Core Collapse Supernovae (CCSNe)

The cores of massive stars (M$>$8 M$_\odot$) burn progressively heavier elements until reaching iron, at which point they experience core-collapse and explode as supernovae.

The violent explosions of these massive stars provide the necessary gas and perturbations to impact the next generation of stars and disperse the chemical elements necessary for life. Further, core-collapse supernovae (CCSNe) expel nuclear-processed materials which enrich the interstellar medium and drive galaxy evolution, making them vital to our understanding of the Universe’s past, present, and future. Both stellar and galactic evolutionary models rely on a precise understanding of the incredibly diverse population of CCSNe. This diversity is the result of differences in progenitor nature and environment, such as stellar mass, binarity, and the amount of residual stellar envelope at explosion. The effects of these differences can be understood by modeling the final stages of massive stars lives, the explosion, and the evolution of the supernovae. Proper testing of these theorical predictions requires observations of nearby supernovae within hours of explosion, when they provide clues about their progenitors and explosion processes. Nearby CCSNe offer the ideal testbed for studying the processes which shape the Universe.

Tidal Disruption Events

Tidal Disruption Events (TDEs) are rare cosmic phenomena where a star strays too close to a supermassive black hole, resulting in its gravitational forces tearing the star apart.

This cataclysmic event leads to the emission of powerful electromagnetic radiation across various wavelengths, making TDEs intriguing subjects of study in black hole accretion and outflow physics. TDEs also provide a direct pathway for studying the launch of relativistic jets, and other non-relativistic outflows. As these outflows propagate into the surrounding medium, we can gain unique insight into the environment of previously dormant SMBHs. Many dedicated researchers at the University of Arizona are at the forefront of unraveling the mysteries surrounding, contributing valuable insights into the fundamental processes governing the interaction between supermassive black holes and their surrounding stellar environments.

Type Ia Supernovae (SNe Ia)

Type Ia supernovae (SNe Ia) are the thermonuclear explosions of carbon-oxygen white dwarfs.

However, there are significant questions about their progenitors and explosion mechanisms. Are the progenitors of SNe Ia double white dwarf (double-degenerate) systems or white dwarf and non-degenerate star (single-degenerate) systems? How massive is the white dwarf at the time of explosion? How does the explosion propagate through the star? Does it begin on the surface and cause a chain reaction in the center, does it begin in the center following a reduction in the central density, or is it something else entirely? Studying the youngest and nearest SNe Ia can help us answer these questions. Further, since SNe Ia are standardizable candles which can be used to measure distances in the universe understanding the diversity of SNe Ia is crucial for cosmology and may help resolve the Hubble tension.

Gamma Ray Bursts (GRB)

Gamma-ray bursts are one of the most energetic explosions in the Universe happening at cosmological distances.

These explosions produce neutron stars and black holes which play a central role in the generation of gravitational waves and related electromagnetic waves, a crucial element of multi-messenger astronomy. However, we have limited knowledge of massive stellar evolution and the production of heavy elements. Uncertainties include the mass-loss rates of massive stars prior to the explosion and the fraction of heavy elements produced in binary neutron star mergers. At the University of Arizona, we make use of various observational facilities to follow up gamma-ray bursts and look for associated supernovae or kilonovae. Supernovae associated with gamma-ray burst sheds light on their progenitor system whereas the detection of kilonova will shed light on the production mechanism of heavy r-process elements in the Universe.

SAGUARO

Searches After Gravitational waves Using ARizona Observatories

SAGUARO is an exciting multi-messenger collaboration comprised of researchers at the University of Arizona and Northwestern University. Formed in 2019, we utilize the Catalina Sky Survey Telescope to search for optical counterparts to gravitational wave (GW)-detected mergers. During the third GW observing run, SAGUARO conducted follow-up of 17 compact binary mergers, including those of binary neutron stars (BNS), neutron star–black holes (NSBH), and black hole–mass gap objects.

Science