4,434 research outputs found
Flavor versus mass eigenstates in neutrino asymmetries: implications for cosmology
We show that, if they exist, lepton number asymmetries () of
neutrino flavors should be distinguished from the ones () of mass
eigenstates, since Big Bang Nucleosynthesis (BBN) bounds on the flavor
eigenstates cannot be directly applied to the mass eigenstates. Similarly,
Cosmic Microwave Background (CMB) constraints on mass eigenstates do not
directly constrain flavor asymmetries. Due to the difference of mass and flavor
eigenstates, the cosmological constraint on the asymmetries of neutrino flavors
can be much stronger than conventional expectation, but not uniquely determined
unless at least the asymmetry of the heaviest neutrino is well constrained.
Cosmological constraint on for a specific case is presented as an
illustration.Comment: 7 pages, 4 figures, matching to journal versio
On the Spectral Lags and Peak-Counts of the Gamma-Ray Bursts Detected by the RHESSI Satellite
A sample of 427 gamma-ray bursts from a database (February 2002 - April 2008)
of the RHESSI satellite is analyzed statistically. The spectral lags and
peak-count rates, which have been calculated for the first time in this paper,
are studied completing an earlier analysis of durations and hardness ratios.
The analysis of the RHESSI database has already inferred the existence of a
third group with intermediate duration, apart from the so-called short and long
groups. First aim of this article is to discuss the properties of these
intermediate-duration bursts in terms of peak-count rates and spectral lags.
Second aim is to discuss the number of GRB groups using another statistical
method and by employing the peak-count rates and spectral lags as well. The
standard parametric (model-based clustering) and non-parametric (K-means
clustering) statistical tests together with the Kolmogorov-Smirnov and
Anderson-Darling tests are used. Two new results are obtained: A. The
intermediate-duration group has similar properties to the group of short
bursts. Intermediate and long groups appear to be different. B. The
intermediate-duration GRBs in the RHESSI and Swift databases seem to be
represented by different phenomena.Comment: 41 pages, 10 figures, 9 tables, accepted to be published in The
Astrophysical Journa
The Case for Hypercritical Accretion in M33 X-7
The spin parameter of the black hole in M33 X-7 has recently been measured to
be a*=0.77+-0.05 (Liu et al. 2008). It has been proposed that the spin of the
15.65 M_sun black hole is natal. We show that this is not a viable evolutionary
path given the observed binary orbital period of 3.45 days since the explosion
that would produce a black hole with the cited spin parameter and orbital
period would disrupt the binary. Furthermore, we show that the system has to be
evolved through the hypercritical mass transfer of about 5 M_sun from the
secondary star to the black hole.Comment: 4 page
Duplexer using microwave photonic band gap structure
We propose a frequency selective duplexer using microwave photonic band gap (PBG) structures. It uses two different PBGs to control the propagation of electromagnetic waves in the microwave region. In this structure, an additional narrow reflection band appears in the transmission spectrum when the PBG structure is not properly located relative to the T junction. By considering multiple reflections, it is proved that this additional reflection band in each PBG structure results from the interference between the input wave and the reflected wave from the other PBG structure. An effective way to prevent this interference effect is also discussed
Effective action of three-dimensional extended supersymmetric matter on gauge superfield background
We study the low-energy effective actions for gauge superfields induced by
quantum N=2 and N=4 supersymmetric matter fields in three-dimensional Minkowski
space. Analyzing the superconformal invariants in the N=2 superspace we propose
a general form of the N=2 gauge invariant and superconformal effective action.
The leading terms in this action are fixed by the symmetry up to the
coefficients while the higher order terms with respect to the Maxwell field
strength are found up to one arbitrary function of quasi-primary N=2
superfields constructed from the superfield strength and its covariant spinor
derivatives. Then we find this function and the coefficients by direct quantum
computations in the N=2 superspace. The effective action of N=4 gauge multiplet
is obtained by generalizing the N=2 effective action.Comment: 1+27 pages; v2: minor corrections, references adde
Photometric Properties of the Near-contact Binary GW Geminorum
New multiband CCD photometry is presented for the eclipsing binary GW Gem;
the light curves are the first ever compiled. Four new minimum timings
have been determined. Our analysis of eclipse timings observed during the past
79 years indicates a continuous period increase at a fractional rate of
+(1.20.1), in excellent agreement with the value
calculated from the Wilson-Devinney binary code. The new
light curves display an inverse O'Connell effect increasing toward longer
wavelengths. Hot and cool spot models are developed to describe these
variations but we prefer a cool spot on the secondary star. Our light-curve
synthesis reveals that GW Gem is in a semi-detached, but near-contact,
configuration. It appears to consist of a near-main-sequence primary star with
a spectral type of about A7 and an evolved early K-type secondary star that
completely fills its inner Roche lobe. Mass transfer from the secondary to the
primary component is responsible for the observed secular period change.Comment: 20 pages, including 5 figures and 6 tables, accepted for publication
in PAS
The Globular Cluster System of M60 (NGC 4649). I. CFHT MOS Spectroscopy and Database
We present the measurement of radial velocities for globular clusters in M60,
giant elliptical galaxy in the Virgo cluster. Target globular cluster
candidates were selected using the Washington photometry based on the deep
16\arcmin \times 16\arcmin images taken at the KPNO 4m and using the
photometry derived from the HST/WFPC2 archive images. The spectra of the target
objects were obtained using the Multi-Object Spectrograph (MOS) at the
Canada-France-Hawaii Telescope (CFHT). We have measured the radial velocity for
111 objects in the field of M60: 93 globular clusters (72 blue globular
clusters with and 21 red globular clusters with
), 11 foreground stars, 6 small galaxies, and the nucleus of
M60. The measured velocities of the 93 globular clusters range from
km s to km s, with a mean value of
km s, which is in good agreement with the velocity of the nucleus of M60
( km s). Combining our results with data in the
literature, we present a master catalog of radial velocities for 121 globular
clusters in M60. The velocity dispersion of the globular clusters in the master
catalog is found to be km s for the entire sample,
km s for 83 blue globular clusters, and
km s for 38 red globular clusters.Comment: 29 pages, 8 figures. To appear in Ap
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