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Item Open Access Analysis of the most precise light curves of HAT-P-36 detrended from spot signals(Fundacja Astronomii Polskiej im. Mikolaja Kopernika,Copernicus Foundation for Polish Astronomy, 2021-11-22) Yalçınkaya, S.; Baştürk, Ö.; El Helweh, Fadel; Esmer, E. M.; Yörükoğlu, O.; Yılmaz, M.; Şenavcı, H.V.; Kılıçoğlu, T.; Selam, S. O.We study the most precise light curves of the planet-host HAT-P-36 that we obtained from the ground primarily with a brand-new 80 cm telescope very recently installed at Ankara University Kreiken Observatory of Turkey and also from the space with Transiting Exoplanet Survey Satellite. The main objective of the study is to analyze the Transit Timing Variations (TTV) observed in the hot-Jupiter type planet HAT-P-36 b, a strong candidate for orbital decay, based on our own observations as well as that have been acquired by professional and amateur observers since its discovery. HAT-P-36 displays out-of-transit variability as well as light curve anomalies during the transits of its planet due to stellar spots. We collected and detrended all the complete transit light curves we had access to from these anomalies, which we modeled with EXOFAST and measured the mid-transit times forming a homogeneous data set for a TTV analysis. We found an increase in the orbital period of HAT-P-36 b at a rate of 0.014 s per year from the best fitting quadratic function, which is only found in the TTV constructed by making use of the mid-transit times measured from detrended light curves, against an expectation of an orbital decay based on its parameters. We refined the values of these system parameters by modeling the Spectral Energy Distribution of the host star, its archival radial velocity observations from multiple instruments, and most precise transit light curves from the space and the ground covering a wide range of wavelengths with EXOFASTV2. We also analyzed the out-of-transit variability from TESS observations to search for potential rotational modulations through a frequency analysis. We report a statistically significant periodicity in the TESS light curve at 4.22 +/- 0.02 d, which might have been caused by instrumental systematics but should be tracked in the future observations of the target.Item Restricted Çocuk ruh sağlığı ve psikiyatrisini Türkiye’ye tanıtan doktor: Atalay Yörükoğlu(Bilkent University, 2020) Yörükoğlu, Emel Yasemin; Çimşit, Deniz; Bayar, Utku; Acar, Alara; Kınay, Emre CanÇocuk ve Ergen Psikiyatrisi, çocukluk ve ergenlik dönemindeki bireylerin akıl sağlığıyla ilgilenir. Bu Anabilim Dalının Türkiye’de kuruculuğunu üstlenen Profesör Doktor Atalay Yörükoğlu’nun hayatı, makalemizin ana konusudur. Konumuz akademik kariyerinin yanında Atalay Yörükoğlu’nun kim olduğunu ve bu ilki nasıl gerçekleştirdiğini de kapsamaktadır. Bu açıdan tıpkı kendisinin çocuk ruh sağlığını inceleyerek insanın temeline inmeyi amaçladığı gibi biz de onun hayat hikayesinin ve Türk toplumuna sağladığı katkıların temellerine inmeyi amaçladık. Makalemizde sırasıyla Çocuk Psikiyatrisinin dünyadaki ve Türkiye’deki tarihinden başlayarak Atalay Yörükoğlu’nun kişisel hayatı, eğitim süreci, kariyeri hayatı, ortaya koyduğu eserler ve Türkiye’ye sağladığı katkılar incelenmiştir.Item Open Access Ginga observations of XI820 — 303 in the globular cluster NGC 6624(Oxford University Press, 1993) Ercan, E. N.; Cruise, A. M.; Kellett, B. J.; Saygili, K.We present the first spectral observations obtained by Ginga of the low-mass X-ray binary source X1820-303 located in the globular cluster NGC6624. Two twocomponent spectral models are found to provide good fits to the data: a bremsstrahlung component plus a blackbody, or a power law with exponential cut-off plus a blackbody. In both cases, inclusion of an iron line at 6.7 keV improves the fits. After considering the importance of Comptonization for the spectral and temporal behaviour, we select the power law plus blackbody model. This model then provides simple explanations for many of the observed features present in our data. The model requires a scattering cloud surrounding the neutron star, with a Thomson optical depth of~ 7. By studying the variation in the amphtude of the 685-s binary period with source luminosity, it is possible to gain some insight into the source geometry. This reveals that our line of sight to X1820 - 303 is close to some ‘critical’ angle. We suggest that gravitationally induced shocks in the rim of the accretion disc cause the height of the rim to vary with azimuthal angle, resulting in the quasi-sinusoidal X-ray orbital modulations. Superposed on this are random ‘dips’ which result from chaotic, timevarying structures in the disc which, principally, only cover the blackbody component of the spectrum.Item Open Access Homogeneous transit timing analyses of 10 exoplanet systems(Oxford University Press, 2022-03-07) Baştürk, Ö.; Esmer, E. M.; Yalçınkaya, S.; Torun, Ş.; Mancini, L.; Helweh, Fadel El; Karamanlı, Ertuğrul; Southworth, J.; Aliş, S.; Wünsche, A.; Tezcan, F.; Aladağ, Y.; Aksaker, N.; Tunç, Ege; Davoudi, F.; Fişek, S.; Bretton, M.; Evans, D. F.; Yeşilyaprak, C.; Yılmaz, M.; Tezcan, C. T.; Yelkenci, K.We study the transit timings of 10 exoplanets in order to investigate potential transit timing variations in them. We model their available ground-based light curves, some presented here and others taken from the literature, and homogeneously measure the mid-transit times. We statistically compare our results with published values and find that the measurement errors agree. However, in terms of recovering the possible frequencies, homogeneous sets can be found to be more useful, of which no statistically relevant example has been found for the planets in our study. We corrected the ephemeris information of all 10 planets we studied and provide these most precise light elements as references for future transit observations with space-borne and ground-based instruments. We found no evidence for secular or periodic changes in the orbital periods of the planets in our sample, including the ultra-short period WASP-103 b, whose orbit is expected to decay on an observable time-scale. Therefore, we derive the lower limits for the reduced tidal quality factors (Q) for the host stars based on best-fitting quadratic functions to their timing data. We also present a global model of all available data for WASP-74 b, which has a Gaia parallax-based distance value ∼25 per cent larger than the published value.