Planetary Nebulae (PNe) are the product of Asymptotic Giant Branch (AGB) evolution. Evolved from Solar-like intermediate mass stars (0.8 – 8M), they have a hot, radiating core that ionizes the gas of the expelled envelope, producing a glowing nebula. The core eventually evolves into a white dwarf (WD), following the WD cooling track. 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 WolfRayet (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. The objects were chosen because most of these features, especially multipolar morphologies, are not well represented amongst PNe with known binary CSs. 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 échelle spectroscopic data over 3 years and The Exoplanet Survey Satellite (TESS) was used to obtain photometric data for the objects. The medium resolution (MR) mode (R ≈ 40000) was chosen and 58, 60, and 35 spectra were collected for Hen3-1333, Hen2-113 and Hen2-47, respectively, with an average S/N of 40 at 4495 Å. The TESS data had continuous sampling (30 min cadence) recorded for an orbit length of 27.4 days. 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 – 103 days) and long (103 – 104 days) orbital period ranges. Compatible scenarios for each range were estimated by combining observational constraints with different parameters expected for assumed companion star types. 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. If the variability observed is due to a companion, rather than pulsations from the CS, the companion masses, 0.10 – 1.36 M for Hen3-1333, 0.043 – 1.27 M for Hen2-113 and 0.077 – 1.36 M for Hen2-47, correspond to main sequence stars and dwarfs.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uct/oai:localhost:11427/33436 |
| Date | 07 July 2021 |
| Creators | Bonokwane, Kelebogile |
| Contributors | Miszalski, B, Mohamed, S, Monageng, I, Manick, R |
| Publisher | Faculty of Science, Department of Astronomy |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Master Thesis, Masters, MSc |
| Format | application/pdf |
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