86 research outputs found
Dynamical Mass Measurement of the Young Spectroscopic Binary V343 Normae AaAb Resolved With the Gemini Planet Imager
We present new spatially resolved astrometry and photometry from the Gemini
Planet Imager of the inner binary of the young multiple star system V343
Normae, which is a member of the beta Pictoris moving group. V343 Normae
comprises a K0 and mid-M star in a ~4.5 year orbit (AaAb) and a wide 10" M5
companion (B). By combining these data with archival astrometry and radial
velocities we fit the orbit and measure individual masses for both components
of M_Aa = 1.10 +/- 0.10 M_sun and M_Ab = 0.290 +/- 0.018 M_sun. Comparing to
theoretical isochrones, we find good agreement for the measured masses and JHK
band magnitudes of the two components consistent with the age of the beta Pic
moving group. We derive a model-dependent age for the beta Pic moving group of
26 +/- 3 Myr by combining our results for V343 Normae with literature
measurements for GJ 3305, which is another group member with resolved binary
components and dynamical masses.Comment: 12 pages, 7 figures. Accepted to A
Improving and Assessing Planet Sensitivity of the GPI Exoplanet Survey with a Forward Model Matched Filter
We present a new matched filter algorithm for direct detection of point
sources in the immediate vicinity of bright stars. The stellar Point Spread
Function (PSF) is first subtracted using a Karhunen-Lo\'eve Image Processing
(KLIP) algorithm with Angular and Spectral Differential Imaging (ADI and SDI).
The KLIP-induced distortion of the astrophysical signal is included in the
matched filter template by computing a forward model of the PSF at every
position in the image. To optimize the performance of the algorithm, we conduct
extensive planet injection and recovery tests and tune the exoplanet spectra
template and KLIP reduction aggressiveness to maximize the Signal-to-Noise
Ratio (SNR) of the recovered planets. We show that only two spectral templates
are necessary to recover any young Jovian exoplanets with minimal SNR loss. We
also developed a complete pipeline for the automated detection of point source
candidates, the calculation of Receiver Operating Characteristics (ROC), false
positives based contrast curves, and completeness contours. We process in a
uniform manner more than 330 datasets from the Gemini Planet Imager Exoplanet
Survey (GPIES) and assess GPI typical sensitivity as a function of the star and
the hypothetical companion spectral type. This work allows for the first time a
comparison of different detection algorithms at a survey scale accounting for
both planet completeness and false positive rate. We show that the new forward
model matched filter allows the detection of fainter objects than a
conventional cross-correlation technique with a Gaussian PSF template for the
same false positive rate.Comment: ApJ accepte
GPI spectra of HR 8799 c, d, and e from 1.5 to 2.4m with KLIP Forward Modeling
We explore KLIP forward modeling spectral extraction on Gemini Planet Imager
coronagraphic data of HR 8799, using PyKLIP and show algorithm stability with
varying KLIP parameters. We report new and re-reduced spectrophotometry of HR
8799 c, d, and e in H & K bands. We discuss a strategy for choosing optimal
KLIP PSF subtraction parameters by injecting simulated sources and recovering
them over a range of parameters. The K1/K2 spectra for HR 8799 c and d are
similar to previously published results from the same dataset. We also present
a K band spectrum of HR 8799 e for the first time and show that our H-band
spectra agree well with previously published spectra from the VLT/SPHERE
instrument. We show that HR 8799 c and d show significant differences in their
H & K spectra, but do not find any conclusive differences between d and e or c
and e, likely due to large error bars in the recovered spectrum of e. Compared
to M, L, and T-type field brown dwarfs, all three planets are most consistent
with mid and late L spectral types. All objects are consistent with low gravity
but a lack of standard spectra for low gravity limit the ability to fit the
best spectral type. We discuss how dedicated modeling efforts can better fit HR
8799 planets' near-IR flux and discuss how differences between the properties
of these planets can be further explored.Comment: Accepted to AJ, 25 pages, 16 Figure
Performance of the Gemini Planet Imager Non-Redundant Mask and spectroscopy of two close-separation binaries HR 2690 and HD 142527
The Gemini Planet Imager (GPI) contains a 10-hole non-redundant mask (NRM),
enabling interferometric resolution in complement to its coronagraphic
capabilities. The NRM operates both in spectroscopic (integral field
spectrograph, henceforth IFS) and polarimetric configurations. NRM observations
were taken between 2013 and 2016 to characterize its performance. Most
observations were taken in spectroscopic mode with the goal of obtaining
precise astrometry and spectroscopy of faint companions to bright stars. We
find a clear correlation between residual wavefront error measured by the AO
system and the contrast sensitivity by comparing phase errors in observations
of the same source, taken on different dates. We find a typical 5-
contrast sensitivity of at . We explore the
accuracy of spectral extraction of secondary components of binary systems by
recovering the signal from a simulated source injected into several datasets.
We outline data reduction procedures unique to GPI's IFS and describe a newly
public data pipeline used for the presented analyses. We demonstrate recovery
of astrometry and spectroscopy of two known companions to HR 2690 and HD
142527. NRM+polarimetry observations achieve differential visibility precision
of in the best case. We discuss its limitations on
Gemini-S/GPI for resolving inner regions of protoplanetary disks and prospects
for future upgrades. We summarize lessons learned in observing with NRM in
spectroscopic and polarimetric modes.Comment: Accepted to AJ, 22 pages, 14 figure
Characterizing 51 Eri b from 1-5 m: a partly-cloudy exoplanet
We present spectro-photometry spanning 1-5 m of 51 Eridani b, a 2-10
M planet discovered by the Gemini Planet Imager Exoplanet Survey.
In this study, we present new (1.90-2.19 m) and (2.10-2.40
m) spectra taken with the Gemini Planet Imager as well as an updated
(3.76 m) and new (4.67 m) photometry from the NIRC2 Narrow
camera. The new data were combined with (1.13-1.35 m) and
(1.50-1.80 m) spectra from the discovery epoch with the goal of better
characterizing the planet properties. 51 Eri b photometry is redder than field
brown dwarfs as well as known young T-dwarfs with similar spectral type
(between T4-T8) and we propose that 51 Eri b might be in the process of
undergoing the transition from L-type to T-type. We used two complementary
atmosphere model grids including either deep iron/silicate clouds or
sulfide/salt clouds in the photosphere, spanning a range of cloud properties,
including fully cloudy, cloud free and patchy/intermediate opacity clouds.
Model fits suggest that 51 Eri b has an effective temperature ranging between
605-737 K, a solar metallicity, a surface gravity of (g) = 3.5-4.0 dex,
and the atmosphere requires a patchy cloud atmosphere to model the SED. From
the model atmospheres, we infer a luminosity for the planet of -5.83 to -5.93
(), leaving 51 Eri b in the unique position as being one of
the only directly imaged planet consistent with having formed via cold-start
scenario. Comparisons of the planet SED against warm-start models indicates
that the planet luminosity is best reproduced by a planet formed via core
accretion with a core mass between 15 and 127 M.Comment: 27 pages, 19 figures, Accepted for publication in The Astronomical
Journa
Improving and assessing planet sensitivity of the GPI exoplanet survey with a forward model matched filter
We present a new matched-filter algorithm for direct detection of point sources in the immediate vicinity of bright stars. The stellar point-spread function (PSF) is first subtracted using a Karhunen-Loéve image processing (KLIP) algorithm with angular and spectral differential imaging (ADI and SDI). The KLIP-induced distortion of the astrophysical signal is included in the matched-filter template by computing a forward model of the PSF at every position in the image. To optimize the performance of the algorithm, we conduct extensive planet injection and recovery tests and tune the exoplanet spectra template and KLIP reduction aggressiveness to maximize the signal-to-noise ratio (S/N) of the recovered planets. We show that only two spectral templates are necessary to recover any young Jovian exoplanets with minimal S/N loss. We also developed a complete pipeline for the automated detection of point-source candidates, the calculation of receiver operating characteristics (ROC), contrast curves based on false positives, and completeness contours. We process in a uniform manner more than 330 data sets from the Gemini Planet Imager Exoplanet Survey and assess GPI typical sensitivity as a function of the star and the hypothetical companion spectral type. This work allows for the first time a comparison of different detection algorithms at a survey scale accounting for both planet completeness and false-positive rate. We show that the new forward model matched filter allows the detection of 50% fainter objects than a conventional cross-correlation technique with a Gaussian PSF template for the same false-positive rate.Peer reviewe
Revised Astrometric Calibration of the Gemini Planet Imager
We present a revision to the astrometric calibration of the Gemini Planet
Imager (GPI), an instrument designed to achieve the high contrast at small
angular separations necessary to image substellar and planetary-mass companions
around nearby, young stars. We identified several issues with the GPI Data
Reduction Pipeline (DRP) that significantly affected the determination of angle
of north in reduced GPI images. As well as introducing a small error in
position angle measurements for targets observed at small zenith distances,
this error led to a significant error in the previous astrometric calibration
that has affected all subsequent astrometric measurements. We present a
detailed description of these issues, and how they were corrected. We reduced
GPI observations of calibration binaries taken periodically since the
instrument was commissioned in 2014 using an updated version of the DRP. These
measurements were compared to observations obtained with the NIRC2 instrument
on Keck II, an instrument with an excellent astrometric calibration, allowing
us to derive an updated plate scale and north offset angle for GPI. This
revised astrometric calibration should be used to calibrate all measurements
obtained with GPI for the purposes of precision astrometry.Comment: 36 pages, 17 figures, accepted for publication in the Journal of
Astronomical Telescopes, Instruments, and Systems. Updated version includes
revisions made during the referee proces
An Optical/Near-infrared Investigation of HD 100546 b with the Gemini Planet Imager and MagAO
We present H band spectroscopic and Hα photometric observations of HD 100546 obtained with the Gemini Planet Imager and the Magellan Visible AO camera. We detect H band emission at the location of the protoplanet HD 100546 b, but show that the choice of data processing parameters strongly affects the morphology of this source. It appears point-like in some aggressive reductions, but rejoins an extended disk structure in the majority of the others. Furthermore, we demonstrate that this emission appears stationary on a timescale of 4.6 years, inconsistent at the 2σ level with a Keplerian clockwise orbit at 59 au in the disk plane. The H band spectrum of the emission is inconsistent with any type of low effective temperature object or accreting protoplanetary disk. It strongly suggests a scattered-light origin, as this is consistent with the spectrum of the star and the spectra extracted at other locations in the disk. A non-detection at the 5σ level of HD 100546 b in differential Hα imaging places an upper limit, assuming the protoplanet lies in a gap free of extinction, on the accretion luminosity of 1.7 × 10−4 L ⊙ and for 1 R Jup. These limits are comparable to the accretion luminosity and accretion rate of T-Tauri stars or LkCa 15 b. Taken together, these lines of evidence suggest that the H band source at the location of HD 100546 b is not emitted by a planetary photosphere or an accreting circumplanetary disk but is a disk feature enhanced by the point-spread function subtraction process. This non-detection is consistent with the non-detection in the K band reported in an earlier study but does not exclude the possibility that HD 100546 b is deeply embedded
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
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