The ASAS-SN Catalog of Variable Stars V: Variables in the Southern Hemisphere

The All-Sky Automated Survey for Supernovae (ASAS-SN) provides long baseline (${sim}4$ yrs) light curves for sources brighter than V$lesssim17$ mag across the whole sky. As part of our effort to characterize the variability of all the stellar sources visible in ASAS-SN, we have produced ${sim}30.1$ million V-band light curves for sources in the southern hemisphere using the APASS DR9 catalog as our input source list. We have systematically searched these sources for variability using a pipeline based on random forest classifiers. We have identified ${sim} 220,000$ variables, including ${sim} 88,300$ new discoveries. In particular, we have discovered ${sim}48,000$ red pulsating variables, ${sim}23,000$ eclipsing binaries, ${sim}2,200$ $delta$-Scuti variables and ${sim}10,200$ rotational variables. The light curves and characteristics of the variables are all available through the ASAS-SN variable stars database (https://asas-sn.osu.edu/variables). The pre-computed ASAS-SN V-band light curves for all the ${sim}30.1$ million sources are available through the ASAS-SN photometry database (https://asas-sn.osu.edu/photometry). This effort will be extended to provide ASAS-SN light curves for sources in the northern hemisphere and for V$lesssim17$ mag sources across the whole sky that are not included in APASS DR9.