<i>Astrophysics. The Atmospheres of the Sun and Stars</i>

Aller, L. H.; Korff, S. A.

doi:10.1063/1.3061592

Cited by 32 publications

(36 citation statements)

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“…of Hill, Slee, and Mills (1958) show evidence of absorption in the first region against a. background temperature of 7000 OK which is rather unusual as the electron temperature of concentrations of ionized hydrogen. in the Galaxy is generally accepted to be 10 4 OK, in which case the region should be seen in emission (see .Aller 1953 ; also Section VII, Part I of this series). In the 19· 7 McJs isophotes of Shain, Komesaroff, and Higgins (1961), the second region (lII=320°, b II = +3°) is found to lie at the top of a band of absorption which cuts the galactic plane at right angles at 111 =320° and extends out to high latitudes on either side of the plane.…”

Section: Discussion Of Results (A) Thermal Disk Oomponentmentioning

confidence: 99%

A Radio Survey of the Southern Milky Way at a Frequency of 1440 Mc/s. II. The Continuum Emission from the Galactic Disk

Mathewson¹,

Healey²,

Rome³

1962

Aust. J. Phys.

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SummaryThe 1440 Mcls survey (Part I of this series) has been used in conjunction with the 85·5Mc/s survey of Hill, Slee, and Mills (1958) to delineate the distribution of the thermal and nonthermal radiation from the disk component of the Southern Milky Way and so complete an investigation commenced by the Northern Hemisphere observers Westerhout (Leiden) and Large, Mathewson, and Haslam (Jodrell Bank). Results of the analysis show an intense concent,ration of ionized hydrogen in an irregular spiral structure in the inner regions of the Galaxy. From lII=256° to 88°, good agreement was obtained between the longitudes at which concentrations of neutral hydrogen were found to occur from H-line studies and the longitudes at which the ionized hydrogen was concentrated. The steps in the longitude distribution of the 85·5 Mcls radiation which Mills used to delineate the spiral arms of the Galaxy were not all visible in the longitude distribution of the nonthermal component obtained from this present analysis. It is believed that three of Mills's steps are thermal in origin.

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Section: Discussion Of Results (A) Thermal Disk Oomponentmentioning

confidence: 99%

A Radio Survey of the Southern Milky Way at a Frequency of 1440 Mc/s. II. The Continuum Emission from the Galactic Disk

Mathewson¹,

Healey²,

Rome³

1962

Aust. J. Phys.

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“…The minimum would then occur around spectral type F, which then would set the zero-point of the bolometric magnitudes. For the Sun, this implied a value BC V, between −0.11 (Aller 1963) and −0.07 (Morton & Adams 1968). However, with the publication of a larger grid of model atmospheres, e.g., the smallest BC in the Kurucz's grid (1979) implied BC V, = −0.194.…”

Section: Bolometric Correctionsmentioning

confidence: 99%

Synthetic stellar photometry – I. General considerations and new transformations for broad-band systems

Casagrande¹,

VandenBerg²

2014

Monthly Notices of the Royal Astronomical Society

263

321

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After a pedagogical introduction to the main concepts of synthetic photometry, colours and bolometric corrections in the Johnson-Cousins, 2MASS, and HST-ACS/WFC3 photometric systems are generated from MARCS synthetic fluxes for various [Fe/H] and [α/Fe] combinations, and virtually any value of E(B − V) 0.7. The successes and failures of model fluxes in reproducing the observed magnitudes are highlighted. Overall, extant synthetic fluxes predict quite realistic broad-band colours and bolometric corrections, especially at optical and longer wavelengths: further improvements of the predictions for the blue and ultraviolet spectral regions await the use of hydrodynamic models where the microturbulent velocity is not treated as a free parameter. We show how the morphology of the colour-magnitude diagram (CMD) changes for different values of [Fe/H] and [α/Fe]; in particular,how suitable colour combinations can easily discriminate between red giant branch and lower main sequence populations with different [α/Fe], due to the concomitant loops and swings in the CMD. We also provide computer programs to produce tables of synthetic bolometric corrections as well as routines to interpolate in them. These colour-T eff -metallicity relations may be used to convert isochrones for different chemical compositions to various bandpasses assuming observed reddening values, thus bypassing the standard assumption of a constant colour excess for stars of different spectral type. We also show how such an assumption can lead to significant systematic errors. The MARCS transformations presented in this study promise to provide important constraints on our understanding of the multiple stellar populations found in globular clusters (e.g., the colours of lower main sequence stars are predicted to depend strongly on [α/Fe]) and of those located towards/in the Galactic bulge.

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“…(cf. Aller 1963). The basic method is still routinely employed when the conditions along the line of sight are not well determined (cf.…”

Section: T Eff -Log (G) Degeneracy; Curves Of Growthmentioning

confidence: 99%

Abundances in the Herbig Ae star HD 101412

Cowley

Hubrig

González

et al. 2010

A&A

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Context. Recent attention has been directed to abundance variations among very young stars. Aims. We perform a detailed abundance study of the Herbig Ae star HD 101412, taking advantage of its unusually sharp spectral lines. Methods. High-resolution spectra are measured for accurate wavelengths and equivalent widths. Balmer-line fits and ionization equlibria give a relation between T eff , and log(g). Abundance anomalies and uncertain reddening preclude the use of spectral type or photometry to fix T eff . Excitation temperatures are used to break the degeneracy between T eff and log(g). Results. Strong lines are subject to an anomalous saturation that cannot be removed by assuming a low microturbulence. By restricting the analysis to weak (≤20 mÅ) lines, we find consistent results for neutral and ionized species, based on a model with T eff = 8300 K, and log(g) = 3.8. The photosphere is depleted in the most refractory elements, while volatiles are normal or, in the case of nitrogen, overabundant with respect to the sun. The anomalies are unlike those of Ap or Am stars. Conclusions. We suggest the anomalous saturation of strong lines arises from heating of the upper atmospheric layers by infalling material from a disk. The overall abundance pattern may be related to those found for the λ Boo stars, though the depletions of the refractory elements are milder, more like those of Vega. However, the intermediate volatile zinc is depleted, precluding a straightforward interpretation of the abundance pattern in terms of gas-grain separation.

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Astrophysics. The Atmospheres of the Sun and Stars

Cited by 32 publications

References 0 publications

A Radio Survey of the Southern Milky Way at a Frequency of 1440 Mc/s. II. The Continuum Emission from the Galactic Disk

A Radio Survey of the Southern Milky Way at a Frequency of 1440 Mc/s. II. The Continuum Emission from the Galactic Disk

Synthetic stellar photometry – I. General considerations and new transformations for broad-band systems

Abundances in the Herbig Ae star HD 101412

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