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Abstract of presentation: https://eas2025programme.kuoni-congress.info/pdf/presentation/the-new-mobile-telescope-at-the-chara-array 

Abstract: https://eas2025programme.kuoni-congress.info/pdf/presentation/the-chara-array-building-towards-the-michelson-array 

Abstract: https://baas.aas.org/pub/2025n2i302p27/release/1 

Abstract: https://horizons-olbin.sciencesconf.org/file/1181666 

Context.Many classical Be stars acquire their very rapid rotation by mass- and angular-momentum transfer in massive binaries, marking the first phase of the evolutionary chain. Later-stage products, such as Be+subdwarf- and Be+neutron-star binaries (Be X-ray binaries), are also well known, although the search for definitive proof of Be+white dwarf companions is ongoing. Short-lived intermediate-phase objects, that is, binaries past the interaction stage but with a donor star that has not yet reached the end of its evolution or contraction, have only recently been discovered. Aims.The main hallmark of this kind of binary is a system of absorption lines with low width, significant radial-velocity variations, and peculiar relative line strengths. Data archives and the literature can be searched for additional candidates exhibiting this pattern, and follow-up observations can be obtained in order to increase the number of these systems with quantitatively known orbits, providing a basis for an initial statistical investigation and to develop observational strategies for abundance analyses. Methods.We identified 13 candidates at various confidence levels. To verify their nature, we derived orbital elements from new high-quality spectra and interferometric observations where possible. We also performed qualitative analyses of other basic parameters, and preliminarily evaluated indicators of advanced stages of nucleosynthesis. Results.Adding to the two known systems identified as classical Be star+pre-subdwarf binaries (LB-1 andHR 6819), we confirm two more (V742 Cas,HD 44637) with interferometry, with V742 Cas setting a new record for the smallest visually observed angular semi-major axis, ata = 0.663 mas. Two further systems (V447 Sct,V1362 Cyg) are not resolved interferometrically, but other evidence puts them at the same confidence level as LB-1.V2174 Cygis a candidate with very high confidence, but was not observed interferometrically. The remaining systems are either candidates with varying levels of confidence –mainly due to the lack of available spectroscopic or interferometric observations for comparison with the others and orbit determination– or could be rejected as candidates with the followup observations. Conclusions.Of a mostly magnitude-complete sample of 328 Be stars, 0.5–1% are found to have recently completed the mass overflow that led to their formation. Another 5% are systems with a compact subdwarf companion –that is, they are further evolved after a previous overflow– and a further 2% possibly harbor white dwarfs. All these systems are early B subtypes, but if the original sample is restricted to early subtypes (136 objects), these percentages increase by a factor of about 2.5, while dropping to zero for the mid and late subtypes (together 204 objects). This strongly suggests that early-type versus mid- and late-type Be stars follow differently weighted channels to acquire their rapid rotation, namely binary interaction versus evolutionary spin up. 

The complex binary system β Lyr A has an extensive observational dataset: light curves (from far UV to far IR), interferometric squared visibility, closure phase, triple product measurements, spectral-energy distribution, high-resolution spectroscopy, differential visibility amplitude, and also a differential phase. In particular, we used spectra from the Ondřejov 2m telescope from 2013 to 2015 to measure the emission in H α , He  I , Si  II , Ne  I , or C  II lines, and differential interferometry by CHARA/VEGA from the 2013 campaign to measure wavelength-dependent sizes across H α and He  I 6678. This allowed us to constrain not only optically thick objects (primary, secondary, accretion disc), but also optically thin objects (disc atmosphere, jets, shell). We extended our modelling tool, Pyshellspec (based on Shellspec; a 1D local thermodynamical equilibrium radiative transfer code), to include all new observables, to compute differential visibilities/phases, to perform a Doppler tomography, and to determine a joint χ 2 metric. After an optimisation of 38 free parameters, we derived a robust model of the β Lyr A system. According to the model, the emission is formed in an extended atmosphere of the disc, two perpendicular jets expanding at ∼700 km s −1 , and a symmetric shell with the radius ∼70  R ⊙ . The spectroscopy indicates a low abundance of carbon, 10 −2 of the solar value. We also quantified systematic differences between datasets, and we discuss here alternative models with higher resolutions, additional asymmetries, or He-rich abundances.