Credit: Navid Marvi, courtesy of the Carnegie Institution for ScienceNew findings verify existence of hot helium stars long-thought to be at the heart of hydrogen-poor supernovae and neutron star mergers.Astronomers at the University of Toronto have discovered a population of massive stars that have been removed of their hydrogen envelopes by their companions in binary systems. The findings, published on December 14 in the journal Science, shed light on the hot helium stars that are believed to be the origins of hydrogen-poor core-collapse supernovae and neutron star mergers.Theory vs. Reality in Stellar EvolutionFor over a years, researchers have actually thought that around one in three massive stars are stripped of their hydrogen envelope in binary systems. Immler (Goddard) and M. Siegel (Penn State)Binary Stripped Stars and Cosmic PhenomenaBinary stripped stars have been previously stimulated to discuss why a third of core-collapse supernovae consist of much less hydrogen than a typical explosion of a Red Supergiant star. These star systems are also believed to be needed to form neutron star mergers, like those that emit gravitational waves found from Earth by the LIGO experiment.In fact, the scientists believe that a couple of items in their current sample are stripped stars with neutron star or black hole buddies. She fulfilled fellow co-author Ylva Götberg, now Assistant Professor at the Institute of Science and Technology Austria (ISTA), at a conference, who had recently constructed new theoretical designs of what these stars need to look like.Drout, Götberg, and their partners created a new survey to look in the ultraviolet part of the spectrum where extremely hot stars discharge most of their light.
This artists impression demonstrates how hot, high-mass and fantastic stars progress. The more massive more vibrant star broadens initially, till the external layers start to strongly feel the gravitational pull of the buddy. The companion then begins to suck product from the main star. When the primary has been removed from its whole hydrogen-rich envelope it diminishes. Credit: Navid Marvi, thanks to the Carnegie Institution for ScienceNew findings validate existence of hot helium stars long-thought to be at the heart of hydrogen-poor supernovae and neutron star mergers.Astronomers at the University of Toronto have actually discovered a population of massive stars that have actually been stripped of their hydrogen envelopes by their buddies in binary systems. The findings, released on December 14 in the journal Science, clarified the hot helium stars that are thought to be the origins of hydrogen-poor core-collapse supernovae and neutron star mergers.Theory vs. Reality in Stellar EvolutionFor over a years, researchers have actually thought that roughly one in three huge stars are removed of their hydrogen envelope in binary systems. Till now, only one possible candidate had been recognized.”This was such a big, glaring hole,” states co-lead author Maria Drout, an Assistant Professor in the David A. Dunlap Department of Astronomy & & Astrophysics and a Dunlap Institute for Astronomy & & Astrophysics Associate at the University of Toronto.Implications for Future Research”If it turned out that these stars are unusual, then our entire theoretical framework for all these different phenomena is wrong, with ramifications for supernovae, gravitational waves, and the light from remote galaxies,” Drout says. “This finding reveals these stars really do exist.””Going forward, we are going to have the ability to do a lot more comprehensive physics with these stars,” Drout says. “For example, predictions for how lots of neutron star mergers we should see are reliant on the homes of these stars, such as just how much product comes off of them in excellent winds. Now, for the very first time, well have the ability to measure that, whereas individuals have actually been theorizing it before.”Surveys performed by NASAs Swift-UVOT telescope offer the most detailed summaries ever recorded in ultraviolet light of the Small and large Magellanic Clouds, the 2 closest major galaxies to our own. The researchers utilize this ultraviolet dataset to determine the prospect systems that they targeted for this paper. Credit: NASA/Swift/S. Immler (Goddard) and M. Siegel (Penn State)Binary Stripped Stars and Cosmic PhenomenaBinary stripped stars have actually been previously evoked to discuss why a 3rd of core-collapse supernovae consist of much less hydrogen than a normal surge of a Red Supergiant star. Drout and her associates propose that these newly found stars will ultimately blow up as hydrogen-poor supernovae. These galaxy are likewise believed to be essential to form neutron star mergers, like those that produce gravitational waves found from Earth by the LIGO experiment.In reality, the researchers think that a few things in their current sample are removed stars with neutron star or black hole companions. These objects are at the stage instantly before they end up being double neutron star or neutron star plus great void systems that might eventually merge.Lead co-author Maria Drout (University of Toronto) with the Magellan Telescope at Las Campanas Observatory. Credit: Tom Holoien/Maria DroutStellar Partnerships and Evolution”Many stars become part of a cosmic dance with a partner, orbiting each other in a binary system. Theyre not singular giants but part of vibrant duos, connecting and influencing each other throughout their life times,” says Bethany Ludwig, a PhD trainee in the David A. Dunlap Department of Astronomy & & Astrophysics at the University Toronto and the 3rd author on this paper. “Our work sheds light on these interesting relationships, revealing a universe that is far more interconnected and active than we formerly pictured.””Just as people are social beings, stars too, specifically the massive ones, are seldom alone,” Ludwig says.As stars evolve and broaden to become red giants, the hydrogen at the outer edges of one can be stripped by the gravitational pull of its companion– leaving a really hot helium core exposed. The process can take 10s of thousands, and even numerous thousands, of years.Study authors Bethany Ludwig, Anna OGrady, Maria Drout, and Ylva Götberg observing on the Magellan telescopes at Las Campanas Observatory in Chile, where they collected data for this research study. Credit: Y. GötbergChallenges in Detecting Stripped StarsStripped stars are tough to find because much of the light they release is beyond the noticeable light spectrum and can be blocked by dust in deep space or outshone by their companion stars.Drout and her collaborators started their search in 2016. Having actually studied hydrogen-poor supernovae throughout her PhD, Drout set out to find the removed stars thought to be at the heart of them throughout a NASA Hubble Postdoctoral Fellowship at the Observatories of the Carnegie Institution for Science. She met fellow co-author Ylva Götberg, now Assistant Professor at the Institute of Science and Technology Austria (ISTA), at a conference, who had actually recently built brand-new theoretical models of what these stars ought to look like.Drout, Götberg, and their partners created a new study to look in the ultraviolet part of the spectrum where very hot stars emit many of their light. While unnoticeable to the naked eye, ultraviolet light can be spotted by specialized instruments and telescopes.Using data from the Swift Ultra-Violet/Optical Telescope, the researchers collected brightnesses for countless stars in the Small and large Magellanic Clouds, 2 of the closest galaxies to Earth. Ludwig established the very first wide-field UV brochure of the Magellanic Clouds and used UV photometry to detect systems with unusual UV emissions, indicating the possible presence of a removed star.They carried out a pilot study of 25 objects, getting optical spectroscopy with the Magellan Telescopes at Las Campanas Observatory in between 2018 and 2022. They used these observations to demonstrate that the stars were hot, small, hydrogen-poor, and in binary systems– all consistent with their model predictions.Ongoing Research and Accessibility of DataCurrently, the researchers are continuing to study the stars recognized in this paper and expanding their search to find more. They will be looking both within close-by galaxies and within our own Milky Way with approved programs on the Hubble Space Telescope, the Chandra X-Ray Telescope, the Magellan Telescopes, and the Anglo-Australian Telescope. As part of this publication, all theoretical designs and data used to identify these stars have been made public and readily available to other scientists.For more on this discovery, see Cracking the Case of Cosmic Ghost Stars.Reference: “An observed population of intermediate-mass helium stars that have been stripped in binaries” by M. R. Drout, Y. Götberg, B. A. Ludwig, J. H. Groh, S. E. de Mink, A. J. G. OGrady and N. Smith, 14 December 2023, Science.DOI: 10.1126/ science.ade4970Collaborating institutions include the University of Toronto, the Observatories of the Carnegie Institution for Science, Max-Planck-Institut für Astrophysik, Anton Pannekoek Institute for Astronomy, Dunlap Institute for Astronomy & & Astrophysics, and Steward Observatory.
