Detection of a feature at 0. 44 MeV in the Crab pulsar spectrum with FIGARO II - A redshifted positron annihilation line
- Roma I, Univ., Rome (Italy) Arcetri, Osservatorio Astrofisico, Florence (Italy) CNR, Inst. di Astrofisica Spaziale, Frascati (Italy) Centre d'Etude Spatiale des Rayonnements, Toulouse (France)
The balloon-borne experiment FIGARO II was launched from the base of Trapani-Milo on July 9, 1990 at 0433 UT and observed the Crab pulsar for about 5 hr. The light curve of the signal from PSR 0531 + 21 folded with the radio period shows clearly the known double-peak structure. The spectrum of the second peak, the dominant structure in the hard X-rays and low-energy gamma rays, is characterized by a feature which, if interpreted as an emission line, gives the intensity of (0.86 {plus minus} 0.33) {times} 10 to the {minus}4th photons/sq cm per sec at the energy of 0.44 {plus minus} 0.01 MeV at a confidence level of 99.6 percent. If this feature is the signature of positron annihilation close to the neutron star surface, redshifted by the intense gravitational field, it is possible to estimate the mass-to-radius ratio of the Crab neutron star and the positron production rate from one of the polar caps. The former is equal to 0.087 solar masses/km and the latter 8.2 {times} 10 to the 39th e(+)/s for a pencil-beam pattern, in reasonable agreement with some heuristic estimates based on the number of energetic particles radiating the optical pulses. 16 refs.
- OSTI ID:
- 5157297
- Journal Information:
- Astrophysical Journal; (United States), Vol. 376; Other Information: L11-L15. Research supported by ASI and CNES; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
PULSARS
EMISSION SPECTRA
ANNIHILATION
BRIGHTNESS
GAMMA SPECTRA
NEUTRON STARS
POSITRONS
RED SHIFT
X-RAY SPECTRA
ANTILEPTONS
ANTIMATTER
ANTIPARTICLES
BASIC INTERACTIONS
COSMIC RADIO SOURCES
ELECTROMAGNETIC INTERACTIONS
ELEMENTARY PARTICLES
FERMIONS
INTERACTIONS
LEPTONS
MATTER
OPTICAL PROPERTIES
PARTICLE INTERACTIONS
PHYSICAL PROPERTIES
SPECTRA
STARS
640102* - Astrophysics & Cosmology- Stars & Quasi-Stellar
Radio & X-Ray Sources