966 research outputs found
The near-synchronous polar V1432 Aql (RX J1940.1-1025): Accretion geometry and synchronization time scale
The magnetic Cataclysmic Variable (mCV) V1432 Aql (RX 1940.1-1025) belongs to
the four-member subclass of near-synchronous polars with a slight
non-synchronism (<2 %) between the spin period of the white dwarf and the
binary period. In these systems the accretion geometry changes periodically
with phase of the beat cycle. We present the application of a dipole accretion
model for near-synchronous systems developed by Geckeler & Staubert (1997a) to
extended optical and X-ray data. We detect a significant secular change of the
white dwarf spin period in V1432 Aql of dP_spin/dt = -5.4 (+3.7/-3.2) 10-9 s/s
from the optical data set alone. This corresponds to a synchronization time
scale tau_sync = 199 (+441/-75) yr, comparable to the time scale of 170 yr for
V1500 Cyg. The synchronization time scale in V1432 Aql is in excellent
agreement with the theoretical prediction from the dominating magnetic torque
in near-synchronous systems. We also present period analyses of optical CCD
photometry and RXTE X-ray data, which argue against the existence of a 4000 s
period and an interpretation of V1432 Aql as an intermediate polar. The dipole
accretion model also allows to constrain the relevant parameters of the
accretion geometry in this system: the optical data allow an estimate of the
dimensionless parameter (R_t0'/R_wd)1/2 sin(beta) = 3.6 (+2.7/-1.1), with a
lower limit for the threading radius of R_t0' > 10 R_wd (68% confidence).Comment: 12 pages, 10 figures, 6 tables accepted by A&
Different kinds of long-term variability from Cygnus X-1
We present a study of the long-term variability of Cyg X-1 using data from
the RXTE/ASM and the RXTE/PCA during the time between the two soft states of
1996 and 2001/2002. This period has been characterized by many short ASM
flaring episodes which we have identified as "failed state transitions". The
150 d period which has been seen before and shortly after the 1996 soft state
is not obviously present in the ASM rate during most of this time. Applying
selection criteria from our pointed RXTE/PCA observations to exclude the
flaring episodes we show that the 150 d period can indeed still be
significantly detected in the hard state. Furthermore, while the ~420 d
timescale associated with the flaring is reduced in the selected hard state
count rate, it is still pronounced in the temporal evolution of the
corresponding hardness ratios. The Ryle radio flux is also consistent with the
150 d period being present but distorted during this time.Comment: 4 pages, 6 figures, to appear in Proceedings of "X-ray Timing 2003:
Rossi and Beyond", ed. P. Kaaret, F.K. Lamb, & J.H. Swan
Evaluación de variables biomecánicas tras la recepción en colchonetas y su relación con los criterios mecánicos de la normativa
Estudio de las presiones plantares en gimnasia y su relación con las propiedades percibidas durante la recepción en colchonetas
Non-critically squeezed light via spontaneous rotational symmetry breaking
We theoretically address squeezed light generation through the spontaneous
breaking of the rotational invariance occuring in a type I degenerate optical
parametric oscillator (DOPO) pumped above threshold. We show that a DOPO with
spherical mirrors, in which the signal and idler fields correspond to first
order Laguerre-Gauss modes, produces a perfectly squeezed vacuum with the shape
of a Hermite-Gauss mode, within the linearized theory. This occurs at any
pumping level above threshold, hence the phenomenon is non-critical.
Imperfections of the rotational symmetry, due e.g. to cavity anisotropy, are
shown to have a small impact, hence the result is not singular.Comment: 4 pages, 1 figure, replaced with resubmitted versio
Development of Thick-foil and Fine-pitch GEMs with a Laser Etching Technique
We have produced thick-foil and fine-pitch gas electron multipliers (GEMs)
using a laser etching technique. To improve production yield we have employed a
new material, Liquid Crystal Polymer, instead of polyimide as an insulator
layer. The effective gain of the thick-foil GEM with a hole pitch of 140 um, a
hole diameter of 70 um, and a thickness of 100 um reached a value of 10^4 at an
applied voltage of 720 V. The measured effective gain of the thick-foil and
fine-pitch GEM (80 um pitch, 40 um diameter, and 100 um thick) was similar to
that of the thick-foil GEM. The gain stability was measured for the thick-foil
and fine-pitch GEM, showing no significant increase or decrease as a function
of elapsed time from applying the high voltage. The gain stability over 3 h of
operation was about 0.5%. Gain mapping across the GEM showed a good uniformity
with a standard deviation of about 4%. The distribution of hole diameters
across the GEM was homogeneous with a standard deviation of about 3%. There was
no clear correlation between the gain and hole diameter maps.Comment: 21 pages, 9 figure
Quantum coherent control of highly multipartite continuous-variable entangled states by tailoring parametric interactions
The generation of continuous-variable multipartite entangled states is
important for several protocols of quantum information processing and
communication, such as one-way quantum computation or controlled dense coding.
In this article we theoretically show that multimode optical parametric
oscillators can produce a great variety of such states by an appropriate
control of the parametric interaction, what we accomplish by tailoring either
the spatio-temporal shape of the pump, or the geometry of the nonlinear medium.
Specific examples involving currently available optical parametric oscillators
are given, hence showing that our ideas are within reach of present technology.Comment: 14 pages, 5 figure
A new luminous supersoft X-ray source in NGC 300
Context. We report the discovery of a new luminous supersoft source, XMMU J005455.0−374117, in the nearby spiral galaxy GC 300, in XMM-Newton observations performed on 2005 May 22 and on 2005 November 25. The source is not present in ROSAT data nor in the previous XMM-Newton observations of 2000 December/2001 January. The unique luminous supersoft source,XMMU J005510.7−373855, detected in the 1992 May/June ROSAT data and in the 2000/2001 XMM-Newton data, fell below detectability. This source already appeared highly variable in ROSAT observations.
Aims. We report on the temporal and spectral analysis of this new supersoft source (SSS) and compare its properties with the previous known SSS.
Methods. We present the light curves of the SSS, model its spectrum and estimate the corresponding flux and luminosities.
Results. The light curve of XMMU J005455.0−374117 does not show large fluctuations in any of the observations and its spectrum can be modelled with an absorbed blackbody with kT ∼ 60 eV. The corresponding bolometric luminosity is 8.1+1.4
−4.5 × 1038 erg s−1 in the first observation and drops to 2.2+0.5 −1.4 × 1038 erg s−1 six months later. No optical source brighter than mV ∼ 21.7 mag is found coincident with its position.
Conclusions. The luminosity of these two SSSs is higher than what has been found for “classical” SSSs. Their nature could be explained by beamed emission from steady nuclear burning of hydrogen onto white dwarfs, or accretion onto stellar-mass black hole with matter outflow or observed at high inclination angle. The presence of an intermediate-mass black hole seems unlikely in our case
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