Radio-loud and Radio-quiet X-ray Binaries: LSI+61303 in Context

The three basic ingredients - a spinning compact object, an accretion disc and a collimated relativistic jet - make microquasars a galactic scaled-down version of the radio-loud AGN. That explains the large interest attributed to this new class of objects, which up to now consists of less than 20 members. Microquasars belong to the much larger class of X-ray binary systems, where there exists a compact object together with its X-ray emitting accretion disc, but the relativistic jet is missing. When does an X-ray binary system evolve into a microquasar? Ideal for studying such kind of a transition is the periodic microquasar LS I +61303 formed by a compact object accreting from the equatorial wind of a Be star and with more than one event of super-critical accretion and ejection along the eccentric orbit. For ejections at periastron passage the relativistic electrons suffer severe inverse Compton losses by upscattering the UV photons of the Be star at high energy: At periastron passage Gamma-ray emission has been observed, whereas radio outbursts have never been observed in 20 years of radio flux monitoring. For ejections displaced from periastron passage the losses are less severe and radio outbursts are observed. The radio emission mapped on scales from a few AU to hundreds of AU shows a double-sided relativistic (beta=0.6c) S-shaped jet, similar to the well-known precessing jet of SS 433.Comment: Invited talk. 7th EVN Symposium. Bachiller,Colomer,Desmurs,de Vincente (eds) October 12th-15 2004, Toledo, Spai

Introduction to Astrophysics of Microquasars

The Astrophysics of microquasars - galactic miniatures of the far distant quasars - has become one of the most active fields of modern Astronomy in recent years. Here I review the astronomical methods used for the investigation of these objects, from Gamma-rays over X-rays and optical to radio wavelengths. The description of each astronomical method is always followed by an examplary application on the source LS I+61 303, one of the most observed Be/X-ray binary systemsComment: 41 figures, 70 pages, Habilitation Thesis in English (Astronomy, University of Bonn, June 2005

Hour time-scale QPOs in the X-ray and radio emission of LS I +61∘^{\circ}303

LS I +61$^{\circ}$303 is an X-ray binary with a radio outburst every ~27 days. Previous studies of the stellar system revealed radio microflares superimposed on the large radio outburst. We present here new radio observations of LS I +61$^{\circ}$303 at 2.2 GHz with the Westerbork Synthesis Radio Telescope (WSRT). Using various timing analysis methods we find significant Quasi-Periodic Oscillations (QPOs) of 55 minutes stable over the duration of 4 days. We also use archival data obtained from the Suzaku satellite at X-ray wavelengths. We report here for the first time significant X-ray QPOs of about 2 hours present over the time span of 21 hours. We compare our results with the previously reported QPO observations and we conclude that the QPOs seem to be associated with the radio outburst, independent of the amplitude of the outburst. Finally, the different QPO time-scales are discussed in the context of magnetic reconnection

An intervention program related to reading development – a case study of a child with Williams syndrome

The present paper is related to a case study of an 8-year-old girl with Williams syndrome and mild intellectual disability. Initial informal assessments and standardized tests indicated that her reading ability was underdeveloped, as well as her phonological awareness. Hence, an intervention for the development of reading skills was designed according to the principles of the ‘top-down’ educational model, combining features from several teaching methods, such as ‘holistic approach’, ‘holisticanalytical method’, and ‘whole-word teaching’. The student’s progress was recorded in the researcher’s journal and evaluated through informal continuous assessment and standardized test. She managed to read 45 out of 65 words, which were included in the intervention, simple syllables with the consonant-vowel sequence and some simple two-syllable words without any complex content, not included in the intervention. The intervention proved to be effective, as the student indicated development in her reading skills, although to a certain degree. Finally, the results verified the influence of the phonological factor in reading and highlighted the holist approach as an appropriate way to develop reading and comprehension skills