Search Publications
Astrophysics in 1999
Aschwanden, Markus J.; Trimble, Virginia
The year 1999 saw the arrival of a star with three planets, a universe with three parameters, and a solar corona that could be heated at least three ways. In addition, there were at least three papers on every question that has ever been asked in astrophysics, from ``Will the Universe expand forever?'' to ``Does mantle convection occur in one or t…
V1073 Cygni: A New Light Curve and Analysis
Morris, Steven L.; Naftilan, Stephen A.
A new CCD light curve of the A-type W UMa star V1073 Cygni has been obtained, and the differential-corrections method of Wilson and Devinney was used to compute a new set of system parameters. The same analysis has been applied to the other photometric light curves in the literature, including the Hipparcos light curve. A new ephemeris is determin…
Periodicities in the Ultraviolet Flux of α Orionis
Houck, J. R.; Hajian, Arsen R.; Terzian, Yervant +1 more
We have used low-resolution spectra from the International Ultraviolet Explorer (IUE) to look for periodicities in the ultraviolet flux from α Orionis. The total continuum flux for each observation was integrated, producing longwave (1900-3200 Å) and shortwave (1250-1750 Å) light curves. The periodograms resulting from the shortwave data are noise…
Close Approaches of Stars to the Solar System Based on Hipparcos Data
García-Sánchez, Joan
Astrometry of the ω Centauri Hubble Space Telescope Calibration Field
Mighell, Kenneth J.
Astrometry, on the International Celestial Reference Frame (epoch J2000.0), is presented for the Walker (1994, PASP, 106, 824) stars in the ω Centauri (=NGC 5139=C1323-1472) Hubble Space Telescope (HST) Wide Field/Planetary Camera (WF/PC) calibration field of Harris et al. (1993, AJ, 105, 1196). Harris et al. stars were first identified on a WFPC2…
The Ultraviolet and Optical Continuum Emission in Active Galactic Nuclei: The Status of Accretion Disks
Koratkar, Anuradha; Blaes, Omer
A fundamental component of models of active galactic nuclei (AGNs) is an accretion disk around a supermassive black hole. However, the nature of this accretion disk is not well understood, and current models do not provide a satisfactory explanation of the optical/UV continuum observed in AGNs. In this paper we review the substantial theoretical a…
White Dwarfs in Cataclysmic Variables
Sion, E. M.
Prior to the last 15 years, the literature on cataclysmic variables (CVs) contained little on the properties of the underlying white dwarf accreter other than estimates of their masses. They were regarded simply as nondescript potential wells for studies of accretion disk structure and stability. Estimates of their masses and associated core compo…
Calibration of the MACHO Photometry Database
Alcock, C.; Allsman, R. A.; Alves, D. R. +22 more
The MACHO Project is a microlensing survey that monitors the brightnesses of ~60 million stars in the Large Magellanic Cloud (LMC), Small Magellanic Cloud, and Galactic bulge. Our database presently contains about 80 billion photometric measurements, a significant fraction of all astronomical photometry. We describe the calibration of MACHO two-co…
Charge-Transfer Efficiency of WFPC2
Casertano, Stefano; Heyer, Inge; Whitmore, Bradley
Observations of ω Centauri have been used to characterize the charge-transfer efficiency (CTE) of the Wide Field and Planetary Camera 2 (WFPC2) on board the Hubble Space Telescope. A set of formulae has been developed to correct aperture photometry for CTE loss with dependencies on the X- and Y-positions, the background counts, the brightness of t…
The Detection and Photometric Redshift Determination of Distant Galaxies Using SIRTF's Infrared Array Camera
Simpson, Chris; Eisenhardt, Peter
We investigate the ability of the Space Infrared Telescope Facility's Infrared Array Camera to detect distant (z~3) galaxies and measure their photometric redshifts. Our analysis shows that changing the original long-wavelength filter specifications provides significant improvements in performance in this and other areas.