scholarly journals Derivation of the Rotational Frequency of Massive Stars from Seismic Studies

2004 ◽  
Vol 215 ◽  
pp. 199-204 ◽  
Author(s):  
C. Aerts ◽  
R. Scuflaire ◽  
A. Thoul
Keyword(s):  
Main Sequence ◽  
High Spatial Resolution ◽  
Massive Stars ◽  
Accurate Determination ◽  
Rotation Frequency ◽  
Rotational Frequency ◽  
Current Status ◽  
B Stars ◽  
Made In

In this contribution we review the current status of the determination of the rotational frequency in non-radially pulsating B stars, i.e. β Cep stars and slowly pulsating B stars. Considerable progress is currently being made in the understanding of the non-radial oscillations of main-sequence B stars by means of high-temporal, high-spatial resolution spectroscopic time series. This has led to the detection of frequency multiplets, which are interpreted as rotationally splitted non-radial modes and which allow an accurate determination of the surface rotational frequency in some stars. We outline how our future goal, i.e. the derivation of the internal rotation frequency, can be achieved.

scholarly journals Core Overshoot and Nonrigid Internal Rotation of Massive Stars: Current Status from Asteroseismology

2007 ◽  
Vol 3 (S250) ◽  
pp. 237-244 ◽  
Author(s):  
Conny Aerts
Keyword(s):  
Main Sequence ◽  
Massive Stars ◽  
Rotation Frequency ◽  
Current Status ◽  
Structure Parameters ◽  
B Stars ◽  
Surface Rotation ◽  
Oscillation Modes ◽  
Drastic Increase ◽  
Core Rotation

AbstractSeismic estimates of core overshoot have been derived from extensive high-precision photometric and spectroscopic ground-based (multisite) campaigns for five main-sequence B-type stars. For three of these, the ratio of the near-core rotation frequency to the surface rotation frequency could be estimated as well, from the identified oscillation modes. We summarise these seismic results obtained for B stars. Now that the technique of asteroseismology was proven to work for probing the interior of massive stars, we expect a drastic increase in the precision of the structure parameters from the space missions CoRoT and Kepler, as well as from currently ongoing ground-based campaigns, in the coming years.

scholarly journals III. On the determination, at sea, of the specific gravity of sea-water

1875 ◽  
Vol 23 (156-163) ◽  
pp. 301-308 ◽  
Keyword(s):  
Specific Gravity ◽  
Physical Condition ◽  
Sea Water ◽  
Accurate Determination ◽  
Actual Difference ◽  
Made In

In the investigation of the physical condition of the ocean the accurate determination of the specific gravity of the water holds a first place. The tolerably numerous observations which have been made in this direction, in a more or less connected manner, are sufficient to prove that the density of the water varies, not only with the latitude and longitude, but also with the distance from the surface of the source from which it is taken. This difference of density depends partly on an actual difference in saltness, and partly on a difference in temperature of the water.

scholarly journals The X-ray stellar population of the LMC

2008 ◽  
Vol 4 (S256) ◽  
pp. 20-29 ◽  
Author(s):  
Yaël Nazé
Keyword(s):  
Stellar Population ◽  
Main Sequence ◽  
Massive Stars ◽  
High Energy ◽  
Magellanic Clouds ◽  
X Rays ◽  
X Ray ◽  
Energy Domain ◽  
X Ray Binaries

AbstractIn the study of stars, the high energy domain occupies a place of choice, since it is the only one able to directly probe the most violent phenomena: indeed, young pre-main sequence objects, hot massive stars, or X-ray binaries are best revealed in X-rays. However, previously available X-ray observatories often provided only crude information on individual objects in the Magellanic Clouds. The advent of the highly efficient X-ray facilities XMM-Newton and Chandra has now dramatically increased the sensitivity and the spatial resolution available to X-ray astronomers, thus enabling a fairly easy determination of the properties of individual sources in the LMC.

scholarly journals Discussion on the structure of atomic nuclei

1929 ◽  
Vol 123 (792) ◽  
pp. 373-390 ◽  
Keyword(s):  
Accurate Determination ◽  
Essential Point ◽  
Whole Numbers ◽  
Atomic Nuclei ◽  
Whole Number ◽  
Nuclear Atom ◽  
The Individual ◽  
The Masses ◽  
Made In

Sir Ernest Rutherford: It was on March 19, 1914, that the Royal Society held its last discussion on the constitution of the atom—just fifteen years ago. I had the honour to open the discussion on that occasion, and the other speakers were Mr. Moseley, Profs. Soddy, Nicholson, Hicks, Stanley Allen, S. P. Thomp­son. In my opening remarks I put forward the theory of the nuclear atom and the evidence in support of it, while Mr. Moseley gave an account of his X-ray investigations, which defined the atomic numbers of the elements, and showed how many gaps were present between hydrogen number 1 and uranium number 92. Prof. Soddy drew attention to the existence of isotopes in the radioactive series, and also to a remarkable observation by Sir Joseph Thomson and Dr. Aston, who had obtained two parabolas in the positive ray spectrograph of neon, and he suggested that possibly the ordinary elements might also consist of mixture of isotopes. I think you will find that the remarks and suggestions made in this discussion fifteen years ago have a certain pertinence to-day. In particular Hicks and Stanley Allen drew attention to the importance of taking into account the magnetic fields in the nucleus, although at that time we had very little evidence on that point, and even to-day our information is very scanty. What has been accomplished in the intervening period ? On looking back we see that three new methods of attack on this problem have been developed. The first, and in some respects the most important, has been the proof of the isotopic constitution of the ordinary elements, and the accurate determination of the masses or weights of the individual isotopes, mainly due to the work of Dr. Aston. This has led in a sense to an extension of the original ideas of Moseley. The experiments of the latter fixed the number of possible nuclear charges, while Aston has shown that there are a large number of species of atoms each defined by its nuclear charge, although their masses and their nuclear constitution may be different. The essential point brought out in the earlier work of Dr. Aston was that the masses of the elements are approxi­mately expressed by whole numbers, where oxygen is taken as 16—with the exception of hydrogen itself. But the real interest, as we now see it, is not the whole number rule itself, but rather the departures from it.

scholarly journals On a relation between the refractive and dispersive constants of the inert gases

1927 ◽  
Vol 114 (769) ◽  
pp. 659-661
Keyword(s):  
Accurate Determination ◽  
Inert Gases ◽  
Critical Temperatures ◽  
Philosophical Magazine ◽  
Empirical Relations ◽  
Five Elements ◽  
Made In

In 1911 I published in the ‘Philosophical Magazine’ a paper on new determinations of some constants of the inert gases, and drew attention to the remarkable empirical relations which subsist between (1) the calculated numbers of “dispersion” electrons in the atoms of these five elements, (2) their “viscosity diameters” as determined by Prof. A. O. Rankine, and (3) their critical temperatures. Since that time the figures used have undergone revision. The accurate determination of the value of ε by Millikan has enabled us to give absolute, instead of relative, values to the apparent numbers of dispersion electrons ( q , see Table I). Chapman has recalculated the viscosity diameters, and Rankine has revised Chapman’s values, in the light of corrections to be made in his own values of Sutherland’s constants for argon, krypton and xenon. But these alterations have not affected the validity of the relations then published.

scholarly journals From single bacterial cell imaging towards in vivo single-molecule biochemistry studies

2019 ◽  
Vol 63 (2) ◽  
pp. 187-196 ◽  
Author(s):  
Ulrike Endesfelder
Keyword(s):  
Single Molecule ◽  
Model Systems ◽  
Current Status ◽  
Bacterial Cells ◽  
Molecular Architecture ◽  
Cellular Mechanisms ◽  
Microscopy Techniques ◽  
Made In

Abstract Bacteria as single-cell organisms are important model systems to study cellular mechanisms and functions. In recent years and with the help of advanced fluorescence microscopy techniques, immense progress has been made in characterizing and quantifying the behavior of single bacterial cells on the basis of molecular interactions and assemblies in the complex environment of live cultures. Importantly, single-molecule imaging enables the in vivo determination of the stoichiometry and molecular architecture of subcellular structures, yielding detailed, quantitative, spatiotemporally resolved molecular maps and unraveling dynamic heterogeneities and subpopulations on the subcellular level. Nevertheless, open challenges remain. Here, we review the past and current status of the field, discuss example applications and give insights into future trends.

The determination of the helium abundance in main-sequence B stars

1985 ◽  
Vol 292 ◽  
pp. 589 ◽  
Author(s):  
S. C. Wolff ◽  
J. N. Heasley
Keyword(s):  
Main Sequence ◽  
Helium Abundance ◽  
B Stars

scholarly journals Atmosphere models for very low mass stars, brown dwarfs and exoplanets

1997 ◽  
Vol 189 ◽  
pp. 227-233
Author(s):  
I. Baraffe ◽  
F. Allard
Keyword(s):  
Main Sequence ◽  
Accurate Determination ◽  
Brown Dwarfs ◽  
Considerable Effort ◽  
Low Mass Stars ◽  
The Past ◽  
Substellar Objects ◽  
Cool Stars ◽  
Low Mass

Over the past decade considerable effort, both observational and theoretical, has been directed towards a more accurate determination of the stellar lower main sequence and of the sub-stellar domain covered by Brown Dwarfs and Planets. Astronomers have been looking for brown dwarfs for more than a decade, either with standard astronomical technics or with microlensing experiments. A breakthrough in the search for brown dwarfs was very recently achieved with the discovery of the first cool brown dwarf GL 229B (Nakajima et al. 1995). At the same epoch, the search for planets blossomed with the discovery of a Jupiter - mass companion of the star 51 Pegasi (Mayor and Queloz 199,5). Now, the number of faint, cool stars and substellar objects is rising rapidly.

scholarly journals II. Magnetic survey of the east of France in 1869

1872 ◽  
Vol 162 ◽  
pp. 7-27
Keyword(s):  
Accurate Determination ◽  
Magnetic Survey ◽  
Sources Of Information ◽  
The West ◽  
Mean Values ◽  
The City ◽  
Central Station ◽  
Previous Occasion ◽  
Made In

This survey, which occupied a considerable portion of the months of August and September 1869, is a continuation of the series of observations made in the west of France during the preceding year. The instruments used were the same on both occasions, the only changes made for the second expedition being (1°) the substitution of a theodolite by Jones in lieu of Cooke’s transit-theodolite, which was slightly too heavy for carrying in the hand, and (2°) the procuring, through the kindness of Dr. Stewart, a second tripod stand similar to our own, which rendered the series of observations with two observers much more rapid than on the previous occasion. The observations were undertaken, as before, by the Rev. W. Sidgreaves and myself, the Vibrations and Deflections falling to his share, and the Declination and Chronometer comparisons remaining in my hands, whilst the Dip was in general observed by both. The method of reduction is almost identical with that adopted for the observations taken in the west of France. The geographical positions of the different stations have been calculated, as far as possible, from the data given in the 'Connaissance des Temps,’ but where this could not be done I have had recourse to the most reliable sources of information at my command. For the accurate determination of the positions of Mont Rolland (near Dôle), of N. D. de Myans (near Chambéry), of Mongré (near Villefranche-sur-Soane), of Iseure (near Moulins), and of our station at Marseilles I am indebted to the kindness of the Rev. N. Larcher, S. J., Membre de la Société Météorologique de France. The coordinates of Vaugirard were readily obtained from a good map of Paris, and for Issenheim and Monaco I have to depend on Cassini’s ‘Carte Générale de la France’ and on Philip’s 'Imperial Atlas.’ The Imperial Observatory at Paris is chosen as the natural position for the origin of coordinates, in lieu of our central station of observation at Vaugirard, which lies on the outskirts of the city; the resulting mean values will thus require no correction, and will be immediately comparable with those of most other observers.

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