Search Publications
Resolved Spectroscopy of the Narrow-Line Region in NGC 1068. I. The Nature of the Continuum Emission
Crenshaw, D. Michael; Kraemer, Steven B.
We present the first long-slit spectra of the Seyfert 2 galaxy NGC 1068 obtained by the Space Telescope Imaging Spectrograph (STIS) the spectra cover the wavelength range 1150-10270 Å at a spatial resolution of 0.05"-0.1" and a spectral resolving power of λ/Δλ~1000. In this first paper, we concentrate on the far-UV to near-IR continuum emission fr…
Recent Changes in the Near-Infrared Structure of η Carinae
Smith, Nathan; Gehrz, Robert D.
Near-infrared imaging at two phases in the 5 yr spectroscopic cycle of η Carinae reveals changes in the spatial structure of the inner core that may be related to recently reported near-infrared photometric variability. The central source changed from a pointlike object to a more extended, bipolar or shell structure. This behavior is reminiscent o…
Magnetic Activity Associated With Radio Noise Storms
van Driel-Gesztelyi, L.; Bentley, R. D.; Klein, K. -L. +4 more
As it crossed the solar disk in May and June 1998, AR 8227 was tracked by TRACE, Yohkoh, SOHO, and many ground-based observatories. We have studied how the evolution of the magnetic field resulted in changes in activity in the corona. In particular, we examine how the evolving field may have led to the acceleration of electrons which emit noise st…
The multiple system LHS 1070: a case study for the onset of dust formation in the atmospheres of very low mass stars
Hauschildt, Peter H.; Richichi, Andrea; Leinert, Christoph +1 more
Atomic data from the IRON Project. XL. Electron impact excitation of the Fe XIV EUV transitions
Young, P. R.; Mason, H. E.; Storey, P. J.
We calculate collision strengths and thermally averaged collision strengths for electron excitation between the forty energetically lowest levels of Fe13+. The scattering calculation is more complete than any previous work on this ion and significant differences are found in the excitation rates for many of the extreme ultra-violet (EUV…
Modelling solar irradiance variations: Comparison with observations, including line-ratio variations
Solanki, S. K.; Unruh, Y. C.; Fligge, M.
Solar irradiance variations show a strong temporal and spectral dependence. The progression of the Sun through its activity cycle as well as solar rotation are mirrored in the irradiance variations. The spectral dependence is such that the variations are several magnitudes larger in the EUV than in the visible or infrared. We present a simple 3-co…
HST ultraviolet observations of rapid variability in the accretion-disc wind of BZ Cam
Ringwald, F. A.; Prinja, Raman K.; Knigge, Christian +1 more
We present results from time-resolved Hubble Space Telescope (HST) GHRS ultraviolet spectroscopy of the nova-like cataclysmic variable BZ Cam. Extensive changes are recorded in the extended absorption troughs of the UV resonance line profiles, which betray a highly unsteady and continuously variable supersonic outflow. The large-scale line-profile…
Multi-wavelength study of the slow ``disparition brusque" of a filament observed with SOHO
Schmieder, B.; Delannée, C.; Yong, Deng Yuan +2 more
A mid-latitude filament was observed before and after its eruption with SOHO (EIT, SUMER, CDS and LASCO) and with ground based observatories (Meudon and Pic du Midi) in the context of a coordinated MEDOC campaign in Orsay. The eruption was followed by a large Coronal Mass Ejection well observed by LASCO. Few hours before its eruption, the filament…
Highly polarized structures in the near-nuclear regions of Cygnus A: intrinsic anisotropy within the cones?
Tadhunter, C. N.; Packham, C.; Sparks, W. +6 more
We present near-infrared imaging polarimetry observations of the nucleus of Cygnus A (z= 0.0567), taken with the NICMOS camera of the Hubble Space Telescope (HST) at a wavelength of 2.0µm. These maps reveal a highly collimated region of polarized emission straddling the nucleus and extending to a radius of 1.2arcsec. Remarkably, this feature…
Radio Tracking of a White-Light Coronal Mass Ejection from Solar Corona to Interplanetary Medium
Plunkett, S. P.; Kaiser, M. L.; Reiner, M. J. +2 more
For a solar flare/coronal mass ejection (CME) event on 1999 May 3, type II radio emissions were observed from the metric through the hectometric wavelength regimes. By comparing the dynamics of the CME with that implied by the frequency range and frequency drift rates of the type II radio emissions, it is concluded that the decametric-hectometric …