Populations of R Coronae Borealis stars and other dusty variables revealed by infrared searches

I will present results from the first systematic infrared search for Galactic R Coronae Borealis (RCB) stars using the infrared Palomar Gattini-IR (PGIR) time-domain surveyor. RCB stars are rare, hydrogen-deficient supergiants formed in mergers of He-core and CO-core white dwarfs, characterized by erratic dust-formation episodes that drive large-amplitude brightness variations. Since 2018, PGIR has been surveying the entire northern sky in the J-band at a three-day cadence, producing light curves for over 60 million stars. Mining this dataset has enabled a systematic characterization of the population of Galactic RCB stars, offering new insights into the Galactic He-CO white dwarf merger rate and the population of compact binaries detectable by future gravitational wave missions such as LISA. In addition to RCB stars, I will also present discoveries of other large-amplitude infrared variables from PGIR, including thousands of new pulsating AGB stars, as well as new outbursting young stellar objects and symbiotic binaries, demonstrating the power of infrared surveys in mapping the dustiest stellar populations in our Galaxy. In closing, I will discuss the exciting landscape of upcoming infrared surveys that are poised to uncover the dustiest stellar variables in the Milky Way and nearby galaxies.