Dmitry Klochkov (IAAT Tuebingen)

Probing the configuration of the emitting region in accreting magnetized neutron stars
When Apr 12, 2013 from 10:30 AM to 12:00 PM
What
  • Colloquium
Where SH, Lecture hall
Add event to calendar vCal / iCal

Study of accreting magnetized neutron stars (observed as X-ray pulsars) over the last 40 years has led to an understanding of the basic physical mechanisms operating in these sources. Nevertheless a number of key points are still unclear. There is no general agreement neither on the dimensions and shape of the X-ray emitting regions nor on the physical conditions inside them. Both are expected to depend on the pulsar luminosity and the magnetic field strength/configuration. In our work, we use the spectrum-luminosity dependences observed in X-ray pulsars on different time scales to probe the structure of the emitting region. Of particular importance are variations of the cyclotron absorption feature(s), whose centroid energy is proportional to the magnetic field strength at the site of emission. We performed a systematic study of the spectrum-luminosity dependences based on the X-ray data taken with INTEGRAL and RXTE on a sample of bright accreting pulsars. Our results indicate the presence of distinct types of spectral variations with flux which we interpret as a manifestation of different modes of accretion, i.e. different configurations of the accretion column/mound above the star surface. According to our model, different accretions regimes are realized in a source depending on whether its X-ray luminosity determined by the mass accretion rate is above or below certain critical values.

You can download the talk here (pdf, 8 MB).