Collaborative Research: A Multi-Wavelength Observational and Theoretical Study of the Fastest Evolving Stellar Explosions

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A new class of fast-rising astronomical events with bright X-ray and radio emission was discovered in 2018. Part of the class known as Fast and Blue Optical Transients (FBOTs), these events are significantly brighter than a supernova (SN), or exploding star, but brighten within a few days, much faster than the tens of days typical for supernovae. They are believed to be powered by a newly-born black hole (BH) or neutron star (NS), which is a very compact type of star. A research team between Northwestern University and the University of Chicago will study these FBOTs with a combination of telescope observations and theoretical investigations. The researchers expect to observe about five FBOTs per year from NSF-funded astronomical survey telescopes such as the Zwicky Transient Facility, enabling them to understand what kind of stars become FBOTs and how compact objects like neutron stars and black holes are formed. The investigators will integrate their research with three educational programs: (i) providing summer research opportunities to under-represented minority and women undergraduates; (ii) work with Chicago-area high school teachers to develop curricular material on stellar explosions for their classes; and (iii) work with visually impaired scientists and professional musicians to translate astronomical measurements into sound. 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 parameter space, and led to the discovery of new types of transients. As the research team showed in their recent study of the Astronomical Transient AT 2018cow, the large FBOT luminosities -- reaching peak luminosities of ~4 X 10^44 erg/s -- 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 of 0.1 to 0.5 solar masses, and point at the presence of a central engine in the form of a newly-born NS or BH powering the transient's display. The radio-to-X-ray emission from an FBOT provides 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. The research program uniquely combines the strengths of panchromatic observations of FBOTs and a theoretical investigation of the non-thermal properties of the transients informed by ab-initio 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.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.