X-ray polarimetry and evolution of isolated neutron stars

• Applicant: Professor Dr. Klaus Werner
• Subject Area: Astrophysics and Astronomy
• Term: from 2019 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 409501728

• Final Report Year: 2023

Final Report Abstract

We achieved about 75% of our initial aims concerning the investigations of X-ray polarization in various types of sources with neutron stars, including the non-pulsing neutron star in HESS J1731-347. Moreover, we performed a few additional tasks which seemed more promising due to opening of the new observational data. They include a hard X-ray luminosity function of cataclysmic variables due to Gaia EDR3 and 105-month BAT catalogue, which explained the observed diffuse hard X-ray emission of the Galactic Ridge and the Nuclear Star Cluster. This luminosity function is also predicting the total number of cataclysmic variables emitting in hard X-rays. It is also important for understanding of cataclysmic variable stars’ evolution. Some first observational data obtained by eROSITA had to be explained and they changed our initial plans. The unique observation of the early fireball phase a nova had to be interpreted by using hot white dwarf model atmospheres, and this kind of model atmosphere spectra set was computed and applied for the interpretation of the observed spectrum. A new distance to the neutron star in HESS J1731-347 found by Gaia made it possible to clarify its basic parameters. The neutron star turns out to be unexpectedly light, about 0.8 solar masses if we assume that it is covered with a homogeneous carbon envelope. The last two publications had a high impact, achieving more than 50 citations within one year.

Publications

• X-ray spectra and polarization from magnetar candidates. Monthly Notices of the Royal Astronomical Society, 492(4), 5057-5074.
  Taverna, R.; Turolla, R.; Suleimanov, V.; Potekhin, A. Y. & Zane, S.
  
• A strangely light neutron star within a supernova remnant. Nature Astronomy, 6(12), 1444-1451.
  Doroshenko, Victor; Suleimanov, Valery; Pühlhofer, Gerd & Santangelo, Andrea
  
• Hard X-ray luminosity functions of cataclysmic variables: joint Swift/BAT and Gaia data. Monthly Notices of the Royal Astronomical Society, 511(4), 4937-4945.
  Suleimanov, Valery F.; Doroshenko, Victor & Werner, Klaus
  
• Expected polarization properties of nonmagnetized CCOs. Astronomy & Astrophysics, 673, A15.
  Suleimanov, Valery F.; Poutanen, Juri; Doroshenko, Victor & Werner, Klaus