Cyclotron lines: from magnetic field strength estimators to geometry tracers in neutron stars

Abstract

With exactly forty years since the discovery of the first cyclotron line in Her X-1, there have been remarkable advancements in the field related to study of the physics of accreting neutron stars -- cyclotron lines have been a major torchbearer in this regard, from being the only direct estimator of the magnetic field strength, a tracer of accretion geometry and an indicator of the emission beam in these systems. The main flurry of activities have centred around studying the harmonic separations, luminosity dependence, pulse phase dependence and more recently the shapes of the line and the trend for long term evolution in the line energy. This article visits the important results related to cyclotron lines since its discovery and reviews their significance. An emphasis is laid on pulse phase resolved spectroscopy and the important clues a joint timing and spectral study in this context can provide, to build a complete picture for the physics of accretion and hence X-ray emission in accreting neutron stars.

Has appeared in Journal of Astrophysics and Astronomy special issue on 'Physics of Neutron Stars and related objects', celebrating the 75th birth-year of G. Srinivasan

References in corpus (14)

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Cited by in corpus (12)

• Long-term evolutions of the cyclotron line energies in Her X-1, Vela X-1 and Cen X-3 as observed with Swift/BAT
• Probing the Cyclotron line characteristics of 4U 1538-522 using AstroSat-LAXPC
• Evolution of timing and spectral characteristics of 4U 1901+03 during its 2019 outburst using the Swift and NuSTAR observatories
• A high-mass X-ray binary pulsar 4U 1907+09 with multiple absorption-line features in the spectrum
• Evolution implications of neutron star magnetic fields: inferred from pulsars and cyclotron lines of HMXBs
• Broadband study and the discovery of pulsations from the Be/X-ray binary eRASSU J052914.9-662446 in the Large Magellanic Cloud
• Phase dependent evolution within large luminosity range of 1A 0535+262 observed by Insight-HXMT during 2020 giant outburst
• Broadband study of the Be X-ray binary RX J0520.5-6932 during its outburst in 2024
• LAXPC instrument onboard AstroSat: Five exciting years of new scientific results specially on X-ray Binaries
• Clumpy wind studies and the non-detection of cyclotron line in OAO 1657-415
• Super-critical accretion of BeXRB SXP 15.3
• Studies of Cepheus X-4 during 2018 outburst observed with AstroSat