In the galaxy NGC 3583, telescopes noticed a strange X-ray source: it flares up and then almost fades away. Breaking its light into a spectrum (a rainbow of energies), astronomers found a narrow dark dip — like a single note plucked from a chord.
This 'note' is created by protons trapped in a monstrous magnetic field. Like a string pressed on a fret, they vibrate at exactly one frequency. The pitch of the note revealed: the field is 400 trillion times stronger than Earth's. Before us is a neutron star with record magnetism — a magnetar.
A field of this strength not only tears atoms apart, stretching them into needles, but also turns the surrounding void into something like crystal, bending light rays.
as written by the authors arXiv:2606.08598
We present a broadband X-ray study of the transient hyperluminous X-ray source (HLX), 2SXPS J111416.1+481833, in the galaxy NGC 3583, using archival XMM-Newton, NuSTAR, Chandra data, and long-term Swift/XRT monitoring. The source episodically enters the hyperluminous regime with X-ray luminosities $$L_X > 10^{41}$$ erg s$$^{-1}$$ and drops by a factor of $$>45$$ from its peak into a deep low state. We detect a clear spectral cutoff at $$\sim$$5-6 keV in the broadband spectra, which are well modeled by a soft thermal component combined with optically thick thermal Comptonization or an inner advection-dominated disk. In the XMM-Newton spectra, we detect a statistically significant ($$\gtrsim 3.9 \sigma$$) absorption line centered at $$E_{\rm line} \approx 1.97 \pm 0.04$$ keV with a width of $$\sigma_{\rm line} \approx 74 \pm 40$$ eV. We primarily interpret the line as a candidate proton Cyclotron Resonance Scattering Feature (CRSF), implying a local magnetic field strength of $$B \sim 4 \times 10^{14}$$ G. Alternative interpretations, such as an origin in an ionized outflow, were explored and found to be less likely. We do not detect coherent X-ray pulsations, placing 90% confidence upper limits on the pulsed fraction of 19.3% in the 0.3-10 keV band and 36.3% in the 3-15 keV band. The combination of extreme luminosity, a hard spectral state, and the detection of a candidate cyclotron line provides strong evidence for a highly magnetized neutron star accretor.
A chunk of neutron star the size of a grain of sand weighs more than an aircraft carrier.