6 research outputs found
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 centuryâ1 due to a quadratic trend in the O â 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 âM = 2.45Ă10â6 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 â„ 0.075 M or a brown dwarf is 5.4% and 94.6% respectively. If we assume i0 = 90âŠ, 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; IrĂĄnFil: Alicavus, Fahri. Canakkale Onsekiz Mart University; TurquĂaFil: Fernandez Lajus, Eduardo Eusebio. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto de AstrofĂsica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias AstronĂłmicas y GeofĂsicas. Instituto de AstrofĂsica La Plata; ArgentinaFil: Davoudi, Fatemeh. The International Occultation Timing Association Middle East section; IrĂĄnFil: MirshafieKhozani, PegahSadat. The International Occultation Timing Association Middle East section; IrĂĄnFil: Blackford, Mark G.. Congarinni Observatory; AustraliaFil: Budding, Edwin. UniversitĂ© du QuĂ©bec a Montreal; CanadĂĄFil: Jalalabadi, Behjat Zarei. Carter Observatory; Nueva ZelandaFil: Rahimi, Jabar. The International Occultation Timing Association Middle; IrĂĄnFil: Farahani, Farzaneh Ahangarani. The International Occultation Timing Association Middle; IrĂĄ
Polarization and Spectral Energy Distribution in OJ 287 during the 2016/17 Outbursts
We report optical photometric and polarimetric observations of the
blazar OJ 287 gathered during 2016/17. The high level of activity,
noticed after the General Relativity Centenary flare, is argued to be
part of the follow-up flares that exhibited high levels of polarization
and originated in the primary black hole jet. We propose that the
follow-up flares were induced as a result of accretion disk
perturbations, traveling from the site of impact towards the primary
SMBH. The timings inferred from our observations allowed us to estimate
the propagation speed of these perturbations. Additionally, we make
predictions for the future brightness of OJ 287.</p
New Data on the Eclipsing Binary V1848 Ori and Improved Orbital and Light Curve Solutions
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 systemâs 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 (m3) = 0.0058 Mâ 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 OâConnell effect was not seen in the light curve and there is no need to add spot
Multiband optical flux density and polarization microvariability study of optically bright blazars
We present the results of flux density, spectral index, and polarization
intra-night monitoring studies of a sample of eight optically bright blazars,
carried out by employing several small to moderate aperture (0.4\,m to 1.5\,m
diameter) telescopes fitted with CCDs and polarimeters located in Europe,
India, and Japan. The duty cycle of flux variability for the targets is found
to be percent, similar to that reported in earlier studies. The
computed two-point spectral indices are found to be between 0.65 to 1.87 for
our sample, comprised of low- and intermediate frequency peaked blazars, with
one exception; they are also found to be statistically variable for about half
the instances where `confirmed' variability is detected in flux density. In the
analysis of the spectral evolution of the targets on hourly timescale, a
counter-clockwise loop (soft-lagging) is noted in the flux-spectral index plane
on two occasions, and in one case a clear spectral flattening with the
decreasing flux is observed. In our data set, we also observe a variety of
flux-polarization degree variability patterns, including instances with a
relatively straightforward anti-correlation, correlation, or counter-clockwise
looping. These changes are typically reflected in the flux-polarization angle
plane: the anti-correlation between the flux and polarization degree is
accompanied by an anti-correlation between the polarization angle and flux,
while the counter-clockwise flux-PD looping behaviour is accompanied by a
clockwise looping in the flux-polarization angle representation. We discuss our
findings in the framework of the internal shock scenario for blazar sources.Comment: MNRAS accepte