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.

Luminosity and Intrinsic Color Calibration of Main-Sequence Stars With 2Mass Photometry: All Sky Local Extinction

2003 ◽  
Vol 12 (4) ◽  
Author(s):  
Jens Knude ◽  
Claus Fabricius
Keyword(s):  
Color Index ◽  
Main Sequence ◽  
Absolute Magnitude ◽  
Interstellar Extinction ◽  
Local Extinction ◽  
Sequence Information ◽  
Main Sequence Stars ◽  
Color Calibration

AbstractWe present a new color index vs. absolute magnitude calibration of 2MASS JHK photometry. For the A0 to ~G5 and M segments of the main sequence information on the amount of interstellar extinction and its location in space may be obtained.

scholarly journals Magnetic inhibition of convection in O-star envelopes

2019 ◽  
Vol 487 (3) ◽  
pp. 3904-3913 ◽  
Author(s):  
James MacDonald ◽  
Véronique Petit
Keyword(s):  
Magnetic Field ◽  
Main Sequence ◽  
Main Sequence Stars ◽  
Lower Field ◽  
Dipole Strength ◽  
Evolved Stars ◽  
Hydrostatic Balance ◽  
Stellar Envelopes ◽  
Stars Evolution ◽  
Good Agreement

ABSTRACT It has been suggested that the absence of macroturbulence in the atmosphere of NGC 1624−2 is due its strong magnetic field (the strongest known for a massive O star) suppressing convection in its outer layers, removing the mechanism thought responsible for the observed macroturbulence in stars with lower field strengths. Here, we develop and apply a criterion for a uniform magnetic field to suppress convection in stellar envelopes in which radiation pressure is a significant contributor to hydrostatic balance. We find upper mass limits of ∼55 and ∼30 M⊙ for magnetic suppression to be possible in zero-age main-sequence and terminal-age main-sequence stars, respectively. For evolved stars, magnetic suppression of convection can significantly alter the stars’ evolution. For NGC 1624−2, we find that a polar dipole strength of 16.5 ± 5.9 kG is required to suppress convection, in good agreement with the value ∼20 kG measured by spectropolarimetry.

Supersolar metallicity in G0–G3 main-sequence stars with V < 15. II. An extension of the sample

2020 ◽  
Vol 493 (4) ◽  
pp. 5807-5815
Author(s):  
M Chávez ◽  
C Tapia-Schiavon ◽  
E Bertone ◽  
R López-Valdivia
Keyword(s):  
Main Sequence ◽  
Wavelength Region ◽  
Interstellar Extinction ◽  
Main Sequence Stars ◽  
Data Set ◽  
Class V ◽  
Full Sample ◽  
Gaia Dr2 ◽  
Temperature Surface ◽  
Good Agreement

ABSTRACT We present the spectroscopic analysis at intermediate resolution of a new sample of 146 Sun-like stars (of spectral types G0–G3 and luminosity class V), which complements the data set of 233 targets previously investigated. Aimed at identifying objects with supersolar metallicity, we conducted observations at the Observatorio Astrofísico Guillermo Haro and derived the basic stellar atmospheric parameters, namely the effective temperature, surface gravity, and global metallicity, based on a set of absorption spectroscopic indices in the wavelength region 3800–4800 Å. The newly derived set of parameters is in good agreement with previous determinations collected from sources in the literature. Considering the full sample of our investigation (379 stars), we also compared the effective temperatures of stars in common (354 objects) with Gaia DR2 for which temperatures are available, and found that, on average, our values are about 100 K higher. We show that most of the largest temperature discrepancies can plausibly be ascribed to interstellar extinction effects on Gaia’s photometry. Finally, within the working sample we found four more stars that present supermetallicity, one of which was previously reported in the literature.

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 VINCI/VLTI Observations of Main Sequence Stars

2004 ◽  
Vol 219 ◽  
pp. 80-84
Author(s):  
Pierre Kervella ◽  
Frédéric Thévenin ◽  
Pierre Morel ◽  
Janine Provost ◽  
Gabrielle Berthomieu ◽  
...  
Keyword(s):  
Main Sequence ◽  
Extrasolar Planets ◽  
Physical Processes ◽  
Main Sequence Stars ◽  
M Dwarfs ◽  
The Past ◽  
Wide Range ◽  
Solar Type ◽  
The Universe ◽  
Angular Diameters

Main Sequence (MS) stars are by far the most numerous class in the Universe. They are often somewhat neglected as they are relatively quiet objects (but exceptions exist), though they bear testimony of the past and future of our Sun. An important characteristic of the MS stars, particularly the solar-type ones, is that they host the large majority of the known extrasolar planets. Moreover, at the bottom of the MS, the red M dwarfs pave the way to understanding the physics of brown dwarfs and giant planets. We have measured very precise angular diameters from recent VINCI/VLTI interferometric observations of a number of MS stars in the K band, with spectral types between A1V and M5.5V. They already cover a wide range of effective temperatures and radii. Combined with precise Hipparcos parallaxes, photometry, spectroscopy as well as the asteroseismic information available for some of these stars, the angular diameters put strong constraints on the detailed models of these stars, and therefore on the physical processes at play.

scholarly journals Analysis of the Hipparcos Sample of Eclipsing Binaries Parallaxes And Multiplicity

1998 ◽  
Vol 11 (1) ◽  
pp. 569-569
Author(s):  
E. Oblak ◽  
M. Kurpinska-Winiarska ◽  
T. Kundera ◽  
S. Zola ◽  
T.Z. Dworak
Keyword(s):  
Main Sequence ◽  
Eclipsing Binaries ◽  
Main Sequence Stars ◽  
Eclipsing Binary ◽  
Visual Component ◽  
Inadequate Knowledge ◽  
Two Systems ◽  
Trigonometric Parallaxes ◽  
Good Agreement

The Hipparcos astrometric satellite observed 993 known eclipsing binaries. Prom 1048 eclipsing binaries of the Brancewicz and Dworak ’s catalogue (1980), there are only 368 observed by Hipparcos, as the others are too faint. On the basis of these common stars, we have undertaken the comparison ofthe satellite parallaxes with the photometric ones. We obtain a good agreement between the two systems with a mean dispersion of 5 mas. The greatest dispersion is for the goup of eclipsing binaries of the EW type. The eclipsing binaries of this group have a mass-luminosity relation different from those of the main sequence stars. An inadequate knowledge of the component spectra of an eclipsing binary seems to be one of the most important cause of discrepancies. For some brightest stars, the new Hipparcos trigonometric parallaxes differ very significantly from those previously known from ground based measurements. It seems that the presence of a close visual components causes statistically an underestimation of photometric or overestimation of Hipparcos parallaxes. 172 Hipparcos eclipsing binaries have a close visual component, generally less than 10 arcseconds apart. The list of these stars for various stellar groups and a brief analysis are presented.

scholarly journals Stellar radii from long-baseline interferometry

2008 ◽  
Vol 4 (S252) ◽  
pp. 405-411
Author(s):  
Pierre Kervella
Keyword(s):  
Main Sequence ◽  
Main Sequence Stars ◽  
Long Baseline ◽  
Nearby Stars ◽  
Low Mass ◽  
Stellar Models ◽  
Powerful Constraint ◽  
Percent Accuracy ◽  
Angular Diameters

AbstractLong baseline interferometers now measure the angular diameters of nearby stars with sub-percent accuracy. They can be translated in photospheric radii when the parallax is known, thus creating a novel and powerful constraint for stellar models. I present applications of interferometric radius measurements to the modeling of main sequence stars. Over the last few years, we obtained accurate measurements of the linear radius of many of the nearest stars: Procyon A, 61 Cyg A & B, α Cen A & B, Sirius A, Proxima. . . Firstly, I describe the example of our modeling of Procyon A (F5IV-V) with the CESAM code, constrained using spectrophotometry, the linear radius, and asteroseismic frequencies. I also present our recent results on the low-mass 61 Cyg system (K5V+K7V), for which asteroseismic frequencies have not been detected yet.

Sign in / Sign up

Export Citation Format

Share Document