The structure of rotating stars from an extension of the Kippenhahn-Thomas method

A method is presented whereby the structure of rotating stars may be determined from an initial guess at the geometry of equipotential surfaces. The method may be considered an extension of the work of Kippenhahn and Thomas in that a uniformly continuous geometry is defined in terms of the appropriate spherical model with Roche characteristics at the surface of the configuration and sphericity at the centre. A simple Cowling model in uniform rotation is employed to illustrate the technique and for comparison purposes with previous work.     

Das elliptische eingeschränkte Dreikörperproblem

Inhalt Eine einfache Herleitung der allgemeinen Gleichungen des elliptischen eingeschränkten Dreikörperproblems und der daraus folgenden linearen Variationsgleichungen mit periodischen Koeffizienten für die Bewegung in der Nähe der Librationszentren wird gegeben. Die in zwei früheren Arbeiten vorgelegte Aufspaltung der ebenen Variationsgleichungen 4. Ordnung in zwei Komponenten 2. Ordnung wird kurz rekapituliert.Bei Benützung dieser Aufspaltung wird die Bewegung in der Umgebung der Dreieckspunkte näher untersucht. Mit Hilfe einer Näherungslösung werden Frequenzverteilung und Stabilitätsbereiche bestimmt.

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A simple derivation of the general equations of the elliptic restricted Three-Body Problem is given from which immediately follow the linear variational equations with periodic coefficients describing the motion close to the libration centers. The explicit separation of these 4th order planar variational equations into two 2nd order components is shortly repeated.Using this separation the motion in the neighborhood of the equilateral points is investigated in more detail. An approximate solution is determined giving frequency distribution and stability domains.

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Gehalten vor der Konferenz über Celestial Mechanics, Oberwolfach, Germany, August 27–September 2, 1972.     

The constancy of galactic cosmic rays as recorded by cosmogenic nuclides in iron meteorites

We measured the He, Ne, and Ar isotopic concentrations and the ¹⁰Be, ²⁶Al, ³⁶Cl, and ⁴¹Ca concentrations in 56 iron meteorites of groups IIIAB, IIAB, IVA, IC, IIA, IIB, and one ungrouped. From ⁴¹Ca and ³⁶Cl data, we calculated terrestrial ages indistinguishable from zero for six samples, indicating recent falls, up to 562 ± 86 ka. Three of the studied meteorites are falls. The data for the other 47 irons confirm that terrestrial ages for iron meteorites can be as long as a few hundred thousand years even in relatively humid conditions. The ³⁶Cl‐³⁶Ar cosmic ray exposure (CRE) ages range from 4.3 ± 0.4 Ma to 652 ± 99 Ma. By including literature data, we established a consistent and reliable CRE age database for 67 iron meteorites. The high quality of the CRE ages enables us to study structures in the CRE age histogram more reliably. At first sight, the CRE age histogram shows peaks at about 400 and 630 Ma. After correction for pairing, the updated CRE age histogram comprises 41 individual samples and shows no indications of temporal periodicity, especially not if one considers each iron meteorite group separately. Our study contradicts the hypothesis of periodic GCR intensity variations (Shaviv 2002, 2003), confirming other studies indicating that there are no periodic structures in the CRE age histogram (e.g., Rahmstorf et al. 2004; Jahnke 2005). The data contradict the hypothesis that periodic GCR intensity variations might have triggered periodic Earth climate changes. The ³⁶Cl‐³⁶Ar CRE ages are on average 40% lower than the ⁴¹K‐K CRE ages (e.g., Voshage 1967). This offset can either be due to an offset in the ⁴¹K‐K dating system or due to a significantly lower GCR intensity in the time interval 195–656 Ma compared to the recent past. A 40% lower GCR intensity, however, would have increased the Earth temperature by up to 2 °C, which seems unrealistic and leaves an ill‐defined ⁴¹K‐K CRE age system the most likely explanation. Finally, we present new ²⁶Al/²¹Ne and ¹⁰Be/²¹Ne production rate ratios of 0.32 ± 0.01 and 0.44 ± 0.03, respectively.     

Interference in solar oscillations

We have analyzed magnetograph observations of the 5-min oscillations. We find that most of the oscillatory power is concentrated in space and frequency. Interference effects where these concentrations overlap can explain some of the variations in amplitude of the oscillation.Of the National Bureau of Standards and University of Colorado.     

Photometric and spectrophotometric observations of Nova Delphini 1967

Photographic, photovisual and photoelectric (V) observations of Nova Delphini 1967 were made from August 8 to October 31 (Table I, Figure 1). Simultaneously spectrophotometric measurements of the continuum were made on objective prism exposures extending to November 26, and spectrophotometric gradients derived (Tables II and III; Figures 3, 4, and 5). The continuum of Nova near its flat maximum is close to that of an early-type star in contrast to late-type absorptionline spectrum.     

Decametric radio spectra and positions during the flare of August 28, 1966: 1522 UT

During a period of intense decametric continuum arising near the center of the sun, there occurred additional very strong emission closely associated with the flare beginning at 1522 UT on August 28, 1966. Owing to strong ionospheric absorption from about 1527 UT on, which eliminated telecommunications interference, the frequency range over which the flare-associated emission appears is unusually large, from the upper limit of the spectrograph, 41 MHz, to about 11 MHz, where external reflection cuts off the solar signals. Strong bursts of Type III (fast drift) occur from 1527 to 1531 UT, and a complex Type II (slow drift) from 1532 to 1547 UT. As the Type-II burst progresses at frequencies from 15 to 25 MHz, Northward position shifts of many solar radii probably take place; at higher frequencies the burst moves in a complicated pattern through a much narrower range of distances to the North of the sun. Type-IV emission, from 1540 UT on, moves a large distance to the sun's North, and then, after 1600 UT, returns to a stable position quite close to the sun.     

High-resolution measurements of photosphere and sunspot velocity and magnetic fields using a narrow-band birefringent filter

Modifications to a Zeiss 1/4 Å filter are described which allow high spatial resolution observations of the line-of-sight velocities and magnetic fields in the photosphere and in sunspots. First results show: (1) the granular velocity field to be very strong; differences in upward motions in the granules and downward motions in between are as much as 6 km/sec; (2) the Evershed effect in sunspots to originate primarily in the dark regions between bright penumbral filaments.     

The scattering mean free path in the Uranian atmosphere

New measurements of the equivalent widths of the 4-0 S(0) and S(1) H₂ quadrupole lines in the Uranian spectrum have been obtained using high dispersion (4.12 Å/mm) image-tube spectrography. The measured equivalent widths are $\text{62 ± 19}\text{m}\text{A}\text{?}\text{and}\text{58 ± 13}\text{m}\text{A}\text{?}$ for the S(0) and S(1) lines, respectively. Curve-of-growth analysis in terms of a reflecting layer model yields an H₂ column-density of 780_?330⁺⁹⁴⁰km amagat and a temperature of 78_?24⁺⁸⁰°K. Interpretation using a semi-infinite, homogeneous, isotropically scattering model for line formation yields a scattering mean free path at λ6400 Å of 550 ± 250 km amagat. Quoted errors for both the H₂ column-density and the scattering mean free path include the effect of uncertainty in the choice of atmospheric temperature. The results are discussed in terms of current models for the Uranian atmosphere.