scholarly journals Mira Variables: Theory versus Observation

1995 ◽  
Vol 155 ◽  
pp. 127-138 ◽  
Author(s):  
P.R. Wood
Keyword(s):  
Fundamental Mode ◽  
Magellanic Clouds ◽  
The Other ◽  
Solar Neighbourhood ◽  
Angular Diameter ◽  
Pulsation Velocity ◽  
Multiple Modes ◽  
Pulsation Mode ◽  
Mira Variables ◽  
Theory Versus

AbstractThe identification of the mode of pulsation of Mira variables remains a major problem. Recent angular diameter measurements of solar neighbourhood Miras suggest large radii consistent with first overtone pulsation. On the other hand, the pulsation velocity amplitudes of Mira variables point to fundamental mode pulsation. There is some marginal evidence from multiple modes in Miras that the prime pulsation mode is the first overtone, while distinct (K,logP) sequences in the Magellanic Clouds point to the Miras being fundamental mode pulsators. The above confusing evidence is presented and discussed. Finally, the (K,logP) relations in the SMC and LMC are compared in order to determine if there is any metallicity dependence.

scholarly journals Mira Variables: Statistical Parallaxes, Kinematics and Period–Luminosity Relation

2000 ◽  
Vol 176 ◽  
pp. 128-129
Author(s):  
E. Kilpio ◽  
O. Malkov ◽  
N. Kharchenko ◽  
E. Schilbach
Keyword(s):  
Fundamental Mode ◽  
Pulsation Period ◽  
Orbital Parameters ◽  
Pulsation Mode ◽  
Mira Variables ◽  
The Mean ◽  
Absolute Magnitudes ◽  
Low Dispersion ◽  
Kinematical Parameters ◽  
Kinematical Data

AbstractBased on the statistical parallaxes, the mean absolute magnitudes and the spatial kinematical parameters were determined as functions of the periods for Mira variables given in the GCVS-4 and selected stars for which new kinematical data were obtained during the last decade. The BC were derived for the oxygen-rich Miras and the P–L relation was compared with predictions from pulsation theory. The following findings result from this analysis:1) With respect to Miras, the GCVS-4 is complete down to V = 9m.2) The kinematical and orbital parameters indicate a higher age for the oxygen-rich Miras pulsating with smaller periods.3) The Mbol-period relation of the oxygen-rich Miras shows a low dispersion and does not depend on the pulsation mode. The resulting P–L relation is a superposition of P–L relations of different pulsation modes.4) The fraction of the fundamental mode pulsators decreases with increasing pulsation period.

Global Trends in Income Inequality: Theory Versus Reality

2017 ◽  
pp. 143-168
Author(s):  
Venkat Venkatasubramanian
Keyword(s):  
Income Inequality ◽  
Prior Knowledge ◽  
The Other ◽  
Global Trends ◽  
Inequality Theory ◽  
Theory Versus ◽  
Income Data ◽  
The U.S

We compare the predictions of our theory with empirical income data from a dozen different countries. We define a new measure of inequality, called the non-ideal inequality coefficient. We show that Norway is close to ideal inequality for the bottom 99% of the population while the U.S. is the most non-ideal at the other extreme. The other countries are in between these two. We find it remarkable that the Scandinavian societies have discovered the near-ideal share by themselves in practice without any prior knowledge of even its existence.

scholarly journals Miras, mass loss, and the origin of planetary nebulae

1981 ◽  
Vol 59 ◽  
pp. 353-356 ◽  
Author(s):  
L. A. Willson
Keyword(s):  
Mass Loss ◽  
Fundamental Mode ◽  
Planetary Nebulae ◽  
Asymptotic Giant Branch ◽  
Mira Variables ◽  
Moderate Mass

Mira variables are found at the tip of the asymptotic giant branch, with L≈3000-5000Lʘ and TeH3000K. (Feast 1981; Willson 1981a). They are fundamental mode pulsators (Willson 1979, 1981a). A typical Mira has P~350 days, R~200-300Rʘ, M~1-2Mʘ (Willson 1979; 1981a). From the atmospheric velocities of the Miras plus a fundamental mode period-massradius relation one finds present masses for the Miras which are not very different from their progenitor masses (Willson 1981a). This suggests that pre-Mira mass loss is moderate -- ≲20% of the mass is lost before pulsation starts. In fact one expects only moderate mass loss before the Mira stage;

scholarly journals A Survey of BL Herculis-Type Models

1993 ◽  
Vol 139 ◽  
pp. 277-277
Author(s):  
J. Robert Buchler ◽  
Pawel Moskalik
Keyword(s):  
Light Curve ◽  
Fundamental Mode ◽  
Qualitative Agreement ◽  
Nonlinear Behavior ◽  
The Other ◽  
Amplitude Ratios ◽  
Classical Cepheids ◽  
Dominant Feature ◽  
Stellar Masses ◽  
Pulsation Cycle

AbstractWe have studied the nonlinear behavior of several sequences of BL Herculis-type models. The question arose whether the 2:1 resonance between the fundamental mode and the second overtone would cause the same systematic variation of Fourier parameters of the pulsation cycle with period ratio P2/P0 as was seen in the classical Cepheids. We find that for the BL Her stars, the behaviour of the light-curve Fourier phases is markedly different from the Cepheid case. In particular, ϕ21 exhibits essentially a featureless, monotone increase throughout the range of P2/P0, which is in qualitative agreement with the observed trend (Petersen & Diethelm 1986). In the velocity curves, on the other hand, the 2:1 resonance is a dominant feature and the progression of the Fourier phases and the amplitude ratios is similar to those witnessed in the Cepheids. However, here the sensitivity to the stellar masses and luminosities is significantly stronger. Our results show that radial velocity observations of the BL Her stars would pinpoint the resonance and put important new constraints on the models.

scholarly journals An Interferometric Survey of Mira Variables and M Supergiants

1994 ◽  
Vol 158 ◽  
pp. 395-397
Author(s):  
P.G. Tuthill ◽  
C.A. Haniff ◽  
J.E. Baldwin
Keyword(s):  
Hot Spot ◽  
The Other ◽  
Spherically Symmetric ◽  
Preliminary Results ◽  
Mira Variables

We present preliminary results from an imaging survey of bright northern Mira variables and Supergiants. Diffraction-limited images of Mira exhibit the same elongation along PA 120° as observed in previous observations. Of the other Mira variables observed, R Cas is unambiguously detected as non-spherically symmetric. Our observations of α-Her are consistent with there being a ‘hot-spot’ on its surface, similar to those we have previously detected on Betelgeuse.

XIV.—On Analysing the Physical Evolution of Galaxies

1960 ◽  
Vol 65 (3) ◽  
pp. 207-222
Author(s):  
V. C. Reddish
Keyword(s):  
Magellanic Clouds ◽  
The Other ◽  
Bright Star ◽  
Evolution Of Galaxies ◽  
Other Hand ◽  
Luminosity Functions ◽  
Mass Ratios ◽  
Set Up

SYNOPSISInvestigations based on gas masses, bright star counts, and luminosity-mass ratios of galaxies lead to one of two conclusions. If the galaxies are all of the same age, the faint ends of the initial luminosity functions of stars at formation differ greatly from one galaxy to another. On the other hand consistent results in the analysis are obtained with luminosity functions that are more nearly constant and ages which range from one to thirty thousand-million years. The various possibilities can be tested by observations on the Magellanic Clouds.Equations are set up which describe, as functions of time, the integrated properties of a galaxy as a system of stars and gas.

scholarly journals Helium abundances in planetary nebulae: Nucleosynthesis and chemical evolution

2009 ◽  
Vol 5 (S268) ◽  
pp. 181-182
Author(s):  
W. J. Maciel ◽  
R. D. D. Costa ◽  
T. E. P. Idiart
Keyword(s):  
Chemical Evolution ◽  
Planetary Nebulae ◽  
Magellanic Clouds ◽  
Heavy Elements ◽  
Solar Neighbourhood ◽  
Host Galaxies ◽  
Intermediate Mass ◽  
Large Sample ◽  
Intermediate Mass Stars ◽  
Progenitor Stars

AbstractWe have obtained a large sample of PN with accurately determined helium abundances, as well as abundances of several heavy elements. The nebulae are located in the solar neighbourhood, in the galactic bulge, disk and anticentre, and in the Magellanic Clouds. The abundances are analyzed both in terms of the nucleosynthesis of intermediate mass stars and the chemical evolution of the host galaxies. In particular, correlations between the He/H ratio and the abundances of N and O are used as constraints of the nucleosynthetic processes occurring in the progenitor stars.

scholarly journals Australian Journal of Physics Astrophysical Supplement

1976 ◽  
Vol 29 (5) ◽  
pp. 471
Author(s):  
JN Clarke ◽  
AG Little ◽  
BY Mills
Keyword(s):  
Flux Density ◽  
High Frequency ◽  
Magellanic Clouds ◽  
Australian Journal ◽  
The Other ◽  
Optical Data ◽  
Radio Sources ◽  
Angular Extent

The fourth catalogue of radio sources observed at 408 MHz with the Molonglo radiotelescope is presented. A total of 1349 sources is listed to a limiting flux density of 0�2 Jy, the catalogue being largely complete above 0� 25 Jy. The area of sky surveyed includes the Magellanic Clouds as well as a comparison region of similar angular extent. Detailed notes are provided on some of the Cloud sources, and maps are given for complex sources in the region of the Clouds. Those sources for which high-frequency or optical data are available are classified into two lists, one of Cloud members and the other of 'unidentified nonthermal sources', presumably not Cloud members.

scholarly journals Long Period Variables in the Magellanic Clouds and the Galaxy

1993 ◽  
Vol 139 ◽  
pp. 192-200 ◽  
Author(s):  
S.M.G. Hughes
Keyword(s):  
Mass Loss ◽  
Galactic Disk ◽  
Magellanic Clouds ◽  
Pulsation Mode ◽  
Long Period ◽  
Long Period Variables ◽  
The Galaxy ◽  
Loss Rates

AbstractNew results (∼last two years) on mainly observational properties of Long Period Variables (LPVs) in the Magellanic Clouds and the Galaxy are reviewed. These properties include the effects of metallicity variations on their mass loss rates, the use of AGB LPVs to map the stellar distributions of the Galactic disk and bulge, and using detailed observations of nearby Miras to investigate their structure and to obtain new parallax distances, with implications for the pulsation mode of Miras.

scholarly journals Linear and Nonlinear Pulsations of β Cephei Stars

1980 ◽  
Vol 58 ◽  
pp. 323-327
Author(s):  
Arthur N. Cox ◽  
Stephen W. Hodson
Keyword(s):  
Fundamental Mode ◽  
Binary Star ◽  
Angular Diameter ◽  
Pulsation Period ◽  
Linear And Nonlinear

The best known β Cephei variable is a α Virginis (Spica) because it is a binary star (P = 4.01 days) and has a interferometer measurement of its angular diameter. In this study to see if the pulsations can be caused by mixing of hydrogen and helium in the semiconvective zone, the parameters we take are 11.5 M⊙, 26,300 K, 6.5 x 1037 erg/s with an envelope composition of Y = 0.28, Z = 0.02. These data agree within the errors of observations as reported recently by Odell (1980), and the theoretical radial fundamental mode period of 0.171 day compares well with the single observed pulsation period of 0.174 day.

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