The Colloquium takes place every Wednesday at 11:15 AM - Warsaw Copernicus Astronomical Centre online by means of Zoom platform. The Colloquium is given in English and chaired by dr Stanisław Bajtlik (bajtlik@camk.edu.pl). People from outside of the Copernicus Center are very welcome to participate. For technical detailes please contact Dr. Stanislaw Bajtlik.
Bogumił Pilecki (CAMK, Warsaw)
Since 2020, we have been systematically identifying and characterizing double-lined (SB2) binary Cepheids in the Large Magellanic Cloud, the Small Magellanic Cloud, and the Milky Way. Our primary detection method exploits the apparent overbrightness of Cepheids as a signature of a luminous companion, complemented by searches for systems composed of two Cepheid components. This effort has increased the known sample of confirmed SB2 Cepheids to 62 objects —an order-of-magnitude improvement over previous numbers— and expanded the number of double-Cepheid binaries from one to ten. For 37 systems, we detected anticorrelated orbital motion of both components, providing definitive proof of binarity. Preliminary orbital solutions have been derived for 24 systems with periods up to seven years, and full spectroscopic orbits have been determined for 15 systems with periods up to 3 years. I will present the orbital and physical properties of these binaries and discuss their implications for Cepheid multiplicity, evolution, and origin. Remarkably, at least 10% of them exhibit evidence of past mergers, suggesting that a significant fraction of Cepheids may form through binary interaction. I will also address the possible consequences of these findings for calibrating the Cepheid distance scale.
Journal Club takes place on Mondays at 11:15 AM in the Seminar Room. The presentation is given in English and is chaired by Journal Club Coordinators. Anyone interested in giving a Journal Club talk is encouraged to contact the email: journalclub(@camk.edu.pl).
Gergely Hajdu (NCAC, Warsaw)
based on https://ui.adsabs.harvard.edu/abs/2026ApJ...998L..27V/abstract from van Dokkum et al. (Feb 2026).
