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Fundamental parameters of Galactic luminous OB stars. IV. The upper HR diagram
Herrero, A.; Puls, J.; Villamariz, M. R.
We present observations and analyses of seven Galactic O stars of type O6 and earlier. The analyses are carried out using NLTE plane-parallel, hydrostatic models as well as NLTE spherical models with mass-loss. With detailed calculations for the former and simulations for the latter, it is shown that the flux blocking due to UV metal lines is impo…
Dust in PG quasars as seen by ISO
Meisenheimer, K.; Lemke, D.; Klaas, U. +5 more
Infrared to millimeter spectral energy distributions (SEDs) have been obtained for a random sample of 17 Palomar Green quasars. The observations were carried out between 4.8 and 200 mu m with ISO and supplemented for ten sources with IRAM at 1.3 mm. Eight sources were detected in the far infrared for the first time. The SEDs provide evidence for c…
Eclipsing Binaries as Astrophysical Laboratories: Internal Structure, Core Convection, and Evolution of the B-Star Components of V380 Cygni
Fitzpatrick, Edward L.; Guinan, Edward F.; Jordi, Carme +4 more
New photometric solutions have been carried out on the important eccentric eclipsing system V380 Cygni (B1.5 II-III+B2 V) from UBV differential photoelectric photometry obtained by us. The photometric elements obtained from the analysis of the light curves have been combined with the spectroscopic solution recently published by Popper & Guinan…
The DIRECT Project: Influence of Blending on the Cepheid Distance Scale. I. Cepheids in M31
Stanek, K. Z.; Macri, L. M.; Mochejska, B. J. +1 more
We investigate the influence of blending on the Cepheid distance scale. Blending is the close association of a Cepheid with one or more intrinsically luminous stars. High-resolution HST images are compared with our ground-based data, obtained as part of the DIRECT project, for a sample of 22 Cepheids in the M31 galaxy. The average (median) V-band …
The Hubble Space Telescope Key Project on the Extragalactic Distance Scale. XXVII. A Derivation of the Hubble Constant Using the Fundamental Plane and Dn-σ Relations in Leo I, Virgo, and Fornax
Kelson, Daniel D.; Illingworth, Garth D.; Huchra, John P. +18 more
Using published photometry and spectroscopy, we construct the fundamental plane and Dn-σ relations in Leo I, Virgo, and Fornax. The published Cepheid period-luminosity (PL) relations to spirals in these clusters fixes the relation between angular size and metric distance for both the fundamental plane and Dn-σ relations. Usin…
Caltech Faint Galaxy Redshift Survey. XIV. Galaxy Morphology in the Hubble Deep Field (North) and Its Flanking Fields to Z=1.2
Hogg, David W.; Cohen, Judith G.; van den Bergh, Sidney +1 more
Morphological classifications are reported for Hubble Space Telescope images of 241 galaxies in the Hubble Deep Field and its flanking fields with measured redshifts in the interval 0.25<z<1.2, drawn from a magnitude-limited redshift survey to R=24.0. The galaxies are divided into three groups with redshifts in the intervals 0.25-0.6, 0.6-0.…
Reconciling Spectroscopic Electron Temperature Measurements in the Solar Corona with In Situ Charge State Observations
Esser, Ruth; Edgar, Richard J.
It has been a puzzle for quite some time that spectroscopic measurements in the inner corona indicate electron temperatures far too low to produce the ion fractions observed in situ in the solar wind. In the present Letter, we show that in order to reconcile the two sets of measurements, a number of conditions have to exist in the inner corona: (1…
The HST view of the FR I / FR II dichotomy
Capetti, A.; Chiaberge, M.; Celotti, A.
In order to explore how the FR I / FR II dichotomy is related to the nuclear properties of radio galaxies, we studied a complete sample of 26 nearby FR II radio galaxies using Hubble Space Telescope (HST) images and compared them with a sample of FR I previously analyzed. FR I nuclei lie in the radio-optical luminosity plane along a tight linear c…
Exobiological Implications of a Possible Ammonia-Water Ocean inside Titan
Fortes, A. D.
Models of Titan's thermal history indicate that an ocean consisting of an ammonia-water solution, as much as 200 km deep, is presently concealed beneath a crust of water ice. Conditions within this hypothetical ocean are discussed here and compared with conditions in terrestrial biomes. These conditions, while extreme by terrestrial standards, are…
The ISOPHOT 170 µ m serendipity survey. I. Compact sources with galaxy associations
Kessler, M. F.; Lemke, D.; Rowan-Robinson, M. +6 more
The first set of compact sources observed in the ISOPHOT 170 µm Serendipity Survey is presented. From the slew data with low (I100 µm <= 15 MJy/sr) cirrus background, 115 well-observed sources with a high signal-to-noise ratio in all detector pixels having a galaxy association were extracted. Of the galaxies with known op…