7 November 2002
Neutron stars: act normal
The high resolution achieved by space observatories such as XMM-Newton are enabling astrophysicists to search for spectral features at the surfaces of neutron stars. A redshift measurement would directly constrain the mass-to-radius ratio of a neutron star, which would in turn reveal much about the matter that these stars are made of. Using data from the Reflection Grating Spectrometer on board XMM-Newton, Cottam et al. obtain spectroscopic evidence for redshifted iron and oxygen absorption features in the spectrum of frequent X-ray bursts on the surface of the neutron star in the compact binary EXO 07481–676. This points to relatively 'normal' nuclear matter as stuff of neutron stars, and excludes some models that predict the presence of more exotic matter.
Gravitationally redshifted absorption lines
in the X-ray burst spectra of a neutron star
J. COTTAM, F. PAERELS & M. MENDEZ
Nature 420, 51–54 (2002); doi:10.1038/nature01159
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Astronomy: Twinkle, twinkle, neutron star
COLE MILLER
Neutron stars, as the name suggests, are mostly made of neutrons. But
the cores of these tiny, dense stellar leftovers might conceal new states
of matter, including strange matter. The light from these stars holds
the key.
Nature 420, 31–33 (2002); doi:10.1038/420031a
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