Search Publications

M-Type Vega-like Stars

Zuckerman, B.; Song, Inseok; Becklin, E. E. +2 more

We carried out a search for M-type Vega-like stars by correlating the IRAS Faint Source Catalog with Hipparcos-selected M-type stars. Three stars with apparent IRAS 25 µm excess emission are shown instead to be non-IR-excess stars from ground-based 11.7 and 17.9 µm photometry. Two stars previously suggested to have Vega-like mid-IR exc…

2016+112: a gravitationally lensed type II quasar

Lawrence, C. R.; Blandford, R. D.; Koopmans, L. V. E. +3 more

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A single-screen model of the gravitational lens system 2016+112 is proposed, that explains recent Hubble Space Telescope (HST) infrared (NICMOS-F160W) observations and new high-resolution European VLBI Network (EVN) 5-GHz radio observations, presented in this paper. In particular, we find that a massive `dark' structure at the lens posit…

Subarcsecond Mid-Infrared Imaging of Two Post-Asymptotic Giant Branch 21 Micron Sources

Volk, Kevin; Kwok, Sun; Hrivnak, Bruce J.

High-resolution (FWHM 0.4") mid-infrared images have been obtained for two proto-planetary nebulae possessing the 21 µm emission feature (IRAS 07134+1005 and Z02229+6208). Images through five filters were obtained, covering the 11.3 and 21 µm emission features as well as the adjacent dust continuum. The images of IRAS 07134+1005 show a…

Possible Recovery of SN 1961V in Hubble Space Telescope Archival Images

Van Dyk, Schuyler D.; Filippenko, Alexei V.; Li, Weidong

SN 1961V in NGC 1058 was originally classified by Fritz Zwicky as a ``Type V'' supernova. However, it has been argued that SN 1961V was not a genuine supernova, but instead the superoutburst of an η Carinae-like luminous blue variable star. In particular, Filippenko et al. used pre-refurbishment Hubble Space Telescope (HST) Wide Field Planetary Ca…

The Effects of Dust in Simple Environments: Large Magellanic Cloud H II Regions

Bell, Eric F.; Gordon, Karl D.; Zaritsky, Dennis +1 more

We investigate the effects of dust on Large Magellanic Cloud (LMC) H II region spectral energy distributions using arcminute-resolution far-ultraviolet (FUV), Hα, far-infrared (FIR), and radio images. Widely used indicators of the amount of light lost to dust (attenuation) at Hα and in the FUV correlate with each other, although often with substan…

The Spectral Energy Distribution and Mass-Loss Rate of the A-Type Supergiant Deneb

Howarth, I. D.; Hauschildt, P. H.; Baron, E. +5 more

A stellar wind module has been developed for the PHOENIX stellar atmosphere code for the purpose of computing non-LTE, line-blanketed, expanding atmospheric structures and detailed synthetic spectra of hot luminous stars with winds. We apply the code to observations of Deneb, for which we report the first positive detections of millimeter and cent…

Uncertainties in Dielectronic Recombination Rate Coefficients: Effects on Solar and Stellar Upper Atmosphere Abundance Determinations

Laming, J. Martin; Savin, Daniel Wolf

We have investigated how the relative elemental abundances inferred from the solar upper atmosphere are affected by uncertainties in the dielectronic recombination (DR) rate coefficients used to analyze the spectra. We find that the inferred relative abundances can be up to a factor of ~5 smaller or ~1.6 larger than those inferred using the curren…

Large-Scale Solar Coronal Structures in Soft X-Rays and Their Relationship to the Magnetic Flux

Kosovichev, A. G.; Benevolenskaya, E. E.; Scherrer, P. H. +2 more

We have investigated the relationship between magnetic activity and coronal structures using soft X-ray data from the Yohkoh soft X-ray telescope and magnetic field data from the Kitt Peak Solar Observatory for the period of 1991-2001 and EUV data from the Solar and Heliospheric Observatory EUV Imaging Telescope for 1996-2001. The data are reduced…

Young massive stars in the ISOGAL survey. II. The catalogue of bright YSO candidates

Felli, M.; Omont, A.; Testi, L. +1 more

The 7 and 15 mu m observations of selected fields in the Galactic Plane obtained with ISOCAM during the ISOGAL program offer a unique possibility to search for previously unknown YSOs, undetected by IRAS because of lower sensitivity or confusion problems. In a previous paper (Felli et al. \cite{FCTOS00}) we established criteria of general validity…

Kinematical Structure of Wolf-Rayet Winds. I.Terminal Wind Velocity

Niedzielski, A.; Skorzynski, W.

New terminal wind velocities for 164 Wolf-Rayet stars (from the Galaxy and LMC) based on PCyg profiles of lambda1550 CIV resonance line were derived from the archive high and low resolution IUE spectra available form the INES database. The high resolution data on 59 WR stars (39 from the Galaxy and 20 from LMC) were used to calibrate the empirical…