Title: Measurement of diameter and rotation of seismology primary targets with AMBER
1Measurement of diameter and rotationof
seismology primary targetswith AMBER
LUAN OCA
F.X Schmider, A. Domiciano, R. Petrov, S.
Jankov G. Berthomieu, P. Mathias, J. Provost, F.
Thevenin C. Catala
2What we want to measure through interferometry
- Fundamental parameters
- Diameter
- Oblateness
- Differential rotation
- Inclination angle
- Detection and characterisation of oscillation
modes - Single mode identification
- Intermediate degree modes
- High degree modes
3AMBER/VLTI Present Status
- AMBER
- characteristics
- 3 Telescopes instrument
- K, H and J bands
- Single mode
- Dispersed fringes
- Spectral resolutions 35, 1000, 10000
- Limiting magnitude with UTs K11
- specification absolute visibility accuracy
- goal visibility accuracy 0.1
- specification differential phase accuracy radians
- goal differential phase accuracy
- Commissioning in H and K medium resolution in
April 2004, high resolution in October 2004 - First open period second semester 2005, with
the UT - Fully operational (3 AT, BCD) second semester
2006? - Fringe tracking (FINITO) is not working
properly. Magnitude limit is 7 with AT - Relative precision are better than 0.5 for
individual measurements - Absolute visibilities are biased by calibration
uncertainties
4Differential visibilities and diameters(using
BCD Beam Commuter Device)
- 3 AT, 3 bases
- BCD
- low resolution (R35)
- JHK band
diameter is calculated as a parameter of a model
of the ratio of visibilities for the various bases
5Visibilities of COROT targets
Uniform disk model
baseline 180 m, J
Limb darkening model
smallest
largest
diameter of main COROT targets
- Precision on visibility limited by
- instrumental stability
- limb darkening model
HD 43587 HD 49933
Precision on diameter depends on visibility slope
6Parallax and angular diameter of primary targets
????2R / d
typical relative error on ? 0.2-0.3 for ?
0.3 mas
error on diameter dominated by error on
parallax BUT small error on ? relation between
Teff and mV (independent estimate of Teff)
7Differential phase measurement and photocenter
displacement
spectroscopic profile
photocenter displacement depends on diameter,
vsini
8Proposed set-up for rotation measurement
- 3 AT
- perpendicular baselines
- high resolution spectroscopy (R15000)
photocenter displacement depends on diameter
vsini
if vsini is already known from spectroscopy, we
can determine diameter very efficient for stars
with high vsini, even for small angular diamaters
(e.g. HD181555)
9Program summary
- 80 hours are necessary to complete the program
on all accessible COROT primary targets - 16 h have been granted to the program on LUAN and
OCA guaranteed time on 2nd semester 2006 (2x4h
for differential visibilities / BCD ) and 1st
semester 2007 (2x4h for differential phase / HR) - The complement has to be claimed on open time and
on CNRS-INSU guaranteed time (same period)