Search Publications
Spectral Irradiance Calibration in the Infrared. X. A Self-Consistent Radiometric All-Sky Network of Absolutely Calibrated Stellar Spectra
Noguchi, Kunio; Cohen, Martin; Walker, Russell G. +3 more
We start from our six absolutely calibrated continuous stellar spectra from 1.2 to 35 µm for K0, K1.5, K3, K5, and M0 giants. These were constructed as far as possible from actual observed spectral fragments taken from the ground, the Kuiper Airborne Observatory, and the IRAS Low Resolution Spectrometer, and all have a common calibration ped…
A giant periodic flare from the soft γ-ray repeater SGR1900+14
Cline, T.; Hurley, K.; Golenetskii, S. +11 more
Soft γ-ray repeaters are transient sources of high-energy photons; they emit sporadic and short (about 0.1s) bursts of `soft' γ-rays during periods of activity, which are often broken by long stretches of quiescence. These objects are associated with neutron stars in young supernova remnants. The event of 5 March 1979 was the most intense burst to…
Hubble Space Telescope/NICMOS Observations of Massive Stellar Clusters near the Galactic Center
Rich, R. Michael; Serabyn, Eugene; Figer, Donald F. +3 more
We report Hubble Space Telescope (HST) Near-Infrared Camera and Multiobject Spectrometer (NICMOS) observations of the Arches and Quintuplet clusters, two extraordinary young clusters near the Galactic center. For the first time, we have identified main-sequence stars in the Galactic center with initial masses well below 10 Msolar. We pr…
The Spectral Energy Distributions of Low-Luminosity Active Galactic Nuclei
Ho, Luis C.
As a step toward elucidating the physical conditions in nearby active galaxies, this paper presents spectral energy distributions (SEDs) of a sample of seven low-luminosity active galactic nuclei (AGNs). SEDs for four objects are presented for the first time (NGC 4261, NGC 4579, NGC 6251, and M84); the data for the remaining three (M81, M87, and N…
A New Catalog of Photometric Redshifts in the Hubble Deep Field
Lanzetta, Kenneth M.; Yahil, Amos; Fernández-Soto, Alberto
Using the newly available infrared images of the Hubble Deep Field in the J, H, and K bands and an optimal photometric method, we have refined a technique to estimate the redshifts of 1067 galaxies. A detailed comparison of our results with the spectroscopic redshifts in those cases where the latter are available shows that this technique gives ve…
Hubble Space Telescope Observations of Superluminal Motion in the M87 Jet
Sparks, W. B.; Macchetto, F.; Biretta, J. A.
We present observations of the M87 jet made with the Faint Object Camera on board the Hubble Space Telescope at five epochs between 1994 and 1998. These observations reveal 10 superluminal features within the first 6" of the jet, with eight of these having apparent speeds in the range 4c-6c. Two additional features within the first arcsecond of th…
Keplerian Motion of Broad-Line Region Gas as Evidence for Supermassive Black Holes in Active Galactic Nuclei
Peterson, Bradley M.; Wandel, Amri
Emission-line variability data on NGC 5548 argue strongly for the existence of a mass of order 7×107 Msolar within the inner few light-days of the nucleus in the Seyfert 1 galaxy NGC 5548. The time-delayed response of the emission lines to continuum variations is used to infer the size of the line-emitting region, and these d…
The Mass Function of Young Star Clusters in the ``Antennae'' Galaxies
Fall, S. Michael; Zhang, Qing
We determine the mass function of young star clusters in the merging galaxies known as the ``Antennae'' (NGC 4038/9) from deep images taken with the Wide Field Planetary Camera 2 on the refurbished Hubble Space Telescope. This is accomplished by means of reddening-free parameters and a comparison with stellar population synthesis tracks to estimat…
Visual binary orbits and masses POST HIPPARCOS
Söderhjelm, Staffan
The parallaxes from Hipparcos are an important ingredient to derive more accurate masses for known orbital binaries, but in order to exploit the parallaxes fully, the orbital elements have to be known to similar precision. The present work gives improved orbital elements for some 205 systems by combining the Hipparcos astrometry with existing grou…
Formation and Evolution of Corotating Interaction Regions and their Three Dimensional Structure
Gosling, J. T.; Pizzo, V. J.
Corotating interaction regions are a consequence of spatial variability in the coronal expansion and solar rotation, which cause solar wind flows of different speeds to become radially aligned. Compressive interaction regions are produced where high-speed wind runs into slower plasma ahead. When the flow pattern emanating from the Sun is roughly t…