Kilonovae

Area of Science:

• Astrophysics
• Nuclear Physics
• Gravitational Wave Astronomy

Background:

• Double neutron star (NS-NS) and black hole-neutron star (BH-NS) mergers are key sources for gravitational wave (GW) detectors.
• These mergers produce neutron-rich ejecta essential for rapid neutron capture (r-process) nucleosynthesis, creating heavy elements.
• The radioactive decay of these nuclei powers kilonovae (macronovae), observable electromagnetic counterparts to GW signals.

Purpose of the Study:

• To review the history and physics of kilonovae, establishing the current understanding of their emission properties.
• To explore variations from the canonical kilonova model, including blue emission and precursor UV/blue signals.
• To assess the detectability of kilonovae in conjunction with future GW detections of compact binary mergers.

Main Methods:

• Review of existing literature on kilonova physics and observational history.
• Utilizing a simple light curve model to illustrate fundamental kilonova physics.
• Analysis of potential variations in kilonova emission based on ejecta composition and central engine activity.

Main Results:

• The established paradigm describes week-long kilonova emission peaking in the near-infrared.
• Potential variations include day-long optical emission from lanthanide-free ejecta and hour-long UV/blue precursor emission.
• Enhanced emission can occur due to energy input from central engines like accreting black holes or magnetars.

Conclusions:

• Kilonovae are crucial electromagnetic counterparts to GW events from compact binary mergers.
• They serve as direct probes of the r-process nucleosynthesis site, vital for understanding heavy element origins.
• Future GW detections will be complemented by kilonova observations, enhancing our understanding of these energetic events.