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A multi-wavelength investigation of the non-thermal radio emitting O-star 9 Sgr
Corcoran, M. F.; Blomme, R.; Rauw, G. +7 more
We report the results of a multi-wavelength investigation of the O4 V star 9 Sgr (= HD 164794). Our data include observations in the X-ray domain with XMM-Newton, in the radio domain with the VLA as well as optical spectroscopy. 9 Sgr is one of a few presumably single OB stars that display non-thermal radio emission. This phenomenon is attributed …
Solar wind from high-latitude coronal holes at solar maximum
McComas, D. J.; Elliott, H. A.; von Steiger, R.
In this study we combine Ulysses' observations from the solar wind plasma (SWOOPS) and ion composition (SWICS) instruments to study high-latitude coronal holes near solar maximum for the first time. While chromospheric and coronal composition signatures indicate that there is a unique type of solar wind, which flows from coronal holes, variations …
Associated Absorption in Radio Quasars. I. C IV Absorption and the Growth of Radio Sources
Lehnert, Matthew D.; Athreya, Ramana M.; Saunders, Richard D. E. +4 more
We assess the global properties of associated C IV λλ1548, 1550 absorption lines measured in the spectra of radio-loud quasars drawn from a near-complete, low-frequency-selected sample. The observations span rest-frame C IV in two redshift ranges, 0.7<z<1.0 and 1.5<z<3.0, which were targeted in the UV with the Hubble Space Telescope Sp…
Variability of the Broad Balmer Emission Lines in 3C 390.3 from 1992 to 2000
Zheng, W.; Peterson, B. M.; Pronik, V. I. +2 more
We describe the results of an optical spectral monitoring campaign on the Seyfert galaxy 3C 390.3 carried out with a CCD spectrograph at the 2.6 m Shajn Telescope of the Crimean Astrophysical Observatory in 1992-2000. Light curves for the Hα and Hβ emission lines and for the continuum in both the Hα and Hβ spectral regions are given. The lag betwe…
The draping of heliospheric magnetic fields upstream of coronal mass ejecta
Balogh, A.; Jones, G. H.; Forsyth, R. J. +1 more
The propagation of a fast coronal mass ejection through the interplanetary medium results in compression and draping of existing heliospheric magnetic fields, forming an upstream sheath. Such sheaths are a common context for planar magnetic structures, where the magnetic field is ordered into laminar sheets. A technique is presented to estimate th…
Two-dimensional Structure of a Polar Coronal Hole at Solar Minimum: New Semiempirical Methodology for Deriving Plasma Parameters
Romoli, M.; Poletto, G.; Noci, G. +2 more
We develop a new technique to determine the plasma parameters in a polar coronal hole. This method makes use of the line intensities of the H I Lyα λ1215.6 line and of the O VI λλ1031.9, 1037.6 doublet, measured with the Ultraviolet Coronagraph Spectrometer (UVCS) on board the ESA-NASA solar spacecraft Solar and Heliospheric Observatory (SOHO) dur…
Photoelectric photometry of eclipsing contact binaries: U Peg, YY CrB, OU Ser and EQ Tau
Pribulla, T.; Vanko, M.
New photoelectric UBV observations of the eclipsing contact binary systems U Peg, YY CrB, OU Ser and EQ Tau obtained from August 2000 to October 2001 are presented and analyzed. The (O-C) diagram of U Peg indicates a decrease of the orbital period combined with a quasi-periodic variation. In the case of EQ Tau the long-term period changes can be i…
Strongly underwound magnetic fields in co-rotating rarefaction regions: Observations and Implications
Smith, E. J.; Schwadron, N. A.; Murphy, N.
Observations of the magnetic field orientation in co-rotating rarefaction regions (CRRs) reveals that the field can be significantly more radial than predicted by the Parker model. In particular, CRRs sampled by the Ulysses spacecraft beyond 4 AU from the sun often show average field orientations deviating by more than 30° from the expected Archim…
The Puzzle of the Polar Structure in NGC 4650A
Freeman, K. C.; De Lucia, G.; Gallagher, J. S., III +3 more
This work presents new surface photometry and two-dimensional modeling of the light distribution of the polar ring galaxy NGC 4650A, based on near-infrared (NIR) observations and high-resolution optical imaging acquired during the Hubble Heritage program. The NIR and optical integrated colors of the S0 galaxy and the polar ring and their scale par…
Analysis of the First Disk-resolved Images of Ceres from Ultraviolet Observations with the Hubble Space Telescope
Parker, Joel Wm.; Stern, S. Alan; Thomas, Peter C. +5 more
We present Hubble Space Telescope Faint Object Camera observations of the asteroid 1 Ceres at near-, mid-, and far-UV wavelengths (λ=3636, 2795, and 1621 Å, respectively) obtained on 1995 June 25. The disk of Ceres is well resolved for the first time, at a scale of ~50 km. We report the detection of a large, ~250 km diameter surface feature for wh…