73 research outputs found
The interstellar medium toward the Galactic center source 2MASS J17470898-2829561
Interstellar matter and star formatio
Ground-based detection of a vibration-rotation line of HD in Orion
The v =1-0 R(5) line of HD at 2.46um has been detected at the position of
brightest line emission of shocked H2 in the Orion Molecular Cloud. The flux in
this HD line, when compared to that of the previously detected HD 0--0 R(5)
line at 19.43um, suggests that, like the v=1 levels of H2, the v=1 levels of HD
are populated in LTE, despite their much higher rates of spontaneous emission
compared to H2. The higher than expected population of vibrationally excited HD
may be due to chemical coupling of HD to H2 via the reactive collisions HD + H
H2 + D in the shocked gas. The deuterium abundance implied by the
strengths of these lines relative to those of H2 is (5.1 pm 1.9 x 10^-6.Comment: 9 pages, 2 figures, Proceedings of the Conference on "Deuterium in
the Universe," to be published in Planetary and Space Science
Methanol: The second most abundant ice species towards the high-mass protostars RAFGL7009S and W 33A
Infrared Space Observatory and Ground-Based Infrared Observation of the Classical Nova V723 Cassiopeiae
We present observations of the classical nova V723 Cassiopeiae (Nova Cas 1995), obtained both with the Infrared Space Observatory (ISO) and from the ground. The infrared spectrum was dominated in the first year by H and He recombination lines, and at later times by coronal lines. The H recombination lines imply a reddening of E(B-V) = 0.78, an electron temperature of 7000 K, and an electron density of 2 × 108 cm-3 on day 250. We argue that the high-ionization species in the infrared are most likely the result of collisional ionization rather than photoionization and are therefore truly "coronal"; we estimate a temperature of 3.2 × 105 K in the coronal region and abundance ratios of S/Si 2.1, Ca/Si 1.6, and Al/Si 1.5. The ejected mass as determined from the Brα line was 2.6 × 10-5 M⊙ for a distance of 4 kpc; however, the mass deduced from the free-free emission, which we conclude arises primarily in the coronal zone, is 4.3 × 10-4 M⊙. V723 Cas did not display the [O IV] 25.89 μm fine-structure line, which was typically seen in the spectra of novae observed with ISO. There was no evidence of dust emission in V723 Cas
Observational diagnostics of gas in protoplanetary disks
Protoplanetary disks are composed primarily of gas (99% of the mass).
Nevertheless, relatively few observational constraints exist for the gas in
disks. In this review, I discuss several observational diagnostics in the UV,
optical, near-IR, mid-IR, and (sub)-mm wavelengths that have been employed to
study the gas in the disks of young stellar objects. I concentrate in
diagnostics that probe the inner 20 AU of the disk, the region where planets
are expected to form. I discuss the potential and limitations of each gas
tracer and present prospects for future research.Comment: Review written for the proceedings of the conference "Origin and
Evolution of Planets 2008", Ascona, Switzerland, June 29 - July 4, 2008. Date
manuscript: October 2008. 17 Pages, 6 graphics, 134 reference
Herschel/HIFI measurements of the ortho/para ratio in water towards Sagittarius B2(M) and W31C
We present Herschel/HIFI observations of the fundamental rotational transitions of ortho- and para-H16
2 O and H18
2 O in absorption towards
Sagittarius B2(M) and W31C. The ortho/para ratio in water in the foreground clouds on the line of sight towards these bright continuum sources is
generally consistent with the statistical high-temperature ratio of 3, within the observational uncertainties. However, somewhat unexpectedly, we
derive a low ortho/para ratio of 2.35±0.35, corresponding to a spin temperature of ∼27 K, towards Sagittarius B2(M) at velocities of the expanding
molecular ring. Water molecules in this region appear to have formed with, or relaxed to, an ortho/para ratio close to the value corresponding to
the local temperature of the gas and dust
Large Scale Searches for Brown Dwarfs and Free-Floating Planets
Searches of large scale surveys have resulted in the discovery of over 1000
brown dwarfs in the Solar neighbourhood. In this chapter we review the progress
in finding brown dwarfs in large datasets, highlighting the key science goals,
and summarising the surveys that have contributed most significantly to the
current sample.Comment: Accepted to appear in the Handbook of Exoplanets (Springer); Editors:
Hans J. Deeg & Juan Antonio Belmont
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