TUGSAT-1/BRITE-Austria—The first Austrian nanosatellite

A nanosatellite to investigate the brightness oscillations of massive luminous stars by differential photometry is currently developed by a Canadian/Austrian team within the BRITE (Bright Target Explorer) project. The first Austrian satellite funded by the Austrian Space Program, called TUGSAT-1/BRITE-Austria, builds on the space heritage of the most successful Canadian CanX-2 and MOST missions. The satellite makes use of recent advances in miniaturized attitude determination and control systems. Precision three-axis stabilization by small reaction wheels and a star tracker provides the necessary accuracy for the photometer telescope to the arcminute level. This will provide to the astronomers photometric data of the most massive stars with unprecedented precision; data which cannot be obtained from the ground due to limitations imposed by the terrestrial atmosphere.The paper describes the spacecraft characteristics and the ground infrastructure being established in support of the BRITE mission which will consist of a constellation of up to four nearly identical satellites allowing to carry out long-term observation of stars (magnitude +3.5) not only with respect to brightness variations, but also in different spectrum ranges.     

The Cool Interstellar Medium

Infrared spectroscopy and photometry with ISO covering most of the emission range of the interstellar medium has led to important progress in the understanding of the physics and chemistry of the gas, the nature and evolution of the dust grains and also the coupling between the gas and the grains. We review here the ISO results on the cool and low-excitation regions of the interstellar medium, where T _gas≲ 500 K, n _H∼ 100–10⁵ cm⁻³ and the electron density is a few 10⁻⁴. JEL codes: D24, L60, 047 Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, The Netherlands, and the United Kingdom), and with the participation of ISAS and NASA.     

On the optical variability of a be star,HDE 245770, — the optical counterpart of the transient X-ray pulsar A0535+26

Photoelectric WBVR observations of Be star HDE 245770=V 725 Tau, the optical counterpart of the transient X-ray pulsar A0535+26, having a pulse period of about 104 s, were conducted for more than 10 years. An irregular long-term optical variability of the star with amplitudes of the order of a few tenths of magnitude was found to be a usual phenomenon. In some cases rapid changes of the star's optical luminosity with a characteristic period of a few tens of minutes or a few hours, and an amplitude of several hundredths of magnitude in all the spectral bands used, which have practically coincided or correlated with the X-ray pulsar outbursts detected by X-ray satellites, were observed.Photoelectric recording of the optical flux from HDE 245770 were made in 1981–1982 with a time resolution of 1 second and 10 s, respectively, in theR spectral band (₀ 7000 Å) and in the narrowH -emission-line band (_1/2 75 Å) using a 48-cm reflector of High-Mountain Tien-Shan observatory of the Sternberg Astronomical Institute near Alma-Ata. An analysis of autocorrelation functions of the flux changes from object under study and a comparison with the star BD+26° 876 indicated the variability of luminosity of V 725 Tau in theR spectral band on a time scale of a few tens of second; this variability resembles shot noise with a characteristic time of stochastic bursts of about 15–20 s and their amplitudes of about a few tenths of a percent. InH -emission-line radiation autocorrelation functions and power spectra show quasiperiodic variability of luminosity of HDE 245770 with a characteristic period of about 100–150 s and an amplitude in the neighbour-hood of 0.5%. The latter result is not quite reliable because of not quite fine weather conditions during the observations; independent observations and check-up are required.     

Optical search for gamma-ray bursts

The preliminary results from optical search for light pulses associated with gamma ray bursts by means of the Czechoslovak Fireball Network plate collection at the Ondřejov observatory are given. Optical monitoring represents more than 7700 hours, but no real optical counterpart was found. Problems associated with the optical search for gamma ray bursts are discussed.     

木星伽利略卫星互掩互食天象的测光技术

对行星天然卫星互掩互食天象进行测光可以得到非常准确的天体测量信息, 这些信息可以用来进一步改进行卫星的运动理论和历表. 对2003年在云南天文台1米望远镜上实际观测到的互掩互食图像进行测光处理, 分析表明, 在对木星去晕和测光孔径为1.5~2.0倍半高全宽条件下, 所得光变曲线有较好的稳定性.      

Investigations of the evolution of optical characteristics and dynamics of proper rotation of uncontrolled geostationary artificial satellites

On the base of the photometrical data an analysis of the periods and light curves of the uncontrolled artificial satellites was performed.     

New data on the variability of X-ray source KR Aurigae

The results from the photometric observations of the x-ray source KR Aur for the period Oct. 1979 – Mai 1983 obtained at the National Astronomical Observatory, Bulgarian Acedemy of Sciences, are presented. The 1981 – 1982 minimum of the light curve is discussed.     

Global value of Hubble constant

Multiaperture photometry in V (5500Å), r (6738Å) and IV (10500Å) of 52 spirals in nearby clusters Virgo, Fornax and Grus and farther clusters Cancer, Zw 74-23 and Peg I in the redshift range up to 6000 Km s⁻¹ was combined with HI width to derive three independant distances for each galaxy in these clusters.The plot between the mean distance of each cluster and its redshift, indicates the Hubble ratios of distant clusters Cancer, Zw 74-23 and Peg I are about 77 Km s⁻¹ Mpc⁻¹. Further, the Hubble ratios of distant clusters vary only from 76.3 to 78.9 Km s⁻¹ Mpc⁻¹ while those of nearby clusters Virgo, Fornax and Grus vary through a large range of 58.5 to 83.5 Km s⁻¹ Mpc⁻¹. We interpret these data by postulating a systematic motion toward Virgo for the Local Group.The best value for the global Hubble constant from farther and nearby clusters is derived as 74.3± 4 Km s⁻¹ Mpc⁻¹ and an average value of 289±60 Km s⁻¹ for the infall velocity of the Local Group toward Virgo is also derived.     

Determination of visible coordinates of the low-orbit space objects and their photometry by the CCD camera with the analogue output. Initial image processing

The number of artificial space objects in the low Earth orbit has been continuously increasing. That raises the requirements for the accuracy of measurement of their coordinates and for the precision of the prediction of their motion. The accuracy of the prediction can be improved if the actual current orientation of the non-spherical satellite is taken into account. In so doing, it becomes possible to directly determine the atmospheric density along the orbit. The problem solution is to regularly conduct the photometric surveillances of a large number of satellites and monitor the parameters of their rotation around the centre of mass. To do that, it is necessary to get and promptly process large video arrays, containing pictures of a satellite against the background stars.