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26th December 2023 (10 Topics)

Milli-second burst detected by AstroSat


AstroSat, India's first multi-wavelength space-based observatory, has made a groundbreaking discovery, detecting bright sub-second X-ray bursts from a novel neutron star with an ultrahigh magnetic field, known as a magnetar.

Magnetars are neutron stars characterized by ultrahigh magnetic fields, surpassing Earth's magnetic field by over one quadrillion times. These extreme astrophysical objects emit high-energy electromagnetic radiation due to the decay of their magnetic fields.

Key Characteristics:

  • Strong temporal variability, including slow rotation and rapid spin-down.
  • Display of bright but short bursts, extending to months-long outbursts.

SGR J1830-0645 - A Unique Magnetar

Discovery and Background:

  • SGR J1830-0645 was discovered in October 2020 by NASA's Swift spacecraft.
  • Relatively young, around 24,000 years old.
  • Isolated neutron star.

Motivation for Study: Scientists from the Raman Research Institute (RRI) and the University of Delhi aimed to study and explore the characteristics of SGR J1830-0645 using AstroSat's instruments.

Scientific Analysis with AstroSat

Instruments Used: The study utilized two instruments onboard AstroSat: the Large Area X-Ray Proportional Counter (LAXPC) and the Soft X-Ray telescope (SXT).

Key Findings:

  • Detection of 67 short sub-second X-ray bursts.
  • Average duration of bursts: 33 milliseconds.
  • Brightest burst lasted approximately 90 milliseconds.
  • Published Study:
  • The research, published by the Royal Astronomical Society, highlights SGR J1830–0645 as a unique magnetar exhibiting emission lines in its spectra.


Unraveling the Mysteries

Emission Lines and Their Origins:

  • The study noted the presence of emission lines in the spectra of SGR J1830-0645.
  • Potential origins include fluorescence of iron, proton cyclotron line feature, or instrumental effects.

Energy-Dependence Findings:

  • Different energy-dependence observed compared to other magnetars.
  • Two thermal blackbody emission components with distinct radii (0.65 and 2.45 km) observed on the neutron star's surface.

Future Research Aims

Varied X-ray Emission Behavior:

  • The pulsed component of the overall X-ray emission showed significant variation with energy, increasing up to 5 kiloelectron Volt (keV) and exhibiting a steep drop thereafter.

Next Steps: The research team plans to expand their study to understand the origin of highly energetic emissions and determine whether they have an astrophysical or instrumental nature.

Way Forward: The research contributes to advancing our understanding of magnetars and the extreme astrophysical conditions they exhibit, opening avenues for further exploration and discovery.Top of Form

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