The masses of the neutron and donor star in the high-mass X-ray binary IGR J18027-2016

Abstract

Aims. We report near-infrared observations of the supergiant donor to the eclipsing high mass X-ray binary pulsar IGR J18027-2016. We aim to determine its spectral type and measure its radial velocity curve and hence determine the stellar masses of the components. Methods. ESO/VLT observations of the donor utilising the NIR spectrograph ISAAC were obtained in the H and K bands. The multiepoch H band spectra were cross-correlated with RV templates in order to determine a radial solution for the system. Results. The spectral type of the donor was confirmed as B0-1 I. The radial velocity curve constructed has a semi-amplitude of 23.8 ± 3.1 km s −1 . Combined with other measured system parameters, a dynamically determined neutron star mass of 1.4 ± 0.2-1.6 ± 0.3 M is found. The mass range of the B0-B1 I donor was 18.6 ± 0.8-21.8 ± 2.4 M . These lower and upper limits were obtained under the assumption that the system is viewed edge-on (i = 90 • with β = 0.89) for the lower limit and the donor fills its Roche lobe (β = 1 with i = 73.1 • ) for the upper limit respectively.

Supergiant fast X-ray transients as an under-luminous class of supergiant X-ray binaries

“…The source undergoes regular X-ray eclipses and features a typical X-ray variability by a factor of 10-50 as expected for a classical SgXB (Walter et al, 2006). The companion star is a B0-BI supergiant located at a distance of 12.4 kpc (Mason et al, 2011). This source is well suited to be monitored by XRT as its average X-ray flux (a few 10 −11 erg cm −2 s −1 ) is low enough to cause only a moderate pile-up and at the same time its X-ray emission can be reasonably well characterized by short pointings of 1-2 ks.…”

High-mass X-ray binaries in the Milky Way

“…With a spin period of 139.612 sec and an orbital period of 4.4696 days, its orbit could be reconstructed Mason et al, 2011). Its X-ray continuum, typical of an accreting pulsar, is moderately absorbed with N H ≈ 0.9 × 10 23 cm −2 and the presence for an Iron line .…”

Ephemeris, orbital decay, and masses of ten eclipsing high-mass X-ray binaries

“…Input and output parameters for the MC simulations used to finally estimate the mass of the NSs hosted in the ten HMXBs. Mason et al (2011); (e) Quaintrell et al (2003); ( f ) Mason et al (2010), (g) Mason et al (2012); (h) Howarth et al (1997); (i) Zuiderwijk (1995); ( j) evaluated at periastron; (k) we used the same Ω as for SMC X-1 since the values of v rot sin i for these systems are compatible to within the uncertainties (see also Rawls et al 2011); (l) we assumed a value of K opt derived from the average of the other systems in this table with properties close to XTE J1855-026; (m) we assume a conservative Ω value to be close to the Roche lobe radius; ( * ) we treat 4U 1700-377 differently, since the project semi-major axis, a x sin i, is unknown; see Sect. 5.1.…”

“…The neutron star masses for LMC X-4, Cen X-3, 4U 1538-52, SMC X-1, and Vela X-1 are taken from Rawls et al (2011), while the mass of the neutron star hosted in 4U 1700-377 is derived from Clark et al (2002). The corresponding values for SAX J1802.7-2017, EXO 1722-363, and OAO 1657-415 are obtained from Mason et al (2011Mason et al ( , 2010Mason et al ( , 2012. We note that our estimated uncertainties on the neutron star masses are somewhat more conservative than those reported by Rawls et al (2011) and slightly smaller than those obtained by Clark et al (2002) and Mason et al (2011Mason et al ( , 2010Mason et al ( , 2012.…”