Supernovae surveys: from the ground up

Abstract

Rapid cadence observations are key in developing a stronger understanding of transient astronomical events. With these observations, we stand to better understand the progenitor systems that result in supernovae, kilonovae, gravitational waves, and gamma-ray bursts. These cataclysmic events reveal key signatures in their earliest stages that need to be understood to properly reduce systematic errors with their use in modern cosmology. Modern surveys (e.g. LSST, ASAS-SN, and ZTF) provide extensive discovery pipelines that allow rapid follow-up of these events, and can provide daily discovery reports, however they are still unable to probe the physics that develops on timescales less than a day.

The first chapter of this thesis, we explore the viability of Siding Spring Observatory as an observing site for followup of LSST's upcoming discovery pipeline. Extensive weather data collected from various sources at the observatory have been analyzed to identify long-term trends in wind, humidity, temperatures, and observing conditions. While strong gusts reaching speeds exceeding 55 meters per second can occasionally occur near the mountain's summit, the majority of the mountain does not experience such high winds, and hence is unlikely to force dome closures. Cloud cover poses a challenge for astronomical observations, with approximately 46% of nights experiencing some cloud. Despite the relatively poor observing conditions for an astronomical site, SSO can still play an important role in transient follow-up, as it can observe a similar sky to LSST due to its latitude, and its longitude is unique enabling observations at times when no other observing sites can.

This analysis is then followed by a discovery paper highlighting the importance of rapid cadence observations of supernovae. SN2019com was discovered on March 31, 2019, with the last non-detection images taken on March 28, 2019. Multiple spectra obtained using the WiFeS instrument on the ANU 2.3m telescope revealed strong similarities to SN2009ip, the first recorded supernova imposter. Early photometry from the Las Campanas SWOPE telescopes indicated an early blue excess, consistent with a shock cooling event. Analysis of this excess provided measurements of SN2019com's progenitor radius, ejecta mass, and ejecta velocity. Subsequent observations with the Hubble Space Telescope (HST) displayed a light source consistent with SN2019com's location, providing further evidence of its similarity to SN2009ip. This kind of analysis was only possible due to a rapid transient follow-up pipeline developed through this thesis, and shows the importance of early observations in determining progenitor systems of peculiar supernovae.

Finally, work done towards developing a low-cost solution to getting UV observations of these high-energy events. The ozone layer exhibits a complex spectral absorption profile in the near-ultraviolet wavelengths, influenced by seasonal variations in solar intensity and atmospheric circulation. Overcoming this obstacle is crucial for achieving a usable signal-to-noise ratio in scientific observations. GLUV is an affordable and long-duration high-altitude balloon experiment designed to deploy a network of NUV telescopes at altitudes between 20-30 km. The GLUV Pathfinder, a spectrometer-based system, serves as a precursor to the final GLUV project, aiming to characterize the NUV sky background as a function of altitude, latitude, and seasonal phase.