Surface Temperature and Synthetic Spectral Energy Distributions for Rotationally Deformed Stars

Lovekin, Catherine; Deupree, R. G.; Short, C. Ian

doi:10.1086/501492

Cited by 37 publications

(47 citation statements)

References 36 publications

(61 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Other formulations of this relation for conservative and nonconservative rotation laws, produce , von Zeipel 1924;Lucy 1967;Smith & Worley 1974;Kippenhahn 1977;Hadrava 1992;Maeder 1999Maeder , 2009Lovekin et al 2006;Gillich et al 2008;Dall & Sbordone 2011;Espinosa Lara & Rieutord 2011;Claret 2012). Moreover, because of the simple fact that β 1 is colatitude θ-dependent, an observed β 1 is necessarily a function of the aspect angle (Domiciano de Souza et al 2014;Rieutord 2016;Zorec et al 2016).…”

Section: The Stoeckley Effectmentioning

confidence: 99%

Critical study of the distribution of rotational velocities of Be stars

Zorec

Frémat

Souza

et al. 2016

A&A

View full text Add to dashboard Cite

Context. Among intermediate-mass and massive stars, Be stars are the fastest rotators in the main sequence (MS) and, as such, these stars are a cornerstone to validate models of structure and evolution of rotating stars. Several phenomena, however, induce under-or overestimations either of their apparent Vsin i, or true velocity V. Aims. In the present contribution we aim at obtaining distributions of true rotational velocities corrected for systematic effects induced by the rapid rotation itself, macroturbulent velocities, and binarity. Methods. We study a set of 233 Be stars by assuming they have inclination angles distributed at random. We critically discuss the methods of Cranmer and Lucy-Richardson, which enable us to transform a distribution of projected velocities into another distribution of true rotational velocities, where the gravitational darkening effect on the Vsin i parameter is considered in different ways. We conclude that iterative algorithm by Lucy-Richardson responds at best to the purposes of the present work, but it requires a thorough determination of the stellar fundamental parameters. Results. We conclude that once the mode of ratios of the true velocities of Be stars attains the value V/V c 0.77 in the main-sequence (MS) evolutionary phase, it remains unchanged up to the end of the MS lifespan. The statistical corrections found on the distribution of ratios V/V c for overestimations of Vsin i, due to macroturbulent motions and binarity, produce a shift of this distribution toward lower values of V/V c when Be stars in all MS evolutionary stages are considered together. The mode of the final distribution obtained is at V/V c 0.65. This distribution has a nearly symmetric distribution and shows that the Be phenomenon is characterized by a wide range of true velocity ratios 0.3 V/V c 0.95. It thus suggests that the probability that Be stars are critical rotators is extremely low. Conclusions. The corrections attempted in the present work represent an initial step to infer indications about the nature of the Be-star surface rotation that will be studied in the second paper of this series.

show abstract

Section: The Stoeckley Effectmentioning

confidence: 99%

Critical study of the distribution of rotational velocities of Be stars

Zorec

Frémat

Souza

et al. 2016

A&A

View full text Add to dashboard Cite

show abstract

“…Two-dimensional (2D) models of rotating stars and some observations suggest that δ < ∼ 0 (cf. Lucy 1967;Lovekin et al 2006;van Belle et al 2006;Monnier et al 2007;Zhao et al 2009). We insist on δ not being in principle the function of taking into account the change in the stellar surface from radiative to possible convective equilibrium-dominated layers because of the strong change in T eff with θ, as seems to be understood in Aufdenberg et al (2006) and Zhao et al (2009), but mainly the non-conservative nature of the rotational law in the external layers.…”

Section: The Gravity Darkening Effect In Stars With Non-conservative mentioning

confidence: 99%

“…They can be modeled by taking into account the rotationally-induced stellar geometrical deformation, but mainly the concomitant latitude-dependent surface gravity and temperature distribution: gravity darkening Lovekin et al 2006;Gillich et al 2008).…”

Section: Attainable Stellar Parametersmentioning

confidence: 99%

“…4 that T eff (θ) = C × g β GD eff , where C can be assumed to be caused by the average stellar geometrical deformation and where β GD = 0.25 + δ has a free parameter δ that should be δ ≤ 0 according to what is suggested in the literature (cf. Lucy 1967;Lovekin et al 2006;van Belle et al 2006;Monnier et al 2007;Zhao et al 2009). For models that begin evolving in the ZAMS as rigid rotators, τ and η o are also synonymous.…”

Section: Attainable Stellar Parametersmentioning

confidence: 99%

See 1 more Smart Citation

Differential rotation in rapidly rotating early-type stars

Zorec

Frémat

Souza

et al. 2010

A&A

View full text Add to dashboard Cite

Context. Since the external regions of the envelopes of rapidly rotating early-type stars are unstable to convection, a coupling may exist between the convection and the internal rotation. Aims. We explore what can be learned from spectroscopic and interferometric observations about the properties of the rotation law in the external layers of these objects. Methods. Using simple relations between the entropy and specific rotational quantities, some of which are found to be efficient at accounting for the solar differential rotation in the convective region, we derived analytical solutions that represent possible differential rotations in the envelope of early-type stars. A surface latitudinal differential rotation may not only be an external imprint of the inner rotation, but induces changes in the stellar geometry, the gravitational darkening, the aspect of spectral line profiles, and the emitted spectral energy distribution. Results. By studying the equation of the surface of stars with non-conservative rotation laws, we conclude that objects undergo geometrical deformations that are a function of the latitudinal differential rotation able to be scrutinized both spectroscopically and by interferometry. The combination of Fourier analysis of spectral lines with model atmospheres provides independent estimates of the surface latitudinal differential rotation and the inclination angle. Models of stars at different evolutionary stages rotating with internal conservative rotation laws were calculated to show that the Roche approximation can be safely used to account for the gravitational potential. The surface temperature gradient in rapid rotators induce an acceleration to the surface angular velocity. Although a nonzero differential rotation parameter may indicate that the rotation is neither rigid nor shellular underneath the stellar surface, still further information, perhaps non-radial pulsations, is needed to determine its characteristics as a function of depth.

show abstract

“…From the fitting of non-LTE stellar atmosphere's models to the observed spectroscopic data, we inferred the physical conditions of the photosphere. The polar and equatorial temperatures, superficial gravities and aspect angle i were inferred from the fitting of stellar models distorted by fast rotation (Lovekin et al 2006;von Zeipel 1924a,b). The bolometric luminosity (log L/L ), stellar mass (M/M ), and logarithmic age (log τ) were derived from interpolations in the tabulated evolutionary tracks of non-rotating stars by Schaller et al (1992).…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic variabilities inλPavonis

Levenhagen

Leister

Künzel

2011

A&A

View full text Add to dashboard Cite

Aims. We investigate the time-varying patterns in line profiles, V/R, and radial velocity of the Be star HD 173948 (λ Pavonis). Methods. Time series analyses of radial velocity, V/R, and line profiles of He i, Fe ii, and Si ii were performed with the Cleanest algorithm. An estimate of the stellar rotation frequency was derived from the stellar mass and radius in the Roche limit by adopting an aspect angle i derived from the fittings of non-LTE model spectra affected by rotation. The projected rotation velocity, necessary as input for the spectral synthesis procedure, was evaluated from the Fourier transform of the rotation profiles of all neutral helium lines in the optical range. Results. Emission episodes in Balmer and He i lines, as well as V/R cyclic variations, are reported for spectra observed in year 1999, followed by a relatively quiescent phase (2000) and then again a new active epoch (2001). From time series analyses of line profiles, radial velocities, and V/R ratios, four signals with high confidence levels are detected: ν 1 = 0.17 ± 0.02, ν 2 = 0.49 ± 0.05, ν 3 = 0.82 ± 0.03, and ν 4 = 1.63 ± 0.04 c/d. We interpret ν 4 as a non-radial pulsation g-mode, ν 3 as a signal related to the orbital timescale of ejected material, which is near the theoretical rotation frequency 0.81 c/d inferred from the fitting of the models taken into account for gravity darkening. The signals ν 1 and ν 2 are viewed as aliases of ν 3 and ν 4 .

show abstract

Surface Temperature and Synthetic Spectral Energy Distributions for Rotationally Deformed Stars

Cited by 37 publications

References 36 publications

Critical study of the distribution of rotational velocities of Be stars

Critical study of the distribution of rotational velocities of Be stars

Differential rotation in rapidly rotating early-type stars

Spectroscopic variabilities inλPavonis

Contact Info

Product

Resources

About