Issue |
A&A
Volume 444, Number 2, December III 2005
|
|
---|---|---|
Page(s) | L33 - L36 | |
Section | Letters | |
DOI | https://doi.org/10.1051/0004-6361:200500204 | |
Published online | 25 November 2005 |
Letter to the Editor
Long-term remnant evolution of compact binary mergers
1
Institut für Astrophysik, Leopold-Franzens Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria e-mail: wilfried.domainko@uibk.ac.at
2
School of Mathematics, University of Edinburgh, Edinburgh EH9 3JZ, Scotland, UK
Received:
25
August
2005
Accepted:
22
October
2005
We investigate the long-term evolution and observability
of remnants originating from the merger
of compact binary systems and discuss the differences to supernova remnants.
Compact binary mergers expel much smaller amounts of mass at much higher
velocities, as compared to supernovae and therefore the free expansion phase
of the remnant will be short (~1-10 yr).
But merger events with high mass ejection exploding in a low density environment
remain in this ejecta dominated stage for several hundred years and
in general the remnants will be
observable for a considerable time (~10 yr).
Events releasing large amounts of
kinetic energy
may be responsible for a subsample of observed giant HI holes of unknown
origin as
compact binaries merge far away
from star forming regions. If the ejecta consist primarily of
actinides, on long timescales the expelled material will contain mainly
the few quasi-stable nuclei in the actinides range. Consequently the
abundance of each isotope in the ejecta might be of the order of a few percent.
During their decay some actinides will produce observational signatures
in form of gamma ray lines.
We particularly investigate the gamma ray
emission of Am 243, Cm 247, Cm 248 and Bi 208 and estimate their
observability in
nearby remnants. Detections of the gamma ray lines with INTEGRAL
will be
possible only in very advantageous cases but these remnants are promising
targets for future instruments using focusing optics for soft gamma rays.
Due to the low mass expelled in mergers and due to the lack of free
electrons in the ejecta, the merger remnants might be significantly fainter
in bremsstrahlung and synchrotron radiation than comparable supernova remnants.
Hence merger remnants might represent a candidate for very recently discovered
“dark accelerators” which are hard gamma ray sources with no apparent emission
in other bands.
Key words: stars: neutron / binaries: close / ISM: bubbles / gamma rays: bursts / nucleosynthesis / abundances
© ESO, 2005
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