γ-Ray line emission from SS433
Abstract
We report here preliminary evidence for γ-ray line emission from the region of SS433. The observations were accomplished with the high-resolution γ-ray spectrometer aboard the HEAO 3 satellite1. One of the line features reported here, located at an energy of 1.5 MeV, has a statistical significance of ~6 σ during a particular 18-day interval. Another feature appears near 1.2 MeV. Both features exhibit fractional linewidths, ΔE/E, of ~1%. The intensity of the 1.5-MeV feature is variable by a factor of ~3 on a time scale of days with a 46-day time average value of 1.5+/-0.3×10-3 photons cm-2 s-1. The 1.2-MeV feature is similarly variable with a time average intensity of 1.1+/-0.2×10-3 photons cm-2 s-1. The combined power in the lines is ~2 × 1037 erg s-1, assuming isotropic emission from SS433. Phenomena previously observed2,3 from SS433 have been interpreted in terms of a kinematic model4,5 in which two oppositely directed jets of relativistic material (ν = 0.26c) are ejected from a central source. Our observed energies may be explained in terms of this kinematic model as blue- and red-shifted components of the 1.369-MeV line from a nuclear transition of 24Mg from its first excited state to its ground state. Both components appear to vary in energy over the duration of the observation in a manner roughly consistent with the pattern seen in the optical regime2, in which `movement' of optical features is accounted for by a precession of the axis of the jets with a 163.51-day period6. However, this identification implies an anomolously high magnesium abundance relative to carbon and oxygen.
- Publication:
-
Nature
- Pub Date:
- September 1983
- DOI:
- 10.1038/305037a0
- Bibcode:
- 1983Natur.305...37L
- Keywords:
-
- Eclipsing Binary Stars;
- Emission Spectra;
- Gamma Ray Astronomy;
- Variable Stars;
- Energy Spectra;
- Heao 3;
- Line Spectra;
- Spaceborne Astronomy;
- Astrophysics