Precise radial velocities of giant stars - XII. Evidence against the proposed planet Aldebaran b
Radial-velocity variations of the K giant star Aldebaran (<i>α<i/> Tau) were first reported in the early 1990s. After subsequent analyses, the radial-velocity variability with a period of ∼629 d has recently been interpreted as caused by a planet of several Jovian masses.<i>Aims.&l...
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| Hauptverfasser: | , , , , |
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| Dokumenttyp: | Article (Journal) |
| Sprache: | Englisch |
| Veröffentlicht: |
01 May 2019
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| In: |
Astronomy and astrophysics
Year: 2019, Jahrgang: 625 |
| ISSN: | 1432-0746 |
| DOI: | 10.1051/0004-6361/201834028 |
| Online-Zugang: | Verlag, Volltext: https://doi.org/10.1051/0004-6361/201834028 Verlag, Volltext: https://www.aanda.org/articles/aa/abs/2019/05/aa34028-18/aa34028-18.html 
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| Verfasserangaben: | Katja Reichert, Sabine Reffert, Stephan Stock, Trifon Trifonov, and Andreas Quirrenbach |
| Zusammenfassung: | Radial-velocity variations of the K giant star Aldebaran (<i>α<i/> Tau) were first reported in the early 1990s. After subsequent analyses, the radial-velocity variability with a period of ∼629 d has recently been interpreted as caused by a planet of several Jovian masses.<i>Aims.<i/> We want to further investigate the hypothesis of an extrasolar planet around Aldebaran.<i>Methods.<i/> We combine 165 new radial-velocity measurements from Lick Observatory with seven already published data sets comprising 373 radial-velocity measurements. We perform statistical analyses and investigate whether a Keplerian model properly fits the radial velocities. We also perform a dynamical stability analysis for a possible two-planet solution. Furthermore, the possibility of oscillatory convective modes as cause for the observed radial-velocity variability is discussed.<i>Results.<i/> As best Keplerian fit to the combined radial-velocity data we obtain an orbit for the hypothetical planet with a smaller period (<i>P<i/> = 607 d) and a larger eccentricity (<i>e<i/> = 0.33 ± 0.04) than the previously proposed one. However, the residual scatter around that fit is still large, with a standard deviation of 117 ms<sup>−1<sup/>. In 2006/2007, the statistical power of the ∼620 d period showed a temporary but significant decrease. Plotting the growth of power in reverse chronological order reveals that a period around 620 d is clearly present in the newest data but not in the data taken before ∼2006. Furthermore, an apparent phase shift between radial-velocity data and orbital solution is observable at certain times. A two-planet Keplerian fit matches the data considerably better than a single-planet solution, but poses severe dynamical stability issues.<i>Conclusions.<i/> The radial-velocity data from Lick Observatory do not further support but in fact weaken the hypothesis of a substellar companion around Aldebaran. Oscillatory convective modes might be a plausible alternative explanation of the observed radial-velocity variations. |
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| Beschreibung: | Gesehen am 17.12.2019 |
| Beschreibung: | Online Resource |
| ISSN: | 1432-0746 |
| DOI: | 10.1051/0004-6361/201834028 |