Astronomy Tea Talk

Talk title: Sleeping Giants: Telling Case Studies of Changing-look Quasars

Abstract 1: 

Changing-look quasars (CLQs) exhibit dramatic variability in their continuum strengths and broad emission-line fluxes on short timescales. This behavior is challenging to many models of the quasar accretion flow and the broad-line region, due in large part to the short transition times between high and low states. To investigate the cause of the observed transitions, in this talk I will present contemporaneous Hubble UV spectra and ground-based optical spectra of previously known turn-off CLQs. I will discuss the changing optical-UV spectral energy distributions of a few case studies before and after transition with an eye to predictions for quasars based on X-ray binary outbursts, which suggest that the mechanism for the change is likely a changing accretion flow structure. I will also discuss a few cases of CLQs that underwent multiple state changes, and what we can learn from both their SEDs and the timescale of the transitions, and the durations of the low and high states.

Title: Creating Space-Based, All-Sky Surveys to Study the Death and Afterlife of Stars

Abstract 2:

The next decade of time-domain astronomy will be defined by our ability to observe the sky continuously, precisely, and across multiple wavelengths. Existing surveys continue to transform our understanding of the transient Universe. Yet, entire classes of events—both known and unknown—remain largely undetected, including the vast population of isolated stellar-mass black holes and neutron stars predicted to exist in the Milky Way. Revealing these remnants requires new survey architectures capable of continuous all-sky coverage, multi-wavelength observations, uninterrupted temporal sampling, and the photometric stability achievable only from space.

In this talk, I will outline a path toward this next generation of survey missions. I will begin by showing how a space-based, all-sky optical survey—exemplified by the CuRIOS mission and its technology demonstrator CuRIOS-ED—can detect the faint, long-duration microlensing signals that trace isolated compact objects in the Milky Way. I will then show how small, scalable gamma-ray monitors such as the BTO instrument on the NASA-funded COSI satellite can further our understanding of compact object formation by capturing the high-energy signatures associated with their birth in supernovae and merger events. These upcoming space-based surveys open discovery spaces inaccessible to current facilities and offer a more complete view of compact objects across their full evolutionary arc, from their formation to their long-lived isolated phases.