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Digging Deeper in the Coronal Graveyard
Ayres, Thomas R.; Brown, Alexander; Carpenter, K. G. +4 more
Soft X-ray detections of stellar coronae (T ~ 106 K) are rare in the giant branch redward of ~K1 III. We have conducted a less direct--but more sensitive--search using the Hubble Space Telescope Goddard High-Resolution Spectrograph to probe for far-ultraviolet proxies of the hot coronal gas in representative ``noncoronal'' red giants. I…
The high-excitation planetary nebula NGC 6741
Hyung, Siek; Aller, Lawrence H.
The compact, bright Peimbert type I planetary nebula NGC 6741 shows an unusually rich spectrum which is studied here from 3700 to 10 370 A with the Hamilton Echelle spectrograph at the Lick Observatory. By combining Hamilton Echelle observations with archive UV data secured with the International Ultraviolet Explorer (IUE), and with available IR d…
Ulysses observations of wave activity at interplanetary shocks and implications for type II radio bursts
MacDowall, R. J.; Phillips, J. L.; Stone, R. G. +2 more
We present the first quantitative investigation of interplanetary type II radio emission in which in situ waves measured at interplanetary shocks are used to compute radio wave intensities for comparison with type II observations. This study is based on in situ measurements of 42 in-ecliptic forward shocks as well as 10 intervals of type II emissi…
Ultraviolet Interstellar Absorption Lines toward the Starburst Dwarf Galaxy NGC 1705
Blades, J. Chris; Sahu, M. S.
Archival Goddard High Resolution Spectrograph (GHRS) low-resolution spectra of NGC 1705, with wavelength ranges of 1170.3-1461.7 Å and 1453.5-1740.1 Å and a velocity resolution of ~120 kms-1, have been used to derive the velocity structure and equivalent widths of the absorption lines of Si II λ1190.42, λ1260.42, λ1304.37, and λ1526.71,…
The Initial Mass Function of Low-Mass Stars in Globular Clusters
Paresce, Francesco; De Marchi, Guido
We compare deep I-band luminosity functions of two globular clusters (NGC 6397 and NGC 6656) that have similar metal content but have experienced very different dynamical histories, both in terms of internal dynamics and as a result of different interactions with the Galactic tidal field. Their luminosity functions measured at the half-mass radius…
EK TrA, a close relative of VW HYI
Gänsicke, B. T.; Beuermann, K.; Thomas, H. -C.
The southern dwarf nova EK TrA has been suggested to show the spectrum of its white dwarf primary in the single available International Ultraviolet Explorer (IUE) post-outburst spectrum. We demonstrate that this spectrum is still disc-dominated. However, a careful analysis reveals a white dwarf contribution of ~25 per cent of the SWP flux and a wh…
The Color-Magnitude Diagram in Baade's Window Revisited
Kiraga, Marcin; Paczyński, Bohdan; Stanek, Krzysztof Z.
We have reanalyzed the OGLE V and I photometry of ~500,000 stars in Baade's Window, and we confirm the extinction map published by Stanek. However, we find that the interpretation of the OGLE color-magnitude diagram for the disk stars proposed by Paczyński et al. was incorrect: the dominant disk population in Baade's Window is old, and we find no …
Final Astro-1 Calibration of the Hopkins Ultraviolet Telescope: A Test of White Dwarf Model Atmospheres as Far-Ultraviolet Calibration Standards
Kriss, Gerard A.; Holberg, J. B.; Kimble, Randy A. +5 more
We present the final calibration of the Hopkins Ultraviolet Telescope (HUT) for its flight during the Astro-1 space shuttle mission in 1990 December. The calibration is defined by a comparison between an observation obtained in flight of the hot DA white dwarf G191-B2B and the model atmosphere for this star calculated by P. Bergeron. We also prese…
The nature of the broad-line region in the radio-loud active galactic nucleus 3C 390.3
Schartel, Norbert; Wamsteker, Willem; Wang, Ting-Gui +1 more
We present the results of an analysis of the ultraviolet and X-ray variability of the broad-line radio (BLR) galaxy 3C 390.3 over 15 years. The ultraviolet (UV) continuum of 3C 390.3 shows large variations with amplitudes of up to a factor of 10. We find the following results. (1) The variations of Civ and Lyalpha are highly correlated with the UV…
The Mass and Radius of 40 Eridani B from HIPPARCOS: An Accurate Test of Stellar Interior Theory
Provencal, J. L.; Shipman, H. L.; Thejll, P. +1 more
The astrometric satellite HIPPARCOS has determined the distance to the important white dwarf 40 Eridani B with an accuracy surpassing 1%. We use this datum to redetermine the mass and radius of this star and find that M = 0.501 +/- 0.011 Msolar and R = 0.0136 +/- 0.00024 Rsolar. These values, the most accurately determined ma…