scholarly journals Deuterium Observations in our Galaxy - View A

2000 ◽  
Vol 198 ◽  
pp. 141-150 ◽  
Author(s):  
Jeffrey L. Linsky ◽  
Brian E. Wood
Keyword(s):  
Chemical Evolution ◽  
Systematic Errors ◽  
Interstellar Cloud ◽  
The Sun ◽  
Galactic Chemical Evolution ◽  
Late Type ◽  
High Quality ◽  
Ultraviolet Spectra ◽  
Local Interstellar Cloud ◽  
Very High

Accurate measurements of the D/H ratio in our Galaxy provide critical tests of Galactic chemical evolution and constrain the primordial value of D/H. Very high quality ultraviolet spectra from the GHRS and STIS instruments on HST have been analyzed for lines of sight toward both early and late-type stars and hot white dwarfs. We will summarize the results that are being obtained for D/H along sightlines through the Local Interstellar Cloud (LIC) and other nearby warm clouds. All sightlines through the LIC are consistent with D/H = (1.53 ± 0.18) × 10−5. Whether or not significantly different values of D/H are present in other clouds within 100 pc of the Sun is not yet settled, but there is evidence that D/H is significantly lower in Orion (500 pc). We will describe the likely sources of systematic errors in determining D/H that must be understood and quantified when analyzing such ultraviolet spectra.

scholarly journals Volatiles and refratories in solar analogs: No terrestial planet connection

2010 ◽  
Vol 6 (S276) ◽  
pp. 422-423 ◽  
Author(s):  
Jonay I. González Hernández ◽  
Garik Israelian ◽  
Nuno C. Santos ◽  
Sergio Sousa ◽  
Elisa Delgado-Mena ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Planetary Systems ◽  
Galactic Chemical Evolution ◽  
Chemical Abundances ◽  
Volatile Elements ◽  
High Quality ◽  
Refractory Elements ◽  
Solar Abundances ◽  
Solar Analogs ◽  
Very High

AbstractWe have analysed very high-quality HARPS and UVES spectra of 95 solar analogs, 24 hosting planets and 71 without detected planets, to search for any possible signature of terrestial planets in the chemical abundances of volatile and refractory elements with respect to the solar abundances.We demonstrate that stars with and without planets in this sample show similar mean abundance ratios, in particular, a sub-sample of 14 planet-host and 14 “single” solar analogs in the metallicity range 0.14 < [Fe/H] < 0.36. In addition, two of the planetary systems in this sub-sample, containing each of them a super-Earth-like planet with masses in the range ~ 7-11 Earth masses, have different volatile-to-refratory abundance ratios to what would be expected from the presence of a terrestial planets.Finally, we check that after removing the Galactic chemical evolution effects any possible difference in mean abundances, with respect to solar values, of refratory and volatile elements practically dissappears.

Developing an astrophysical line list for Keck/Nirspec observations of red giants in the Galactic centre

2017 ◽  
Vol 13 (S334) ◽  
pp. 372-373 ◽  
Author(s):  
B. Thorsbro ◽  
N. Ryde ◽  
R. M. Rich ◽  
M. Schultheis ◽  
T. K. Fritz ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Wavelength Region ◽  
Galactic Centre ◽  
Red Giants ◽  
The Sun ◽  
Galactic Chemical Evolution ◽  
Line List ◽  
Stellar Spectroscopy ◽  
Near Ir ◽  
The Galaxy

AbstractA major avenue in the study of the Galaxy is the investigation of stellar populations and Galactic chemical evolution by stellar spectroscopy. Due to the dust obscuration, stars in the centre of the Galaxy can only be observed in the near-IR wavelength region. However, existing line lists in this wavelength region are demonstratively not of good enough quality for use in stellar spectroscopy. In response to this, we have developed an empirical astrophysical line list in the K-band based on modelling against the Sun and testing against Arcturus. Of ca. 700 identified interesting lines about 570 lines have been assigned empirically determined values.

scholarly journals Prisma the Instruments

1993 ◽  
Vol 137 ◽  
pp. 672-674
Author(s):  
Andrew Jones
Keyword(s):  
High Resolution ◽  
Stellar Structure ◽  
Quality Data ◽  
The Sun ◽  
Calibration Point ◽  
High Quality ◽  
High Quality Data ◽  
X Ray ◽  
Very High ◽  
Selection Of

Our understanding of Solar structure has increased dramatically in the last couple of decades thanks mainly to the opening of new windows of observation providing high quality data to theoreticians with access to powerful computing facilities. Two of the new windows were UV and X-ray images of the Sun, allowing a detailed view of the upper solar atmosphere, and the development of very high resolution spectrometers allowing us to exploit the solar oscillations to probe the internal structure of the Sun. It is the goal of PRISMA to extend these techniques to other stars, which using the Sun as a calibration point will allow us to explore stellar structure and evolution in ways not possible now.In this poster I will present a possible selection of instruments able to achieve this goal, and explain some of the rationale in their design. A more general overview is presented by T. Appouchaux also in these proceedings. It must be stressed that these are not the definitive instruments to be flown on PRISMA, but rather result from a study to show the feasibility of such a mission. Should PRISMA be chosen as the next ESA medium sized mission, an ‘Announcement of Opportunity’ wiH be issued by ESA and the responses of all people interested in constructing the instrument will be considered.

scholarly journals Deuterium Abundance in the Local ISM

2002 ◽  
Vol 187 ◽  
pp. 75-79
Author(s):  
Jeffrey L. Linsky ◽  
Brian E. Wood
Keyword(s):  
Systematic Errors ◽  
Mean Value ◽  
Gas Analysis ◽  
Interstellar Cloud ◽  
Interstellar Gas ◽  
Local Interstellar Cloud ◽  
The Galaxy ◽  
Nearby Stars ◽  
Data Points ◽  
The Mean

Excellent HST/GHRS spectra of interstellar hydrogen and deuterium Lyman-α absorption toward nearby stars allow us to identify systematic errors that have plagued earlier work and to measure accurate values of the D/H ratio in local interstellar gas. Analysis of 12 sightlines through the Local Interstellar Cloud leads to a mean value of D/H = (1.50 ± 0.10) x 10−5 with all data points lying within ±1σ of the mean. Deciding whether or not the D/H ratio has different values elsewhere in the Galaxy and beyond will be one of the major objectives of the FUSE mission.

scholarly journals The Orion Nebula and the Sun as Probes of Galactic Chemical Evolution

1987 ◽  
Vol 115 ◽  
pp. 111-121
Author(s):  
M. Peimbert
Keyword(s):  
Chemical Evolution ◽  
Chemical Compositions ◽  
The Sun ◽  
Galactic Chemical Evolution ◽  
Orion Nebula ◽  
Chemical Abundances

The solar and the Orion nebula chemical abundances are discussed; their chemical compositions differ at least in the O/H, He/O and 12C/13C ratios. A review of processes that could be responsible for these differences is presented.

Wallal: The 1922 Eclipse Expedition

1990 ◽  
Vol 8 (3) ◽  
pp. 312-313 ◽  
Author(s):  
R. R. Burman ◽  
P. M. Jeffery
Keyword(s):  
Solar Eclipse ◽  
Meteorological Conditions ◽  
Total Solar Eclipse ◽  
Northern Coast ◽  
The Sun ◽  
Great Care ◽  
High Quality ◽  
Western Australian ◽  
Very High ◽  
Scientific Team

AbstractOn 1922 August 20, a 20-strong scientific team, together with a naval party of 10, left Fremantle on one of the major scientific expeditions in Western Australian history. After picking up further personnel at Broome, the party proceeded to the isolated post and telegraph station of Wallal on the northern coast of Western Australia. Their task was to measure with great care the deflection of starlight by the Sun during the total solar eclipse of 1922 September 21. Specially designed photographic equipment of very high quality was used and meteorological conditions were excellent. As a result, measurements were obtained for well over a hundred stars.

scholarly journals Components of the Local Interstellar Medium

2001 ◽  
Vol 203 ◽  
pp. 595-598
Author(s):  
J. L. Linsky ◽  
S. Redfield ◽  
B. Wood
Keyword(s):  
Interstellar Medium ◽  
Critical Velocity ◽  
Column Density ◽  
Interstellar Cloud ◽  
The Sun ◽  
Local Interstellar Medium ◽  
Density Data ◽  
Local Interstellar Cloud

HST, EUVE, and Ca II spectra are providing critical velocity and column density data needed to identify individual stuctures (clouds) of warm gas in the local ISM. The Sun is located very close to the edge of and will soon leave the Local Interstellar Cloud (LIC). We will summarize the properties of the LIC and other nearby warm clouds.

scholarly journals Spectroscopic distances to late-type stars

2012 ◽  
Vol 8 (S289) ◽  
pp. 83-86
Author(s):  
Maria Bergemann ◽  
Aldo Serenelli ◽  
Gregory Ruchti
Keyword(s):  
Stellar Evolution ◽  
Large Scale ◽  
Local Thermodynamic Equilibrium ◽  
Systematic Errors ◽  
Spectroscopic Techniques ◽  
The Sun ◽  
Late Type ◽  
Non Local ◽  
Ionization Balance

AbstractA common approach to determining distances to stars without astrometric information is to compare stellar evolution models with parameters obtained from spectroscopic techniques. This method is routinely applied in the context of large-scale stellar surveys out to distances of several kpc. However, systematic errors may arise because of inaccurate spectroscopic parameters. We explore the effects of non-local thermodynamic equilibrium (NLTE) on the determination of surface gravities and metallicities for a large sample of metal-poor stars within approximately 10 kpc of the Sun. Using the improved Teff scale, we then show that stellar parameters estimated based on the widely used method of 1D LTE excitation-ionization balance of Fe results in distances which are systematically in error. For metal-poor giants, [Fe/H] ~ −2 dex, the distances can be overestimated by up to 70%. We compare the results with those from the Radial Velocity Experiment Survey catalogue (rave) for the stars in common, and find similar offsets.

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