On the reconstruction of the surface structure of the spotted stars

We have developed and tested a light-curve inversion technique for photometric mapping of spotted stars. The surface of a spotted star is partitioned into small area elements, over which a search is carried out for the intensity distribution providing the best agreement between the observed and model light curves within a specified uncertainty. We have tested mapping techniques based on the use of both a single light curve and several light curves obtained in different photometric bands. Surface reconstruction artifacts due to the ill-posed nature of the problem have been identified.     

Spotted star mapping by light curve inversion: Tests and application to HD 12545

A code for mapping the surfaces of spotted stars is developed. The concept of the code is to analyze rotational-modulated light curves. We simulate the process of reconstruction for the star surface and the results of simulation are presented. The reconstruction atrifacts caused by the ill-posed nature of the problem are deduced. The surface of the spotted component of system HD 12545 is mapped using the procedure.     

Spotted star light curve numerical modeling technique and its application to HII 1883 surface imaging

We developed a code for imaging the surfaces of spotted stars by a set of circular spots with a uniform temperature distribution. The flux from the spotted surface is computed by partitioning the spots into elementary areas. The code takes into account the passing of spots behind the visible stellar limb, limb darkening, and overlapping of spots. Modeling of light curves includes the use of recent results of the theory of stellar atmospheres needed to take into account the temperature dependence of flux intensity and limb darkening coefficients. The search for spot parameters is based on the analysis of several light curves obtained in different photometric bands. We test our technique by applying it to HII 1883.     

Results of the First Year of the 3BS Polar Search Program

Astronomy Letters - We present the results of the first year of searching for polar candidates within the 3BS (3-Band Survey) program using medium-band filters. Observational data for 84 selected...     

Photometric and spectral studies of the eclipsing polar CRTS CSS081231 J071126+440405

We present the results of the study of the eclipsing polar CRTS CSS081231 J071126+440405. Photometric observations allowed us to refine the orbital period of the system \(P_ \circ = 0_ \cdot ^d 0.08137673\). Considerable changes in the appearance of the object’s spectra have occurred over the period of September 20–21, 2001: the slope of the continuum changed from “red” to “blue”, and the variability of the line profiles over the duration of the orbital period has also changed. Doppler maps have shown a shift of the emission line-forming region along the accretion stream closer to the white dwarf. We measured the duration of the eclipse of the system and imposed constraints on the inclination angle \(78_ \cdot ^ \circ 7 < i < 79_ \cdot ^ \circ 3\). The derived radial velocity amplitude was used to obtain the basic parameters of the system: M₁ = 0.86 ± 0.08M_⊙, M₂ = 0.18 ± 0.02 M_⊙, q = 0.21 ± 0.01, R_L2 = 0.20 ± 0.03 R_⊙, A = 0.80 ± 0.03 R_⊙. The spectra of the object exhibit cyclotron harmonics. Their comparison with model spectra allowed us to determine the parameters of the accretion column: B = 31–34 MG, T_e = 10–12 keV, θ = 80–90°, and Λ = 10⁵.     

Analysis of magnetic activity of the rapidly rotating stars He 373 and AP 225

Spectroscopic and photometric data for the two rapidly rotating members of the α Persei cluster He 373 and AP 225 are analyzed. Improved estimates have been obtained for the projected equatorial rotation velocities: v sin i = 164 km/s for He 323 and v sin i = 129 km/s for AP 225. Multi-band photometric mapping is used to map the spot distributions on the surfaces of the two stars. The fractional spotted areas S and mean temperature difference ΔT between the unspotted photosphere and the spots are estimated (S = 7% and ΔT = 1000 K for He 373; S = 9% and ΔT = 800 K for AP 225). The H _α line profiles of both stars have variable emission components whose widths are used to deduce the presence of extended regions of emission reaching the corotation radius.