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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
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:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 46 83 Observation log data.dat 1133 71 Calibrated visibilities of W Hya
Byte-by-byte Description of file: table1.dat
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
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.
Byte-by-byte Description of file: data.dat
Bytes Format Units Label Explanations
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)
Acknowledgements: Ronny Zhao-Geisler, rgeisler(at)lsw.uni-heidelberg.de
(End) Patricia Vannier [CDS] 19-Apr-2011
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