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First Results from VIRGO, the Experiment for Helioseismology and Solar Irradiance Monitoring on SOHO
Gough, Douglas; Domingo, Vicente; Appourchaux, Thierry +19 more
First results from the VIRGO experiment (Variability of solar IRradiance and Gravity Oscillations) on the ESA/NASA Mission SOHO (Solar and Heliospheric Observatory) are reported. The observations started mid-January 1996 for the radiometers and sunphotometers and near the end of March for the luminosity oscillation imager. The performance of all t…
Line-blanketed model atmospheres for R Coronae Borealis stars and hydrogen-deficient carbon stars.
Eriksson, K.; Gustafsson, B.; Asplund, M. +1 more
We have constructed line-blanketed model atmospheres for the hydrogen-deficient and carbon-rich R Coronae Borealis (RCrB) stars, as well as for the similar hydrogen-deficient carbon (HdC) stars and the cool extreme helium (EHe) stars. Improved continuum opacities have been used together with realistic line absorption data for atomic and molecular …
First Results of the SUMER Telescope and Spectrometer on SOHO - II. Imagery and Data Management
Grewing, M.; Wilhelm, K.; Marsch, E. +13 more
SUMER - Solar Ultraviolet Measurements of Emitted Radiation - is not only an extreme ultraviolet (EUV) spectrometer capable of obtaining detailed spectra in the range from 500 to 1610 Å, but, using the telescope mechanisms, it also provides monochromatic images over the full solar disk and beyond, into the corona, with high spatial resolution. We …
Synthetic Spectra of Hydrodynamic Models of Type Ia Supernovae
Baron, E.; Branch, David; Hauschildt, Peter H. +2 more
We present detailed non-LTE synthetic spectra of hydrodynamic supernovae (SNe) Ia models. We make no assumptions about the form of the spectrum at the inner boundary. We calculate both Chandrasekhar-mass deflagration models and sub-Chandrasekhar ``helium detonators.'' Gamma-ray deposition is handled in a simple, accurate manner. We have parameteri…
HIPPARCOS data on Herbig Ae/Be stars: an evolutionary scenario.
Waters, L. B. F. M.; Catala, C.; The, P. S. +4 more
Fundamental astrophysical parameters (distance, temperature, luminosity, mass, age) of a sample of 10 Herbig Ae/Be candidates and 3 non-emission line A and B stars in star forming regions were computed combining Hipparcos parallaxes with data from literature. All genuine Herbig stars in our sample are located between the birthline and the zero-age…
M Dwarfs from Hubble Space Telescope Star Counts. III. The Groth Strip
Gould, Andrew; Bahcall, John N.; Flynn, Chris
We analyze the disk M dwarfs found in 31 new fields observed with the Wide Field Camera 2 (WFC2) on the Hubble Space Telescope, together with the sample previously analyzed from 22 WFC2 fields and 162 prerepair Planetary Camera 1 fields. The new observations, which include the 28 high-latitude fields comprising the Large Area Multi-Color Survey (G…
The Star Cluster System of the Merger Remnant NGC 7252
Whitmore, Bradley C.; Fall, S. Michael; Miller, Bryan W. +1 more
We present new U, B, V, and I images of the prototypical merger remnant NGC 7252 obtained with the WFPC2 instrument of the Hubble Space Telescope. The photometry reaches about 3 mag deeper than the previous observations with WF/PC1 and we detect 499 cluster candidates, most of them previously undiscovered. We can distinguish three populations of s…
Spiral Galaxies with WFPC2.I.Nuclear Morphology, Bulges, Star Clusters, and Surface Brightness Profiles
Carollo, C. M.; Stiavelli, M.; de Zeeuw, P. T. +1 more
We report the analysis of HST WFPC2 F606W images of a sample of 35 spiral galaxies. We describe the optical morphological properties of the galaxies on scales of a few tens of parsecs, derive the surface brightness profiles for 18 of them, and present the results of analytical fits to these profiles. We find that: (I) Several galaxies, despite the…
Triggered Star Formation in a Massive Galaxy at z = 3.8: 4C 41.17
Dey, Arjun; Vacca, William D.; van Breugel, Wil +1 more
We present deep spectropolarimetric observations obtained with the W. M. Keck Telescope of the very high redshift (z = 3.79786 +/- 0.0024) radio galaxy 4C 41.17. We find that the bright, spatially extended rest-frame UV continuum emission from this galaxy, which is aligned with the radio axis, is unpolarized (P2σ < 2.4%). This implie…
Ultraviolet Coronagraph Spectrometer Observations of Density Fluctuations in the Solar Wind
Romoli, M.; Poletto, G.; Noci, G. +2 more
Recent Ultraviolet Coronagraph Spectrometer (UVCS) white-light channel (WLC) observations on board the Solar and Heliospheric Observatory (SOHO) indicate quasi-periodic variations in the polarized brightness (pB) in the polar coronal holes. This is the first observation of possible signatures of compressional waves high above the limb (at heliocen…