A broadband X-ray study of the Geminga pulsar with NuSTAR And XMM-Newton

Journal Article · Wed Oct 01 04:00:00 EDT 2014 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/793/2/88· OSTI ID:22370582

Mori, Kaya; Gotthelf, Eric V.; Halpern, Jules P.; Beloborodov, Andrei M.; Hailey, Charles J. ^[1]; Dufour, Francois; Kaspi, Victoria M.; An, Hongjun ^[2]; Bachetti, Matteo ^[3]; Boggs, Steven E.; Craig, William W. ^[4]; Christensen, Finn E. ^[5]; Harrison, Fiona A. ^[6]; Kouveliotou, Chryssa ^[7]; Pivovaroff, Michael J. ^[8]; Stern, Daniel ^[9]

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1. Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States)
2. Department of Physics, McGill University, Montreal, QC H3A2T8 (Canada)
3. Université de Toulouse, UPS-OMP, IRAP, Toulouse (France)
4. Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States)
5. DTU Space—National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark)
6. Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States)
7. NASA Marshall Space Flight Center, Huntsville, AL 35812 (United States)
8. Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States)
9. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

We report on the first hard X-ray detection of the Geminga pulsar above 10 keV using a 150 ks observation with the Nuclear Spectroscopic Telescope Array (NuSTAR) observatory. The double-peaked pulse profile of non-thermal emission seen in the soft X-ray band persists at higher energies. Broadband phase-integrated spectra over the 0.2-20 keV band with NuSTAR and archival XMM-Newton data do not fit to a conventional two-component model of a blackbody plus power law, but instead exhibit spectral hardening above ∼5 keV. We find that two spectral models fit the data well: (1) a blackbody (kT {sub 1} ∼ 42 eV) with a broken power law (Γ{sub 1} ∼ 2.0, Γ{sub 2} ∼ 1.4 and E {sub break} ∼ 3.4 keV) and (2) two blackbody components (kT {sub 1} ∼ 44 eV and kT {sub 2} ∼ 195 eV) with a power-law component (Γ ∼ 1.7). In both cases, the extrapolation of the Rayleigh-Jeans tail of the thermal component is consistent with the UV data, while the non-thermal component overpredicts the near-infrared data, requiring a spectral flattening at E ∼ 0.05-0.5 keV. While strong phase variation of the power-law index is present below ∼5 keV, our phase-resolved spectroscopy with NuSTAR indicates that another hard non-thermal component with Γ ∼ 1.3 emerges above ∼5 keV. The spectral hardening in non-thermal X-ray emission as well as spectral flattening between the optical and X-ray bands argue against the conjecture that a single power law may account for multi-wavelength non-thermal spectra of middle-aged pulsars.

• OSTI ID: 22370582
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 793; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
DETECTION
EMISSION
EV RANGE
EXTRAPOLATION
HARD X RADIATION
KEV RANGE
SOFT X RADIATION
SPECTRAL HARDENING
SPECTROSCOPY
TELESCOPES
WAVELENGTHS