scholarly journals Effective temperature vs. line-depth ratio for ELODIE spectra: Gravity and rotational velocity effects

2007 ◽  
Vol 328 (9) ◽  
pp. 938-947 ◽  
Author(s):  
K. Biazzo ◽  
A. Frasca ◽  
S. Catalano ◽  
E. Marilli
Keyword(s):  
Effective Temperature ◽  
Rotational Velocity ◽  
Depth Ratio ◽  
Line Depth

scholarly journals Determining the evolutionary stage of HD163899 on the basis of its oscillation spectrum

2015 ◽  
Vol 11 (A29B) ◽  
pp. 567-572
Author(s):  
Jakub Ostrowski ◽  
Jadwiga Daszyńska-Daszkiewicz ◽  
Henryk Cugier
Keyword(s):  
Effective Temperature ◽  
Main Sequence ◽  
Rotational Velocity ◽  
Evolutionary Stage ◽  
Oscillation Spectrum ◽  
New Interpretation ◽  
Massive Models

AbstractWe present the new interpretation of the oscillation spectrum of HD 163899 based on the new determinations of the effective temperature, mass-luminosity ratio and rotational velocity. These new parameters strongly prefer the more massive models than previously considered. Now it is also possible that the star could be in the main sequence stage. Using the oscillation spectrum as a gauge, we intend to establish which stage of evolution corresponds better to HD 163899.

scholarly journals Quantitative spectroscopic analyses in the IACOB+OWN project: Massive O-type stars in the Galaxy with the current Gaia information

2016 ◽  
Vol 12 (S329) ◽  
pp. 407-407
Author(s):  
Gonzalo Holgado ◽  
Sergio Simón-Díaz ◽  
Rodolfo Barbá
Keyword(s):  
Effective Temperature ◽  
Optical Spectrum ◽  
Spectroscopic Analysis ◽  
Rotational Velocity ◽  
Helium Abundance ◽  
Spectroscopic Parameters ◽  
Spectroscopic Analyses ◽  
The Galaxy ◽  
Complete Set

We present the results from the quantitative spectroscopic analysis of ~280 likely single O stars targeted by the IACOB and OWN surveys. This implies the largest sample of Galactic O-type stars analyzed homogeneously to date. We used the iacob-broad and iacob-gbat tools (see Simón-Díaz et al. 2011,2015) to obtain the complete set of spectroscopic parameters which can be determined from the optical spectrum of O-type stars: projected rotational velocity (v sin i), macroturbulence velocity (vmac), effective temperature (Teff), gravity (logg), wind-strength (logQ), helium abundance (YHe), microturbulence (ξt), and the exponent of the wind-law (β).

scholarly journals Results from a recent stellar rotation census of B stars

2010 ◽  
Vol 6 (S272) ◽  
pp. 89-90
Author(s):  
Wenjin Huang ◽  
Douglas R. Gies ◽  
M. Virginia McSwain
Keyword(s):  
Effective Temperature ◽  
Rotation Rate ◽  
Rotation Speed ◽  
Rotational Velocity ◽  
Rotation Velocity ◽  
Be Stars ◽  
Stellar Rotation ◽  
B Stars ◽  
Critical Rotation ◽  
Critical Rotation Speed

AbstractIn an analysis of the rotational properties of more than 1100 B stars (~660 cluster and ~500 field B stars), we determine the projected rotational velocity (V sin i), effective temperature, gravity, mass, and critical rotation speed for each star. The new data provide us a solid observational base to explore many hot topics in this area: Why do field B stars rotate slower than cluster B stars? How fast do B stars rotate when they are just born? How fast can B stars rotate before they become Be stars? How does the rotation rate of B stars change with time? Does the evolutionary change in rotation velocity lead to the Be phenomenon? Here we report the results of our efforts in searching for answers to these questions based on the latest B star census.

scholarly journals Statistical analysis of the new catalogue of CP stars

2018 ◽  
pp. 223-227
Author(s):  
S. Ghazaryan ◽  
G. Alecian ◽  
A. A. Hakobyan
Keyword(s):  
Statistical Analysis ◽  
Effective Temperature ◽  
Rotational Velocity ◽  
Rank Correlation ◽  
High Resolution Spectroscopy ◽  
Physical Parameters ◽  
Chemical Abundances ◽  
Spearman’S Rank Correlation ◽  
Chemically Peculiar Stars ◽  
Anderson Darling

This talk is devoted to the statistical analysis of the new catalogue of Chemically Peculiar stars compiled from papers, where chemical abundances of those stars were given. The catalogue contains chemical abundances and physical parameters of 428 stars based on high-resolution spectroscopy data. Spearman's rank correlation test was applied for 416 CP (108 HgMn, 188 ApBp and 120 AmFm) stars and the correlation between chemical abundances and different physical parameters (effective temperature, surface gravity and rotational velocity) was checked. From dozens interesting cases we secluded four cases: the Mn peculiarities in HgMn stars, the Ca correlation with respect to effective temperature in AmFm stars, the case of helium and iron in ApBp stars. We applied also Anderson-Darling (AD) test on ApBp stars to check if multiplicity is a determinant parameter for abundance peculiarities.

scholarly journals HDO and SO2 thermal mapping on Venus

2020 ◽  
Vol 639 ◽  
pp. A69 ◽  
Author(s):  
T. Encrenaz ◽  
T. K. Greathouse ◽  
E. Marcq ◽  
H. Sagawa ◽  
T. Widemann ◽  
...  
Keyword(s):  
Local Time ◽  
Mixing Ratio ◽  
Echelle Spectrograph ◽  
Imaging Spectrometer ◽  
Infrared Telescope ◽  
Depth Ratio ◽  
Time Period ◽  
Telescope Facility ◽  
Line Depth

Since January 2012, we have been monitoring the behavior of sulfur dioxide and water on Venus, using the Texas Echelon Cross-Echelle Spectrograph imaging spectrometer at the NASA InfraRed Telescope Facility (IRTF, Mauna Kea Observatory). Here, we present new data recorded in February and April 2019 in the 1345 cm−1 (7.4 μm) spectral range, where SO2, CO2, and HDO (used as a proxy for H2O) transitions were observed. The cloud top of Venus was probed at an altitude of about 64 km. As in our previous studies, the volume mixing ratio (vmr) of SO2 was estimated using the SO2/CO2 line depth ratio of weak transitions; the H2O volume mixing ratio was derived from the HDO/CO2 line depth ratio, assuming a D/H ratio of 200 times the Vienna standard mean ocean water. As reported in our previous analyses, the SO2 mixing ratio shows strong variations with time and also over the disk, showing evidence for the formation of SO2 plumes with a lifetime of a few hours; in contrast, the H2O abundance is remarkably uniform over the disk and shows moderate variations as a function of time. We have used the 2019 data in addition to our previous dataset to study the long-term variations of SO2 and H2O. The data reveal a long-term anti-correlation with a correlation coefficient of −0.80; this coefficient becomes −0.90 if the analysis is restricted to the 2014–2019 time period. The statistical analysis of the SO2 plumes as a function of local time confirms our previous result with a minimum around 10:00 and two maxima near the terminators. The dependence of the SO2 vmr with respect to local time shows a higher abundance at the evening terminator with respect to the morning. The dependence of the SO2 vmr with respect to longitude exhibits a broad maximum at 120–200° east longitudes, near the region of Aphrodite Terra. However, this trend has not been observed by other measurements and has yet to be confirmed.

scholarly journals Gravity darkening in stars with surface differential rotation

2017 ◽  
Vol 606 ◽  
pp. A32 ◽  
Author(s):  
J. Zorec ◽  
M. Rieutord ◽  
F. Espinosa Lara ◽  
Y. Frémat ◽  
A. Domiciano de Souza ◽  
...  
Keyword(s):  
Differential Rotation ◽  
Effective Temperature ◽  
Rotational Velocity ◽  
Viewing Angle ◽  
Rotating Stars ◽  
Stellar Rotation ◽  
Fundamental Parameters ◽  
Effective Gravity ◽  
Unique Interpretation

Context. The interpretation of stellar apparent fundamental parameters (viewing-angle dependent) requires that they be treated consistently with the characteristics of their surface rotation law. Aims. We aim to develop a model to determine the distribution of the effective temperature and gravity, which explicitly depend on the surface differential rotation law and on the concomitant stellar external geometry. Methods. The basic assumptions in this model are: a) the external stellar layers are in radiative equilibrium; b) the emergent bolometric flux is anti-parallel with the effective gravity; c) the angular velocity in the surface obeys relations like Ω(θ) = Ωo [ 1 + αΥ(θ,k) ] where Υ(θ,k) = coskθ or sinkθ, and where (α,k) are free parameters. Results. The effective temperature varies with co-latitude θ, with amplitudes that depend on the differential-rotation law through the surface effective gravity and the gravity-darkening function (GDF). Although the derived expressions can be treated numerically, for some low integer values of k, analytical forms of the integral of characteristic curves, on which the determination of the GDF relies, are obtained. The effects of the quantities (η,α,k) (η = ratio between centrifugal and gravitational accelerations at the equator) on the determination of the Vsini parameter and on the gravity-darkening exponent are studied. Depending on the values of (η,α,k) the velocity V in the derived Vsini may strongly deviate from the equatorial rotational velocity. It is shown that the von Zeipel’s-like gravity-darkening exponent β1 depends on all parameters (η,α,k) and that its value also depends on the viewing-angle i. Hence, there no unique interpretation of this exponent determined empirically in terms of (i,α). Conclusions. We stress that the data on rotating stars should be analyzed by taking into account the rotational effects through the GDF, by assuming k = 2 as a first approximation. Instead of the classic pair (η,β1), it would be more useful to determine the quantities (η,α,i) to characterize stellar rotation.

scholarly journals Angular Diameters of O- and B-type Stars

2014 ◽  
Vol 9 (S307) ◽  
pp. 293-294
Author(s):  
Kathryn Gordon ◽  
Douglas Gies ◽  
Gail Schaefer
Keyword(s):  
Stellar Evolution ◽  
Effective Temperature ◽  
Angular Resolution ◽  
Rotational Velocity ◽  
Angular Diameter ◽  
High Angular Resolution ◽  
Long Baseline ◽  
Evolutionary State ◽  
The World ◽  
Angular Diameters

AbstractWe are observing a sample of 10 O-type stars and 60 B-type stars to determine angular diameters using the Center for High Angular Resolution Astronomy (CHARA) Array, the foremost optical long baseline interferometer in the world. Our goal is to establish accurate stellar parameters to test modern theories of stellar evolution that include rotation. We will combine our stellar angular diameter measurements with flux and line measurements from spectroscopy, projected rotational velocities, and distances to determine radius, effective temperature, luminosity, equatorial rotational velocity, and evolutionary mass. Knowing these properties will allow us to place the stars in a Hertzsprung-Russell diagram and obtain estimates for the age and evolutionary state.

scholarly journals Spectroscopic survey of Kepler stars: high-resolution observations of A- and F-type stars

2013 ◽  
Vol 9 (S301) ◽  
pp. 467-468
Author(s):  
E. Niemczura ◽  
B. Smalley ◽  
S. Murphy ◽  
G. Catanzaro ◽  
K. Uytterhoeven ◽  
...  
Keyword(s):  
Chemical Composition ◽  
High Resolution ◽  
Effective Temperature ◽  
Spectroscopic Data ◽  
Rotational Velocity ◽  
Surface Gravity ◽  
Working Groups ◽  
Space Data ◽  
Temperature Surface

AbstractBasic stellar parameters such as effective temperature, surface gravity, chemical composition, and projected rotational velocity, are important to classify stars and are crucial for successful asteroseismic modelling. However, the Kepler space data do not provide such information. Therefore, ground-based spectral and multi-colour observations of Kepler asteroseismic targets are necessary to complement the space data. For this purpose, in coordination with the KASC ground-based observational Working Groups, high-resolution spectroscopic data for more than 500 B, A, F and G-type stars were collected.

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