Astronomers Unveil Stellar Impostor in S1 Binary System
Astronomers have discovered that the mass of the main star in the S1 binary system is significantly smaller than previously thought. By using advanced techniques, researchers determined the star's mass is only 4.1 times that of the Sun, challenging existing models of stellar evolution.
In the most precise measurement of the characteristics of the S1 binary system, researchers from the Institute of Radio Astronomy and Astrophysics (IRyA) of the UNAM, Morelia campus, determined that the mass of the main star of this object is 20 to 50 percent less than previously estimated.
Through the study — made up of the doctoral student in Astrophysics at IRyA, Jazmin Ordóñez Toro, researchers Laurent Raymond Loinard and Luis Felipe Rodríguez Jorge; as well as Sergio A. Dzib, from the Max Planck Institute in Germany — they reviewed the objects located in a star-forming region in the direction of the Ophiuchus constellation, approximately 450 light-years away from Earth.
Ordóñez Toro explained that a binary system is the name given to two stars that orbit each other. In this case, S1 reviewed almost two decades of data, including 28 sets of previously obtained information, and 7 recent observations from the Dynamical Masses of Young Stellar Multiple Systems with the VLBA Project (DYNAMO–VLBA). All of them using the Very Long Baseline Array (VLBA) in New Mexico, United States.
One of the fundamental parameters to know the structure, dynamics and diverse characteristics of a star is its mass; knowing it makes it possible to derive other variables that provide us more information about the behavior, structure, evolution and star formation, said the expert about the work published in The Astronomical Journal.
The general way to estimate the mass is with stellar evolution models, which are predictions based on indicators such as luminosity. To do this with more certainty, binary systems are used, since knowing their orbital dynamics makes it possible to obtain the information directly and precisely, said the Master of Science from the University of Guanajuato.
The S1 system has been observed since the 1990s in various wavelengths; it is known that they are young celestial bodies; that is, they are in their early stages of development, so they are difficult to see with a visible light telescope and that is why equipment is used to observe the infrared spectrum. Originally, the models indicated that the main star is approximately six times the mass of the Sun.
But the research team led by Ordóñez Toro used a technique called Very Long Baseline Interferometry (VLBI), which combines data from different radio telescopes distributed at great distances from each other. This method allowed them to determine that the star measures only 4.1 times that of the king star, significantly smaller than estimated.
According to the researcher, the assessment shows the importance of using advanced techniques and long-term observations to explain the unknowns of star formation, as the work redefines our perception of S1 and could have significant implications for refining theoretical models of early stellar evolution in the intermediate mass range.
The research also included Gisela Ortiz-León, from the National Institute of Astrophysics, Optics and Electronics; Marina A. Kounkel, from the University of North Florida; Josep M. Masqué, from the University of Guanajuato; N.X. Medina, from the German Aerospace Center; Phillip Galli, from the Universidade Cicade de São Paulo; Trent J. Dupuy, from the University of Edinburgh; and Luis H. Quiroga-Núñez, from the Florida Institute of Technology; all of them as part of the DYNAMO–VLBA project.
