HEAO 3 observations of the Crab pulsar

Mahoney, W. A.; Ling, J. C.; Jacobson, Allan

doi:10.1086/161848

Cited by 24 publications

(16 citation statements)

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“…At medium γ-ray energies the first detection of pulsed radiation (0.6-9 MeV) from the Crab pulsar was reported by Hillier et al (1970); see also Walraven et al (1975), Graser & Schönfelder (1982), Mahoney et al (1984) and Agrinier et al (1990).…”

Section: Introductionmentioning

confidence: 98%

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

Kuiper

Hermsen

Cusumano

et al. 2001

A&A

249

280

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Abstract. 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 significantly improved COMPTEL spectra for the Crab nebula and pulsar emissions, and for the first time to accurately determine at low-energy γ-rays the pulse profile 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 γ-rays from CGRO BATSE and at high-energy γ-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 profile 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 first pulse for increasing energies up to ∼1 MeV. Over the COMPTEL energy range above 1 MeV an abrupt morphology change happens: the first pulse becomes again dominant over the second pulse and the bridge emission loses significance such that the pulse profile 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 pulsephase 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 profile 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.

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Section: Introductionmentioning

confidence: 98%

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

Kuiper

Hermsen

Cusumano

et al. 2001

A&A

249

280

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“…Positive detections for such a feature were reported by Leventhal et al (1977), Yoshimori et al (1979), Jung (1989), Ayre et al (1983), Agrinier et al (1990), and Parlier et al (1991), and no detections were reported by Ling et al (1977), Mahoney et al (1984), Hameury et al (1983), andMcConnell et al (1987). (See Owen 1991 for a review.)…”

Section: Introductionmentioning

confidence: 99%

“…The phaseaveraged spectrum of the pulsar measured by HEAO 3 (Mahoney et al 1984), which can be described by a single power law, 1.04 Â 10 À4 (E/100) À2.14 photons cm À2 s À1 keV À1 , accounts for $15% and $18% of the observed flux by BATSE at 100 keV and 1 MeV, respectively. At 10 keV, the pulsed flux (Kuiper et al 2001) accounts for $10% of the total emission.…”

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confidence: 99%

Gamma‐Ray Spectra and Variability of the Crab Nebula Emission Observed by BATSE

Ling¹,

Wheaton²

2003

ApJ

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We report $600 days of BATSE earth occultation observations of the total gamma-ray (30 keV to 1.7 MeV) emission from the Crab Nebula between 1991 May 24 (TJD 8400) and 1994 October 3 (TJD 9628). Light curves from 35-100, 100-200, 200-300, 300-400, 400-700, and 700-1000 keV show that positive fluxes were detected by BATSE in each of these six energy bands at significances of approximately 31, 20, 9.2, 4.5, 2.6, and 1.3 , respectively, per day. We also observed significant flux and spectral variations in the 35-300 keV energy region, with timescales of days to weeks. The spectra below 300 keV, averaged over typical Compton Gamma Ray Observatory viewing periods of 6-13 days, can be well described by a broken power law with average indices of $2.1 and $2.4, varying around a spectral break at $100 keV. Above 300 keV, the long-term averaged spectra, averaged over three 400 day periods (TJD 8400-8800, 8800-9200, and 9200-9628, respectively), are well represented by the same power law with index of $2.34 up to $670 keV, plus a hard spectral component extending from $670 keV to $1.7 MeV, with a spectral index of $1.75. The latter component could be related to a complex structure observed by COMPTEL in the 0.7-3 MeV range. Above 3 MeV, the extrapolation of the power-law continuum determined by the low-energy BATSE spectrum is consistent with fluxes measured by COMPTEL in the 3-25 MeV range and by EGRET from 30-50 MeV. We interpret these results as synchrotron emission produced by the interaction of particles ejected from the pulsar with the field in different dynamical regions of the nebula system, as observed recently by the Hubble Space Telescope, XMM-Newton, and Chandra.

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“…Despite many y ears of extensive study of the Crab pulsar, a detailed understanding of this object is still lacking, and a number of questions about its pulsed emission remain unanswered or open to debate. For example, Mahoney, Ling, & Jacobson 1984 found that the spectrum of the pulsed emission in the region between the two peaks has the same spectral shape in the 0.05 to 10 MeV range as do the pulse peaks, while others e.g., Knight 1982 andHasinger et al 1984 suggest that the spectrum of the interpulse region is di erent. Numerous studies report the detection of lines or spectral features from the Crab nebula and pulsar Leventhal, MacCallum, & Watts 1977;Ling et al 1979;Strickman, Johnson, & Kurfess 1979;Ayre et al 1983;Agrinier et al 1990;Massaro et al 1991Massaro et al , 1992Manchanda et al 1982;Gilfanov et al 1994.…”

Section: Introductionmentioning

confidence: 99%

“…Numerous studies report the detection of lines or spectral features from the Crab nebula and pulsar Leventhal, MacCallum, & Watts 1977;Ling et al 1979;Strickman, Johnson, & Kurfess 1979;Ayre et al 1983;Agrinier et al 1990;Massaro et al 1991Massaro et al , 1992Manchanda et al 1982;Gilfanov et al 1994. In contrast, many other observations have failed to detect these lines Mahoney et al 1984;Ling et al 1977;Schwartz et al 1980;Hameury et al 1983;Knight 1982;Hasinger et al 1982. There have also been reports that the ratio of counts in the two pulse peaks, at energies 50 MeV, varies with time Clear et al 1987;Nolan et al 1993;Kanbach 1990. Previous tests for time variability in the 100 keV range, based on comparisons of light curves, have spanned time scales of less than 10 years Toor & Seward 1977;Mahoney et al 1984;Hasinger et al 1984. A study similar in time duration, detail, and method as the high-energy ones has not been carried out at gamma-ray energies of 100 keV.…”

Section: Introductionmentioning

confidence: 99%

OSSE observations of the Crab pulsar

Ulmer

Lomatch²,

Matz³

et al. 1994

ApJ

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We present preliminary results of the Compton Gamma Ray Observatory OSSE observations of the Crab pulsar. The pulsar energy spectra and light curves are in general agreement with previous observations, validating the OSSE pulsar data acquisition modes and data analysis algorithms. The data suggest that the spectrum of the pulsar varies throughout the light curve. The interpulse" region has a slightly atter spectrum in the 600250 keV region and a slightly steeper spectrum at higher energies than the two main pulses. We nd no evidence for any lines in the spectra with a typical sensitivity of about 10 ,4 photons cm ,2 s ,1 .

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HEAO 3 observations of the Crab pulsar

Cited by 24 publications

References 0 publications

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

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

Gamma‐Ray Spectra and Variability of the Crab Nebula Emission Observed by BATSE

OSSE observations of the Crab pulsar

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