News Excerpt:
Recently, AstroSat has detected bright sub-second X-ray bursts from a new and unique neutron star with an ultrahigh magnetic field (magnetar).
- It can help understand the intriguing extreme astrophysical conditions of magnetars.
About Magnetars:
- Magnetars are neutron stars with an ultrahigh magnetic field that are much stronger than the terrestrial magnetic field.
- The magnetic field of a magnetar is over one quadrillion times stronger than Earth’s magnetic field.
- Besides, magnetars display strong temporal variability, typically including a slow rotation, a rapid spin-down, bright but short bursts going on up to months-long outbursts.
- One such magnetar, called SGR J1830-0645, was discovered in October 2020 by NASA's Swift spacecraft.
- It is relatively young (about 24,000 years) and an isolated neutron star.
- X-ray bursts occur in low-mass X-ray binary systems where a neutron star and low-mass main sequence star are in orbit around one another.
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AstroSat:
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Key findings:
- Scientists from the Raman Research Institute (RRI) and the University of Delhi performed the timing and spectral analysis of SGR J1830−0645 magnetar using two instruments onboard AstroSat- the LAXPC and SXT.
- It detected 67 short sub-second X-ray bursts, with an average duration of 33 milliseconds.
- Of these bursts, the brightest one lasted for about 90 milliseconds.
- According to the Monthly Notices of the Royal Astronomical Society, SGR J1830–0645 is a unique magnetar that showcases emission lines in its spectra.
- The presence of emission lines and its potential origin remains a subject of consideration.
- The energy-dependence in SGR J1830-0645 differed from what was observed in several other magnetars.
- There were two thermal blackbody emission components originating from the neutron star's surface (radius of 0.65 and 2.45 km).
- Thus, this research contributes to our understanding of magnetars and their extreme astrophysical conditions.
- The pulsed component of the overall X-ray emission showed significant variation with energy.
- It increased for energies up to about 5 kiloelectron Volt (keV) and showed a steep drop thereafter.
- This trend is different from that observed in several other magnetars.
