NICER Data on Low-Mass Binary (IMAGE)
Caption
During NICER commissioning, an observation of low-mass X-ray binary 4U 1608-522 revealed a serendipitous Type I X-ray burst, a flare resulting from a thermonuclear explosion on the surface of a neutron star. 4U 1608 consists of a neutron star in a close orbit with a low-mass star from which it is drawing gas. As this matter accretes and piles up on the neutron star surface, its density in the strong-gravity environment increases until an explosive nuclear fusion reaction is ignited. The heated neutron star surface and atmosphere glow in X-rays, cooling and dimming over the span of about one minute. The hot-spot on the star swings in and out of NICER's view as the star spins, approximately 619 times each second; these fluctuations in X-ray brightness, and their evolution during the burst, are indicated by the purple contours in the lower panel. NICER provides a unique such bursts, tracing flame propagation and other phenomena through the burst's temperature and brightness changes over time, with simultaneous fast-timing and spectroscopy capability not previously available.
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NASA
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