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Study of Neglected Variable Stars Classified as Type II Cepheids

Szabados, L.; Berdnikov, L. N.

Four variable stars classified as Type II Cepheids have been studied partly based on new photometry and the Hipparcos photometric data. The correct period is derived for V341 Ara and NW Pav and it is pointed out that RR Mic and V1711 Sgr do not belong to Type II Cepheids, instead they may be semi-regular variables. The cycle length of their variab…

Magnetic Fields in the Inner Heliosphere

Balogh, A.

The structure of Heliospheric Magnetic Field (HMF) is a function of both the coronal conditions from which it originates and dynamic processes which take place in the solar wind. The division between the inner and outer regions of the heliosphere is the result of dynamic processes which form large scale structures with increasing heliocentric dist…

Primordial Helium and DeltaY/DeltaZ from H II Regions and from Fine Structure in the Main Sequence Based on HIPPARCOS Parallaxes

Girardi, L.; Høg, E.; Pagel, B. E. J. +3 more

The primordial helium abundance YP is important for cosmology and the ratio DeltaY/DeltaZ of the changes relative to primordial abundances constrains models of stellar evolution. While the most accurate estimates of YP come from emission lines in extragalactic H II regions, they involve an extrapolation to zero metallicity which itself is closely …

Wide Field Planetary Camera 2 Observations of Proxima Centauri: No Evidence of the Possible Substellar Companion

Golimowski, David A.; Schroeder, Daniel J.

Two-epoch observations of Proxima Centauri using the Hubble Space Telescope (HST) Wide Field Planetary Camera 2 (WFPC2) are reported. Exposures of 10 and 40 s were recorded through the F1042M filter (lambda_c ~ 1 µm), permitting examination of the circumstellar region beyond 0.09" from Proxima Cen. No evidence of a substellar companion withi…

No Death Star--For Now

Gould, Andrew; Frogel, Jay A.

A star passing within ~10⁴ AU of the Sun would trigger a comet shower that would reach the inner solar system about 0.18 Myr later. We calculate an a priori probability of ~0.4% that a star has passed this close to the Sun but that the comet shower has not yet reached the Earth. We search the Hipparcos catalogue for such recent close-en…

Spectral Analysis

Eriksson, Anders I.

The Blue Companion of 3C 65: A Star-forming Galaxy with a Probable Redshift of 2.8

Charlot, Stéphane; Dunlop, J. S.; Owen, Frazer +2 more

We present BVRIK images and photometry of the z = 1.175 radio galaxy 3C 65 and its extended blue companion, along with a 6 cm radio map. These data are used to test the hypotheses that the companion is scattering the continuum of a hidden active nucleus within the radio galaxy and/or is undergoing a starburst triggered by interaction with its radi…

Jovian and terrestrial low-frequency radio bursts: Possible cause of anomalous continuum

Kaiser, M. L.

Observations by the Ulysses Unified Radio and Plasma Wave instrument show that the most intense portion of the Jovian continuum emission appears to emanate from the planet's bow shock or magnetosheath region. This intense component is highly correlated with the Jovian ``type III'' or quasi-periodic (QP-15 and QP-40) bursts. I suggest that this int…

Multi-Spacecraft Filtering: General Framework

Motschmann, Uwe; Pinçon, Jean-Louis

Dramatic change in Sakurai's Object

Roth, M.; Kimeswenger, S.; Kerber, F. +1 more