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  • 1
    Electronic Resource
    Electronic Resource
    Electrostatic effect on the flow behavior of a dilute gas/cohesive particle flow system (1996)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 1590-1599 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Cohesive (Group C) particles have been widely used in various industries. To handle and process such fine particles, a clear understanding of the flow behavior and interparticle force, is needed. To achieve that objective, a Laser Doppler Anemometer system was used to measure particle velocity, fluctuating velocity, and size and extent of agglomeration or cluster formation of particles in a dilute gas/fine oil shale particle flow system with particle density of 2,082 kg/m3, average particle volumetric concentration of 1.5%, and average particle mass flux of about 100 kg/m2·s in a controlled-moisture environment. The flow behavior of the particles was also studied for a mixture of 99% shale particles and 1% antistatic agent (Larostat powder, a quaternary ammonium compound) to examine the role of electrostatic force in gas/cohesive particle flow behavior. The addition of Larostat powder significantly reduced the electrostatic force and, in turn, made Group C particles behave similar to Group A or in some cases to Group B particles. In addition, our experimental data showed that the Maxwellian distribution function is a reasonable assumption to describe the velocity probability density function of the shale particles with or without antistatic agents.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690420610
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  • 2
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    Differences in the Gas and Dust Distribution in the Transitional Disk of a Sun-Like Young Star, PDS 70 (2018)
    In:  Other Sources
    Details
    Publication Date: 2019-05-30
    Description: We present ALMA 0.87 mm continuum, HCO+ J = 43 emission line, and CO J = 32 emission line data of the disk of material around the young, Sun-like star PDS 70. These data reveal the existence of a possible two-component transitional disk system with a radial dust gap of 0.42 arcsec 0.05 arcsec, an azimuthal gap in the HCO+ J = 43 moment zero map, as well as two bridge-like features in the gas data. Interestingly these features in the gas disk have no analog in the dust disk making them of particular interest. We modeled the dust disk using the Monte Carlo radiative transfer code HOCHUNK3D using a two-disk component. We nd that there is a radial gap that extends from 15 to 60 au in all grain sizes, which differs from previous work.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN64788 , Astrophysical Journal (ISSN 0004-637X) (e-ISSN 1538-4357); 858; 2; 112
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  • 3
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    High-Contrast Polarimetry Observation of the T Tau Circumstellar Environment (2018)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: We conducted high-contrast polarimetry observations of T Tau in the H-band, using the High Contrast Instrument for the Subaru Next Generation Adaptive Optics instrument mounted on the Subaru Telescope, revealing structures as near as 0farcs1 from the stars T Tau N and T Tau S. The whole T Tau system is found to be surrounded by nebula-like envelopes, and several outflow-related structures are detected in these envelopes. We analyzed the detailed polarization patterns of the circumstellar structures near each component of this triple young star system and determined constraints on the circumstellar disks and outflow structures. We suggest that the nearly face-on circumstellar disk of T Tau N is no larger than 0".8, or 117 au, in the northwest, based on the existence of a hole in this direction, and no larger than 0".27, or 40 au, in the south. A new structure, "N5," extends to about 0."42, or 59 au, southwest of the star, and is believed to be part of the disk. We suggest that T Tau S is surrounded by a highly inclined circumbinary disk with a radius of about 0."3, or 44 au, with a position angle of about 30, that is misaligned with the orbit of the T Tau S binary. After analyzing the positions and polarization vector patterns of the outflow-related structures, we suggest that T Tau S should trigger the well-known EW outflow, and is also likely to be responsible for a southwest precessing outflow "coil" and a possible south outflow.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN64810 , The Astrophysical Journal (ISSN 0004-637X) (e-ISSN 1538-4357); 861; 2; 133
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  • 4
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    Subaru/HiCIAO HK(sub S) Imaging of LKHa 330: Multi-Band Detection of the Gap and Spiral-Like Structures (2018)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: We present H- and K s-bands observations of the LkH 330 disk with a multi-band detection of the large gap and spiral-like structures. The morphology of the outer disk (r ~ 0."3) at PA = 045 and PA = 180290 is likely density wave-induced spirals, and comparison between our observational results and simulations suggests a planet formation. We have also investigated the azimuthal profiles at the ring and the outer-disk regions as well as radial profiles in the directions of the spiral-like structures and semimajor axis. Azimuthal analysis shows a large variety in wavelength and implies that the disk has non-axisymmetric dust distributions. The radial profiles in the major-axis direction (PA = 271) suggest that the outer region (r 0."25) may be influenced by shadows of the inner region of the disk. The spiral-like directions (PA = 10 and 230) show different radial profiles, which suggests that the surfaces of the spiral-like structures are highly flared and/or have different dust properties. Finally, a color map of the disk shows a lack of an outer eastern region in the H-band disk, which may hint at the presence of an inner object that casts a directional shadow onto the disk.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN64807 , The Astrophysical Journal (ISSN 0004-6256) (e-ISSN 1538-3881); 156; 2; 63
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  • 5
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    SCExAO/CHARIS Near-IR High-Contrast Imaging and Integral Field Spectroscopy of the HIP 79977 Debris Disk (2018)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: We present new, near-infrared (1.12.4 m) high-contrast imaging of the bright debris disk surrounding HIP 79977 with the Subaru Coronagraphic Extreme Adaptive Optics system (SCExAO) coupled with the CHARIS integral eld spectrograph. SCExAO/CHARIS resolves the disk down to smaller angular separations of (0".11; r 14 au) and at a higher signicance than previously achieved at the same wavelengths. The disk exhibits a marginally signicant eastwest brightness asymmetry in H band that requires conrmation. Geometrical modeling suggests a nearly edge-on disk viewed at a position angle of 114.6 east of north. The disk is best-t by scattered-light models assuming strongly forward-scattering grains (g 0.50.65) conned to a torus with a peak density at r0 5375 au. We nd that a shallow outer density power law of (sub out) = 1 to 3 and are index of = 1 are preferred. Other disk parameters (e.g., inner density power law and vertical scale height) are more poorly constrained. The disk has a slightly blue intrinsic color and its prole is broadly consistent with predictions from birth ring models applied to other debris disks. While HIP 79977s disk appears to be more strongly forward- scattering than most resolved disks surrounding 530 Myr old stars, this difference may be due to observational biases favoring forward-scattering models for inclined disks versus lower inclination, ostensibly neutral-scattering disks like HR 4796As. Deeper, higher signal-to-noise SCExAO/CHARIS data can better constrain the disks dust composition.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN64796 , The Astrophysical Journal (ISSN 0004-637X) (e-ISSN 1538-4357); 156; 6; 279
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  • 6
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    Subaru SCExAO First-Light Direct Imaging of a Young Debris Disk around HD 36546 (2017)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: 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 approximately 0 3 to r approximately 0".3 to r approximately 1" (34-114 au). The disk is oriented in a near east west direction (PA approximately 75deg), is inclined by I approximately 70deg-75deg, and is strongly forward-scattering(g greater than 0.5). It is an extended disk rather than a sharp ring; a second, diffuse dust population extends from the disks eastern side. While HD 36546 intrinsic properties are consistent with a wide age range (t approximately 1-250 Myr), its kinematics and analysis of coeval stars suggest a young age (310 Myr) and a possible connection to Taurus-Aurigas star formation history. SCExAOs 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 greater than 20 au may explain the disks 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.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN45673 , The Astrophysical Journal Letters (ISSN 2041-8205) (e-ISSN 2041-8213); 836; 1; L15
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  • 7
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    The Shadow Knows: Using Shadows to Investigate the Structure of the Pretransitional Disk of HD 100453 (2017)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We present Gemini Planet Imager polarized intensity imagery of HD 100453 in Y, J, and K1 bands that reveals an inner gap (9-18 au), an outer disk (18-39 au) with two prominent spiral arms, and two azimuthally localized dark features that are also present in Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) total intensity images. Spectral energy distribution fitting further suggests that the radial gap extends to 1 au. The narrow, wedge-like shape of the dark features appears similar to predictions of shadows cast by an inner disk that is misaligned with respect to the outer disk. Using the Monte Carlo radiative transfer code HOCHUNCK3D, we construct a model of the disk that allows us to determine its physical properties in more detail. From the angular separation of the features, we measure the difference in inclination between the disks (45deg) and their major axes, PA = 140deg east of north for the outer disk, and 100deg for the inner disk. We find an outer-disk inclination of 25deg +/- 10deg from face-on, in broad agreement with the Wagner et al. measurement of 34deg. SPHERE data in J and H bands indicate a reddish disk, which indicates that HD 100453 is evolving into a young debris disk.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN45649 , The Astrophysical Journal (ISSN 2041-8205) (e-ISSN 2041-8213); 838; 1; 62
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  • 8
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    Discovery of Highly Blueshifted Broad Balmer and Metastable Helium Absorption Lines in a Tidal Disruption Event (2019)
    In:  CASI
    Details
    Publication Date: 2019-11-30
    Description: We report the discovery of nonstellar hydrogen Balmer and metastable helium absorption lines accompanying a transient, high-velocity (0.05c) broad absorption line (BAL) system in the optical spectra of the tidal disruption event (TDE) AT2018zr (z = 0.071). In the Hubble Space Telescope UV spectra, absorption of high- and low-ionization lines is also present at this velocity, making AT2018zr resemble a low-ionization BALQSO. We conclude that these transient absorption features are more likely to arise in fast outflows produced by the TDE than absorbed by the unbound debris. In accordance with the outflow picture, we are able to reproduce the flat-topped H emission in a spherically expanding medium without invoking the typical prescription of an elliptical disk. We also report the appearance of narrow (~1000 kms(exp 1)) N III 4640, He II 4686, H, and H emission in the late-time optical spectra of AT2018zr, which may be a result of UV continuum hardening at late times, as observed by Swift. Including AT2018zr, we find a high association rate (three out of four) of BALs in the UV spectra of TDEs. This suggests that outflows may be ubiquitous among TDEs and less sensitive to viewing angle effects compared to QSO outflows.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN75254 , Astrophysical Journal (ISSN 0004-637X) (e-ISSN 1538-4357); 879; 2; 119
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  • 9
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    Near-Infrared Imaging Polarimetry of Inner Region of GG Tau A Disk (2016)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: By performing non-masked polarization imaging with Subaru HiCIAO, polarized scattered light from the inner region of the disk around the GGTau A system was successfully detected in the H band, with a spatial resolution of approximately0 07, revealing the complicated inner disk structures around this young binary. This paper reports the observation of an arc-like structure to the north of GG Tau Ab, and part of a circumstellar structure that is noticeable around GG Tau Aa, extending to a distance of approximately 28 au from the primary star. The speckle noise around GG Tau Ab constrains its disk radius to 13 au. Based on the size of the circumbinary ring and the circumstellar disk around GG Tau Aa, these mimajor axis of the binary's orbit is likely to be 62 au. A comparison of the present observations with previous Atacama Large Millimeter Array and near-infrared H2 emission observations suggests that the north arc could be part of a large streamer flowing from the circumbinary ring to sustain the circumstellar disks. According to the previous studies,the circumstellar disk around GG Tau Aa has enough mass and can sustain itself for a duration sufficient for planet formation; thus, our study indicates that planets can form within close (separation 100 au) young binary systems.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN43990 , The Astronomical Journal (ISSN 1538-3881); 153; 1; 7
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