Study of Pluto's Atmosphere Based on 2020 Stellar Occultation Light Curve Results

On 6 Jun 2020, Pluto's stellar occultation was successfully observed at a ground-based observatory and Pluto's atmospheric parameters were investigated. We used an atmospheric model of Pluto (DO15), assuming a spherical and transparent pure N2 atmosphere. Using ray-tracing code the stellar occultation light curve was satisfactorily fitted to this model. We found that Pluto's atmospheric pressure at the reference radius of 1215 km is 6.72+_0.21 {\mu}bar. Our estimated pressure shows a continuation of the increasing pressure studied in 2016 consistent with a seasonal volatile transport model. We concluded that the N2 condensation processes in the Sputnik Planitia glacier are increasing due to the heating of the N2 ice in this basin. This study's result was shown on the diagram of the annual evolution of atmospheric pressure.Comment: 4 figures, 2 table

BVRI photometric observations, light curve solutions and orbital period analysis of BF Pav

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 ∆M = 2.45×10−6 M. 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 or a brown dwarf is 5.4% and 94.6% respectively. If we assume i0 = 90◦, a3 = 8.04 ± 0.33 AU. The mass of the secondary component was also determined following two different methods which result close to each other.Fil: Poro, Atila. The International Occultation Timing Association Middle East section; IránFil: Alicavus, Fahri. Canakkale Onsekiz Mart University; TurquíaFil: Fernandez Lajus, Eduardo Eusebio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Davoudi, Fatemeh. The International Occultation Timing Association Middle East section; IránFil: MirshafieKhozani, PegahSadat. The International Occultation Timing Association Middle East section; IránFil: Blackford, Mark G.. Congarinni Observatory; AustraliaFil: Budding, Edwin. Université du Québec a Montreal; CanadáFil: Jalalabadi, Behjat Zarei. Carter Observatory; Nueva ZelandaFil: Rahimi, Jabar. The International Occultation Timing Association Middle; IránFil: Farahani, Farzaneh Ahangarani. The International Occultation Timing Association Middle; Irá