The Crab pulsar in the 0.75-30 MeV range as seen by CGRO COMPTEL

By L. Kuiper, W. Hermsen, G. Cusumano, R. Diehl, V. Schonfelder, A. Strong, K. Bennett, M. M. Sron, Ifc Cnr, Mpe and 2 more. 2001

199 citations recorded by the source corpus.

We present the time-averaged characteristics of the Crab pulsar in the 0.75{30 MeV energy window using data from the imaging Compton Telescope COMPTEL aboard the Compton Gamma-Ray Observatory (CGRO) collected over its 9 year mission. Exploiting the exceptionally long COMPTEL exposure on the Crab allowed us to derive signicantly improved COMPTEL spectra for the Crab nebula and pulsar emissions, and for the rst time to accurately determine at low-energy -rays the pulse prole as a function of energy. These timing data, showing the well-known main pulse and second pulse at a phase separation of 0:4 with strong bridge emission, are studied together with data obtained at soft/hard X-ray energies from the ROSAT HRI, BeppoSAX LECS, MECS and PDS, at soft -rays from CGRO BATSE and at high-energy -rays from CGRO EGRET in order to obtain a coherent high-energy picture of the Crab pulsar from 0.1 keV up to 10 GeV. The morphology of the pulse prole of the Crab pulsar is continuously changing as a function of energy: the intensities of both the second pulse and the bridge emission increase relative to that of the rst pulse for increasing energies up to 1 MeV. Over the COMPTEL energy range above 1 MeV an abrupt morphology change happens: the rst pulse becomes again dominant over the second pulse and the bridge emission loses signicance such that the pulse prole above 30 MeV is similar to the one observed at optical wavelengths. A pulse-phase-resolved spectral analysis performed in 7 narrow phase slices consistently applied over the 0.1 keV{10 GeV energy interval shows that the pulsed emission can empirically be described with 3 distinct spectral components: i) a power-law emission component (1 keV{5 GeV; photon index 2:022 0:014), present in the phase intervals of the two pulses; ii) a curved spectral component required to describe soft (<100 keV) excess emission present in the same pulse- phase intervals; iii) a broad curved spectral component reflecting the bridge emission from 0.1 keV to 10 MeV. This broad spectral component extends in phase over the full pulse prole in an approximately triangular shape, peaking under the second pulse. Recent model calculations for a three-dimensional pulsar magnetosphere with outer magnetospheric gap acceleration by Cheng et al. (2000) appear at present most successful in explaining the above complex high-energy characteristics of the Crab pulsar.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/c49f494a6a78d0a51168acf720cbdc662a4600e5

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THE NUCLEAR SPECTROSCOPIC TELESCOPE ARRAY (NuSTAR) HIGH-ENERGY X-RAY MISSION (2013, background): “For the Crab Nebula, the integrated spectrum is well-known through the NuSTAR bandpass (though there may remain some disagreements among instruments; Kuiper et al. 2001, Jourdain & Roques 2009).”
THE FIRST FERMI LARGE AREA TELESCOPE CATALOG OF GAMMA-RAY PULSARS (2009, unknown): “LX for E < 100 MeV is taken from Figure 9 of Kuiper et al. (2001).”
The Crab Nebula and Pulsar between 500 GeV and 80 TeV: Observations with the HEGRA Stereoscopic Air Cerenkov Telescopes (2004, methodology): “The high-energy measurements of the Crab Nebula have been summarized recently in Kuiper et al. (2001), to the extent of including ROSAT HRI, BeppoSAX LECS, MECS, and PDS, COMPTEL, and EGRET measurements covering the range from soft X-rays up to gamma-ray emission.”
CALIBRATION OF THE NuSTAR HIGH-ENERGY FOCUSING X-RAY TELESCOPE (2015, background): “The softening above 100 keV primarily comes from the curvature of the pulsed spectrum (Kuiper et al. 2001).”
INTEGRAL observations of the cosmic X-ray background in the 5–100 keV range via occultation by the Earth (2006, methodology): “…measurements of the Crab spectrum (the pulsar plus nebulae) suggest that a single power law is a reasonable approximation below ∼100 keV (e.g Toor & Seward 1974; Seward 1992; Kuiper et al. 2001; Kirsch et al. 2005) with the scatter in the reported values of the photon index of ∼0.1 (see Fig.9).”
Polarization of the Crab Pulsar and Nebula as Observed by the INTEGRAL/IBIS Telescope (2008, background): “…an 77 % polarized signal along the pulsar rotation axis, which is the maximum polarization fraction allowed for synchrotron radiation in a uniform magnetic field and from a power-law distribution of electrons with the spectral index p = 3.454 ± 0.026 recorded at these energies (Kuiper et al. 2001).”
Discovery of Luminous Pulsed Hard X-Ray Emission from Anomalous X-Ray Pulsars 1RXS J1708–4009, 4U 0142+61, and 1E 2259+586 by INTEGRAL and RXTE (2006, unknown): “…the BeppoSAX LECS (Low Energy Concentrator Spectrometer), MECS (Medium Energy Concentrator Spectrometer), PDS Phoswich Detector System spectrum (Kuiper et al. 2001) the derived 15–250 keV HEXTE Crab total spectrum connects smoothly to the 0.3–10 keV Crab total spectrum derived by Willingale et…”
High-Altitude Emission from Pulsar Slot Gaps: The Crab Pulsar (2008, methodology): “The phase-resolved spectra are shown in Figure 4, for the phase ranges adopted by Kuiper et al. (2001) to study the Crab pulsed emission.”
FERMI LARGE AREA TELESCOPE OBSERVATIONS OF THE CRAB PULSAR AND NEBULA (2009, methodology): “Phase histograms in radio (from the Nançay radio telescope), optical (Oosterbroek et al. 2008), X-rays (Rots et al. 2004), hard X-rays (Mineo et al. 2006), γ -rays (CGRO COMPTEL and EGRET; Kuiper et al. 2001), and very high energy (VHE) γ -rays (MAGIC; Aliu et al. 2008) are also plotted in Figure 2”