3,577 research outputs found
Solar Carbon Monoxide, Thermal Profiling, and the Abundances of C, O, and their Isotopes
A solar photospheric "thermal profiling" analysis is presented, exploiting
the infrared rovibrational bands of carbon monoxide (CO) as observed with the
McMath-Pierce Fourier transform spectrometer (FTS) at Kitt Peak, and from above
the Earth's atmosphere by the Shuttle-borne ATMOS experiment. Visible continuum
intensities and center-limb behavior constrained the temperature profile of the
deep photosphere, while CO center-limb behavior defined the thermal structure
at higher altitudes. The oxygen abundance was self consistently determined from
weak CO absorptions. Our analysis was meant to complement recent studies based
on 3-D convection models which, among other things, have revised the historical
solar oxygen (and carbon) abundance downward by a factor of nearly two;
although in fact our conclusions do not support such a revision. Based on
various considerations, an oxygen abundance of 700+/-100 ppm (parts per million
relative to hydrogen) is recommended; the large uncertainty reflects the model
sensitivity of CO. New solar isotopic ratios also are reported for 13C, 17O,
and 18O.Comment: 90 pages, 19 figures (some with parts "a", "b", etc.); to be
published in the Astrophysical Journal Supplement
Visualization techniques to aid in the analysis of multispectral astrophysical data sets
The goal of this project was to support the scientific analysis of multi-spectral astrophysical data by means of scientific visualization. Scientific visualization offers its greatest value if it is not used as a method separate or alternative to other data analysis methods but rather in addition to these methods. Together with quantitative analysis of data, such as offered by statistical analysis, image or signal processing, visualization attempts to explore all information inherent in astrophysical data in the most effective way. Data visualization is one aspect of data analysis. Our taxonomy as developed in Section 2 includes identification and access to existing information, preprocessing and quantitative analysis of data, visual representation and the user interface as major components to the software environment of astrophysical data analysis. In pursuing our goal to provide methods and tools for scientific visualization of multi-spectral astrophysical data, we therefore looked at scientific data analysis as one whole process, adding visualization tools to an already existing environment and integrating the various components that define a scientific data analysis environment. As long as the software development process of each component is separate from all other components, users of data analysis software are constantly interrupted in their scientific work in order to convert from one data format to another, or to move from one storage medium to another, or to switch from one user interface to another. We also took an in-depth look at scientific visualization and its underlying concepts, current visualization systems, their contributions and their shortcomings. The role of data visualization is to stimulate mental processes different from quantitative data analysis, such as the perception of spatial relationships or the discovery of patterns or anomalies while browsing through large data sets. Visualization often leads to an intuitive understanding of the meaning of data values and their relationships by sacrificing accuracy in interpreting the data values. In order to be accurate in the interpretation, data values need to be measured, computed on, and compared to theoretical or empirical models (quantitative analysis). If visualization software hampers quantitative analysis (which happens with some commercial visualization products), its use is greatly diminished for astrophysical data analysis. The software system STAR (Scientific Toolkit for Astrophysical Research) was developed as a prototype during the course of the project to better understand the pragmatic concerns raised in the project. STAR led to a better understanding on the importance of collaboration between astrophysicists and computer scientists. Twenty-one examples of the use of visualization for astrophysical data are included with this report. Sixteen publications related to efforts performed during or initiated through work on this project are listed at the end of this report
Visualization techniques to aid in the analysis of multi-spectral astrophysical data sets
The goal of this project was to support the scientific analysis of multi-spectral astrophysical data by means of scientific visualization. Scientific visualization offers its greatest value if it is not used as a method separate or alternative to other data analysis methods but rather in addition to these methods. Together with quantitative analysis of data, such as offered by statistical analysis, image or signal processing, visualization attempts to explore all information inherent in astrophysical data in the most effective way. Data visualization is one aspect of data analysis. Our taxonomy as developed in Section 2 includes identification and access to existing information, preprocessing and quantitative analysis of data, visual representation and the user interface as major components to the software environment of astrophysical data analysis. In pursuing our goal to provide methods and tools for scientific visualization of multi-spectral astrophysical data, we therefore looked at scientific data analysis as one whole process, adding visualization tools to an already existing environment and integrating the various components that define a scientific data analysis environment. As long as the software development process of each component is separate from all other components, users of data analysis software are constantly interrupted in their scientific work in order to convert from one data format to another, or to move from one storage medium to another, or to switch from one user interface to another. We also took an in-depth look at scientific visualization and its underlying concepts, current visualization systems, their contributions, and their shortcomings. The role of data visualization is to stimulate mental processes different from quantitative data analysis, such as the perception of spatial relationships or the discovery of patterns or anomalies while browsing through large data sets. Visualization often leads to an intuitive understanding of the meaning of data values and their relationships by sacrificing accuracy in interpreting the data values. In order to be accurate in the interpretation, data values need to be measured, computed on, and compared to theoretical or empirical models (quantitative analysis). If visualization software hampers quantitative analysis (which happens with some commercial visualization products), its use is greatly diminished for astrophysical data analysis. The software system STAR (Scientific Toolkit for Astrophysical Research) was developed as a prototype during the course of the project to better understand the pragmatic concerns raised in the project. STAR led to a better understanding on the importance of collaboration between astrophysicists and computer scientists
Reversal-free CaIIH profiles: a challenge for solar chromosphere modeling in quiet inter-network
We study chromospheric emission to understand the temperature stratification
in the solar chromosphere. We observed the intensity profile of the CaIIH line
in a quiet Sun region close to the disk center at the German Vacuum Tower
Telescope. We analyze over 10^5 line profiles from inter-network regions. For
comparison with the observed profiles, we synthesize spectra for a variety of
model atmospheres with a non local thermodynamic equilibrium (NLTE) radiative
transfer code. A fraction of about 25% of the observed CaIIH line profiles do
not show a measurable emission peak in H_{2v} and H_{2r} wavelength bands
(reversal-free). All of the chosen model atmospheres with a temperature rise
fail to reproduce such profiles. On the other hand, the synthetic calcium
profile of a model atmosphere that has a monotonic decline of the temperature
with height shows a reversal-free profile that has much lower intensities than
any observed line profile. The observed reversal-free profiles indicate the
existence of cool patches in the interior of chromospheric network cells, at
least for short time intervals. Our finding is not only in conflict with a
full-time hot chromosphere, but also with a very cool chromosphere as found in
some dynamic simulations.Comment: 8 pages, accepted in A&
A Study of Wavelength Calibration of NEWSIPS High-Dispersion Spectra
In this study we cross-correlate many IUE echellograms of a variety of stars
to evaluate systematic error sources in the wavelength zeropoint of all three
cameras. We first evaluated differences between the final archived ("NEWSIPS")
and the originally processed ("IUESIPS") spectra. These show a clear time
dependence in zeropoint for the SWP camera due to revisions in the IUESIPS
wavelength scale. Small IUESIPS - NEWSIPS differences are also found for the
LWR camera. We also examined wavelength zeropoint disparities between data
obtained both through the small and large entrance apertures and for
observations made by different target acquisition modes for faint and bright
stars. We found that velocities resulting from these alternative observing
modes are nil. For large-aperture observations the dominant error source is the
target position placement in the aperture. We searched for spurious trends with
time, and found only a suggestion of time trends for faint stars observed with
the SWP camera. We also discovered 1-day, +/-3 km/s sinusoidsal patterns in
intensive monitoring data which are ascribable to changes in telescope focus
resulting from thermal drifts. In the second part of the paper, we measured
mean zeropoint errors of NEWSIPS echellogram data against laboratory results by
using the GHRS spectral atlas of the 10 Lac. We find that the derived apparent
velocity difference for this star is -1 +/-3.5 km/s. Several less precise
comparisons lead to similar results. The zeropoints of the NEWSIPS-processed
LWP/LWR cameras are evaluated and are also found to be nearly zero (+/-5 km/s)
relative to HST atlases of Arcturus and Procyon atlas. These results do not
support result by Gonzalez-Riestra et al. that corrections should be introduced
to the wavelength scales of various NEWSIPS high-dispersion data products.Comment: 16 pages, Latex with 12 figures, Accepted by Pub. Astron. Soc.
Pacific for July 1, 2001. Files available from
ftp://nobel.stsci.edu/pub/iuerv
The extreme O-type spectroscopic binary HD 93129A
HD 93129A was classified as the earliest O-type star in the Galaxy (O2~If*)
and is considered as the prototype of its spectral class. However,
interferometry shows that this object is a binary system, while recent
observations even suggest a triple configuration. None of the previous spectral
analyses of this object accounted for its multiplicity. With new
high-resolution UV and optical spectra, we have the possibility to reanalyze
this key object, taking its binary nature into account for the first time. We
aim to derive the fundamental parameters and the evolutionary status of HD
93129A, identifying the contributions of both components to the composite
spectrum. We analyzed UV and optical observations acquired with the Hubble
Space Telescope and ESO's Very Large Telescope. A multiwavelength analysis of
the system was performed using the latest version of the Potsdam Wolf-Rayet
model atmosphere code. Despite the similar spectral types of the two
components, we are able to find signatures from each of the components in the
combined spectrum, which allows us to estimate the parameters of both stars. We
derive , kK, and for the primary Aa, and , kK, and for the secondary Ab. Even when accounting for the
binary nature, the primary of HD 93129A is found to be one of the hottest and
most luminous O stars in our Galaxy. Based on the theoretical decomposition of
the spectra, we assign spectral types O2~If* and O3~III(f*) to components Aa
and Ab, respectively. While we achieve a good fit for a wide spectral range,
specific spectral features are not fully reproduced. The data are not
sufficient to identify contributions from a hypothetical third component in the
system.Comment: 16 pages, 20 figures, accepted for publication in Astronomy &
Astrophysics, typos corrected by language edito
Influence of seasonality on ovulatory follicular wave dynamic in long protocols in Santa Inês sheep in the tropics.
Edição dos proceedings da Annual Conference or the International Embryo Transfer Society, Orlando, Florida, 2011
Long-Slit Observations of Extended C II 1335 Emission Around V854 Centauri and RY Sagittarii
We have obtained long-slit far-ultraviolet (1150--1730 A) spectra of the R
Coronae Borealis (RCB) stars V854 Cen and RY Sgr, near maximum light and
pulsational phase zero, with the Space Telescope Imaging Spectrograph (STIS) on
Hubble Space Telescope (HST). The far-UV spectrum of each star shows a
photospheric continuum rising steeply toward longer wavelengths, and a
prominent emission feature at C II 1335. RY Sgr displays a second, but fainter,
emission attributed to Cl I 1351 (which is radiatively fluoresced by C II
1335), but Cl I is weak or absent in V854 Cen. Most surprisingly, the C II
emission of V854 Cen is significantly extended along the slit by +/- 2.5
arcsec, about 6 x 10^3 AU at the distance of the star. The C II feature of RY
Sgr exhibits no such gross extension. Nevertheless, subtle broadenings of the C
II emissions beyond the point response profile suggests inner clouds of radius
\~0.1 arcsec (250 AU) around both stars. V854 Cen is only the third RCB star
after R CrB and UW Cen known to have a resolved shell.Comment: 15 pages, 2 figures, (Figure 1 is a jpeg file), ApJ, in pres
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