... 4U1700-37

Based on observations collected at the European Southern Observatory, La Silla, Chile (64.H-0224).

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

... found

We note that Wellstein & Langer (1999) demonstrate that such limits derived from binary systems cannot be directly applied to single stars.

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

... temperature

Defined, as is usual for an extended atmosphere, as the effective temperature corresponding to the radius at a Rosseland optical depth of 20.

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

... object

Values of $M_{x} <2~M_{\odot}$are only obtained when the radial velocity semi-amplitude, K₀, is >2 $\sigma$ below the observed value, to obtain M_x< 1.6 $M_{\odot }$ would require K₀ to be wrong by several sigma.

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

... transfer

We adopt the nomenclature used in Wellstein & Langer (1999 and references therein), with Case A, B & C evolution corresponding to mass transfer during core hydrogen burning, after core hydrogen burning but before core helium exhaustion, and after core helium burning, respectively.

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

...2001)

We note however, that the difference in the life time of a 60 $M_{\odot }$ star (3.8 Myr) and - for example - a 120 $M_{\odot }$ star (3.0 Myr) is smaller (0.8 Myr) than the uncertainty in the life time of a 60 $M_{\odot }$ star (1 Myr), suggesting that higher progenitor masses may be possible.

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

...$M_{\odot }$

Systematic excursions in the radial velocity curve for this system complicate this determination and prevent an unambiguous confirmation of the mass estimate for the neutron star (Barziv et al. 2001).

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

...1998)

Hyperons such as $\Delta$, $\Sigma$ and $\Lambda$ may also be produced at high density and it is thought that their presence will also soften the equation of state and reduce the overall permitted neutron star mass (Heiselberg & Hjorth-Jensen 1999).

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.