65 research outputs found
Which Radial Velocity Exoplanets Have Undetected Outer Companions?
(Abridged) The observed radial velocity (RV) eccentricity distribution for
extrasolar planets in single-planet systems shows that a significant fraction
of planets are eccentric (). Here we investigate the effects on an RV
planet's eccentricity produced by undetected outer companions. We have carried
out Monte Carlo simulations of mock RV data to understand this effect and
predict its impact on the observed distribution. We first quantify the
statistical effect of undetected outer companions and show that this alone
cannot explain the observed distribution. We then modify the simulations to
consist of two populations, one of zero-eccentricity planets in double-planet
systems and the other of single planets drawn from an eccentric distribution.
Our simulations show that a good fit to the observed distribution is obtained
with 45% zero-eccentricity double-planets and 55% single eccentric planets.
Matching the observed distribution allows us to determine the probability that
a known RV planet's orbital eccentricity has been biased by an undetected
wide-separation companion. Our simulations show that moderately-eccentric
planets, with and , have a and probability, respectively, of having an undetected outer companion. We
encourage both high-contrast direct imaging and RV follow-up surveys of known
RV planets with moderate eccentricities to test our predictions and look for
previously undetected outer companions.Comment: 23 pages (12 text, 2 tables, 9 figures). Accepted to the
Astrophysical Journal 30 June 200
High-Contrast 3.8 Micron Imaging Of The Brown Dwarf/Planet-Mass Companion to GJ 758
We present L' band (3.8 ) MMT/Clio high-contrast imaging data for the
nearby star GJ 758, which was recently reported by Thalmann et al. (2009) to
have one -- possibly two-- faint comoving companions (GJ 758B and ``C",
respectively). GJ 758B is detected in two distinct datasets. Additionally, we
report a \textit{possible} detection of the object identified by Thalmann et al
as ``GJ 758C" in our more sensitive dataset, though it is likely a residual
speckle. However, if it is the same object as that reported by Thalmann et al.
it cannot be a companion in a bound orbit. GJ 758B has a H-L' color redder than
nearly all known L--T8 dwarfs. Based on comparisons with the COND evolutionary
models, GJ 758B has T 560 K and a mass
ranging from 10--20 M if it is 1 Gyr old to 25--40
M if it is 8.7 Gyr old. GJ 758B is likely in a highly eccentric orbit, e
0.73, with a semimajor axis of 44 AU. Though GJ 758B is sometimes discussed within the context of
exoplanet direct imaging, its mass is likely greater than the deuterium-burning
limit and its formation may resemble that of binary stars rather than that of
jovian-mass planets.Comment: 14 pages, 3 figures. Accepted for publication in The Astrophysical
Journal Letter
Direct Imaging Confirmation and Characterization of a Dust-Enshrouded Candidate Exoplanet Orbiting Fomalhaut
We present Subaru/IRCS J band data for Fomalhaut and a (re)reduction of
archival 2004--2006 HST/ACS data first presented by Kalas et al. (2008). We
confirm the existence of a candidate exoplanet, Fomalhaut b, in both the 2004
and 2006 F606W data sets at a high signal-to-noise. Additionally, we confirm
the detection at F814W and present a new detection in F435W. Fomalhaut b's
space motion may be consistent with it being in an apsidally-aligned, non
debris ring-crossing orbit, although new astrometry is required for firmer
conclusions. We cannot confirm that Fomalhaut b exhibits 0.7-0.8 mag
variability cited as evidence for planet accretion or a semi-transient dust
cloud. The new, combined optical SED and IR upper limits confirm that emission
identifying Fomalhaut b originates from starlight scattered by small dust, but
this dust is most likely associated with a massive body. The Subaru and
IRAC/4.5 micron upper limits imply M < 2 Mj, still consistent with the range of
Fomalhaut b masses needed to sculpt the disk. Fomalhaut b is very plausibly "a
planet identified from direct imaging" even if current images of it do not,
strictly speaking, show thermal emission from a directly imaged planet.Comment: 13 pages, 3 figures; ApJ Letters in press. Fixed one outdated
reference and a few typo
New Extinction and Mass Estimates of the Low-mass Companion 1RXS 1609 B with the Magellan AO System: Evidence of an Inclined Dust Disk
We used the Magellan adaptive optics system to image the 11 Myr substellar
companion 1RXS 1609 B at the bluest wavelengths to date (z' and Ys). Comparison
with synthetic spectra yields a higher temperature than previous studies of
and significant dust extinction of
mag. Mass estimates based on the DUSTY tracks gives
0.012-0.015 Msun, making the companion likely a low-mass brown dwarf surrounded
by a dusty disk. Our study suggests that 1RXS 1609 B is one of the 25% of Upper
Scorpius low-mass members harboring disks, and it may have formed like a star
and not a planet out at 320 AU.Comment: 5 pages, 4 figures; accepted to ApJ
New Extinction and Mass Estimates from Optical Photometry of the Very Low Mass Brown Dwarf Companion CT Chamaeleontis B with the Magellan AO System
We used the Magellan adaptive optics (MagAO) system and its VisAO CCD camera
to image the young low mass brown dwarf companion CT Chamaeleontis B for the
first time at visible wavelengths. We detect it at r', i', z', and Ys. With our
new photometry and Teff~2500 K derived from the shape its K-band spectrum, we
find that CT Cha B has Av = 3.4+/-1.1 mag, and a mass of 14-24 Mj according to
the DUSTY evolutionary tracks and its 1-5 Myr age. The overluminosity of our r'
detection indicates that the companion has significant Halpha emission and a
mass accretion rate ~6*10^-10 Msun/yr, similar to some substellar companions.
Proper motion analysis shows that another point source within 2" of CT Cha A is
not physical. This paper demonstrates how visible wavelength AO photometry (r',
i', z', Ys) allows for a better estimate of extinction, luminosity, and mass
accretion rate of young substellar companions.Comment: Accepted for publication in ApJ; 6 figure
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