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Henry Draper catalogue identifications for Tycho-2 stars
Makarov, V. V.; Fabricius, C.; Wycoff, G. L. +1 more
We present identifications in the Tycho-2 Catalogue, for 99.8 per cent of the stars in the Henry Draper Catalogue and for 96 per cent of the Henry Draper Extensions. Based on observations made with the ESA Hipparcos astrometry satellite. The identifications are available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.7…
Characterizing the Adaptive Optics Off-Axis Point-Spread Function. I. A Semiempirical Method for Use in Natural Guide Star Observations
Lloyd, J. P.; Graham, James R.; Faber, S. M. +11 more
Even though the technology of adaptive optics (AO) is rapidly maturing, calibration of the resulting images remains a major challenge. The AO point-spread function (PSF) changes quickly in both time and position on the sky. In a typical observation, the star used for guiding will be separated from the scientific target by 10"-30". This is sufficie…
HST observations rule out the association between Cir X-1 and SNR G321.9-0.3
Caraveo, P. A.; De Luca, A.; Mignani, R. P. +1 more
Cir X-1 is one of the most intriguing galactic X-ray sources. It is a ~16.6 days variable X/radio source, a type-I X-ray burster and a QPO emitter. In spite of an uncertain optical counterpart classification, all these properties identify the source as an LMXB. The morphology of the surrounding radio nebula has suggested an association with the ne…
The Photospheric Absorption Lines in the Ultraviolet Spectrum of the Multiple System HD 5980
Koenigsberger, Gloria; Kurucz, Robert L.; Georgiev, Leonid
We search for radial velocity variations in the ultraviolet spectra of the erupting Wolf-Rayet/luminous blue variable system HD 5980, located in the Small Magellanic Cloud. We obtain an average radial velocity of 22+/-22 km s-1 for five observations in 1999 at different orbital phases, -39+/-24 km s-1 for one observation in 2…
Will Jets Identify the Progenitors of Type Ia Supernovae?
Livio, Mario; Riess, Adam; Sparks, William
We use the fact that a Type Ia supernova has been serendipitously discovered near the jet of the active galaxy 3C 78 to examine the question of whether jets can enhance accretion onto white dwarfs. One interesting outcome of such a jet-induced accretion process is an enhanced rate of novae in the vicinity of jets. We present results of observation…
The white dwarf cooling sequence in the old open cluster NGC 188
Andreuzzi, G.; Richer, H. B.; Limongi, M. +1 more
We develop the white dwarf luminosity function (LF) of the old open cluster NGC 188 in order to determine a lower limit to the age of the cluster by using the faint end of the cooling sequence. To produce an extensive sequence of the cooling white dwarfs we imaged four contiguous HST-WFPC2 fields in the center of the cluster in the F555W and F814W…
The massive double-lined O-type binary HD 165052
Barbá, R. H.; Morrell, N. I.; Arias, J. I. +3 more
We present a new optical spectroscopic study of the O-type binary HD 165052 based on high- and intermediate-resolution CCD observations. We re-investigated the spectral classification of the binary components, obtaining spectral types of O6.5V and O7.5V for the primary and secondary, respectively, finding that both stars display weak CIIIλ5696 emi…
The Central Binary and Surrounding Nebula of the Symbiotic Star V1016 Cygni
Eyres, S. P. S.; Bode, M. F.; Taylor, A. R. +3 more
We present Hubble Space Telescope (HST) Wide Field Planetary Camera 2 images of the symbiotic star V1016 Cygni that, for the first time, directly explore the inner regions of the nebula to AU scales at optical wavelengths. They also suggest that the [O III] λλ4959, 5007 emission takes place in a bipolar outflow. We use these images to determine th…
Far Ultraviolet Spectroscopic Explorer 900-1200 Å Spectroscopy of AM Herculis
Hutchings, J. B.; Fullerton, A. W.; Cowley, A. P. +1 more
Spectra of the magnetic white dwarf binary AM Herculis were obtained with the Far Ultraviolet Spectroscopic Explorer during three consecutive spacecraft orbits. These observations were split into 19 spectra of about 5 minutes' duration (0.025P binary phase) partially covering the binary orbit. We report the phase-related changes in the far-ultravi…
Coronal Loops Heated by Magnetohydrodynamic Turbulence. I. A Model of Isobaric Quiet-Sun Loops with Constant Cross Sections
Chae, Jongchul; Aschwanden, Markus J.; Poland, Arthur I.
Several recent papers have presented new observational results indicating that many coronal loops in active regions are nearly isothermal. It is expected that quiet-Sun loops may have similar thermal structures, since quiet-Sun differential emission measures look similar to those in active regions. In the quiet Sun, it is well known from observati…