Search Publications
Hot HB stars in globular clusters: physical parameters and consequences for theory III. NGC 6752 and its long blue vertical branch.
Heber, U.; Moehler, S.; Rupprecht, G.
We present spectroscopic analyses of 17 faint blue stars in the globular cluster NGC 6752, using optical and UV spectrophotometric data and intermediate resolution optical spectra. Effective temperatures, surface gravities, and helium abundances of the stars are determined and compared to theoretical predictions. All stars are helium deficient by …
A One-sided Ionization Cone in the Seyfert 2 Galaxy NGC 5643
Simpson, Chris; Krolik, J. H.; Wilson, A. S. +3 more
We present high-resolution (0.1") observations of the Seyfert 2 galaxy NGC 5643 taken with the WFPC2 on board the Hubble Space Telescope. Images taken in the light of [O III] λ5007 and Hα reveal a halo of emission centered on the nucleus and high-excitation extranuclear emission which extends eastward for at least 1.8 kpc. An excitation map of [O …
Detection of the Tip of the Red Giant Branch in NGC 3379 (M105) in the Leo I Group Using the Hubble Space Telescope
Madore, Barry F.; Freedman, Wendy L.; Lauer, Tod R. +3 more
We report the detection of individually resolved stars in the elliptical galaxy NGC 3379, a luminous member of the Leo I Group. The bright end of the stellar luminosity function has a logarithmic slope that is consistent with these stars being Population II red giants. An abrupt discontinuity in the apparent luminosity function at I = 26.30 +/- 0.…
Detection of [O I] 63µm in absorption toward SGR B2.
Prusti, T.; Liseau, R.; Burgdorf, M. +26 more
A high signal-to-noise 52-90µm spectrum is presented for the central part of the Sagittarius B2 complex. The data were obtained with the Long Wavelength Spectrometer on board the Infrared Space Observatory (ISO). The [O I] 63µm line is detected in absorption even at the grating spectral resolution of 0.29µm. A lower limit for the…
SS 433 in the ultraviolet.
Dolan, J. F.; Boyd, P. T.; Fabrika, S. +8 more
The High Speed Photometer (HSP) on the Hubble Space Telescope observed SS 433 at 15 different epochs between 1993 May and November. Polarimetric observations were obtained in a 340Å FWHM bandpass centered at 2770Å; photometric observations were made in a bandpass extending between 1400 and 3000Å. The polarization in the UV is both large (
=13…Improved Parameters and New Lensed Features for Q0957+561 from WFPC2 Imaging
Tyson, J. Anthony; Fischer, Philippe; Bernstein, Gary +1 more
New Hubble Space Telescope WFPC2 observations of the lensed double QSO 0957+561 will allow stronger constraints on the lens mass distribution and hence will refine the derived value of H0. We first present improved optical positions and photometry for the known components of this lens. The optical separation between the A and B quasar i…
Tri-Phonic Helioseismology: Comparison of Solar P Modes Observed by the Helioseismology Instruments Aboard SOHO
Henney, C. J.; Hoeksema, J. T.; Baudin, F. +17 more
The three helioseismology instruments aboard SOHO observe solar p modes in velocity (GOLF and MDI) and in intensity (VIRGO and MDI). Time series of two months duration are compared and confirm that the instruments indeed observe the same Sun to a high degree of precision. Power spectra of 108 days are compared showing systematic differences betwee…
MHD Interpretation of LASCO Observations of a Coronal Mass Ejection as a Disconnected Magnetic Structure
Llebaria, A.; Michels, D. J.; Koomen, M. J. +15 more
We present a qualitative and quantitative comparison of a single coronal mass ejection (CME) as observed by LASCO (July 28-29, 1996) with the results of a three-dimensional axisymmetric time-dependent magnetohydrodynamic model of a flux rope interacting with a helmet streamer. The particular CME considered was selected based on the appearance of a…
Extension of coronal structure into interplanetary space
Habbal, Shadia Rifai; Woo, Richard
We investigate the extension and evolution of the solar corona into interplanetary space by comparing 1995 Ulysses radio occultation measurements of path-integrated electron density and density fluctuations measured between 21 and 32 Ro, with simultaneous white-light measurements made by the HAO Mauna Loa K-coronameter below 2.5 Ro…
A Linear Relationship between the Latitude Gradient and 26 Day Recurrent Variation in the Fluxes of Galactic Cosmic Rays and Anomalous Nuclear Components. I. Observations
Zhang, Ming
We find that there exists a linear relationship between the magnitude of latitude gradient and the amplitude of 26 day recurrent variations in the fluxes of galactic cosmic rays and anomalous nuclear components. This result is based on energetic charged particle measurements from the University of Chicago High Energy Telescope (HET) in the Cosmic …