Issue |
A&A
Volume 410, Number 1, October IV 2003
|
|
---|---|---|
Page(s) | 53 - 74 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20031074 | |
Published online | 17 November 2003 |
Properties of discrete X-ray sources in the starburst spiral galaxy M 83
Mullard Space Science Laboratory, University College London, Holmbury St Mary, Surrey RH5 6NT, UK e-mail: Roberto.Soria@mssl.ucl.ac.uk; kw@mssl.ucl.ac.uk
Corresponding author: R. Soria, rs1@mssl.ucl.ac.uk
Received:
3
December
2002
Accepted:
2
July
2003
We have identified 127 discrete sources
in a Chandra ACIS observation of M 83,
with a detection limit of ≈ erg s-1
in the 0.3–8.0 keV band.
We discuss the individual X-ray spectral and time-variability properties
of ≈20 bright sources with luminosities
1038 erg s-1,
and the statistical properties of the whole sample.
About one third of the bright sources show X-ray spectra
with a blackbody component at temperatures
1 keV,
plus a powerlaw component with
,
typical of X-ray binaries in a soft state;
another third have powerlaw spectra with
,
consistent with X-ray binaries in a hard state.
Two bright sources show emission lines on a hard powerlaw continuum,
and are probably X-ray binaries surrounded by a photo-ionized nebula or stellar wind.
Among the other bright sources, we also identified two supernova remnant
candidates,
with optically-thin thermal plasma spectra at temperatures ~0.5 keV.
The two brightest supersoft sources have blackbody temperatures
eV and luminosities ~1038 erg s-1.
Two candidate X-ray pulsars are detected with periods ≈200 s.
One X-ray source corresponds to the core of a background
FRII radio galaxy.
The discrete sources can be divided into three groups,
based on their spatial, color and luminosity distributions.
The first group comprises supersoft sources with no detected
emission above 1 keV
and blackbody spectra at temperatures <100 eV.
The second group consists of soft sources
with little or no detected emission above 2 keV.
They are strongly correlated with Hα emission
in the spiral arms and starburst nucleus, tracing
a young population. Their relative abundance
depends on the current level of star-forming activity
in the galaxy. Most of them are likely to be supernova remnants.
The sources in the third group are mostly X-ray binaries,
reaching higher X-ray luminosities than sources in the other
two groups. Being a mixture of old low-mass and young high-mass systems,
the whole group appears to be of intermediate age when correlated
with the Hα emission. The color-color diagrams allow us
to distinguish between sources in a soft and hard state.
Key words: galaxies: individual: M 83 (=NGC 5236) / galaxies: spiral / galaxies: starburst / X-rays: binaries / X-rays: galaxies
© ESO, 2003
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