Participant Support Cost for Collaborative Research: A multi-wavelength observational and theoretical study of the fastest evolving stellar explosions SP0052614

Astronomical transients are at the intersection of several critical areas of modern Astrophysics: as probes of the early Universe, as cosmic distance ladders, as electromagnetic signposts of gravitational waves (GW) and neutrinos, and as factories of compact objects (black holes -BHs- and neutron stars -NSs-) that later merge producing detectable GWs. Recent technological advances have revolutionized the investigative power of optical Astronomical Transient surveys (e.g. PanSTARRS and PTF), which allowed the exploration of uncharted territories of the parameters space, and led to the discovery of new types of transients. Among these, very prominent is the new class of luminous Fast and Blue Optical Transients (FBOTs), which collects explosive transients with supernova-like luminosities and the shortest observed time scales of evolution of a few days. Current and upcoming NSF-funded surveys like the Zwicky Transient Facility (ZTF) and the Large Synoptic Survey Telescope (LSST) will take this effort to the next step regarding timescales, luminosities and rate of discoveries. This proposal capitalizes on this guaranteed stream of data. As we showed in our recent study of the Astronomical Transient AT 2018cow, the large FBOT luminosities –reaching Lpk ⇠ 4 ⇥ 1044 erg s−1– and extremely short rise-times of a few days rule out traditional SN models powered by the radioactive decay of 56Ni, imply small ejecta masses Mej ⇠ 0.1−0.5M$, and point at the presence of a central engine in the form of a newly-born NS or BH powering the transient’s display. Furthermore, by sampling the radio-to-X-ray emission from an FBOT for the first time, we demonstrated that FBOTs provide an unparalleled opportunity to study BHs and NSs at the time of their formation, a phase of evolution that has been hidden to our eyes so far. We build on our recent results and propose here an effort that uniquely combines the strengths of panchromatic observations of FBOTs and a theoretical investigation of the emission from their fastest ejecta informed by Particle-In-Cell simulations, with the immediate goals to (i) shed light on the nature of FBOTs stellar progenitors; (ii) provide critical insight onto the process of formation of compact objects and their properties at the time of birth.