Issue 10 Volume 41 May 16, 2003

The present report covers the third year of a grant which represents a direct continuation of NASA NAG5-4050, with the
same title as before. It is dedicated as before to the discovery and characterization of new astrophysical molecules. This year,
like the two before, has been extremely productive, yielding many new discoveries of astronomical interest at both radio and
optical wavelengths, and the publication or submission of the 15 papers listed below. Nearly all of these articles have or will
soon appear in the leading refereed journals of astrophysics, chemical physics, physics, or molecular spectroscopy. One is a
major invited review for Molecular Physics. One of our other invited reviews published in Spectrochimica Acta in 2001 was
recently awarded the Sir Harold Thompson Memorial Award, annually given to the best paper in that journal. During the past
year significant advances have been made by our group in the laboratory study of exotic silicon and carbon molecules of
astronomical interest. The most exciting discoveries include the pure silicon cluster Si3, several novel silicon hydrides, and
the detection of phenyl radical, CsH5, a fundamental reactive organic ring. In addition, the rotational spectra of many carbon
chains terminated with Si, N, O, and other heteroatoms have also been detected for the first time. The laboratory astrophysics
of the whole set is complete in the sense that the entire radio spectrum of each species has now been measured or can be
calculated to very high accuracy. Nearly all of these newly found molecules are plausible candidates for the detection by radio
astronomers in the interstellar gas or in circumstellar sources because they are similar in structure and composition to known
astronomical species, and because most are calculated to possess large permanent dipole moments.
Author
Molecular Spectroscopy; Interstellar Gas; Molecular Clouds; Radio Astronomy; Radio Spectra; Visible Spectrum; Rotational
Spectra
20030033078 Smithsonian Astrophysical Observatory, Cambridge, MA, USA
RXTE Observations of the Outburst of the Dwarf Nova SS Cyg and VW Hyi and XTE Observations of the Precessing
Disk CV TV Col
Oliversen, Ronald J., Technical Monitor; April 2003; 2 pp.; In English
Contract(s)/Grant(s): NAG5-9107; No Copyright; Avail: CASI; A01, Hardcopy
A final report on the Rossi X Ray Timing Explorer (RXTE) Observations of outbursts SS Cyg and VW Hyi dwarf novae
are presented, along with observations of the Precessing Disk CV TV Col using the XTE.
CASI
Cygnus Constellation; X Ray Timing Explorer; Dwarf Novae; Astrophysics; Observation; Cataclysmic Variables
20030033920 Space Telescope Science Inst., Baltimore, MD, USA
Small-Scale Interstellar Structure Toward the Open Cluster CHI Persei-Fuse II
Sonneborn, George, Technical Monitor; Friedman, Scott; April 29, 2003; 4 pp.; In English
Contract(s)/Grant(s): NAG5-12639; STScI Proj. J01025; No Copyright; Avail: CASI; A01, Hardcopy
The purpose of this study was to measure the physical conditions of gas along sight lines toward 6 stars in the core Chi
Persei open cluster. These sight lines traverse gas in both the Orion and Perseus spiral arms of the Galaxy, at distances of 500
and 2000 pc, respectively. The stars have angular separations ranging from 45 to 280 arcsec; 60 arcsec corresponds to linear
distances of 0.15 and 0.6 pc in the two arms. Thus, abundance variations in these observations would constitute evidence for
small-scale variations in the properties of the interstellar medium. Ground-based Na I observations at high resolution (approx.
15 km/sec) toward 172 stars (including the 6 in this study) in the double open cluster h and Chi Persei have revealed complex
spatial variation. These variations are especially evident in the gas at velocities of -40 and -55 km/sec, corresponding to the
Perseus spiral arm. 21 cm observations of HI emission using the Low Resolution DRAO Survey, with a 12-arcmin beam, also
show variations. Averaging the Na I apparent optical depth profiles of neighboring sight lines in order to mimic such a beam
size reduces the variation, as compared to the individual Na I measurements, but still show variations larger than seen in the
21 cm profiles. Na I is not the dominant ionization state of Na in the interstellar medium. Thus, it is possible that the variations
seen really trace physical structures in the interstellar medium, or they may simply result from variations in the radiation field
seen by the gas, or be due to some other environmental circumstance. To distinguish among these possibilities in the present
study we obtained FUSE spectra toward the 6 targets in order to measure the molecular hydrogen absorption profiles along
these sight lines. The higher J states of H2 are populated by the ambient W radiation field, and thus can provide insight into
the environment affecting the gas. If both the high and low J states reveal absorption line profiles with variations similar to
that observed in Na I, this would indicate that the variations are due to real structures in the interstellar medium. On the other
hand, if the only the high J profiles mimicked the Na I profiles, then the variations may be attributable to environmental effects.
We found that the H2 profiles showed considerable variation over the 6 sight lines, and that the profiles, despite having
somewhat lower velocity resolution, resemble the Na I profiles. Thus, it appears that the gas really does exhibit variations in
physical structures along these sight lines. Useful follow-up work would be to obtain higher signal-to-noise FUSE
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