A neutron star, once dormant, has awakened with a powerful roar, captivating astronomers worldwide. This phenomenon, triggered by the gravitational pull of a compact object, has unveiled a fascinating mystery.
When gas is drawn towards these cosmic giants, an incredible display of electromagnetic waves occurs. Recent observations have revealed objects with extraordinary X-ray luminosities, leading scientists to explore the concept of supercritical accretion. However, the precise mechanism behind this process remains shrouded in mystery.
The research team focused their attention on NGC 7793 P13, a neutron star located in the NGC 7793 galaxy, approximately 10 million light-years from Earth. As gas falls onto this star, it forms an accretion column, a structure believed to emit intense X-rays. The rotation of the neutron star produces coherent X-ray pulsations, providing valuable insights.
Previous studies indicated that P13 rotates with a period of 0.4 seconds and a constant acceleration rate. Interestingly, its luminosity underwent a dramatic change, increasing by more than two orders of magnitude over a decade. Both rotation velocity and luminosity are crucial parameters in estimating the gas accretion rate, yet their relationship remained elusive for P13.
The research team analyzed archival data from XMM-Newton, Chandra, NuSTAR, and NICER, spanning from 2011 to 2024. They discovered that P13 entered a faint phase in 2021 but began to brighten again in 2022, reaching an exceptionally high luminosity by 2024. During this rebrightening phase, the acceleration rate of the rotation velocity doubled and remained consistent until 2024. This finding suggests a correlation between X-ray luminosity and rotation velocity, indicating a change in the accretion system during the faint phase.
The team further examined the pulsation, conducting detailed analyses. Their results suggested that the height of the accretion column varied with the 10-year flux modulation. These findings offer valuable clues to unravel the enigma of supercritical accretion.
But here's where it gets intriguing: the relationship between X-ray luminosity and rotation velocity, and how it changed during the faint phase, is a topic of debate among astronomers. What do you think? Could this be a key to understanding the mysterious supercritical accretion process? Share your thoughts and let's spark a discussion!
