Interferometric observations of rapidly rotating stars

Belle, Gerald van

doi:10.1007/s00159-012-0051-2

Cited by 85 publications

(30 citation statements)

References 142 publications

(219 reference statements)

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…As listed in Table 1, published ages vary between 1.25 and 1.50 Gyr. The calibration within the PARSEC isochrones (Bressan et al 2012) for solar metallicity ([Z] = 0.019 dex) yields an almost perfect match with the evolutionary track of log t = 9.1 (1.26 Gyr), which implies that 95 Vir is still on the main sequence and therefore an object of luminosity class V. This finding is in line with the result by Zorec & Royer (2012), who published a fractional age of 0.881(16).…”

Section: Target Star Literature Information and Astrophysical Paramesupporting

confidence: 87%

K2 observations of 95 Vir: δ Scuti pulsations in a chromospherically active star

Paunzen

Hümmerich

Bernhard

et al. 2017

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

We have searched for photometric variability in 95 Vir, a fast rotating, chromospherically active early F-type star, which was observed in the framework of Campaign 6 of the Kepler K2 mission. Available literature information on 95 Vir were procured, and well-established calibrations were employed to verify the derived astrophysical parameters. We have investigated the location of our target star in the M Bol versus log T eff diagram, which provides information on evolutionary status. We have discussed our results in detail, drawing on literature information and the theoretical predictions of state-of-the-art pulsation models, with the aim of unraveling the underlying variability mechanisms. From an analysis of 3400 long-cadence measurements, we have identified two main frequencies and several harmonics in our target star. We attribute the main frequency, f 1 = 9.53728 d −1 , to δ Scuti pulsations. The origin of the secondary signal, f 2 = 1.07129 d −1 , is less clear. We have investigated three possible interpretations of the low-frequency variation: binarity, pulsation and rotational modulation. Current evidence favours an interpretation of f 2 as a signature of the rotational period caused by the presence of cool star spots, which goes along well with the observed chromospheric activity. However, phase-resolved spectroscopy is needed to verify this assumption. We briefly consider other chromospherically active δ Scuti stars that have been presented in the literature. A search for star spot-induced photometric variability in these objects might be of great interest, as well as an investigation of the interplay between chromospheric and pulsational activity.

show abstract

Section: Target Star Literature Information and Astrophysical Paramesupporting

confidence: 87%

K2 observations of 95 Vir: δ Scuti pulsations in a chromospherically active star

Paunzen

Hümmerich

Bernhard

et al. 2017

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

show abstract

“…Stellar rotation was measured for the first time by interferometry, from the photocentre displacements by Lagarde (1994), on the slow rotator Aldebaran, which was observed in 1988 at OHP (Observatoire de Haute-Provence) through the 152cm telescope by the Speckle Differential Interferometry method. Results obtained by interferometry on the fast rotators were summarized by Jankov (2011) & van Belle (2012. The extreme stellar flattening induced by the rotation was measured by interferometry by Domiciano de Souza et al (2003) on Achernar (Req/R pol = 1.56 ± 0.05), using VLTI/VINCI (Very Large Telescope Interferometer/VLT INterferometer Commissioning Instrument) with a dense (u, v) coverage.…”

Section: Optical Interferometry Of Rapid Rotatorsmentioning

confidence: 99%

Differential interferometry of the rapid rotator Regulus

Hadjara

Petrov

Jankov

et al. 2018

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

We analyse interferometric data obtained for Regulus with AMBER (Astronomical Multi-BEam combineR) at high spectral resolution (λ/δλ ≈ 12000) across the Brγ spectral line. The study of the photocentre displacement allows us to constrain a large number of stellar parameters -equatorial radius R eq , equatorial velocity V eq , inclination i, rotation-axis position angle P A rot , and flattening -with an estimation of gravity-darkening coefficient β using previously published theoretical results. We use the Simulation Code of Interferometric-observations for ROtators and CirCumstellar Objects (SCIROCCO), a semi-analytical algorithm dedicated to fast rotators. We chose Regulus because it is a very well-known edge-on star, for which an alternative approach is needed to check the previously published results. Our analysis showed that a significant degeneracy of solution is present. By confronting the results obtained by differential interferometry with those obtained by conventional long-base interferometry, we obtain similar results (within the uncertainties), thereby validating our approach, where V eq and i are found separately. From the photocentre displacement, we can independently deduce P A rot . We use two minimization methods to restrict observed stellar parameters via a fast rotator model: a non-stochastic method (χ 2 fit) and a stochastic one (Markov Chain Monte Carlo method), in order to check whether the correct global minimum is achieved particularly with respect to the degeneracies of the gravity darkening parameter β, where we demonstrate, using a quantitative analysis of parameters, that the estimate of β is easier for stars with an inclination angle of around 45 • .

show abstract

“…Population I stars with spectral type A have masses that range from 1.5 to 2.5 M ,  based on dynamical measurements of spectroscopic binaries (e.g., Torres et al 2010), and corresponding main sequence lifetimes of 3.6-1.0 Gyr (assuming MS t µ M , 2.5 - Kippenhahn et al 2012). However, measuring the age and mass of any single A-type star is often severely complicated by their peculiar characteristics, including chemically anomalous photospheres (e.g., Am stars, Ap stars, λ Boo stars), radial and non-radial pulsations (e.g., γ Doradus-type, δ Scuti-type), and severely distorted shapes from rapid rotation (e.g., Regulus-McAlister et al 2005, Altair-Monnier et al 2007, Vega- Aufdenberg et al 2006;Monnier et al 2012).…”

Section: Introductionmentioning

confidence: 99%

The Ages of a-Stars. I. Interferometric Observations and Age Estimates for Stars in the Ursa Major Moving Group

Jones

White

Boyajian

et al. 2015

ApJ

View full text Add to dashboard Cite

We have observed and spatially resolved a set of seven A-type stars in the nearby Ursa Major moving group with the Classic, CLIMB, and PAVO beam combiners on the Center for High Angular Resolution Astronomy Array. At least four of these stars have large rotational velocities (v i sin  170 km s 1 -) and are expected to be oblate. These interferometric measurements, the stars' observed photometric energy distributions, and v i sin values are used to computationally construct model oblate stars from which stellar properties (inclination, rotational velocity, and the radius and effective temperature as a function of latitude, etc.) are determined. The results are compared with MESA stellar evolution models to determine masses and ages. The value of this new technique is that it enables the estimation of the fundamental properties of rapidly rotating stars without the need to fully image the star. It can thus be applied to stars with sizes comparable to the interferometric resolution limit as opposed to those that are several times larger than the limit. Under the assumption of coevality, the spread in ages can be used as a test of both the prescription presented here and the MESA evolutionary code for rapidly rotating stars. With our validated technique, we combine these age estimates and determine the age of the moving group to be 414 ± 23 Myr, which is consistent with, but much more precise than previous estimates.

show abstract

Interferometric observations of rapidly rotating stars

Cited by 85 publications

References 142 publications

K2 observations of 95 Vir: δ Scuti pulsations in a chromospherically active star

K2 observations of 95 Vir: δ Scuti pulsations in a chromospherically active star

Differential interferometry of the rapid rotator Regulus

The Ages of a-Stars. I. Interferometric Observations and Age Estimates for Stars in the Ursa Major Moving Group

Contact Info

Product

Resources

About