2,269 research outputs found
Three-Flavour Neutrino-Mixing Implications of the LSND Result
The LSND result is shown to fit into a minimal three-flavour neutrino-mixing
scenario capable of describing all known experimental facts provided the large
Delta M^2 = m_3^2 - m_2^2 \sim m_3^2 - m_1^2 lies in the range 2.5 x 10^{-1} <
Delta M^2 < 3.0 eV^2. In this range the value of P_{\mu\tau} is expected to be
about 5% or larger.Comment: 10 pages, 2 eps figures, LaTeX 2.09, revised for Physics Letters
MSW mediated neutrino decay and the solar neutrino problem
We investigate the solar neutrino problem assuming simultaneous presence of
MSW transitions in the sun and neutrino decay on the way from sun to earth. We
do a global -analysis of the data on total rates in Cl, Ga and
Superkamiokande (SK) experiments and the SK day-night spectrum data and
determine the changes in the allowed region in the \dm - \tan^2\theta plane
in presence of decay. We also discuss the implications for unstable neutrinos
in the SNO experiment.Comment: Final version to appear in Phys. Rev.
Spectral variability of planetary nebulae and related objects
The results of long-term spectral observations were used to search for
changes in planetary nebulae and emission-line stars. Significant increase of
excitation degree is found in two objects: M1-6 and M1-11
Neutrino Anomalies without Oscillations
I review explanations for the three neutrino anomalies (solar, atmospheric
and LSND) which go beyond the ``conventional'' neutrino oscillations induced by
mass-mixing. Several of these require non-zero neutrino masses as well.Comment: 14pages, LATEX format, 3 figure
The true nature of the alleged planetary nebula W16-185
We report the discovery of a small cluster of massive stars embedded in a NIR
nebula in the direction of the IRAS15411-5352 point source, which is related to
the alleged planetary nebula W16-185. The majority of the stars present large
NIR excess characteristic of young stellar objects and have bright counterparts
in the Spitzer IRAC images; the most luminous star (IRS1) is the NIR
counterpart of the IRAS source. We found very strong unresolved Brgamma
emission at the IRS1 position and more diluted and extended emission across the
continuum nebula. From the sizes and electron volume densities we concluded
that they represent ultra-compact and compact HII regions, respectively.
Comparing the Brgamma emission with the 7 mm free-free emission, we estimated
that the visual extinction ranges between 14 and 20 mag. We found that only one
star (IRS1) can provide the number of UV photons necessary to ionize the
nebula.Comment: 30 pages, 15 figures, 2 tables V3: minor grammatical changes. Figure
4 is available in pdf file. Accepted for publication in AJ, April / 200
Neutrino Lasing in the Sun
Applying the phenomenon of neutrino lasing in the solar interior, we show how
the rate for the generic neutrino decay process `\nu -> fermion + boson', can
in principal be enhanced by many orders of magnitude over its normal decay
rate. Such a large enhancement could be of import to neutrino-decay models
invoked in response to the apparent deficit of electron neutrinos observed from
the sun. The significance of this result to such models depends on the specific
form of the neutrino decay, and the particle model within which it is embedded.Comment: 12 pages, using ordinary TeX. No figure
Investigating on the nuclear obscuration in two types of Seyfert 2 galaxies
We build a large sample of Seyfert 2 galaxies (Sy2s) with both optical
spectropolarimetric and X-ray data available, in which 29 Sy2s with the
detection of polarized broad emission line (PBL) and 25 without. We find that
for luminous Sy2s with L_[OIII] > 10^41 erg/s, sources with PBL have smaller
X-ray absorption column density comparing with those without PBL (at 92.3%
confidence level): most of the Sy2s with N_H<10^23.8 cm^-2 show PBL (86%, 12
out 14), while the fraction is much smaller for sources with heavier
obscuration (54%, 15 out 28). The confidence level of the difference in
absorption bounces up to 99.1% while using the "T" ratio (F_2-10keV/F_[O III])
as an indicator. We rule out observation or selection bias as the origin for
the difference. Our results, for the first time with high statistical
confidence, show that, in additional to the nuclei activity, the nuclear
obscuration also plays an important role in the visibility of PBL in Sy2s.
These results can be interpreted in the framework of the unified model. We can
reach these results in the unified model if: a) the absorption column density
is higher at large inclinations and b) the scattering region is obscured at
large inclinations.Comment: 28 pages, including 7 figures and 3 tables, ApJ accepte
Morpho-kinematic analysis of the point-symmetric, bipolar planetary nebulae Hb 5 and K 3-17, a pathway to poly-polarity
The kinematics of the bipolar planetary nebulae Hb~5 and K 3-17 are
investigated in detail by means of a comprehensive set of spatially resolved
high spectral resolution, long-slit spectra. Both objects share particularly
interesting characteristics, such as a complex filamentary, rosette-type
nucleus, axial point-symmetry and very fast bipolar outflows. The kinematic
information of Hb~5 is combined with {\it HST} imagery to construct a detailed
3D model of the nebula using the code SHAPE. The model shows that the large
scale lobes are growing in a non-homologous way. The filamentary loops in the
core are proven to actually be secondary lobes emerging from what appears to be
a randomly punctured, dense, gaseous core and the material that forms the point
symmetric structure flows within the lobes with a distinct kinematic pattern
and its interaction with the lobes has had a shaping effect on them. Hb~5 and
K~3-17 may represent a class of fast evolving planetary nebulae that will
develop poly-polar characteristics once the nebular core evolves and expands.Comment: 19 pages, 8 figures. To appear in The Astrophysical Journa
A Common Explanation for the Atmospheric, Solar-Neutrino and Double Beta Decay Anomalies
We make a number of small changes, including correcting an error in our
heavy-neutrino decay rate. None of our analysis is changed, either in substance
or detail.Comment: 25 pages, 6 Figures, McGill-93/1
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