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A Possible Mechanism for the Origin of Emerging Flux in the Sunspot Moat
Title, A.; Shine, R.; Sakai, J. I. +1 more
Mass and energy flow near sunspots are associated with the emergence of magnetic flux, which then moves outward in the sunspot moat. We present results of analytical and numerical studies of the interaction of horizontal magnetic flux and plasma flows in three-dimensional geometry. We show that nonlinear coupling of flux and plasma flows in the pr…
HST/GHRS Observations of the Velocity Structure of Interplanetary Hydrogen
Bertaux, Jean-Loup; Clarke, John T.; Lallement, Rosine +3 more
We present high-resolution spectra of the emission-line profile of inflowing interplanetary hydrogen atoms along lines of sight with the Earth orbital motion upwind (into the flow), downwind, and across the flow to Doppler-shift the line from the geocoronal emission. The line-center positions, in comparison with hot-model profiles, confirm that th…
Hubble Space Telescope WFPC2 Imaging of FS Tauri and Haro 6-5B
Ballester, Gilda E.; Krist, John E.; Crisp, David +14 more
We have observed the field of FS Tauri (Haro 6-5) with the Wide Field Planetary Camera 2 on the Hubble Space Telescope. Centered on Haro 6-5B and adjacent to the nebulous binary system of FS Tauri A there is an extended complex of reflection nebulosity that includes a diffuse, hourglass-shaped structure. H6-5B, the source of a bipolar jet, is not …
An Infrared Search for Star-forming Galaxies at Z > 2
Teplitz, Harry I.; Malkan, M.; McLean, I. S.
We report the cumulative results of an ongoing near-infrared search for redshifted Hα emission from normal galaxies at z > 2. An infrared search reduces the bias due to reddening. Using narrowband imaging with the Near Infrared Camera on the Keck I 10 m telescope, a survey area of almost 12 arcmin2 has been covered. Target regions we…
Isotopic Composition of Solar Wind Nitrogen: First In Situ Determination with the CELIAS/MTOF Spectrometer on board SOHO
Bochsler, P.; Geiss, J.; Ipavich, F. M. +6 more
Using the high-resolution Mass Time-of-Flight (MTOF) spectrometer of the Charge, Element, and Isotope Analysis System (CELIAS) experiment on board the Solar and Heliospheric Observatory (SOHO), we have determined the solar wind isotope abundance ratio 14N/15N = 200+/-55 (1 σ error), suggesting that the relative abundance of <…
Solar Wind at 6.8 Solar Radii from UVCS Observation of Comet C/1996Y1
Raymond, John C.; Ciaravella, A.; Fineschi, S. +10 more
The comet C/1996Y1, a member of the Kreutz family of Sun-grazing comets, was observed with the Ultraviolet Coronagraph Spectrometer (UVCS) aboard the Solar and Heliospheric Observatory (SOHO) satellite. The Lyα line profile and spatial distribution are interpreted in terms of the theory of bow shocks driven by mass-loading. At the time of the obse…
Is There a Difference in Luminosity between Field and Cluster RR Lyrae Variables?
Catelan, Marcio
Recent Hipparcos results have lent support to the idea that RR Lyrae variables in the halo field and in globular clusters differ in luminosity by ~0.2 mag. In this Letter, we study the pulsation properties of RR Lyrae variables in clusters with distances determined via main-sequence fitting to Hipparcos parallaxes for field subdwarfs and compare t…
The Far-Field Hubble Constant
Lauer, Tod R.; Ajhar, Edward A.; Postman, Marc +2 more
We used the Hubble Space Telescope to obtain surface brightness fluctuation (SBF) observations of four nearby brightest cluster galaxies (BCGs) to calibrate the BCG Hubble diagram of Lauer & Postman. This BCG Hubble diagram contains 114 galaxies covering the full celestial sphere and is volume-limited to 15,000 km s-1, providing exc…
Solar Cycle Onset Seen in SOHO Michelson Doppler Imager Seismic Data
Kosovichev, A. G.; Schou, J.; Dziembowski, W. A. +2 more
We have analyzed time changes in centroid frequencies and multiplet frequency splittings of solar oscillations determined with the Michelson Doppler Imager instrument (MDI) on SOHO. The data were divided into five consecutive 72 day sets covering the period from 1996 May 1 through 1997 April 25. We have detected a significant trend in the a4<…
Goddard High-Resolution Spectrograph Observations of Cool Low-Gravity Stars. IV. A Comparison of the K5 III stars α Tauri and γ Draconis
Brown, Alexander; Robinson, Richard D.; Carpenter, Kenneth G.
The Goddard High-Resolution Spectrograph (GHRS) has observed the K5 III star α Tau in the 2330 Å region on three separate occasions. These spectra show marked changes with time, with the UV continuum varying by a factor of 2, and with the emission lines changing in flux by 30% or more, with the amount of change dependent upon the opacity of the li…