325 research outputs found
Three years of Fermi GBM Earth Occultation Monitoring: Observations of Hard X-ray/Soft Gamma-Ray Sources
The Gamma ray Burst Monitor (GBM) on board Fermi has been providing
continuous data to the astronomical community since 2008 August 12. In this
paper we present the results of the analysis of the first three years of these
continuous data using the Earth occultation technique to monitor a catalog of
209 sources. From this catalog, we detect 99 sources, including 40 low-mass
X-ray binary/neutron star systems, 31 high-mass X-ray binary neutron star
systems, 12 black hole binaries, 12 active galaxies, 2 other sources, plus the
Crab Nebula, and the Sun. Nine of these sources are detected in the 100-300 keV
band, including seven black-hole binaries, the active galaxy Cen A, and the
Crab. The Crab and Cyg X-1 are also detected in the 300-500 keV band. GBM
provides complementary data to other sky-monitors below 100 keV and is the only
all-sky monitor above 100 keV. Up-to-date light curves for all of the catalog
sources can be found at http://heastro.phys.lsu.edu/gbm/.Comment: 24 pages, 12 figures, accepted for publication in ApJ
Calibration of the GLAST Burst Monitor detectors
The GLAST Burst Monitor (GBM) will augment the capabilities of GLAST for the
detection of cosmic gamma-ray bursts by extending the energy range (20 MeV to >
300 GeV) of the Large Area Telescope (LAT) towards lower energies by 2
BGO-detectors (150 keV to 30 MeV) and 12 NaI(Tl) detectors (10 keV to 1 MeV).
The physical detector response of the GBM instrument for GRBs is determined
with the help of Monte Carlo simulations, which are supported and verified by
on-ground calibration measurements, performed extensively with the individual
detectors at the MPE in 2005. All flight and spare detectors were irradiated
with calibrated radioactive sources in the laboratory (from 14 keV to 4.43
MeV). The energy/channel-relations, the dependences of energy resolution and
effective areas on the energy and the angular responses were measured. Due to
the low number of emission lines of radioactive sources below 100 keV,
calibration measurements in the energy range from 10 keV to 60 keV were
performed with the X-ray radiometry working group of the
Physikalisch-Technische Bundesanstalt (PTB) at the BESSY synchrotron radiation
facility, Berlin.Comment: 2 pages, 1 figure; to appear in the Proc. of the First Int. GLAST
Symp. (Stanford, Feb. 5-8, 2007), eds. S.Ritz, P.F.Michelson, and C.Meegan,
AIP Conf. Pro
Probing the charging mechanisms of carbon nanomaterial polyelectrolytes
Chemical charging of single-walled carbon nanotubes (SWCNTs) and graphenes to generate soluble salts shows great promise as a processing route for electronic applications, but raises fundamental questions. The reduction potentials of highly-charged nanocarbon polyelectrolyte ions were investigated by considering their chemical reactivity towards metal salts/complexes in forming metal nanoparticles. The redox activity, degree of functionalisation and charge utilisation were quantified via the relative metal nanoparticle content, established using thermogravimetric analysis (TGA), inductively coupled plasma atomic emission spectroscopy (ICP-AES) and X-ray photoelectron spectroscopy (XPS). The fundamental relationship between the intrinsic nanocarbon electronic density of states and Coulombic effects during charging is highlighted as an important area for future research
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Quantifying the Opportunity Limits of Automatic Residential Electric Load Shaping
Electric utility residential demand response programs typically do not shape load using intraday, transactive, and local setpoint adjustments of storage-capable thermostatically controlled loads (TCL). In the future, it is envisioned that utilities will continually broadcast forecast dynamic prices of electricity to automatically shape residential load and create load elasticity by alternatively encouraging or discouraging electric energy use. In this research, a binary conditional algorithm was developed and applied to TCL appliance empirical time series data to estimate price-based instantaneous load add and shed opportunities. To overcome limitations of traditional stochastic methods in quantifying diverse, non-normal, non-stationary distributions, recent developments in spectral methods were applied to capture and simulate load in both the frequency and time domains. The performance of autoregressive and spectral reconstruction methods was compared, with phase reconstruction providing the best simulation ensembles. The terminal application of this work is simulating the monetary savings anticipated from wide-scale deployment of price-responsive model predictive control of air conditioning, domestic hot water (DHW) heating, and battery systems.</p
First-year Results of Broadband Spectroscopy of the Brightest Fermi-GBM Gamma-Ray Bursts
We present here our results of the temporal and spectral analysis of a sample
of 52 bright and hard gamma-ray bursts (GRBs) observed with the Fermi Gamma-ray
Burst Monitor (GBM) during its first year of operation (July 2008-July 2009).
Our sample was selected from a total of 253 GBM GRBs based on each event peak
count rate measured between 0.2 and 40MeV. The final sample comprised 34 long
and 18 short GRBs. These numbers show that the GBM sample contains a much
larger fraction of short GRBs, than the CGRO/BATSE data set, which we explain
as the result of our (different) selection criteria and the improved GBM
trigger algorithms, which favor collection of short, bright GRBs over BATSE. A
first by-product of our selection methodology is the determination of a
detection threshold from the GBM data alone, above which GRBs most likely will
be detected in the MeV/GeV range with the Large Area Telescope (LAT) onboard
Fermi. This predictor will be very useful for future multiwavelength GRB follow
ups with ground and space based observatories. Further we have estimated the
burst durations up to 10MeV and for the first time expanded the duration-energy
relationship in the GRB light curves to high energies. We confirm that GRB
durations decline with energy as a power law with index approximately -0.4, as
was found earlier with the BATSE data and we also notice evidence of a possible
cutoff or break at higher energies. Finally, we performed time-integrated
spectral analysis of all 52 bursts and compared their spectral parameters with
those obtained with the larger data sample of the BATSE data. We find that the
two parameter data sets are similar and confirm that short GRBs are in general
harder than longer ones.Comment: 40 pages, 11 figures, 3 tables, Submitted to Ap
The Vehicle, November 1960, Vol. 3 no. 1
CONTENTS
To the ReaderStaffpage 2
N’ = N : 1Donald C. Blairpage 3
ConsistencyDonald C. Blairpage 3
Unto MeLinda Kay Campbellpage 4
The Meek Shall InheritE. J. B. page 5
The Infinite QuestLarry W. Dudleypage 6
Dreamer’s DawnMike Hindmanpage 7
BirthNancy Coepage 7
The Lost DutchmanDonald C. Blairpage 8
W. E. Noonan IRobert S. Hodgepage 8
A Soldier’s OrdealDonald E. Shephardsonpage 9
Personal PossessionMary Beilpage 11
Thine The GloryDonald C. Blairpage 12
The ThornJan Holstlawpage 13
A Lord’s Day MorningLinda Campbellpage 14
Observations of a 6-Year-OldTom McPeakpage 15
Jewels of TimeJudith Jerintspage 16
LavenderE. J. B. page 16https://thekeep.eiu.edu/vehicle/1008/thumbnail.jp
The 3rd Fermi GBM Gamma-Ray Burst Catalog: The First Six Years
Since its launch in 2008, the Fermi Gamma-ray Burst Monitor (GBM) has
triggered and located on average approximately two gamma-ray bursts (GRB) every
three days. Here we present the third of a series of catalogs of GRBs detected
by GBM, extending the second catalog by two more years, through the middle of
July 2014. The resulting list includes 1405 triggers identified as GRBs. The
intention of the GBM GRB catalog is to provide information to the community on
the most important observables of the GBM detected GRBs. For each GRB the
location and main characteristics of the prompt emission, the duration, peak
flux and fluence are derived. The latter two quantities are calculated for the
50-300~keV energy band, where the maximum energy release of GRBs in the
instrument reference system is observed, and also for a broader energy band
from 10-1000 keV, exploiting the full energy range of GBM's low-energy NaI(Tl)
detectors. Using statistical methods to assess clustering, we find that the
hardness and duration of GRBs are better fitted by a two-component model with
short-hard and long-soft bursts, than by a model with three components.
Furthermore, information is provided on the settings and modifications of the
triggering criteria and exceptional operational conditions during years five
and six in the mission. This third catalog is an official product of the Fermi
GBM science team, and the data files containing the complete results are
available from the High-Energy Astrophysics Science Archive Research Center
(HEASARC).Comment: 225 pages, 13 figures and 8 tables. Accepted for publication in
Astrophysical Journal Supplement 201
The Fermi Gamma-Ray Burst Monitor
The Gamma-Ray Burst Monitor (GBM) will significantly augment the science
return from the Fermi Observatory in the study of Gamma-Ray Bursts (GRBs). The
primary objective of GBM is to extend the energy range over which bursts are
observed downward from the energy range of the Large Area Telescope (LAT) on
Fermi into the hard X-ray range where extensive previous data exist. A
secondary objective is to compute burst locations on-board to allow
re-orientiong the spacecraft so that the LAT can observe delayed emission from
bright bursts. GBM uses an array of twelve sodium iodide scintillators and two
bismuth germanate scintillators to detect gamma rays from ~8 keV to ~40 MeV
over the full unocculted sky. The on-board trigger threshold is ~0.7
photons/cm2/s (50-300 keV, 1 s peak). GBM generates on-board triggers for ~250
GRBs per year.Comment: 36 pages, 18 figures, to be published in Astrophysical Journa
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