The Gemini Planet Imager Exoplanet Survey: Giant Planet and Brown Dwarf Demographics from 10 to 100 au

We present a statistical analysis of the first 300 stars observed by the Gemini Planet Imager Exoplanet Survey. 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, semimajor axis, and host stellar mass. We uncover a strong correlation between planet occurrence rate and host star mass, with stars M-* > 1.5 M-circle dot more likely to host planets with masses between 2 and 13M(Jup) and semimajor axes of 3-100 au at 99.92% confidence. We fit a double power-law model in planet mass (m) and semimajor axis (a) for planet populations around high-mass stars (M-* > 1.5 M-circle dot) of the form d(2)N/(dm da) proportional to m(alpha) a(beta), finding alpha = -2.4 +/- 0.8 and beta = -2.0 +/- 0.5, and an integrated occurrence rate of 9(-4)(+5)% between 5-13M(Jup )and 10-100 au. A significantly lower occurrence rate is obtained for brown dwarfs around all stars, with 0.81(-0.5)(+0.8)% of stars hosting a brown dwarf companion between 13-80M(Jup) and 10-100 au. Brown dwarfs also appear to be distributed differently in mass and semimajor axis compared to giant planets; whereas giant planets follow a bottom-heavy mass distribution and favor smaller semimajor axes, brown dwarfs exhibit just the opposite behaviors. Comparing to studies of shortperiod giant planets from the radial velocity method, our results are consistent with a peak in occurrence of giant planets between similar to 1 and 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.Office of Science of the U.S. Department of Energy [DE-AC02-05CH11231]; National Science Foundation [ACI-1548562]; Fonds de Recherche du Quebec; California Institute of Technology (Caltech)/Jet Propulsion Laboratory (JPL) - NASA; NASA - Space Telescope Science Institute [51378.01-A]; NASA [NAS5-26555, NNX14AJ80G, NNX15AC89G, NNX15AD95G, NN15AB52l, NNX16AD44G]; NSF [AST-1411868, AST-141378, AST-1518332]; NRAO Student Observing Support Award [SOSPA3-007]; Heising-Simons Foundation 51 Pegasi b postdoctoral fellowship; U.S. Department of Energy by Lawrence Livermore National Laboratory [DE-AC52-07NA27344]; NASA's Science Mission Directorate; Pennsylvania State University; Eberly College of Science; Pennsylvania Space Grant ConsortiumThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Resolving the H-alpha-emitting Region in the Wind of Eta Carinae

The massive evolved star Eta Carinae is the most luminous star in the Milky Way and has the highest steady wind mass-loss rate of any known star. Radiative transfer models of the spectrum by Hillier et al. predict that H-alpha is mostly emitted in regions of the wind at radii of 6 to 60 AU from the star (2.5 to 25 mas at 2.35 kpc). We present diffraction-limited images (FWHM ~25 mas) with Magellan adaptive optics in two epochs, showing that Eta Carinae consistently appears ~2.5 to 3 mas wider in H-alpha emission compared to the adjacent 643 nm continuum. This implies that the H-alpha line-forming region may have a characteristic emitting radius of 12 mas or ~30 AU, in very good agreement with the Hillier stellar-wind model. This provides direct confirmation that the physical wind parameters of that model are roughly correct, including the mass-loss rate of 10^-3 M_sun/yr, plus the clumping factor, and the terminal velocity. Comparison of the H-alpha images (ellipticity and PA) to the continuum images reveals no significant asymmetries at H-alpha. Hence, any asymmetry induced by a companion or by the primary's rotation do not strongly influence the global H-alpha emission in the outer wind.Comment: Published in ApJ

High-contrast imaging in the Hyades with snapshot LOCI

To image faint substellar companions obscured by the stellar halo and speckles, scattered light from the bright primary star must be removed in hardware or software. We apply the "locally-optimized combination of images" (LOCI) algorithm to 1-minute Keck Observatory snapshots of GKM dwarfs in the Hyades using source diversity to determine the most likely PSF. We obtain a mean contrast of 10^{-2} at 0.01", 10^{-4} at <1", and 10^{-5} at 5". New brown dwarf and low-mass stellar companions to Hyades primaries are found in a third of the 84 targeted systems. This campaign shows the efficacy of LOCI on snapshot imaging as well as on bright wide binaries with off-axis LOCI, reaching contrasts sufficient for imaging 625-Myr late-L/early-T dwarfs purely in post-processing.Comment: 12 pages, 12 figures, to appear in SPIE Astronomy 2012, paper 8447-16

The Intricate Structure of HH 508, the Brightest Microjet in the Orion Nebula

We present Magellan adaptive optics H$\alpha$ imaging of HH 508, which has the highest surface brightness among protostellar jets in the Orion Nebula. We find that HH 508 actually has a shorter component to the west, and a longer and knotty component to the east. The east component has a kink at 0.3" from the jet-driving star $\theta^1$ Ori B2, so it may have been deflected by the wind/radiation from the nearby $\theta^1$ Ori B1B5. The origin of both components is unclear, but if each of them is a separate jet, then $\theta^1$ Ori B2 may be a tight binary. Alternatively, HH 508 may be a slow-moving outflow, and each component represents an illuminated cavity wall. The ionization front surrounding $\theta^1$ Ori B2B3 does not directly face $\theta^1$ Ori B1B5, suggesting that the EUV radiation from $\theta^1$ Ori C plays a dominant role in affecting the morphology of proplyds even in the vicinity of $\theta^1$ Ori B1B5. Finally, we report an H$\alpha$ blob that might be ejected by the binary proplyd LV 1.Comment: 4 pages. Published in Ap

The Orbit of the Companion to HD 100453A: Binary-Driven Spiral Arms in a Protoplanetary Disk

HD 100453AB is a 10+/-2 Myr old binary whose protoplanetary disk was recently revealed to host a global two-armed spiral structure. Given the relatively small projected separation of the binary (1.05", or ~108 au), gravitational perturbations by the binary seemed to be a likely driving force behind the formation of the spiral arms. However, the orbit of these stars remained poorly understood, which prevented a proper treatment of the dynamical influence of the companion on the disk. We observed HD 100453AB between 2015-2017 utilizing extreme adaptive optics systems on the Very Large Telescope and Magellan Clay Telescope. We combined the astrometry from these observations with published data to constrain the parameters of the binary's orbit to a=1.06"+/-0.09", e=0.17+/-0.07, and i=32.5+/- 6.5 degrees. We utilized publicly available ALMA CO data to constrain the inclination of the disk to i~28 degrees, which is relatively co-planar with the orbit of the companion and consistent with previous estimates from scattered light images. Finally, we input these constraints into hydrodynamical and radiative transfer simulations to model the structural evolution of the disk. We find that the spiral structure and truncation of the circumprimary disk in HD 100453 are consistent with a companion-dirven origin. Furthermore, we find that the primary star's rotation, its outer disk, and the companion exhibit roughly the same direction of angular momentum, and thus the system likely formed from the same parent body of material.Comment: 28 pages, 11 figures, Accepted to Ap