خط خفي يكشف عن نجم نيوتروني مغناطيسي سريع

الملخص الأصلي

كما كتبه المؤلفون، بالإنجليزية 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.