Wynn Jacobson-Galan wrote:
Almost a decade ago, amongst the heap of exotic transients observed every day in our Universe, a new class of stellar explosion was identified and labeled Type Iax supernovae (
SNe Iax). Similar to the infamous Type Ia supernovae (
SNe Ia) that are commonly used to measure the
expansion rate of the universe, SNe Iax are also thought to arise from the destruction of a white dwarf star as it approaches the
Chandrasekhar mass limit. However, these supernovae are physically distinct explosions from SNe Ia given their low observed luminosities and kinetic energies, combined with the slow velocities at which the obliterated white dwarf blasts through interstellar space i.e., the ejecta velocity.
After their identification, theorists were tasked with explaining how the destruction of a white dwarf could produce such a “weak” explosion rather than the typical characteristics seen in SNe Ia. Many now agree that in order to create a SN Iax, the white dwarf needs to explode via a
deflagration rather than a
detonation: the
shock wave that initially ripples through the white dwarf will travel sub-sonically instead of super-sonically. As the weakened shock wave attempts to explode the white dwarf, it will not be strong enough to overcome the pull of gravity and completely unbind the star. Instead, only some of the white dwarf’s stellar structure will be released in the explosion to produce a SN Iax, leaving behind a remnant stellar core. And thus, a
zombie star is born!
Of the ~100 SNe Iax known presently, all have occurred in galaxies far from the Milky Way. However, for every 10 SN Ia identified, which make up ~20% of all explosions in the universe, 2-5 SNe Iax are also discovered, making them relatively common explosions. Nevertheless, none of the remnant supernovae that exploded in the Milky Way in the past have been identified as a SN Iax despite the identification of many SNe Ia remnants, as well as those from the collapse of massive stars. And so, since the inception of the SN Iax class, a pressing question has eluded astronomers: where are all the
galactic Type Iax supernova remnants?
The authors of today’s paper attempt to answer this burning question by offering up what may be the first confirmed SN Iax remnant in the Milky Way. Using archival data from the
Chandra X-ray Observatory, the authors study the X-ray emission from supernova remnant Sgr A East (i.e., G0.0+0.0, shown in
Figure 1) that is thought to have exploded at least 2000 years ago near the galactic center. Even after thousands of years, shock waves within the synthesized supernova material will continue to accelerate subatomic particles, which in turn created prominent X-ray emission that can be observed in supernova remnants throughout our own galaxy. Consequently, the strength of this X-ray emission from different elements in the remnant is directly linked to the type of explosion that may have produced the G0.0+0.0 remnant. ...
