Issue |
A&A
Volume 368, Number 2, March III 2001
|
|
---|---|---|
Page(s) | 420 - 430 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361:20010027 | |
Published online | 15 March 2001 |
BeppoSAX spectroscopy of the luminous X-ray sources in M 33
1
Astrophysics Division, Space Science Department of ESA, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands
2
Dept of Physics & Astronomy, University of Southampton, Southampton, Hants, SO17 1BJ, UK
3
Astronomical Institute "Anton Pannekoek", Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
4
XMM-Newton SOC, ESA Villafranca, Apartado 50727, 28080, Madrid Spain
5
Observatory & Astrophysics Lab., University of Helsinki, Helsinki, Finland
6
Max-Planck-Institut für Extraterrestrische Physik, 85740 Garching bei München, Germany
7
Osservatorio Astronomico di Brera, Via Bianchi 46, Merate 22055, Italy
Corresponding author: A. N. Parmar, aparmar@astro.estec.esa.nl
Received:
16
October
2000
Accepted:
18
December
2000
The nearby galaxy M 33 was observed by the imaging X-ray instruments on-board
BeppoSAX. Two observations at different phases of the 105.9 day
intensity cycle of the luminous central source X-8 failed
to reveal the expected modulation, suggesting that it is
probably transitory. Similar behavior has been observed from
several X-ray binary sources. This strengthens somewhat the
idea that M 33 X-8 is a black hole accreting from a binary
companion. The 0.2-10 keV spectrum of M 33 X-8 can best be
modeled by an absorbed power-law with a photon index, α, of
and a disk-blackbody with a temperature, kT, of
keV and
a projected inner-disk radius of
km.
This spectral shape is in good agreement with earlier ASCA results.
The 2-10 keV spectra of M 33 X-4, X-5, X-7, X-9 and X-10 are all consistent
with power-law or bremsstrahlung models, whilst that of X-6 appears to be
significantly more complex and may be reasonably well modeled with a
disk-blackbody with
keV and
a projected inner-disk radius of
km. The spectrum
of M 33 X-9 is rather hard with
.
Compared to earlier Einstein and ROSAT observations,
M 33 X-7 and X-9 varied in intensity, M 33 X-4, X-6, and X-10
may have varied and M 33 X-5 remained constant.
Key words: galaxies: individual (M 33) / galaxies: nuclei / X-ray: galaxies
© ESO, 2001
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