Search Publications
Solar Coronal Heating and the Magnetic Flux Content of the Network
Falconer, D. A.; Moore, R. L.; Porter, J. G. +1 more
We investigate the heating of the quiet corona by measuring the increase of coronal luminosity with the amount of magnetic flux in the underlying network at solar minimum when there were no active regions on the face of the Sun. The coronal luminosity is measured from Fe IX/X-Fe XII pairs of coronal images from SOHO/EIT, under the assumption that …
A Unique Small-Scale Gravitational Arc in A1201
Smith, Graham P.; Treu, Tommaso; van Dokkum, Pieter G. +4 more
We present a snapshot Hubble Space Telescope (HST) image of the galaxy cluster A1201 (z=0.169), revealing a tangential arc 2" from the brightest cluster galaxy (BCG). Keck Echelle Spectrograph and Imager (ESI) spectroscopy confirms that the arc is gravitational in nature and that the source galaxy lies at z=0.451. We construct a model of the gravi…
Mass and Dust in the Disk of a Spiral Lens Galaxy
Hall, Patrick B.; Winn, Joshua N.; Schechter, Paul L.
Gravitational lensing is a potentially important probe of spiral galaxy structure, but only a few cases of lensing by spiral galaxies are known. We present Hubble Space Telescope and Magellan observations of the two-image quasar PMN J2004-1349, revealing that the lens galaxy is a spiral galaxy. One of the quasar images passes through a spiral arm …
Shock emission in the bipolar post-AGB star IRAS 16594-4656
van Hoof, P. A. M.; Van de Steene, G. C.
In this paper we study the near-infrared emission spectrum of IRAS 16594-4656, a bipolar post-AGB star with spectral type B7 and no observed ionization. Using optical and near-infrared photometry we determined the total extinction towards this object to be AV= 7.5+/-0.4 mag and derived a distance of 2.2+/-0.4 kpc, assuming a luminosity …
Solar Large-Scale Channeled Dimmings Produced by Coronal Mass Ejections
Grechnev, V. V.; Chertok, I. M.
A new type of dimmings, or transient coronal holes (i.e., regions of reduced soft-X-ray and EUV emission), is revealed in analyses of difference solar images obtained with the SOHO EIT ultraviolet telescope at 195 Å. Such features can be observed on the solar disk after halo-type coronal mass ejections (CMEs). If several active regions, filaments,…
Sizes of quiet Sun transition region structures
Peter, H.; Gontikakis, C.; Dara, H. C.
We studied the morphology of the transition region of the quiet Sun, with data obtained by the Solar Ultraviolet Measurements of Emitted Radiation spectrometer (SUMER) and the Extreme-Ultraviolet Imaging Telescope (EIT), in September 1996. We analyzed lines emitted in the chromosphere, the low transition region and the low corona. We computed the …
Evidence for a Flux Rope driven EUV wave and CME: Comparison with the Piston Shock Model
Foley, C. R.; Culhane, J. L.; Harra, L. K. +2 more
This paper examines the relationship between a coronal wave, filament eruption, flare and Coronal Mass Ejection (CME) which occurred on 2001, April 10th. We study the pre-flare activity which includes the eruption of a filament and a coronal wave. A large X-ray flare and a CME follow. We discuss how these phenomena are related and compare our resu…
A very young star forming region detected by the ISOPHOT Serendipity Survey
Krause, O.; Lemke, D.; Klaas, U. +4 more
We present a multi-wavelength study of the star forming region ISOSS J 20298+3559, which was identified by a cross-correlation of cold compact sources from the 170 mu m ISOPHOT Serendipity Survey (ISOSS) database coinciding with objects detected by the MSX, 2MASS and IRAS infrared surveys. ISOSS J 20298+3559 is associated with a massive dark cloud…
Infrared Space Observatory Long-Wavelength Spectrometer Spectroscopy of Star-forming Regions in M33
Stacey, G. J.; Higdon, S. J. U.; Higdon, J. L. +1 more
We present Infrared Space Observatory (ISO) Long-Wavelength Spectrometer (LWS) far-infrared (FIR) spectra of the nucleus and six giant H II regions in M33 (NGC 595, IC 142, NGC 592, NGC 604, NGC 588, and IC 133). The seven fine-structure lines observed in the FIR are used to model the H II and photodissociation regions (PDRs). There is no observed…
The active quiescence of HR Del (Nova Del 1967). The ex-nova HR Del
Selvelli, P.; Friedjung, M.
This new UV study of the ex-nova HR Del is based on all of the data obtained with the International Ultraviolet Explorer (IUE) satellite, and includes the important series of spectra taken in 1988 and 1992 that have not been analyzed so far. This has allowed us to make a detailed study of both the long-timescale and the short-timescale UV variatio…