TY - JOUR
T1 - Strong constraints to the putative planet candidate around VB 10 using Doppler spectroscopy
AU - Anglada-Escudé, Guillem
AU - Shkolnik, Evgenya L.
AU - Weinberger, Alycia J.
AU - Thompson, Ian B.
AU - Osip, David J.
AU - Debes, John H.
PY - 2010
Y1 - 2010
N2 - We present new radial velocity (RV) measurements of the ultra-cool dwarf VB 10, which was recently announced to host a giant planet detected with astrometry. The new observations were obtained using optical spectrographs (MIKE/Magellan and ESPaDOnS/CFHT) and cover 65% of the reported period of 270 days. The nominal precision of the new Doppler measurements is about 150 ms -1 while their standard deviation is 250 ms-1. However, there are indications that such a larger variation is due to uncontrolled systematic errors. We apply least-squares periodograms to identify the most significant signals and evaluate their false alarm probabilities (FAPs). We show that this method is the proper generalization to astrometric data because (1) it mitigates the coupling of the orbital parameters with the parallax and proper motion, and (2) it permits a direct generalization to include nonlinear Keplerian parameters in a combined fit to astrometry and RV data. Our analysis of the astrometry alone uncovers the reported 270 day period and an even stronger signal at ∼50 days. We estimate the uncertainties in the parameters using a Markov chain Monte Carlo approach. Although the new data alone cannot rule out the presence of a candidate, when combined with published RV measurements, the FAPs of the best solutions grow to unacceptable levels strongly suggesting that the observed astrometric wobble is not due to an unseen companion. The new measurements put an upper limit of m sin i ∼2.5 m jup for a companion with a period shorter than one year and moderate eccentricities.
AB - We present new radial velocity (RV) measurements of the ultra-cool dwarf VB 10, which was recently announced to host a giant planet detected with astrometry. The new observations were obtained using optical spectrographs (MIKE/Magellan and ESPaDOnS/CFHT) and cover 65% of the reported period of 270 days. The nominal precision of the new Doppler measurements is about 150 ms -1 while their standard deviation is 250 ms-1. However, there are indications that such a larger variation is due to uncontrolled systematic errors. We apply least-squares periodograms to identify the most significant signals and evaluate their false alarm probabilities (FAPs). We show that this method is the proper generalization to astrometric data because (1) it mitigates the coupling of the orbital parameters with the parallax and proper motion, and (2) it permits a direct generalization to include nonlinear Keplerian parameters in a combined fit to astrometry and RV data. Our analysis of the astrometry alone uncovers the reported 270 day period and an even stronger signal at ∼50 days. We estimate the uncertainties in the parameters using a Markov chain Monte Carlo approach. Although the new data alone cannot rule out the presence of a candidate, when combined with published RV measurements, the FAPs of the best solutions grow to unacceptable levels strongly suggesting that the observed astrometric wobble is not due to an unseen companion. The new measurements put an upper limit of m sin i ∼2.5 m jup for a companion with a period shorter than one year and moderate eccentricities.
KW - Astrometry
KW - Methods: statistical
KW - Stars: individual (VB 10)
KW - Techniques: radial velocities
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U2 - 10.1088/2041-8205/711/1/L24
DO - 10.1088/2041-8205/711/1/L24
M3 - Article
AN - SCOPUS:77949528799
SN - 2041-8205
VL - 711
SP - L24-L29
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
IS - 1 PART 2
ER -