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Title:
Searching for Annihilation Radiation from SN 1006 with SPI on INTEGRAL
Authors:
Kalemci, E.; Boggs, S. E.; Milne, P. A.; Reynolds, S. P.
Affiliation:
AA(Space Sciences Laboratory, University of California at Berkeley, 7 Gauss Way, Berkeley, CA 94720-7450.; Current address: Sabancı Üniversitesi, Orhanlı-Tuzla, 34956 İstanbul, Turkey.), AB(Space Sciences Laboratory, University of California at Berkeley, 7 Gauss Way, Berkeley, CA 94720-7450.; Department of Physics, University of California at Berkeley, 366 Le Conte Hall, Berkeley, CA 94720-7300.), AC(Steward Observatory, 933 North Cherry Avenue, Tucson, AZ 85721.), AD(Department of Physics, North Carolina State University, 2700 Stinson Drive, Box 8202, Raleigh, NC 27695.)
Publication:
The Astrophysical Journal, Volume 640, Issue 1, pp. L55-L57. (ApJL Homepage)
Publication Date:
03/2006
Origin:
UCP
ApJ Keywords:
Gamma Rays: Observations, ISM: Individual: Alphanumeric: SN 1006, ISM: Supernova Remnants
DOI:
10.1086/503289
Bibliographic Code:
2006ApJ...640L..55K

Abstract

Historical Type Ia supernovae are a leading candidate as the source of positrons observed through diffuse annihilation emission in the Galaxy. However, a search for annihilation emission from individual Type Ia supernovae was not possible before the improved sensitivity of INTEGRAL. The total 511 keV annihilation flux from individual SNe Ia, as well as their contribution to the overall diffuse emission, depends critically on the escape fraction of positrons produced in 56Co decays. Late optical light curves suggest that this fraction may be as high as 5%. We have searched for positron annihilation radiation from the historical Type Ia supernova SN 1006 using the SPI instrument on INTEGRAL. We did not detect significant 511 keV line emission, with a 3 σ flux upper limit of 0.59 ×10-4 photons cm-2 s-1 for ~1 Ms exposure time, assuming a FWHM of 2.5 keV. This upper limit corresponds to a 7.5% escape fraction, 50% higher than the expected 5% escape scenario, and rules out the possibility that Type Ia supernovae produce all of the positrons in the Galaxy (~12% escape fraction), if the mean positron lifetime is less than 105 yr. Future observations with INTEGRAL will provide stronger limits on the escape fraction of positrons, the mean positron lifetime, and the contribution of Type Ia supernovae to the overall positron content of the Galaxy.
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