scholarly journals The Drake Equation as a Function of Spectral Type and Time

2018 ◽  
pp. 307-319 ◽  
Author(s):  
Jacob Haqq-Misra ◽  
Ravi K. Kopparapu
Keyword(s):  
Spectral Type

Some Results of the Spectroscopic Study of Four Close Binary Systems of Early Spectral Types

1965 ◽  
Vol 5 ◽  
pp. 120-130
Author(s):  
T. S. Galkina
Keyword(s):  
Spectroscopic Study ◽  
Spectral Type ◽  
Spectroscopic Investigation ◽  
Binary Systems ◽  
Quantitative Information ◽  
Close Binary ◽  
Physical Parameters ◽  
Absorption And Emission ◽  
Close Binary Systems ◽  
Quantitative Estimates

It is necessary to have quantitative estimates of the intensity of lines (both absorption and emission) to obtain the physical parameters of the atmosphere of components.Some years ago at the Crimean observatory we began the spectroscopic investigation of close binary systems of the early spectral type with components WR, Of, O, B to try and obtain more quantitative information from the study of the spectra of the components.

The Eclipsing Binary WX Eridani

1979 ◽  
Vol 46 ◽  
pp. 385
Author(s):  
M.B.K. Sarma ◽  
K.D. Abhankar
Keyword(s):  
Light Curve ◽  
Spectral Type ◽  
Orbital Period ◽  
Primary Component ◽  
Light Curves ◽  
Absorption Feature ◽  
Primary Star ◽  
Eclipsing Binary ◽  
The Times ◽  
Phase Angles

AbstractThe Algol-type eclipsing binary WX Eridani was observed on 21 nights on the 48-inch telescope of the Japal-Rangapur Observatory during 1973-75 in B and V colours. An improved period of P = 0.82327038 days was obtained from the analysis of the times of five primary minima. An absorption feature between phase angles 50-80, 100-130, 230-260 and 280-310 was present in the light curves. The analysis of the light curves indicated the eclipses to be grazing with primary to be transit and secondary, an occultation. Elements derived from the solution of the light curve using Russel-Merrill method are given. From comparison of the fractional radii with Roche lobes, it is concluded that none of the components have filled their respective lobes but the primary star seems to be evolving. The spectral type of the primary component was estimated to be F3 and is found to be pulsating with two periods equal to one-fifth and one-sixth of the orbital period.

On the nature of radio emission from stars of late spectral type

2003 ◽  
Vol 173 (1) ◽  
pp. 106 ◽  
Author(s):  
Aleksandr V. Stepanov
Keyword(s):  
Radio Emission ◽  
Spectral Type

scholarly journals Observed Relations Between Physical Properties and MK Classification as Functions of Metal Abundance for F5-K4 Stars

1976 ◽  
Vol 72 ◽  
pp. 75-78
Author(s):  
M. Grenon
Keyword(s):  
Physical Properties ◽  
Spectral Range ◽  
Spectral Type ◽  
Photometric System ◽  
Luminosity Class ◽  
Empirical Relations ◽  
Metal Abundance ◽  
Systematic Effects ◽  
The Absolute ◽  
Absolute Magnitudes

The Geneva photometric system has been calibrated in terms of [M/H], θeff, Mv in the spectral range F5 to K4. As the spectral type is a datum generally available, we derive empirical relations showing the coupling of θeff and [M/H] at given spectral type and luminosity class. Similar relations are offered for the absolute magnitudes and provide a more accurate means for deriving spectroscopic parallaxes. Systematic effects on the estimation of the luminosity class are also shown.

scholarly journals A Deep Large area Search for Low Luminosity Stars

1998 ◽  
Vol 11 (1) ◽  
pp. 435-435
Author(s):  
Hugh R.A. Jones ◽  
Mike R.S. Hawkins
Keyword(s):  
Spectral Type ◽  
Low Temperatures ◽  
Current Model ◽  
Brown Dwarfs ◽  
Evolutionary Models ◽  
Spectral Indices ◽  
Late Type ◽  
Brown Dwarf ◽  
Large Area ◽  
M Dwarfs

In a recent survey for faint red stars from a digital stack of Schmidt plates a number of candidate objects were identified. Parallax’s for three of these objects have been reported showing them to have luminosities which interpreted within the available evolutionary models indicate them to be good brown dwarf candidates. Here we examine spectra of these objects and others from the plate stack. Using standard spectral indices we find that for a given spectral type their spectra are more consistent with the Pleiades brown dwarfs (PPL 15, Teide 1 and Calar 3) than with standard late-type M dwarfs. Our interpretation is that this is due to their selection by RF IN colours which at values > 3 preferentially selects objects with relatively low gravities. For late-type M dwarfs and brown dwarfs low gravities are expected to be a reliable indication of youth. We also notice that the stack objects generally have strong FeH absorption for their spectral type. Current model atmospheres suggest that FeH strongly increases in strength toward lower metallicities and lower temperatures. We believe that this is not consistent with the available observational evidence from late-type M dwarfs. It is possible that solid Fe is forming inthe low temperature atmospheres relatively depleting FeH strengths toward lower temperatures. We find some evidence that for dwarfs at low temperatures dust formation is less prevalent in lower gravity objects suggesting that dwarfs at low temperatures stronger FeH may be an indication of youth. In addition to the spectral evidence the three stack objects whose parallax’s have been measured show small tangential velocities which is a further indication of youth.

scholarly journals Stellar 5 min Oscillations

1983 ◽  
Vol 66 ◽  
pp. 469-486
Author(s):  
Jørgen Christensen-Dalsgaard ◽  
Søren Frandsen
Keyword(s):  
Spectral Type ◽  
Main Sequence ◽  
Total Flux ◽  
The Sun ◽  
Major Fraction ◽  
Main Sequence Stars ◽  
Red Supergiants

AbstractEstimates are given for the amplitudes of stochastically excited oscillations in Main Sequence stars and cool giants; these were obtained using the equipartition between convective and pulsational energy which was originally proposed by Goldreich and Keeley. The amplitudes of both velocity and luminosity perturbation generally increase with increasing mass along the Main Sequence as long as convection transports a major fraction of the total flux, and the amplitudes also increase with the age of the model. The 1.5 Mʘ ZAMS model, of spectral type F0, has velocity amplitudes ten times larger than those found in the Sun. For very luminous red supergiants luminosity amplitudes of up to about 0ṃ.1 are predicted, in rough agreement with observations presented by Maeder.

Emergent polarization structure in spectral lines from rotating stars of spectral type B

1984 ◽  
Vol 107 (1) ◽  
pp. 61-69 ◽  
Author(s):  
Sean J. McKenna
Keyword(s):  
Spectral Type ◽  
Spectral Lines ◽  
Rotating Stars ◽  
Type B ◽  
Polarization Structure

Correlation of molecular structure, EPR and moessbauer spectral type and reduction potential in low-spin ferriheme models of the cytochromes

2003 ◽  
Vol 96 (1) ◽  
pp. 248
Author(s):  
F.Ann Walker ◽  
Liliya Yatsunyk ◽  
Michael D. Carducci ◽  
Thomas Teschner ◽  
Volker Schënemann ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Spectral Type ◽  
Reduction Potential

scholarly journals FURTHER DEFINING SPECTRAL TYPE “Y” AND EXPLORING THE LOW-MASS END OF THE FIELD BROWN DWARF MASS FUNCTION

2012 ◽  
Vol 753 (2) ◽  
pp. 156 ◽  
Author(s):  
J. Davy Kirkpatrick ◽  
Christopher R. Gelino ◽  
Michael C. Cushing ◽  
Gregory N. Mace ◽  
Roger L. Griffith ◽  
...  
Keyword(s):  
Spectral Type ◽  
Mass Function ◽  
Brown Dwarf ◽  
Low Mass

scholarly journals Constraining the multiplicity statistics of the coolest brown dwarfs: binary fraction continues to decrease with spectral type

2018 ◽  
Vol 479 (2) ◽  
pp. 2702-2727 ◽  
Author(s):  
Clémence Fontanive ◽  
Beth Biller ◽  
Mariangela Bonavita ◽  
Katelyn Allers
Keyword(s):  
Spectral Type ◽  
Brown Dwarfs
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