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Possible High-Redshift, Low-Luminosity Active Galactic Nuclei in the Hubble Deep Field
MacAlpine, Gordon M.; Jarvis, R. Michael
In the Hubble Deep Field (HDF), 12 candidate sources of high-redshift (z > 3.5) active galactic nuclei (AGN) have been identified. The color selection criteria were established by passing spectra of selected quasars and Seyfert galaxies (appropriately redshifted and modified for ``Lyman forest'' absorption), as well as stars, observed normal an…
Observations of QSO J2233-606 in the Southern Hubble Deep Field
Webb, J. K.; Drinkwater, M. J.; Sealey, K. M.
The Hubble Deep Field South (HDF-S) Hubble Space Telescope (HST) observations are expected to begin in 1998 October. We present a composite spectrum of the QSO in the HDF-S field covering UV/optical/near-IR wavelengths, obtained by combining data from the Australian National University 2.3 m telescope with STIS on the HST.1 This intermediate-resol…
ISOCAM Molecular Hydrogen Images of the Cepheus E Outflow
Garnavich, Peter M.; Molinari, Sergio; Noriega-Crespo, Alberto
The physical characteristics of the Cepheus E ``embedded'' outflow are analyzed using ISOCAM images in the v = 0-0 S(5) 6.91 µm and S(3) 9.66 µm molecular hydrogen lines. We find that the morphology of the Cep E outflow in the ground vibrational H_2 lines is similar to that in the near-infrared v = 1-0 2.12 µm line. At these mid-…
Morphological Changes, Evidence for a Collimating Disk, and Extremely Young Jetlike Components in the Planetary Nebula IC 4997
Miranda, Luis F.; Torrelles, José M.
We present VLA-A radio continuum observations at 3.6 cm and 2 cm of the extremely young, double-shell planetary nebula IC 4997. A comparison of the new 3.6 cm map with that obtained in 1995 July shows that morphological changes have occurred in the nebula in ~=1.3 yr. These changes reveal themselves by the presence in the outer shell of several ne…
New Light Synthesis and Spectrum Synthesis Constraints on a Model for β Lyrae
Harmanec, P.; Hubeny, I.; Linnell, A. P.
A suite of programs that calculates both synthetic light curves and synthetic spectra for a binary system with an optically thick accretion disk has been applied for the first time to β Lyrae A. Our results demonstrate that the standard accretion disk model by Hubeny & Plavec shows significant residuals from observations, both photometric and …
Carbon and Oxygen Depletion and Extinction in the Translucent Cloud toward HD 24534 (X Persei)
Snow, Theodore P.; van Dishoeck, Ewine F.; Black, John H. +3 more
Recent studies of the gas-phase abundances of carbon and oxygen in diffuse clouds have suggested that the depletions of both elements are invariant and independent of extinction curve properties. We show, however, that in the line of sight toward HD 24534 (X Persei), the depletion of carbon is at least a factor of 3 greater than in the diffuse clo…
A test of B-type star Hβ photometric distances via the HIPPARCOS parallaxes
Knude, J.; Kaltcheva, N.
We test the photometric uvbybeta distances for B III, IV and V type stars, with an emphasis on the effect of rotation on the M_V determination. From the M_V(uvbybeta ) calibration of Balona & Shobbrook (1984), we have derived the absolute visual magnitudes for 176 stars with v sin (i) measurements and have compared them to M_V values derived v…
Mid-Infrared Emission Features in the Interstellar Medium: Feature-to-Feature Flux Ratios
Lu, Nanyao Y.
Using a limited but representative sample of sources in the interstellar medium of our Galaxy with published spectra from the Infrared Space Observatory, we analyze the flux ratios between the major mid-IR emission features (EFs) centered around 6.2, 7.7, 8.6, and 11.3 µm, respectively. In a flux ratio-to-flux ratio plot of EF(6.2 µm)/…
A Statistical Treatment of the Gamma-Ray Burst ``No Host Galaxy'' Problem. I. Methodology
Hartmann, Dieter H.; Band, David L.
If gamma-ray bursts originate in galaxies at cosmological distances, the host galaxy should be detected if a burst error box is searched deeply enough; are the host galaxies present? We present and implement a statistical methodology that evaluates whether the observed galaxy detections in a burst's error box are consistent with the presence of th…
CCD photometry of variable stars in the Magellanic Clouds - V. The eclipsing binaries HV1620 and HV2241
Guinan, E. F.; Pritchard, J. D.; Tobin, W. +1 more
Using improved techniques, high-quality CCD uvbyVI_C photometry has been obtained for the 14th magnitude eclipsing binaries HV1620 in the Small Magellanic Cloud (SMC) and HV2241 in the Large Magellanic Cloud (LMC). IUE ultraviolet spectrophotometry was also obtained. These data have been analysed using the Wilson & Devinney synthetic light-cur…