Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı 2

A Study on the Nature of Sw Sextantıs Type of Cataclysmıc Varıables
SW Sextantis (SW Sex) systems are considered as important objects to understand the evolution of cataclysmic variables (CVs) as their orbital periods are just above the period gap: 2,8 hr < P_orb < 4 hr. It is thought that investigating SW Sex-type systems can give clues about the behavior of CVs before entering the period gap. In this thesis, six SW Sex-type CVs were taken among 70 systems given by Ritter and Kolb (2013) and were observed with the IST60 telescope located in Ulupınar Astrophysical Observatory in Çanakkale.
Data taken during observations were reduced and analyzed with IRAF (Image Reduction and Analysis Facility) and light curves were obtained. For each object eclipse depths were determined and compared with the values given in the literature. Additionally, position of the eclipse hump and its amplitude and flickering activity of the system were inspected. Among the targets, HS0129+2933 shows some sudden brightness increase in its eclipse light curves. This finding indicates that system shows strong flickering activity during eclipses.
Among many existing softwares which DCDFT (Data Compensated Discrete Fourier Transform) (Ferraz-Mello, 1981; Foster, 1995) (TS v.1.2; AAVSO (American Association of Variable Star Observers)) including CLEAN algorithms (Roberts et al., 1987) and, Period04 v.1.2 (Lenz & Breger, 2005) were used to detect periodicities in the light curves. Frequency for orbital period and second strongest frequency of PX And was found as f_orb = 7,42296 ± 0,00004 cycle/day (0,134717 day) and f₂ = 6,47787 ± 0,00005 cycle/day (0,154365 day), respectively. Frequencies corresponding to the orbital periods of HS0455+8315 and HS0129+2933 are f_orb = 6,99599 ± 0,00005 cycle/day (0,142939 day) and f_orb = 7,82505 ± 0,00820 cycle/day (0,127794 day), respectively. For V1315 Aql, BH Lyn and HS1813+6122 systems we could not detect any strong periodicities.
Minima times of the eclipses seen in the light curves were computed with Kwee and van Woerden (1956) method. Those times computed in this thesis were combined with other minima times collected from the literature and O-C analysis were done for each system. Except BH Lyn any indication for period change has not been seen. Only BH Lyn shows strong period change as Stanishev et al. (2006) stated before. According to that orbital period of BH Lyn seems increasing.
  

YONTAN Talar

Danışman : Doç. Dr. Selçuk BİLİR

Anabilim Dalı : Astronomi ve Uzay Bilimleri

Programı : -

Mezuniyet Yılı : 2014

Tez Savunma Jürisi : Doç. Dr. Selçuk BİLİR

Prof. Dr. Tansel AK

Prof. Dr. Faruk SOYDUGAN

Doç. Dr. Tolga GÜVER

Doç. Dr. Esma YAZ GÖKÇE