10,521 research outputs found
V405 Aurigae: A High Magnetic Field Intermediate Polar
Our simultaneous multicolor (UBVRI) circular polarimetry has revealed nearly
sinusoidal variation over the WD spin cycle, and almost symmetric positive and
negative polarization excursions. Maximum amplitudes are observed in the B and
V bands (+-3 %). This is the first time that polarization peaking in the blue
has been discovered in an IP, and suggests that V405 Aur is the highest
magnetic field IP found so far. The polarized flux spectrum is similar to those
found in polars with magnetic fields in the range B ~ 25-50 MG. Our low
resolution circular spectropolarimetry has given evidence of transient features
which can be fitted by cyclotron harmonics n = 6, 7, and 8, at a field of B =
31.5 +- 0.8 MG, consistent with the broad-band polarized flux spectrum. Timings
of the circular polarization zero crossovers put strict upper limits on WD spin
period changes and indicate that the WD in V405 Aur is currently accreting
closely at the spin equilibrium rate, with very long synchronization
timescales, T_s > 10^9 yr. For the observed spin to orbital period ratio,
P_{spin}/P_{orb} = 0.0365, and P_{orb} ~ 4.15 hr, existing numerical accretion
models predict spin equilibrium condition with B ~ 30 MG if the mass ratio of
the binary components is q_1 ~ 0.4. The high magnetic field makes V405 Aur a
likely candidate as a progenitor of a polar.Comment: To appear in The Astrophysical Journal, September 1 Issue (2008), 9
pages, 10 figure
Process Combination of VPP-LED and Vacuum Die Casting for Producing Complex Ceramic 3D-MID
Future developments lead to increasing demands on mechatronic integrated devices (MID). Therefore, ceramics have to be used as substrate material and conductor tracks have to be located in the interior of components to be sufficiently protected. A process combination of vat photopolymerization (VPP-LED) and vacuum die casting is investigated for realizing such structures. First, optimized process parameters are derived by studying the filling behavior of straight capillaries. Subsequently, the results are transferred to complex additively manufactured substrates to derive design guidelines
A New Analysis Method for Simulations Using Node Categorizations
Most research concerning the influence of network structure on phenomena
taking place on the network focus on relationships between global statistics of
the network structure and characteristic properties of those phenomena, even
though local structure has a significant effect on the dynamics of some
phenomena. In the present paper, we propose a new analysis method for phenomena
on networks based on a categorization of nodes. First, local statistics such as
the average path length and the clustering coefficient for a node are
calculated and assigned to the respective node. Then, the nodes are categorized
using the self-organizing map (SOM) algorithm. Characteristic properties of the
phenomena of interest are visualized for each category of nodes. The validity
of our method is demonstrated using the results of two simulation models. The
proposed method is useful as a research tool to understand the behavior of
networks, in particular, for the large-scale networks that existing
visualization techniques cannot work well.Comment: 9 pages, 8 figures. This paper will be published in Social Network
Analysis and Mining(www.springerlink.com
Higher order effects in the and transfer reactions
Full Coupled Channels Calculations were performed for the
and transfer reactions at several deuteron incident
energies from MeV up to 3.27 MeV. A strong polarization effect
between the entrance channel and the transfer channels
and was
observed. This polarization effect had to be taken into account in order to
obtain realistic spectroscopic factors from these reactions.Comment: 15 papes, 13 figures, accepted for publication in Phys. Rev.
Photometric study of selected cataclysmic variables
We present time-resolved photometry of five relatively poorly-studied
cataclysmic variables: V1193 Ori, LQ Peg, LD 317, V795 Her, and MCT 2347-3144.
The observations were made using four 1m-class telescopes for a total of more
than 250 h of observation and almost 16,000 data points. For LQ Peg WHT
spectroscopic data have been analysed as well.
The light curves show a wide range of variability on different time scales
from minutes to months. We detect for the first time a brightness variation of
0.05 mag in amplitude in V1193 Ori on the same timescale as the orbital period,
which we interpret as the result of the irradiation of the secondary. A 20-min
quasi-periodic oscillation is also detected. The mean brightness of the system
has changed by 0.5 mag on a three-month interval, while the flickering was
halved. In LQ Peg a 0.05 mag modulation was revealed with a period of about 3
h. The flickering was much smaller, of the order of 0.025 mag. A possible
quasi-periodic oscillation could exist near 30 min. For this object, the WHT
spectra are single-peaked and do not show any radial-velocity variations. The
data of LD 317 show a decrease in the mean magnitude of the system. No periodic
signal was detected but this is certainly attributable to the very large
flickering observed: between 0.07 and 0.1 mag. For V795 Her, the 2.8-hour
modulation, thought to be a superhump arising from the precession of the disc,
is present. We show that this modulation is not stable in terms of periodicity,
amplitude, and phase. Finally, for MCT 2347-3144, a clear modulation is seen in
a first dataset obtained in October 2002. This modulation is absent in August
2003, when the system was brighter and showed much more flickering.Comment: 19 pages, 15 figures, 7 tables. Accepted for pubication by A&
Geometrical Constraints on the Cosmological Constant
The cosmological constant problem is examined under the assumption that the
extrinsic curvature of the space-time contributes to the vacuum. A compensation
mechanism based on a variable cosmological term is proposed. Under a suitable
hypothesis on the behavior of the extrinsic curvature, we find that an
initially large rolls down rapidly to zero during the early stages
of the universe. Using perturbation analysis, it is shown that such vacuum
behaves essentially as a spin-2 field which is independent of the metric.Comment: [email protected], 17 pages, Latex, 2 figures obtained by reques
Observations of the SW Sextantis star DW Ursae Majoris with the Far Ultraviolet Spectroscopic Explorer
We present an analysis of the first far-ultraviolet observations of the SW
Sextantis-type cataclysmic variable DW Ursae Majoris, obtained in November 2001
with the Far Ultraviolet Spectroscopic Explorer. The time-averaged spectrum of
DW UMa shows a rich assortment of emission lines (plus some contamination from
interstellar absorption lines including molecular hydrogen). Accretion disk
model spectra do not provide an adequate fit to the far-ultraviolet spectrum of
DW UMa. We constructed a light curve by summing far-ultraviolet spectra
extracted in 60-sec bins; this shows a modulation on the orbital period, with a
maximum near photometric phase 0.93 and a minimum half an orbit later. No other
periodic variability was found in the light curve data. We also extracted
spectra in bins spanning 0.1 in orbital phase; these show substantial variation
in the profile shapes and velocity shifts of the emission lines during an
orbital cycle of DW UMa. Finally, we discuss possible physical models that can
qualitatively account for the observed far-ultraviolet behavior of DW UMa, in
the context of recent observational evidence for the presence of a
self-occulting disk in DW UMa and the possibility that the SW Sex stars may be
the intermediate polars with the highest mass transfer rates and/or weakest
magnetic fields.Comment: accepted by the Astronomical Journal; 36 pages, including 12 figures
and 4 table
Conformally coupled dark matter
Dark matter is obtained from a scalar field coupled conformally to
gravitation; the scalar being a relict of Dirac's gauge function. This
conformally coupled dark matter includes a gas of very light () neutral bosons having spin 0, as well as a
time-dependent global scalar field, both pervading all of the cosmic space. The
time-development of this dark matter in the expanding F-R-W universe is
investigated, and an acceptable cosmological behaviour is obtained.Comment: LaTEX File 10 pages, no figure
Status of the Solar Neutrino Puzzle
Using the latest results from the solar neutrino experiments and a few
standard assumptions, I show that the popular solar models are ruled out at the
3 level or at least TWO of the experiments are incorrect.
Alternatively, one of the assumptions could be in error. These assumptions are
spelled out in detail as well as how each one affects the argument.Comment: Latex, 8 pages + 4 uuencoded figures, minor changes made,
FERMILAB-PUB/273-
- …