462 research outputs found
Photometric properties of intermediate-redshift Type Ia supernovae observed by the Sloan Digital Sky Survey-II Supernova Survey
Simulated and experimental results of dual resolution sensor based planning for hyper-redundant manipulators
This paper presents a dual-resolution local sensor based planning method for hyper-redundant robot mechanisms. Two classes of sensor feedback control methods, working at different sampling rates and different spatial resolutions, are considered: full shape modification (FSM), and partial shape modification (PSM). FSM and PSM cooperate to utilize a mechanism's hyper-redundancy to enable both local obstacle avoidance and end-effector placement in real-time. These methods have been implemented on a thirty degree of freedom hyper-redundant manipulator which has 11 ultrasonic distance measurement sensors and 20 infrared proximity sensors. The implementation of these algorithms in a dual CPU real-time control computer, an innovative sensor bus architecture, and a novel graphical control interface are described. Experimental results obtained using this test bed show the efficacy of the proposed method
Rest-Frame R-band Lightcurve of a z~1.3 Supernova Obtained with Keck Laser Adaptive Optics
We present Keck diffraction limited H-band photometry of a z~1.3 Type Ia
supernova (SN) candidate, first identified in a Hubble Space Telescope (HST)
search for SNe in massive high redshift galaxy clusters. The adaptive optics
(AO) data were obtained with the Laser Guide Star facility during four
observing runs from September to November 2005. In the analysis of data from
the observing run nearest to maximum SN brightness, the SN was found to have a
magnitude H=23.9 +/- 0.14 (Vega). We present the H-band (approximately
rest-frame R) light curve and provide a detailed analysis of the AO photometric
uncertainties. By constraining the aperture correction with a nearby (4"
separation) star we achieve 0.14 magnitude photometric precision, despite the
spatially varying AO PSF.Comment: 11 pages, 8 figures, Accepted for Publication in AJ Updated the
citations, fixed typo
Subaru FOCAS Spectroscopic Observations of High-Redshift Supernovae
We present spectra of high-redshift supernovae (SNe) that were taken with the
Subaru low resolution optical spectrograph, FOCAS. These SNe were found in SN
surveys with Suprime-Cam on Subaru, the CFH12k camera on the
Canada-France-Hawaii Telescope (CFHT), and the Advanced Camera for Surveys
(ACS) on the Hubble Space Telescope (HST). These SN surveys specifically
targeted z>1 Type Ia supernovae (SNe Ia). From the spectra of 39 candidates, we
obtain redshifts for 32 candidates and spectroscopically identify 7 active
candidates as probable SNe Ia, including one at z=1.35, which is the most
distant SN Ia to be spectroscopically confirmed with a ground-based telescope.
An additional 4 candidates are identified as likely SNe Ia from the
spectrophotometric properties of their host galaxies. Seven candidates are not
SNe Ia, either being SNe of another type or active galactic nuclei. When SNe Ia
are observed within a week of maximum light, we find that we can
spectroscopically identify most of them up to z=1.1. Beyond this redshift, very
few candidates were spectroscopically identified as SNe Ia. The current
generation of super red-sensitive, fringe-free CCDs will push this redshift
limit higher.Comment: 19 pages, 26 figures. PASJ in press. see
http://www.supernova.lbl.gov/2009ClusterSurvey/ for additional information
pertaining to the HST Cluster SN Surve
The Hubble Space Telescope Cluster Supernova Survey: VI. The Volumetric Type Ia Supernova Rate
We present a measurement of the volumetric Type Ia supernova (SN Ia) rate out
to z ~ 1.6 from the Hubble Space Telescope Cluster Supernova Survey. In
observations spanning 189 orbits with the Advanced Camera for Surveys we
discovered 29 SNe, of which approximately 20 are SNe Ia. Twelve of these SNe Ia
are located in the foregrounds and backgrounds of the clusters targeted in the
survey. Using these new data, we derive the volumetric SN Ia rate in four broad
redshift bins, finding results consistent with previous measurements at z > 1
and strengthening the case for a SN Ia rate that is equal to or greater than
~0.6 x 10^-4/yr/Mpc^3 at z ~ 1 and flattening out at higher redshift. We
provide SN candidates and efficiency calculations in a form that makes it easy
to rebin and combine these results with other measurements for increased
statistics. Finally, we compare the assumptions about host-galaxy dust
extinction used in different high-redshift rate measurements, finding that
different assumptions may induce significant systematic differences between
measurements.Comment: 11 pages, 7 figures. Submitted to the Astrophysical Journal. Revised
version following referee comments. See the HST Cluster SN Survey website at
http://supernova.lbl.gov/2009ClusterSurvey for control time simulations in a
machine-readable table and a complete listing of transient candidates from
the surve
The Hubble Space Telescope Cluster Supernova Survey: II. The Type Ia Supernova Rate in High-Redshift Galaxy Clusters
We report a measurement of the Type Ia supernova (SN Ia) rate in galaxy
clusters at 0.9 < z < 1.45 from the Hubble Space Telescope (HST) Cluster
Supernova Survey. This is the first cluster SN Ia rate measurement with
detected z > 0.9 SNe. Finding 8 +/- 1 cluster SNe Ia, we determine a SN Ia rate
of 0.50 +0.23-0.19 (stat) +0.10-0.09 (sys) SNuB (SNuB = 10^-12 SNe L_{sun,B}^-1
yr^-1). In units of stellar mass, this translates to 0.36 +0.16-0.13 (stat)
+0.07-0.06 (sys) SNuM (SNuM = 10^-12 SNe M_sun^-1 yr^-1). This represents a
factor of approximately 5 +/- 2 increase over measurements of the cluster rate
at z < 0.2. We parameterize the late-time SN Ia delay time distribution with a
power law (proportional to t^s). Under the assumption of a cluster formation
redshift of z_f = 3, our rate measurement in combination with lower-redshift
cluster SN Ia rates constrains s = -1.41 +0.47/-0.40, consistent with
measurements of the delay time distribution in the field. This measurement is
generally consistent with expectations for the "double degenerate" scenario and
inconsistent with some models for the "single degenerate" scenario predicting a
steeper delay time distribution at large delay times. We check for
environmental dependence and the influence of younger stellar populations by
calculating the rate specifically in cluster red-sequence galaxies and in
morphologically early-type galaxies, finding results similar to the full
cluster rate. Finally, the upper limit of one host-less cluster SN Ia detected
in the survey implies that the fraction of stars in the intra-cluster medium is
less than 0.47 (95% confidence), consistent with measurements at lower
redshifts.Comment: 29 pages, 14 figures. Accepted for publication in ApJ on 16 February
2011. See the HST Cluster Supernova Survey website at
http://supernova.lbl.gov/2009ClusterSurvey for a version with full-resolution
images and a complete listing of transient candidates from the survey. This
version fixes a typo in the metadata; the paper is unchanged from v
Epitaxial contact Andreev reflection spectroscopy of NbN/Co<sub>2</sub>FeSi layered devices
We investigated the spin polarization P of Co-based Heusler alloy Co2FeSi by epitaxial contact Andreev reflection (ECAR) spectroscopy using epitaxially grown superconductor NbN and Heusler alloy Co2FeSi layered devices. Ferromagnetic Co2FeSi possesses the highest Curie temperature (TC ? 1100 K) and the largest spontaneous magnetic moment (ps ? 6 μB) in the class of Heusler alloys. The ECAR measurements revealed that the P value of Co2FeSi was 54 ± 2% with a finite barrier parameter Z, indicating that an intrinsic P value in ECAR spectroscopy would exceed reported values in point-contact Andreev reflection spectroscopy. We therefore established not only the epitaxial integration of ferromagnetic Co2FeSi with superconductor NbN on an MgO substrate but also the fabrication and evaluation techniques of their ECAR devices. This highly versatile superconducting spintronic system enables fundamental superconducting spintronic studies, and it is also a candidate for practical superconducting spintronic devices
Interesting magnetic properties of FeCoSi alloys
Solid solution between nonmagnetic narrow gap semiconductor FeSi and
diamagnetic semi-metal CoSi gives rise to interesting metallic alloys with
long-range helical magnetic ordering, for a wide range of intermediate
concentration. We report various interesting magnetic properties of these
alloys, including low temperature re-entrant spin-glass like behaviour and a
novel inverted magnetic hysteresis loop. Role of Dzyaloshinski-Moriya
interaction in the magnetic response of these non-centrosymmetric alloys is
discussed.Comment: 11 pages and 3 figure
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