In this work we present the solution of the stellar spot problem using the Kelvin-Stokes theorem. Our result is applicable for any given location and dimension of the spots on the stellar surface. We present explicitely the result up to the second de
gree in the limb darkening law. This technique can be used to calculate very efficiently mutual photometric effects produced by eclipsing bodies occulting stellar spots and to construct complex spot shapes.
Transmission spectroscopy during planetary transits, which is based on the measurements of the variations of planet-to-star radius ratio as a function of wavelength, is a powerful technique to study the atmospheric properties of transiting planets. O
ne of the main limitation of this technique is the effects of stellar activity, which up until now, have been taken into account only by assessing the effect of non-occulted stellar spots on the estimates of planet-to-star radius ratio. In this paper, we study, for the first time, the impact of the occultation of a stellar spot and plage on the transmission spectra of transiting exoplanets. We simulated this effect by generating a large number of transit light curves for different transiting planets, stellar spectral types, and for different wavelengths. Results of our simulations indicate that the anomalies inside the transit light curve can lead to a significant underestimation or overestimation of the planet-to-star radius ratio as a function of wavelength. At short wavelengths, the effect can reach to a difference of up to 10% in the planet-to-star radius ratio, mimicking the signature of light scattering in the planetary atmosphere. Atmospheric scattering has been proposed to interpret the increasing slopes of transmission spectra toward blue for exoplanets HD 189733b and GJ 3470b. Here we show that these signatures can be alternatively interpreted by the occultation of stellar plages. Results also suggest that the best strategy to identify and quantify the effects of stellar activities on the transmission spectrum of a planet is to perform several observations during the transit epoch at the same wavelength. This will allow for identifying the possible variations in transit depth as a function of time due to stellar activity variability.
In general, in the studies of transit light-curves and the Rossiter-McLaughlin (RM), the contribution of the planets gravitational microlensing is neglected. Theoretical studies, have, however shown that the planets microlensing can affect the transi
t light-curve and in some extreme cases cause the transit depth to vanish. In this letter, we present the results of our quantitative analysis of microlening on the RM effect. Results indicate that for massive planets in on long period orbits, the planets microlensing will have considerable contribution to the stars RV measurements. We present the details of our study, and discuss our analysis and results.
We present a model-independent technique for calculating the time of mid-transits. This technique, named barycenter method, uses the light-curves symmetry to determine the transit timing by calculating the transit light-curve barycenter. Unlike the o
ther methods of calculating mid-transit timing, this technique does not depend on the parameters of the system and central star. We demonstrate the capabilities of the barycenter method by applying this technique to some known transiting systems including several emph{Kepler} confirmed planets. Results indicate that for complete and symmetric transit lightcurves, the barycenter method achieves the same precision as other techniques, but with fewer assumptions and much faster. Among the transiting systems studied with the barycenter method, we focus in particular on LHS 6343C, a brown dwarf that transits a member of an M+M binary system, LHS 6343AB. We present the results of our analysis, which can be used to set an upper limit on the period and mass of a possible second small perturber.
