scholarly journals 33. Commission de la Statistique Stellaire

1936 ◽  
Vol 5 ◽  
pp. 228-232
Author(s):  
M. Lindblad ◽  
MM. Bok ◽  
Eddington ◽  
Hertzsprung ◽  
S. Hirayama ◽  
...  
Keyword(s):  
White Dwarfs ◽  
Main Sequence ◽  
Spectral Characteristics ◽  
Absolute Magnitude ◽  
Wide Field ◽  
Continuous Absorption ◽  
Trigonometric Parallaxes ◽  
The One ◽  
Almost All ◽  
Made In

In the wide field of research covered by the Commission considerable progress has been made in recent years, and it is only possible here to touch briefly on the results of a few lines of investigation, without any attempt to completeness.Stellar luminosities. On the basis of the new list of Mount Wilson spectroscopic parallaxes and a compilation of the long series of modern trigonometric parallaxes A. van Maanen finds 617 objects within a distance of 20 parsecs from the sun. It is very doubtful, however, if we know all the stars even in the region of 5 parsecs radius. Almost all the known stars within 20 parsecs belong to the main sequence, the faintest star being of absolute magnitude +16.6. The most interesting deviations from the main sequence are the three “white dwarfs”, Сотр. of Sirius, Comp. o2 Eridani, and van Maanen’s F type star. G. P. Kuiper lists 3 additional white dwarfs at larger distances which were estimated to be of types Bo, B7 and A2. For the first two stars, A.C. 70°8247 and Wolf 1346, a revision of the spectral types by Adams and Humason gives A2 and A5, respectively, although the spectra differ considerably from normal ones. The A2 star in Kuiper’s list is the one discovered by Oosterhoff in the region of the cluster h, X Persei; its spectral characteristics have been examined by Öhman and by Humason. The absence of the high-numbered members of the Bahner series and of the continuous absorption at the Balmer limit seems to be an important criterion of such stars. A white dwarf of quite peculiar spectrum (type probably about B8) is the companion of o Ceti discovered spectro-graphically by Joy in 1922. There appear several additional deviations towards faint magnitudes from the main sequence which may be classed more or less safely among the white dwarfs. A few such cases have been discussed at Lund by J. Tuominen.

scholarly journals The Luminosity Determination

1995 ◽  
Vol 10 ◽  
pp. 399-402
Author(s):  
A.E. Gómez ◽  
C. Turon
Keyword(s):  
Main Sequence ◽  
Small Volume ◽  
Absolute Magnitude ◽  
Fitting Procedure ◽  
Trigonometric Parallaxes ◽  
The Mean ◽  
The Absolute ◽  
Absolute Magnitudes ◽  
Kinematical Data ◽  
Magnitude Determination

The Hertzprung-Russel (HR) diagram luminosity calibration relies basically on three kinds of data: trigonometric parallaxes, kinematical data (proper motions and radial velocities) and cluster distances obtained by the zero-age main sequence fitting procedure. The most fundamental method to calculate the absolute magnitude is the use of trigonometric parallaxes, but up to now, accurate data only exist for stars contained in a small volume around the sun. Individual absolute magnitudes are obtained using trigonometric parallaxes or photometric and spectroscopic calibrations. In these calibrations the accuracy on the absolute magnitude determination ranges from ±0.m2 in the main sequence to ±0m5 in the giant branch. On the other hand, trigonometric parallaxes, kinematical data or cluster distances have been used to make statistical calibrations of the absolute magnitude. The standard error on the mean absolute magnitude calibrations ranges from ±0m3 to ±0m6 on the mean sequence, from ±0m5 to ±0m7 on thegiant branch and is of about 1mfor supergiants.Future improvements in the absolute magnitude determination will depend on the improvement of the basic data from the ground and space. A brief overview of the new available data is presented. In particular, the analysis of the first 30 months data of the Hipparcos mission (H30) (from the 37 months data of the whole mission) allows to perform a statistical evaluation of the improvements expected in the luminosity determination.

scholarly journals On the characteristics of 150-km echoes observed in the Brazilian longitude sector by the 30 MHz São Luís radar

2011 ◽  
Vol 29 (10) ◽  
pp. 1905-1916 ◽  
Author(s):  
F. S. Rodrigues ◽  
E. R. de Paula ◽  
J. L. Chau
Keyword(s):  
Signal To Noise Ratio ◽  
Spectral Characteristics ◽  
Occurrence Rate ◽  
Wide Field ◽  
Echo Intensity ◽  
Doppler Shifts ◽  
Wide Field Of View ◽  
The Mean ◽  
Local Noon ◽  
Made In

Abstract. We present long-overdue details about the intensity and spectral characteristics of 150-km echoes observed by the São Luís radar in Brazil. The São Luís observations show that the echoes usually come from multiple scattering layers that descend in altitude before local noon, and ascend during afternoon hours, similar to what has been found in observations made in other longitude sectors. The layers are usually 3–5 km thick and located, mostly, between 130 and 170 km altitude. The measurements also show variations in echo intensity that are similar to observations made at other equatorial and off-equatorial sites. Analysis of observations made during 2008 shows significant (>37%) monthly occurrence rates for every month. Reduced occurrence rates were observed around March Equinox. We associate this reduction in occurrence rate, however, to a non-geophysical factor. An increase in the daytime sky noise in the months around March Equinox causes a decrease in the signal-to-noise ratio (SNR) of the echoes, which makes them less distinguishable in our analysis. A higher occurrence of weaker echoes around March Equinox was confirmed by an statistical analysis of the seasonal variation of echo intensities. Strong, long-lasting and, therefore, more noticeable echoing layers, however, were observed between June and early September compared to other months in 2008. Spectral analyses show that most of the echoes have negative mean Doppler shifts indicating upward velocities. The echoes also have narrow spectral widths of only a few m s−1. Finally, we also found that the mean Doppler shift of the observed echoes can vary noticeably with altitude at times. Using spaced antenna measurements we show that this is caused by the wide field-of-view of the radar and the spatial distribution of the scatterers within the radar beam.

scholarly journals On Syllable Weight in Amharic

Aethiopica ◽  
2020 ◽  
Vol 22 ◽  
Author(s):  
Rainer Voigt
Keyword(s):  
Second Language ◽  
Data Base ◽  
Syllable Weight ◽  
Incomplete Knowledge ◽  
Inaccurate Data ◽  
The One ◽  
Almost All ◽  
Stress Patterns ◽  
Made In

Contrary to the claim made in a recently published article, that literature on Amharic stress is ‘almost nonexistent’, I present and quote from the works of Armbruster, Guidi, Abraham, and others, and discuss their concept of stress patterns in Amharic. However, my criticism mainly concerns the data base used in the aforementioned article which addresses the topic of syllable weight, and where an attempt is made to analyse stress in Amharic based on a large number of examples. In these examples, however, consonantal lengthening and the distinction between the central vowels ǝ and ä and ä and a are incorrectly represented in almost all verbal forms, infinitives, and adjectives. This is partly the result of the informants speaking Amharic as their second language, and partly due to the fieldworkers’ incomplete knowledge of the language. This gives rise to many mistakes even amongst the simplest one- and two-syllable words. Ultimately this raises the question of whether those authors’ linguistic conclusions on the moraic nature of codas can be regarded as safe since it is based on inaccurate data. I also apply my own analysis to Amharic reduplicated adjectival forms, which differs from the one proposed in the said article.

A study of the physical properties of SB2s with both the visual and spectroscopic orbits

2020 ◽  
Vol 492 (2) ◽  
pp. 2709-2721
Author(s):  
Luca Piccotti ◽  
José Ángel Docobo ◽  
Roberta Carini ◽  
Vakhtang S Tamazian ◽  
Enzo Brocato ◽  
...  
Keyword(s):  
Stellar Model ◽  
Spectroscopic Binaries ◽  
Adopted Model ◽  
Magnitude Diagram ◽  
Trigonometric Parallaxes ◽  
The One ◽  
The Masses ◽  
Almost All ◽  
Unique Mass ◽  
Good Agreement

ABSTRACT The study of a selected set of 69 double-lined spectroscopic binaries (SB2) with well-defined visual and spectroscopic orbits was carried out. The orbital parallax, the mass, the colour, and the luminosity of each component were derived from observational data for almost all of these systems. We have also obtained an independent estimation of the component masses by comparing the colour–magnitude diagram (CMD) to the stellar evolution tracks reported by Pietrinferni. Nearly all of the observational points on the CMD are located between two tracks of slightly different mass or which fall very close to the one corresponding to a unique mass value. The masses obtained from the stellar model are in good agreement with their empirical values determined by parallax techniques (orbital, Gaia, and dynamical). This means that our adopted model is rather reliable and can therefore be used to infer further information, such as the age of each component in the studied systems. Our results indicate a fair correspondence between the age of primaries and secondary stars within 3σ. Nevertheless, we caution that these age indications suffer of uncertainties due to both inhomogeneities/low precision of the adopted photometric data and possible systematics. Finally, it is statistically shown that along with the orbital and trigonometric parallaxes, the dynamical parallax can serve as a reliable tool for distance estimates.

scholarly journals The population of hot subdwarf stars studied with Gaia

2020 ◽  
Vol 635 ◽  
pp. A193 ◽  
Author(s):  
S. Geier
Keyword(s):  
Proper Motion ◽  
White Dwarfs ◽  
Main Sequence ◽  
Absolute Magnitude ◽  
Radial Velocities ◽  
Horizontal Branch ◽  
Atmospheric Parameters ◽  
Main Sequence Stars ◽  
Data Release ◽  
Hot Subdwarfs

In light of substantial new discoveries of hot subdwarfs by ongoing spectroscopic surveys and the availability of new all-sky data from ground-based photometric surveys and the Gaia mission Data Release 2, we compiled an updated catalogue of the known hot subdwarf stars. The catalogue contains 5874 unique sources including 528 previously unknown hot subdwarfs and provides multi-band photometry, astrometry from Gaia, and classifications based on spectroscopy and colours. This new catalogue provides atmospheric parameters of 2187 stars and radial velocities of 2790 stars from the literature. Using colour, absolute magnitude, and reduced proper motion criteria, we identified 268 previously misclassified objects, most of which are less luminous white dwarfs or more luminous blue horizontal branch and main-sequence stars.

scholarly journals Stellar chemical-abundance gradient in the direction of the South Galactic Pole - preliminary results

1985 ◽  
Vol 106 ◽  
pp. 151-152
Author(s):  
Ch. F. Trefzger ◽  
J. W. Pel ◽  
A. Blaauw
Keyword(s):  
Main Sequence ◽  
Absolute Magnitude ◽  
Photometric System ◽  
Intermediate Type ◽  
Chemical Abundance ◽  
Spectroscopic Analyses ◽  
Program Star ◽  
Effects Of Temperature ◽  
Semi Empirical ◽  
Made In

Using the Walraven VBLUW photometric system, we have studied the metal content of 89 F and G stars in the Galactic South Pole field SA141. Our sample is based on the Basel survey of RGU photometry in Selected Areas, and it contains all stars in SA141 with VJ <14m.5 and (G-R)<1m.15 (spectral types earlier than about G7). The observations were made with the VBLUW photometer and the 90-cm Dutch Telescope at ESO, La Silla.For unreddened intermediate-type stars the VBLUW photometry enables us to separate the effects of temperature, gravity, and metallicity (cf. Lub and Pel, 1977). Since reddening is negligible in SA141, we can therefore determine these three parameters for each program star once the photometric indices are calibrated in terms of Teff, log g, and [Fe/H]. The latter calibration was made in a semi-empirical way, using VBLUW observations of stars with spectroscopic analyses in combination with theoretical colors based on the model spectra by Kurucz (1979). We used the Hyades main-sequence as a zeropoint, adopting [Fe/H] = +0.15 for this cluster.The results in the (V-B)-(B-L) diagram are shown in Fig. 1. This diagram is very sensitive to metallicity, but almost gravity-independent. Fig. 1 indicates that most program stars have metallicities in the range −1 ≦ [Fe/H] ≦ 0. The distribution of the program stars in the gravity-sensitive (V-B)-(L-U) diagram is very narrow, log g =4.2 ± 0.3, which means that these stars are probably all dwarfs, with only very few possible subgiants.The absolute-magnitude calibration was derived by using the data of Cayrel de Strobel et al. (1980) and of Cayrel de Strobel and Bentolila (1983). From their [Fe/H]-catalogue we took all stars with known distances, and within the parameter range of our program stars, to construct an empirical MV - Teff relation. This relation was used to derive distances for the stars in SA141.These distances are plotted against [Fe/H] in Fig. 2. The diagram clearly shows the correlation between distance and metallicity, suggesting for this particular sample a gradient of −0.6 in [Fe/H] over the first 500 pc. Similar values were found in the Basel RGU program (cf. Trefzger, 1981) and by Blaauw and Garmany (1975).

scholarly journals The Evolution of Contact Binaries

1976 ◽  
Vol 73 ◽  
pp. 343-346 ◽  
Author(s):  
F. Van'T Veer
Keyword(s):  
Large Scale ◽  
Main Sequence ◽  
Mean Lifetime ◽  
Mass Outflow ◽  
Contact Binaries ◽  
Contact Binary ◽  
Solar Type ◽  
The Mean ◽  
The One ◽  
Almost All

Asymmetric light curves and period changes of contact binaries can be explained by large-scale prominence activity. From the mass outflow accompanying this activity the mean lifetime of a contact binary is estimated as 5 × 107 yr. From the lifetimes of contact binaries and normal solar type dwarfs on the one hand and the proportion of the former among the latter in equal volumes of space on the other hand, it is concluded that (almost) all solar type dwarfs were contact binaries at the beginning of their main sequence life.

STM studies of crystal growth

1991 ◽  
Vol 49 ◽  
pp. 374-375
Author(s):  
M. G. Lagally
Keyword(s):  
Crystal Growth ◽  
Molecular Beam ◽  
Chemical Vapor ◽  
Sputter Deposition ◽  
Field Of View ◽  
Scanning Tunneling ◽  
Wide Field ◽  
Tunneling Microscopy ◽  
Wide Field Of View ◽  
The One

It has been recognized since the earliest days of crystal growth that kinetic processes of all Kinds control the nature of the growth. As the technology of crystal growth has become ever more refined, with the advent of such atomistic processes as molecular beam epitaxy, chemical vapor deposition, sputter deposition, and plasma enhanced techniques for the creation of “crystals” as little as one or a few atomic layers thick, multilayer structures, and novel materials combinations, the need to understand the mechanisms controlling the growth process is becoming more critical. Unfortunately, available techniques have not lent themselves well to obtaining a truly microscopic picture of such processes. Because of its atomic resolution on the one hand, and the achievable wide field of view on the other (of the order of micrometers) scanning tunneling microscopy (STM) gives us this opportunity. In this talk, we briefly review the types of growth kinetics measurements that can be made using STM. The use of STM for studies of kinetics is one of the more recent applications of what is itself still a very young field.

Auto Markets in the World and Strategy of Japan’s Companies

2019 ◽  
Vol 10 (10) ◽  
pp. 1003-1008
Author(s):  
Hiroyuki Matsuoka ◽  
Keyword(s):  
Saudi Arabia ◽  
Electric Vehicle ◽  
New Technologies ◽  
Auto Industry ◽  
Domestic Market ◽  
Automatic Driving ◽  
The World ◽  
Almost All ◽  
Made In

In the world auto market, top three companies are VW(Volkswagen), Runault-Nissan-Mistubishi, and Toyota. About some selected countries and areas, China, England, Italy, Australia, Germany, Turkey, Russia, Sweden, USA, Brazil, UAE, Japan, Vietnam and Thailand are more competitive. However, the situation is different. Seeing monopolistic market countries and areas, Saudi Arabia, Taiwan, Korea, Malaysia, France, India, and Pakistan, in particular, the influence of Japan to Taiwan, India, and Pakistan is very big. But in Korea and France, their own companies’ brands occupy the market. In Japan domestic market, the overall situation is competitive. Almost all vehicles made in Japan are Japanese brand. From now on, we have to note the development of electric vehicle (EV) and other new technologies such as automatic driving and connected car. That is because they will give a great impact on the auto industry and market of Japan. Now Japan’s auto industry is going to be consolidated into three groups, Honda, Toyota group, and Renault-Nissan-Mitsubishi group for seeking the scale merit of economy. Therefore, I will pay attention to the worldwide development of EV and other new technologies and the reorganization of auto companies groups.

Simulation of the internal temperature in the Passol Laboratory, University of Debrecen

2012 ◽  
Vol 3 (1) ◽  
pp. 63-73 ◽  
Author(s):  
I. Csáky ◽  
F. Kalmár
Keyword(s):  
Temperature Variation ◽  
Air Temperature ◽  
Indoor Air ◽  
Storage Capacity ◽  
Building Structures ◽  
Internal Temperature ◽  
The One ◽  
Heavy Structure ◽  
East West ◽  
Made In

Abstract Nowadays the facades of newly built buildings have significant glazed surfaces. The solar gains in these buildings can produce discomfort caused by direct solar radiation on the one hand and by the higher indoor air temperature on the other hand. The amplitude of the indoor air temperature variation depends on the glazed area, orientation of the facade and heat storage capacity of the building. This paper presents the results of a simulation, which were made in the Passol Laboratory of University of Debrecen in order to define the internal temperature variation. The simulation proved that the highest amplitudes of the internal temperature are obtained for East orientation of the facade. The upper acceptable limit of the internal air temperature is exceeded for each analyzed orientation: North, South, East, West. Comparing different building structures, according to the obtained results, in case of the heavy structure more cooling hours are obtained, but the energy consumption for cooling is lower.

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