An investigation of the close environment of beta Cep with the VEGA/CHARA interferometer
N. Nardetto, D. Mourard, I. Tallon-Bosc, M. Tallon, P. Berio, E. Chapellier, D. Bonneau, O. Chesneau, P. Mathias, K. Perraut, P. Stee, A. Blazit, J. M. Clausse,… 展开作者
N. Nardetto, D. Mourard, I. Tallon-Bosc, M. Tallon, P. Berio, E. Chapellier, D. Bonneau, O. Chesneau, P. Mathias, K. Perraut, P. Stee, A. Blazit, J. M. Clausse, O. Delaa, A. Marcotto, F. Millour, A. Roussel, A. Spang, H. McAlister, T. ten Brummelaar, J. Sturmann, L. Sturmann, N. Turner, C. Farrington, P. J. Goldfinger
High-precision interferometric measurements of pulsating stars help to characterize their close environment. In 1974, a close companion was discovered around the pulsating star beta Cep using the speckle interferometry technique and features at the limit of resolution (20 milli-arcsecond or mas) of the instrument were mentioned that may be due to circumstellar material. Beta Cep has a magnetic field that might be responsible for a spherical shell or ring-like structure around the star as described by the MHD models. Using the visible recombiner VEGA installed on the CHARA long-baseline interferometer at Mt. Wilson, we aim to determine the angular diameter of beta Cep and resolve its close environment with a spatial resolution up to 1 mas level. Medium spectral resolution (R=6000) observations of beta Cep were secured with the VEGA instrument over the years 2008 and 2009. These observations were performed with the S1S2 (30m) and W1W2 (100m) baselines of the array. We investigated several models to reproduce our observations. A large-scale structure of a few mas is clearly detected around the star with a typical flux relative contribution of 0.23 +- 0.02. Our best model is a co-rotational geometrical thin ring around the star as predicted by magnetically-confined wind shock models. The ring inner diameter is 8.2 +- 0.8 mas and the width is 0.6 +- 0.7 mas. The orientation of the rotation axis on the plane of the sky is PA = 60 +- 1 deg, while the best fit of the mean angular diameter of beta Cep gives UD[V] = 0.22 +- 0.05 mas. Our data are compatible with the predicted position of the close companion of beta Cep. These results bring additional constraints on the fundamental parameters and on the future MHD and asteroseismological models of the star.
VEGA/CHARA interferometric observations of Cepheids. I. A resolved structure around the prototype classical Cepheid delta Cep in the visible spectral range
The surface brightness - color relationship (SBCR) is a poweful tool for determining the angular diameter of stars from photometry. It was for instance used to derive the distance of eclipsing binaries in the Large Magellanic Cloud (LMC), which led to its distance determination with an accuracy of 1%. We calibrate the SBCR for red giant stars in the 2.1 < V-K < 2.5 color range using homogeneous VEGA/CHARA interferometric data secured in the visible domain, and compare it to the relation based on infrared interferometric observations, which were used to derive the distance to the LMC. Observati…
Multi-chromatic observations of classical Cepheids using the CHARA Array interferometer: Surface brightness-colour relation, projection factor, and limb-darkening
Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange(蔚蓝海岸大学,蔚蓝海岸天文台);European Southern Observatory(欧洲南方天文台);LIRA, Observatoire de Paris, Université PSL, Sorbonne Université, Université Paris Cité, CY Cergy Paris Université, CNRS(巴黎天文台 LIRA 实验室,巴黎文理研究大学,索邦大学,巴黎西岱大学,CY 塞尔吉巴黎大学);French-Chilean Laboratory for Astronomy, IRL 3386, CNRS(中智天文学联合实验室);Instituto de Alta Investigación, Universidad de Tarapacá(塔拉帕卡大学高等研究院);Astronomy Department, University of Michigan(密歇根大学天文学系)
As many as 10\% of OB-type stars have global magnetic fields, which is surprising given their internal structure is radiative near the surface. A direct probe of internal structure is pulsations, and some OB-type stars exhibit pressure modes ($β$ Cep pulsators) or gravity modes (slowly pulsating B-type stars; SPBs); a few rare cases of hybrid $β$ Cep/SPBs occupy a narrow instability strip in the H-R diagram. The most precise fundamental properties of stars are obtained from eclipsing binaries (EBs), and those in clusters with known ages and metallicities provide the most stringent constraints …
Ensemble pulsational characteristics of eclipsing binaries containing $β$ Cep stars observed by the TESS mission
University of Nigeria, Nsukka(尼日利亚恩苏卡大学);KU Leuven(荷语鲁汶大学);Newcastle University(纽卡斯尔大学);Radboud University Nijmegen(奈梅亨拉德堡德大学);Max Planck Institut für Astronomie(马克斯·普朗克天文学研究所);Nicolaus Copernicus Astronomical Centre, Polish Academy of Sciences(波兰科学院尼古拉·哥白尼天文中心)
Mean angular diameters, distances and pulsation modes of the classical Cepheids FF Aql and T Vul - CHARA/FLUOR near-infrared interferometric observations
Multiplicity of Galactic Cepheids from long-baseline interferometry~III. Sub-percent limits on the relative brightness of a close companion of $δ$~Cephei
The presence of three more Herbig Ae/Be (HAeBe) stars in the Cepheus Flare within a 1.5$^{\circ}$ radius centered on HD 200775 suggests that star formation is prevalent in a wider region of the LDN 1147/1158, LDN 1172/1174, and LDN 1177 clouds. A number of young stellar objects (YSOs) are also found to be located toward these clouds. Various star formation studies indicate ongoing low-mass star formation inside this region. Sources associated with less near-infrared (IR) excess and less H-alpha emission raise the possibility that more low-mass YSOs, which were not identified in previous studie…