Search Publications
Hubble Space Telescope Spectroscopy of V471 Tauri: Oversized K Star, Paradoxical White Dwarf
Bond, Howard E.; Sion, Edward M.; O'Brien, M. Sean
We have used the Goddard High Resolution Spectrograph on board the Hubble Space Telescope to obtain Lyα spectra of the hot white dwarf (WD) component of the short-period eclipsing DA+dK2 precataclysmic binary V471 Tauri, a member of the Hyades star cluster. Radial velocities of the WD were determined from eight post-COSTAR spectra obtained near th…
Observational Constraints on Coronal Heating Models Using Coronal Diagnostics Spectrometer and Soft X-Ray Telescope Data
Schmelz, J. T.; Scopes, R. T.; Cirtain, J. W. +2 more
We have constructed a multithermal differential emission measure distribution for several pixels along a relatively isolated coronal loop on the southwest limb of the solar disk using spectral line data from the Solar and Heliospheric Observatory coronal diagnostics spectrometer (CDS) and broadband data from the Yohkoh soft X-ray telescope. The te…
Source Regions of Coronal Mass Ejections
Dere, K. P.; Subramanian, Prasad
Observations of the solar corona with the Large Angle and Spectrometric Coronagraph Experiment (LASCO) and EUV Imaging Telescope (EIT) instruments on the Solar and Heliospheric Observatory (SOHO) provide an unprecedented opportunity to study coronal mass ejections (CMEs) from their initiation through their evolution out to 30 Rsolar. Th…
Lithium abundances for 185 main-sequence stars: Galactic evolution and stellar depletion of lithium
Zhao, G.; Nissen, P. E.; Chen, Y. Q. +1 more
We present a survey of lithium abundances in 185 main-sequence field stars with 5600 <~ Teff <~ 6600 K and -1.4 <~ [Fe/H] <~ +0.2 based on new measurements of the equivalent width of the lambda 6708 Li I line in high-resolution spectra of 130 stars and a reanalysis of data for 55 stars from Lambert et al. (\cite{Lambert91}).…
SOHO Observations of a Coronal Mass Ejection
Vourlidas, Angelos; Wu, R.; Raymond, John C. +5 more
We describe a coronal mass ejection (CME) observed on 1999 April 23 by the Ultraviolet Coronagraph Spectrometer (UVCS), the Extreme-Ultraviolet Imaging Telescope (EIT), and the Large-Angle and Spectrometric Coronagraphs (LASCO) aboard the Solar and Heliospheric Observatory (SOHO). In addition to the O VI and C III lines typical of UVCS spectra of …
Detection of Cosmic Shear with the Hubble Space Telescope Survey Strip
Refregier, Alexandre; Rhodes, Jason; Groth, Edward J.
Weak lensing by large-scale structure provides a unique method to directly measure matter fluctuations in the universe and has recently been detected from the ground. Here we report the first detection of this ``cosmic shear'' based on space-based images. The detection was derived from the Hubble Space Telescope (HST) Survey Strip (or ``Groth Stri…
Radial Velocity Studies of Close Binary Stars. IV.
Rucinski, Slavek M.; Lu, Wenxian; Ogłoza, Waldemar
Radial velocity measurements and sine-curve fits to the orbital velocity variations are presented for the fourth set of 10 close binary systems: 44 Boo, FI Boo, V2150 Cyg, V899 Her, EX Leo, VZ Lib, SW Lyn, V2377 Oph, Anon Psc (GSC 8-324), and HT Vir. All systems are double-lined spectroscopic binaries, with only two of them not being contact syste…
The Spatial Distribution of O-B5 Stars in the Solar Neighborhood as Measured by Hipparcos
Maíz-Apellániz, Jesús
We have developed a method to calculate the fundamental parameters of the vertical structure of the Galaxy in the solar neighborhood from trigonometric parallaxes alone. The method takes into account Lutz-Kelker-type biases in a self-consistent way and has been applied to a sample of O-B5 stars obtained from the Hipparcos catalog. We find that the…
The helium content and age of the Hyades:. Constraints from five binary systems and Hipparcos parallaxes
Lebreton, Y.; Fernandes, J.; Lejeune, T.
We compare the accurate empirical mass-luminosity (M-L) relation based on five Hyades binary systems to predictions of stellar models calculated with various input parameters (helium, metallicity and age) or physics (mixing-length ratio, model atmosphere, equation of state and microscopic diffusion). Models based on a helium content Y ~ 0.28 infer…
The properties of field elliptical galaxies at intermediate redshift - II. Photometry and spectroscopy of an HST-selected sample
Treu, T.; Stiavelli, M.; Møller, P. +2 more
A sample of field early-type galaxies (E/S0) at intermediate redshift (z~0.1-0.6) is selected, based on morphology and colours from HST-WFPC2 parallel images. Photometric structural parameters (effective radius Re and effective surface brightness SBe) are derived through the F606W and F814W filters, using luminosity profile f…