SkyMapper optical follow-up of gravitational wave triggers: Alert science data pipeline and LIGO/Virgo O3 run. (19th May 2021)

• Record Type: Journal Article
• Authors: Chang, Seo-Won; Onken, Christopher A.; Wolf, Christian; Luvaul, Lance; Möller, Anais; Scalzo, Richard; Schmidt, Brian P.; Scott, Susan M.; Sura, Nikunj; Yuan, Fang
• Is Part Of: Publications of the Astronomical Society of Australia. Volume 38(2021)
• Publication Date: 2021-05-19
• Subjects: methods: data analysis, -- methods: statistical, -- transient detection, -- gravitational waves, -- neutron stars; Astronomy -- Periodicals; Southern sky (Astronomy) -- Periodicals; Astrophysics -- Periodicals; Periodicals; 520.5
• DOI: 10.1017/pasa.2021.17
• Languages: English
• ISSNs: 1323-3580

Abstract

Abstract: We present an overview of the SkyMapper optical follow-up programme for gravitational-wave event triggers from the LIGO/Virgo observatories, which aims at identifying early GW170817-like kilonovae out to $\sim200\, \mathrm{Mpc}$ distance. We describe our robotic facility for rapid transient follow-up, which can target most of the sky at $\delta<+10\deg $ to a depth of $i_\mathrm{AB}\approx 20\, \mathrm{mag}$ . We have implemented a new software pipeline to receive LIGO/Virgo alerts, schedule observations and examine the incoming real-time data stream for transient candidates. We adopt a real-bogus classifier using ensemble-based machine learning techniques, attaining high completeness ( $\sim98\%$ ) and purity ( $\sim91\%$ ) over our whole magnitude range. Applying further filtering to remove common image artefacts and known sources of transients, such as asteroids and variable stars, reduces the number of candidates by a factor of more than 10. We demonstrate the system performance with data obtained for GW190425, a binary neutron star merger detected during the LIGO/Virgo O3 observing campaign. In time for the LIGO/Virgo O4 run, we will have deeper reference images allowing transient detection to $i_\mathrm{AB}\approx 21\, \mathrm{mag}$ .