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2018A&A...618A.125G - Astronomy and Astrophysics, volume 618A, 125-125 (2018/1-0)

GRAVITY chromatic imaging of η Car's core. Milliarcsecond resolution imaging of the wind-wind collision zone (Brγ, He I).

GRAVITY COLLABORATION, SANCHEZ-BERMUDEZ J., WEIGELT G., BESTENLEHNER J.M., KERVELLA P., BRANDNER W., HENNING T., MULLER A., PERRIN G., POTT J.-U., SCHOLLER M., VAN BOEKEL R., ABUTER R., ACCARDO M., AMORIM A., ANUGU N., AVILA G., BENISTY M., BERGER J.P., BLIND N., BONNET H., BOURGET P., BRAST R., BURON A., CANTALLOUBE F., CARATTI O GARATTI A., CASSAING F., CHAPRON F., CHOQUET E., CLENET Y., COLLIN C., COUDE DU FORESTO V., DE WIT W., DE ZEEUW T., DEEN C., DELPLANCKE-STROBELE F., DEMBET R., DERIE F., DEXTER J., DUVERT G., EBERT M., ECKART A., EISENHAUER F., ESSELBORN M., FEDOU P., GARCIA P.J.V., GARCIA DABO C.E., GARCIA LOPEZ R., GAO F., GENDRON E., GENZEL R., GILLESSEN S., HAUBOIS X., HAUG M., HAUSSMANN F., HIPPLER S., HORROBIN M., HUBER A., HUBERT Z., HUBIN N., HUMMEL C.A., JAKOB G., JOCHUM L., JOCOU L., KARL M., KAUFER A., KELLNER S., KENDREW S., KERN L., KIEKEBUSCH M., KLEIN R., KOLB J., KULAS M., LACOUR S., LAPEYRERE V., LAZAREFF B., LE BOUQUIN J.-B., LENA P., LENZEN R., LEVEQUE S., LIPPA M., MAGNARD Y., MEHRGAN L., MELLEIN M., MERAND A., MORENO-VENTAS J., MOULIN T., MULLER E., MULLER F., NEUMANN U., OBERTI S., OTT T., PALLANCA L., PANDURO J., PASQUINI L., PAUMARD T., PERCHERON I., PERRAUT K., PETRUCCI P.-O., PFLUGER A., PFUHL O., DUC T.P., PLEWA P.M., POPOVIC D., RABIEN S., RAMIREZ A., RAMOS J., RAU C., RIQUELME M., RODRIGUEZ-COIRA G., ROHLOFF R.-R., ROSALES A., ROUSSET G., SCHEITHAUER S., SCHUHLER N., SPYROMILIO J., STRAUB O., STRAUBMEIER C., STURM E., SUAREZ M., TRISTRAM K.R.W., VENTURA N., VINCENT F., WAISBERG I., WANK I., WIDMANN F., WIEPRECHT E., WIEST M., WIEZORREK E., WITTKOWSKI M., WOILLEZ J., WOLFF B., YAZICI S., ZIEGLER D. and ZINS G.

Abstract (from CDS):

Context. η Car is one of the most intriguing luminous blue variables in the Galaxy. Observations and models of the X-ray, ultraviolet, optical, and infrared emission suggest a central binary in a highly eccentric orbit with a 5.54yr period residing in its core. 2D and 3D radiative transfer and hydrodynamic simulations predict a primary with a dense and slow stellar wind that interacts with the faster and lower density wind of the secondary. The wind-wind collision scenario suggests that the secondary's wind penetrates the primary's wind creating a low-density cavity in it, with dense walls where the two winds interact. However, the morphology of the cavity and its physical properties are not yet fully constrained.
Aims. We aim to trace the inner ∼5-50au structure of η Car's wind-wind interaction, as seen through Brγ and, for the first time, through the HeI 2s-2p line.
Methods. We have used spectro-interferometric observations with the K-band beam-combiner GRAVITY at the VLTI. The analyses of the data include (i) parametrical model-fitting to the interferometric observables, (ii) a CMFGEN model of the source's spectrum, and (iii) interferometric image reconstruction.
Results. Our geometrical modeling of the continuum data allows us to estimate its FWHM angular size close to 2mas and an elongation ratio ε=1.06±0.05 over a PA=130°±20°. Our CMFGEN modeling of the spectrum helped us to confirm that the role of the secondary should be taken into account to properly reproduce the observed Brγ and HeI lines. Chromatic images across the Brγ line reveal a southeast arc-like feature, possibly associated to the hot post-shocked winds flowing along the cavity wall. The images of the HeI 2s-2p line served to constrain the 20mas (∼50au) structure of the line-emitting region. The observed morphology of HeI suggests that the secondary is responsible for the ionized material that produces the line profile. Both the Brγ and the HeI 2s-2p maps are consistent with previous hydrodynamical models of the colliding wind scenario. Future dedicated simulations together with an extensive interferometric campaign are necessary to refine our constraints on the wind and stellar parameters of the binary, which finally will help us predict the evolutionary path of η Car.

Abstract Copyright: © ESO 2018

Journal keyword(s): instrumentation: interferometers - instrumentation: high angular resolution - stars: mass-loss - stars: massive - stars: imaging - binaries: general

Simbad objects: 4

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2021.02.24-19:34:26

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