Data: 23.01.2024

Marcin Wrona (PhD candidate, OAUW)

Eccentric ellipsoidal variables (heartbeat stars) in the OGLE project

Streszczenie:
In eccentric ellipsoidal variables (EEVs), brightness variations are primarily caused by the tidal deformation of at least one component, most notably visible near the periastron passage. From our search for EEVs in the Optical Gravitational Lensing Experiment (OGLE) project database, we have identified 991 candidate systems. This discovery has increased the number of cataloged EEVs fivefold [1].

The sample comprises two distinct groups of EEVs, differentiated by the evolutionary status of their primaries [2]. The first group, consisting of approximately 100 systems, features a hot main sequence or a Hertzsprung-gap primary. Conversely, the second group, encompassing roughly 900 systems, contains a red giant primary. The orbital periods of these EEVs range from about 3 to 1250 days, with eccentricity values reaching up to 0.8.

The gravitational interactions between components of a binary system may induce tidally excited oscillations (TEOs). These oscillations appear at frequencies exactly equal to integer multiples of the orbital frequency. In our sample of the EEVs, we found 52 systems exhibiting at least a single TEO [2].

Our publications on this topic:
[1] Marcin Wrona et al. 2022; The OGLE Collection of Variable Stars: One Thousand Heartbeat Stars in the Galactic Bulge and Magellanic Clouds, ApJS, 259, 16;
[2] Marcin Wrona et al. 2022; Photometric Analysis of the OGLE Heartbeat Stars; ApJ, 928, 135;