Astrokit-an efficient program for high-precision differential CCD photometry and search for variable stars

Having a need to perform differential photometry for tens of thousands stars in a several square degrees field, we developed Astrokit program. The software corrects the star brightness variations caused by variations of atmospheric transparency: to this end, the program selects for each star an individual ensemble of reference stars having similar magnitudes and positions in the frame. With ten or more reference stars in the ensemble, the differences between their spectral types and the spectral type of the object studied become unimportant. A strokit searches for variable stars using Robust Median Statistics criterion, which allows candidate variables to be selected more efficiently than by analyzing the standard deviation of star magnitudes. The software allows very precise automatic analysis of long inhomogeneous sets of photometric observations of a large number of objects to be performed, making it possible to find “hot Jupiter” type exoplanet transits and low-amplitude variables. We describe the algorithm of the program and the results of its application to reduce the data of the photometric sky survey in Cygnus as well as observations of the open cluster NGC188 and the transit of the exoplanet WASP-11 b /HAT-P-10 b, performed with the MASTER-II-URAL telescope of the Kourovka Astronomical Observatory of the Ural Federal University.     

The MASTER-II network of robotic optical telescopes. First results

The main stages in the creation of the Russian segment of the MASTER network of robotic telescopes is described. This network is designed for studies of the prompt optical emission of gammaray bursts (GRBs; optical emission synchronous with the gamma-ray radiation) and surveys of the sky aimed at discovering uncataloged objects and photometric studies for various programs. The first results obtained by the network, during its construction and immediately after its completion in December 2010, are presented. Eighty-nine alert pointings at GRBs (in most cases, being the first ground telescopes to point at the GRBs) were made from September 2006 through July 2011. The MASTER network holds first place in the world in terms of the total number of first pointings, and currently more than half of first pointings at GRBs by ground telescopes are made by the MASTER network. Photometric light curves of GRB 091020, GRB 091127, GRB 100901A, GRB 100906A, GRB 10925A, GRB 110106A, GRB 110422A, and GRB 110530A are presented. It is especially important that prompt emission was observed for GRB 100901A and GRB 100906A, and thar GRB 091127, GRB 110422A, and GRB 110106A were observed from the first seconds in two polarizations. Very-wide-field cameras carried out synchronous observations of the prompt emission of GRB 081102, GRB 081130B, GRB 090305B, GRB 090320B, GRB 090328, and GRB 090424. Discoveries of Type Ia supernovae are ongoing (among them the brightest supernova in 2009): 2008gy, 2009nr, 2010V, and others. In all, photometry of 387 supernovae has been carried out, 43 of which were either discovered or first observed with MASTER telescopes; more than half of these are Type Ia supernovae. Photometric studies of the open clusters NGC 7129 and NGC 7142 have been conducted, leading to the discovery of 38 variable stars. Sixty-nine optical transients have been discovered.     

Analysis of Key Technologies for a Space Geophysics Mission: Required Accuracies and Engineering Solutions

Solar System Research - Abstract—The paper analyzes the Russian scientific and technological capabilities to manufacture a space-borne observation platform for high-precision monitoring of...     

Spots and activity cycles of the star FKCom—2013–2015 data analysis

We present an analysis of new photometric and spectropolarimetric observations of a chromospherically active star FKCom. Based on this observational data and the data from the literature sources, applying a common technique, we performed an analysis of a complete set of the available photometric data, which were divided into 218 individual light curves. For each of them a reverse problem of restoring largescale temperature irregularities on the surface of the star from its light curve was solved. We analyzed the time series for the brightness of the star in the U-, B-, and V-bands, the brightness variability amplitudes, the total area of the spots on the surface of the star, and the average brightness of each set considered. The analysis of determination results of the positions of active longitudes leads to the conclusion about the existence of two systems of active regions on the FKCom surface. It was determined that the positions of each of these systems undergo cyclic changes. This confirms the conclusion on the likely absence of a strongly pronounced regularity of the flip-flops in FKCom, earlier suggested by other researchers. The results of the new polarimetric observations FKCom in 2014–2015 are presented. These measurements evidence the legitimacy of the proposed interpretation the behavior of the longitudinal magnetic field strength 〈B_z〉, indicating the settling-in of a more symmetric distribution of magnetic region on the FKCom surface. An increasing activity of the star over the recent years, registered from the photometric observations is also consistent with the probable onset of growth in the 〈B_z〉 parameter starting from 2014.