Kelebogile Bonokwane – SALT and TESS monitoring of central stars of planetary nebulae
Jun 17 @ 11:00 am - 12:00 pm
Thursday 17 June 2021
Kelebogile Bonokwane (SAAO/UCT)
SALT and TESS monitoring of central stars of planetary nebulae
Planetary Nebulae (PNe) are the product of Asymptotic Giant Branch (AGB) evolution. Evolved from Solar-like intermediate mass stars (0.8 — 8 M_sun), they have a hot, radiating core that ionizes the gas of the expelled envelope, producing a glowing nebula. Complex, aspherical morphologies are observed in PNe and binary central stars (CSs) have been the favoured explanation for deviations from spherical symmetry. Finding and characterizing the population of binary CSs is thus important to understand the physics behind their morphologies. The objects of this study are Hen3-1333, Hen2-113 and Hen2-47, all with Wolf- Rayet (WR) CSs that commonly exhibit fast, dense stellar winds. All exhibit multipolarity in their young nebulae, Hen3-1333 has a disk and dual-dust chemistry, while the other two have central stars offset from the geometric centre of their nebulae. Here we develop a quantitative time-series analysis to determine whether these objects have binary CSs and develop constraints to permissible orbital parameters.
The High Resolution Spectrograph (HRS) of the Southern African Large Telescope (SALT) was used to collect echelle spectroscopic data over ~3 years and The Exoplanet Survey Satellite (TESS) was used to obtain photometric data for the objects. Using cross-correlation and Gaussian line fitting, radial velocity (RV) time-series were compared to lightcurves determined from the TESS data. Lomb-Scargle periodograms were used to search for periodic variability in the RV and photometry time-series data. The results were discussed based on short (0 — 10 days), intermediate (10 — 1000 days) and long (1000 — 10000 days) orbital period ranges. The quantitative variability analysis excludes short orbital period binary systems, suggesting that if their multiple features are due to binary interactions, the most likely case is the long orbital period range.