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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…
Astrophysics in 2001
Aschwanden, Markus J.; Trimble, Virginia
During the year, astronomers provided explanations for solar topics ranging from the multiple personality disorder of neutrinos to cannibalism of CMEs (coronal mass ejections) and extra-solar topics including quivering stars, out-of-phase gaseous media, black holes of all sizes (too large, too small, and too medium), and the existence of the unive…
The Ultraviolet Light Curve of LMC X-4: X-Ray Heating of the O Star and Accretion Disk
Boroson, Bram; Vrtilek, Saeqa Dil; Preciado, Michael E.
We present an archival study of ultraviolet spectra of the X-ray binary LMC X-4 obtained with the IUE satellite. We fit these spectra with models that incorporate the X-ray heating of the O star and accretion disk. A systematic analysis of the UV continuum confirms the general picture of an O star that fills its Roche lobe and is heated by X-rays …
Solving Olin Wilson's Mystery
Abt, Helmut A.
Wilson showed that G8-M1 dwarfs have a range of 0.30 mag in P-V color whereas the color range for earlier stars is 0.12 mag. He attributed the increased range for the later stars to differing hydrogen-to-metal ratios in the temperature region where most of the electrons come from the metals. I explored those stars using Hipparcos parallaxes and ph…