NASA Scientific and Technical Aerospace Reports

20040121010 Space Telescope Science Inst., Baltimore, MD, USA
The Formation Mechanism of Helium-Rich Subdwarf B Stars
Luers, Jeannine N.; September 23, 2004; 2 pp.; In English
Contract(s)/Grant(s): NAG5-12314; STScI Proj. J1004; No Copyright; Avail: CASI; A01, Hardcopy
This program used the Far Ultraviolet Spectroscopic Explorer (FUSE) to measure the surface abundances of three
helium-rich hot subdwarfs in the Galactic field, to test our hypothesis that such stars form via a late helium flash while
descending the white dwarf cooling curve. If these stars form via a late He flash, the stellar envelope should be mixed with
the interior, enhancing the surface carbon abundance enormously while depleting the surface hydrogen. The first observation
of PG1544+488 was incomplete because detector 2 was turned off, but the repeat observations were fully successful. The
observations of LB1766 had no problems and were fully successful. The observations of PG1127+019 became infeasible when
FUSE lost some of its pointing control, so it was replaced with JL87, which was also observed successfully.
Derived from text
Subdwarf Stars; Stellar Envelopes; Hydrogen; Helium
20040121117 NASA Marshall Space Flight Center, Huntsville, AL, USA
Five Years of Operation of the Chandra X-Ray Observatory
Weisskopf, Martin C.; [2004]; 1 pp.; In English; Astronomial Telescopes and Instrumentation 2004, 21-25 Jun. 2004,
Glasgow, Scotland, UK; Original contains black and white illustrations; No Copyright; Avail: CASI; A01, Hardcopy
The on-orbit performance of the Chandra X-ray Observatory over its first five years of operation is reviewed. The
Observatory is running smoothly and the scientific return continues to be outstanding.
Author
X Ray Astrophysics Facility; Spaceborne Astronomy; NASA Space Programs
20040121118 NASA Marshall Space Flight Center, Huntsville, AL, USA
Eruption of a Multiple-Turn Helical Magnetic Flux Tube in a Large Flare: Evidence for External and Internal
Reconnection that Fits the Breakout Model of Solar Magnetic Eruptions
Gary, G. Allen; Moore, R. L.; Astrophysical Journal; Aug. 10, 2004; Volume 611, pp. 545-556; In English; Original contains
black and white illustrations; Copyright; Avail: Other Sources
We present observations and an interpretation of a unique multiple-turn spiral flux tube eruption from active region 10030
on 2002 July 15. The TRACE C IV observations clearly show a flux tube that is helical and erupting from within a sheared
magnetic field. These observations are interpreted in the context of the breakout model for magnetic field explosions. The
initiation of the helix eruption. as determined by a linear backward extrapolation, starts 25 s after the peak of the flare’s
strongest impulsive spike of microwave gyrosynchrotron radiation early in the flare s explosive phase, implying that the
sheared core field is not the site of the initial reconnection. Within the quadrupolar configuration of the active region, the
external and internal reconnection sites are identified in each of two consecutive eruptive flares that produce a double coronal
mass ejection (CME). The first external breakout reconnection apparently releases an underlying sheared core field and allows
it to erupt, leading to internal reconnection in the wake of the erupting helix. This internal reconnection releases the helix and
heats the two-ribbon flare. These events lead to the first CME and are followed by a second breakout that initiates a second
and larger halo CME. The strong magnetic shear in the region is compatible with the observed rapid proper motion and
evolution of the active region. The multiple-turn helix originates from above a sheared-field magnetic inversion line within
a filament channel. and starts to erupt only after fast breakout reconnection has started. These observations are counter to the
standard flare model and support the breakout model for eruptive flare initiation.
Author
Coronal Mass Ejection; Sun; Transition Region and Coronal Explorer; Magnetic Flux; Solar Flares; Magnetic Field
Reconnection
20040121121 NASA Marshall Space Flight Center, Huntsville, AL, USA
Long-Term Spectral and Timing Behavior of the Black Hole Candidate XTE J1908+094
Gogus, Ersin; Finger, Mark H.; Kouveliotou, Chryssa; Woods, Peter M.; Patel, Sandeep K.; Ruppen, Michael; Swank, Jean
H.; Markwardt, Craig B.; VanDerKlis, Michiel; Astrophysical Journal; July 10, 2004; Volume 609, pp. 977-987; In English;
Original contains black and white illustrations
Contract(s)/Grant(s): NAG5-3370; Copyright; Avail: CASI; A03, Hardcopy
We present the long-term X-ray light curves and detailed spectral and timing analyses of XTE J1908+094 using the Rossi
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