Yazar "Gok, F." seçeneğine göre listele

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  • [ X ]
    Öğe
    Optical CCD photometry and Rosat X-ray spectral analysis of the shortest period CV EI Psc (1RXS J232953.9+062814)
    (Elsevier, 2009) Gok, F.; Gun, G. Ikis; Aktekin, E.; Sezer, A.; Altan, M.
    We present here the optical observations of EI Psc (1RXS J232953.9 + 062814) through Turkish National Observatory (TUG) with RTT150 cm Russian-Turkish joint telescope and its X-ray observation using the ROSAT archival data. Our optical observations reveal a period of 0.0408 days (58.75 min) which is rather different from its early value of 0.046 days (66.24 min) as reported by [Schmeer, P., 2001. vsnet-alert6830, ]. Also possible periodicities as well as any QPOs are studied without having any clear indication of it. Archival ROSAT RASS data are also analyzed for its X-ray spectra. The raw data were fitted with various spectral models and the best fit models are found to be that of Blackbody and Raymond-Smith with best fit temperatures of kT = (0.07 +/- 0.02) keV for blackbody model and kT =(0.13 +/- 10.04)keV for Raymond-Smith model while the column density fixed at 0.54 x 10(-21) cm(-2). The estimated 0.1-2.4 keV flux is found to be in the range of between logF = -13 and logF = -14 erg cm(-2) s(-1). The model dependent luminosity values were in the range of log L = 29 erg s(-1) for Raymond-Smith model and logL = 31 erg s(-1) for blackbody model. Using the well fitted temperature values, the mass of the primary value that is obtained by [Uemura, M., Kato, T., Ishioka, R., Yamaoka, H., Scgmeer, P., Starkey, D.R., Torii, K., Kawai, N., Urata, Y., Kohama, M., Yoshida, A., Ayani, K., Kawabata, T., Tanabe, K., Matsumoto, K., Kiyota, S., Pietz, J., Vanmunster, T., Krajci, T., Oksanen, A., Giambersio, A., 2002b. Superhump Evolution in the Ultrashort Period Dwarf Nova (1RXS J232953.9 + 062814. PASJ 54, 599-607] and the equations taken from literature, the mass accretion rate in the boundary layer is obtained to be (1.58 +/- 0.14) x 10(21) gs(-1) for the blackbody model and (2.2 +/- 0.052) x 10(19) gs(-1) for Raymond-Smith model. As a result of our study it seems that the system El Psc has a very high mass accretion rate: and because of the observed soft X-ray photons and high mass accretion rates it has an optically thick boundary layer and M-type secondary star which can be a Brown Dwarf. (C) 2008 Elsevier B.V. All rights reserved.
  • [ X ]
    Öğe
    Preliminary results of the spectral analysis of Suzaku data of SW Ursae Majoris and BZ Ursae Majoris
    (Elsevier Science Bv, 2013) Gun, G. Ikis; Karagul, A.; Gok, F.
    Herein, we present the preliminary results of the spectral analysis of the Suzaku data of SW Ursae Majoris (SW UMa) and BZ Ursae Majoris (BZ UMa) which were obtained in their quiescent states. The aim of this study was to analyse 0.5-6.0 key energy range X-ray photons of the Suzaku satellite and to determine their emission mechanisms and the areas where they were radiated from these two dwarf novae. No study on this energy range for BZ UMa has been reported in the literature. We analysed the Suzaku data in the (0.5-6.0) keV and in (0.5-2.5) keV energy bands of the systems separatelly to search for possible differences between the emission mechanisms in the energy ranges; however, none were found. We obtained the best-fitted spectral models, flux, luminosity, temperature and mass accretion rate values for the systems. The white dwarf radius of BZ UMa, which has not been reported in the literature, was found to be 6.88 x 10(8) cm. From this study, we concluded that the mass accretion rate values for both systems were lower than the critical mass accretion rate value in the boundary layers of cataclysmic variables, which indicates that the boundary layers are composed of optically thin thermal X-ray emitting gas in their quiescent state; these results support those of previous studies regarding SW UMa and some studies regarding BZ UMa. Another result was that there can be a coronal structure above the boundary layer which act as soft X-ray emitter for SW UMa. (C) 2013 Elsevier B.V. All rights reserved.