Spitzer Lectures 2023

Raffaella Margutti
Associate Professor of Astronomy
and Physics, UC Berkeley

Colloquium: Tue May 2, 11:00 am-12:00 pm

Mining the transient sky in the new era of Time Domain Multi-Messenger investigations
Astronomical transients are signposts of catastrophic events in space, including the most extreme stellar deaths, stellar tidal disruptions by supermassive black holes, and mergers of compact objects. Thanks to new and improved
observational facilities we can now sample the night sky with unprecedented temporal cadence and sensitivity across the electromagnetic spectrum and beyond. This effort has led to the discovery of new types of astronomical transients, revolutionized our understanding of phenomena that we thought we already knew, and enabled the first insights into the physics of neutron star mergers with gravitational waves and light. In this talk I will review some very recent developments that resulted from our capability to acquire a truly panchromatic view of transient astrophysical phenomena. I will focus on two key areas of ignorance in the field: (i) What are the progenitors of stellar explosions and what happens in the last centuries before death? (ii) What is the nature of the compact objects produced by these explosions and what happens when compact objects merge? The unique combination of Discovery Power (guaranteed by planned transient surveys like LSST, combined with efforts in the realm of artificial intelligence) and Understanding (enabled by multi-messenger observations) is what positions time-domain astrophysics for major advances in the near future.

Lecture 1: Fri May 5, 3:30-4:30

Past and Future of searches for electromagnetic counterparts of GW events
After the landmark neutron-star merger event GW170817, the frontier is now to map the properties of a population of neutron star mergers, find electromagnetic counterparts of NS-BH mergers, and connect the pre-merger to the post-merger properties of these events, as constrained by their gravitational wave emission and electromagnetic radiation. In this talk I will review our past achievements and the exciting prospects enabled by the next generation of gravitational wave detectors. The future is bright and loud.

Lecture 2: Tue May 9, 3:30-4:30

The Fastest Stellar Explosions (are really stellar explosions?)
Fast and Blue Optical Transients (FBOTs) emerged in the past decade as a new class of astronomical transients. With extremely rapid time scales of evolution and luminous emission, FBOTs likely probe the extremes of the explosion parameters and/or stellar progenitor properties, and are hard to reconcile within the traditional supernova models. Alternative scenarios include strong shock interaction with a dense medium, or the presence of a central engine (e.g. BH or magnetar formed by the explosion, or a pre-existent BH).

Lecture 3: Thu May 11, 3:30-4:30

Surprisingly bright radio signals from old supernovae and TDEs: the beauty of an unbiassed view of the radio sky
The VLA Sky Survey (VLASS) has delivered the first deep, unbiased view of the northern radio sky, offering an unprecedented opportunity to perform a systematic and unbiased survey of the late-time radio emission from the tens of thousands of previously reported optical stellar explosions and tens of tidal disruption events. Interestingly, we found evidence for bright radio emission from several stellar explosions and tidal disruption events. In this talk I will review our current knowledge of the late-time radio emission from transients, and I will discuss the prospects for future observations to reveal the underlying physics of these bright displays.