245 research outputs found
No Sub-Saturn Mass Planet Desert in the CORALIE/HARPS Radial Velocity Sample
We analyze the CORALIE/HARPS sample of exoplanets (Mayor et al. 2011) found
by the Doppler radial velocity method for signs of the predicted "desert" at
10- caused by runaway gas accretion at semimajor axes of AU. We find that these data are not consistent with this prediction. This
result is similar to the finding by the MOA gravitational microlensing survey
that found no desert in the exoplanet distribution for exoplanets in slightly
longer period orbits and somewhat lower host masses (Suzuki et al. 2018).
Together, these results imply that the runaway accretion scenario of the core
accretion theory does not have a large influence on the final mass and
semimajor axis distribution of exoplanets.Comment: accepted by the Astronomical Journal, 19 pages with 5 figure
Photometry of K2 Campaign 9 bulge data
In its Campaign 9, K2 observed dense regions toward the Galactic bulge in
order to constrain the microlensing parallaxes and probe for free-floating
planets. Photometric reduction of the \emph{K2} bulge data poses a significant
challenge due to a combination of the very high stellar density, large pixels
of the Kepler camera, and the pointing drift of the spacecraft. Here we present
a new method to extract K2 photometry in dense stellar regions. We extended the
Causal Pixel Model developed for less-crowded fields, first by using the pixel
response function together with accurate astrometric grids, second by combining
signals from a few pixels, and third by simultaneously fitting for an
astrophysical model. We tested the method on two microlensing events and a
long-period eclipsing binary. The extracted K2 photometry is an order of
magnitude more precise than the photometry from other method
Measurement of the Free-Floating Planet Mass Function with Simultaneous Euclid and WFIRST Microlensing Parallax Observations
Free-floating planets are the remnants of violent dynamical rearrangements of
planetary systems. It is possible that even our own solar system ejected a
large planet early in its evolution. WFIRST will have the ability to detect
free-floating planets over a wide range of masses, but it will not be able to
directly measure their masses. Microlensing parallax observations can be used
to measure the masses of isolated objects, including free-floating planets, by
observing their microlensing events from two locations. The intra-L2 separation
between WFIRST and Euclid is large enough to enable microlensing parallax
measurements, especially given the exquisite photometric precision that both
spacecraft are capable of over wide fields. In this white paper we describe how
a modest investment of observing time could yield hundreds of parallax
measurements for WFIRST's bound and free-floating planets. We also describe how
a short observing campaign of precursor observations by Euclid can improve
WFIRST's bound planet and host star mass measurements.Comment: Astro2020 White Pape
WFIRST Exoplanet Mass-measurement Method Finds a Planetary Mass of 39 ± 8 M_â for OGLE-2012-BLG-0950Lb
We present the analysis of the simultaneous high-resolution images from the Hubble Space Telescope and Keck adaptive optics system of the planetary event OGLE-2012-BLG-0950 that determine that the system consists of a 0.58 ± 0.04 M_â host star orbited by a 39 ± 8 M_â planet at a projected separation of 2.54 ± 0.23 au. The planetary system is located at a distance of 2.19 ± 0.23 kpc from Earth. This is the second microlens planet beyond the snow line with a mass measured to be in the mass range 20â80 M_â. The runaway gas accretion process of the core accretion model predicts fewer planets in this mass range. This is because giant planets are thought to be growing rapidly at these masses, and they rarely complete growth at this mass. So this result suggests that the core accretion theory may need revision. This analysis also demonstrates the techniques that will be used to measure the masses of planets and their host stars by the WFIRST exoplanet microlensing survey: one-dimensional microlensing parallax combined with the separation and brightness measurement of the unresolved source and host stars to yield multiple redundant constraints on the masses and distance of the planetary system
Keck Observations Confirm a Super-Jupiter Planet Orbiting M Dwarf OGLE-2005-BLG-071L
We present adaptive optics imaging from the NIRC2 instrument on the Keck II telescope that resolves the exoplanet host (and lens) star as it separates from the brighter source star. These observations yield the K-band brightness of the lens and planetary host star, as well as the lens-source relative proper motion, ”_(rel,H), in the heliocentric reference frame. The ”_(rel,H) measurement allows for the determination of the microlensing parallax vector, Ï_E, which had only a single component determined by the microlensing light curve. The combined measurements of ”_(rel,H) and K L provide the masses of the host star, M_(host) = 0.426 ± 0.037 Mâ, and planet, m_p = 3.27 ± 0.32M_(Jupiter) with a projected separation of 3.4 ± 0.5 au. This confirms the tentative conclusion of a previous paper that this super-Jupiter mass planet, OGLE-2005-BLG-071Lb, orbits an M dwarf. Such planets are predicted to be rare by the core accretion theory and have been difficult to find with other methods, but there are two such planets with firm mass measurements from microlensing, and an additional 11 planetary microlens events with host mass estimates <0.
0.5Mâ and planet mass estimates >2 Jupiter masses that could be confirmed by high angular follow-up observations. We also point out that OGLE-2005-BLG-071L has separated far enough from its host star that it should be possible to measure the host-star metallicity with spectra from a high angular resolution telescope such as Keck, the Very Large Telescope, the Hubble Space Telescope, or the James Webb Space Telescope
A Planetary Microlensing Event with an Unusually Red Source Star: MOA-2011-BLG-291
We present the analysis of planetary microlensing event MOA-2011-BLG-291,
which has a mass ratio of and a source star that
is redder (or brighter) than the bulge main sequence. This event is located at
a low Galactic latitude in the survey area that is currently planned for NASA's
WFIRST exoplanet microlensing survey. This unusual color for a microlensed
source star implies that we cannot assume that the source star is in the
Galactic bulge. The favored interpretation is that the source star is a lower
main sequence star at a distance of kpc in the Galactic disk.
However, the source could also be a turn-off star on the far side of the bulge
or a sub-giant in the far side of the Galactic disk if it experiences
significantly more reddening than the bulge red clump stars. However, these
possibilities have only a small effect on our mass estimates for the host star
and planet. We find host star and planet masses of and from a Bayesian
analysis with a standard Galactic model under the assumption that the planet
hosting probability does not depend on the host mass or distance. However, if
we attempt to measure the host and planet masses with host star brightness
measurements from high angular resolution follow-up imaging, the implied masses
will be sensitive to the host star distance. The WFIRST exoplanet microlensing
survey is expected to use this method to determine the masses for many of the
planetary systems that it discovers, so this issue has important design
implications for the WFIRST exoplanet microlensing survey
Measurement of the Free-Floating Planet Mass Function with Simultaneous Euclid and WFIRST Microlensing Parallax Observations
Free-floating planets are the remnants of violent dynamical rearrangements of planetary systems. It is possible that even our own solar system ejected a large planet early in its evolution. WFIRST will have the ability to detect free-floating planets over a wide range of masses, but it will not be able to directly measure their masses. Microlensing parallax observations can be used to measure the masses of isolated objects, including free-floating planets, by observing their microlensing events from two locations. The intra-L2 separation between WFIRST and Euclid is large enough to enable microlensing parallax measurements, especially given the exquisite photometric precision that both spacecraft are capable of over wide fields. In this white paper we describe how a modest investment of observing time could yield hundreds of parallax measurements for WFIRST's bound and free-floating planets. We also describe how a short observing campaign of precursor observations by Euclid can improve WFIRST's bound planet and host star mass measurements
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