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| DOI | 10.1088/0004-637X/732/2/68 | ||||
| Año | 2011 | ||||
| Tipo | artículo de investigación |
Citas Totales
Autores Afiliación Chile
Instituciones Chile
% Participación
Internacional
Autores
Afiliación Extranjera
Instituciones
Extranjeras
Near-infrared interferometers have recently imaged a number of rapidly rotating A-type stars, finding levels of gravity darkening inconsistent with theoretical expectations. Here, we present new imaging of both a cooler star beta Cas (F2IV) and a hotter one alpha Leo (B7V) using the CHARA array and the MIRC instrument at the H band. Adopting a solid-body rotation model with a simple gravity darkening prescription, we modeled the stellar geometric properties and surface temperature distributions, confirming that both stars are rapidly rotating and show gravity darkening anomalies. We estimate the masses and ages of these rapid rotators on L-R-pol and H-R diagrams constructed for non-rotating stars by tracking their non-rotating equivalents. The unexpected fast rotation of the evolved sub-giant beta Cas offers a unique test of the stellar core-envelope coupling, revealing quite efficient coupling over the past similar to 0.5 Gyr. Lastly, we summarize all our interferometric determinations of the gravity darkening coefficient for rapid rotators, finding that none match the expectations from the widely used von Zeipel gravity darkening laws. Since the conditions of the von Zeipel law are known to be violated for rapidly rotating stars, we recommend using the empirically derived beta = 0.19 for such stars with radiation-dominated envelopes. Furthermore, we note that no paradigm exists for self-consistently modeling heavily gravity-darkened stars that show hot radiative poles with cool convective equators.
| Ord. | Autor | Género | Institución - País |
|---|---|---|---|
| 1 | Che, X. | - |
UNIV MICHIGAN - Estados Unidos
University of Michigan, Ann Arbor - Estados Unidos |
| 2 | Monnier, John D. | Hombre |
UNIV MICHIGAN - Estados Unidos
University of Michigan, Ann Arbor - Estados Unidos |
| 3 | Zhao, M. | - |
Jet Prop Lab - Estados Unidos
Jet Propulsion Laboratory - Estados Unidos |
| 4 | Pedretti, E. | Hombre |
Univ St Andrews - Reino Unido
University of St Andrews - Reino Unido |
| 5 | Thureau, Nathalie | Mujer |
Univ St Andrews - Reino Unido
University of St Andrews - Reino Unido |
| 6 | Merand, Antoine | Hombre |
Georgia State Univ - Estados Unidos
ESO - Chile Georgia State University - Estados Unidos European Southern Observatory Santiago - Chile |
| 7 | ten Brummelaar, Theo | Hombre |
Georgia State Univ - Estados Unidos
Georgia State University - Estados Unidos |
| 8 | Mc Alister, Harold A. | Hombre |
Georgia State Univ - Estados Unidos
Georgia State University - Estados Unidos |
| 9 | Ridgway, Stephen T. | Hombre |
Natl Opt Astron Observ - Estados Unidos
National Optical Astronomy Observatory - Estados Unidos |
| 10 | Turner, Neal | Hombre |
Georgia State Univ - Estados Unidos
Georgia State University - Estados Unidos |
| 11 | Sturmann, Judit | Mujer |
Georgia State Univ - Estados Unidos
Georgia State University - Estados Unidos |
| 12 | Sturmann, Laszlo | - |
Georgia State Univ - Estados Unidos
Georgia State University - Estados Unidos |
| Fuente |
|---|
| National Science Foundation |
| University of Michigan |
| Georgia State University |
| Directorate for Mathematical and Physical Sciences |
| Division Of Astronomical Sciences; Direct For Mathematical & Physical Scien |
| Agradecimiento |
|---|
| We acknowledge interesting discussions with Antonio Claret, Jason Aufdenberg, Chuck Cowley, and Chris Matzner when preparing this manuscript. The CHARA Array is funded by the National Science Foundation through NSF grants AST-0307562, AST-0606958, AST-0908253 and by the Georgia State University. Funding for the MIRC combiner came from the University of Michigan and observations were supported through National Science Foundation grants AST-0352723, AST-0707927, and AST-0807577. |