Search Publications
HST photometry of the stars near the center of PN NGC 650
Pottasch, S. R.; Koornneef, J.
Colours and magnitudes of the central star of NGC 650 and its two companions have been obtained from HST images. The spectral types of the companions, which have been deduced from the colours, suggest a probable distance to the companions of between 5 and 6 kpc. Using the spectral and photometric characteristics of the central star, which are very…
A Search for an Emission-Line Region in the Hydrogen-deficient Carbon Star HD 182040
Clayton, Geoffrey C.; Ayres, T. R.; Brunner, Andrew R.
A long-exposure short-wavelength IUE spectrum of the hydrogen-deficient carbon (HdC) star HD 182040 does not show any detectable emission in the C II lambda1335 line. It is not certain whether this absence of emission is intrinsic or due to the large uncertainties in the distance, absolute luminosity, and reddening toward HD 182040. If intrinsic, …
Cassini as a heliospheric probe - the potential of pick-up ion measurements during its cruise phase
Fichtner, H.; Mall, U.; Hamilton, D. C. +2 more
Measurements of the spatial distributions of pick-up ions can be utilized to infer important information about the structure of the heliosphere. First, a determination of the symmetry axis of flux distributions of pick-up ions not experiencing any significant filtration of their neutral parent atoms in the heliospheric interface represents a new m…
Hubble Space Telescope Observations of Chromospheric Emission from the Population II Red Giant HD 216143
Smith, Graeme H.; Dupree, A. K.
Spectra of the Hα and Ca ii K line of Population II red giants exhibit evidence for chromospheric mass outflows only among stars brighter than M_V = -1.7. In order to determine whether this phenomenon is indicative of a true physical onset in mass outflow, spectra of the 2800 Å Mg ii lines of the metal-poor halo red giant HD 216143 have been obtai…
Latitudinal structure within Jovian hectometric radiation
Higgins, Charles A.; Thieman, James R.; Fung, Shing F. +2 more
Jovian hectometric radio emission (HOM: 300-3000 kHz) has a number of persistent structural features associated with it as observed by the Voyager 1, Voyager 2, Ulysses, and Galileo spacecraft for specific jovigraphic latitudes (-4° to +7.1°) and local times (0.3 to 10.5 hours). Most notable are the presence of HOM emission between 270° and 120° c…
The Variable Central Star of PN G243.8-37.1
Peña, Miriam; Ruiz, María Teresa
Spectroscopic and photometric variations of the central star of the planetary nebula PRTM 1 (PN G243.8-37.1) have been detected from optical spectrophotometric data. The photometric variations can be as large as ΔV~1 mag, but most of the time they are within 0.2 mag. The phenomenon seems to be cyclic. These optical changes confirm the UV variation…
Hubble Space Telescope/Faint Object Spectrograph Imaging of Wolf 424 AB: Is This Binary a Double Brown Dwarf System?
Benedict, G. F.; Franz, O. G.; Bruhweiler, F. C. +9 more
The low-mass binary system Wolf 424 AB (GJ 473 AB) was spatially resolved in an image obtained on 1996 April 16 with the imaging mode of the Hubble Space Telescope Faint Object Spectrograph. The separation was measured to be 0.42"+/-0.03" at a position angle of 353.2d+/-2.5d. The new measurement was combined with previously published orbital posit…
Search for H2 Emission from Disks around T Tauri and Herbig AE Stars
Thi, W. F.; van Dishoeck, E. F.; Blake, G. A. +4 more
Preliminary results are presented of observations of the pure rotational lines of H2 toward T Tauri and Herbig Ae stars using the Short Wavelength Spectrometer (SWS) on the Infrared Space Observatory (ISO). The sources are selected to be isolated low- and intermediate-mass young stellar objects, for which the presence of a circumstellar disk has b…
SBF distances to Leo and Virgo using the HST
Morris, P. W.; Shanks, T.
We use archive HST WFPC2 data for three elliptical galaxies (NGC 3379 in the Leo I group, and NGC 4472 and 4406 in the Virgo cluster) to determine their distances using the surface brightness fluctuation (SBF) method as described by Tonry & Schneider. A comparison of the HST results with the SBF distance moduli found by Ciardullo et al. shows …
Long-duration high-energy proton events observed by GOES in October 1989
Vainio, R.; Torsti, J.; Anttila, A. +1 more
We consider the prolonged injection of the high-energy (>10 MeV) protons during the three successive events observed by GOES in October 1989. We apply a solar-rotation-stereoscopy approach to study the injection of the accelerated particles from the CME-driven interplanetary shock waves in order to find out how the effectiveness of the particle…