Abstract:
Juraj Jonák and Dr. Denis Mourard have requested AAVSO observers’ assistance in obtaining photometry and spectroscopy of several bright detached binary variable stars in support of their study of these targets to determine their visual trajectories and fundamental stellar parameters, crucial for understanding stellar evolution, interiors, and environments. Jonák writes: “With the recent installment of the CHARA/SPICA interferometer, located at Mt. Wilson, CA, USA we aim to observe a large sample of bright detached binaries in order to determine their visual trajectories. The goal is to use a robust combined model including interferometry, spectroscopy and/or photometry, which will open access to a wide range of direct mass determination and fundamental ingredients of the stellar evolution models.”
Justification:
Jonák writes: “Fundamental stellar parameters are the primary data required for an in-depth under- standing of stellar evolution, interiors, and environments…Spectroscopic binary systems provide direct information on stellar mass and structure from the mutual interaction via radial velocity of orbital motion. However, this method is highly dependent on the inclination of the orbit, which cannot be determined purely from spectroscopy…This dependence can be alleviated by combination with observations of eclipses…In fact, the method of simultaneous modelling of spectroscopy and photometry has been a common method since the 1970s. A different approach is utilising interferometric measurements. Although these don’t necessarily require viewing the system edge-on, they demand other constraints on the system…Naturally, the observations are not mutually exclusive, and in fact, using all of them can improve our understanding of the system. The SPICA team has 5 nights per month allocated for observing with the CHARA/SPICA instrument from now through July 2024. However, as our goal is to study the entire orbit, simultaneous observations are not required or preferred.” Added in September 2024: Although the CHARA/SPICA observing time has passed, photometry and spectroscopy on these targets is still requested until further notice. This Alert Notice will be updated when coverage is no longer needed.