Spectral evolution is investigated and interpretation of the spectra are considered for a burst from the X-ray burster MXB 1728-34 detected by ASTRON. Interpretation of the spectra around the burst maximum in terms of radiation from an isothermal neutron star (NS) photosphere with dominating role of the Thomson scattering allows one to obtain reasonable constraints on NS mass M, radius R and distance D to the burster. In particular, M=(1.4-2)M⊗, R=(6.5-12) km for D=6 kpc and helium photosphere. This interpretation leads to a conclusion that the photosphere expands up to several tens of kilometers in the burst maximum. The luminosity remains close to the Eddington limit during expansion and contraction, maxima of the observed flux corresponding to minima of the luminosity due to general relativity effects.
All Science Journal Classification (ASJC) codes
- Aerospace Engineering
- Astronomy and Astrophysics
- Atmospheric Science
- Space and Planetary Science
- Earth and Planetary Sciences(all)