Search Publications
Nearby Young Solar Analogs. I. Catalog and Stellar Characteristics
Gaidos, Eric J.
We present a catalog of 38 young solar analogs within 25 pc, stars that are uniquely well suited for observations of their circumstellar environments to improve our understanding of conditions within the solar system during the Hadean/early Archean eons (prior to 3.8 Gyr ago). These G and early K stars were selected from the Hipparcos astrometric …
An Extendable Galaxy Number Count Model
Gardner, Jonathan P.
I review galaxy number count models and present ncmod, an extendable and general purpose model for comparing and interpreting the results of field galaxy survey data. I develop techniques and software for converting the results of a survey done in one filter into another filter for direct comparison with other surveys. Comparison of the data from …
Automatic Noise Estimation from the Multiresolution Support
Starck, Jean-Luc; Murtagh, Fionn
We describe an automated approach for determining the noise associated with astronomical images. Detector noise is ever present and must be determined for high-quality image filtering or compression. We also show that the method can be used for very high quality cosmic-ray hit removal. Our method is based on a multiresolution transform of the imag…
Characterization and Subtraction of Well-Exposed HST/NICMOS Camera 2 Point-Spread Functions for a Survey of Very Low Mass Companions to Nearby Stars
Krist, John E.; Golimowski, David A.; Schroeder, Daniel J. +1 more
We are conducting a search for very low mass (M<0.2 M_solar) companions of stars within 10 pc of the Sun using the NICMOS infrared camera on the Hubble Space Telescope. The highly exposed images of each target star are subtracted from the NICMOS Camera 2 (NIC2) field using previously observed stars so that faint companions may be detected. We h…
HIPPARCOS Parallaxes of Eclipsing Binaries and the Radiative Flux Scale
Popper, Daniel M.
Eclipsing binaries with Hipparcos parallaxes are found to define a radiative flux relation for main-sequence stars in the B6-F0 range about as well as stars with angular diameters and to extend the range to F8. The fluxes of components of binaries showing large intrinsic variations fall well below the curve for other stars and its extension to low…
The Optical Spectrum of the Planetary Nebula NGC 2440
Hyung, Siek; Aller, Lawrence H.
Wavelengths and identifications have been provided for approximately 300 lines between 3660 and 10125 Å in the spectrum of the bipolar planetary nebula NGC 2440. These lines measured with the Hamilton echelle spectrograph at Lick Observatory and supplemented by published IUE results are used to construct diagnostic diagrams and derive ionic concen…
Pulsation Modes in Small-Amplitude Red Variable Stars
Percy, John R.; Parkes, Michael
We have investigated the pulsation modes of small-amplitude red variables with well-determined periods and accurate Hipparcos parallaxes by comparing observational and theoretical Q-values. In our sample of 13 stars, one appears to be pulsating in the third overtone, nine in the first or second overtone, and three in the fundamental or first overt…
A Long-Period Spectroscopic Binary in the O-Star Multiple System HD 193322
Bolton, C. T.; Fullerton, A. W.; Gies, D. R. +8 more
We present radial velocity measurements and a single-lined spectroscopic orbit for the bright O-type star, HD 193322A, which we show to be a 311 day binary system that has a distant third companion (detected by speckle interferometry) in a 31 yr orbit. We suggest that the speckle companion appears in the spectrum as a broad-lined component of earl…
The Goddard High Resolution Spectrograph: Post-COSTAR Characteristics
Savage, B. D.; Ebbets, D. C.; Carpenter, K. G. +16 more
We review changes to the characteristics of the Goddard High Resolution Spectrograph (GHRS) which resulted from the installation of the Corrective Optics Space Telescope Axial Replacement (COSTAR) on the Hubble Space Telescope. The introduction of two new optical elements into the light path altered the spectral distribution of the light, decreasi…
Constraints on the Radial Velocity Curve of HDE 245770 = A0535+26
Wang, Z. X.; Gies, D. R.
We present new radial velocity measurements from IUE high-dispersion spectra of HDE 245770, the Be companion of the X-ray transient binary system, A0535+26. We formally derive the semiamplitude of the star's binary motion by fitting the UV and published radial velocity measurements with the other orbital parameters fixed according to the neutron s…