Context.
We present a new, fast, and easy to use tool for modelling light and radial velocity curves of close eclipsing binaries with built-in methods for solving an inverse problem.
Aims.
The main ...goal of ELISa (Eclipsing binary Learning and Interactive System) is to provide an acceptable compromise between computational speed and precision during the fitting of light curves and radial velocities of eclipsing binaries. The package is entirely written in the Python programming language in a modular fashion, making it easy to install, modify, and run on various operating systems.
Methods.
ELISa implements Roche geometry and the triangulation process to model a surface of the eclipsing binary components, where the surface parameters of each surface element are treated separately. Surface symmetries and approximations based on the similarity between surface geometries were used to reduce the runtime during light curve calculation significantly. ELISa implements the least square trust region reflective algorithm and Markov-chain Monte Carlo optimisation methods to provide the built-in capability to determine parameters of the binary system from photometric observations and radial velocities.
Results.
The precision and speed of the light curve generator were evaluated using various benchmarks. We conclude that ELISa maintains an acceptable level of accuracy to analyse data from ground-based and space-based observations, and it provides a significant reduction in computational time compared to the current widely used tools for modelling eclipsing binaries.
Transit-timing variations in the system Kepler-410Ab Gajdoš, Pavol; Parimucha, Štefan; Hambálek, Ľubomír ...
Monthly notices of the Royal Astronomical Society,
08/2017, Letnik:
469, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Abstract
We present a new analysis of the transit timing variations displayed by the extrasolar planet Kepler-410Ab. We obtained and improved the orbital and physical parameters for the planet and ...analysed 70 transit times obtained by the Kepler satellite. In our analysis of the O-C diagram (observed minus calculated), we assumed that the observed changes in the transit times are probably caused by the gravitational influence of another body in the system. To determine the mass of the perturbing body, we considered the light-time effect and an analytical approximation of the perturbation model. The solutions resulting from both methods give comparable results, with an orbital period P
3 ∼ 970 d and a slightly eccentric orbit of the third body. We also showed that this orbit is nearly coplanar with the orbit of the Neptune-like planet Kepler-410Ab (orbital period 17.8 d). We propose two possible models for the perturbing body orbiting a common barycentre with Kepler-410A: (i) a single star with mass at least 0.906 M⊙, (ii) a binary star with the total mass of its components at least 2.15 M⊙. In both cases, the star Kepler-410B is on a long orbit (period more than 2200 yr). Small amplitude variations (∼5–8 min) detected in O-C residuals can be explained by the stellar activity of the host star (spots and pulsations), which affects the shape of the light curve during the transit. The presence of a single or binary companion of the mentioned masses heavily affects the total observed flux from the system. After removing the flux contamination from the Kepler-410A light curve, we found that the radius of the transiting planet Kepler-410Ab should be in the range from about 3.7 to 4.2 R⊕.
Abstract
We studied three exoplanetary systems with transiting planets: WASP-92, WASP-93, and WASP-118. Using ground-based photometric observations of WASP-92 and WASP-93 and Kepler-K2 observations ...of WASP-118, we redetermined the orbital and physical parameters of these planets. The precise times of all transits were determined. We constructed O–C diagrams of transits and analysed possible transit timing variations. We did not observe any significant deviation from a linear ephemeris for any of the selected exoplanets. We put upper mass limits for other hypothetical planets in these systems. Using long-term numerical simulation, we looked for stable regions where another planet could exist for a long time. We used the maximum eccentricity method for this purpose. We discuss the influence of values of initial inclination and eccentricity on the shape and size of regions of stability.
Abstract
Transit timing variations (TTVs) of Kepler-410Ab were already reported in a few papers. Their semi-amplitude is about 14.5 min. In our previous paper, we found that the TTVs could be caused ...by the presence of a stellar companion in this system. Our main motivation for this paper was to investigate variation in a radial-velocity (RV) curve generated by this additional star in the system. We performed spectroscopic observation of Kepler-410 using three telescopes in Slovakia and Czech Republic. Using the cross-correlation function, we measured the radial velocities of the star Kepler-410A. We did not observe any periodic variation in an RV curve. Therefore, we rejected our previous hypothesis about additional stellar companion in the Kepler-410 system. We ran different numerical simulations to study mean-motion resonances with Kepler-410Ab. Observed TTVs could be also explained by the presence of a small planet near to mean-motion resonance 2:3 with Kepler-410Ab. This resonance is stable on a long time-scale. We also looked for stable regions in the Kepler-410 system where another planet could exist for a long time.
We present a comparison of selected methods for measuring radial velocities in stellar spectra. We compare cross-correlation, line-profile fitting with Gauss, Lorentz and Voigt functions and a ...less-known mirroring method. We discuss their applicability and precision and indicate their advantages and disadvantages. The mirroring method proved to be useful for the analysis of Be stars, but is not implemented in any major astronomical packages.
New photoelectric and CCD observations of the eclipsing contact binary systems V344 Lac and V1191 Cyg are presented and analyzed. All available times of minimum light were used to study period ...changes of the systems and determine up-to-date ephemerides. The orbital period of V1191 Cyg is found to be increasing at a very fast rate. The photometric elements were determined using the new light curve, radial-velocity curve and broadening function fitting code ROCHE.
We present a new, fast, and easy to use tool for modelling light and radial velocity curves of close eclipsing binaries with built-in methods for solving an inverse problem. The main goal of ELISa ...(Eclipsing binary Learning and Interactive System) is to provide an acceptable compromise between computational speed and precision during the fitting of light curves and radial velocities of eclipsing binaries. The package is entirely written in the Python programming language in a modular fashion, making it easy to install, modify, and run on various operating systems. ELISa implements Roche geometry and the triangulation process to model a surface of the eclipsing binary components, where the surface parameters of each surface element are treated separately. Surface symmetries and approximations based on the similarity between surface geometries were used to reduce the runtime during light curve calculation significantly. ELISa implements the least square trust region reflective algorithm and Markov-chain Monte Carlo optimisation methods to provide the built-in capability to determine parameters of the binary system from photometric observations and radial velocities. The precision and speed of the light curve generator were evaluated using various benchmarks. We conclude that ELISa maintains an acceptable level of accuracy to analyse data from ground-based and space-based observations, and it provides a significant reduction in computational time compared to the current widely used tools for modelling eclipsing binaries.
How a black hole accretes matter and how this process is regulated are fundamental but unsolved questions in astrophysics. In transient black-hole binaries, a lot of mass stored in an accretion disk ...is suddenly drained to the central black hole because of thermal-viscous instability. This phenomenon is called an outburst and is observable at various wavelengths (Frank et al., 2002). During the outburst, the accretion structure in the vicinity of a black hole shows dramatical transitions from a geometrically-thick hot accretion flow to a geometrically-thin disk, and the transition is observed at X-ray wavelengths (Remillard, McClintock, 2006; Done et al., 2007). However, how that X-ray transition occurs remains a major unsolved problem (Dunn et al., 2008). Here we report extensive optical photometry during the 2018 outburst of ASASSN-18ey (MAXI J1820\(+\)070), a black-hole binary at a distance of 3.06 kpc (Tucker et al., 2018; Torres et al., 2019) containing a black hole and a donor star of less than one solar mass. We found optical large-amplitude periodic variations similar to superhumps which are well observed in a subclass of white-dwarf binaries (Kato et al., 2009). In addition, the start of the stage transition of the optical variations was observed 5 days earlier than the X-ray transition. This is naturally explained on the basis of our knowledge regarding white dwarf binaries as follows: propagation of the eccentricity inward in the disk makes an increase of the accretion rate in the outer disk, resulting in huge mass accretion to the black hole. Moreover, we provide the dynamical estimate of the binary mass ratio by using the optical periodic variations for the first time in transient black-hole binaries. This paper opens a new window to measure black-hole masses accurately by systematic optical time-series observations which can be performed even by amateur observers.
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