Abstract
51 Pegasi, one of many nearby Sun-like stars, was undistinguished until the recent detections of apparent variations in its radial velocity, which have been attributed to reflex motion caused by a planetary companion1,2. The velocity variation inferred from variations in the spectral lines of 51 Peg has an amplitude of 56ā59 m sāl and a period of 4.23 days, implying a planet of at least half the mass of Jupiter moving in an embarrassingly small orbit of 0.05 astronomical units. But the techniques currently used to identify these exceedingly small radial velocity variations do not allow for the possibility that changes of comparable size might be occurring in the intrinsic shapes of the spectral lines; such variations are expected when a star pulsates or has spots on its surface, and could be mistaken for radial velocity variations. Here I present high-spectral-resolution observations of 51 Peg that show that its spectral lines exhibit intrinsic shape variations with a period of 4.23 days, and an amplitude comparable to that previously attributed1,2 to radial velocity variations. As the presence of a planet will not influence the shapes of spectral lines, these variations are likely to reflect a hitherto unknown mode of stellar oscillation. The presence of a planet is not required to explain the data.
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References
Mayor, M. & Queloz, D. A Jupiter-mass companion to a solar-type star. Nature 378, 355ā359 (1995).
Marcy, G. W. et al. The planet around 51 Pegasi. Astrophys. J. (submitted).
Gray, D. F., Baliunas, S. L., Lockwood, G. W. & Skiff, B. A. Variations of Ī² Comae through a magnetic minimum. Astrophys. J. 456, 365ā369 (1996).
Gray, D. F., Baliunas, S. L., Lockwood, G. W. & Skiff, B. A. Magnetic, photometric, temperature, and granulation variations of Ī¾ Boo A 1984ā1993. Astrophys. J. 465, 945ā950 (1996).
Gray, D. F. in Instrumentation and Research Programmes for Small Telescopes (eds Hearnshaw, J. B. & Cottrell, P. L.) 401ā412 (Reidel, Dordrecht, 1986).
Dravins, D., Lindegren, L. & Nordlund, A. Solar granulationāinfluence of convection on spectral line asymmetries and wavelength shifts. Astron. Astrophys. 96, 345ā364 (1981).
Brandt, P. N. & Solanki, S. K. Solar line asymmetries and the magnetic filling factor. Astron. Astrophys. 231, 221ā234 (1990).
Gray, D. F. Lectures on Spectral-Line Analysis: F, G, and K Stars Ch. 4 (Arva, Ontario, 1988).
Gray, D. F. Observations of spectral line asymmetries and convective velocities in F, G, and K stars. Astrophys. J. 255, 200ā209 (1982).
Hatzes, A. P. Simulations of stellar radial-velocity and spectral line bisector variations. I. Nonradial pulsations. Publ. Astron. Soc. Pacif. 108, 839ā843 (1996).
Toner, C. G. & Gray, D. F. The starpatch on the G8 dwarf Ī¾ Boo A. Astrophys. J. 334, 1008ā1020 (1988).
Gray, D. F. Spectral line-depth ratios as temperature indicators for cool stars. Publ. Astron. Soc. Pacif. 106, 1248ā1257 (1994).
Gray, D. F. Comparing the Sun with other stars along the temperature coordinate. Publ. Astron. Soc. Pacif. 107, 120ā123 (1995).
Gray, D. F. & Livingston, W. C. Monitoring the solar temperature: empirical calibration of the temperature sensitivity of CIĪ»5380. Astrophys. J. 474, 798ā801 (1997).
Perryman, M. A. C. et al. Happarcos distances and mass limits for the planetary candidates: 47 UMa, 70 Vir, and 51 Peg. Astron. Astrophys. 310, L21āL24 (1996).
Henry, G. W., Baliunas, S. L., Donahue, R. A., Soon, W. H. & Saar, S. H. Properties of Sun-like stars with planets. Astrophys. J. 474, 503ā510 (1997).
Dravins, D. Solar and Stellar Granulation (eds Rutten, R. J. & Severino, G.) 153ā160 (Kluwer, Dordrecht, 1989).
Hatzes, A. P., Cochran, W. D. & Johns-Krull, M. Testing the planet hypothesis: a search for variability in the spectral lines shapes of 51 Pegasi. Astrophys. J. (submitted).
Unno, W., Osaki, Y., Ando, H. & Shibahashi, H. Nonradial Oscillations of Stars (Univ. Tokyo Press, 1979).
Xu, Z. The near-IR Na I doublet and Ca II triplet in late-type stars and the determination of stellar atmosphere parameters. Astron. Astrophys. 248, 367ā388 (1991).
Edvardsson, B. et al. The chemical evolution of the galactic disk II. Observational data. Astron. Astrophys. 275, 101ā152 (1993).
Walker, G. A. H., Yang, S., Irwin, A. W. & Campbell, B. Yellow giants: a new class of radial-velocity variable. Astrophys. J. 343, L21āL24 (1989).
Latham, D. W., Stefanik, R. P., Mazeh, T., Mayor, M. & Burki, G. The unseen companion of HD 114762āa probable brown dwarf. Nature 339, 38ā40 (1989).
Marcy, G. W. & Butler, R. P. A planet orbiting 47 Ursae Majoris. Astrophys. J. 464, L153āL156 (1996).
Butler, R. P. & Marcy, G. W. A planetary companion to 70 Virginis. Astrophys. J. 464, L147āL151 (1996).
Butler, R. P., Marcy, G. W., Williams, E., Hauser, H. & Shirts, P. Three new ā51 Peg-typeā planets. Astrophys. J. (submitted).
Cochran, W. D., Hatzes, A. P., Butler, R. P. & Marcy, G. W. The discovery of a planetary companion to 16 Cygni B. Astrophys. J. (submitted).
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Gray, D. Absence of a planetary signature in the spectra of the star 51 Pegasi. Nature 385, 795ā796 (1997). https://doi.org/10.1038/385795a0
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DOI: https://doi.org/10.1038/385795a0
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