CaltechAUTHORS
Published October 1, 2014 | Version Submitted + Published
Journal Article Open

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

Creators

Abstract

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_1 ~ 42 eV) with a broken power law (Γ_1 ~ 2.0, Γ_2 ~ 1.4 and E_(break) ~ 3.4 keV) and (2) two blackbody components (kT_1 ~ 44 eV and kT_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.

Additional Information

© 2014 American Astronomical Society. Received 2014 April 21; accepted 2014 July 24; published 2014 September 10. This work was supported under NASA Contract No. NNG08FD60C, and made use of data from the NuSTAR mission, 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 has 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). E.V.G. acknowledges support from NASA/Fermi grant NNX12AO89G and NASA/Chandra grant G03-14066X. V.M.K. acknowledges support from an NSERC Discovery Grant, the FQRNT Centre de Recherche Astrophysique du Quebec, an R. Howard Webster Foundation Fellowship from the Canadian Institute for Advanced Research (CIFAR), the Canada Research Chairs Program, and the Lorne Trottier Chair in Astrophysics and Cosmology. A.M.B. acknowledges the support by NASA grants NNX10AI72G and NNX13AI34G.

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Published - 0004-637X_793_2_88.pdf

Submitted - 1408.1644v1.pdf

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Additional details

Identifiers

Eprint ID
50429
Resolver ID
CaltechAUTHORS:20141016-074136515

Related works

Describes
http://arxiv.org/abs/1408.1644 (URL)

Funding

NASA
NNG08FD60C
NASA
NNX12AO89G
NASA
G03-14066X
Natural Sciences and Engineering Research Council of Canada (NSERC)
Fonds de recherche du Québec – Nature et technologies (FRQNT)
Canadian Institute for Advanced Research (CIFAR)
Canada Research Chairs Program
Lorne Trottier Chair in Astrophysics and Cosmology
NASA
NNX10AI72G
NASA
NNX13AI34G

Dates

Created
2014-10-16
Created from EPrint's datestamp field
Updated
2021-11-10
Created from EPrint's last_modified field

Caltech Custom Metadata

Caltech groups
NuSTAR, Space Radiation Laboratory
Other Numbering System Name
Space Radiation Laboratory
Other Numbering System Identifier
2014-31