFT space telescope, but when scientists went to collect photometric data on the neutron star, there was another star in front of it. Dr. Herbert (“Bert”) Pablo, currently the staff astronomer at the American Association of Variable Star Observers (AAVSO), and a co-author of the Nature-published paper, was at the time a postdoctoral fellow with the BRITE-Constellation project at the University of Montreal, where he was consulted on the “offending” object. Pablo recommended that spectra instead of photometry should be collected, to get proof that the Be star and neutron star were related and to gather insights into the Be star’s motion. Pablo contacted Richardson, and they proposed multiple cycles of time for observations on the Cerro Tololo Interamerican Observatory’s CHIRON instrument in Chile to get the spectra. Richardson imparted, “Bert was instrumental in this discovery and pushing the study along after identifying that we should pursue it spectroscopically.”
What happened after this data was collected? Enter Clarissa Pavao, an undergraduate at Embry-Riddle keen to be involved in research. Richardson passed the data to Pavao to analyze. “Clarissa fit an orbit and it seemed circular rather than elliptical. I was thinking that a system with a neutron star should have had some sort of kick during the supernova that led up to the current day,” explained Richardson of his first indication that this system was unusual compared to most Be X-ray binaries.
Over the next million years, the Be star that collected most of the mass of the x-ray outburst is expected to lose its mass and explode similarly to its companion, so that eventually both stars will be neutron stars in a smaller, still-circular orbit with one another. According to Richardson, he and Pavao aim to “better characterize the current bright star in the system.” Pavao notes, “This system has a very interesting evolution, so we would like to know more about each star and hopefully find out more information.”
Contributing to scientific discoveries can be done as a student, professional, or citizen scientist. Pavao’s advice to undergraduate students pursuing a scientific career is to actively seek out research opportunities. “You must look past the fear [of rejection] and just think about how cool and exciting scientific research is and what knowledge you will gain from participating.” If you want to help advance research without a formal education, there are avenues for that too, such as being a volunteer observer with AAVSO, the international nonprofit organization where Pablo manages and maintains the organization’s open-source and verified databases, other resources for professional research, and tools for its community of citizen scientists and amateur astronomers. AAVSO even has an Eclipsing Binaries Observing Section dedicated to connecting and helping those interested in this niche science. AAVSO meets the data needs of professional astronomers by educating interested individuals on how to collect stellar photometry and spectra and submit them to the organization’s open-source databases, and by alerting these volunteer observers to the stars on which their time and contributions will be most valuable. 
Increasing our collective knowledge about the life cycles of varying stars and their relationships to one another are important components to understanding the continuous evolution of the Universe. As humans, we are curious to know our place in the Universe and what happens outside of our own solar system. Curiosity drove us to discover that the Earth is not flat and orbits around the Sun, that our small solar system is part of a whole galaxy, and that there are trillions of galaxies. It is the quest for knowledge that inspires us to learn what else is happening in the Universe, and what occurs before and after our existence. Pablo believes that binary star systems are crucial to our understanding of stellar evolution.

About AAVSO:
The American Association of Variable Star Observers (AAVSO) is an international nonprofit organization of citizen scientists and professional astronomers working together to increase the knowledge of the universe through education and by conducting variable star photometry and spectroscopy, as well as exoplanet observations. AAVSO's mission is to enable anyone, anywhere, to participate in scientific discovery through variable star astronomy. Visit us at https://www.aavso.org/. For more information on the AAVSO’s Eclipsing Binaries Observing Section, visit https://www.aavso.org/aavso-eclipsing-binaries-section.

About the paper
"A high-mass X-ray binary descended from an ultra-stripped supernova"
Authors: Noel D. Richardson (Embry-Riddle Aeronautical University, Prescott Campus), Clarissa M. Pavao (Embry-Riddle Aeronautical University, Prescott Campus), Jan J. Eldridge (University of Auckland), Herbert Pablo (AAVSO), André-Nicolas Chené (Gemini Observatory), Peter Wysocki (Georgia State University), Douglas R. Gies (Georgia State University), George Younes (NASA Goddard Space Flight Center; The George Washington University), & Jeremy Hare (NASA Goddard Space Flight Center)
Published in Nature 614, 45–47 (2023)
Abstract available at https://www.nature.com/articles/s41586-022-05618-9
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