Search Publications
Template Ultraviolet to Near-Infrared Spectra of Star-forming Galaxies and Their Application to K-Corrections
Calzetti, Daniela; Storchi-Bergmann, Thaisa; Bohlin, Ralph C. +3 more
Template UV-optical spectra of quiescent and starburst galaxies are presented and used to derive K-corrections as a function of morphological type and redshift. IUE observations and archival data are used for the UV template spectra. The optical spectra are from ground-based observations obtained in apertures that match closely the 200 arcsec^2^ I…
Multiwavelength Observations of Short-Timescale Variability in NGC 4151. IV. Analysis of Multiwavelength Continuum Variability
Shull, J. M.; Glass, I. S.; Malkan, M. A. +88 more
This paper combines data from the three preceding papers in order to analyze the multi-wave-band variability and spectral energy distribution of the Seyfert I galaxy NGC 4151 during the 1993 December monitoring campaign. The source, which was near its peak historical brightness, showed strong, correlated variability at X-ray, ultraviolet, and opti…
Projected Rotational Velocities of O-Type Stars
Penny, Laura R.
I present an homogeneous set of projected rotational velocities for 177 O stars based upon lUE high- dispersion spectra of the UV photo spheric lines. The line widths are estimated by cross-correlating each spectrum with the spectrum of a narrow-lined O star (HD 34078), and the widths of the cross-correlation functions are transformed to projected…
The Gas and Dust Abundances of Diffuse Halo Clouds in the Milky Way
Sembach, Kenneth R.; Savage, Blair D.
We present Goddard High-Resolution Spectrograph observations of the interstellar Mg II, Si II, P II, S II, Mn II, Cr II, Fe II, Ni II, Zn II, and Ge II lines toward HD 116852, a star at -1.3 kpc from the Galactic plane and a distance of 4.8 kpc in the direction l = 304°.9, b = -16°.1. The intermediate-resolution (FWHM ≈ 11-18 km s-1) ob…
New Insights into the Physical Nature of LINERs from a Multiwavelength Analysis of the Nucleus of M81
Filippenko, Alexei V.; Ho, Luis C.; Sargent, Wallace L. W.
We discuss the physical conditions and excitation of the nucleus of M81 by combining ground-based optical spectra, archival Hubble Space Telescope (HST) Ultraviolet (UV) and optical spectral, and published X- ray measurements. This well known low-ionization nuclear emission-line region (LINER) is representative of a general class of objects though…
Simultaneous Multiwavelength Spectrum and Variability of 3C 279 from 10 9 to 10 24 Hz
Dermer, C. D.; Tornikoski, M.; Hermsen, W. +25 more
Data from a number of monitoring programs have been combined with data from the Compton Gamma Ray Observatory and the Ginga X-ray satellite to construct a spectrum covering nearly 15 decades in frequency during or near the time of the 3C 279 γ-ray flare observed by EGRET in 1991 June. A much less complete spectrum is presented for 1991 October. Li…
Reverberation Mapping and the Disk-Wind Model of the Broad-Line Region
Chiang, J.; Murray, N.
Using the disk-wind model of Murray et al., we calculate line profiles and frequency-resolved response functions for broad-line emission from the surface of an accretion disk in an active galactic nucleus in the presence of a radiatively driven wind. We find that the combined effects of the shears in the wind and in the dIsk itself produce anisotr…
Obscuration of LY alpha Photons in Star-forming Galaxies
Giavalisco, Mauro; Calzetti, Daniela; Koratkar, Anuradha
We present a new study of the correlations between the Lyα emission, the UV extinction, and the metal content in a sample of 21 local, low-metallicity starburst galaxies from archival IUE spectra. We have consistently reextracted all the spectra using the optimal extraction algorithm by Kinney and coworkers, and we have also included galaxies not …
The Variability of Quasars. II. Frequency Dependence
Giallongo, E.; Trevese, D.; Vagnetti, F. +2 more
The variability of 30 PG quasars has been observed in the red band during 3 years. A rest-frame structure function analysis shows an increase of variability with the time interval up to 0.2 mag rms after 2 years. A comparison with the IUE data available for PG quasars shows that the variability increases with the rest-frame frequency at each time …
On the Balmer Line Problem
Werner, K.
The so-called Balmer line problem describes the failure to achieve a consistent fit to the Balmer line spectrum of any hot sdO star whose effective temperature exceeds ~70,000 K. Results of Teff determinations drastically deviate, up to a factor of 2, depending on which Balmer line is examined. This problem was uncovered a few years ago during non…