Issue |
A&A
Volume 392, Number 3, September IV 2002
|
|
---|---|---|
Page(s) | 909 - 920 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20021184 | |
Published online | 09 September 2002 |
Physical parameters of the high-mass X-ray binary 4U1700-37 *
1
Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT, England, UK
2
Department of Physics and Astronomy, University of Wales, Cardiff, CF24 3YB, Wales, UK
3
Astronomical Institute “Anton Pannekoek”, University of Amsterdam and Center for High-Energy Astrophysics, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
4
Service de Physique Théorique, CP225, Université Libre de Bruxelles, 1050 Brussels, Belgium
5
Astronomical Institute, Utrecht University, Princetonplein 5, 3584 CC, Utrecht, The Netherlands
6
Astrophysics Research Institute, Liverpool John Moores University, Liverpool, L41 1LD, UK
Corresponding author: J. S. Clark, jsc@star.ucl.ac.uk
Received:
22
March
2002
Accepted:
20
June
2002
We present the results of a detailed non-LTE analysis of the
ultraviolet and optical spectrum of the O6.5 Iaf+ star
HD 153919 – the mass donor in the high-mass X-ray binary
4U1700-37. We find that the star has a luminosity
log,
K, radius
, mass-loss rate
yr-1, and a significant
overabundance of nitrogen (and possibly carbon) relative to solar
values. Given the eclipsing nature of the system these results allow
us to determine the most likely masses of both components of the
binary via Monte Carlo simulations. These suggest a mass for
HD 153919 of
– implying the
initial mass of the companion was rather high
(
60
). The most likely mass for the compact companion
is found to be
, with only 3.5 per
cent of the trials resulting in a mass less than 2.0
and
none less than 1.65
. Such a value is significantly in
excess of the upper observational limit to the masses of neutron stars
of 1.45
found by Thorsett & Chakrabarthy
([CITE]), although a mass of 1.86
has recently
been reported for the Vela X-1 pulsar (Barziv et al. [CITE]). Our observational data is inconsistent with the
canonical neutron star mass and the lowest black hole mass observed
(
4.4
; Nova Vel). Significantly changing
observational parameters can force the compact object mass into
either of these regimes but, given the strong proportionality between
and Mx, the O-star mass changes by factors of greater than 2,
well beyond the limits determined from its evolutionary state and
surface gravity. The low mass of the compact object implies that it
is difficult to form high mass black holes through both the Case A &
B mass transfer channels and, if the compact object is a neutron star,
would significantly constrain the high density nuclear equation of
state.
Key words: stars: early-type / stars: individual: HD153919, 4U1700-37 / X–rays: stars / stars: binaries: general
© ESO, 2002
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