Suárez-Andrés, L.; González Hernández, J. I.; Israelian, G.; Casares, J.; Rebolo, R.
Bibliographical reference
Monthly Notices of the Royal Astronomical Society, Volume 447, Issue 3, p.2261-2273
Description
We present Utrecht Echelle Spectrograph@William Herschel Telescope
high-resolution spectra of the low-mass X-ray binary (LMXB) Cygnus X-2.
We have derived the stellar parameters of the secondary star using
χ2 minimization procedure, and taking into account any
possible veiling from the accretion disc. We determine a metallicity
higher than solar ([Fe/H] = 0.27 ± 0.19), as seen also in the
neutron star X-ray binary Centaurus X-4. The high quality of the
secondary's spectrum allow us to determine the chemical abundances of O,
Mg, Si, Ca, S, Ti, Fe, and Ni. We found that some α-elements (Mg,
Si, S, Ti) are enhanced, consistent with a scenario of contamination of
the secondary star during the supernova event. Surprisingly oxygen
appears to be underabundant, whereas enhanced abundances of Fe and Ni
are measured. Assuming that these abundances come from matter that has
been processed in the SN and then captured by the secondary star, we
explore different SN explosion scenarios with diverse geometries. A
non-spherically symmetric SN explosion, with a low mass cut, seems to
reproduce better the observed abundance pattern of the secondary star
compared to the spherical case.
Related projects
Black holes, neutron stars, white dwarfs and their local environment
Accreting black-holes and neutron stars in X-ray binaries provide an ideal laboratory for exploring the physics of compact objects, yielding not only confirmation of the existence of stellar mass black holes via dynamical mass measurements, but also the best opportunity for probing high-gravity environments and the physics of accretion; the most
Observational Tests of the Processes of Nucleosynthesis in the Universe
Several spectroscopic analyses of stars with planets have recently been carried out. One of the most remarkable results is that planet-harbouring stars are on average more metal-rich than solar-type disc stars. Two main explanations have been suggested to link this metallicity excess with the presence of planets. The first of these, the “self
