Search for Redshifted Annihilation Radiation from the Crab Pulsar

Ulmer, M. P.; Matz, S. M.; Grove, J. E.; Strickman, M. S.; Kurfess, J. D.; Ruderman, M.; Zhu, T.; Ho, Cheng

doi:10.1086/320050

Cited by 4 publications

(2 citation statements)

References 14 publications

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“…Note, however, that there is no evidence in favour of the claim of a 0.44 MeV annihilation line from the Crab pulsar by the FIGARO team (see, e.g. Ulmer et al 2001;and references therein). Obviously, the lower bounds on surface redshift obtained here do not represent, in general, the absolute lower bound on surface redshift of NSs.…”

Section: An Application Of the Models To The Crab Pulsarmentioning

confidence: 99%

An upper bound on the energy of a gravitationally redshifted electron-positron annihilation line from the Crab pulsar

Negi¹

2005

A&A

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Abstract. We present a causally consistent and pulsationally stable two component neutron star model on the basis of the criterion that for each assigned value of σ(≡(P 0 /E 0 ) ≡ the ratio of central pressure to central energy-density), the compactness ratio u(≡(M/R), where M is the total mass and R is the radius of the configuration) of the static configuration does not exceed the compactness ratio, u h , of the homogeneous density sphere (that is, u ≤ u h ). The core of this model is given by the stiffest equation of state (EOS), dP/dE = 1 (in geometrized units) and the envelope is characterized by the well-known EOS of aThe models yield an upper bound on surface redshift, z R 0.77, of neutron stars corresponding to the case of Γ 1 = 5/3 envelope, whereas a model-independent upper bound on neutron star masses, M max ≤ 4.1 M , is obtained for a conservative choice of the "matching density", E b = 2.7 × 10 14 g cm −3 , at the core-envelope boundary. If the observational constraint of the glitch healing parameter, Q ≥ 0.7, of the Crab pulsar is imposed on these models, the strong lower bounds on surface redshift z R ≥ 0.2234 and mass M 1.721 M are obtained for the Crab pulsar. However, if the other observational constraint of the recently evaluated value of the moment of inertia for the Crab pulsar (based upon the newly estimated "central value" of the Crab nebula mass M(nebula) 4.6 M ) is also imposed on these models together with the observational constraint of the "central" weighted mean value Q ≈ 0.72, the model with the Γ 1 = 5/3 envelope itself yields the value of matching density, E b = 2.7 × 10 14 g cm −3 , adopted in this study and in this sense does not represent a fiduciary quantity. For these constraints, the minimum surface redshift and mass of the Crab pulsar are slightly increased to the values z R 0.2350 and M 1.807 M respectively. The confirmation of these results requires evidence of the observation of the gravitationally redshifted electron-positron annihilation line in the energy range of about 0.414-0.418 MeV from the Crab pulsar, which is in agreement with the energy of the gamma-ray line at about 0.40 MeV, observed in the mid 1970s.

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Section: An Application Of the Models To The Crab Pulsarmentioning

confidence: 99%

An upper bound on the energy of a gravitationally redshifted electron-positron annihilation line from the Crab pulsar

Negi¹

2005

A&A

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“…Neither "Pulsed" nor "Unpulsed" mean spectra do not demonstrate emission line features. The 3σ upper limits on flux from the possible 440 keV red shifted positron annihilation line (see also [6], [7], [8]) are 3 × 10 −4 and 6 × 10 −4 ph/s/cm 2 , in "Pulsed" and "Unpulsed" emission respectively. These upper limits are higher than the line intensity that was observed previously with other instruments ( [6], [7]).…”

Section: Discussionmentioning

confidence: 99%

The pulse-phase-resolved spectroscopy of the Crab pulsar with SPI/INTEGRAL

Molkov¹

2009

Proceedings of 7th INTEGRAL Workshop — PoS(Integral08)

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We investigated spectral properties of the Crab nebular emission in the pulsar phase plane in the 0.02 − 1.2 Mev energy band with the SPI telescope. After applying a barycentre correction procedure we folded publicly available SPI/INTEGRAL data of ∼ 3.4 Ms Crab observations with radio monthly ephemeris (see [1]). We found that the shape of Crab phase histograms and absolute phases are very stable. In this work we focus attention on the spectral study of "Total pulsed" and "Unpulsed" emission from the Crab nebula. We define "Unpulsed" emission as an appropriately rescaled "Off pulse" phase component ("Unpulsed"="Off pulse"/(0.86 − 0.5)). "Total pulsed" is the total Crab nebular emission minus "Unpulsed". We assumed that pulsating emission is negligible for the "Off pulse" phase component. Both "Pulsed" and "Unpulsed" mean spectra could be well fitted with a broken powerlaw model. We showed that the spectral shape and flux of both the components are very stable in time. Moreover neither "Pulsed" nor "Unpulsed" mean spectra do not reveal emission line features. The 3σ upper limits on possible 440 keV red shifted positron annihilation line in "Pulsed" and "Unpulsed" emission are 3 × 10 −4 and 6 × 10 −4 ph/s/cm 2 , respectively. 7th INTEGRAL Workshop

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Astrophysics in 2001

Trimble¹,

Aschwanden²

2002

PUBL ASTRON SOC PAC

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ABSTRACT. During the year, astronomers provided explanations for solar topics ranging from the multiple personality disorder of neutrinos to cannibalism of CMEs (coronal mass ejections) and extrasolar topics including quivering stars, out-of-phase gaseous media, black holes of all sizes (too large, too small, and too medium), and the existence of the universe. Some of these explanations are probably probably true, though the authors are not betting large sums on any one. The data ought to remain true forever, though this requires a careful definition of "data" (think of the Martian canals).

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Search for Redshifted Annihilation Radiation from the Crab Pulsar

Cited by 4 publications

References 14 publications

An upper bound on the energy of a gravitationally redshifted electron-positron annihilation line from the Crab pulsar

An upper bound on the energy of a gravitationally redshifted electron-positron annihilation line from the Crab pulsar

The pulse-phase-resolved spectroscopy of the Crab pulsar with SPI/INTEGRAL

Astrophysics in 2001

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