102 research outputs found
Rydberg-Klein-Rees 1-Sigma-positive potential curve turning points for the isotopes of carbon monoxide
First order RKR turning points were computed for (C-12)O16, (C-12)O17, (C-13)O16, (C-12)O18, and (C-13)O18 for vibrational levels up to v = 40. These turning points should be useful in the numerical computation of matrix elements of powers of the internuclear separation
Combined effects of a converging beam of light and mirror misalignment in Michelson interferometry
Expressions have been derived and calculations have been made which show that combined effects lead to asymmetric interferograms and reduction in power at zero path difference. Criteria are given for estimating maximum allowable mirror misalignment
Are the aerosols on Uranus and Neptune composed of methane photopolymers?
The measured optical properties of photochemically produced aerosols in an adding-doubling radiative transfer code were used to match various points in the spectra of Uranus and Neptune. How well these points are fit are shown by different assumptions regarding the size and distribution of these aerosols in the Uranus and Neptune atmospheres. The consistency of these derived distributions with those expected from computations of the sedimentation rate of such aerosols is discussed
Laser-generated plasma as a spectroscopic light source
Laser generated plasma as spectroscopic light sourc
Observations of the J = 10 manifold of the pure rotational band of phosphine on Saturn
Saturn was observed in the vicinity of the J = 10 manifold of the pure rotational band of phosphine on 1984 July 10 and 12 from NASA's Kuiper Airborne Observatory with the facility far-infrared cooled grating spectrometer. On each night observations of the full disk plus rings were made at 4 to 6 discrete wavelengths which selectively sampled the manifold and the adjacent continuum. The previously reported detection of this manifold is confirmed. After subtraction of the flux due to the rings, the data are compared with disk-averaged models of Saturn. It is found that PH3 must be strongly depleted above the thermal inversion (approx. 70 mbar). The best fitting models consistent with other observational constaints indicate that PH3 is significantly depleted at even deeper atmospheric levels ( or = 500 mbar), implying an eddy diffusion coefficient for Saturn of 10 to the 4 cm sq/sec
Quantitative infrared spectroscopy of minor constituents of the Earth's atmosphere
We obtain quantitative laboratory spectroscopic measurements of molecular constituents which are of importance in understanding the health of the Earth's atmosphere, and, in particular, emphasize those species which are important for understanding stratospheric kinetics or are used for long term monitoring of the stratosphere. Our measurements provide: (1) line and band intensity values which are needed to establish limits of detectability for as yet unobserved species and to quantify the abundance of those species which are observed; (2) line-positions, -half widths and pressure induced shifts are all needed for remote sensing techniques, and (3) data on the above basic molecular parameters at temperatures and pressures appropriate for the real atmosphere
Near-IR Spectra of Red Supergiants and Giants. I- Models with Solar and with Mixing-Induced Surface Abundance Ratios
We provide a grid of PHOENIX spectra of red giant and supergiant stars, that
extend through optical and near-IR wavelengths. For the first time, models are
also provided with modified surface abundances of C, N and O, as a step towards
accounting for the changes known to occur due to convective dredge-up (and to
be enhanced in the case of rotation). The aims are (i) to assess how well
current models reproduce observed spectra, (ii) to quantify the effects of the
abundance changes on the spectra, and (iii) to determine how these changes
affect estimates of fundamental stellar parameters.
Observed giant star spectra can be fitted very well at solar metallicity down
to about 3400K. Modified surface abundances are preferred in only a minority of
cases for luminosity class II, possibly indicating mixing in excess of standard
first dredge-up.
Supergiant stars show a larger variety of near-IR spectra, and good fits are
currently obtained for about one third of the observations only. Modified
surface abundances help reproducing strong CN bands, but do not suffice to
resolve all the difficulties. The effect of the abundance changes on the
estimated Teff depends on the wavelength range of observation and can amount
several 100K. Reasons for the remaining discrepancies are discussed.Comment: To be published in A&A. 19 p., 35 postscript figures, uses aa.cls.
Selected model spectra available through CD
High-resolution infrared spectroscopy as a tool to detect false positives of transit search programs
Transit search programs such as CoRoT and Kepler now have the capability of
detecting planets as small as the Earth. The detection of these planets however
requires the removal of all false positives. Although many false positives can
be identified by a detailed analysis of the LCs, the detections of others
require additional observations. An important source of false positives are
faint eclipsing binaries within the PSF of the target stars. We develop a new
method that allows us to detect faint eclipsing binaries with a separation
smaller than one arcsec from target stars. We thereby focus on binaries that
mimic the transits of terrestrial planets. These binaries can be either at the
same distance as the target star (triple stars), or at either larger, or
smaller distances. A close inspection of the problem indicates that in all
relevant cases the binaries are brighter in the infrared than in the optical
regime. We show how high resolution IR spectroscopy can be used to remove these
false positives. For the triple star case, we find that the brightness
difference between a primary and an eclipsing secondary is about 9-10 mag in
the visual but only about 4.5-5.9 magnitudes in the K-band. We demonstrate how
the triple star hypothesis can be excluded by taking a high-resolution IR
spectrum. Simulations of these systems show that the companions can be detected
with a false-alarm probability of 2%, if the spectrum has a S/N-ratio > 100. We
show that high-resolution IR spectra also allows to detect most of the false
positives caused by foreground or background binaries. If high resolution IR
spectroscopy is combined with photometric methods, virtually all false
positives can be detected without RV measurements. It is thus possible to
confirm transiting terrestrial planets with a modest investment of observing
time.Comment: 6 pages, 7 figure
Sakurai's Object: characterizing the near-infrared CO ejecta between 2003 and 2007
We present observations of Sakurai's Object obtained at 1–5 μm between 2003 and 2007. By fitting a radiative transfer model to an echelle spectrum of CO fundamental absorption features around 4.7 μm, we determine the excitation conditions in the line-forming region. We find 12C/13C = 3.5+2.0−1.5, consistent with CO originating in ejecta processed by the very late thermal pulse, rather than in the pre-existing planetary nebula. We demonstrate the existence of 2.2 × 10−6≤MCO≤ 2.7 × 10−6 M⊙ of CO ejecta outside the dust, forming a high-velocity wind of 500 ± 80 km s−1. We find evidence for significant weakening of the CO band and cooling of the dust around the central star between 2003 and 2005. The gas and dust temperatures are implausibly high for stellar radiation to be the sole contributor
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