Search Publications
Evolution of Chromospheric Structures: How Chromospheric Structures Contribute to the Solar HE II 30.4 Nanometer Irradiance and Variability
Woods, Thomas N.; Worden, John; Neupert, Werner M. +1 more
The bright He II 30.4 nm solar emission is an important energy source for ionization and heating of the Earth's upper atmosphere. The analysis of the Solar and Heliospheric Observatory (SOHO) Extreme-Ultraviolet Imaging Telescope (EIT) He II 30.4 nm images provides an improved understanding of how the solar surface structures, i.e., plage, enhance…
A Hubble Space Telescope Optical and Ground-based Near-Infrared Study of the Giant Nuclear Ring in ESO 565-11
Buta, R.; Crocker, D. A.; Byrd, G. G.
We present multiband Wide Field Planetary Camera 2 images of the central regions of ESO 565-11, a peculiar southern barred galaxy recently shown to have the largest known example of a circumnuclear starburst ring. We also present ground-based near-infrared H-band imaging and photometry of the galaxy. The results provide an interesting picture of t…
Observations of Transition Region Plasma
Brekke, Pâl
Recent space missions have changed our view of the solar transition region. In particular the ESA/NASA Solar and Heliospheric Observatory (SOHO) and NASA's TRACE satellite have provided a unique opportunity to explore the solar atmosphere in detail. The combination of high spatial, spectral and temporal observations has made it possible to derive …
Nonthermal Radio Signatures of Coronal Disturbances with and without Coronal Mass Ejections
Thompson, B. J.; Andrews, M. D.; Mann, G. +3 more
This study presents data on two events from the Extreme-UV Imaging Telescope (EIT) and the Large Angle and Spectroscopic Coronagraph instruments (C1, C2, and C3), Geostationary Operational Environmental Satellite (GOES) soft X-ray data, and 40-800 MHz radio spectra of the Astrophysical Institute Potsdam. At first glance, the two events appear simi…
The Hubble Space Telescope Key Project on the Extragalactic Distance Scale. XIX. The Discovery of Cepheids in and a New Distance to NGC 3198
Kelson, Daniel D.; Illingworth, Garth D.; Huchra, John P. +17 more
We report the detection of Cepheid variable stars and a new distance to the Sc spiral NGC 3198. NGC 3198 is one of 25 galaxies that have been observed with the WFPC2 of the Hubble Space Telescope (HST) for the purpose of measuring Cepheid distances. Eighteen of these galaxies were targeted by the HST Key Project on the Extragalactic Distance Scale…
Electron density and temperature structure of two limb active regions observed by SOHO-CDS
Young, P. R.; Mason, H. E.; Landi, E. +1 more
The analysis of two active regions on the limb using observations from SOHO-CDS allows us to determine the electron density and temperature distribution of the coronal emission. We find that the active regions have hot cores (3×106 K) with larger cooler (106 K) loop structures extending above the limb. The electron number den…
Depth of excitation and reversal of asymmetry of low-l solar P modes: a complementary analysis of BiSON* and VIRGO/SPM† data
Chaplin, W. J.; Appourchaux, T.
We use the solutions to a simple, one-dimensional wave equation - which is intended to describe the essential elements of the solar resonant acoustic cavity - as formalistic models to which to fit low-l modes in observational helioseismic power spectra. We have analysed data collected in velocity, by the ground-based Birmingham Solar-Oscillations …
Radio Detections of Stellar Winds from the Pistol Star and Other Stars in the Galactic Center Quintuplet Cluster
Goss, W. M.; Morris, Mark; Lang, Cornelia C. +1 more
Very Large Array images of the Sickle and Pistol H II regions near the Galactic center at 8.3 and 4.9 GHz reveal six point sources in the region where the dense Quintuplet stellar cluster is located. The spectral indices of five of these sources between 6 and 3.6 cm have values of α=0.5 to 0.8 (where Sν~να), consistent with t…
HST observations of Terzan 1: a second parameter globular cluster in the galactic bulge
Bica, E.; Barbuy, B.; Marconi, G. +3 more
Hubble Space Telescope observations in the F555W and F814W bands are presented of the bulge globular cluster Terzan 1. This highly obscured cluster has the smallest projected distance to the Galactic center among all known globulars. Its colour-magnitude diagram shows a red horizontal branch, which is typical of metal-rich clusters, combined to a …
The extremely young open cluster NGC 6611: Compiled catalogue, absorption map and the HR diagram
Piskunov, A. E.; Kharchenko, N. V.; Schilbach, E. +1 more
A compiled catalogue of astrometric and photometric data for about 2200 stars down to V=16.8() m is presented. The stars are located in an area with a radius of 22.8 arcmin around the extremely young open cluster NGC 6611 with the cluster center at (alpha ,delta )_{2000.0}=18() h18() m40() s,-13(deg) 47.1'. The catalogue is based on new reductions…