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Trigonometric Parallaxes and a Kinematically Adjusted Distance Scale for OB Associations

Dambis, A. K.; Rastorguev, A. S.; Mel'Nik, A. M.

By directly comparing the photometric distances of Blaha and Humphreys (1989) (BH) to OB associations and field stars with the corresponding Hipparcos trigonometric parallaxes, we show that the BH distance scale is overestimated, on average, by 10-20%. This result is independently corroborated by applying the rigorous statistical-parallax method a…

An Astrometric Study of the Triple Star ADS 48

Kiselev, A. A.; Kiyaeva, O. V.; Polyakov, E. V. +1 more

We analyze the series of relative positions of the hierarchical triple system ADS 48 ABF (AB = 6 arcsec, AF = 327 arcsec) obtained with the 26-inch Pulkovo refractor during 1961-1995 and measured with the Fantazia automated measuring system. A new relative orbit of pair AB is determined by the method of apparent-motion parameters using new observa…

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.