In-depth asteroseismic analysis of HR8799
the host of the first directdirect-imaged exoplanetary system
A.-N. Chené (NRC-HIA), E. Kambe (OAO), D. Wright (ROB), P. De Cat (ROB), C. Marois (NRC-HIA),
MOST teamRationale:
Direct imaging of the HR8799 system (Marois et al. 2008) was a major achievement in the study of exoplanets.
However, determining the masses of the companions depends crucially on the age of the parent star. Fortunately,
HR8799 is a Gamma Dor variable and astroseismology may provide an independent age constraint. The orbital
inclination, useful for the fit of the companions’ orbit, may also be determined.

The three planets
HR8799b, c and dobserved at KeckMarois et al. (2008)

MOST Photometric Observations:

f3

MOST

Photometric analysis• First Canadian pace telescope• 10 cm aperture• 1024x1024 CCD• Precision of ~1 ppm (v~6)• Orbital period : 100 min• 42 days of quasi-continuous observations (black points)• More than 45 frequencies identified (cyan curve)• Coordinated with ~1000 spectra (black rectangles)• ~510 spectra from OAO (red filled rectangles)• Total amplitude of 100 mmag (hard from ground!!!)f2 f1• 3 independent frequencies identified• The Short-Time Fourier Transform (up)shows the evolution of the frequencies• f2 seems to disappear during the run!
• Investigation of the many otherfrequencies in progress• Possible variations in amplitude and phase

MultiMulti-site Spectroscopic Campaign~1740 spectra were obtained with Okayama Astronomical Observatory (~510 spectra!),Xinglong Observatory, Tautenburg Observatory, Observatoire de Haute-Provence,
Mercator, ESO-2.2m, McDonald, Lick Observatory and Dominion Astronomical
Observatory over a time-span of two years.
The figure on the left shows clear line-profile variations observed in the OAO spectra.
On the right is the same, but for only ~3 days observed continuously from 4 different
telescopes.

f1 observed

f1 synthetic

Four (4) independent frequencies have been found (including f1, f2 and f3 from photometry), and preliminarymode identification gives l=1 and m=1 for f1 and f2.

f2 observed

f2 synthetic

This figure shows the line-profile variability folded with f1 and f2, after pre-whitening the spectra of the otheridentified frequencies. On the left is the observed variability and on the right, the variability expected for l=1
and m=1 for f1 and f2.
The current determination of the orbital inclination from asteroseismology is significantly larger than the one
found from the orbit of HR8799’s companions. However, with v sin i~40 km/s, if i is small (i.e. lower than30°), frot/fpuls is high and the usual custom tools for asteroseismic analysis may not be appropriate!

Future Work:
After complete determination of the pulsation modes found with the photometry and the spectroscopy, the interior of HR8799 will be modeledusing the most up-to-date models for Gamma Dor Stars and, ideally, HR8799 will be placed in the HR diagram. Also, an asteroseismic tool
including fast rotation velocity may be used in order to get a better constrain of the orbital inclination. Finally, possible amplitude and phasevariations and frequency disappearance will be investigated.
Many thanks to : Gordon Walker (UBC), David Bohlender (HIA), Stephenson L. S. Yang (UVic), Artie P. Hatzes (Tautenburg), Michael Hartmann (Tautenburg), Holger Lehmann (Tautenburg), Christian Nitschelm (Antofagasta),Bruce Macintosh (LLNL), Josh Isaacs (LLNL), Carl Melis (U Cal.), Jason Rowe (AMES), Connie Aerts (Leuven), Tijl Verhost (Leuven), Paul Beck (Leuven), Steven Bleomen (Leuven), Philippe Mathias (OCA)