| Name: | DEBASISH DUTTA |
| Affiliation: | Indian Institute of Technology Palakkad |
| Conference ID : | ASI2024_180 |
| Title : | On the evolutionary nature of puffed-up stripped star binaries and their occurrence in stellar populations |
| Authors : | Debasish Dutta (1) and Jakub Klencki (2) |
| Authors Affiliation: | 1) Department of Physics, Indian Institute of Technology Palakkad, Kerala, India
2) European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany |
| Mode of Presentation: | Poster |
| Abstract Category : | Stars, Interstellar Medium, and Astrochemistry in Milky Way |
| Abstract : | The majority of massive stars are formed in binary or multiple systems at some point during their life they interact with their companions via mass transfer. This interaction typically leads to the primary star shedding its outer envelope, resulting in the formation of what is known as a "stripped star". Classically, stripped stars are expected to quickly contract to become hot and compact helium stars that emit most of their light in the (near) UV. Surprisingly, recent optical spectroscopic surveys have unveiled a number of these stripped stars that are notably larger and cooler, appearing almost "puffed up" in post-interaction binary systems. This discovery is somewhat puzzling given the normally transient nature of the phase in which stripped stars contract. In this study, we employed the 1D stellar evolution code MESA to calculate grids of binary models at different metallicities. Contrary to previous assumptions, our computations reveal that stripped stars quickly regain thermal equilibrium shortly after the end of mass transfer, remaining as relatively large "puffed-up" stripped stars (PSS) with hydrogen-shell burning as their primary energy source. The duration of the bloated phase is approximately 10% of the core-He burning lifetime and up to 100 times more than the thermal timescale. Additionally, we explored various factors such as orbital period, mass ratio, wind mass loss rate and semiconvection. We further carried out a simple binary population synthesis calculation to estimate how many such stars one can expect to find in future optical surveys. Our results indicate that tens to hundred of puffed-up stripped stars in post-interaction binaries may be hiding in the MS population, disguised as "normal" stars. We overview which observables may help to reveal their true nature (surface abundances, gravities, companion stars) and briefly discuss the observational resources needed to achieve that. |
