J/A+A/628/A132 IK Tau and HIP 20188 visible polarimetric imaging (Adam+, 2019)
Exploring the innermost region of the oxygen-rich AGB star IK Tauri with
VLT/SPHERE-ZIMPOL and VLTI/AMBER.
Adam C., Ohnaka K.
<Astron. Astrophys. 628, A132 (2019)>
=2019A&A...628A.132A 2019A&A...628A.132A (SIMBAD/NED BibCode)
ADC_Keywords: Stars, supergiant ; Stars, late-type ; Models, atmosphere ;
Mass loss ; Polarization ; Interferometry
Keywords: techniques: polarimetric - stars: AGB and post-AGB -
stars: atmospheres - circumstellar matter -
stars: individual: IK Tau -- stars: imaging
Abstract:
We present visible polarimetric imaging observations of the
oxygen-rich AGB star IK Tau obtained with SPHERE-ZIMPOL (phase 0.27)
as well as interferometric observations with AMBER. The polarimetric
imaging capabilities of SPHERE-ZIMPOL have allowed us to spatially
resolve clumpy dust clouds at 20-50mas from the central star, which
corresponds to 2-5R* when combined with a central star's angular
diameter of 20.7±1.53 mas measured with AMBER. The diffuse,
asymmetric dust emission extends out to ∼73R*. We find that the TiO
emission extends to 150 mas (15R*). The AMBER data in the CO lines
also suggest a molecular outer atmosphere extending to ∼1.5R*. The
results of our 2-D Monte Carlo radiative transfer modelling of dust
clumps suggest that the polarized intensity and degree of linear
polarization can be reasonably explained by small-sized (0.1µm)
grains of Al2O_3, MgSiO_3, or Mg2SiO_4 in an optically thin shell
(τ_550 nm=0.5±0.1) with an inner boundary radius of 3.5*. IK
Tau's mass-loss rate is 20 to 50 times higher than the previously
studied AGB stars W Hya, R Dor, and o Cet. Nevertheless, our
observations of IK Tau revealed that clumpy dust formation occurs
close to the star as seen in those low mass-rate AGB stars.
Description:
IK Tau and the PSF reference star HIP 20188 were observed with ZIMPOL
at three wavelengths in the pseudo-continuum (645, 748, and 820nm),
in the Hα line at 656.3nm, and in the TiO band at 717nm. The
AMBER observations of IK Tau were carried out in the wavelength region
of the CO first overtone lines near 2.3µm (R=12 000). This is the
data used to produce Figures 1, 3 and 6 in the paper.
Objects:
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RA (2000) DE Designation(s)
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03 53 28.9 +11 24 22 IK Tau = NML Tau
04 19 37.4 +10 07 17 HD 27386 = HIP 20188
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
visiktau.dat 173 506 Observed visibilities and closure phases for
IK Tau observed with VLT/AMBER
list.dat 241 25 List of FITS files
fits/* . 25 Individual fits images
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See also:
J/A+A/597/A25 : IK Tau millimeter IRAM-30m line survey (Velilla Prieto+, 2017)
J/A+A/624/A107 : IK Tau + IRC+10011 interferometric obs. (Verbena+, 2019)
Byte-by-byte Description of file: visiktau.dat
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Bytes Format Units Label Explanations
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1- 8 F8.6 um lambda Wavelength
11- 19 E9.3 --- F1 Flux measured at baseline 1 (1)
22- 30 E9.3 --- Vis1 Visibility at baseline 1
33- 41 E9.3 --- e_Vis1 Visibility uncertainty at baseline 1
43- 52 E10.3 deg DP1 Differential phase at baseline 1
55- 63 E9.3 deg e_DP1 Differential phase uncertainty at baseline 1
66- 74 E9.3 --- Vis2 Visibility at baseline 2
77- 85 E9.3 --- e_Vis2 Visibility uncertainty at baseline 2
87- 96 E10.3 deg DP2 Differential phase at baseline 2
99-107 E9.3 deg e_DP2 Differential phase uncertainty at baseline 2
110-118 E9.3 --- Vis3 Visibility at baseline 3
121-129 E9.3 --- e_Vis3 Visibility uncertainty at baseline 3
131-140 E10.3 deg DP3 Differential phase at baseline 3
143-151 E9.3 deg e_DP3 Differential phase uncertainty at baseline 3
153-162 E10.3 deg CP Closure phase
165-173 E9.3 deg e_CP Closure phase uncertainty
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Note (1): The flux (= spectrum) is normalized by the continuum and was used to
produce Fig. 6a of the paper.
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Byte-by-byte Description of file:list.dat*
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Bytes Format Units Label Explanations
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1- 2 I2 h RAh Right ascension (J2000)
4- 5 I2 min RAm Right ascension (J2000)
7- 10 F4.1 s RAs Right ascension (J2000)
11 A1 --- DE- Declination sign (J2000)
12- 13 I2 deg DEd Declination sign (J2000)
15- 16 I2 arcmin DEm Declination sign (J2000)
18- 19 I2 arcsec DEs Declination sign (J2000)
21- 29 E9.6 arcsec/pix scale Scale of the image
31- 34 I4 --- Nx Number of pixels along X-axis
36- 39 I4 --- Ny Number of pixels along Y-axis
41- 45 F5.3 um lambda [0.645/0.820] ZIMPOL filter (wavelength)
47- 52 A6 --- Filter Name of ZIMPOL filter
54- 55 I2 s DIT [2/80] Detector integration time
57- 60 A4 --- ObsMode Observation mode (1)
62- 65 I4 Kibyte size Size of FITS file
67-142 A76 --- FileName Name of FITS file, in subdirectory fits
144-241 A98 --- Title Title of the file
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Note (1): Observation mode as follows:
sPol = slow Polarimetry
fPol = fast Polarimetry
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Acknowledgements:
Christian Adam christian.adam84 (at) gmail.com
(End) Christian Adam [UCN, Chile], Patricia Vannier [CDS] 23-Aug-2019