Hilo, HI, United States
Hilo, HI, United States

Time filter

Source Type

Chun M.R.,University of Hawaii at Hilo | Lai O.,Gemini Observatory | Butterley T.,Durham University | Goebel S.,University of Hawaii at Hilo | And 2 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

We present high resolution optical turbulence profiles of the dome and ground-layers measured using a set of Shack- Hartmann wavefront sensors deployed over a field of view of between 0.5 and 1.0 degrees at the focal planes of the University of Hawaii 2.2-m telescope and the Canada-France-Hawaii Telescope on Maunakea, Hawaii. Observations with the experiment were made over the course of several nights on each telescope. We obtain estimates of the strength, distribution, and velocities of optical turbulence from the covariance matrices and maps of the measured wavefront gradients and a decomposition of the measured wavefronts into Zernike polynomials. We find agreement with previous measurements on Maunakea that the ground layer is largely confined within the first tens of meters above the ground and moves at the ground wind velocity. In addition, we spatially resolve the optical turbulence that arises from within the dome. For both facilities we find that the dome seeing is a major component of the overall turbulence strength accounting for more than half of the turbulence within the ground layer and that the dome seeing changes very slowly with a characteristic frequency of less than 1 Hz. While the variety of observing conditions sampled is low, we find that the characteristics of the dome seeing with observation elevation angle and the azimuth angle with respect to the ground wind are quite different on the two telescopes suggesting a different origin to the seeing within the two enclosures. © 2014 SPIE.


Nielsen E.L.,University of Hawaii at Manoa | Liu M.C.,University of Hawaii at Manoa | Wahhaj Z.,University of Hawaii at Manoa | Biller B.A.,Max Planck Institute for Astronomy | And 21 more authors.
Astrophysical Journal | Year: 2012

We report the discovery of two low-mass companions to the young A0V star HD1160 at projected separations of 81 ± 5AU (HD1160B) and 533 ± 25AU (HD1160C) by the Gemini NICI Planet-Finding Campaign. Very Large Telescope images of the system taken over a decade for the purpose of using HD1160A as a photometric calibrator confirm that both companions are physically associated. By comparing the system to members of young moving groups and open clusters with well-established ages, we estimate an age of 50+50 -40Myr for HD1160 ABC. While the UVW motion of the system does not match any known moving group, the small magnitude of the space velocity is consistent with youth. Near-IR spectroscopy shows HD1160C to be an M3.5 ± 0.5 star with an estimated mass of 0.22+0.03 -0.04 M⊙, while NIR photometry of HD1160B suggests a brown dwarf with a mass of 33 +12 -9 M Jup. The very small mass ratio (0.014) between the A and B components of the system is rare for A star binaries, and would represent a planetary-mass companion were HD1160A to be slightly less massive than the Sun. © 2012 The American Astronomical Society. All rights reserved.


Biller B.A.,Max Planck Institute for Astronomy | Liu M.C.,University of Hawaii at Manoa | Wahhaj Z.,University of Hawaii at Manoa | Nielsen E.L.,University of Hawaii at Manoa | And 17 more authors.
Astrophysical Journal | Year: 2013

We report results of a direct imaging survey for giant planets around 80 members of the β Pic, TW Hya, Tucana-Horologium, AB Dor, and Hercules-Lyra moving groups, observed as part of the Gemini/NICI Planet-Finding Campaign. For this sample, we obtained median contrasts of ΔH = 13.9 mag at 1″ in combined CH4 narrowband ADI+SDI mode and median contrasts of ΔH = 15.1 mag at 2″ in H-band ADI mode. We found numerous (>70) candidate companions in our survey images. Some of these candidates were rejected as common-proper motion companions using archival data; we reobserved with Near-Infrared Coronagraphic Imager (NICI) all other candidates that lay within 400 AU of the star and were not in dense stellar fields. The vast majority of candidate companions were confirmed as background objects from archival observations and/or dedicated NICI Campaign followup. Four co-moving companions of brown dwarf or stellar mass were discovered in this moving group sample: PZ Tel B (36 ± 6 M Jup, 16.4 ± 1.0 AU), CD-35 2722B (31 ± 8 M Jup, 67 ± 4 AU), HD 12894B (0.46 ± 0.08 M , 15.7 ± 1.0 AU), and BD+07 1919C (0.20 ± 0.03 M , 12.5 ± 1.4 AU). From a Bayesian analysis of the achieved H band ADI and ASDI contrasts, using power-law models of planet distributions and hot-start evolutionary models, we restrict the frequency of 1-20 M Jup companions at semi-major axes from 10-150 AU to <18% at a 95.4% confidence level using DUSTY models and to <6% at a 95.4% using COND models. Our results strongly constrain the frequency of planets within semi-major axes of 50 AU as well. We restrict the frequency of 1-20 M Jup companions at semi-major axes from 10-50 AU to <21% at a 95.4% confidence level using DUSTY models and to <7% at a 95.4% using COND models. This survey is the deepest search to date for giant planets around young moving group stars. © 2013. The American Astronomical Society. All rights reserved..


Nielsen E.L.,University of Hawaii at Manoa | Liu M.C.,University of Hawaii at Manoa | Wahhaj Z.,European Southern Observatory | Biller B.A.,Max Planck Institute for Astronomy | And 21 more authors.
Astrophysical Journal | Year: 2013

We have carried out high contrast imaging of 70 young, nearby B and A stars to search for brown dwarf and planetary companions as part of the Gemini NICI Planet-Finding Campaign. Our survey represents the largest, deepest survey for planets around high-mass stars (1.5-2.5 M⊙) conducted to date and includes the planet hosts β Pic and Fomalhaut. We obtained follow-up astrometry of all candidate companions within 400 AU projected separation for stars in uncrowded fields and identified new low-mass companions to HD 1160 and HIP 79797. We have found that the previously known young brown dwarf companion to HIP 79797 is itself a tight (3 AU) binary, composed of brown dwarfs with masses 58 M⊙Jup and 55 M⊙Jup, making this system one of the rare substellar binaries in orbit around a star. Considering the contrast limits of our NICI data and the fact that we did not detect any planets, we use high-fidelity Monte Carlo simulations to show that fewer than 20% of 2 M⊙ stars can have giant planets greater than 4 M ⊙Jup between 59 and 460 AU at 95% confidence, and fewer than 10% of these stars can have a planet more massive than 10 M⊙Jup between 38 and 650 AU. Overall, we find that large-separation giant planets are not common around B and A stars: fewer than 10% of B and A stars can have an analog to the HR 8799 b (7 M⊙Jup, 68 AU) planet at 95% confidence. We also describe a new Bayesian technique for determining the ages of field B and A stars from photometry and theoretical isochrones. Our method produces more plausible ages for high-mass stars than previous age-dating techniques, which tend to underestimate stellar ages and their uncertainties. © 2013. The American Astronomical Society. All rights reserved..


Wahhaj Z.,European Southern Observatory | Liu M.C.,University of Hawaii at Manoa | Nielsen E.L.,University of Hawaii at Manoa | Biller B.A.,Max Planck Institute for Astronomy | And 17 more authors.
Astrophysical Journal | Year: 2013

We have completed a high-contrast direct imaging survey for giant planets around 57 debris disk stars as part of the Gemini NICI Planet-Finding Campaign. We achieved median H-band contrasts of 12.4 mag at 0.″5 and 14.1 mag at 1″ separation. Follow-up observations of the 66 candidates with projected separation <500 AU show that all of them are background objects. To establish statistical constraints on the underlying giant planet population based on our imaging data, we have developed a new Bayesian formalism that incorporates (1) non-detections, (2) single-epoch candidates, (3) astrometric and (4) photometric information, and (5) the possibility of multiple planets per star to constrain the planet population. Our formalism allows us to include in our analysis the previously known β Pictoris and the HR 8799 planets. Our results show at 95% confidence that <13% of debris disk stars have a ≥5 M Jup planet beyond 80 AU, and <21% of debris disk stars have a ≥3 M Jup planet outside of 40 AU, based on hot-start evolutionary models. We model the population of directly imaged planets as d 2 N/dMdam α a β, where m is planet mass and a is orbital semi-major axis (with a maximum value of a max). We find that β < -0.8 and/or α > 1.7. Likewise, we find that β < -0.8 and/or a max < 200 AU. For the case where the planet frequency rises sharply with mass (α > 1.7), this occurs because all the planets detected to date have masses above 5 M Jup, but planets of lower mass could easily have been detected by our search. If we ignore the β Pic and HR 8799 planets (should they belong to a rare and distinct group), we find that <20% of debris disk stars have a ≥3 M Jup planet beyond 10 AU, and β < -0.8 and/or α < -1.5. Likewise, β < -0.8 and/or a max < 125 AU. Our Bayesian constraints are not strong enough to reveal any dependence of the planet frequency on stellar host mass. Studies of transition disks have suggested that about 20% of stars are undergoing planet formation; our non-detections at large separations show that planets with orbital separation >40 AU and planet masses >3 M Jup do not carve the central holes in these disks. © 2013. The American Astronomical Society. All rights reserved.


Nielsen E.L.,University of Hawaii at Manoa | Liu M.C.,University of Hawaii at Manoa | Wahhaj Z.,European Southern Observatory | Biller B.A.,University of Edinburgh | And 11 more authors.
Astrophysical Journal | Year: 2014

We present new astrometry for the young (12-21 Myr) exoplanet β Pictoris b taken with the Gemini/NICI and Magellan/MagAO instruments between 2009 and 2012. The high dynamic range of our observations allows us to measure the relative position of β Pic b with respect to its primary star with greater accuracy than previous observations. Based on a Markov Chain Monte Carlo analysis, we find the planet has an orbital semi-major axis of 9.1 AU and orbital eccentricity <0.15 at 68% confidence (with 95% confidence intervals of 8.2-48 AU and 0.00-0.82 for semi-major axis and eccentricity, respectively, due to a long narrow degenerate tail between the two). We find that the planet has reached its maximum projected elongation, enabling higher precision determination of the orbital parameters than previously possible, and that the planet's projected separation is currently decreasing. With unsaturated data of the entire β Pic system (primary star, planet, and disk) obtained thanks to NICI's semi-transparent focal plane mask, we are able to tightly constrain the relative orientation of the circumstellar components. We find the orbital plane of the planet lies between the inner and outer disks: the position angle (P.A.) of nodes for the planet's orbit (211.8 ± 0.°3) is 7.4σ greater than the P.A. of the spine of the outer disk and 3.2σ less than the warped inner disk P.A., indicating the disk is not collisionally relaxed. Finally, for the first time we are able to dynamically constrain the mass of the primary star β Pic to 1.76 M . © 2014. The American Astronomical Society. All rights reserved..


Wahhaj Z.,European Southern Observatory | Liu M.C.,University of Hawaii at Manoa | Biller B.A.,University of Edinburgh | Nielsen E.L.,University of Hawaii at Manoa | And 6 more authors.
Astronomy and Astrophysics | Year: 2014

We present J,H, CH4 short (1.578 μm), CH4 long (1.652 μm) and Ks-band images of the dust ring around the 10 Myr old star HR 4796 A obtained using the Near Infrared Coronagraphic Imager (NICI) on the Gemini-South 8.1 m Telescope. Our images clearly show for the first time the position of the star relative to its circumstellar ring thanks to NICI's translucent focal plane occulting mask. We employ a Bayesian Markov chain Monte Carlo method to constrain the offset vector between the two. The resulting probability distribution shows that the ring center is offset from the star by 16.7 ± 1.3 milliarcseconds along a position angle of 26 ± 3°, along the PA of the ring, 26.47 ± 0.04°. We find that the size of this offset is not large enough to explain the brightness asymmetry of the ring. The ring is measured to have mostly red reflectivity across the JHKs filters, which seems to indicate micron-sized grains. Just like Neptune's 3:2 and 2:1 mean-motion resonances delineate the inner and outer edges of the classical Kuiper belt, we find that the radial extent of the HR 4796 A and the Fomalhaut rings could correspond to the 3:2 and 2:1 mean-motion resonances of hypothetical planets at 54.7 AU and 97.7 AU in the two systems, respectively. A planet orbiting HR 4796 A at 54.7 AU would have to be less massive than 1.6 MJup so as not to widen the ring too much by stirring. © ESO, 2014.


Hayward T.L.,Gemini Observatory | Biller B.A.,University of Edinburgh | Biller B.A.,Max Planck Institute for Astronomy | Liu M.C.,University of Hawaii at Manoa | And 6 more authors.
Publications of the Astronomical Society of the Pacific | Year: 2014

We describe the astrometric calibration of the Gemini NICI Planet-Finding Campaign. The Campaign requires a relative astrometric accuracy of ≈20 mas across multiyear timescales in order to distinguish true companions from background stars by verifying common proper motion and parallax with their parent stars. The calibration consists of a correction for instrumental optical image distortion, plus on-sky imaging of astrometric fields to determine the pixel scale and image orientation. We achieve an accuracy of ≲7 mas between the center and edge of the 18″ NICI field, meeting the 20 mas requirement. Most of the Campaign data in the Gemini Science Archive are accurate to this level but we identify a number of anomalies and present methods to correct the errors. © 2014. The Astronomical Society of the Pacific. All rights reserved. Printed in U.S.A.


Males J.R.,University of Arizona | Close L.M.,University of Arizona | Morzinski K.M.,University of Arizona | Wahhaj Z.,European Southern Observatory | And 21 more authors.
Astrophysical Journal | Year: 2014

We present the first ground-based CCD (λ < 1 μm) image of an extrasolar planet. Using the Magellan Adaptive Optics system's VisAO camera, we detected the extrasolar giant planet β Pictoris b in Y-short (YS , 0.985 μm), at a separation of 0.470 ± 0.″010 and a contrast of (1.63 ± 0.49) × 10-5. This detection has a signal-to-noise ratio of 4.1 with an empirically estimated upper limit on false alarm probability of 1.0%. We also present new photometry from the Gemini Near-Infrared Coronagraphic Imager instrument on the Gemini South telescope, in CH 4S,1% (1.58 μm), KS (2.18 μm), and K cont (2.27 μm). A thorough analysis of our photometry combined with previous measurements yields an estimated near-IR spectral type of L2.5 ± 1.5, consistent with previous estimates. We estimate log (L odot;bol/L odot;) = -3.86 ± 0.04, which is consistent with prior estimates for β Pic b and with field early-L brown dwarfs (BDs). This yields a hot-start mass estimate of 11.9 ± 0.7 M odot;Jup for an age of 21 ± 4 Myr, with an upper limit below the deuterium burning mass. Our L odot;bol-based hot-start estimate for temperature is T eff = 1643 ± 32 K (not including model-dependent uncertainty). Due to the large corresponding model-derived radius of R = 1.43 ± 0.02 R Jup, this T eff is ∼250 K cooler than would be expected for a field L2.5 BD. Other young, low-gravity (large-radius), ultracool dwarfs and directly imaged EGPs also have lower effective temperatures than are implied by their spectral types. However, such objects tend to be anomalously red in the near-IR compared to field BDs. In contrast, β Pic b has near-IR colors more typical of an early-L dwarf despite its lower inferred temperature. © 2014. The American Astronomical Society. All rights reserved.


Wahhaj Z.,European Southern Observatory | Liu M.C.,University of Hawaii at Manoa | Biller B.A.,Max Planck Institute for Astronomy | Nielsen E.L.,University of Hawaii at Manoa | And 6 more authors.
Astrophysical Journal | Year: 2013

We present high-contrast image processing techniques used by the Gemini NICI Planet-Finding Campaign to detect faint companions to bright stars. The Near-Infrared Coronographic Imager (NICI) is an adaptive optics instrument installed on the 8 m Gemini South telescope, capable of angular and spectral difference imaging and specifically designed to image exoplanets. The Campaign data pipeline achieves median contrasts of 12.6 mag at 0.″5 and 14.4 mag at 1″ separation, for a sample of 45 stars (V = 4.3-13.9 mag) from the early phase of the campaign. We also present a novel approach to calculating contrast curves for companion detection based on 95% completeness in the recovery of artificial companions injected into the raw data, while accounting for the false-positive rate. We use this technique to select the image processing algorithms that are more successful at recovering faint simulated point sources. We compare our pipeline to the performance of the Locally Optimized Combination of Images (LOCI) algorithm for NICI data and do not find significant improvement with LOCI. © 2013. The American Astronomical Society. All rights reserved..

Loading Mauna Kea Infrared LLC. collaborators
Loading Mauna Kea Infrared LLC. collaborators