2006A&A...453.1059K


C.D.S. - SIMBAD4 rel 1.7 - 2021.02.24CET19:37:45

2006A&A...453.1059K - Astronomy and Astrophysics, volume 453, 1059-1066 (2006/7-3)

The polar wind of the fast rotating Be star Achernar. VINCI/VLTI interferometric observations of an elongated polar envelope.

KERVELLA P. and DOMICIANO DE SOUZA A.

Abstract (from CDS):

Be stars show evidence of mass loss and circumstellar envelopes (CSE) from UV resonance lines, near-IR excesses, and the presence of episodic hydrogen emission lines. The geometry of these envelopes is still uncertain, although it is often assumed that they are formed by a disk around the stellar equator and a hot polar wind. We probe the close environment of the fast rotating Be star Achernar at angular scales of a few milliarcseconds (mas) in the infrared, in order to constrain the geometry of a possible polar CSE. We obtained long-baseline interferometric observations of Achernar with the VINCI/VLTI beam combiner in the H and K bands, using various telescope configurations and baseline lengths with a wide azimuthal coverage. The observed visibility measurements along the polar direction are significantly lower than the visibility function of the photosphere of the star alone, in particular at low spatial frequencies. This points to the presence of an asymmetric diffuse CSE elongated along the polar direction of the star. To our data, we fit a simple model consisting of two components: a 2D elliptical Gaussian superimposed on a uniform ellipse representing the distorted photosphere of the fast rotating star. We clearly detected a CSE elongated along the polar axis of the star, as well as rotational flattening of the stellar photosphere. For the uniform-ellipse photosphere we derive a major axis of θeq=2.13 ±0.05mas and a minor axis of θpol=1.51 ±0.02mas. The relative near-IR flux measured for the CSE compared to the stellar photosphere is f=4.7±0.3%. Its angular dimensions are loosely constrained by the available data at ρeq=2.7±1.3mas and ρpol=17.6±4.9mas. This CSE could be linked to free-free emission from the radiative pressure driven wind originating from the hot polar caps of the star.

Abstract Copyright:

Journal keyword(s): techniques: high angular resolution - techniques: interferometric - stars: emission-line, Be - stars: mass-loss - stars: rotation - stars: individual: Achernar

Simbad objects: 16

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Number of rows : 16

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 HD 787 PM* 00 12 09.9850054049 -17 56 17.699314201   6.740 5.265     K4III 89 0
2 * gam Cas Be* 00 56 42.5317 +60 43 00.265 1.18 2.29 2.39 2.32 2.40 B0.5IVpe 1148 2
3 * del Phe PM* 01 31 15.1047497 -49 04 21.730837   4.918 3.935     G8.5IIIb 114 0
4 * alf Eri Be* 01 37 42.84548 -57 14 12.3101 -0.36 0.30 0.46 0.49 0.60 B6Vpe 447 0
5 * ups Cet PM* 02 00 00.3091617 -21 04 40.194571 7.45 5.58 4.02 2.76 1.72 M0III 95 0
6 * chi Phe PM* 02 01 42.3769730947 -44 42 48.626974441 8.45 6.63 5.14 3.92 3.03 K5IV 57 0
7 * alf Cet LP? 03 02 16.77307 +04 05 23.0596 6.10 4.17 2.53 1.18 0.02 M1.5IIIa 441 0
8 * 39 Eri PM* 04 14 23.6883920999 -10 15 22.617787948 7.18 6.07 4.90 4.01 3.44 K2III 103 0
9 HD 44951 PM* 06 24 10.3196410582 -11 31 48.324633091   6.434 5.207     K2III 62 0
10 * alf Leo PM* 10 08 22.31099 +11 58 01.9516 0.88 1.24 1.40 1.37 1.47 B8IVn 815 1
11 * eta Car Em* 10 45 03.5455050 -59 41 03.951060 6.37 7.034 6.21 4.90 4.41 OBepec 2253 0
12 * alf Ara Be* 17 31 50.4915282 -49 52 34.122041 2.09 2.78 2.95 3.05 3.29 B2Vne 248 0
13 * alf Aql dS* 19 50 46.99855 +08 52 05.9563 1.07 0.98 0.76 0.62 0.49 A7Vn 828 0
14 * alf Ind PM* 20 37 34.0320077 -47 17 29.402601 4.90 4.11 3.11     K0III-IV 124 0
15 * eps Ind PM* 22 03 21.6542294981 -56 47 09.537018193   5.75 4.69     K5V 486 0
16 * alf PsA ** 22 57 39.04625 -29 37 20.0533 1.31 1.25 1.16 1.11 1.09 A4V 1135 3

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2021.02.24-19:37:45

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