Akademik Veri Yönetim Sistemi
Tezin Türü: Doktora
Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Fen Edebiyat Fakültesi, Fizik Bölümü, Türkiye
Tezin Onay Tarihi: 2019
Öğrenci: Çiğdem Gamsızkan
Danışman: ALTUĞ ÖZPİNECİ
Özet:This thesis presents an analysis of high-resolution X-ray spectra of four non-magnetic cataclysmic variables based on archival data of XMM-Newton and Chandra observatories. The analysis focuses on the classical novae data in outburst; V2491 Cyg, V4743 Sgr and V407 Lupi taken by XMM-Newton RGS, and KT Eridani taken by Chandra HRC-S+LETG. All these novae have super-soft-source (SSS) type spectra with the broad and blueshifted absorption lines. As an alternative to the static or expanding stellar atmospheric models used in the modeling of the X-ray data, composite models including warm and hot absorbers are constructed and investigated in detail. The continuum is modeled by a blackbody emission, besides a collisionally ionized emission model for V2491 Cyg. The presence of different components of absorption from a warm photoionized and a hot collisionally ionized plasma is detected and included in the models. The absorption lines corresponding to the interstellar medium and dust absorption are modeled in all four sources with slightly different column densities and elemental abundances. The difference in the absorbers, in their column densities, ionizations and temperatures indicate the inhomogeneities in the ejecta and complex morphology of the outflow. We show that the variations within the absorbers in addition to the changes in the central emitting source cause the variations on time scales of hours in the X-ray count rates. The composite model with the absorber components gives a good description of the SSS spectra of all four sources and indicates the necessity of the consideration of the absorptions from the fast-moving and highly ionized plasma in these cases.