Friday, May 3, 2013

1305.0280 (Jason T. Wright et al.)

MARVELS-1: A face-on double-lined binary star masquerading as a resonant planetary system; and consideration of rare false positives in radial velocity planet searches    [PDF]

Jason T. Wright, Arpita Roy, Suvrath Mahadevan, Sharon X. Wang, Eric B. Ford, Matt Payne, Brian L. Lee, Ji Wang, Justin R. Crepp, B. Scott Gaudi, Jason Eastman, Joshua Pepper, Jian Ge, Scott W. Fleming, Luan Ghezzi, Jonay I. Gonzalez-Hernandez, Phillip Cargile, Keivan G. Stassun, John Wisniewski, Leticia Dutra-Ferreira, Gustavo F. Porto de Mello, Marcio A. G. Maia, Luiz Nicolaci da Costa, Ricardo L. C. Ogando, Basilio X. Santiago, Donald P. Schneider, Fred R. Hearty
We have analyzed new and previously published radial velocity observations of MARVELS-1, known to have an ostensibly substellar companion in a ~6- day orbit. We find significant (~100 m/s) residuals to the best-fit model for the companion, and these residuals are naively consistent with an interior giant planet with a P = 1.965d in a nearly perfect 3:1 period commensuribility (|Pb/Pc - 3| < 10^{-4}). We have performed several tests for the reality of such a companion, including a dynamical analysis, a search for photometric variability, and a hunt for contaminating stellar spectra. We find many reasons to be critical of a planetary interpretation, including the fact that most of the three-body dynamical solutions are unstable. We find no evidence for transits, and no evidence of stellar photometric variability. We have discovered two apparent companions to MARVELS-1 with adaptive optics imaging at Keck; both are M dwarfs, one is likely bound, and the other is likely a foreground object. We explore false-alarm scenarios inspired by various curiosities in the data. Ultimately, a line profile and bisector analysis lead us to conclude that the ~100 m/s residuals are an artifact of spectral contamination from a stellar companion contributing ~15-30% of the optical light in the system. We conclude that origin of this contamination is the previously detected radial velocity companion to MARVELS-1, which is not, as previously reported, a brown dwarf, but in fact a G dwarf in a face-on orbit.
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