PTFs

PTF stands for Palomar Transient Factory, a time-domain sky survey conducted from 2009 to 2012 at Palomar Observatory in California. It used the 48-inch Samuel Oschin Telescope equipped with a wide-field mosaic camera to repeatedly image large swaths of the sky in search of transient events. The project emphasized automated image processing and real-time candidate identification, with alert streams shared to the broader astronomical community.

The survey contributed significantly to the discovery and study of transient phenomena, including various types of supernovae, tidal disruption events, variable stars, and active galactic nuclei variability. By providing rapid follow-up opportunities and a growing catalog of transients, PTF aided population studies, rate measurements, and statistical analyses of transient events. It also helped advance pipelines for real-time data processing, candidate vetting, and community-accessible data products.

Following the initial campaign, PTF evolved into the Intermediate Palomar Transient Factory (iPTF) (roughly 2013–2017), which introduced upgrades to instrumentation and data processing to improve cadence and sensitivity. In 2017–2018, operations transitioned to the Zwicky Transient Facility (ZTF), which expanded the field of view and data throughput while continuing the Palomar Observatory program on time-domain astronomy.

Impact and legacy: PTF and its successors established and refined methodologies for rapid transient discovery, data sharing, and collaborative follow-up. The project is regarded as a foundational effort in modern time-domain astronomy, influencing subsequent surveys and the development of real-time alert systems used by the astronomical community.