Search Publications
The Surprising Emission Distribution within the Helix Nebula Cometary Knots
O'Dell, C. R.; Henney, W. J.; Burkert, A.
We compare the morphology of the cometary knots in the Helix Nebula in different emission lines using Hubble Space Telescope Wide Field Planetary Camera 2 and Space Telescope Imaging Spectrograph observations. We find that the [N II] 6658 Å line emission from the cometary heads is displaced with respect to Hα, peaking at a position that is closer …
Hubble Space Telescope Infrared Imaging Polarimetry of Centaurus A: Implications for the Unified Scheme and the Existence of a Misdirected BL Lacertae Nucleus
Marconi, Alessandro; Capetti, Alessandro; Hough, J. H. +6 more
We report results from the Hubble Space Telescope (HST)/near-infrared camera and multiobject spectrometer (NICMOS) 2 µm imaging polarimetry of the central region of Centaurus A. In the vicinity of the nucleus we observe a complex polarization structure, which we explain by a combination of scattering of nuclear light and dichroic polarizatio…
Far-infrared photometry and mapping of Herbig Ae/Be stars with ISO
Burkert, A.; Ábrahám, P.; Henning, Th. +2 more
Seven Herbig Ae/Be stars were observed at mid- and far-infrared wavelengths with ISOPHOT, the photometer on-board the Infrared Space Observatory. At λ{<=}25µm, where the emission mainly arises from a compact circumstellar region, the observed spectral energy distributions can be described by power-law relationships between wavelength and …
Distance Dependence in the Solar Neighborhood Age-Metallicity Relation
Garnett, D. R.; Kobulnicky, H. A.
The age-metallicity relation for F and G dwarf stars in the solar neighborhood, based on the stellar metallicity data of Edvardsson et al., shows an apparent scatter that is larger than expected considering the uncertainties in metallicities and ages. A number of theoretical models have been put forward to explain the large scatter. However, we pr…
A young stellar group associated with HD 199143 (d=48 pc)
McCollum, B.; de Winter, D.; van den Ancker, M. E. +1 more
We present new optical and ultraviolet spectroscopy of the anomalous EUV emitter HD 199143 (F8V). High resolution spectra in the Halpha and Na I D wavelength regions show evidence for very rapid (a few hundred km/s) rotation of the stellar photosphere. Using archive IRAS data we also show that the star has excess emission above photospheric levels…
ISOPHOT Serendipity Survey observations of interstellar clouds I. Detection of the Coldest Cores in Chamaeleon
Krause, O.; Lemke, D.; Laureijs, R. J. +5 more
ISOPHOT Serendipity Survey (ISOSS) observations at 170 \um\ reveal cold dust clouds in the nearby star forming region Chamaeleon. The distribution of the ISOSS/IRAS based T(I170/I100) colour temperature have been studied in a nearby low-mass star forming region. T(I170/I100) separates the obscured and in…
The Nature of Solar Polar Rays
Jewitt, David; Li, Jing; LaBonte, Barry
We use time series observations from the Solar and Heliospheric Observatory and Yohkoh spacecraft to study solar polar rays. Contrary to our expectations, we find that the rays are associated with active regions on the Sun and are not features of the polar coronal holes. They are extended, hot plasma structures formed in the active regions and pro…
Evolution of Global-Scale Coronal Magnetic Field due to Magnetic Reconnection: The Formation of the Observed Blob Motion in the Coronal Streamer Belt
Plunkett, S. P.; Michels, D. J.; Wu, S. T. +1 more
Recent SOHO/LASCO/EIT observations showed that the global corona at the minimum phase of cycle 22 is an organized, simple, and persistent dipolar configuration streamer belt (Michels). But the low-lying, closed-loop, multipolar magnetic structure of the inner corona at low- to mid-latitudes revealed in EIT and LASCO images is not static. It stretc…
Vertical Distribution of PH 3 in Saturn from Observations of Its 1-0 and 3-2 Rotational Lines
Orton, Glenn S.; Serabyn, E.; Lee, Y. T.
Far-infrared Fourier-transform spectrometer measurements of the 1-0 and 3-2 PH 3 transitions in Saturn's disk near 267 and 800 GHz (8.9 and 26.7 cm -1), respectively, were analyzed simultaneously to derive a global mean profile for the PH 3 vertical mixing ratio between 100 and 600 mbar total pressure. The far-infr…
Small Scale Structure in the Solar Transition Region
Winebarger, Amy R.; Warren, Harry P.
We present analysis of a high spatial resolution (~1.5") O VI λ1032 spectroheliogram taken with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on the Solar and Heliospheric Observatory. This image shows numerous narrow, looplike structures. The widths of the narrowest resolved features are at the spatial resolution of…