Extrasolar Planet Detection with the AFOE

Detection of a high-eccentricity low-mass companion to HD 89744

Introduction

The AFOE has been designed to provide the required precison and stability to detect the wobble induced on the star by the presence of a planet.

Indeed, both the planet and the star revolve around their common center of gravity. While the center of gravity is very close to the center of the star, it is not exactly at the center of the star.

Therefore the star wobbles around the center of gravity with the same period as the planet. The more massive the planet and the closer the orbit the larger will be the amplitude of the wobble.

By measuring the doppler shift caused by the wobble of the star on the light it emits, we can detect such a periodic motion.

This wobble is very small, therefore very stable and precise measurements are needed to make such a detection. The amplitude if the wobble induced by Jupiter on the Sun is 13 meters per second, or 29 miles per hour (1 m/s is 2.237 mph).

Animations for some simulations of orbit are now available.

Results

The AFOE extrasolar program has since

• detected a high-eccentricity low-mass companion to HD 89744.
• detected a multiple planetary system around the star Upsilon Andromedae.
• detected a planet around the star rho Coronae Borealis.
• confirmed the presence of a 3.9 Jupiter mass planet around the star tau Boötis.
• confirmed the presence of a 0.5 Jupiter mass planet around the star 51 Pegasi.
• Presented at the 194th AAS meeting:
  "Evidence for a System of planets orbiting upsilon Andromedae",
  a poster presentation showing the evidence for a system of 3 giant planets around the star Upsilon Andromedae and the results of dynamical stability calculations to further contrain the properties of the system.
• Published in The Astrophysical Journal Letter (v. 494, p. L85)
  "A Search for Line Shape and Depth Variations in 51 Pegasi and Tau Boötis" ,
  where our analysis of spectroscopic observations of 51 Pegasi and tau Boötis with the AFOE show no periodic changes in the shapes of their line profiles; these results for 51 Peg are in significant conflict with those reported by Gray and Hatzes (1997).
• Published in The Astrophysical Journal Supplement (v. 117, p. 563-85)
  "Exoplanets or Dynamic Atmospheres? The Radial Velocity and Line Shape Variations of 51Pegasi and Tau Boötis. " ,
  where we present expanded and detailed analysis of spectroscopic observations of 51 Pegasi and tau Boötis, that show no evidence for periodic line-shape changes,at a level that rules out pulsations as the source of the radial velocity variability.
• Presented a talk at IAU Colloquium 170 on Precise Stellar Radial Velocities , Victoria, BC, June 1998:
  The advanced fiber-optic echelle (AFOE) and extrasolar planet searches, where we discuss the status of the instrument, as well as an upgrade to the instrument, a Fabry-Perot reference, which may prove important both for the AFOE and for all Precision Radial Velocity (PRV) facilities.
• Presented a poster at IAU Colloquium 170 on Precise Stellar Radial Velocities , Victoria, BC, June 1998:
  "The Planet Orbiting RhoCrB" , where we present updated orbital parameters of rhoCrB, and discuss various planet formation scenarios in view of the observational constrains.
• Presented a poster at The 10th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun , Cambridge, July 1997:
  "51 Pegasi and Tau Boötis: Planets or Pulsations", where we discuss the suggestion (Gray 1997) that the radial velocity variations observed in the spectra of 51 Pegasi are the result of stellar pulsations as opposed to the reflex motion due to an orbital companion.

References

1. Exoplanet Research with the Advanced Fiber Optic Echelle, Korzennik et al., 1997, poster presented at the 10th Cool Star Meeting (July 1997, Cambridge, MA
2. The AFOE Program for Extra Solar Planet Research, Noyes et al., 1997, in "Planets Beyond the Solar System and the Next Generation of Space Missions", Space Telescope Science Institute Workshop, P.A.S.P., in press.
3. HD 3346., Noyes, R., Korzennik, S., Nisenson, P., Jha, S., Krockenberger, M., Brown, T., Kennelly, T., Rowland, C., Horner, S., 1996, IAUCirc. 6316.
4. Precise Radial Velocity Measurements of 51 Pegasi with the AFOE Spectrograph Kennelly, E.J., Brown, T. M., Rowland, C., Horner, S.D., Korzennik, S.G., Krockenberger, M., Nisenson, P., Noyes, R.W., 1995, BAAS, 187, 7005.

Other Sites

• Tim Brown's STellar Astrophysics & Research on Exoplanets project (aka STARE) Web page.
  STARE uses precise time-series photometry to search for extrasolar giant planets transiting their parent stars.
• Jean Schneider's Extrasolar Planets Encyclopaedia (France), or the US mirror site.
• The San Francisco State University Planet Search Project Web page.

AFOE Home page.
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