Search Publications
The 1993-1994 Activity of EX Lupi
Herbig, G. H.; Aspin, C.; Gilmore, Alan C. +2 more
EX Lupi is a classical T Tauri star (and the EXor prototype) subject to sporadic outbursts. The historic record shows that it remains at about V=13.2 (or mpg=14.7:) for extended periods, from which it has been observed to brighten to as much as V=8.4 (on one occasion in 1955-1956). During 1993-1994 the star remained slightly above norma…
Spectroscopic Observation of the Planetary Nebula IC 4846
Hyung, Siek; Aller, Lawrence H.; Lee, Woo-baik
A high-dispersion optical (3700-10100 Å) spectrum was secured with the Hamilton echelle spectrograph at the coudé focus of the 120 inch (3 m) Shane telescope at Lick Observatory, with the goal of deriving chemical abundances for the compact planetary nebula IC 4846. We also remeasured the UV spectra from the IUE archive. Diagnostics indicate that …
Markarian 478: A Second Seyfert Galaxy with 1 Micron Fe II Emission Lines
Hamann, F.; Rudy, Richard J.; Puetter, R. C. +3 more
We present infrared spectroscopy of the narrow-line Seyfert 1 galaxy Mrk 478 that shows the 1 µm Fe II lines λ9997, λ10501, λ10863, and λ11126. This is the second active galaxy, after I Zw 1, in which these features have been observed. Like I Zw 1, the 1 µm Fe II lines of Mrk 478 appear to arise from collisional excitation of their com…
The Accretion Disk and White Dwarf in the Short-Period Dwarf Novae TY Piscium and V436 Centauri during Quiescence
Sion, Edward M.; Nadalin, Ira
The short-period dwarf novae TY Psc and V436 Cen are SU UMa systems with very similar orbital periods, similar recurrence times for normal outbursts (~23 days) and superoutbursts (~340 days), and nearly identical outburst amplitudes. We have carried out high-gravity model atmosphere and accretion disk synthetic spectra from the grid of Wade & …
The Accretion Disk and White Dwarf during the Quiescence of the Dwarf Novae VW Vulpeculae and χ Leonis
Sion, Edward M.; Henry, Colleen K.
We have carried out an International Ultraviolet Explorer archival comparative study of the two U Geminorum type dwarf novae VW Vulpeculae and χ Leonis. The spectrum of χ Leo does not show any C IV, a feature normally seen in the vast majority of other dwarf novae. For VW Vul, a single-temperature high-gravity photosphere does not produce a consis…
The Orbit and Spectral Line Variations of the Massive Binary HD 163181 (V453 Scorpii)
Wang, Z.; Gies, D. R.; Bagnuolo, W. G., Jr. +3 more
We present revised orbital elements for the massive interacting binary HD 163181, and we offer the first evidence of apsidal motion in the orbit (apsidal period U=510+/-100 yr). We searched for but found no obvious evidence of the secondary's spectral lines in our optical spectra. We do observe, however, systematic profile variations with orbital …
A Study of the Wavelength Calibration of NEWSIPS High-Dispersion Spectra
Smith, Myron A.
In this study we cross-correlate many IUE echellograms of a variety of well-observed stars to evaluate systematic error sources in the wavelength zero points (velocities) of all three cameras. We first evaluate differences between the final archived (``NEWSIPS'') and the originally processed (``IUESIPS'') echellograms. These show a marked time dep…
The Underlying White Dwarf Accretor in the Dwarf Nova UU Aquilae
Sion, Edward M.; Stump, Michael
We present a high-gravity, solar composition model atmosphere and model accretion disk study of the U Gem type dwarf nova UU Aql. We have identified the far-UV signature of the underlying white dwarf for the first time. Our best-fit model atmosphere to the observed far-UV spectrum in quiescence is 27,000+/-1000 K. The solar abundance high-gravity …