19 research outputs found
Search for Nanosecond Near-infrared Transients around 1280 Celestial Objects
Stars and planetary system
The Gemini Planet Imager Exoplanet Survey: Giant Planet and Brown Dwarf Demographics From 10-100 AU
We present a statistical analysis of the first 300 stars observed by the
Gemini Planet Imager Exoplanet Survey (GPIES). This subsample includes six
detected planets and three brown dwarfs; from these detections and our contrast
curves we infer the underlying distributions of substellar companions with
respect to their mass, semi-major axis, and host stellar mass. We uncover a
strong correlation between planet occurrence rate and host star mass, with
stars M 1.5 more likely to host planets with masses between 2-13
M and semi-major axes of 3-100 au at 99.92% confidence. We fit a
double power-law model in planet mass (m) and semi-major axis (a) for planet
populations around high-mass stars (M 1.5M) of the form , finding = -2.4 0.8 and
= -2.0 0.5, and an integrated occurrence rate of %
between 5-13 M and 10-100 au. A significantly lower occurrence rate
is obtained for brown dwarfs around all stars, with 0.8% of
stars hosting a brown dwarf companion between 13-80 M and 10-100
au. Brown dwarfs also appear to be distributed differently in mass and
semi-major axis compared to giant planets; whereas giant planets follow a
bottom-heavy mass distribution and favor smaller semi-major axes, brown dwarfs
exhibit just the opposite behaviors. Comparing to studies of short-period giant
planets from the RV method, our results are consistent with a peak in
occurrence of giant planets between ~1-10 au. We discuss how these trends,
including the preference of giant planets for high-mass host stars, point to
formation of giant planets by core/pebble accretion, and formation of brown
dwarfs by gravitational instability.Comment: 52 pages, 18 figures. AJ in pres
HD 165054: An Astrometric Calibration Field for High-contrast Imagers in Baade's Window
We present a study of the HD 165054 astrometric calibration field that has been periodically observed with the Gemini Planet Imager (GPI). HD 165054 is a bright star within Baade's Window, a region of the galactic plane with relatively low extinction from interstellar dust. HD 165054 was selected as a calibrator target due to the high number density of stars within this region (~3 stars per square arcsecond with H < 22), necessary because of the small field of view of the GPI. Using nine epochs spanning over five years, we have fit a standard five-parameter astrometric model to the astrometry of seven background stars within close proximity to HD 165054 (Ï < 2''). We achieved a proper motion precision of ~0.3 mas yrâ»Âč and constrained the parallax of each star to be âŸ1 mas. Our measured proper motions and parallax limits are consistent with the background stars being a part of the galactic bulge. Using these measurements, we find no evidence of any systematic trend of either the plate scale or the north angle offset of GPI between 2014 and 2019. We compared our model describing the motions of the seven background stars to observations of the same field in 2014 and 2018 obtained with Keck/NIRC2, an instrument with excellent astrometric calibration. We find that the predicted position of the background sources is consistent with that measured by NIRC2, within the uncertainties of the calibration of the two instruments. In the future, we will use this field as a standard astrometric calibrator for the upgrade of GPI and potentially for other high-contrast imagers
An updated visual orbit of the directly-imaged exoplanet 51 Eridani b and prospects for a dynamical mass measurement with Gaia
We present a revision to the visual orbit of the young, directly-imaged
exoplanet 51 Eridani b using four years of observations with the Gemini Planet
Imager. The relative astrometry is consistent with an eccentric
() orbit at an intermediate inclination
(\,deg), although circular orbits cannot be excluded due to
the complex shape of the multidimensional posterior distribution. We find a
semi-major axis of \,au and a period of
\,yr, assuming a mass of 1.75\,M for the host
star. We find consistent values with a recent analysis of VLT/SPHERE data
covering a similar baseline. We investigated the potential of using absolute
astrometry of the host star to obtain a dynamical mass constraint for the
planet. The astrometric acceleration of 51~Eri derived from a comparison of the
{\it Hipparcos} and {\it Gaia} catalogues was found to be inconsistent at the
2--3 level with the predicted reflex motion induced by the orbiting
planet. Potential sources of this inconsistency include a combination of random
and systematic errors between the two astrometric catalogs or the signature of
an additional companion within the system interior to current detection limits.
We also explored the potential of using {\it Gaia} astrometry alone for a
dynamical mass measurement of the planet by simulating {\it Gaia} measurements
of the motion of the photocenter of the system over the course of the extended
eight-year mission. We find that such a measurement is only possible (\%
probability) given the most optimistic predictions for the {\it Gaia} scan
astrometric uncertainties for bright stars, and a high mass for the planet
(\,M).Comment: 17 pages, 11 figures. Accepted for publication in the Astronomical
Journa
First Resolved Scattered-light Images of Four Debris Disks in Scorpius-Centaurus with the Gemini Planet Imager
We present the first spatially resolved scattered-light images of four debris disks around members of the Scorpius-Centaurus (Sco-Cen) OB association with high-contrast imaging and polarimetry using the Gemini Planet Imager (GPI). All four disks are resolved for the first time in polarized light, and one disk is also detected in total intensity. The three disks imaged around HD 111161, HD 143675, and HD 145560 are symmetric in both morphology and brightness distribution. The three systems span a range of inclinations and radial extents. The disk imaged around HD 98363 shows indications of asymmetries in morphology and brightness distribution, with some structural similarities to the HD 106906 planetâdisk system. Uniquely, HD 98363 has a wide comoving stellar companion, Wray 15-788, with a recently resolved disk with very different morphological properties. HD 98363 A/B is the first binary debris disk system with two spatially resolved disks. All four targets have been observed with ALMA, and their continuum fluxes range from one nondetection to one of the brightest disks in the region. With the new results, a total of 15 A/F stars in Sco-Cen have resolved scattered-light debris disks, and approximately half of these systems exhibit some form of asymmetry. Combining the GPI disk structure results with information from the literature on millimeter fluxes and imaged planets reveals a diversity of disk properties in this young population. Overall, the four newly resolved disks contribute to the census of disk structures measured around A/F stars at this important stage in the development of planetary systems