Authors:

Jeremy Switzer

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About Paper:

Low- and intermediate-mass stars reach the final stage of their lives on the Asymptotic Giant Branch (AGB), where they pulsate with periods ranging from several hundred to over one thousand days. Stellar evolution models predict that only stars with initial masses between roughly 1.4 and 3.2 times the mass of the Sun can bring carbon from their cores to their surfaces, 77 producing carbon-rich stars. Lower-mass stars remain oxygen-rich because they cannot produce enough carbon, while higher-mass stars convert carbon into oxygen before it reaches the surface. This project analyzed how stars vary in brightness using data from the Palomar Gattini-IR (PGIR) time- domain survey and identified eight AGB stars with pulsation periods exceeding 1000 days. Follow-up observations with near-infrared spectroscopy at the NASA Infrared Telescope Facility (IRTF) revealed that three of these extremely long-period stars are carbon-rich. According to stellar evolution models, stars with such long periods should be too massive to become carbon-rich. These findings challenge existing models of stellar evolution, suggesting that some stars can become carbon-rich at higher masses or longer periods than previously thought. The discovery highlights gaps in theoretical models and provides new targets for studying the late stages of stellar evolution in more detail.

Source:

Columbia / Archaeology / 2026

Topics:

No topics listed

Co-authors:

Jeremy Switzer