Search Publications
The Three-dimensional Structure of the Warm Local Interstellar Medium. II. The Colorado Model of the Local Interstellar Cloud
Redfield, Seth; Linsky, Jeffrey L.
In this second paper in a series on the structure of the local interstellar medium (LISM), we construct a three-dimensional model of the local interstellar cloud (LIC) based on Hubble Space Telescope (HST), Extreme Ultraviolet Explorer (EUVE), and ground-based Ca II spectra. Starting with hydrogen column densities derived from deuterium column den…
Membership and Multiplicity among Very Low Mass Stars and Brown Dwarfs in the Pleiades Cluster
Zapatero Osorio, M. R.; Luhman, K. L.; Martín, E. L. +5 more
We present near-infrared photometry and optical spectroscopy of very low mass stars and brown dwarf candidates in the Pleiades open cluster. The membership status of these objects is assessed using color-magnitude diagrams, lithium and spectral types. Eight objects out of 45 appear to be nonmembers. A search for companions among 34 very low mass P…
Chandra Observations of the X-Ray Narrow-Line Region in NGC 4151
Marshall, H. L.; Lee, J. C.; Ogle, P. M. +1 more
We present the first high-resolution X-ray spectrum of the Seyfert 1.5 galaxy NGC 4151. Observations with the Chandra High-Energy Transmission Grating Spectrometer reveal a spectrum dominated by narrow emission lines from a spatially resolved (1.6 kpc), highly ionized nebula. The X-ray narrow-line region is composite, consisting of both photoioniz…
How Much Do Helioseismological Inferences Depend on the Assumed Reference Model?
Basu, Sarbani; Pinsonneault, M. H.; Bahcall, John N.
We investigate systematic uncertainties in determining the profiles of the solar sound speed, density, and adiabatic index using helioseismological techniques. We find that rms uncertainties (averaged over the Sun) of ~0.02%-0.04% are contributed to the sound-speed profile by each of three sources: (1) the choice of assumed reference model, (2) th…
A Candidate Substellar Companion to HR 7329
Weinberger, Alycia J.; Schneider, Glenn; Hines, Dean C. +10 more
We present the discovery of a candidate substellar companion from a survey of nearby young stars made with the Near-Infrared Camera and Multiobject Spectrometer coronagraph on the Hubble Space Telescope. The H~12 mag object was discovered approximately 4" from the young A0 V star HR 7329. Using follow-up spectroscopy from the Space Telescope Imagi…
An Excess of Submillimeter Sources near 4C 41.17: A Candidate Protocluster at Z = 3.8?
Ivison, R. J.; Smail, Ian; Dunlop, J. S. +3 more
Biased galaxy-formation theories predict that massive galaxies at high redshifts should act as signposts to high-density environments in the early universe, which subsequently evolve into the cores of the richest clusters seen at the present day. These regions are characterized by overdensities of young galaxies, perhaps including a population of …
STIS Coronagraphic Imaging of the Herbig AE Star: HD 163296
Kimble, R.; Linsky, J. L.; Bruhweiler, F. C. +7 more
Coronagraphic imaging with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope reveals a ~450 AU radius circumstellar disk around the Herbig Ae star HD 163296. A broadband (0.2-1.0 µm) reflected light image shows the disk oriented at a position angle of 140deg+/-5deg and inclined to our line of …
The Mid-Infrared Spectra of Normal Galaxies
Helou, G.; Malhotra, S.; Werner, M. W. +2 more
The mid-infrared spectra (2.5-5 and 5.7-11.6 µm) obtained by ISOPHOT reveal the interstellar medium emission from galaxies powered by star formation to be strongly dominated by the aromatic features at 6.2, 7.7, 8.6, and 11.3 µm. Additional emission appears in between the features, and an underlying continuum is clearly evident at 3-5 …
Hubble Space Telescope Observations of Oxygen-rich Supernova Remnants in the Magellanic Clouds. II. Elemental Abundances in N132D and 1E 0102.2-7219
Blair, William P.; Kirshner, Robert P.; Hughes, John P. +6 more
We present Hubble Space Telescope (HST) Wide Field and Planetary Camera 2 images and Faint Object Spectrograph data of two young supernova remnants in the Magellanic Clouds, N132D (LMC) and 1E 0102.2-7219 (SMC). The spectra cover essentially the entire UV/optical range available to HST and provide the first true comparison of UV/optical line inten…
The η Chamaeleontis Cluster: Origin in the Sco-Cen OB Association
Feigelson, Eric D.; Mamajek, Eric E.; Lawson, Warrick A.
A young, nearby compact aggregate of X-ray-emitting pre-main-sequence stars was recently discovered in the vicinity of η Chamaeleontis. In this paper, we further investigate this cluster: its membership, its environs, and its origins. ROSAT High Resolution Imager X-ray data for the cluster's T Tauri stars show high levels of magnetic activity and …