Kavli Affiliate: Saul A. Rappaport
| First 5 Authors: Tajan H. de Amorim, Tajan H. de Amorim, , ,
| Summary:
With its two stellar eclipses and two disk attenuations per binary orbit,
V658 Carinae stands out as the first clear eclipsing Be + sdOB system. This
rare alignment offers a unique opportunity to probe the structure and dynamics
of a Be star disk with unprecedented detail. In this study, we present the most
comprehensive observational dataset and modeling effort for this system to
date, including optical, near-infrared, and ultraviolet spectroscopy,
space-based photometry, and optical polarization. Using a new ray-tracing code,
we apply a three-component model, consisting of an oblate, rapidly rotating Be
star, a symmetric circumstellar disk, and a compact stripped companion, to
reproduce the system’s light curve, polarization, and spectral features. Our
analysis yields precise constraints on the stellar and disk parameters,
determining its status as the second known late-type Be + stripped star, and
also provides strong spectroscopic evidence for a tenuous circumsecondary
envelope. Despite the model’s overall success, several key observables, such as
the $H_alpha$ equivalent width and the secondary attenuation, remain poorly
reproduced, pointing to the need for more sophisticated modelling. In
particular, future improvements should incorporate the companion’s radiative
feedback on the disk and account for asymmetric disk structures expected by the
gravitational interaction with the companion. Owing to its unique geometry and
rich diagnostics, V658 Car establishes itself as a benchmark system for Be
stars (and rapid rotators in general), stripped stars, post-RLOF massive
binaries, and circumstellar disk structures.
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