Issue |
A&A
Volume 412, Number 2, December III 2003
|
|
---|---|---|
Page(s) | L47 - L51 | |
Section | Letters | |
DOI | https://doi.org/10.1051/0004-6361:20034604 | |
Published online | 28 November 2003 |
Letter to the Editor
Line shape diagnostics of Galactic
Al
1
Max-Planck-Institut für extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany
2
Department of Physics & Astronomy, Clemson University, Clemson, SC 29634-0978, USA
Corresponding author: K. Kretschmer, kkr@mpe.mpg.de
Received:
7
July
2003
Accepted:
6
November
2003
The shape of the gamma-ray line from radioactive , at
1808.7 keV energy in the frame of the decaying isotope, is
determined by its kinematics when it decays, typically 106 y after
its ejection into the interstellar medium from its nucleosynthesis
source. Three measurements of the line width exist: HEAO-C's 1982
value of
keV FWHM, the GRIS 1996 value of
keV
FWHM, and the recent RHESSI value of
keV FWHM,
suggesting either “cold”, “hot”, or “warm”
in the ISM. We model
the line width as expected from Galactic rotation, expanding
supernova ejecta, and/or Wolf-Rayet winds, and predict a value below
1 keV (FWHM) with plausible assumptions about
initial velocities
and expansion history. Even though the recent RHESSI measurement
reduces the need to explain a broad line corresponding to
540 km s-1 mean
velocity through extreme assumptions about
grain transport of
or huge interstellar cavities, our results
suggest that standard
ejection models produce a line on the narrow
side of what is observed by RHESSI and INTEGRAL. Improved INTEGRAL and RHESSI
spatially-resolved line width measurements should help to disentangle the
effects of Galactic rotation from the ISM trajectories of
.
Key words: nuclear reactions, nucleosynthesis, abundances / gamma rays: observations / supernovae: general / ISM: supernova remnants / stars: formation
© ESO, 2003
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