Search Publications
Determining Central Black Hole Masses in Distant Active Galaxies and Quasars. II. Improved Optical and UV Scaling Relationships
Peterson, Bradley M.; Vestergaard, Marianne
We present four improved empirical relationships useful for estimating the central black hole mass in nearby AGNs and distant luminous quasars alike using either optical or UV single-epoch spectroscopy. These mass scaling relationships between line widths and luminosity are based on recently improved empirical relationships between the broad-line …
Damped Lyα Systems at z<1.65: The Expanded Sloan Digital Sky Survey Hubble Space Telescope Sample
Turnshek, David A.; Rao, Sandhya M.; Nestor, Daniel B.
We present results of our Hubble Space Telescope Cycle 11 survey for low-redshift (z<1.65) damped Lyα (DLA) systems in the UV spectra of quasars selected from the Sloan Digital Sky Survey (SDSS) Early Data Release. These quasars have strong intervening Mg II-Fe II systems that are known signatures of high column density neutral gas. In total, i…
Formation and Evolution of Planetary Systems: Upper Limits to the Gas Mass in Disks around Sun-like Stars
Wolf, S.; Pascucci, I.; Carpenter, J. M. +17 more
We have carried out a sensitive search for gas emission lines at IR and millimeter wavelengths for a sample of 15 young Sun-like stars selected from our dust disk survey with Spitzer. We have used mid-IR lines to trace the warm (300-100 K) gas in the inner disk and millimeter transitions of 12CO to probe the cold (~20 K) outer disk. We …
The Mass of the Central Black Hole in the Seyfert Galaxy NGC 4151
Peterson, Bradley M.; Onken, Christopher A.; Metzroth, Kyle G.
In order to improve the reverberation-mapping-based estimate of the mass of the central supermassive black hole in the Seyfert 1 galaxy NGC 4151, we have reanalyzed archival ultraviolet monitoring spectra from two campaigns undertaken with the International Ultraviolet Explorer. We measure emission-line time delays for four lines, C IV λ1549, He I…
C II Abundances in Early-Type Stars: Solution to a Notorious Non-LTE Problem
Przybilla, N.; Nieva, M. F.
We address a long-standing discrepancy between non-LTE analyses of the prominent C II 4267 and 6578/82 Å multiplets in early-type stars. A comprehensive non-LTE model atom of C II is constructed based on critically selected atomic data. This model atom is used for an abundance study of six apparently slow-rotating main-sequence and giant early B-t…
Ultraviolet-to-Far-Infrared Properties of Local Star-forming Galaxies
Giavalisco, M.; Leitherer, C.; Armus, L. +5 more
We present the results of a multiwavelength study of nearby galaxies aimed at understanding the relation between the ultraviolet and far-infrared emission in star-forming galaxies. The data set comprises new ultraviolet (from HST STIS), ground-based Hα, and radio continuum observations, together with archival infrared data (from IRAS and ISO). The…
Binary and Multiple O-Type Stars in the Cassiopeia OB6 Association
Gies, Douglas R.; Bagnuolo, William G., Jr.; McSwain, M. Virginia +3 more
We present the results of time-resolved spectroscopy of 13 O-type stars in the Cas OB6 stellar association. We conducted a survey for radial velocity variability in search of binary systems, which are expected to be plentiful in young OB associations. Here we report the discovery of two new single-lined binaries, and we present new orbital element…
An Ultraviolet to Mid-Infrared Study of the Physical and Wind Properties of HD 164270 (WC9) and Comparison to BD +30 3639 ([WC9])
Smith, J. D.; Morris, P. W.; Crowther, Paul A.
We present new Spitzer IRS observations of HD 164270 (WC9, WR103). A quantitative analysis of the UV, optical, near-, and mid-IR spectra of HD 164270 is presented, allowing for line blanketing and wind clumping, revealing T*~48 kK, logL/Lsolar~4.9, and M˙~10-5 Msolar yr-1 for a volume filling …
The Dwarf Novae during Quiescence
Sion, Edward M.; Urban, Joel A.
We present a synthetic spectral analysis of nearly the entire far-ultraviolet (FUV) IUE archive of spectra of dwarf novae (DNe) in or near their quiescence. We have examined all of the systems for which the signal-to-noise ratio permitted an analysis. The study includes 53 systems of all DN subtypes both above and below the period gap. The spectra…
Hubble Space Telescope STIS Spectroscopy and Modeling of the Long-Term Cooling of WZ Sagittae following the 2001 July Outburst
Szkody, Paula; Sion, Edward M.; Godon, Patrick +3 more
We present the latest Hubble Space Telescope Space Telescope Imaging Spectrograph (HST STIS) E140M far-ultraviolet (FUV) spectrum of the dwarf nova WZ Sge, obtained in 2004 July, 3 yr following the early superoutburst of 2001 July. With a temperature T~15,000 K, the white dwarf (WD) is still ~1500 K above its quiescent temperature, it has a FUV fl…