11,358 research outputs found
Uniting the Quiescent Emission and Burst Spectra of Magnetar Candidates
Spectral studies of quiescent emission and bursts of magnetar candidates
using XMM-Newton, Chandra and Swift data are presented. Spectra of both the
quiescent emission and the bursts for most magnetar candidates are reproduced
by a photoelectrically absorbed two blackbody function (2BB). There is a strong
correlation between lower and higher temperatures of 2BB (kT_LT and kT_HT) for
the magnetar candidates of which the spectra are well reproduced by 2BB. In
addition, a square of radius for kT_T (R_LT^2) is well correlated with a square
of radius for kT_HT (R_HT^2). A ratio kT_LT/kT_HT ~ 0.4 is nearly constant
irrespective of objects and/or emission types (i.e., the quiescent emission and
the bursts). This would imply a common emission mechanism among the magnetar
candidates. The relation between the quiescent emission and the bursts might be
analogous to a relation between microflares and solar flares of the sun. Three
AXPs (4U 0142+614, 1RXS J170849.0-400910 and 1E 2259+586) seem to have an
excess above ~7 keV which well agrees with a non-thermal hard component
discovered by INTEGRAL.Comment: 17 pages, 5 figures, 12 tables, Accepted for publication in PAS
Spectral Comparison of Weak Short Bursts to the Persistent X-rays from the Magnetar 1E 1547.0-5408 in its 2009 Outburst
In January 2009, the 2.1-sec anomalous X-ray pulsar 1E 1547.0-5408 evoked
intense burst activity. A follow-up Suzaku observation on January 28 recorded
enhanced persistent emission both in soft and hard X-rays (Enoto et al. 2010b).
Through re-analysis of the same Suzaku data, 18 short bursts were identified in
the X-ray events recorded by the Hard X-ray Detector (HXD) and the X-ray
Imaging Spectrometer (XIS). Their spectral peaks appear in the HXD-PIN band,
and their 10-70 keV X-ray fluences range from ~2e-9 erg cm-2 to 1e-7 erg cm-2.
Thus, the 18 events define a significantly weaker burst sample than was ever
obtained, ~1e-8-1e-4 erg cm-2. In the ~0.8 to ~300 keV band, the spectra of the
three brightest bursts can be represented successfully by a two-blackbody
model, or a few alternative ones. A spectrum constructed by stacking 13 weaker
short bursts with fluences in the range (0.2-2)e-8 erg s-1 is less curved, and
its ratio to the persistent emission spectrum becomes constant at ~170 above ~8
keV. As a result, the two-blackbody model was able to reproduce the stacked
weaker-burst spectrum only after adding a power-law model, of which the photon
index is fixed at 1.54 as measured is the persistent spectrum. These results
imply a possibility that the spectrum composition employing an optically-thick
component and a hard power-law component can describe wide-band spectra of both
the persistent and weak-burst emissions, despite a difference of their fluxes
by two orders of magnitude. Based on the spectral similarity, a possible
connection between the unresolved short bursts and the persistent emission is
discussed.Comment: 21 pages, 18 figures and 3 tables. Accepted for publication in
Monthly Notices of the Royal Astronomical Society Main Journa
Differences in Canadian and U.S. Farm Structure: What the Canadian Farm Typology Shows
Canadian and U.S. farms vary widely in size and other characteristics, ranging from very small retirement and residential farms to firms with sales in the millions. Agriculture and Agri-Food Canada (AAFC) and the United States Department of Agriculture’s (USDA’s) Economic Research Service (ERS) have each developed a farm typology to classify farms into more homogeneous groups. These typologies provide useful insights into farm structure in each country. It is difficult, however, to use the typologies to compare farm structure in Canada and the United States, because the definitions within the two typologies differ. To make direct comparisons of farm structure in the two countries the Canadian typology was applied to the farms in both nations.Crop Production/Industries, Farm Management,
Thermal noise in half infinite mirrors with non-uniform loss: a slab of excess loss in a half infinite mirror
We calculate the thermal noise in half-infinite mirrors containing a layer of
arbitrary thickness and depth made of excessively lossy material but with the
same elastic material properties as the substrate. For the special case of a
thin lossy layer on the surface of the mirror, the excess noise scales as the
ratio of the coating loss to the substrate loss and as the ratio of the coating
thickness to the laser beam spot size. Assuming a silica substrate with a loss
function of 3x10-8 the coating loss must be less than 3x10-5 for a 6 cm spot
size and a 7 micrometers thick coating to avoid increasing the spectral density
of displacement noise by more than 10%. A similar number is obtained for
sapphire test masses.Comment: Passed LSC (internal) review. Submitted to Phys. Rev. D. (5/2001)
Replacement: Minor typo in Eq. 17 correcte
Time-evolution of Peak Energy and Luminosity Relation within Pulses for GRB 061007: Probing Fireball Dynamics
We perform a time-resolved spectral analysis of bright, long Gamma-ray burst
GRB 061007 using Suzaku/WAM and Swift/BAT. Thanks to the large effective area
of the WAM, we can investigate the time evolution of the spectral peak energy,
Et_peak and the luminosity Lt_iso with 1-sec time resolution, and we find that
luminosity Lt_iso with 1-sec time resolution, and we find that the
time-resolved pulses also satisfy the Epeak-Liso relation, which was found for
the time-averaged spectra of other bursts, suggesting the same physical
conditions in each pulse. Furthermore, the initial rising phase of each pulse
could be an outlier of this relation with higher Et_peak value by about factor
2. This difference could suggest that the fireball radius expands by a factor
of 2-4 and/or bulk Lorentz factor of the fireball is decelerated by a factor of
4 during the initial phase, providing a new probe of the fireball dynamics in
real time.Comment: 21 pages, 16 figures, accepted for publication in PAS
The Suzaku Discovery of A Hard Power-Law Component in the Spectra of Short Bursts from SGR 0501+4516
Using data with the Suzaku XIS and HXD, spectral studies of short bursts from
the soft gamma repeater SGR 0501+4516 were performed. In total, 32 bursts were
detected during the ~60 ks of observation conducted in the 2008 August
activity. Excluding the strongest one, the remaining 31 bursts showed an
average 2--40 keV fluence of 1.0(-0.5,+0.3)*10^-9 erg cm^-2. A 1--40 keV
spectrum summed over them leaves significant positive residuals in the HXD-PIN
band with chi^2/d.o.f. = 74/50, when fitted with a two-blackbody function. By
adding a power law model, the fit became acceptable with chi^2/d.o.f. = 56/48,
yielding a photon index of Gamma=1.0(-0.3,+0.4). This photon index is
comparable to Gamma=1.33(-0.16,+0.23) (Enoto et al. 2010a) for the persistent
emission of the same object obtained with Suzaku. The two-blackbody components
showed very similar ratios, both in the temperature and the emission radii, to
those comprising the persistent emission. However, the power-law to
two-blackbody flux ratio was possibly higher than that of the persistent
emission at 2.6 sigma level. Based on these measurements, average wide-band
properties of these relatively weak bursts are compared with those of the
persistent emission.Comment: 11 pages, 8 figures, 2 tables, Accepted for publication in PASJ
(Suzaku & MAXI special issue
The dynamical transition in proteins and non-Gaussian behavior of low frequency modes in Self Consistent Normal Mode Analysis
Self Consistent Normal Mode Analysis (SCNMA) is applied to heme c type
cytochrome f to study temperature dependent protein motion. Classical Normal
Mode Analysis (NMA) assumes harmonic behavior and the protein Mean Square
Displacement (MSD) has a linear dependence on temperature. This is only
consistent with low temperature experimental results. To connect the protein
vibrational motions between low temperature and physiological temperature, we
have incorporated a fitted set of anharmonic potentials into SCNMA. In
addition, Quantum Harmonic Oscillator (QHO) theory has been used to calculate
the displacement distribution for individual vibrational modes. We find that
the modes involving soft bonds exhibit significant non-Gaussian dynamics at
physiological temperature, which suggests it may be the cause of the
non-Gaussian behavior of the protein motions probed by Elastic Incoherent
Neutron Scattering (EINS). The combined theory displays a dynamical transition
caused by the softening of few "torsional" modes in the low frequency regime (<
50cm-1or 0.6ps). These modes change from Gaussian to a classical
distribution upon heating. Our theory provides an alternative way to understand
the microscopic origin of the protein dynamical transition.Comment: 17 pages, 6 figures, 1 tabl
Axions and the pulsation periods of variable white dwarfs revisited
Axions are the natural consequence of the introduction of the Peccei-Quinn
symmetry to solve the strong CP problem. All the efforts to detect such elusive
particles have failed up to now. Nevertheless, it has been recently shown that
the luminosity function of white dwarfs is best fitted if axions with a mass of
a few meV are included in the evolutionary calculations. Our aim is to show
that variable white dwarfs can provide additional and independent evidence
about the existence of axions. The evolution of a white dwarf is a slow cooling
process that translates into a secular increase of the pulsation periods of
some variable white dwarfs, the so-called DAV and DBV types. Since axions can
freely escape from such stars, their existence would increase the cooling rate
and, consequently, the rate of change of the periods as compared with the
standard ones. The present values of the rate of change of the pulsation period
of G117-B15A are compatible with the existence of axions with the masses
suggested by the luminosity function of white dwarfs, in contrast with previous
estimations. Furthermore, it is shown that if such axions indeed exist, the
drift of the periods of pulsation of DBV stars would be noticeably perturbed.Comment: Accepted for publication in Astronomy & Astrophysic
Suzaku Discovery of a Hard X-Ray Tail in the Persistent Spectra from the Magnetar 1E 1547.0-5408 during its 2009 Activity
The fastest-rotating magnetar 1E 1547.0-5408 was observed in broad-band
X-rays with Suzaku for 33 ks on 2009 January 28-29, 7 days after the onset of
its latest bursting activity. After removing burst events, the
absorption-uncorrected 2-10 keV flux of the persistent emission was measured
with the XIS as 5.7e-11 ergs cm-2 s-1, which is 1-2 orders of magnitude higher
than was measured in 2006 and 2007 when the source was less active. The
persistent emission was also detected significantly with the HXD in >10 keV up
to at least ~110 keV, with an even higher flux of 1.3e-10 ergs cm-2 s-1 in
20-100 keV. The pulsation was detected at least up to 70 keV at a period of
2.072135+/-0.00005 s, with a deeper modulation than was measured in a fainter
state. The phase-averaged 0.7-114 keV spectrum was reproduced by an absorbed
blackbody emission with a temperature of 0.65+/-0.02 keV, plus a hard power-law
with a photon index of ~1.5. At a distance of 9 kpc, the bolometric luminosity
of the blackbody and the 2-100 keV luminosity of the hard power-law are
estimated as (6.2+/-1.2)e+35 ergs s-1 and 1.9e+36 ergs s-1, respectively, while
the blackbody radius becomes ~5 km. Although the source had not been detected
significantly in hard X-rays during the past fainter states, a comparison of
the present and past spectra in energies below 10 keV suggests that the hard
component is more enhanced than the soft X-ray component during the persistent
activity.Comment: 12 pages, 7 figures, PASJ Vol.62 No.2 accepte
The S shape of a granular pile in a rotating drum
The shape of a granular pile in a rotating drum is investigated. Using
Discrete Elements Method (DEM) simulations we show that the "S shape" obtained
for high rotation speed can be accounted for by the friction on the end plates.
A theoretical model which accounts for the effect of the end plates is
presented and the equation of the shape of the free surface is derived. The
model reveals a dimensionless number which quantifies the influence of the end
plates on the shape of the pile. Finally, the scaling laws of the system are
discussed and numerical results support our conclusions
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