2,001 research outputs found
Coronal--Temporal Correlations in GX339-4: Hysteresis, Possible Reflection Changes, and Implications for ADAFs
We present spectral fits and timing analysis of Rossi X-ray Timing Explorer
observations of GX339-4. These observations were carried out over a span of
more than two years and encompassed both the soft/high and hard/low states.
Hysteresis in the soft state/hard state transition is observed. The hard state
exhibits a possible anti-correlation between coronal compactness (i.e.,
spectral hardness) and the covering fraction of cold, reflecting material. The
correlation between `reflection fraction' and soft X-ray flux, however, appears
to be more universal. Furthermore, low flux, hard state observations - taken
over a decline into quiescence- show that the Fe line, independent of
`reflection fraction', remains broad and at a roughly constant equivalent
width, counter to expectations from ADAF models. All power spectral densities
(PSD) of the hard state X-ray lightcurves are describable as the sum of just a
few broad, quasi-periodic features with frequencies that roughly scale as
coronal compactness to the -3/2 power. Similar to observations of Cyg X-1, time
lags between soft and hard variability anti-correlate with coronal compactness.
A stronger correlation is seen between the time lags and the `reflection
fraction'.Comment: 29 Pages, 17 Figures, 6 Tables. Accepted for Publication in MNRAS.
(Abstract Abridged
Running Neutrino Mass Parameters in See-Saw Scenarios
We systematically analyze quantum corrections in see-saw scenarios, including
effects from above the see-saw scales. We derive approximate renormalization
group equations for neutrino masses, lepton mixings and CP phases, yielding an
analytic understanding and a simple estimate of the size of the effects. Even
for hierarchical masses, they often exceed the precision of future experiments.
Furthermore, we provide a software package allowing for a convenient numerical
renormalization group analysis, with heavy singlets being integrated out
successively at their mass thresholds. We also discuss applications to model
building and related topics.Comment: 49 pages, 9 figures; minor corrections in Sec. 6.5.1; the
accompanying software packages REAP/MPT can be downloaded from
http://www.ph.tum.de/~rg
The LMA Solution from Bimaximal Lepton Mixing at the GUT Scale by Renormalization Group Running
We show that in see-saw models with bimaximal lepton mixing at the GUT scale
and with zero CP phases, the solar mixing angle theta_{12} generically evolves
towards sizably smaller values due to Renormalization Group effects, whereas
the evolution of theta_{13} and theta_{23} is comparatively small. The
currently favored LMA solution of the solar neutrino problem can thus be
obtained in a natural way from bimaximal mixing at the GUT scale. We present
numerical examples for the evolution of the leptonic mixing angles in the
Standard Model and the MSSM, in which the current best-fit values of the LMA
mixing angles are produced. These include a case where the mass eigenstates
corresponding to the solar mass squared difference have opposite CP parity.Comment: 14 pages, 10 figures; references and a subsection containing an
example with odd CP parities added; results and conclusions unchange
Neutrino Mass Operator Renormalization in Two Higgs Doublet Models and the MSSM
In a recent re-analysis of the Standard Model (SM) beta-function for the
effective neutrino mass operator, we found that the previous results were not
entirely correct. Therefore, we consider the analogous dimension five operators
in a class of Two Higgs Doublet Models (2HDM's) and the Minimal Supersymmetric
Standard Model (MSSM). Deriving the renormalization group equations for these
effective operators, we confirm the existing result in the case of the MSSM.
Some of our 2HDM results are new, while others differ from earlier
calculations. This leads to modifications in the renormalization group
evolution of leptonic mixing angles and CP phases in the 2HDM's.Comment: 8 pages, 18 eps figure
The column density towards LMC X-1
We measure the neutral absorption towards the black hole X-ray binary system
LMC X-1 from six archival soft X-ray spectra obtained with the gratings and/or
CCD detectors on Chandra, XMM-Newton, and Swift. Four spectral models for the
soft continuum have been investigated. While the powerlaw model may
overestimate NH considerably, the others give consistent results. Taking the
lower metalicity of the Large Magellanic Cloud into account, we find equivalent
hydrogen column densities of N_H = (1.0-1.3)*10^22 cm^-2, with a systematic
dependence on the orbital phase. This variation of the neutral absorption can
nearly explain the orbital modulation of the soft X-ray flux recently detected
with the All Sky Monitor (ASM) on the Rossi X-ray Timing Explorer (RXTE).Comment: 4 pages, accepted for publication as a Letter in Astronomy and
Astrophysic
Low Luminosity States of the Black Hole Candidate GX 339-4. I. ASCA and Simultaneous Radio/RXTE Observations
We discuss a series of observations of the black hole candidate GX 339-4 in
low luminosity, spectrally hard states. We present spectral analysis of three
separate archival Advanced Satellite for Cosmology and Astrophysics (ASCA) data
sets and eight separate Rossi X-ray Timing Explorer (RXTE) data sets. Three of
the RXTE observations were strictly simultaneous with 843 MHz and 8.3-9.1 GHz
radio observations. All of these observations have (3-9 keV) flux approximately
< 10^{-9} ergs s^{-1} cm^{-2}. The ASCA data show evidence for an 6.4 keV Fe
line with equivalent width 40 eV, as well as evidence for a soft excess that is
well-modeled by a power law plus a multicolor blackbody spectrum with peak
temperature 150-200 eV. The RXTE data sets also show evidence of an Fe line
with equivalent widths 20-140 eV. Reflection models show a hardening of the
RXTE spectra with decreasing X-ray flux; however, these models do not exhibit
evidence of a correlation between the photon index of the incident power law
flux and the solid angle subtended by the reflector. `Sphere+disk'
Comptonization models and Advection Dominated Accretion Flow (ADAF) models also
provide reasonable descriptions of the RXTE data. The former models yield
coronal temperatures in the range 20-50 keV and optical depths of \tau ~ 3. The
model fits to the X-ray data, however, do not simultaneously explain the
observed radio properties. The most likely source of the radio flux is
synchrotron emission from an extended outflow of size greater than O(10^7
GM/c^2).Comment: 18 pages in latex emulateapj.sty. Accepted for publication in the
Astrophysical Journa
RXTE Observation of Cygnus X-1: II. Timing Analysis
We present timing analysis for a Rossi X-ray Timing Explorer observation of
Cygnus X-1 in its hard/low state. This was the first RXTE observation of Cyg
X-1 taken after it transited back to this state from its soft/high state.
RXTE's large effective area, superior timing capabilities, and ability to
obtain long, uninterrupted observations have allowed us to obtain measurements
of the power spectral density (PSD), coherence function, and Fourier time lags
to a decade lower in frequency and half a decade higher in frequency than
typically was achieved with previous instruments. Notable aspects of our
observations include a weak 0.005 Hz feature in the PSD coincident with a
coherence recovery; a `hardening' of the high-frequency PSD with increasing
energy; a broad frequency range measurement of the coherence function,
revealing rollovers from unity coherence at both low and high frequency; and an
accurate determination of the Fourier time lags over two and a half decades in
frequency. As has been noted in previous similar observations, the time delay
is approximately proportional to f^(-0.7), and at a fixed Fourier frequency the
time delay of the hard X-rays compared to the softest energy channel tends to
increase logarithmically with energy. Curiously, the 0.01-0.2 Hz coherence
between the highest and lowest energy bands is actually slightly greater than
the coherence between the second highest and lowest energy bands. We carefully
describe all of the analysis techniques used in this paper, and we make
comparisons of the data to general theoretical expectations. In a companion
paper, we make specific comparisons to a Compton corona model that we have
successfully used to describe the energy spectral data from this observation.Comment: To Be Published in the Astrophysical Journal. 18 pages. Uses
emulatepaj.st
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