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Sökning: WFRF:(Serabyn Eugene)

  • Resultat 1-10 av 25
  • [1]23Nästa
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1.
  • Absil, Olivier, et al. (författare)
  • An update on the VORTEX project
  • 2015
  • Ingår i: Techniques and Instrumentation for Detection of Exoplanets VII.
  • Konferensbidrag (refereegranskat)abstract
    • <p>In this talk, we will review the on-going activities within the VORTEX teamat the University of Liège and Uppsala University. The VORTEX project aimsto design, manufacture, test, and exploit vector vortex phase masks madeof sub-wavelength gratings (aka the Annular Groove Phase Mask, AGPM)for the direct detection and characterization of extrasolar planets. This talkwill specifically report on the commissioning of several AGPMs on infraredcameras equipping 10-m class telescopes, including the VLT, the LBT andthe Keck. We will describe the in-lab and on-sky performance of the AGPMs,and discuss first scientific observations. We will also report on the lessonslearned from the on-sky operation of our vortices, and discuss ways toimprove their performance. The potential of our coronagraphic devices inthe context of future extremely large telescopes and space missions will alsobe addressed.</p>
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2.
  • Absil, Oliver, et al. (författare)
  • Three years of harvest with the vector vortex coronagraph in the thermal infrared
  • 2016
  • Ingår i: Ground-Based and Airborne Instrumentation for Astronomy VI : 26-30 June 2016, Edinburgh, United Kingdom. - SPIE - International Society for Optical Engineering. - 978-1-5106-0196-3 ; s. 1-14
  • Konferensbidrag (refereegranskat)abstract
    • <p>For several years, we have been developing vortex phase masks based on sub-wavelength gratings, known as Annular Groove Phase Masks. Etched onto diamond substrates, these AGPMs are currently designed to be used in the thermal infrared (ranging from 3 to 13 μm). Our AGPMs were first installed on VLT/NACO and VLT/VISIR in 2012, followed by LBT/LMIRCam in 2013 and Keck/NIRC2 in 2015. In this paper, we review the development, commissioning, on-sky performance, and early scientific results of these new coronagraphic modes and report on the lessons learned. We conclude with perspectives for future developments and applications.</p>
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3.
  • Akiyama, Eiji, et al. (författare)
  • SPIRAL STRUCTURE AND DIFFERENTIAL DUST SIZE DISTRIBUTION IN THE LkH alpha 330 DISK
  • 2016
  • Ingår i: Astronomical Journal. - 0004-6256 .- 1538-3881. ; 152:6
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>Dust trapping accelerates the coagulation of dust particles, and, thus, it represents an initial step toward the formation of planetesimals. We report H-band (1.6 mu m) linear polarimetric observations and 0.87 mm interferometric continuum observations toward a transitional disk around LkH alpha 330. As a. result, a pair of spiral arms were detected in the H-band emission, and an asymmetric (potentially arm-like) structure was detected in the 0.87 mm continuum emission. We discuss the origin of the spiral arm and the asymmetric structure. and suggest that a massive unseen planet is the most plausible explanation. The possibility of dust trapping and grain growth causing the asymmetric structure was also investigated through the opacity index (beta) by plotting the observed spectral energy distribution slope between 0.87 mm from our Submillimeter Array observation and 1.3 mm from literature. The results imply that grains are indistinguishable from interstellar medium-like dust in the east side (beta = 2.0 +/- 0.5) but are much smaller in the west side beta = 0.7(-0.4)(+0.5), indicating differential dust size distribution between the two sides of the disk. Combining the results of near-infrared and submillimeter observations, we conjecture that the spiral arms exist at the upper surface and an asymmetric structure resides in the disk interior. Future observations at centimeter wavelengths and differential polarization imaging in other bands (Y-K) with extreme AO imagers are required to understand how large dust grains form and to further explore the dust distribution in the disk.</p>
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4.
  • Castellá, Bruno Femenía, et al. (författare)
  • Commissioning and first light results of an L’-band vortex coronagraph with the Keck II adaptive optics NIRC2 science instrument
  • 2016
  • Ingår i: Adaptive Optics Systems V. - SPIE - International Society for Optical Engineering.
  • Konferensbidrag (refereegranskat)abstract
    • <p>On March 2015 an L'-band vortex coronagraph based on an Annular Groove Phase Mask made up of a diamond sub-wavelength grating was installed on NIRC2 as a demonstration project. This vortex coronagraph operates in the L' band not only in order to take advantage from the favorable star/planet contrast ratio when observing beyond the K band, but also to exploit the fact that the Keck II Adaptive Optics (AO) system delivers nearly extreme adaptive optics image quality (Strehl ratios values near 90%) at 3.7 mu m. We describe the hardware installation of the vortex phase mask during a routine NIRC2 service mission. The success of the project depends on extensive software development which has allowed the achievement of exquisite real-time pointing control as well as further contrast improvements by using speckle nulling to mitigate the effect of static speckles. First light of the new coronagraphic mode was on June 2015 with already very good initial results. Subsequent commissioning nights were interlaced with science nights by members of the VORTEX team with their respective scientific programs. The new capability and excellent results so far have motivated the VORTEX team and the Keck Science Steering Committee (KSSC) to offer the new mode in shared risk mode for 2016B.</p>
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5.
  • Coughlin, Michael W., et al. (författare)
  • GROWTH on S190425z : Searching Thousands of Square Degrees to Identify an Optical or Infrared Counterpart to a Binary Neutron Star Merger with the Zwicky Transient Facility and Palomar Gattini-IR
  • 2019
  • Ingår i: Astrophysical Journal Letters. - 2041-8205 .- 2041-8213. ; 885:1
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>The third observing run by LVC has brought the discovery of many compact binary coalescences. Following the detection of the first binary neutron star merger in this run (LIGO/Virgo S190425z), we performed a dedicated follow-up campaign with the Zwicky Transient Facility (ZTF) and Palomar Gattini-IR telescopes. The initial skymap of this single-detector gravitational wave (GW) trigger spanned most of the sky observable from Palomar Observatory. Covering 8000 deg(2) of the initial skymap over the next two nights, corresponding to 46% integrated probability, ZTF system achieved a depth of 21 m(AB) in g- and r-bands. Palomar Gattini-IR covered 2200 square degrees in J-band to a depth of 15.5 mag, including 32% integrated probability based on the initial skymap. The revised skymap issued the following day reduced these numbers to 21% for the ZTF and 19% for Palomar Gattini-IR. We narrowed 338,646 ZTF transient ?alerts? over the first two nights of observations to 15 candidate counterparts. Two candidates, ZTF19aarykkb and ZTF19aarzaod, were particularly compelling given that their location, distance, and age were consistent with the GW event, and their early optical light curves were photometrically consistent with that of kilonovae. These two candidates were spectroscopically classified as young core-collapse supernovae. The remaining candidates were ruled out as supernovae. Palomar Gattini-IR did not identify any viable candidates with multiple detections only after merger time. We demonstrate that even with single-detector GW events localized to thousands of square degrees, systematic kilonova discovery is feasible.</p>
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6.
  • Currie, Thayne, et al. (författare)
  • SCExAO/CHARIS Near-infrared Direct Imaging, Spectroscopy, and Forward-Modeling of kappa And b : A Likely Young, Low-gravity Superjovian Companion
  • 2018
  • Ingår i: Astronomical Journal. - 0004-6256 .- 1538-3881. ; 156:6
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We present SCExAO/CHARIS high-contrast imaging/JHK integral field spectroscopy of kappa And b, a directly imaged low-mass companion orbiting a nearby B9V star. We detect kappa And b at a high signal-to-noise ratio and extract high-precision spectrophotometry using a new forward-modeling algorithm for (A-)LOCI complementary to KLIP-FM developed by Pueyo et al. kappa And b's spectrum best resembles that of a low-gravity LO-L1 dwarf (L0-L1 gamma). Its spectrum and luminosity are very well matched by 2MASS J0141-4633 and several other 12.5-15 M-J free-floating members of the 40 Myr old Tuc-Hor Association, consistent with a system age derived from recent interferometric results for the primary, a companion mass at/near the deuterium-burning limit (13(-2)(+12) M-J), and a companion-to-primary mass ratio characteristic of other directly imaged planets (q similar to 0.0051(-0.001)(+0.005)). We did not unambiguously identify additional, more closely orbiting companions brighter and more massive than kappa And b down to p similar to 0.'' 3 (15 au). SCExAO/CHARIS and complementary Keck/NIRC2 astrometric points reveal clockwise orbital motion. Modeling points toward a likely eccentric orbit: a subset of acceptable orbits include those that are aligned with the star's rotation axis. However, kappa And b's semimajor axis is plausibly larger than 55 au and in a region where disk instability could form massive companions. Deeper high-contrast imaging of kappa And and low-resolution spectroscopy from extreme adaptive optics systems such as SCExAO/CHARIS and higher-resolution spectroscopy from Keck/OSIRIS or, later, IRIS on the Thirty Meter Telescope could help to clarify kappa And b's chemistry and whether its spectrum provides an insight into its formation environment.</p>
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7.
  • Currie, Thayne, et al. (författare)
  • Subaru/SCExAO First-light Direct Imaging of a Young Debris Disk around HD 36546
  • 2017
  • Ingår i: Astrophysical Journal Letters. - 2041-8205 .- 2041-8213. ; 836:1
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We present H-band scattered light imaging of a bright debris disk around the A0 star HD 36546 obtained from the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system with data recorded by the HiCIAO camera using the vector vortex coronagraph. SCExAO traces the disk from r similar to 0.3 to r similar to 1 (34-114 au). The disk is oriented in a near east-west direction (PA similar to 75 degrees), is inclined by i similar to 70 degrees-75 degrees, and is strongly forward-scattering (g &gt; 0.5). It is an extended disk rather than a sharp ring; a second, diffuse dust population extends from the disk's eastern side. While HD 36546 intrinsic properties are consistent with a wide age range (t similar to 1-250 Myr), its kinematics and analysis of coeval stars suggest a young age (3-10 Myr) and a possible connection to Taurus-Auriga's star formation history. SCExAO's planet-to-star contrast ratios are comparable to the first-light Gemini Planet Imager contrasts; for an age of 10 Myr, we rule out planets with masses comparable to HR 8799 b beyond a projected separation of 23 au. A massive icy planetesimal disk or an unseen super-Jovian planet at r &gt; 20 au may explain the disk's visibility. The HD 36546 debris disk may be the youngest debris disk yet imaged, is the first newly identified object from the now-operational SCExAO extreme AO system, is ideally suited for spectroscopic follow-up with SCExAO/CHARIS in 2017, and may be a key probe of icy planet formation and planet-disk interactions.</p>
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8.
  • de Leon, Jerome, et al. (författare)
  • NEAR-IR HIGH-RESOLUTION IMAGING POLARIMETRY OF THE SU Aur DISK : CLUES FOR TIDAL TAILS?
  • 2015
  • Ingår i: Astrophysical Journal Letters. - 2041-8205 .- 2041-8213. ; 806:1
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We present new high-resolution (similar to 0.09) H-band imaging observations of the circumstellar disk around the T Tauri star SU Aur. Our observations with Subaru-HiCIAO have revealed the presence of scattered light as close as 0.15 (similar to 20 AU) to the star. Within our image, we identify bright emission associated with a disk with a minimum radius of similar to 90 AU, an inclination of similar to 35 degrees from the plane of the sky, and an approximate PA of 15 degrees for the major axis. We find a brightness asymmetry between the northern and southern sides of the disk due to a non-axisymmetric disk structure. We also identify a pair of asymmetric tail structures extending east and west from the disk. The western tail extends at least 2.5 (350 AU) from the star, and is probably associated with a reflection nebula previously observed at optical and near-IR wavelengths. The eastern tail extends at least 1. (140 AU) at the present signal-to-noise. These tails are likely due to an encounter with an unseen brown dwarf, but our results do not exclude the explanation that these tails are outflow cavities or jets.</p>
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9.
  • Follette, Katherine B., et al. (författare)
  • SEEDS ADAPTIVE OPTICS IMAGING OF THE ASYMMETRIC TRANSITION DISK OPH IRS 48 IN SCATTERED LIGHT
  • 2015
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 798:2
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We present the first resolved near-infrared imagery of the transition disk Oph IRS 48 (WLY 2-48), which was recently observed with ALMA to have a strongly asymmetric submillimeter flux distribution. H-band polarized intensity images show a similar to 60 AU radius scattered light cavity with two pronounced arcs of emission, one from northeast to southeast and one smaller, fainter, and more distant arc in the northwest. K-band scattered light imagery reveals a similar morphology, but with a clear third arc along the southwestern rim of the disk cavity. This arc meets the northwestern arc at nearly a right angle, revealing the presence of a spiral arm or local surface brightness deficit in the disk, and explaining the east-west brightness asymmetry in the H-band data. We also present 0.8-5.4 mu m IRTF SpeX spectra of this object, which allow us to constrain the spectral class to A0 +/- 1 and measure a low mass accretion rate of 10(-8.5) M-circle dot yr(-1), both consistent with previous estimates. We investigate a variety of reddening laws in order to fit the multiwavelength spectral energy distribution of Oph IRS 48 and find a best fit consistent with a younger, higher luminosity star than previous estimates.</p>
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10.
  • Konishi, Mihoko, et al. (författare)
  • A substellar companion to Pleiades HII 3441
  • 2016
  • Ingår i: Publications of the Astronomical Society of Japan. - 0004-6264. ; 68:6
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We find a new substellar companion to the Pleiades member star, Pleiades HII 3441, using the Subaru telescope with adaptive optics. The discovery is made as part of the high-contrast imaging survey to search for planetary-mass and substellar companions in the Pleiades and young moving groups. The companion has a projected separation of 0.'' 49 +/- 0.'' 02 (66 +/- 2 au) and a mass of 68 +/- 5 M-J based on three observations in the J-, H-, and K-s-bands. The spectral type is estimated to be M7 (similar to 2700 K), and thus no methane absorption is detected in the H band. Our Pleiades observations result in the detection of two substellar companions including one previously reported among 20 observed Pleiades stars, and indicate that the fraction of substellar companions in the Pleiades is about 10.0(-8.8)(+26.1)%. This is consistent with multiplicity studies of both the Pleiades stars and other open clusters.</p>
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