Astrophys. J., 845, 159-159 (2017/August-3)
NuSTAR hard X-ray observations of the energetic millisecond pulsars PSR B1821-24, PSR B1937+21, and PSR J0218+4232.
GOTTHELF E.V. and BOGDANOV S.
Abstract (from CDS):
We present Nuclear Spectroscopic Telescope Array (NuSTAR) hard X-ray timing and spectroscopy of the three exceptionally energetic rotation-powered millisecond pulsars PSRs B1821-24, B1937+21, and J0218+4232. By correcting for the frequency and phase drifts of the NuSTAR onboard clock, we are able to recover the intrinsic hard X-ray pulse profiles of all three pulsars with a resolution down to 15 µs. The substantial reduction of background emission relative to previous broadband X-ray observations allows us to detect for the first time pulsed emission up to ∼50 keV, ∼20 keV, and ∼25 keV for the three pulsars, respectively. We conduct phase-resolved spectroscopy in the 0.5-79 keV range for all three objects, obtaining the best measurements yet of the broadband spectral shape and high-energy pulsed emission to date. We find extensions of the same power-law continua seen at lower energies, with no conclusive evidence for a spectral turnover or break. Extrapolation of the X-ray power-law spectrum to higher energies reveals that a turnover in the 100 keV to 100 MeV range is required to accommodate the high-energy γ-ray emission observed with Fermi-LAT, similar to the spectral energy distribution observed for the Crab pulsar.
© 2017. The American Astronomical Society. All rights reserved.
pulsars: general - pulsars: individual: (PSR B1821-24, PSR B1937+21, PSR J0218+4232) - stars: neutron - X-rays: stars - X-rays: stars
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