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Subaru Imaging of Asymmetric Features in a Transitional Disk in Upper Scorpius
Authors:
S. Mayama,
J. Hashimoto,
T. Muto,
T. Tsukagoshi,
N. Kusakabe,
M. Kuzuhara,
Y. Takahashi,
T. Kudo,
R. Dong,
M. Fukagawa,
M. Takami,
M. Momose,
J. P. Wisniewski,
K. Follette,
L. Abe,
E. Akiyama,
W. Brandner,
T. Brandt,
J. Carson,
S. Egner,
M. Feldt,
M. Goto,
C. A. Grady,
O. Guyon,
Y. Hayano
, et al. (30 additional authors not shown)
Abstract:
We report high-resolution (0.07 arcsec) near-infrared polarized intensity images of the circumstellar disk around the star 2MASS J16042165-2130284 obtained with HiCIAO mounted on the Subaru 8.2 m telescope. We present our $H$-band data, which clearly exhibits a resolved, face-on disk with a large inner hole for the first time at infrared wavelengths. We detect the centrosymmetric polarization patt…
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We report high-resolution (0.07 arcsec) near-infrared polarized intensity images of the circumstellar disk around the star 2MASS J16042165-2130284 obtained with HiCIAO mounted on the Subaru 8.2 m telescope. We present our $H$-band data, which clearly exhibits a resolved, face-on disk with a large inner hole for the first time at infrared wavelengths. We detect the centrosymmetric polarization pattern in the circumstellar material as has been observed in other disks. Elliptical fitting gives the semimajor axis, semiminor axis, and position angle (P.A.) of the disk as 63 AU, 62 AU, and -14 $^{\circ}$, respectively. The disk is asymmetric, with one dip located at P.A.s of $\sim85^{\circ}$. Our observed disk size agrees well with a previous study of dust and CO emission at submillimeter wavelength with Submillimeter Array. Hence, the near-infrared light is interpreted as scattered light reflected from the inner edge of the disk. Our observations also detect an elongated arc (50 AU) extending over the disk inner hole. It emanates at the inner edge of the western side of the disk, extending inward first, then curving to the northeast. We discuss the possibility that the inner hole, the dip, and the arc that we have observed may be related to the existence of unseen bodies within the disk.
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Submitted 14 November, 2012;
originally announced November 2012.
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Aerial Measurement of Radioxenon Concentration off the West Coast of Vancouver Island following the Fukushima Reactor Accident
Authors:
L. E. Sinclair,
H. C. J. Seywerd,
R. Fortin,
J. M. Carson,
P. R. B. Saull,
M. J. Coyle,
R. A. Van Brabant,
J. L. Buckle,
S. M. Desjardins,
R. M. Hall
Abstract:
In response to the Fukushima nuclear reactor accident, on March 20th, 2011, Natural Resources Canada conducted aerial radiation surveys over water just off of the west coast of Vancouver Island. Dose-rate levels were found to be consistent with background radiation, however a clear signal due to Xe-133 was observed. Methods to extract Xe-133 count rates from the measured spectra, and to determine…
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In response to the Fukushima nuclear reactor accident, on March 20th, 2011, Natural Resources Canada conducted aerial radiation surveys over water just off of the west coast of Vancouver Island. Dose-rate levels were found to be consistent with background radiation, however a clear signal due to Xe-133 was observed. Methods to extract Xe-133 count rates from the measured spectra, and to determine the corresponding Xe-133 volumetric concentration, were developed. The measurements indicate that Xe-133 concentrations on average lie in the range of 30 to 70 Bq/m3.
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Submitted 20 June, 2011;
originally announced June 2011.
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First measurement of low intensity fast neutron background from rock at the Boulby Underground Laboratory
Authors:
E. Tziaferi,
M. J. Carson,
V. A. Kudryavtsev,
R. Lerner,
P. K. Lightfoot,
S. M. Paling,
M. Robinson,
N. J. C. Spooner
Abstract:
A technique to measure low intensity fast neutron flux has been developed. The design, calibrations, procedure for data analysis and interpretation of the results are discussed in detail. The technique has been applied to measure the neutron background from rock at the Boulby Underground Laboratory, a site used for dark matter and other experiments, requiring shielding from cosmic ray muons. The…
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A technique to measure low intensity fast neutron flux has been developed. The design, calibrations, procedure for data analysis and interpretation of the results are discussed in detail. The technique has been applied to measure the neutron background from rock at the Boulby Underground Laboratory, a site used for dark matter and other experiments, requiring shielding from cosmic ray muons. The experiment was performed using a liquid scintillation detector. A 6.1 litre volume stainless steel cell was filled with an in-house made liquid scintillator loaded with Gd to enhance neutron capture. A two-pulse signature (proton recoils followed by gammas from neutron capture) was used to identify the neutron events from much larger gamma background from PMTs. Suppression of gammas from the rock was achieved by surrounding the detector with high-purity lead and copper. Calibrations of the detector were performed with various gamma and neutron sources. Special care was taken to eliminate PMT afterpulses and correlated background events from the delayed coincidences of two pulses in the Bi-Po decay chain. A four month run revealed a neutron-induced event rate of 1.84 +- 0.65 (stat.) events/day. Monte Carlo simulations based on the GEANT4 toolkit were carried out to estimate the efficiency of the detector and the energy spectra of the expected proton recoils. From comparison of the measured rate with Monte Carlo simulations the flux of fast neutrons from rock was estimated as (1.72 +- 0.61 (stat.) +- 0.38 (syst.))*10^(-6) cm^(-2) s^(-1) above 0.5 MeV.
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Submitted 8 December, 2006;
originally announced December 2006.
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Reduction of Coincident Photomultiplier Noise Relevant to Astroparticle Physics Experiment
Authors:
M. Robinson,
P. K. Lightfoot,
M. J. Carson,
V. A. Kudryavtsev,
N. J. C. Spooner
Abstract:
In low background and low threshold particle astrophysics experiments using observation of Cherenkov or scintillation light it is common to use pairs or arrays of photomultipliers operated in coincidence. In such circumstances, for instance in dark matter and neutrino experiments, unexpected PMT noise events have been observed, probably arising from generation of light from one PMT being detecte…
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In low background and low threshold particle astrophysics experiments using observation of Cherenkov or scintillation light it is common to use pairs or arrays of photomultipliers operated in coincidence. In such circumstances, for instance in dark matter and neutrino experiments, unexpected PMT noise events have been observed, probably arising from generation of light from one PMT being detected by one or more other PMTs. We describe here experimental investigation of such coincident noise events and development of new techniques to remove them using novel pulse shape discrimination procedures. When applied to data from a low background NaI detector with facing PMTs the new procedures are found to improve noise rejection by a factor of 20 over conventional techniques, with significantly reduced loss of signal events.
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Submitted 5 March, 2005;
originally announced March 2005.
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Metrological constraints on the variability of the fundamental constants $e$, $\hbar$, and $c$
Authors:
A. Yu. Ignatiev,
B. J. Carson
Abstract:
We set up a framework for a model-independent analysis of the time variation of $e$, $\hbar$, and $c$ indiviually. It is shown that the time-evolution of each constant can be determined uniquely from the time evolution of the fine structure constant $α$ provided that the choice of basic time-independent units (i.e., the clock and ruler) is fixed. Realistic systems of units are considered as exam…
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We set up a framework for a model-independent analysis of the time variation of $e$, $\hbar$, and $c$ indiviually. It is shown that the time-evolution of each constant can be determined uniquely from the time evolution of the fine structure constant $α$ provided that the choice of basic time-independent units (i.e., the clock and ruler) is fixed. Realistic systems of units are considered as examples and implications for metrology are discussed.
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Submitted 16 September, 2004; v1 submitted 8 December, 2003;
originally announced December 2003.