J/A+A/530/A120 Mid-infrared diameter of W Hya (Zhao-Geisler+, 2011)
The mid-infrared diameter of W Hydrae.
Zhao-Geisler R., Quirrenbach A., Koehler R., Lopez B., Leinert C.
<Astron. Astrophys. 530, A120 (2011)>
=2011A&A...530A.120Z 2011A&A...530A.120Z
ADC_Keywords: Stars, variable ; Stars, diameters ; Infrared sources
Keywords: stars: AGB and post-AGB - stars: individual: W Hya -
techniques: high angular resolution - circumstellar matter
techniques: interferometric - infrared: stars
Abstract:
Mid-infrared (N-band) interferometric data of W Hya were obtained with
MIDI/VLTI between April 2007 and September 2009, covering nearly three
pulsation cycles. The spectrally dispersed visibility data of all 75
observations were analyzed by fitting a circular fully limb-darkened
disk (FDD) model to all data and individual pulsation phases.
Asymmetries were studied with an elliptical FDD.
Modeling results in an apparent angular FDD diameter of W Hya of about
(80±1.2)mas (7.8AU) between 8 and 10 micron, which corresponds to an
about 1.9 times larger diameter than the photospheric one. The
diameter gradually increases up to (105±1.2)mas (10.3AU) at
12 micron. In contrast, the FDD relative flux fraction decreases from
(0.85±0.02) to (0.77±0.02), reflecting the increased flux
contribution from a fully resolved surrounding silicate dust shell.
The asymmetric character of the extended structure could be confirmed.
An elliptical FDD yields a position angle of (11±20)deg and an axis
ratio of (0.87±0.07). A weak pulsation dependency is revealed with a
diameter increase of (5.4±1.8)mas between visual minimum and
maximum, while detected cycle-to-cycle variations are smaller.
Description:
The file contains the calibrated visibilities of all 75 used
observations listed in the observation log (table1) as function of
wavelength (8-12micron). Data are ordered by time (same as in table1).
Objects:
---------------------------------------------
RA (2000) DE Designation(s)
---------------------------------------------
13 49 02.0 -28 22 03 W Hydrae = V* W Hya
---------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 46 83 Observation log
data.dat 1133 71 Calibrated visibilities of W Hya
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 "YYYY-DD-MM" Date Observation date
12- 13 A2 --- AT AT station (1)
15- 19 A5 --- Disp Dispersive element (grism or prism)
22- 26 F5.2 m B Projected baseline length
28- 33 F6.2 deg PA [-13/131] Position angle of the projected
baseline on the sky
35- 38 F4.2 --- Phase Phase
40- 43 A4 --- QF Quality flag (2)
45- 46 I2 --- Seq ? Sequential number for visibility used in
data.dat file
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Note (1): AT stations as follows:
A = E0-G0
B = G0-H0
B* = A0-D0
C = E0-H0
D = D0-H0
E = D0-G1
F = H0-G1
Note (2): Quality flag showing if that observation is used for the model
fitting (used) or not (n.u.), see Sect. 3.1 for reasons that a value
had not been used.
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Byte-by-byte Description of file: data.dat
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Bytes Format Units Label Explanations
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1- 10 F10.7 um lambda Wavelength
12- 25 F14.10 --- V1 Calibrated visibility # 1 (2007-04-12)
27- 40 F14.10 --- V2 Calibrated visibility # 2 (2007-04-13)
42- 55 F14.10 --- V3 Calibrated visibility # 3 (2007-04-17)
57- 70 F14.10 --- V4 Calibrated visibility # 4 (2007-04-22)
72- 85 F14.10 --- V5 Calibrated visibility # 5 (2007-04-22)
87- 100 F14.10 --- V6 Calibrated visibility # 6 (2007-04-22)
102- 115 F14.10 --- V7 Calibrated visibility # 7 (2007-04-22)
117- 130 F14.10 --- V8 Calibrated visibility # 8 (2007-04-25)
132- 145 F14.10 --- V9 Calibrated visibility # 9 (2007-06-18)
147- 160 F14.10 --- V10 Calibrated visibility # 10 (2007-06-20)
162- 175 F14.10 --- V11 Calibrated visibility # 11 (2007-06-20)
177- 190 F14.10 --- V12 Calibrated visibility # 12 (2007-07-02)
192- 205 F14.10 --- V13 Calibrated visibility # 13 (2007-07-04)
207- 220 F14.10 --- V14 Calibrated visibility # 14 (2007-07-04)
222- 235 F14.10 --- V15 Calibrated visibility # 15 (2008-01-10)
237- 250 F14.10 --- V16 Calibrated visibility # 16 (2008-02-20)
252- 265 F14.10 --- V17 Calibrated visibility # 17 (2008-02-20)
267- 280 F14.10 --- V18 Calibrated visibility # 18 (2008-02-22)
282- 295 F14.10 --- V19 Calibrated visibility # 19 (2008-02-22)
297- 310 F14.10 --- V20 Calibrated visibility # 20 (2008-03-02)
312- 325 F14.10 --- V21 Calibrated visibility # 21 (2008-03-02)
327- 340 F14.10 --- V22 Calibrated visibility # 22 (2008-03-03)
342- 355 F14.10 --- V23 Calibrated visibility # 23 (2008-03-06)
357- 370 F14.10 --- V24 Calibrated visibility # 24 (2008-03-11)
372- 385 F14.10 --- V25 Calibrated visibility # 25 (2008-03-11)
387- 400 F14.10 --- V26 Calibrated visibility # 26 (2008-03-12)
402- 415 F14.10 --- V27 Calibrated visibility # 27 (2008-03-13)
417- 430 F14.10 --- V28 Calibrated visibility # 28 (2008-03-13)
432- 445 F14.10 --- V29 Calibrated visibility # 29 (2008-03-13)
447- 460 F14.10 --- V30 Calibrated visibility # 30 (2008-03-14)
462- 475 F14.10 --- V31 Calibrated visibility # 31 (2008-03-14)
477- 490 F14.10 --- V32 Calibrated visibility # 32 (2008-03-25)
492- 505 F14.10 --- V33 Calibrated visibility # 33 (2008-03-25)
507- 520 F14.10 --- V34 Calibrated visibility # 34 (2008-03-25)
522- 535 F14.10 --- V35 Calibrated visibility # 35 (2008-04-01)
537- 550 F14.10 --- V36 Calibrated visibility # 36 (2008-04-02)
552- 565 F14.10 --- V37 Calibrated visibility # 37 (2008-04-02)
567- 580 F14.10 --- V38 Calibrated visibility # 38 (2008-04-03)
582- 595 F14.10 --- V39 Calibrated visibility # 39 (2008-04-28)
597- 610 F14.10 --- V40 Calibrated visibility # 40 (2008-04-28)
612- 625 F14.10 --- V41 Calibrated visibility # 41 (2008-05-25)
627- 640 F14.10 --- V42 Calibrated visibility # 42 (2008-05-30)
642- 655 F14.10 --- V43 Calibrated visibility # 43 (2008-07-03)
657- 670 F14.10 --- V44 Calibrated visibility # 44 (2008-07-03)
672- 685 F14.10 --- V45 Calibrated visibility # 45 (2008-07-06)
687- 700 F14.10 --- V46 Calibrated visibility # 46 (2009-01-16)
702- 715 F14.10 --- V47 Calibrated visibility # 47 (2009-01-16)
717- 730 F14.10 --- V48 Calibrated visibility # 48 (2009-01-20)
732- 745 F14.10 --- V49 Calibrated visibility # 49 (2009-01-21)
747- 760 F14.10 --- V50 Calibrated visibility # 50 (2009-01-21)
762- 775 F14.10 --- V51 Calibrated visibility # 51 (2009-01-22)
777- 790 F14.10 --- V52 Calibrated visibility # 52 (2009-01-22)
792- 805 F14.10 --- V53 Calibrated visibility # 53 (2009-01-22)
807- 820 F14.10 --- V54 Calibrated visibility # 54 (2009-01-22)
822- 835 F14.10 --- V55 Calibrated visibility # 55 (2009-01-25)
837- 850 F14.10 --- V56 Calibrated visibility # 56 (2009-01-25)
852- 865 F14.10 --- V57 Calibrated visibility # 57 (2009-01-25)
867- 880 F14.10 --- V58 Calibrated visibility # 58 (2009-01-25)
882- 895 F14.10 --- V59 Calibrated visibility # 59 (2009-01-27)
897- 910 F14.10 --- V60 Calibrated visibility # 60 (2009-01-27)
912- 925 F14.10 --- V61 Calibrated visibility # 61 (2009-02-16)
927- 940 F14.10 --- V62 Calibrated visibility # 62 (2009-02-16)
942- 955 F14.10 --- V63 Calibrated visibility # 63 (2009-03-16)
957- 970 F14.10 --- V64 Calibrated visibility # 64 (2009-04-20)
972- 985 F14.10 --- V65 Calibrated visibility # 65 (2009-04-23)
987- 1000 F14.10 --- V66 Calibrated visibility # 66 (2009-04-23)
1002- 1015 F14.10 --- V67 Calibrated visibility # 67 (2009-04-24)
1017- 1030 F14.10 --- V68 Calibrated visibility # 68 (2009-05-02)
1032- 1045 F14.10 --- V69 Calibrated visibility # 69 (2009-05-03)
1047- 1060 F14.10 --- V70 Calibrated visibility # 70 (2009-05-03)
1062- 1075 F14.10 --- V71 Calibrated visibility # 71 (2009-05-03)
1077- 1090 F14.10 --- V72 Calibrated visibility # 72 (2009-06-04)
1092- 1105 F14.10 --- V73 Calibrated visibility # 73 (2009-06-04)
1107- 1120 F14.10 --- V74 Calibrated visibility # 74 (2009-06-04)
1122- 1133 F12.8 --- V75 Calibrated visibility # 75 (2009-08-15)
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Acknowledgements:
Ronny Zhao-Geisler, rgeisler(at)lsw.uni-heidelberg.de
(End) Patricia Vannier [CDS] 19-Apr-2011