Search Publications

Interpretation of Ultraviolet Absorption Lines in SN 1006

Crenshaw, D. M.; Sarazin, C. L.; Wu, C. -C. +2 more

We present a theoretical interpretation of the broad silicon and iron ultraviolet absorption features observed with the Hubble Space Telescope (HST) in the spectrum of the Schweizer-Middleditch star behind the remnant of SN 1006. These features are caused by supernova ejecta in SN 1006.

We propose that the redshifted Si II 1260 Å feature cons…

EUV Observations of a Macrospicule: Evidence for Solar Wind Acceleration?

Harrison, R. A.; Pike, C. D.

We present a unique observation of a macrospicule, recorded in extreme ultraviolet light on 11 April 1996, using the Coronal Diagnostic Spectrometer (CDS) on board the Solar and Heliospheric Observatory (SOHO). The observation was made by chance as part of a daily, large-area mapping sequence. Although the feature has some characteristics of the c…

Eclipse Mapping of the Accretion Disk Wind in the Cataclysmic Variable UX Ursae Majoris

Drew, Janet E.; Knigge, Christian

We present the results of an effort to model recent HST eclipse observations of the C IV 1550 Å resonance line in the high-inclination nova-like cataclysmic variable UX UMa. Assuming this line to be predominantly wind-formed, we are able to roughly reproduce the shapes and strengths of the observed line profiles (both away from and during eclipse)…

An adaptive grid code for high resolution 1-D hydrodynamics of the solar and stellar transition region and corona

Peres, G.; Reale, F.; Betta, R. +1 more

We present a new version of the Palermo-Harvard hydrodynamic model of plasma confined in coronal loops, based on a regridding algorithm which ensures limited variations of thermodynamical variables across grid points. The code provides an accurate description of the dynamics of the chromosphere-corona transition region, in spite of the very steep …

Additional Observations and Analysis of the Lyman-α Absorption Lines toward the QSO Pair Q0107-025A,B

Morris, Simon L.; Weymann, Ray J.; Foltz, Craig B. +3 more

We present further analysis and discussion of the properties of the absorption lines in the QSO pair Q0107-025A,B (z_em = 0.956, 0.952; angular separation 1.29 arcmin) based upon spectroscopy obtained with the Faint Object Spectrograph (FOS) of the Hubble Space Telescope (HST). We also present observations of the pair at shorter waveleng…

Evidence for Galaxy Interactions/Mergers from Medium Deep Survey WFPC2 Data

Im, M.; Griffiths, R. E.; Ratnatunga, K. U. +3 more

We examine the morphological and statistical properties of close galaxy pairs from two sets of 28 WFPC2 fields, acquired for the Medium Deep Survey (MDS) and the Groth-Westphal Survey (GWS) in F606W (V) and F814W (I) passbands. In the GWS sample all fields have uniform 95% completeness down to I <~ 24.3 mag, whereas in the MDS sample, fields ha…

The Distance to the Coma Cluster from Surface Brightness Fluctuations

Baum, William A.; Hammergren, Mark; Thomsen, Bjarne +1 more

We report on the first determination of the distance to the Coma Cluster from surface brightness fluctuation (SBF) measurements obtained from Hubble Space Telescope WFPC2 observations of the bright E0 galaxy NGC 4881 in the Coma Cluster and ground-based observations of the ``standard'' E1 galaxy NGC 3379 in the Leo-I group. Relative distances base…

Imaging the nuclear environment of NGC 1365 with the Hubble Space Telescope

Boksenberg, Alec; Lindblad, Per Olof; Kristen, Helmuth +1 more

The region surrounding the active nucleus of the barred spiral galaxy NGC 1365 is observed in the [Oiii] lambda 5007 line and neighbouring continuum using the Faint Object Camera (FOC) aboard the Hubble Space Telescope (HST). In the continuum light numerous bright ``super star clusters'' (SSCs) are seen in the nuclear region. They tend to fall on …

Detection of SO₂ on Callisto with the Hubble Space Telescope

Johnson, Robert E.; McGrath, Melissa A.; Noll, Keith S. +1 more

We have detected SO₂ in ultraviolet spectra of Callisto obtained with the Hubble Space Telescope's Faint Object Spectrograph. An absorption band centered at 280 nm appears in the spectrum of Callisto's leading hemisphere, but is not apparent in the spectrum of the trailing hemisphere. The band is similar to the SO₂ band on Eu…

A 200km/s molecular wind in the peculiar carbon star V Hya.

Jorissen, A.; Knapp, G. R.; Young, K.

A molecular wind with an outflow speed in excess of 200km/s has been found in the AGB carbon star V Hya. Observations of several molecular lines show that the circumstellar envelope is expanding at 15km/s and is flattened and inclined to the line of sight. The fast wind appears to be expanding from the poles of the envelope, with the expansion spe…