Bibcode
Gettel, Sara; Wolszczan, A.; Niedzielski, A.; Nowak, G.; Adamow, M.; Zielinski, P.; Maciejewski, G.
Referencia bibliográfica
American Astronomical Society, AAS Meeting #219, #125.03
Advertised on:
1
2012
Número de citas
0
Número de citas referidas
0
Descripción
We present the discovery of sub-stellar mass companions to six giant
stars by the ongoing Penn State-Torun Planet Search conducted with the
Hobby-Eberly Telescope. Each system has a single planet, with minimum
masses ranging from 0.9 to 5.3 MJ and orbits ranging from 0.9 to 5.6
years, the longest period yet found by our survey. Three other stars
exhibit long-term non-linear RV trends, indicative of additional
companions that may be low-mass stars or brown dwarfs. If these
companions prove to be substellar, they add to a growing number of
companions to giants that have minimum masses in excess of 10 MJ, making
them candidates for either brown dwarfs or supermassive planets.
Such systems may require a gravitational instability in the
circumstellar disk to form. The two remaining stars have significant RV
noise due to intrinsic stellar variability, making it more difficult to
detect a low-amplitude periodic signal. If the noise component of the
observed RV variations is due to solar-type oscillations, we show, using
all the published data for the substellar companions to giants, that its
amplitude is anti-correlated with stellar metallicity. It is not yet
clearly established whether the metallicity - planet frequency
correlation observed in dwarfs also holds for giants, though the
apparent increase in RV noise for low-metallicity giants must bias these
studies.