Follette, Katherine B.; Rameau, Julien; Dong, Ruobing; Pueyo, Laurent; Close, Laird M.; Duchêne, Gaspard; Fung, Jeffrey; Leonard, Clare; Macintosh, Bruce; Males, Jared R.; et al.(IOP PUBLISHING LTD, 2017-05-19)
We present optical and near-infrared high-contrast images of the transitional disk HD 100546 taken with the Magellan Adaptive Optics system (MagAO) and the Gemini Planet Imager (GPI). GPI data include both polarized intensity and total intensity imagery, and MagAO data are taken in Simultaneous Differential Imaging mode at Ha. The new GPI H-band total intensity data represent a significant enhancement in sensitivity and field rotation compared to previous data sets and enable a detailed exploration of substructure in the disk. The data are processed with a variety of differential imaging techniques (polarized, angular, reference, and simultaneous differential imaging) in an attempt to identify the disk structures that are most consistent across wavelengths, processing techniques, and algorithmic parameters. The inner disk cavity at 15 au is clearly resolved in multiple data sets, as are a variety of spiral features. While the cavity and spiral structures are identified at levels significantly distinct from the neighboring regions of the disk under several algorithms and with a range of algorithmic parameters, emission at the location of HD 100546 "c" varies from point-like under aggressive algorithmic parameters to a smooth continuous structure with conservative parameters, and is consistent with disk emission. Features identified in the HD 100546 disk bear qualitative similarity to computational models of a moderately inclined two-armed spiral disk, where projection effects and wrapping of the spiral arms around the star result in a number of truncated spiral features in forward-modeled images.
Christiansen, Jessie L.; Vanderburg, Andrew; Burt, Jennifer; Fulton, B. J.; Batygin, Konstantin; Benneke, Björn; Brewer, John M.; Charbonneau, David; Ciardi, David R.; Cameron, Andrew Collier; et al.(IOP PUBLISHING LTD, 2017-08-31)
HD 3167 is a bright (V = 8.9), nearby KO star observed by the NASA K2 mission (EPIC 220383386), hosting two small, short-period transiting planets. Here we present the results of a multi-site, multi-instrument radial-velocity campaign to characterize the HD 3167 system. The masses of the transiting planets are 5.02 +/- 0.38 M-circle plus for HD 3167 b, a hot super-Earth with a likely rocky composition (rho(b) = 5.6(-1.43)(+2.15) g cm(-3)), and 9.80(-1.24)(+1.30) M-circle plus for HD 3167 c, a warm sub-Neptune with a likely substantial volatile complement (rho(c) = 1.97(-0.59)(+0.94) g cm(-3)). We explore the possibility of atmospheric composition analysis and determine that planet c is amenable to transmission spectroscopy measurements, and planet b is a potential thermal emission target. We detect a third, non-transiting planet, HD 3167 d, with a period of 8.509 +/- 0.045 d (between planets b and c) and a minimum mass of 6.90 +/- 0.71 M-circle plus. We are able to constrain the mutual inclination of planet d with planets b and c: we rule out mutual inclinations below 1.degrees 3 because we do not observe transits of planet d. From 1.degrees 3 to 40 degrees, there are viewing geometries invoking special nodal configurations, which result in planet d not transiting some fraction of the time.
Millar-Blanchaer, Maxwell A.; Wang, Jason J.; Kalas, Paul; Graham, James R.; Duchêne, Gaspard; Nielsen, Eric L.; Perrin, Marshall; Moon, Dae-Sik; Padgett, Deborah; Metchev, Stanimir A.; et al.(IOP PUBLISHING LTD, 2016-10-20)
We present H-band near-infrared polarimetric imaging observations of the F5V star HD 157587 obtained with the Gemini Planet Imager (GPI) that reveal the debris disk as a bright ring structure at a separation of similar to 80-100 au. The new GPI data complement recent Hubble Space Telescope/STIS observations that show the disk extending out to over 500 au. The GPI image displays a strong asymmetry along the projected minor axis as well as a fainter asymmetry along the projected major axis. We associate the minor and major axis asymmetries with polarized forward scattering and a possible stellocentric offset, respectively. To constrain the disk geometry, we fit two separate disk models to the polarized image, each using a different scattering phase function. Both models favor a disk inclination of similar to 70 degrees and a 1.5 +/- 0.6 au stellar offset in the plane of the sky along the projected major axis of the disk. We find that the stellar offset in the disk plane, perpendicular to the projected major axis is degenerate with the form of the scattering phase function and remains poorly constrained. The disk is not recovered in total intensity due in part to strong adaptive optics residuals, but we recover three point sources. Considering the system's proximity to the galactic plane and the point sources' positions relative to the disk, we consider it likely that they are background objects and unrelated to the disk's offset from the star.
Chilcote, Jeffrey; Pueyo, Laurent; De Rosa, Robert J.; Vargas, Jeffrey; Macintosh, Bruce; Bailey, Vanessa P.; Barman, Travis S.; Bauman, Brian; Bruzzone, Sebastian; Bulger, Joanna; et al.(IOP PUBLISHING LTD, 2017-03-28)
Using the Gemini Planet Imager located at Gemini South, we measured the near-infrared (1.0-2.4 mu m) spectrum of the planetary companion to the nearby, young star beta. Pictoris. We compare the spectrum obtained with currently published model grids and with known substellar objects and present the best matching models as well as the best matching observed objects. Comparing the empirical measurement of the bolometric luminosity to evolutionary models, we find a mass of 12.9. +/- 0.2. M-Jup, an effective temperature of 1724. +/- 15 K, a radius of 1.46. +/- 0.01. R-Jup, and a surface gravity of log g = 4.18. 0.01 [dex] (cgs). The stated uncertainties are statistical errors only, and do not incorporate any uncertainty on the evolutionary models. Using atmospheric models, we find an effective temperature of 1700-1800 K and a surface gravity of log g = 3.5-4.0 [dex] depending upon the model. These values agree well with other publications and with "hot-start" predictions from planetary evolution models. Further, we find that the spectrum of beta Pic. b best matches a low surface gravity L2. +/- 1 brown dwarf. Finally, comparing the spectrum to field brown dwarfs, we find the the spectrum best matches 2MASS J04062677- 381210 and 2MASS J03552337 + 1133437.
We present H band spectroscopic and H alpha 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 2 sigma 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 nondetection at the 5 sigma level of HD 100546 b in differential H alpha imaging places an upper limit, assuming the protoplanet lies in a gap free of extinction, on the accretion luminosity of 1.7 x 10(-4) L-circle dot and M(M) over dot < 6.3 x 10(-7) M-Jup(2) yr(-1) 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.
Wang, Jason J.; Graham, James R.; Pueyo, Laurent; Kalas, Paul; Millar-Blanchaer, Maxwell A.; Ruffio, Jean-Baptiste; De Rosa, Robert J.; Ammons, S. Mark; Arriaga, Pauline; Bailey, Vanessa P.; et al.(IOP PUBLISHING LTD, 2016-10-03)
A principal scientific goal of the Gemini Planet Imager (GPI) is obtaining milliarcsecond astrometry to constrain exoplanet orbits. However, astrometry of directly imaged exoplanets is subject to biases, systematic errors, and speckle noise. Here, we describe an analytical procedure to forward model the signal of an exoplanet that accounts for both the observing strategy (angular and spectral differential imaging) and the data reduction method (Karhunen-Loeve Image Projection algorithm). We use this forward model to measure the position of an exoplanet in a Bayesian framework employing Gaussian processes and Markov-chain Monte Carlo to account for correlated noise. In the case of GPI data on beta Pic b, this technique, which we call Bayesian KLIP-FM Astrometry (BKA), outperforms previous techniques and yields 1 sigma errors at or below the one milliarcsecond level. We validate BKA by fitting a Keplerian orbit to 12 GPI observations along with previous astrometry from other instruments. The statistical properties of the residuals confirm that BKA is accurate and correctly estimates astrometric errors. Our constraints on the orbit of beta Pic b firmly rule out the possibility of a transit of the planet at 10-sigma significance. However, we confirm that the Hill sphere of beta Pic b will transit, giving us a rare chance to probe the circumplanetary environment of a young, evolving exoplanet. We provide an ephemeris for photometric monitoring of the Hill sphere transit event, which will begin at the start of April in 2017 and finish at the end of January in 2018.
Nielsen, Eric L.; Rosa, Robert J. De; Wang, Jason; Rameau, Julien; Song, Inseok; Graham, James R.; Macintosh, Bruce; Ammons, Mark; Bailey, Vanessa P.; Barman, Travis S.; et al.(IOP PUBLISHING LTD, 2016-11-22)
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 (beta Pic) moving group. V343 Normae comprises a K0 and mid-M star in a similar to 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 +/- 0.10M(circle dot) and M-Ab= 0.290 +/- 0.018 M-circle dot. 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.
Johnson-Groh, Mara; Marois, Christian; De Rosa, Robert J.; Nielsen, Eric L.; Rameau, Julien; Blunt, Sarah; Vargas, Jeffrey; Ammons, S. Mark; Bailey, Vanessa P.; Barman, Travis S.; et al.(IOP PUBLISHING LTD, 2017-03-31)
We present new observations of the low-mass companion to HD 984 taken with the Gemini Planet Imager (GPI) as a part of the GPI Exoplanet Survey campaign. Images of HD 984 B were obtained in the J (1.12-1.3 mu m) and H (1.50-1.80 mu m) bands. Combined with archival epochs from 2012 and 2014, we fit the first orbit to the companion to find an 18 au (70-year) orbit with a 68% confidence interval between 14 and 28 au, an eccentricity of 0.18 with a 68% confidence interval between 0.05 and 0.47, and an inclination of 119 degrees with a 68% confidence interval between 114 degrees and 125 degrees. To address the considerable spectral covariance in both spectra, we present a method of splitting the spectra into low and high frequencies to analyze the spectral structure at different spatial frequencies with the proper spectral noise correlation. Using the split spectra, we compare them to known spectral types using field brown dwarf and low-mass star spectra and find a best-fit match of a field gravity M6.5 +/- 1.5 spectral type with a corresponding temperature of 2730(-180)(+120)K. Photometry of the companion yields a luminosity of log(L-bol/L-circle dot) = -2.88 +/- 0.07 dex with DUSTY models. Mass estimates, again from DUSTY models, find an age-dependent mass of 34 +/- 1 to 95 +/- 4 M-Jup. These results are consistent with previous measurements of the object.
Cauley, P. Wilson; Redfield, Seth; Jensen, Adam G.; Barman, Travis S.(IOP PUBLISHING LTD, 2016-06-24)
As followup to our recent detection of a pre-transit signal around HD 189733 b, we obtained full pre-transit phase coverage of a single planetary transit. The pre-transit signal is again detected in the Balmer lines but with variable strength and timing, suggesting that the bow shock geometry reported in our previous work does not describe the signal from the latest transit. We also demonstrate the use of the Ca II H and K residual core flux as a proxy for the stellar activity level throughout the transit. A moderate trend is found between the pre-transit absorption signal in the 2013 data and the Ca II H flux. This suggests that some of the 2013 pre-transit hydrogen absorption can be attributed to varying stellar activity levels. A very weak correlation is found between the Ca II H core flux and the Balmer line absorption in the 2015 transit, hinting at a smaller contribution from stellar activity compared to the 2013 transit. We simulate how varying stellar activity levels can produce changes in the Balmer line transmission spectra. These simulations show that the strength of the 2013 and 2015 pre-transit signals can be reproduced by stellar variability. If the pre-transit signature is attributed to circumplanetary material, its evolution in time can be described by accretion clumps spiraling toward the star, although this interpretation has serious limitations. Further high-cadence monitoring at H alpha is necessary to distinguish between true absorption by transiting material and short-term variations in the stellar activity level.
Rajan, Abhijith; Rameau, Julien; De Rosa, Robert J.; Marley, Mark S.; Graham, James R.; Macintosh, Bruce; Marois, Christian; Morley, Caroline V.; Patience, Jenny; Pueyo, Laurent; et al.(IOP PUBLISHING LTD, 2017-06-16)
We present spectrophotometry spanning 1-5 mu m of 51 Eridani b, a 2-10 M-Jup planet discovered by the Gemini Planet Imager Exoplanet Survey. In this study, we present new K1 (1.90-2.19 mu m) and K2 (2.10-2.40 mu m) spectra taken with the Gemini Planet Imager as well as an updated L-P (3.76 mu m) and new M-S (4.67 mu m) photometry from the NIRC2 Narrow camera. The new data were combined with J (1.13-1.35 mu m) and H (1.50-1.80 mu m) spectra from the discovery epoch with the goal of better characterizing the planet properties. The 51 Eri b photometry is redder than field brown dwarfs as well as known young T-dwarfs with similar spectral type (between T4 and 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. The model fits suggest that 51 Eri. b has an effective temperature ranging between 605 and 737 K, a solar metallicity, and a surface gravity of log(g) = 3.5-4.0 dex, and the atmosphere requires a patchy cloud atmosphere to model the spectral energy distribution (SED). From the model atmospheres, we infer a luminosity for the planet of -5.83 to -5.93 (logL/L circle dot),leaving 51 Eri b in the unique position of being one of the only directly imaged planets consistent with having formed via a cold-start scenario. Comparisons of the planet SED against warm-start models indicate that the planet luminosity is best reproduced by a planet formed via core accretion with a core mass between 15 and 127 M-circle plus.
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