Speaker
Description
About 30% of long-period variables exhibit a long secondary period (LSP) in their light curve. Their origin is still unclear.
About 15% of carbon stars are enriched in 13C and lack s-process elements. They are labeled as J-type stars. These chemical peculiarities challenge standard AGB models, suggesting that J-type stars may follow a different evolutionary sequence.
In this talk, I will bring these two mysterious a priori unrelated subclasses together. We report, for the first time, the detection of LSP among J-type carbon stars and provided physical constraints on the circum-stellar/-companion environment of a star experiencing a LSP. The dense spectral monitoring has allowed us to characterize the phase-dependent variability in the gas and dust densities along the line of sight. In the binary framework, the current prevailing scenario to explain the LSP, these periodic increases of column density further supported the presence of a trailing structure - such as an expanding wake - created by a close substellar companion.
These retrieved quantities and orbital configurations provide material for direct comparison with hydrodynamic simulations of AGB stars with a nearby substellar companion. Furthermore, the detection of LSP among the J-type stars raised new open questions about the impact of binary interactions on their evolutionary status.