Search Publications
Microflaring of a solar bright point
Curdt, W.; Huovelin, J.; Vilhu, O. +2 more
A 50 x 50 arcsec region near the solar disc center containing a bright point (BP) was observed with the SUMER- spectrograph of the SOHO observatory. The data consist of two hours observation of four far-UV emission lines formed between 2 x 104-6x 105 K, with 2 arcsec spatial, 2.8 min temporal and 4 km s-1 spectral …
Two-Dimensional Spectroscopy of Double-Barred Galaxies
Moiseev, A. V.
We describe the results of our spectroscopy for a sample of barred galaxies whose inner regions exhibit an isophotal twist commonly called a secondary bar. The line-of-sight velocity fields of the ionized gas and stars and the light-of-sight velocity dispersion fields of the stars were constructed from two-dimensional spectroscopy with the 6m Spec…
Observations of Hipparcos short-period red giant stars
Koen, Chris; van Wyk, Francois; Laney, Dave
Optical UBV(RI)C and infrared JHK photometry is presented of a small sample of giant stars with short periods in the Hipparcos catalogue. Observations were limited, but were sufficient to rule out most of the Hipparcos periods. Radial velocity measurement were also made for a few stars, over six successive nights. Low-level variability …
On the kinematic deconvolution of the local neighbourhood luminosity function
Siebert, A.; Pichon, C.; Bienaymé, O.
A method for inverting the statistical star counts equation, including proper motions, is presented; in order to break the degeneracy in that equation, it uses the supplementary constraints required by dynamical consistency. The inversion gives access to both the kinematics and the luminosity function of each population in three régimes: the singu…
An investigation into instrumental nonlinear effects
Walker, S. N.; Balikhin, M. A.; Huff, R. +1 more
High order spectral techniques are one of the most powerful tools for the identification of non-linear processes in space plasma turbulence. Without such tools it is impossible to determine, for example, the occurrence of non-linear interactions between spectral components. However, since the observations made by an instrument involve some interna…
Radial velocities of population II binary stars. I.
Bartkevicius, A.; Sperauskas, J.
Radial velocities for 114 Hipparcos stars, mostly high transverse velocity binaries without previous radial velocity measurements, are published. Measurements are made with the CORAVEL-type radial velocity spectrometer. The accuracy of measurements is better than 1 km/s. Two stars, BD +30 deg 2129A and HD 117466AB are found to be radial velocity v…
The relation between far-UV and visible extinctions
Zagury, Frederic
For directions of sufficient reddening ( E( B- V)>∼0.25), there is a simple relation between the slope of the extinction curve in the far-UV and E( B- V). Regardless of direction, the far-UV extinction curve is proportional to 1/ λn e -2 E( B- V)/ λ ( λ in µm, n=4), in accordance with the idea that reddened stars spe…
Observations of ultraviolet emission lines in solar coronal holes on the disk with SUMER on SOHO
Dammasch, Ingolf E.; Wilhelm, Klaus; Xia, Lidong
The Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrograph and other instruments on the Solar and Heliospheric Observatory (SOHO) have observed many solar polar coronal holes (PCHs) during the minimum of the sunspot cycle in 1996 and 1997. Based on the results obtained for PCHs, investigations of near-equatorial coronal holes (EC…
Cosmic electron gradients in the inner heliosphere
Heber, Bernd; Clem, John; Evenson, Paul
We report the first determination of the radial gradient of cosmic ray electrons in the inner heliosphere at rigidities of 1.2 and 2.5 GV from 1 to 5 AU. Since this determination was made during the A+ solar polarity state, it also constitutes the only determination for particles in a polarity state opposite to their charge sign. We fin…
Observing programs of the Kyiv meridian axial circle equipped with a CCD micrometer
Andruk, V.; Babenko, Yu.; Lazorenko, P. +6 more
The present status of the Kyiv meridian axial circle after its refurbishment is described. The mounting of a new micrometer with the front-illuminated CCD 1040x1160 allows to observe stars up to V=16 mag. For the stars of 11-14 mag, the internal positional accuracy of a single observation is 0.05-0.10'', and stellar V values are determined with an…