Ricardo Salinas (CAMK/Araucaria, Warsaw)
While adaptive optics is the most widespread method to compensate for atmospheric turbulence, these methods are particularly difficult to implement in the optical regime given the technical challenges imposed by the short coherence times. An alternative to reach the diffraction limit of an optical telescope is provided by speckle interferometry, where, instead of real-time corrections, observations are obtained in timescales similar to the coherence time (a few ms), and the diffraction limit is recovered via a post-hoc reduction in Fourier space. In 2019, the Gemini telescopes commissioned two speckle interferometers, Zorro and 'Alopeke, owned by NASA Ames, which have remained as "permanent visiting" instruments since then. In this talk I will present the characteristics of these instruments, to then present a number of science cases where these instruments are particularly suited, mostly leaning to my own research on RR Lyrae in binary systems, and blue stragglers in hierarchical triplets.
Winter break
Winter break
Rolf Chini (CAMK, Warsaw, Araucaria Project)
The project deals with the rotational velocity (v sin i) of 238 southern O stars. The sample contains 130 spectroscopic single stars (C), 36 single-lined binaries (SB1), and 72 SB2 systems (including eight triples). The overall v sin i statistics peaks at slow rotators (40–100 km/s) with a tail towards medium (100–200 km/s) and fast rotators (200–400 km/s). Binaries, on average, show increased rotation, which differs for close (Porb < 10 d) and wide binaries (10 d < Porb < 3700 d), and for primaries and secondaries. The spin-up of close binaries is well explained by the superposition of spin-orbit synchronization and mass transfer via Roche-lobe overflow. The increased rotation of wide binaries, however, can be caused by various spin-up mechanisms. Timescale arguments lead us to favor a scenario where wide O binaries are spun-up by a combination of cloud or disk fragmentation, which lays the basis of triple and multiple stars, and the subsequent merging or swallowing of low-mass by higher-mass stars or proto-stars.
