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
  The good energy resolution (3--4 keV FWHM) of the Transient Gamma Ray Spectrometer (TGRS) on board the WIND spacecraft makes it sensitive to Doppler-shifted outbursts of 511 keV electron-positron annihilation radiation, the reason being that the Doppler shift causes the cosmic line to be slightly offset from a strong instrumental background 511 keV line at rest, which is ubiquitous in space environments. Such a cosmic line (blueshifted) is predicted to arise in classical novae due to the annihilation of positrons from $\beta$-decay on a timescale of a few hours in an expanding envelope. A further advantage of TGRS - its broad field of view, containing the entire southern ecliptic hemisphere - has enabled us to make a virtually complete and unbiased 3-year search for classical novae at distances up to ~1 kpc. We present negative results of this search, and estimate its implications for the highly-uncertain Galactic classical nova rate and for future space missions. 
M.J. Harris (1 and 2), B.J. Teegarden (2), T.L. Cline (2), N. Gehrels   (2), D.M. Palmer (1 and 2), R. Ramaty (2), H. Seifer...