SANTA CRUZ DE TENERIFE, June 22 (EUROPA PRESS) –
An international collaboration, in which the Instituto de Astrofísica de Canarias (IAC) participates, has managed to determine with an unprecedented level of precision the mass, age and rotation profile of the nucleus of a pulsating massive star. Called HD 192575, it has been observed by NASA’s TESS satellite continuously for more than a year.
The results shed new light on how these types of stars are internally structured and how they evolve until their death, when they explode as supernovae and form neutron stars and black holes. The scientific team has also used observations made with the Mercator telescope located at the Roque de los Muchachos Observatory in La Palma. The study is published in the journal ‘Nature Astronomy’.
Massive stars are extremely short-lived in the Universe; they have very dense and hot nuclei, burn their fuel fast and die young. When these types of stars collapse, they generate a violent supernova explosion and, depending on their mass and the structure of their core, end up forming a neutron star or a black hole. For this reason, massive stars are key, not only to understand the physical processes responsible for their evolution, but also to resolve other fundamental questions about the Universe.
An international study, led by the KU Leuven (Belgium), has applied the asteroseismology technique to study the variability of the pulsating star HD 192575 that NASA’s TESS satellite has been observing continuously for more than a year. Astroseismology is the study of waves inside stars.
These waves are affected by their internal properties and, in particular, by the rotation of their nucleus, which allows access to information about the physical processes that occur inside the stars from their brightness changes. At present, these mechanisms remain uncalibrated, but they need to be understood to predict the ultimate fate of stars.
The study of massive stars requires high-precision, long-lived data for advanced analysis. Thanks to the TESS mission, the study of HD 192575 has reached an unprecedented level of detail. “Space telescopes like TESS, and Kepler before it, are able to observe stars almost continuously for long periods of time, making them excellent tools for astroseismologists,” says Siemen Burssens, a KU Leuven researcher who led the study. “TESS is especially important for asteroseismology of massive stars, since previous space telescopes generally avoided bright massive stars,” he adds.
The novel modeling tools developed in this work have made it possible to determine that the mass of HD 192575 is about 12 times that of the Sun and that it is approximately 15 million years old. This makes HD 192575 one of the rarest and most massive stars to have been modeled by asteroseismology. Furthermore, its core has been found to rotate about 1.5 times faster than its surface layers, something that current models do not predict.
As Dominic Bowman, a researcher at KU Leuven and co-author of the study, explains, “Like a ballet dancer who spins faster by bringing her arms outstretched closer to her body, the nucleus of HD 192575 should rotate faster as it ages and shrinks. However, the core’s rotation rate that we have measured is not as fast relative to its outer shells as predicted by non-magnetic models of rotation.”
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The TESS data combined with that of the Mercator telescope, located at the Roque de los Muchachos Observatory on La Palma, and ESA’s Gaia space mission, allowed the team to also accurately infer the amount of chemical elements inside HD. 192575 and the mass of its core, which are key to predicting the future evolution of the star and its explosion as a supernova.
The precise determination of HD 192575’s core mass, age, and rotation profile make this massive star a unique calibration point for adjusting stellar evolution models, which are ultimately keys to understanding the impact of massive stars in the evolution of galaxies and the infancy of the Universe.
“This is just the beginning of a very promising path that involves carrying out a study similar to the one carried out on HD 192575 on a much larger sample of massive stars in our galaxy”, comments Sergio Simón-Díaz, IAC researcher, co-author of the article. and Principal Investigator (PI) of the IACOB project, an international collaboration led by the IAC that has been using various telescopes from the Canary Islands Observatories for more than 15 years to create the largest database of spectra of massive stars of the Milky Way ever built. .
“The continued efforts made by the IACOB project will be decisive to get the most out of the data from the TESS satellite and jump from the pioneering study on HD 192575 to several hundred stars tens of times more massive than our Sun”, concludes Simón-Díaz.
