NuSTAR Hard X-ray Observations of the Energetic Millisecond Pulsars PSR B1821-24, PSR B1937+21, and PSR J0218+4232
- Creators
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Gotthelf, E. V.
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Bogdanov, S.
Abstract
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.
Additional Information
© 2017 The American Astronomical Society. Received 2017 April 11; revised 2017 July 12; accepted 2017 July 18; published 2017 August 22. We greatly appreciate discussions with M. Bachetti and C. Markwardt concerning NuSTAR clock timing issues, and K. Forster for the necessary assistance in planning the PSR B1821-24 observations. We thank A. Harding for discussions regarding high-energy magnetospheric emission from pulsars. We also thank S. Ransom for supplying the radio ephemeris of PSR B1821-24. This work was supported under NuSTAR Cycle 1 Guest Observer Program grant NNX15AV29G awarded through Columbia University. E.V.G. thanks Josep Maria Paredes for hosting his sabbatical at the University of Barcelona Institut de Ciències del Cosmos (ICCUB) and acknowledges support through the "Programa Estatal de Foment de la Investigaciò Científica i Tècnica d'Excellència, Convocatòria 2014, Unitats d'Excellència Maria de Maeztu." The NuSTAR mission is a project led by the California Institute of Technology, managed by the Jet Propulsion Laboratory, and funded by the National Aeronautics and Space Administration. We thank the NuSTAR Operations, Software, and Calibration teams for support with the execution and analysis of these observations. This research made use of the NuSTAR Data Analysis Software (NuSTARDAS) jointly developed by the ASI Science Data Center (ASDC, Italy) and the California Institute of Technology (USA). The scientific results reported in this article are based in part on data obtained from the Chandra Data Archive. A portion of the results presented are based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA member states and NASA. This research has made use of data and software provided by the High Energy Astrophysics Science Archive Research Center (HEASARC), which is a service of the Astrophysics Science Division at NASA/GSFC and the High Energy Astrophysics Division of the Smithsonian Astrophysical Observatory. We also acknowledge extensive use of arXiv and the NASA Astrophysics Data Service (ADS). Facilities: NuSTAR - The NuSTAR (Nuclear Spectroscopic Telescope Array) mission, CXO, XMM.Attached Files
Accepted Version - 1704.02964.pdf
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Additional details
- Eprint ID
- 76511
- Resolver ID
- CaltechAUTHORS:20170411-111011349
- Created
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2017-04-11Created from EPrint's datestamp field
- Updated
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2021-11-15Created from EPrint's last_modified field
- Caltech groups
- NuSTAR