6–10 Jul 2026
University of the Western Cape
Africa/Johannesburg timezone
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ANALYSING VARIABILITY IN BLUEBERRY GALAXIES IN SEARCH OF AGN ACTIVITY

8 Jul 2026, 16:20
1h 20m
Great Hall ( University of the Western Cape)

Great Hall

University of the Western Cape

Poster Presentation Track D - Astrophysics & Space Science Poster Session 2

Speaker

Unathi Tshabalala

Description

Blueberry galaxies are a class of low-mass, low-metallicity, and extremely compact starbursts, considered local analogues to high-redshift star-forming galaxies. This study investigates the hypothesis that a subset of these systems hosts Active Galactic Nuclei (AGN). Photometric light curves for an initial sample of 20 Blueberry galaxies were extracted from Asteroid Terrestrial-impact Last Alert System ATLAS, with 17 sources retained after quality and error filtering, and analysed using a Python script. AGN candidates were identified based on two principal criteria: low-level stochastic variability and achromatic behaviour across optical bands, indicative of accretion disk instabilities. The analysis reveals that the majority of galaxies in the final sample exhibit low-amplitude variability within the 0–0.5 magnitude range, consistent with low-luminosity AGN activity. Additionally, several galaxies display coherent, long-term variability that can be modelled by a single Fourier series across both c- and o-bands, under the assumption of achromatic behaviour, suggesting the presence of a centralised energy source. However, no individual galaxy satisfies all selection criteria sufficiently to be definitively classified as an AGN. Despite this, the prevalence of AGN-like variability signatures across the sample suggests that weak or obscured nuclear activity may be common in Blueberry galaxies. These results warrant further multi-wavelength observations for definitive confirmation.

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