ASTRONS · Astrophysics of Neutron Stars

Final Activity Report Summary - ASTRONS (Astrophysics of Neutron Stars)

Neutron stars represent the largest quantities of matter in the most extreme condensed state. Observing them, we learn about extreme states of matter and fundamental interactions between neutrons, protons and quarks. Stars like our Sun shine by the energy they get from nuclear reactions. When a heavy star runs out of nuclear fuel, it explodes spectacularly leaving behind a neutron star or a black hole. Stars with initial masses 12 to 25 times the mass of the Sun end up in a supernova explosion making a neutron star. Neutron stars are fascinating: with as much mass as the Sun, squeezed into a ball of 10 km radius, densities are about 100 million tons per cubic cm. They spin as fast as 700 times per second! Their magnets are up to 1000 trillion times stronger than the Sun's. They produce light, radio waves, X and Gamma rays. As the star rotates and its beam sweeps us once every rotation, we observe pulses of radiation repeating at the rotation period. Many neutron stars are in binaries accreting matter from their companion star and emitting X-rays. ASTRONS supported theoretical and observational research. We made observations with international X and gamma ray observatory satellites RXTE, Swift, Chandra, Fermi, INTEGRAL and XMM-Newton and used their archives. We learned a lot of interesting new science, resulting in 8 PhD theses, 45 articles in major international scientific journals (+5 submitted) and 11 papers in scientific conferences. The scientific results were disseminated at three ASTRONS Workshops in Istanbul and at ASTRONS Conference in 2010 in Izmir. The training took place via workshops on data analysis (Fermi and timing), and PhD courses. Highlights are: (i) Discovery of two new Soft Gamma-Ray Repeaters (ii) Development of fall back disk model , explaining properties of some young neutron stars by effect of a disk left over from the supernova explosion. Fitted spectrum of light and infrared radiation from first observed fallback disk. (iii) Properties of X-ray binaries as individual sources and as a class. (iv) A demonstration that the reason for not seeing pulses from most low mass X-ray binaries (LMXB) is not due to effects of Compton scattering. (v) Very fast oscillations observed in X-rays from LMXB interpreted as disk oscillations. (vi) How the superconductor and superfluid inside a neutron star effect its dynamics. (vii) Comparison of black hole and neutron star properties with distinct signatures. These exciting results were widely shared with the public, and with teaches and children in primary-secondary schools. In technology we set up the first laboratory in Turkey for building and testing X and gamma ray detectors for scientific research from space. ASTRONS gave the first and largest support for this effort in Turkey, essential for development of space science and technology. The lab, now functioning at Sabanci University started generating support in further grants. A proposal to TUBITAK for a low cost high scientific gain hard X-ray instrument with optimised mask pattern was accepted. A recent FP7 Cooperation proposal with ASTRONS Partner DTU-SPACE and TUBITAK-SPACE explores a wide field X-ray detector on a rotating cubesat.

Data: CORDIS, © European Union