Eclipsing binary light curves have provided the ‘royal road’ (Russell 1948) to fundamental astrophysical information on stars. If radial velocities of the components and a reliable colour/temperature/flux relation are available, parallaxes may be determined and compared with direct measures, e.g. by Hipparcos. Accuracies of existing measures are considered and aspects of the development of this and other methods of distance determination reviewed. Roles for multiwavelength techniques (e.g. VLBA, broad-spectrum photometry) are noted. The recovery of information on new planets orbiting remote stars by transit phenomena will be looked into within this context.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The CORONAS project is aimed at observation of the Sun in the wide wave-range. The CORONAS-I satellite has been launched to an orbit on 2 March 1994, the CORONAS-F satellite has been launched on 31 July 2001 (see for example Kazachevskaya et al., 1998; Oraevsky et al., 2002). Solar Ultraviolet Radiometer — SUVR provides measurements in the wavelength region $\lambda < 130$ nm and also in the line $L_{\alpha}(\lambda = 121.6)$nm. (Kazachevskaya et al., 1998).To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

With the substantial improvements in observational techniques we have to deal with very big databases, consisting of a few positions of an object over a short time span; this is often not enough to compute a preliminary orbit with traditional tools. In this paper we first review a classical method by C.F. Gauss to compute a preliminary orbit for asteroids. This method, followed by a least squares fit to improve the orbit, still today gives successful results when we have at least three separate observations. Then we introduce the basics of a very recent orbit determination theory, that has been thought just to be used with modern sets of data. These data allow us in many cases to know the angular position and velocity of an asteroid at a given time, even though the radial distance and velocity $(r,\dot r)$, needed to compute its full orbit, are unknown. The variables $(r,\dot r)$ can be constrained to a compact set, that we call the admissible region(AR), whose definition requires that the body belongs to the Solar System, that it is not a satellite of the Earth, and that it is not a “shooting star” (i.e. very close and very small). We provide a mathematical description of the AR: its topological properties are surprisingly simple, in fact it turns out that the AR cannot have more than two connected components. A sampling of the AR can be performed by means of a Delaunay triangulation; a finite number of six-parameter sets of initial conditions are thus defined, with each node of the triangulation representing a possible orbit (a virtual asteroid).To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

RESIK Bragg spectrometer aboard CORONAS-F solar observatory collected spectra of hundreds of solar flares in the unique spectral range between 3.3 Å and 6.1 Å. The instrument's absolute and relative calibrations are now finished which allows for the first time to interpret the observations in terms of the differential emission measure (DEM) distribution. With known DEM shape it is possible to derive and study in detail flaring plasma composition and energy balance. Here we report results of using an improved Maximum Likelihood iterative algorithm (Withbroe-Sylwester) for determination of the DEM distributions for 7 January 2003 flare at 23:30 UT. The study is based on the absolute flux values observed in a number of strong H- and He-like transitions of K xviii, Ar xviii, Ar xvii, S xvi, S xv, Si xiv and Si xiii ions. In this respect, we use line and continuum X-ray emissivities as provided by CHIANTI package from SolarSoft.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

With the advent of the 2004 transit of Venus, interest in historical observations of past transits has been rekindled. We present evidence suggesting that the Maya of the post-classic period actually observed at least one transit of Venus. The frescoes of Mayapan, which are proposed as a record of 12$^{{\rm th}$- or 13$^{{\rm th}}$-century transits, are described and discussed in their astronomical contextTo search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

More than 30 active regions were observed on the Sun during October-November 2003 by SOHO. Approximately half of such regions induced hard X-ray and $\gamma$-ray emission and some solar flares with class M and X were detected during this time by GOES, RHESSI and other experiments. 5 solar flares were detected by AVS-F instrument onboard CORONAS-F satellite. Nuclear $\gamma$-emission lines were detected during some flares observed in this period, in particular, during all flares on October 29 2003.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We report on chromospheric oscillations studied with 15 sec cadence observations obtained at a wavelength of 3.5 mm with the Berkeley-Illinois-Maryland Array (BIMA). Different solar structures, including active and quiet-Sun regions, are analyzed. We compare the high-resolution millimeter 2-D images with Ca II K line images from Big Bear Solar Observatory. Using Fourier and wavelet time series analysis techniques we find signatures of intensity oscillations with periods in the range of 2-7 minutes. We discuss the results in the context of the dynamical model of the solar atmosphere by Carlsson & Stein (1995, 1997).To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The experimental and theoretic investigation of the halo (a detail of local source structure genetically associated with an active region magnetosphere) is presented by the example of the AR 5200 (October, 1988). Accordingly to the high space resolution observations of RATAN-600 and SSRT the emission of this region was almost completely ($\approx 80$%) consist of halo emission. The peculiarities of the observed halo spectrum and polarization with the model explaining these peculiarities are described. It is shown that the inversion phenomenon for the halo is strongly affected by the propagation conditions influence on the polarized emission inside the large source of this emission. The term ‘self-inversion’ is introduced for this effect. Maximum in the halo spectrum at the wavelengths 5–10 cm is clarified by the scattering and by the strong suppression of the emissivity of non-thermal electrons at these and more longer wavelengths.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

This paper discusses the observations of the 1761 and 1769 transits of Venus by the Dutch-German clergyman Johan Maurits Mohr (1716–1775) from Batavia (Dutch East Indies). We will investigate how Mohr became interested in observing this phenomenon and how he made the necessary preparations. Finally, the fate of his observatory and his instruments will be discussed.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Some properties of General Magnetic Fields (GMF) of the Sun as a star and of two solar-like stars (an active young $\xi$ Boo A with no cyclicity of activity, and 61 Cyg A – an old star with a moderate level of cyclic activity) are represented.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present the first center-to-limb G-band images synthesized from high resolution simulations of solar magneto-convection. Towards the limb the simulations show “hilly” granulation with dark bands on the far side, bright granulation walls and striated faculae, similar to observations. At disk center G-band bright points are flanked by dark lanes. The increased brightness in magnetic elements is due to their lower density compared with the surrounding intergranular medium. One thus sees deeper layers where the temperature is higher. At a given geometric height, the magnetic elements are cooler than the surrounding medium. In the G-band, the contrast is further increased by the destruction of CH in the low density magnetic elements. The optical depth unity surface is very corrugated. Bright granules have their continuum optical depth unity 80 km above the mean surface, the magnetic elements 200-300 km below. The horizontal temperature gradient is especially large next to flux concentrations. When viewed at an angle, the deep magnetic elements optical surface is hidden by the granules and the bright points are no longer visible, except where the “magnetic valleys” are aligned with the line of sight. Towards the limb, the low density in the strong magnetic elements causes unit line-of-sight optical depth to occur deeper in the granule walls behind than for rays not going through magnetic elements and variations in the field strength produce a striated appearance in the bright granule walls.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present results from realistic, high resolution, simulations of solar magneto-convection. Simulations were run with both a mean vertical and a mean horizontal field. The magnetic field is quickly swept out of the granules and meso-granules and concentrated in the intergranular lanes.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Magnetic and acoustic properties of the complex active region AR 486 are analyzed for two consecutive days: October 28 and October 29, 2003 when two large flares of magnitude X17.2 and X10 were produced, respectively. Using the technique of helioseismic holography we detected seismic waves emitted from these flares at 6 mHz. SOHO-MDI white light images, magnetograms, and Dopplergrams are used to study the physics of the acoustic sources.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The radial surfaces of constant angular frequency may be connected with the upper rest latitude of the filament bands (or boundaries of large-scale unipolar magnetic regions) and with the separation of the sunspot region and the polar region (polar faculae, etc.). The equator-ward evolution of the rest latitudes observed since cycle 12 may be a forebode of a deep minimum.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

This paper presents the results of the active region observations in red coronal line ($\lambda = 6374 \stackrel{\circ}{\rm A}$). The analysis was made of the dependence of the profile parameters of the red coronal line on the exposition value.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We introduce a Japanese plan for infrared (z-band: 0.9 $\mu$m) space astrometry (the JASMINE-project). It will measure parallaxes, positions with the accuracy of 10 $\mu$as and proper motions with the accuracy of 10 $\mu$as/yr for stars brighter than z$\sim$14. JASMINE can observe about $10^8$ stars belonging to the disk and bulge components of our Galaxy which are hidden by interstellar dust extinction in optical bands. The number of stars with $\sigma_{\pi}/\pi<0.1$ in the direction of the Galactic central bulge is about $10^3$ times larger than those observed in optical bands, where $\pi$ is a parallax and $\sigma_{\pi}$ is an error of the parallax. The main objective of JASMINE is to provide very useful and important astrometric parameters for studying fundamental structures and evolution of the disk and bulge components of the Milky Way Galaxy. Furthermore, the astrometric parameters given by JASMINE will give us exact absolute luminosities and motions of many stars in the bulge and the disk far away from us, so it will promote the study of stellar physics. The information of infrared astrometry that JASMINE will provide is very useful also for investigating stars in star formation regions, gravitational lens effects due to disk stars, extra-solar planets, etc. JASMINE will be launched around 2014 and a candidate for the orbit is a Lissajous orbit around the Sun-Earth L2 point with about a 5-yr mission life. We adopt a 3-mirror optical system (modified Korsch system) with a primary mirror of $\sim$1.5-m diameter in an instrument design of JASMINE. A beam combiner should be used for performance of the global astrometry as used in the Hipparcos satellite. On the astro-focal plane, we put about 100 new-type CCDs for the z-band in which TDI mode (drift scan mode) can be operated. The effective field of view is 0.23 square degrees. The consideration of overall system (bus) design is now going on in cooperation with the Japan Aerospace Exploration Agency (JAXA). Furthermore, we introduce the Nano-JASMINE project which uses a nano-satellite with a size of about 20 cm3 and a weight of a few kg. The objective of Nano-JASMINE is verification of the observing strategy adopted in JASMINE and examination of some important technical issues for the JASMINE project. It will be launched around 2006.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The close collaboration between the two North-country astronomers Jeremiah Horrocks and William Crabtree gave them special insight into the new astronomy published by the recently-deceased Kepler, whereby Horrocks became the only person to apprehend that the Rudolphine tables were in fact predicting a Venus transit in 1639. This paper focuses especially upon William Crabtree's role and contribution. A comparison is made with an earlier, unsuccessful endeavour by these two concerning a possible transit of Mercury. Much of the record of their work was lost during the civil war. Finally, thanks to Christiaan Huygens, Horrock's manuscript was published by Johannes Hevelius in Danzig, in 1662.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The oscillations in solar daily soft X-rays (SXR) have been analyzed for 22$^{nd}$ and 23$^d$ solar cycles. The SXR in the 1–8Å passband have been recorded by the GOES-6,8 satellites from January 1986 to April 2003 year. For 22$^{nd}$ cycle the revealed periodicities 24, 43, 54, 65 and 73 days coincide with the 23$^d$ cycle ones within data uncertainty (1 day) and their values may be explained by the differential rotation of the solar chromosphere and corona.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The variability of solar radiance over a solar cycle is thought to be a delicate balance between the radiative deficit of sunspots and the extra contribution of plage and network regions. Although the net effect is tiny, it must imply structural and thermal changes in the Sun or in partial layers of it as an unavoidable consequence of the virial theorem. Using the virial theorem for continua including the magnetic field it is shown, how solar radiance variability might be connected to a deeply seated flux-tube dynamo and how this connection is established on a hydrodynamical time-scale.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The very weak storm-effectiveness of frontside partial halo coronal mass ejections (FPH CMEs) suggests that many, if not most, FPH CMEs are not Earth-directed. Based on the cone model (Zhao et al., 2002) we put forward a method to identify Earth-directed partial halo CMEs from FPH CMEs.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html