I presented my work at EWASS 2018 in the Peculiar Supernovae sessions.
We present the first ever measurement of the volumetric rate of ‘Ca-rich’ optical transients from the Palomar Transient Factory (PTF). PTF was an automated optical sky survey designed for transient discovery that spectroscopically confirmed 1800 supernovae over 2009-2012. With a range of cadence experiments, from 1 to 5 days, providing untargeted scans of the night sky, the PTF dataset is the perfect playground for a supernova rate calculation. Ca-rich transients have absolute magnitudes in the range -15 to -16.5 mag, rise times of 10-15 days, and a fast photospheric and spectroscopic evolution to a Ca-dominated nebular spectrum. Due to their faint-and-fast nature, these objects are notoriously difficult to both discover and spectroscopically identify before they fade away. We use 3 years of PTF data to construct a representative simulation of the survey in which we place Ca-rich explosions. The survey replicates the cadence and observing conditions of PTF’s operation, allowing us to determine whether a simulated object would have been discovered or missed. The results of these simulations are compared to the real survey performance to determine the volumetric rate of Ca-rich SNe, which we find to be 33-96% of the SNe Ia rate at a similar redshift. This value is higher than previous estimates, but compatible with being the missing source of calcium in the intracluster medium (ICM). Furthermore, these explosions are observed at large distances from host galaxies, allowing for efficient pollution of the ICM. Our survey simulations suggest these remote locations are likely to be astrophysically real, rather than an observational bias. The high cadences of future sky surveys, such as ZTF and LSST, will transform our understanding of faint-and-fast transients and further populate this region of the time- domain phase-space.