Yazar "Davoudi, Fatemeh" seçeneğine göre listele

Listeleniyor 1 - 3 / 3
  • Küçük Resim
    Öğe
    BVRI Photometric Observations, Light Curve Solutions and Orbital Period Analysis of BF Pav
    (IOP Publishing, 2021) Poro, Atila; Aliçavuş, Fahri; Fernandez-Lajus, Eduardo; Davoudi, Fatemeh; MirshafieKhozani, PegahSadat; Blackford, Mark G.; Budding, Edwin; Jalalabadi, Behjat Zarei; Rahimi, Jabar; Farahani, Farzaneh Ahangarani
    A new ephemeris, period change analysis and light curve modeling of the W UMa-type eclipsing binary BF Pav are presented in this study. Light curves of the system taken in BVRI filters from two observatories, in Australia and Argentina, were modeled using the Wilson-Devinney code. The results of this analysis demonstrate that BF Pav is a contact binary system with a photometric mass ratio q = 1.460 +/- 0.014, a fillout factor f = 12.5%, an inclination of 87.97 +/- 0.45 deg and a cold spot on the secondary component. By applying the distance modulus formula, the distance of BF Pav was calculated to be d = 268 +/- 18 pc which is in good agreement with the Gaia EDR3 distance. We obtain an orbital period increase at a rate of 0.142 s century(-1) due to a quadratic trend in the O - C diagram. Also, an alternative sudden period jump probably occurred which could be interpreted as a rapid mass transfer from the lower mass star to its companion of about Delta M = 2.45 x 10(-6) M (circle dot). Furthermore, there is an oscillatory behavior with a period of 18.3 +/- 0.3 yr. Since BF Pav does not seem to have significant magnetic activity, this behavior could be interpreted as the light-time effect caused by an undetected third body in this system. In this case, the probability for the third body to be a low mass star with M >= 0.075 M (circle dot) or a brown dwarf is 5.4% and 94.6% respectively. If we assume i ' = 90 degrees, a (3) = 8.04 +/- 0.33 AU. The mass of the secondary component was also determined following two different methods which result close to each other.
  • [ X ]
    Öğe
    New Data on the Eclipsing Binary V1848 Ori and Improved Orbital and Light Curve Solutions
    (De Gruyter Poland Sp Z O O, 2020) Davoudi, Fatemeh; Poro, Atila; Alicavus, Fahri; Halavati, Afshin; Doostmohammadi, Saeed; Shandadi, AmirAbbas; Vahedi, Sareh
    New observations of the eclipsing binary system V1848 Ori were carried out using the V filter resulting in a determination of new times of minima and new ephemeris were obtained. We presented the first complete analysis of the system's orbital period behavior and analysis of O-C diagram done by the GA and MCMC approaches in OCFit code. The O-C diagram demonstrates a sinusoidal trend in the data; this trend suggests a cyclic change caused by the LITE effect with a period of 10.57 years and an amplitude of 7.182 minutes. It appears that there is a third body with mass function of f (m(3)) = 0.0058 M-circle dot in this binary system. The light curves were analyzed using the Wilson-Devinney code to determine some geometrical and physical parameters of the system. These results show that V1848 Ori is a contact W UMa binary system with the mass ratio of q = 0.76 and a weak fillout factor of 5.8%. The O'Connell effect was not seen in the light curve and there is no need to add spot.
  • Küçük Resim
    Öğe
    Observational and Theoretical Studies of 27 delta Scuti Stars with Investigation of the Period-Luminosity Relation
    (IOP Publishing, 2021) Poro, Atila; Paki, Ehsan; Mazhari, Golnaz; Sarabi, Soroush; Farahani, Farzaneh Ahangarani; Guilani, Hamidreza; Popov, Alexander A.; Zubareva, Alexandra M.; Jalalabadi, Behjat Zarei; Nourmohammad, Mahshid; Davoudi, Fatemeh; Arani, Zahra Sabaghpour; Ghalee, Amir; Alicavuş, Filiz Kahraman
    The multi-color CCD photometric study of 27 δ Scuti stars is presented. By using approximately three years of photometric observations, we obtained the times of maxima and magnitude changes during the observation time interval for each star. The ephemerides of our δ Scuti stars were calculated based on the Markov Chain Monte Carlo (MCMC) method using the observed times of maxima and the period of the stars’ oscillations. We used the Gaia EDR3 parallaxes to calculate the luminosities and also the absolute magnitudes of these δ Scuti stars. The fundamental physical parameters of all the stars in our sample such as masses and radii were estimated. We determined the pulsation modes of the stars based on the pulsation constants. Moreover, the period–luminosity (P–L) relation of δ Scuti stars was investigated and discussed. Then, by using a machine learning classification, new P–L relations for fundamental and overtone modes are presented. Unified Astronomy Thesaurus concepts: Delta Scuti variable stars (370); Photometry (1234) Online material: rar file