Radial Velocity Method of Companion Detection

Debra Fischer (University of California, Berkeley)

Abstract:

Doppler surveys have discovered about 50 extrasolar planets orbiting nearby F,G,K and M-type stars. Most of the host stars have reflex velocity amplitudes greater than 30 m/s, induced by planets with masses similar to our Jupiter, but with semi-major axes less than a few AU. The highest precision surveys are beginning to detect close-in, Saturn-mass planets and Jupiter-mass planets in wider orbits. The detection of a planet-transit in November 1999 yielded the first extrasolar planet radius and hence density, and implies that the Doppler-detected planets are gaseous rather than solid.

These discoveries have unexpected properties which will bear on interferometric searches for extrasolar planets:

• The distribution of planet masses is strongly peaked toward low masses and appears to be truncated at masses above about 10 MJupiter.

• Extrasolar planets orbiting beyond 0.2 AU appear to be in orbits that are more eccentric than those in our own solar system.

• The detection of the first system of planets around Upsilon Andromedae was made in April 1999. Far from being unique, we see residual velocity trends in more than one third of the planet-bearing stars in our sample. Thus, multiple planet systems appear to be common.

These finding suggest that low-mass planets and multiple planet systems may be common and orbital fitting of astrometric observations will need to allow for this added complexity. The Doppler observations should be useful in constraining some of the free parameters in the orbital solution.

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Selected Reading 1999-2000

A discussion of residual velocity trends and multiple planet systems:

• "Planetary Companions to HD 12661, HD 92788, Hd 38529 and Variations in Keplerian Residuals of Extrasolar Planets ", Fischer, D. A., Marcy, G. W., Butler, R. P., Vogt, S. S., Frink, S. Apps, K. 2000., submitted to ApJ.

A discussion of metallicity in stars with extrasolar planets:

• "Planetary Companions to the Metal-Rich Stars BD-10 3166 and HD 52265 ", Butler, R. P., Vogt, S. S., Marcy, G. W., Fischer, D. A., Henry, G.W., Apps, K., 2000. accepted by ApJ.

The lowest mass extrasolar planet detections:

• "Sub-Saturn Planetary Candidates of HD 16141 and HD 46375 ", Marcy, G. W., Butler, R. P., Vogt, S. S., 2000., ApJL 536, 43

• "Six New Planets from the Keck Precision Velocity Survey ", Vogt, S. S., Marcy, G. W., Butler, R. P., Apps, K., 2000. ApJ, 536, 902

The transit of HD 209458:

• "A Transiting 51 Pegasi-Type Planet", Henry, G.W., Marcy, G.W., Butler, R.P., Vogt, S.S. 2000. ApJ, 529 41L.

• "Detection of Planetary Transits Across a Sun-like Star", Charbonneau, D., Brown, T. M., Latham, D. W, Mayor, M. 2000. ApJL 529, 45

A good review paper:

• "Extrasolar Planets Around Main Sequence Stars", Marcy, G.W., Cochran, W., Mayor, M., to appear in "Protostars and Planets IV"

The first multiple planet system:

• "Evidence for Multiple Companions to Upsilon Andromedae" Butler, R.P., Marcy, G.W., Fischer, D.A., Brown, T.M.; Contos, A.R., Korzennik, S.G.,Nisenson, P., Noyes, R.W. 1999., 1999. ApJ 526, 916.

• "Two New Candidate Planets in Eccentric Orbits" , Marcy, G.W., Butler, R. P., Vogt, S.S. Fischer, D., Liu, M.C. 1999. ApJ 520, 239.

• "Planetary Companions around Two Solar-Type Stars: HD 195019 and HD 217107" , Fischer, D., Marcy, G.W., Butler, R.P., Vogt, S.S., Apps, K.A., 1999. PASP, 111, 50.