Yazar "Kirmizitas, O." seçeneğine göre listele

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    Öğe
    Candidate Eclipsing Binary Systems with a ? Scuti Star in Northern TESS Field
    (Natl Astronomical Observatories, Chin Acad Sciences, 2022) Alicavus, F. Kahraman; Gumus, D.; Kirmizitas, O.; Ekinci, O.; Cavus, S.; Kaya, Y. T.; Alicavus, F.
    The existence of pulsating stars in eclipsing binaries has been known for decades. These types of objects are extremely valuable systems for astronomical studies as they exhibit both eclipse and pulsation variations. The eclipsing binaries are the only way to directly measure the mass and radius of stars with a good accuracy (<= 1%), while the pulsations are a unique way to probe the stellar interior via oscillation frequencies. There are different types of pulsating stars existing in eclipsing binaries. One of them is the delta Scuti variables. Currently, the known number of delta Scuti stars in eclipsing binaries is around 90 according to the latest catalog of these variables. An increasing number of these kinds of variables is important to understand the stellar structure, evolution and the effect of binarity on the pulsations. Therefore, in this study, we focus on discovering new eclipsing binaries with delta Scuti component(s). We searched within the northern Transiting Exoplanet Survey Satellite (TESS) field with a visual inspection by following some criteria such as light curve shape, the existence of pulsation like variations in the out-of-eclipse light curve and the T (eff) values of the targets. As a result of these criteria, we discovered some targets. The orbital variations were first removed from the TESS light curves and frequency analysis was performed on the residuals. The luminosity, and absolute and bolometric magnitudes of the targets were calculated as well. To find how much of these parameters represent the primary (more luminous) binary component, we also computed the flux density ratio of the systems by utilizing the area of the eclipses. In addition, the positions of the systems in the H-R diagram were examined considering the flux density ratios. As a consequence of the investigation, we defined 38 candidate delta Scuti stars and also one Maia variable in eclipsing binary systems.
  • [ X ]
    Öğe
    Discovery of New ? Scuti Stars
    (Maik Nauka/Interperiodica/Springer, 2022) Kirmizitas, O.; Cavus, S.; Alicavus, F. Kahraman
    Pulsating stars are remarkable objects for stellar astrophysics. Their pulsation frequencies allow us to probe the internal structure of stars. One of the most known groups of pulsating stars is delta Scuti variables which could be used to understand the energy transfer mechanism in A-F type stars. Therefore, in the current study, we focused on the discovery of delta Scuti stars. For this investigation, we followed some criteria. First, we inspected TESS database by eye and discovered some single stars that exhibit pulsation-like behaviour. Our second criterion is T-eff and logg range. The delta Scuti stars generally have T-eff and log g value in a range of 6300-8500 K and 3.2-4.3, respectively. Hence, we selected the stars which have TIC T-eff and logg values in these ranges. The other criterion is the pulsating frequency. A frequency analysis was performed for all the candidate stars. In addition, M-V, L and also M-bol parameters of the target stars were determined to calculate the pulsation constants and show their positions in the H-R diagram. The final pulsation type classification was made by considering the frequency ranges and pulsation constants of the stars. As a result of the study, five delta Scuti, one gamma Doradus and four hybrid systems were discovered.