J/A+A/481/553 High-precision angular diameter of V3879 Sgr (Le Bouquin+, 2008)
First result with AMBER+FINITO on the VLTI:
the high-precision angular diameter of V3879 Sagittarii.
Le Bouquin J.-B., Bauvir B., Haguenauer P., Scholler M., Rantakyro F.,
Menardi S.
<Astron. Astrophys. 481, 553 (2008)>
=2008A&A...481..553L 2008A&A...481..553L
ADC_Keywords: Interferometry
Keywords: instrumentation: interferometers - techniques: interferometric -
stars: fundamental parameters
Abstract:
Our goal is to demonstrate the potential of the interferometric AMBER
instrument linked with the Very Large Telescope Interferometer (VLTI)
fringe-tracking facility FINITO to derive high-precision stellar
diameters.
We use commissioning data obtained on the bright single star
V3879 Sgr. Locking the interferometric fringes with FINITO allows us
to record very low contrast fringes on the AMBER camera. By fitting
the amplitude of these fringes, we measure the diameter of the target
in three directions simultaneously with an accuracy of
25micro-arcseconds.
We showed that V3879 Sgr has a round photosphere down to a sub-percent
level. We quickly reached this level of accuracy because the technique
used is independent from absolute calibration (at least for baselines
that fully span the visibility null). We briefly discuss the potential
biases found at this level of precision.
Description:
We obtained data at the VLBI during the night of 2007 May 1, with the
relocatable 1.8m Auxiliary Telescopes AT2, AT3 and AT4 placed
respectively at stations G1, D0 and H0. Ground baseline length is 64m
for baseline D0-H0 and 71m for baselines G1-D0 and G1-H0.
Objects:
----------------------------------------------------------
RA (2000) DE Designation(s)
----------------------------------------------------------
18 42 55.1 -19 17 03 V3879 Sgr = HD 172816
----------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
vis2.dat 67 23274 Calibrated square visibility for 54 baselines
--------------------------------------------------------------------------------
Byte-by-byte Description of file: vis2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 F7.4 um lambda Wavelength
9- 20 F12.6 d MJD Modifiate Julian date of observation
22- 26 A5 --- Station Station of observation (1)
28- 37 F10.6 m u baseline projection toward East (u, in meter)
39- 48 F10.6 m v baseline projection toward Nord (v, in meter)
50- 59 F10.7 --- Vis2 [-1/1] Calibrated square visibility,
Vis2=<V2meas>-biais
60- 67 F8.6 --- e_Vis2 rms uncertainty on Vis2
--------------------------------------------------------------------------------
Note (1): Station of observation as follows:
D0-H0 = D0-H0 64m baseline
G1-D0 = G1-D0 71m baseline
H0-G1 = H0-G1 71m baseline
--------------------------------------------------------------------------------
Acknowledgements:
Jean-Baptiste Le Bouquin, jlebouqu(at)eso.org
(End) Patricia Vannier [CDS] 07-Dec-2007