scholarly journals Effective Temperatures and Angular Diameters of A–G Main Sequence Stars

1993 ◽  
Vol 137 ◽  
pp. 153-155
Author(s):  
I.N. Glushneva ◽  
I.B. Voloshina ◽  
L.N. Knyazeva
Keyword(s):  
Spectral Type ◽  
Main Sequence ◽  
Main Sequence Stars ◽  
Flux Method ◽  
Effective Temperatures ◽  
Angular Diameters

AbstractFor 9 stars of A5–G2 spectral type interval IV and V luminosity classes effective temperatures, bolometric corrections, radii, angular diameters and luminosities were obtained by means of the infrared flux method in the modification by Blackwell et al. (1980).

scholarly journals Colours and Teff of Main Sequence Stars Covering the Galactic Metallicity Range

1995 ◽  
Vol 164 ◽  
pp. 368-368
Author(s):  
A. Alonso ◽  
S. Arribas ◽  
C. Martínez-Roger
Keyword(s):  
Temperature Scale ◽  
Main Sequence ◽  
Main Sequence Stars ◽  
Flux Method ◽  
Absolute Flux ◽  
The Galaxy ◽  
Effective Temperatures ◽  
Bolometric Correction ◽  
Flux Calibration ◽  
Hr Diagram

We present the results of a general programme aimed to study the effects of metallicity on the temperature scale of late main sequence stars (F0-K5). A sample of approximately 400 stars with published UBV(RI) and ubvy – β photometry has been collected from the literature. A three years campaign of observations (Alonso et al. 1994b) was carried out to obtain JHK photometry in order to apply the InfraRed Flux Method (IRFM) to derive effective temperatures. The effect of metallicity on Colour-Colour IR diagrams is discussed. The absolute flux calibration in the IR was revised in Alonso et al. (1994a). The effect of metallicity on the bolometric correction has been studied in Alonso et al. (1995) in order to derive bolometric fluxes. The temperatures have been derived by applying the IRFM using new Kurucz models. Teff = f(Colours, [Fe/H], log(g)) relations are obtained for dwarfs covering the ranges 4000K ≤ Teff ≤ 8000K, 3.5 ≤ logg ≤ 5.00, +0.5 ≤ [Fe/H] ≤ −3.00 which expands considerably the database of previous works. These relations are used to check atmosphere models through the analysis of UBV RIJH Kubvy – β synthetic photometry in combination with the IRFM. The transformation from the theoretical HR diagram into an observational one is analyzed with the new relations. The influence of these points on the study of the evolution of the Galaxy is briefly discussed.

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.

A Discussion on astronomy in the ultraviolet - The ultraviolet spectrum of B-type supergiants

1975 ◽  
Vol 279 (1289) ◽  
pp. 429-442
Keyword(s):  
High Resolution ◽  
Spectral Type ◽  
Main Sequence ◽  
Ultraviolet Spectrum ◽  
Absorption Lines ◽  
Light Elements ◽  
Main Sequence Stars ◽  
Complete Identification ◽  
Constant Strength

The broad, steep-sided absorption lines in B-type supergiant spectra are stronger than the absorption lines in main-sequence stars. In addition to lines from the second, third and fourth spectra of the light elements and the metals there is a broad, pointed feature at 1720 A which has constant strength in the B-type supergiants regardless of spectral type. The complete identification of this blend is not known. At high resolution the ultraviolet resonance lines of C iv, N v, Si hi and Si iv in the spectra of OB supergiants are shortward displaced by velocities up to 1800 km s-1 indicating the presence of an escaping atmosphere. At type B5 the expanding atmosphere is moving at about 120 km s-1 which means that the material is probably brought to rest before it escapes from the star. Evidence is presented of the presence of a stationary shell around the B5Ia supergiant q Canis Majoris as well as a slowly expanding atmosphere.

scholarly journals On the Accuracy of Spectral Classifications of Main-Sequence Stars

1973 ◽  
Vol 50 ◽  
pp. 52-59
Author(s):  
W. Gliese
Keyword(s):  
Spectral Type ◽  
Main Sequence ◽  
Standard Errors ◽  
Main Sequence Stars ◽  
M Dwarfs ◽  
Spectral Class ◽  
Classification Errors ◽  
Nearby Stars

By examining the observed dispersion in (colour, spectral type) relations, classification errors have been derived from the data of nearby stars. The comparisons of the colour deviations observed in spectral regions of large variations of colour with type with the deviations in regions of small variations give the following standard errors in units of a tenth of a spectral class: For K dwarfs ±0.6 (MK), ±1.2 (Mt. Wilson), ±0.7 (Kuiper); for early M dwarfs ±0.9: (MK), ±0.7 (Mt. Wilson), ±0.5: (Kuiper); and for late M dwarfs ±0.7 (Kuiper).

scholarly journals The Rotation of Pre-Main Sequence Stars

1980 ◽  
Vol 5 ◽  
pp. 835-837
Author(s):  
Leonard V. Kuhi ◽  
Stuart Vogel
Keyword(s):  
Angular Momentum ◽  
Spectral Type ◽  
Main Sequence ◽  
Rotational Velocity ◽  
The Sun ◽  
Main Sequence Stars ◽  
Lower Mass ◽  
B Stars ◽  
Large Numbers ◽  
Rapid Deceleration

Kraft (1970) obtained the rotational velocities for large numbers of stars located in the field and in clusters of different ages. He noted that (a) among the field stars those stars with strong Call K emission had larger rotational velocities than those without; (b) stars in the Hyades and Pleiades (which are much younger than the field) had both larger rotational velocities and stronger Call K emission than field stars; (c) there was a pronounced break at spectral type early F in v sini as a function of spectral type and (d) the distribution of angular momentum per unit, mass J(M⊚) was proportional to M0.57 for main sequence stars with mass M > 1.5 Mʘ. This distribution predicted a v sini of ˜75 km/sec for stars of lower mass (e.g. G type) but such high velocities were not seen in the Pleiades nor in the sun. This implied a more rapid deceleration of v sini for lower mass stars and led to estimates of the e-folding time of ˜4×l08 years for stars of 1.2 M⊚ to reduce their v sini from that of the Pleiades to that of the Hyades and ˜4×l09 years to go from the Hyades to the sun’s v sini. We note also that the age of the Pleiades is approximately equal to the pre-main sequence lifetime of a 1.0 M0 star so that the zero-age main sequence cannot have J(M) α M0.57 for ˜1 M0 stars. Skumanich (1972) showed that both the Call k emission and the rotational velocity decayed as the (age)-½ for main-sequence stars.

scholarly journals An Improvement in the Visual Surface Brightness Scale for B5-F5 Main Sequence Stars

1985 ◽  
Vol 111 ◽  
pp. 523-524
Author(s):  
L. Pastori ◽  
G. Malaspina
Keyword(s):  
Surface Brightness ◽  
Color Index ◽  
Main Sequence ◽  
Surface Gravity ◽  
Main Sequence Stars ◽  
Interferometric Method ◽  
Gravity Effects ◽  
Good Agreement ◽  
Angular Diameters

Angular diameters of 593 B5-F5 main sequence stars listed in the “Catalogue of apparent diameters and absolute radii of stars” (CADARS; Fracassini et al. 1981) have been analysed in order to improve the precision of the visual surface brightness Sv. The new relations between this quantity and the color index (B-V)o turn out to be in good agreement with those found with the interferometric method (Barnes et al. 1978). Moreover, the results suggest that surface gravity effects may bias the Sv-(B-V)o relations.

Temperatures and radii of O stars

1979 ◽  
Vol 83 ◽  
pp. 103-108
Author(s):  
A. B. Underhill ◽  
L. Divan ◽  
V. Doazan ◽  
M.L. Prévot-Burnichon
Keyword(s):  
Main Sequence ◽  
Near Infrared ◽  
Stellar Atmosphere ◽  
Class Iii ◽  
Main Sequence Stars ◽  
Class V ◽  
Intermediate Band ◽  
B Stars ◽  
Luminosity Class ◽  
Effective Temperatures

Angular diameters have been estimated for 18 O and 142 B stars using absolute intermediate-band photometry in the near infrared and they have been combined with integrated fluxes to yield effective temperatures. The effective temperatures of the O stars lie in the range 30000 K to about 47000 K. For a given subtype, the luminosity class I stars have lower effective temperatures than the main-sequence stars by about 1000 K. The absorption-line spectral types of the supergiants of types O and B reflect electron temperatures which are higher than can be maintained by the integrated flux which flows through the stellar atmosphere. Distances have been estimated for all the stars and linear diameters found. The average radius for an 08 to 09.5 supergiant is about 23.3 R⊙; the radii for luminosity class III and Class V O stars lie in the range 6.8 to 10.7⊙ R.

scholarly journals Anomalous Spectral Types and Intrinsic Colors of Young Stars

2015 ◽  
Vol 10 (S314) ◽  
pp. 85-90 ◽  
Author(s):  
Mark J. Pecaut
Keyword(s):  
Infrared Spectra ◽  
Spectral Type ◽  
Main Sequence ◽  
Near Infrared ◽  
Systematic Errors ◽  
Optical Spectra ◽  
Young Stars ◽  
Main Sequence Stars ◽  
Near Infrared Spectra ◽  
Dynamical Masses

AbstractWe highlight differences in spectral types and intrinsic colors observed in pre-main sequence (pre-MS) stars. Spectral types of pre-MS stars are wavelength-dependent, with near-infrared spectra being 3-5 spectral sub-classes later than the spectral types determined from optical spectra. In addition, the intrinsic colors of young stars differ from that of main-sequence stars at a given spectral type. We caution observers to adopt optical spectral types over near-infrared types, since Hertzsprung-Russell (H-R) diagram positions derived from optical spectral types provide consistency between dynamical masses and theoretical evolutionary tracks. We also urge observers to deredden pre-MS stars with tabulations of intrinsic colors specifically constructed for young stars, since their unreddened colors differ from that of main sequence dwarfs. Otherwise, V-band extinctions as much as ~0.6 mag erroneously higher than the true extinction may result, which would introduce systematic errors in the H-R diagram positions and thus bias the inferred ages.

scholarly journals A Tale on Two Close Binaries in Pegasus

2014 ◽  
Vol 23 (2) ◽  
Author(s):  
H. V. Şenavcı ◽  
M. Yılmaz ◽  
Ö. Baştürk ◽  
İ. Özavcı ◽  
Ş. Çalışkan ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Main Sequence ◽  
Curve Analysis ◽  
Velocity Curve ◽  
Close Binaries ◽  
Main Sequence Stars ◽  
Radial Velocity Curve ◽  
Contact Binaries ◽  
Effective Temperatures

AbstractWe present the simultaneous light and radial velocity curve analysis of two contact binaries in Pegasus using the Wilson-Devinney code. The following absolute astrophysical parameters are determined: masses, radii and effective temperatures. BB Peg is a W-subtype W UMa-type binary, components of which are main sequence stars with 0.50

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