Determination of basic neutron star parameters from spectral modeling of X-ray bursters

• Applicant: Professor Dr. Klaus Werner
• Subject Area: Astrophysics and Astronomy
• Term: from 2017 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 330634413

• Final Report Year: 2021

Final Report Abstract

We achieved about 70% of our initial aims concerning the development of the cooling tail method for determination of masses and radii of X-ray bursting neutron stars in Low Mass X-ray Binaries. We additionally followed two new tasks which were not planned at the outset of the project because of new developments in the field. During the course of the project, we focused on a new idea, the determination of white dwarf masses and precise mass accretion rates in intermediate polars based on our grid of models of hard X-ray spectra of these objects. This kind of robust information is important for understanding of the evolution of close binary systems. Performing of this work became highly topical after new observations of the NuSTAR observatory and Gaia DR2. Another new problem that we worked on is connected to the spectral states of low-luminous accreting X-ray pulsars. We concluded that the spectra of the objects at this spectral state are formed in the upper hot layers of NS atmospheres heated by the accreting flow. We note that this idea is closely connected with the planned (and performed) work concerning accretion heated NS atmospheres. The respective publications had a high impact, achieving more than 45 citations within about two years.

Publications

• 2018: Accretion heated atmospheres of X-ray bursting neutron stars. A&A, 619, A114
  Suleimanov, V.F., Poutanen, J., Werner, K.
  (See online at https://doi.org/10.1051/0004-6361/201833581)
• 2018: Evidence for the Photoionization Absorption Edge in a Photospheric Radius Expansion X-Ray Burst from GRS 1747312 in Terzan 6. ApJ, 866, 53
  Li, Z., Suleimanov, V.F., Poutanen, J. Salmi, T., Falanga, M., Nättilä, J., Xu, R.
  (See online at https://doi.org/10.3847/1538-4357/aade8e)
• 2018: Testing the Equation of State with Electromagnetic Observations, in The Physics and Astrophysics of Neutron Stars, Astrophysics and Space Science Library, Springer Nature Switzerland AG, 457, 185
  Degenaar, N., Suleimanov, V.
  (See online at https://doi.org/10.1007/978-3-319-97616-7_5)
• 2019: Hard X-ray view on intermediate polars in the Gaia era. MNRAS, 482, 3622
  Suleimanov, V.F., Doroshenko, V., Werner, K.
  (See online at https://doi.org/10.1093/mnras/sty2952)
• 2020: Magnetospheric return-current-heated atmospheres of rotation-powered millisecond pulsars. A&A, 641, A15
  Salmi, T., Suleimanov, V.F., Nättilä, J., Poutanen, J.
  (See online at https://doi.org/10.1051/0004-6361/202037824)
• 2020: Observational appearance of rapidly rotating neutron stars. X-ray bursts, cooling tail method, and radius determination. A&A, 639, A33
  Suleimanov, V.F., Poutanen, J., Werner, K.
  (See online at https://doi.org/10.1051/0004-6361/202037502)