32,637 research outputs found
Broad-line and Multi-wave Band Emission from Blazars
We study the correlations of the flux of the broad-line emission ()
with the X-ray emission flux, optical emission flux at 5500 \AA and radio
emission flux at 5 GHz, respectively, for a large sample of 50 Blazars (39
flat-spectrum radio quasars (FSRQs) and 11 BL Lac objects). Our main results
are as follows. There are very strong correlations between and
and between and in both states for 39 FSRQs and the
slopes of the linear regression equations are almost equal to 1. There are weak
correlations between and and between and
for 11 BL Lac objects in both states, and the slopes of the linear regression
equations are close to 1. There are significant correlations between
and and between and for 50 blazars in both states,
the slopes of both the linear regression equations are also close to 1. These
results support a close link between relativistic jets and accretion on to the
central Kerr black hole. On the other hand, we find that BL Lac objects have
low accretion efficiency , whereas FSRQs have high accretion efficiency
. The unified model of FSRQs and BL Lac objects is also discussed.Comment: 15 pages, 8 figure
Distinguishing RBL-like objects and XBL-like objects with the peak emission frequency of the overall energy spectrum
We investigate quantitatively how the peak emission frequency of the overall
energy spectrum is at work in distinguishing RBL-like and XBL-like objects. We
employ the sample of Giommi et al. (1995) to study the distribution of BL
Lacertae objects with various locations of the cutoff of the overall energy
spectrum. We find that the sources with the cutoff located at lower frequency
are indeed sited in the RBL region of the plane,
while those with the cutoff located at higher frequency are distributed in the
XBL region. For a more quantitative study, we employ the BL Lacertae samples
presented by Sambruna et al. (1996), where, the peak emission frequency, , of each source is estimated by fitting the data with a parabolic function.
In the plot of we find that, in the four different
regions divided by the line and the line,
all the RBL-like objects are inside the upper left region, while most XBL-like
objects are within the lower right region. A few sources are located in the
lower left region. No sources are in the upper right region. This result is
rather quantitative. It provides an evidence supporting what Giommi et al.
(1995) suggested: RBL-like and XBL-like objects can be distinguished by the
difference of the peak emission frequency of the overall energy spectrum.Comment: 7 pages, 2 figure
The long-term optical behavior of MRK421
All data available in B band for the BL Lac object MRK421 from 22
publications are used to construct a historical light curve, dating back to
1900. It is found that the light curve is very complicated and consists of a
set of outbursts with very large duration. The brightness of MRK421 varies from
11.6 magnitude to more than 16 magnitude. Analyses with Jurkevich method of
computing period of cyclic phenomena reveal in the light curve two kinds of
behaviors. The first one is non-periodic with rapid, violent variations in
intensity on time scales of hours to days. The second one is periodic with a
possible period of years. Another possible period of years is not very significant. We have tested the robustness of the
Jurkevich method. The period of about one year found in the light curves of
MRK421 and of other objects is a spurious period due to the method and the
observing window. We try to explain the period of years under the
thermal instability of a slim accretion disk around a massive black hole of
mass of .Comment: Tex, 14 pages, 5 Postscript figures. Accepted for publication in A&A
Supplement Serie
Production rates for hadrons, pentaquarks and , and di-baryon in relativistic heavy ion collisions by a quark combination model
The hadron production in relativistic heavy ion collisions is well described
by the quark combination model. The mixed ratios for various hadrons and the
transverse momentum spectra for long-life hadrons are predicted and agree with
recent RHIC data. The production rates for the pentaquarks , and the di-baryon are estimated, neglecting
the effect from the transition amplitude for constituent quarks to form an
exotic state.Comment: The difference between our model and other combination models is
clarified. The scaled transverse momentum spectra for pions, kaons and
protoms at both 130 AGeV and 200 AGeV are given, replacing the previous
results in transverse momentum spectr
CMS Offline Conditions Framework and Services
Non-event data describing detector conditions change with time and come from different data sources. They are accessible by physicists within the offline event-processing applications for precise calibration of reconstructed data as well as for data-quality control purposes. Over the past years CMS has developed and deployed a software system managing such data. Object-relational mapping and the relational abstraction layer of the LHC persistency framework are the foundation; the offline conditions framework updates and delivers C++ data objects according to their validity. A high-level tag versioning system allows production managers to organize data in hierarchical view. A scripting API in python, command-line tools and a web service serve physicists in daily work. A mini-framework is available for handling data coming from external sources. Efficient data distribution over the worldwide network is guaranteed by a system of hierarchical web caches. The system has been tested and used in all major productions, test-beams and cosmic runs
A statistical model approximation for perovskite solid-solutions: a Raman study of lead-zirconate-titanate single crystal
Lead titanate (PbTiO3) is a classical example of a ferroelectric perovskite
oxide illustrating a displacive phase transition accompanied by a softening of
a symmetry-breaking mode. The underlying assumption justifying the soft-mode
theory is that the crystal is macroscopically sufficiently uniform so that a
meaningful free energy function can be formed. In contrast to PbTiO3,
experimental studies show that the phase transition behaviour of
lead-zirconate-titanate solid solution (PZT) is far more subtle. Most of the
studies on the PZT system have been dedicated to ceramic or powder samples, in
which case an unambiguous soft-mode study is not possible, as modes with
different symmetries appear together. Our Raman scattering study on
titanium-rich PZT single crystal shows that the phase transitions in PZT cannot
be described by a simple soft-mode theory. In strong contrast to PbTiO3,
splitting of transverse E-symmetry modes reveals that there are different
locally-ordered regions. The role of crystal defects, random distribution of Ti
and Zr at the B-cation site and Pb ions shifted away from their ideal
positions, dictates the phase transition mechanism. A statistical model
explaining the observed peak splitting and phase transformation to a complex
state with spatially varying local order in the vicinity of the morphotropic
phase boundary is given.Comment: Article contains four black-and-white figures, one colour figure and
one Table. Symmetry analysis and details of the model are given in Appendices
I and II, respectivel
Historic Light Curve and Long-term Optical Variation of BL Lacertae 2200+420
In this paper, historical optical(UBVRI) data and newly observed data from
the Yunnan Observatory of China(about100 years) are presented for BL Lacertae.
Maximum variations in UBVRI: 5.12, 5.31, 4.73, 2.59, and 2.54 and color indices
of U-B = -0.11 +/- 0.20, B-V= 1.0 +/- 0.11, V-R= 0.73 +/- 0.19, V-I= 1.42 +/-
0.25, R-I= 0.82 +/- 0.11, and B-I= 2.44 +/- 0.29 have been obtained from the
literature; The Jurkevich method is used to investigate the existence of
periods in the B band light curve, and a long-term period of 14 years is found.
The 0.6 and 0.88 year periods reported by Webb et al.(1988) are confirmed. In
addition, a close relation between B-I and B is found, suggesting that the
spectra flattens when the source brightens.Comment: 21 pages, 6 figures, 2 table, aasms4.sty, to be published in ApJ,
Vol. 507, 199
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