Probing the progenitors of peculiar thermonuclear supernovae using early-time observations

02es-like Ia supernovae (SNe) show normal width light curves but are generally sub-luminous, whereas 03fg-like SNe Ia tend to be over-luminous. Photometric and spectroscopic distinctions notwithstanding, recently discovered SNe within both these rare subclasses have shown pronounced 'early excess' features in their light curve. The prevalence of this feature within Ia-02es and Ia-03fg suggests it could be generic and that CSM interaction may best explain this feature, thereby indicating a common origin for these peculiar Ia subclasses. The CSM could originate within a double-degenerate scenario involving a white dwarf merger. Another intriguing characteristic common to Ia-02es and Ia-03fg is the presence of narrow [OI] emission in nebular spectra of some members in both subclasses, also favouring a white dwarf merger scenario. I will present early-time photometry for a sample (~6) of recent Ia-02es and Ia-03fg events from ATLAS, Pan-STARRS and ZTF. In the case of SN 2022vqz, multi-colour photometry from thett aforementioned surveys provides strong constraints on the plausible powering mechanism for the early excess (eg. ejecta-companion interaction, CSM interaction, surface nickel or He shell detonation). We model the early excess feature for the SNe in our sample to constrain basic parameters for the CSM shell, such as mass and radial extent. I will discuss open questions surrounding the observed diversity within these subclasses and the nature of their progenitors.