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The Etched Hourglass Nebula MYCN 18. II. A Spatio-kinematic Model

Trauger, John T.; Gallagher, John S., III; Dayal, Aditya +4 more

We have observed MyCn18, a young planetary nebula, with Hubble Space Telescope/Wide Field Planetary Camera 2 and have presented the observational results in an earlier paper. Here we present a detailed spatio-kinematic model of Hα emission from the nebula. We model the hourglass-shaped nebular lobes as thin-walled structures in the shape of modifi…

Local Kinematics of Classical Cepheids

Zhu, Zi

Combining Hipparcos proper motions and the radial velocity data, we have studied the Cepheid kinematics on the basis of the three-dimensional Ogorodnikov-Milne model. The results seem to show a slight contracting motion of the Galaxy in the solar neighbourhood, ∂ V_θ / ∂θ / R = ‑2.60 ± 1.07 km s^-1 kpc^-1, which is al…

Extended X-Ray Emission from the Planetary Nebula BD +30°3639

Kwok, Sun; Leahy, D. A.; Yin, Donghui

We report the discovery of extended X-ray emission from the planetary nebula BD +30^deg3639. Analysis of the ROSAT HRI image shows clearly that BD +30^deg3639 has extended X-ray emission which is well fitted with a Gaussian source of σ=1.7"-2.8" (95.4% confidence interval). This size is consistent with being the same as that of…

The May 1997 SOHO-Ulysses quadrature

Romoli, M.; Goldstein, B. E.; Neugebauer, M. +3 more

We present results from the May 1997 SOHO-Ulysses quadrature (SOHO-Sun-Ulysses angle=90°), near sunspot minimum. Ulysses was at 5.1 AU, 10° north of the solar equator, and off the east limb. It was also at the very northern edge of the streamer belt. Nevertheless, the Solar Wind Observations Over the Poles of the Sun instrument (SWOOPS) detected o…

Evolution of White Dwarfs in Cataclysmic Variables

Gänsicke, Boris T.

Has Blending Compromised Cepheid-based Determinations of the Extragalactic Distance Scale?

Gibson, Brad K.; Sakai, Shoko; Maloney, Philip R.

We examine the suggestion that half of the galaxies observed by the Hubble Space Telescope Key Project and the Type Ia Supernova Calibration Team have had their distances systematically underestimated, by 0.1-0.3 mag in the distance modulus, because of the underappreciated influence of stellar profile blending on the Wide Field Camera chips. The s…

Chromospheric two-component NLTE modelling of the binary system V 711 Tau = HR 1099

Lanzafame, A. C.; Rodonò, M.; Busà, I.

In this paper we present the first two-component, semi-empirical chromospheric model of the RS CVn binary system V 711 Tau based on detailed fits of Hα and Mg II h line profiles. Synthetic Hα and Mg II h line profiles are computed by means of NLTE radiative transfer calculations. Using the observed Emission Measure distribution to constrain the tr…

The Orbit of the Classical Cepheid AW Persei Revisited

Evans, Nancy Remage; Wahlgren, Glenn M.; Vinko, Jozsef

We have obtained new velocity data for the classical Cepheid AW Persei and used them to derive a new orbit for the binary star system of which it is part. The orbital period (40 yr) is slightly longer than the previously determined orbit. The lower limit to the mass of the secondary from the new mass function is 6.6 M_solar. This is much…

Solar spectroradiometry with the telescope and spectrograph SUMER on the Solar and Heliospheric Observatory SOHO

Wilhelm, K.; Curdt, W.; Schühle, U. +4 more

Velocity Shear-induced Mode Conversion in Solar Wind and Streamer Plasmas

Kaghashvili, Edisher Kh.; Esser, Ruth

The possible scenario of Alfvén wave transformation into other MHD waves due to inhomogeneous flow in different regions of solar wind/corona is examined. We have chosen four examples with different plasma parameters and velocity shear parameters as representative cases for the plasma conditions. Two of the cases are representative of coronal holes…