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Hipparcos Trigonometric Parallaxes and the Distance Scale for Open Star Clusters

Beshenov, G. V.; Loktin, A. V.

Hipparcos trigonometric parallaxes are used to estimate the distances to the maximum possible number of open star clusters (OSC); distance moduli are estimated for 45 clusters with maximum heliocentric distances of about 1000 pc. The latter value can serve as an estimate of the limit to which it still makes sense to use Hipparcos trigonometric par…

Absolute Magnitudes and Kinematic Parameters of the Subsystem of RR Lyrae Variables

Dambis, A. K.; Rastorguev, A. S.

The statistical parallax technique is applied to a sample of 262 RRab Lyrae variables with published photoelectric photometry, metallicities, and radial velocities and with measured absolute proper motions. Hipparcos, PPM, NPM, and the Four-Million Star Catalog (Volchkov et al. 1992) were used as the sources of proper motions; the proper motions f…

Analysis of HST and IUE Ultraviolet Spectra for T Tauri Stars: DF Tau

Vittone, A. A.; Errico, L.; Lamzin, S. A.

We analyze ultraviolet spectra of DF Tau, a binary system whose primary component is a classical T Tauri star. The spectra were obtained from the Hubble Space Telescope and the IUE satellite. The stellar emission in the wavelength range covered is shown to originate in an accretion shock wave. The gas infall velocity is 250 km/s. The accreted-gas …

Small-Scale High-Temperature Structures in Flare Regions

Chernov, G. P.; Kovalev, V. A.; Hanaoka, I.

When analyzing YOHKOH/SXT, HXT (soft and hard X-ray) images of solar flares against the background of plasma with a temperature T ~ 6 MK, we detected localized (with minimum observed sizes of approximately 2000 km) high-temperature structures (HTSs) with T = (20-50) MK with a complex spatial-temporal dynamics. Quasi-stationary, stable HTSs form a …

Observations of Bright Coronal Points at Wavelengths of 5.2 and 1.76 cm

Maksimov, V. P.; Prosovetskii, D. V.; Krissinel, B. B.

Based on two-dimensional solar images obtained with the Siberian Solar Radio Telescope and the Nobeyama Radio Heliograph and using YOHKOH soft X-ray images, we investigate bright coronal points. The principal microwave emission mechanism of these points is shown to be the thermal bremsstrahlung of an optically thin plasma. The fact that, in severa…

Analysis of IUE Spectra for the Star V1016 Ori

Vitrichenko, É. A.

The Triple System HR 7272

Udry, S.; Griffin, R. F.; Tokovinin, A. A. +2 more

A combined spectroscopic-interferometric orbit is computed for the primary component of the visual binary star HR 7272 = ADS 12101. The orbital period is 3.55 years; semimajor axis 0.074 arcsec. Radial velocities of both components were determined by correlation techniques; their semi-amplitudes are 6.6 and 8.4 km/s. Because those amplitudes are s…

Analysis of the HST Ultraviolet Spectra for T Tauri Stars: RY Tau and HD115043

Lamzin, S. A.

The ultraviolet spectra of the stars RY Tau and HD115043 from the Hubble Space Telescope are analyzed. RY Tau belongs to the classical T Tauri stars, while HD115043 is a young (t ~ 3 x 10^8 years), chromospherically active star. The most intense emission lines were identified, and their fluxes were measured. Low-resolution spectra of RY Tau and HD…

Analysis of HST Ultraviolet Spectra for T Tauri Stars: RU Lup

Lamzin, S. A.

The ultraviolet spectra of the star RU Lup obtained with the Hubble Space Telescope are analyzed. Emission lines are identified. The presence of absorption components with a nearly zero residual intensity in the MgII resonance doublet lines is indicative of mass outflow with a velocity V_infty = 300 km/s. These lines also exhibit a broad (1400 km/…

Evolution of the Symbiotic Star AS338 after Its Strong Outburst in 1983

Munari, U.; Mikolajewska, J.; Kolotilov, E. A. +5 more

The photometric UBV observations of AS338 that we began after its outburst in 1983 are presented. They were accompanied by yearly spectroscopic observations and by occasional estimations of the star's infrared JHKL magnitudes. In June 1993, the star's optical spectrum was extended to the ultraviolet via IUE observations of AS338. Collectively, the…