Search Publications
Proper motions of Hipparcos stars in two plate areas
Wang, Shu-he; Tang, Zheng-hong; Jin, Wen-jing
Using the ACT reference catalogue as preliminary reference we have reduced 31 exposures on 15 plates in two areas taken with the 40-cm refractor of our Observatory. Using the central overlapping technique and an iterative procedure we have derived high-precision positions and proper motions for 54 stars, including 16 Hipparcos stars. For the latte…
Contributions of the Bucharest Observatory to the CONFOR program
Bocsa, Gheorghe
The connection between the optical reference frame and the radio one constitutes one of the main purposes of the astrometry. The paper is pointing out the contribution of the Bucharest Observatory in this direction. The statistic analysis of the standard errors for the astrometric PPM and TYCHO stars is presented.
Steady Flow Model of a Magnetic Flux Tube Constrained to Observed Differential Emission Measure
Chae, Jongchul; Bong, Su-Chan; Yun, Hong Sik
We have investigated one dimensional steady flow model of a typical magnetic flux tube in the solar transition region constrained to observed Differential Emission Measure (DEM) for the average quiet-Sun deduced by Raymond & Doyle (1981) with a flux tube geometry conforming to Doppler shifts of UV lines measured by Chae, Yun & Poland (1998…
High Angular Resolution Studies of Coronal Structures with SOHO
Karovska, Margarita; Wood, Brian; Cook, John W. +2 more
Since January 1996, the Solar and Heliospheric Observatory (SOHO)has been providing unprecedented views of the extended solar coronato heliocentric distances of up to 32 solar radii. During the past threeyears we carried out studies of the morphology and dynamical evolutionof various structures in the solar corona using two instruments on boardSOH…
The Energy Supply to X-ray Bright Points
Culhane, J. L.; Harra, L. K.; Matthews, S. A. +1 more
X-ray bright points (XBPs) are usually assumed to be isolated structures in the solar atmosphere that are powered exclusively by magnetic reconnection. We analyse a large XBP that does not satisfy this assumption. The XBP is observed to be connected to an active region approximately 280 000 km away by a magnetic loop. We find that the soft X-ray i…
Timing of gamma-ray pulsars: Search in seven-parametric space
Bisnovatyi-Kogan, G. S.; Repin, S. V.
Timing of the Geminga gamma-ray pulsar is done using the data of COS B and EGRET. It is shown, that errors in angular coordinates of sources similar to Geminga strongly influence the determination of , so that at angular precision less then 10^-3 arc sec determination of the value of by means of this criterion gives an error of more than 100%. Att…
The ISOCAM Detectors: an Overview
Gallais, P.; Boulade, O.
The two detectors of the ISOCAM camera on board the ISO spacecraft, have performed nominally for the entire duration of the emission. Their main properties (dark current, noise and responsivity) stayed very stable from the first tests on ground to the end of the life of ISO, a 6 yr long period. The main limitation to the sensitivity of the observa…
Catalogue of 2450 positions of 19 selected minor planets on ICRS system obtained with the zonal astrograph at Nikolaev during 1961-1997
Gorel, G. K.; Gudkova, L. A.
Photographic positions of 19 selected minor planets (SMP), obtained with the Zonal Astrograph at Nikolaev during 1961-1997 were reduced to the ICRS system using reference stars from HIPPARCOS and Tycho star catalogues and proper motions from ACT Reference Catalogue. Rms of one position is 0.16'' in both coordinates.
Effects of a Micrometeorite Stream on the Accuracy of Astrometric Measurements by Scanning Space-Borne Instruments
Mikisha, A. M.; Rykhlova, L. V.; Smirnov, M. A.
The effect of micrometeorite impacts upon the surface of a spacecraft on the accuracy of astrometric measurements made by scanning with instruments onboard the spacecraft is considered. This effect is shown to be marginal for HIPPARCOS measurements. However, disregarding this kind of effect for all the currently projected spacecraft may result in …
Deep Survey Sources, and Predictions for XMM and AXAF
Ptak, A.; Georgantopoulos, I.; Griffiths, R. E. +6 more
From the deep surveys performed with the ROSAT and ASCA X-ray observatories, we have now built up a plausible picture of the constitution of the X-ray background and the way in which AGNs (and starburst nuclei surrounding AGNs) account for it. But major problems remain: the best model that we have is one in which the XRB above 3 kev is accounted f…