Search Publications
ASCA (and HST) observations of NLS1s
Leighly, Karen M.
The study of NLS1s using ASCA has many advantages. A representative sample can be studied; to date, observations of more than 30 NLS1s have been made. ASCA observations are conducted contiguously, so their X-ray variability properties can be studied systematically. ASCA detectors have a broad band pass and moderate energy resolution, properties wh…
FOS observations of four NLS1s
Goodrich, Robert W.
Ultraviolet through optical spectroscopy of four NLS1s shows strong absorption features in the high-ionization UV resonance lines such as C IV, N V, and Si IV. Mg II is not absorbed. The absorption could originate in the warm absorber.
V751 Cyg and V Sge as transient supersoft X-ray sources
Greiner, Jochen
I review the observational evidence for luminous, soft X-ray emission during optical low-states in the two cataclysmic variables V751 Cyg and V Sge, and discuss the possible link to the canonical supersoft X-ray sources.
Chemical enrichment by massive stars
Thuan, T. X.; Izotov, Y. I.
Heavy element abundances derived from high-quality ground-based and Hubble Space Telescope (HST) spectroscopic observations of low-metallicity blue compact galaxies (BCGs) with oxygen abundances 12+log O/H between 7.1 and 8.3 are discussed. None of the heavy element-to-oxygen abundance ratios studied here (C/O, N/O, Ne/O, Si/O, S/O, Ar/O, Fe/O) de…
Extragalactic novae
Shara, Michael M.
Novae are expected to form in all stellar systems with a binary population. Detection of extragalactic novae provides direct evidence of close binary populations and possible spatial variations in those populations. Comparison of extragalactic novae with their local counterparts can yield valuable tests of close binary evolution theory. I report e…
Dynamics of the transition region
Gontikakis, C.; Dara, H. C.
In this review, we consider the problem of the apparent redshifts of the UV lines in the transition region and review the basic observations made over the last decades, especially the observations of the last few years from satellite observatories. Moreover, we revise the most popular theoretical explanations for the motions in the transition regi…
The UV spectra of NLS1s - implications for their broad line regions
Brandt, W. N.; Vestergaard, M.; Mathur, S. +3 more
We study the UV spectra of NLS1 galaxies and compare them with typical Seyfert 1 galaxies and quasars. The NLS1 spectra show narrower UV lines as well as weaker CIV λ1549 and CIII] λ1909 emission. We show that these line properties are due to a lower ionization parameter and somewhat higher BLR cloud densities. These modified conditions can be exp…
What we learn from quantitative ultraviolet spectroscopy of naked white dwarfs in cataclysmic variables
Long, Knox S.
Using the Hopkins Ultraviolet Telescope and Hubble Space Telescope, observers have now obtained UV spectra with sufficient signal to noise and resolution to allow quantitative spectroscopic analyses of the WDs in several DNe. In the "cleanest" DNe, such as U Gem, the observations are allowing the basic physical parameters of the WD - temperature, …
Molecular gas and star formation in the host galaxy of I Zw 1
Schinnerer, Eva; Eckart, Andreas; Tacconi, Linda
A recent analysis of high angular resolution NIR imaging and spectroscopic data in conjunction with Plateau de Bure interferometric mm-line observations indicate the presence of a circum-nuclear starburst ring of ∼1.5″ (1.5 kpc) diameter in I Zw 1. High angular resolution NIR imaging, using the MPE SHARP camera at the ESO NTT, HST V-band images, a…
Weak lensing analysis of CL 1358+62
Franx, Marijn; Hoekstra, Henk; Kuijken, Konrad +1 more
We report on the detection of weak gravitational lensing of faint, distant background objects by Cl 1358+62, a rich cluster of galaxies at a redshift of z = 0.33. The observations consist of a multicolor mosaic of 12 WFPC2 pointings of the Hubble Space Telescope (HST). We find a projected mass of (4.4±0.6) × 10 14 M ⊙ within …