Ersin Gogus

The Spectrum and Dips of RE 0751+14: A Joint Evaluation of ROSAT and ASCA Archival Data

Using archival ASCA and ROSAT observations of RE 0751+14, X- ray energy spectra, pulse profiles and the results of pulse timing analysis are presented. The energy spectra are well-fitted by a blackbody model at low energy and a Raymond-Smith model at high energy, together with a partial covering absorber. A fluorescence emission line at 6.4 keV with an equivalent width ∼ 220 eV was resolved for the first time.Using archival ASCA and ROSAT observations of RE 0751+14, X-ray energy spectra, pulse profiles and the results of pulse timing analysis are presented. The energy spectra are well-fitted by a blackbody model at low energy and a Raymond-Smith model at high energy, together with a partial covering absorber. A fluorescence emission line at 6.4 keV with an equivalent width

Dipping and Absorption in the stellar wind in GX 301-2

\sim 220

GRB 090621B: RTT150 optical observations.

eV was resolved for the first time.

Swift XRT Observations of SGR 0418+4729

We present a detailed study of the absorption and dipping behavior of the accreting High Mass Xray Binary GX 301-2. We use data from the XMM-Newton observatory to study the low energy continuum and the iron line complex and data from the Rossi X-ray Timing Explorer (RXTE) to model the continuum and study lightcurves. The analysis of the RXTE data shows that the source is strongly variable: the source exhibits intense flaring as well as dipping activity. The source countrate as recorded by the RXTE-PCA drops to almost zero during some of the dips in the lightcurve. A similar dipping behavior has been observed in the Vela X-1 as well as a number of other massive wind accreting sources. We present a detailed spectral and temporal study of the dips and discuss possible scenarios to explain the dips. The high quality XMM timing mode data are taken during the pre-periastron flare. We accumulate an overall spectrum with very high signal to noise ratio and model it with a partial covering model. The high signal allows us to obtain spectra as short as 30 s to track the evolution of the photoelectric absorption and thus the density of the material in the stellar wind.