Transient Gamma Ray Spectrometer Measurements of Gamma-Ray Lines from Novae. I. Limits on the Positron Annihilation Line in Five Individual Novae

Abstract

The Transient Gamma Ray Spectrometer (TGRS) on board the WIND spacecraft has spent most of the interval 1995-1997 in a high-altitude orbit where gamma-ray backgrounds are low. Its high-resolution Ge spectrometer is thus able to detect weak lines which are slightly offset from stronger background features. One such line is predicted from nucleosynthesis in classical novae, where beta-decays on a time-scale of a few hours in an expanding envelope produce positrons that annihilate to generate a line which is blueshifted by a few keV away from the background annihilation line at 511 keV. The broad TGRS field of view contained five known Galactic novae during 1995 January - 1997 June, and we have searched the spectra taken around the times of these events for the blueshifted nova annihilation line. Although no definite detections were made, the method is shown to be sensitive enough to detect novae occurring on ONeMg-rich white dwarfs out to about 2.5 kpc.

27 pp. + 10 figs., or offprint mailed by request to [email protected]

References in corpus (4)

• Gamma--ray emission from individual classical novae
• New results on 26Al production in classical novae
• TGRS Measurements of the Positron Annihilation Spectrum from the Galactic Center
• Predictions of gamma-ray emission from classical novae and their detectability by CGRO

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• A New 17F(p,gamma)18Ne Reaction Rate and Its Implications for Nova Nucleosynthesis
• Detectability of gamma-ray emission from classical novae with Swift/BAT
• Gamma-Ray Light Curves and Spectra of Classical Novae
• Transient Gamma Ray Spectrometer Measurements of Gamma-Ray Lines from Novae. II. Constraining the Galactic Nova Rate from a Survey of the Southern Sky during 1995-1997