Showing papers by "James R. Graham published in 2007"

The Gemini Deep Planet Survey

Abstract: We present the results of the Gemini Deep Planet Survey, a near-infrared adaptive optics search for giant planets and brown dwarfs around 85 nearby young stars. The observations were obtained with the Altair adaptive optics system at the Gemini North telescope, and angular differential imaging was used to suppress the speckle noise of the central star. Typically, the observations are sensitive to angular separations beyond 0.5'' with 5 σ contrast sensitivities in magnitude difference at 1.6 μm of 9.5 at 0.5'', 12.9 at 1'', 15.0 at 2'', and 16.5 at 5''. These sensitivities are sufficient to detect planets more massive than 2 MJ with a projected separation in the range 40-200 AU around a typical target. Second-epoch observations of 48 stars with candidates (out of 54) have confirmed that all candidates are unrelated background stars. A detailed statistical analysis of the survey results is presented. Assuming a planet mass distribution dn/dm ∝ m-1.2 and a semimajor-axis distribution dn/da ∝ a-1, the 95% credible upper limits on the fraction of stars with at least one planet of mass 0.5-13 MJ are 0.28 for the range 10-25 AU, 0.13 for 25-50 AU, and 0.093 for 50-250 AU; this result is weakly dependent on the semimajor-axis distribution power-law index. The 95% credible interval for the fraction of stars with at least one brown dwarf companion having a semimajor axis in the range 25-250 AU is 0.019, irrespective of any assumption on the mass and semimajor-axis distributions. The observations made as part of this survey have resolved the stars HD 14802, HD 166181, and HD 213845 into binaries for the first time.

The Gemini Deep Planet Survey -- GDPS

Abstract: We present the results of the Gemini Deep Planet Survey, a near-infrared adaptive optics search for giant planets and brown dwarfs around nearby young stars. The observations were obtained with the Altair adaptive optics system at the Gemini North telescope and angular differential imaging was used to suppress the speckle noise of the central star. Detection limits for the 85 stars observed are presented, along with a list of all faint point sources detected around them. Typically, the observations are sensitive to angular separations beyond 0.5" with 5-sigma contrast sensitivities in magnitude difference at 1.6 micron of 9.5 at 0.5", 12.9 at 1", 15.0 at 2", and 16.5 at 5". For the typical target of the survey, a 100 Myr old K0 star located 22 pc from the Sun, the observations are sensitive enough to detect planets more massive than 2 Mjup with a projected separation in the range 40-200 AU. Second epoch observations of 48 stars with candidates (out of 54) have confirmed that all candidates are unrelated background stars. A detailed statistical analysis of the survey results, yielding upper limits on the fractions of stars with giant planet or low mass brown dwarf companions, is presented. Assuming a planet mass distribution dN/dm m^{-1.2} and a semi-major axis distribution dN/da a^{-1}, the 95% credible upper limits on the fraction of stars with at least one planet of mass 0.5-13 Mjup are 0.28 for the range 10-25 AU, 0.13 for 25-50 AU, and 0.093 for 50-250 AU. The 95% credible interval for the fraction of stars with at least one brown dwarf companion having a semi-major axis in the range 25-250 AU is 0.019 (-0.015/+0.083), irrespective of any assumption on the mass and semi-major axis distributions. The stars HD 14802, HD 166181, and HD 213845 have been resolved into binaries for the first time.

A Population of Faint Extended Line Emitters and the Host Galaxies of Optically Thick QSO Absorption Systems

Abstract: We have conducted a long slit search for low surface brightness Lyman-alpha emitters at redshift 2.67 < z < 3.75. A 92 hour long exposure with VLT/FORS2 down to a 1-sigma surface brightness detection limit of 8x10^-20 erg/cm2/s/sqarcsec yielded a sample of 27 single line emitters with fluxes of a few times 10^-18 erg/s/cm2. We present arguments that most objects are indeed Lyman-alpha. The large comoving number density, the large covering factor, dN/dz ~ 0.2-1, and the often extended Lyman-alpha emission suggest that the emitters be identified with the elusive host population of damped Lyman-alpha systems (DLAS) and high column density Lyman limit systems. A small inferred star formation rate, perhaps supplanted by cooling radiation, appears to energetically dominate the Lyman-alpha emission, and is consistent with the low metallicity, low dust content, and theoretically inferred low masses of DLAS, and with the relative lack of success of earlier searches for their optical counterparts. (abridged)

The Signature of Primordial Grain Growth in the Polarized Light of the AU Microscopii Debris Disk

Abstract: We have used the Hubble Space Telescope Advanced Camera for Surveys coronagraph to make the first polarization maps of the AU Microscopii debris disk. The polarization rises from 5% at 20 AU to 40% at 80 AU. The polarization is perpendicular to the disk, indicating that the scattered light originates from micron-sized grains in an optically thin disk. Disk models show that interior to the ‘‘birth ring’’ (40Y50 AU) there is a hole in the dust distribution where micron-sized dust is depleted by a factor of more than 300. The disk is collision dominated, and grains that fall inward due to drag forces undergo a destructive collision. The presence of this hole implies that the localized enhancements in surface brightness that occur at projected radii interior to the birth ring are caused by nonaxisymmetric structures in the outer disk. The grains exhibit strong forward scattering and high polarization. Spherical grains composed of conventional materials cannot reproduce these optical properties. A Mie/MaxwellGarnett analysis demands highly porous (91%Y94%) particles. In the inner solar system, porous particles form in cometary dust, where the sublimation of ices leaves a ‘‘bird’s nest’’ of refractory material. In AU Mic, the grain porosity may be primordial, because the dust birth ring lies beyond the ice sublimation point. The observed porosities span the range of values implied by laboratory studies of particle coagulation by ballistic clustercluster aggregation. To avoid compactification, the upper size limit for the parent bodies is in the decimeter range, in agreement with theoretical predictions based on collisional lifetime arguments. Consequently, AU Mic may exhibit thesignatureoftheprimordialagglomerationprocesswherebyinterstellargrainsfirstassembledtoformmacroscopic objects. Subject headingg circumstellar matter — dust, extinction — planetary systems: formation — polarization — stars: individual (AU Mic, GJ 803)

Evidence for a Long-standing Top-heavy Initial Mass Function in the Central Parsec of the Galaxy

Abstract: We classify 329 late-type giants within 1 pc of Sgr A*, using the adaptive optics integral field spectrometer SINFONI on the VLT. These observations represent the deepest spectroscopic data set so far obtained for the Galactic center, reaching a 50% completeness threshold at the approximate magnitude of the helium-burning red clump (KS ~ 15.5 mag). Combining our spectroscopic results with NaCo H and KS photometry, we construct an observed Hertzsprung-Russell diagram, which we quantitatively compare to theoretical distributions of various star formation histories of the inner Galaxy, using a χ2 analysis. Our best-fit model corresponds to continuous star formation over the last 12 Gyr with a top-heavy initial mass function (IMF). The similarity of this IMF to the IMF observed for the most recent epoch of star formation is intriguing and perhaps suggests a connection between recent star formation and the stars formed throughout the history of the Galactic center.

Evidence for a Long-Standing Top-Heavy IMF in the Central Parsec of the Galaxy

Abstract: We classify 329 late-type giants within 1 parsec of Sgr A*, using the adaptive optics integral field spectrometer SINFONI on the VLT. These observations represent the deepest spectroscopic data set so far obtained for the Galactic Center, reaching a 50% completeness threshold at the approximate magnitude of the helium-burning red clump (Ks ~ 15.5 mag.). Combining our spectroscopic results with NaCo H and Ks photometry, we construct an observed Hertzsprung-Russell diagram, which we quantitatively compare to theoretical distributions of various star formation histories of the inner Galaxy, using a chi-squared analysis. Our best-fit model corresponds to continuous star formation over the last 12 Gyr with a top-heavy initial mass function (IMF). The similarity of this IMF to the IMF observed for the most recent epoch of star formation is intriguing and perhaps suggests a connection between recent star formation and the stars formed throughout the history of the Galactic Center.

Discovery of Extreme Asymmetry in the Debris Disk Surrounding HD 15115

Abstract: We report the first scattered light detection of a dusty debris disk surrounding the F2 V star HD 15115 using the Hubble Space Telescope in the optical and Keck adaptive optics in the near-infrared. The most remarkable property of the HD 15115 disk relative to other debris disks is its extreme length asymmetry. The east side of the disk is detected to ~315 AU radius, whereas the west side of the disk has radius >550 AU. We find a blue optical to near-infrared scattered light color relative to the star that indicates grain scattering properties similar to the AU Mic debris disk. The existence of a large debris disk surrounding HD 15115 adds further evidence for membership in the β Pic moving group, which was previously argued based on kinematics alone. Here we hypothesize that the extreme disk asymmetry is due to dynamical perturbations from HIP 12545, an M star east of HD 15115 that shares a common proper motion vector, heliocentric distance, galactic space velocity, and age.

Discovery of an Extended Debris Disk around the F2 V Star HD 15745

Abstract: Using the Advanced Camera for Surveys aboard the Hubble Space Telescope, we have discovered dust-scattered light from the debris disk surrounding the F2 V star HD 15745. The circumstellar disk is detected between 2.0 and 7.5 radius, corresponding to 128–480 AU radius. The circumstellar disk morphology is asymmetric about the star, resembling a fan, and consistent with forward scattering grains in an optically thin disk with an inclination of ∼67 to our line of sight. The spectral energy distribution and scattered light morphology can be approximated with a model disk composed of silicate grains between 60 and 450 AU radius, with a total dust mass of 10 7 M, (0.03 M), representing a narrow grain size distribution (1–10 mm). Galactic space motions are similar to the Castor moving group, with an age of ∼10 8 yr, although future work is required to determine the age of HD 15745 using other indicators. Subject headings: circumstellar matter — stars: individual (HD 15745)

A ring of warm dust in the hd 32297 debris disk

Abstract: We report the detection of a ring of warm dust in the near-edge-on disk surrounding HD 32297 with the Gemini NorthMichellemid-infraredimager.OurN 0 -bandimageshowselongatedstructureconsistentwiththeorientationof the scattered-lightdisk.TheF! (11:2 " m) ! 49:9 " 2:1mJyfluxissignificantly abovethe28:2 " 0:6mJyphotosphere. Subtraction of the stellar point-spread function reveals a bilobed structure with peaks 0.5 00 Y0.6 00 from the star. The disk is detected out to the sensitivity limit at # 1 00 , and the flux in each lobe is symmetric to within 10%. An analysis of the stellar component of the spectral energy distribution (SED) suggests a spectral type later than A0, in contrast tocommonlycitedliteraturevalues.Wefitthree-dimensional,single-sizegrainmodelsof anopticallythindustringto our image and the SED using a Markov chain Monte Carlo algorithm in a Bayesian framework. The best-fit effective grain sizesare submicron, suggesting the samedust population isresponsible for the bulk of the scattered light. The innerboundaryofthewarmdustislocated0.5 00 Y0.7 00 (# 65AU)fromthestar,whichisapproximatelycospatialwiththe outerboundaryofthe scattered-light asymmetryinwardof 0.5 00 . Theadditionof aseparatecomponent of larger,cooler grainsthatprovideaportionof the60" mfluximprovesboththefidelityof themodelfitandconsistencywiththeslopes of the scattered-light brightness profiles. The peak vertical optical depths in our models [# (0:3Y1) ; 10 $ 2 ] imply that grain-grain collisions likely play a significant role in dust dynamics and evolution. Submicron grains can survive radiationpressureblowoutif theyareicyandporous.Similarly,theinferredwarmtemperatures(130Y200K)suggest that ice sublimation may play a role in truncating the inner disk. Subject headingg circumstellar matter — infrared: stars — planetary systems: protoplanetary disks — stars: formation — stars: individual (HD 32297)

Discovery of an extended debris disk around the F2V star HD 15745

Abstract: Using the Advanced Camera for Surveys aboard the Hubble Space Telescope, we have discovered dust-scattered light from the debris disk surrounding the F2V star HD 15745. The circumstellar disk is detected between 2.0" and 7.5" radius, corresponding to 128 - 480 AU radius. The circumstellar disk morphology is asymmetric about the star, resembling a fan, and consistent with forward scattering grains in an optically thin disk with an inclination of ~67 degrees to our line of sight. The spectral energy distribution and scattered light morphology can be approximated with a model disk composed of silicate grains between 60 and 450 AU radius, with a total dust mass of 10E-7 M_sun (0.03 M_earth) representing a narrow grain size distribution (1 - 10 micron). Galactic space motions are similar to the Castor Moving Group with an age of ~10E+8 yr, although future work is required to determine the age of HD 15745 using other indicators.

Imaging of the Stellar Population of IC10 with Laser Guide Star Adaptive Optics and the Hubble Space Telescope

Abstract: We present adaptive optics (AO) images of the central starburst region of the dwarf irregular galaxy IC10. The Keck 2 telescope laser guide star was used to achieve near diffraction-limited performance at H and K' (Strehls of 18% and 32%, respectively). The images are centered on the putative Wolf-Rayet (W-R) object [MAC92]24. We combine our AO images with F814W data from HST. By comparing the K' vs. [F814W]-K' color-magnitude diagram (CMD) with theoretical isochrones, we find that the stellar population is best represented by at least two bursts of star formation, one ~ 10 Myr ago and one much older (150-500 Myr). Young, blue stars are concentrated in the vicinity of [MAC92]24. This population represents an OB association with a half-light radius of about 3 pc. We resolve the W-R object [MAC92]24 into at least six blue stars. Four of these components have near-IR colors and luminosities that make them robust WN star candidates. By matching the location of C-stars in the CMD with those in the SMC we derive a distance modulus for IC10 of about 24.5 mag. and a foreground reddening of E(B-V) = 0.95. We find a more precise distance by locating the tip of the giant branch in the F814W, H, and K' luminosity functions. We find a weighted mean distance modulus of 24.48 +/- 0.08. The systematic error in this measurement, due to a possible difference in the properties of the RGB populations in IC10 and the SMC, is +/- 0.16 mag.

Imaging of the Stellar Population of IC 10 with Laser Guide Star Adaptive Optics and the Hubble Space Telescope

Abstract: We present adaptive optics (AO) images of the central starburst region of the dwarf irregular galaxy IC 10. The Keck II telescope laser guide star was used to achieve near diffraction-limited performance at H and K' (Strehl ratios of 18% and 32%, respectively). The images are centered on the putative Wolf-Rayet (W-R) object [MAC92]24. We combine our AO images with F814W data from HST. By comparing the K' versus [F814W] - K' color-magnitude diagram (CMD) with theoretical isochrones, we find that the stellar population is best represented by at least two bursts of star formation, one ~10 Myr ago and one much older (150-500 Myr). Young, blue stars are concentrated in the vicinity of [MAC92]24. This population represents an OB association with a half-light radius of about 3 pc. We resolve the W-R object [MAC92] 24 into at least six blue stars. Four of these components have near-IR colors and luminosities that make them robust WN star candidates. By matching the location of C stars in the CMD with those in the SMC we derive a distance modulus for IC 10 of about 24.5 mag and a foreground reddening of E(B - V) = 0.95 mag. We find a more precise distance by locating the tip of the giant branch in the F814W, H, and K' luminosity functions. We find a weighted mean distance modulus of 24.48 ± 0.08. The systematic error in this measurement, due to a possible difference in the properties of the RGB populations in IC 10 and the SMC, is ±0.16 mag.

A Ring of Warm Dust in the HD 32297 Debris Disk

Abstract: We report the detection of a ring of warm dust in the edge-on disk surrounding HD 32297 with the Gemini-N/MICHELLE mid-infrared imager. Our N'-band image shows elongated structure consistent with the orientation of the scattered-light disk. The Fnu(11.2 um) = 49.9+/-2.1 mJy flux is significantly above the 28.2+/-0.6 mJy photosphere. Subtraction of the stellar point spread function reveals a bilobed structure with peaks 0.5"-0.6" from the star. An analysis of the stellar component of the SED suggests a spectral type later than A0, in contrast to commonly cited literature values. We fit three-dimensional, single-size grain models of an optically thin dust ring to our image and the SED using a Markov chain Monte Carlo algorithm in a Bayesian framework. The best-fit effective grain sizes are submicron, suggesting the same dust population is responsible for the bulk of the scattered light. The inner boundary of the warm dust is located 0.5"-0.7" (~65 AU) from the star, which is approximately cospatial with the outer boundary of the scattered-light asymmetry inward of 0.5". The addition of a separate component of larger, cooler grains that provide a portion of the 60 um flux improves both the fidelity of the model fit and consistency with the slopes of the scattered-light brightness profiles. Previous indirect estimates of the stellar age (~30 Myr) indicate the dust is composed of debris. The peak vertical optical depths in our models (~0.3-1 x 1e-2) imply that grain-grain collisions likely play a significant role in dust dynamics and evolution. Submicron grains can survive radiation pressure blow-out if they are icy and porous. Similarly, the inferred warm temperatures (130-200 K) suggest that ice sublimation may play a role in truncating the inner disk.

Ground-Based Direct Detection of Exoplanets with the Gemini Planet Imager (GPI)

Abstract: The Gemini Planet (GPI) imager is an "extreme" adaptive optics system being designed and built for the Gemini Observatory GPI combines precise and accurate wavefront control, diffraction suppression, and a speckle-suppressing science camera with integral field and polarimetry capabilities GPI's primary science goal is the direct detection and characterization of young, Jovian-mass exoplanets For systems younger than 2 Gyr exoplanets more massive than 6 MJ and semimajor axes beyond 10 AU are detected with completeness greater than 50% GPI will also discover faint debris disks, explore icy moons and minor planets in the solar system, reveal high dynamic range main-sequence binaries, and study mass loss from evolved stars This white paper explains the role of GPI in exoplanet discovery and characterization and summarizes our recommendations to the NSF-NASA-DOE Astronomy and Astrophysics Advisory Committee ExoPlanet Task Force

Laser Guide Star Adaptive Optics Integral Field Spectroscopy of a Tightly Collimated Bipolar Jet from the Herbig Ae Star LkHα 233

Abstract: We have used the integral field spectrograph OSIRIS and laser guide star adaptive optics at Keck Observatory to obtain high angular resolution (0.06''), moderate spectral resolution (R 3800) images of the bipolar jet from the Herbig Ae star LkHα 233, seen in near-IR [Fe II] emission at 1.600 and 1.644 μm. This jet is narrow and tightly collimated, with an opening angle of only 9°, and has an average radial velocity of ~100 km s-1. The jet and counterjet are asymmetric, with the redshifted jet much clumpier than its counterpart at the angular resolution of our observations. The observed properties are in general similar to jets seen around T Tauri stars, although it has a relatively large mass flux of 1.2 ± 0.3 × 10-7 M☉ yr-1, near the high end of the observed mass flux range around T Tauri stars. We also spatially resolve an inclined circumstellar disk around LkHα 233, which obscures the star from direct view. By comparison with numerical radiative transfer disk models, we estimate the disk midplane to be inclined i = 65° ± 5° relative to the plane of the sky. Since the star is seen only in scattered light at near-infrared wavelengths, we detect only a small fraction of its intrinsic flux. Because previous estimates of its stellar properties did not account for this, either LkHa 233 must be located closer than previously believed, or its true luminosity must be greater than previously supposed, consistent with its being a ~4 M☉ star near the stellar birth line.

Laser Guide Star Adaptive Optics Integral Field Spectroscopy of a Tightly Collimated Bipolar Jet from the Herbig Ae star LkHa 233

Abstract: We have used the integral field spectrograph OSIRIS and laser guide star adaptive optics at Keck Observatory to obtain high angular resolution (0.06"), moderate spectral resolution (R ~ 3800) images of the bipolar jet from the Herbig Ae star LkHa 233, seen in near-IR [Fe II] emission at 1.600 & 1.644 microns. This jet is narrow and tightly collimated, with an opening angle of only 9 degrees, and has an average radial velocity of ~ 100 km/s. The jet and counterjet are asymmetric, with the red-shifted jet much clumpier than its counterpart at the angular resolution of our observations. The observed properties are in general similar to jets seen around T Tauri stars, though it has a relatively large mass flux of (1.2e-7 +- 0.3e-7) M_sun/year, near the high end of the observed mass flux range around T Tauri stars. We also spatially resolve an inclined circumstellar disk around LkHa 233, which obscures the star from direct view. By comparison with numerical radiative transfer disk models, we estimate the disk midplane to be inclined i = 65 +- 5 degrees relative to the plane of the sky. Since the star is seen only in scattered light at near-infrared wavelengths, we detect only a small fraction of its intrinsic flux. Because previous estimates of its stellar properties did not account for this, either LkHa 233 must be located closer than the previously believed, or its true luminosity must be greater than previously supposed, consistent with its being a ~4 M_sun star near the stellar birthline.

The Molecular Gas Environment around Two Herbig Ae/Be Stars: Resolving the Outflows of LkHα 198 and LkHα 225S

Abstract: Observations of outflows associated with preYmain-sequence stars reveal details about morphology, binarity, and evolutionary states of young stellar objects. We present molecular line data from the Berkeley-Illinois-Maryland Associationarray and Five Colleges RadioAstronomicalObservatory toward the regions containingthe Herbig Ae/Be stars LkH! 198 and LkH! 225S. Single-dish observations of 12 CO J ! 1 " 0, 13 CO J ! 1 " 0, N2H + J ! 1 " 0, and CS J ! 2 " 1 were made over a field of 4:3 0 ;4:3 0 for each species. 12 CO J ! 1 " 0 data from FCRAO were combined with high-resolution BIMA array data to achieve a naturally weighted synthesized beam of 6:75 00 ;5:5 00 toward LkH! 198 and 5:7 00 ; 3:95 00 toward LkH! 225S, representing resolution improvements of factors of approximately 10 and 5 over existing data. By using uniform weighting, we achieved another factor of 2 improvement. The outflow around LkH! 198 resolves into at least four outflows, none of which are centered on LkH! 198-IR, but even at our resolution we cannot exclude the possibility of an outflow associated with this source. In the LkH! 225S region we find evidence for two outflows associated with LkH! 225S itself, and a third outflow is likely driven by this source. Identification of the driving sources is still resolution limited and is also complicated by the presence of three clouds along the line of sight toward the Cygnus molecular cloud. 13 CO J ! 1 " 0 is present in the environmentsof bothstars alongwith cold,densegas as traced byCSJ ! 2 " 1 and (inLkH! 225S) N2H + J ! 1 " 0. No 2.6 mm continuum is detected in either region in relatively shallow maps compared to existing continuum observations. Subject headingg ISM: clouds — ISM: individual (LkH! 198, LkH! 225S) — ISM: molecules — stars: formation

The Molecular Gas Environment around Two Herbig Ae/Be Stars: Resolving the Outflows of LkHa 198 and LkHa 225S

Abstract: Observations of outflows associated with pre-main-sequence stars reveal details about morphology, binarity and evolutionary states of young stellar objects. We present molecular line data from the Berkeley-Illinois-Maryland Association array and Five Colleges Radio Astronomical Observatory toward the regions containing the Herbig Ae/Be stars LkHa 198 and LkHa 225S. Single dish observations of 12CO 1-0, 13CO 1-0, N2H+ 1-0 and CS 2-1 were made over a field of 4.3' x 4.3' for each species. 12CO data from FCRAO were combined with high resolution BIMA array data to achieve a naturally-weighted synthesized beam of 6.75'' x 5.5'' toward LkHa 198 and 5.7'' x 3.95'' toward LkHa 225S, representing resolution improvements of factors of approximately 10 and 5 over existing data. By using uniform weighting, we achieved another factor of two improvement. The outflow around LkHa 198 resolves into at least four outflows, none of which are centered on LkHa 198-IR, but even at our resolution, we cannot exclude the possibility of an outflow associated with this source. In the LkHa 225S region, we find evidence for two outflows associated with LkHa 225S itself and a third outflow is likely driven by this source. Identification of the driving sources is still resolution-limited and is also complicated by the presence of three clouds along the line of sight toward the Cygnus molecular cloud. 13CO is present in the environments of both stars along with cold, dense gas as traced by CS and (in LkHa 225S) N2H+. No 2.6 mm continuum is detected in either region in relatively shallow maps compared to existing continuum observations.

Discovery of extreme asymmetry in the debris disk surrounding HD 15115

Abstract: We report the first scattered light detection of a dusty debris disk surrounding the F2V star HD 15115 using the Hubble Space Telescope in the optical, and Keck adaptive optics in the near-infrared. The most remarkable property of the HD 15115 disk relative to other debris disks is its extreme length asymmetry. The east side of the disk is detected to ~315 AU radius, whereas the west side of the disk has radius >550 AU. We find a blue optical to near-infrared scattered light color relative to the star that indicates grain scattering properties similar to the AU Mic debris disk. The existence of a large debris disk surrounding HD 15115 adds further evidence for membership in the Beta Pic moving group, which was previously argued based on kinematics alone. Here we hypothesize that the extreme disk asymmetry is due to dynamical perturbations from HIP 12545, an M star 0.5 degrees (0.38 pc) east of HD 15115 that shares a common proper motion vector, heliocentric distance, galactic space velocity, and age.

Ground-Based Direct Detection of Exoplanets with the Gemini Planet Imager (GPI)

Abstract: The Gemini Planet (GPI) imager is an “extreme” adaptive optics system being designed and built for the Gemini Observatory. GPI combines precise and accurate wavefront control, diffraction suppression, and a speckle-suppressing science camera with integral field and polarimetry capabilities. GPI’s primary science goal is the direct detection and characterization of young, Jovian-mass exoplanets. For systems younger than 2 Gyr exoplanets more massive than 6 MJ and semimajor axes beyond 10 AU are detected with completeness greater than 50%. GPI will also discover faint debris disks, explore icy moons and minor planets in the solar system, reveal high dynamic range mainsequence binaries, and study mass loss from evolved stars. This white paper explains the role of GPI in exoplanet discovery and characterization and summarizes our recommendations to the NSF-NASA-DOE Astronomy and Astrophysics Advisory Committee ExoPlanet Task Force. 1 UC Berkeley 2 Lawrence Livermore National Lab 3 Universite de Montreal 4 UC Santa Cruz 5 UCLA 6 JPL 7 American Museum of Natural History 8 NRC/Herzberg Institute