Neutron stars, born in the fires of supernovae, continue to amaze even nearly a century after they were first predicted. Fritz Zwicky and Walter Baade pointed out their possibility back in the 1930s, and Jocelyn Bell Burnell discovered pulsars — spinning cosmic lighthouses — in 1967. A special class among them are magnetars, boasting magnetic fields quadrillions of times stronger than Earth's: like giant electromagnetic harps, they vibrate in rhythm with their rotation. Yet their infrared "sound" long eluded astronomers, sparking debate: was it an echo of the magnetosphere or heat from matter that fell onto the star in its turbulent past?

The breakthrough came from James Webb (JWST), using high-time-resolution photometry in a 4.08-micron infrared filter. Over 33 minutes of observation, the NIRCam camera caught a faint pulse at 115 mHz — exactly the star's rotation period (8.69 seconds). The signal profile was broad, like a beat on a bass drum, but with a hint of a second harmonic — betraying a complex internal structure of the emitting region. Phase comparison with X-ray data (obtained earlier via spectroscopy and monitoring by NICER/NuSTAR) revealed an almost perfect match: the infrared peak precedes the hard X-ray peak by only 0.06–0.13 in phase. The magnetar seems to perform the same score in two octaves — from soft infrared to harsh X-rays.

Such phase synchrony spells the end for the accretion disk hypothesis, where emission would be reprocessed with delays of a different geometry. What we see is the flawless work of the magnetosphere: relativistic electrons and positrons, accelerated in twisted magnetic fields, produce synchrotron glow. Its key note is set by the formula \( \nu_c = \frac{3}{2}\gamma^2 \frac{e B}{2\pi m_e c} \). For typical Lorentz factors of \(\gamma\) in the hundreds to thousands and a field of \(B \sim 1.3\times 10^{14}\) G, the critical frequency falls squarely in the infrared and hard X-ray bands — explaining the simultaneous "chord" in two parts of the spectrum. The power of this radiation is drawn from the colossal rotational energy, leaking away according to \( L_{\text{spin-down}} = -4\pi^2 I \frac{\dot{P}}{P^3} \), where \(P\) and \(\dot{P}\) are the period and its derivative.

In the future, observations with higher time resolution (below 0.1 s) will allow us to record the full "score" of the pulse, revealing subtle phase shifts between energies and the geometry of the emitting plasma. Long-term monitoring with JWST and the upcoming ELT will link infrared variability to X-ray outbursts, while theorists will gain constraints on models of coherent curvature radiation. Ultimately, magnetars are becoming laboratories for testing physics in extreme fields, where quantum effects intertwine with gravity — and we are only beginning to hear their true voice. Perhaps it is in such rhythmic synchrony that the origin of mysterious fast radio bursts lies hidden.