Multiple outflows and delayed ejections revealed by early imaging of novae

Area of Science:

• Astronomy and Astrophysics
• Stellar Evolution
• High-Energy Astrophysics

Background:

• Novae are thermonuclear explosions on accreting white dwarfs in binary systems.
• The precise mechanism of mass ejection during novae remains uncertain, with possibilities including impulsive ejection, multiple outflows, or common-envelope interactions.
• Gigaelectronvolt gamma-ray detections indicate novae are crucial for studying shock physics and particle acceleration.

Purpose of the Study:

• To investigate the mass ejection mechanisms in gamma-ray-detected novae.
• To provide direct observational evidence of the processes driving envelope expulsion from accreting white dwarfs.

Main Methods:

• Near-infrared interferometry was employed to image two gamma-ray-detected novae.
• Observations were supported by multiwavelength data.
• High-resolution imaging captured the structure of outflows and ejected material.

Main Results:

• The fast nova V1674 Her exhibited two perpendicular outflows just days after discovery, likely responsible for gamma-ray emission.
• The slow nova V1405 Cas showed evidence of delayed envelope ejection occurring over 50 days post-eruption, involving a common-envelope phase.
• Direct imaging revealed complex and varied mass ejection processes.

Conclusions:

• The mechanisms driving mass ejection from accreting white dwarfs are more complex than previously assumed.
• Novae can exhibit diverse ejection phenomena, including multiple outflows and significantly delayed mass expulsion.
• These findings advance our understanding of stellar explosions and their impact on binary systems.