158 research outputs found
Variation of fluxes of RR Tel emission lines measured in 2000 with respect to 1996
The aim of this work is to make available unpublished non-Fe+ emission line
fluxes from optical spectra of the symbiotic nova RR Tel which were taken in
2000, and to compare them with fluxes of the same lines from spectra taken in
1996. After leaving out blends and misidentifications, as well as the
unreliable far-red and violet lines, we present the log (F2000/F1996) flux
ratios for identified non-Fe+ lines. Mean values of log (F2000/F1996) for
different ionization potential ranges of the ions producing the lines are shown
separately for the permitted and forbidden lines. All means show fading, which
is larger in the lowest range of ionization potential. Provisional
interpretations are suggested. We also measured the values of FWHM in 2000; the
previously known decrease with time of FWHM of lines due to the same ion has
continued.Comment: 16 pages, 5 figure
KWISP: an ultra-sensitive force sensor for the Dark Energy sector
An ultra-sensitive opto-mechanical force sensor has been built and tested in
the optics laboratory at INFN Trieste. Its application to experiments in the
Dark Energy sector, such as those for Chameleon-type WISPs, is particularly
attractive, as it enables a search for their direct coupling to matter. We
present here the main characteristics and the absolute force calibration of the
KWISP (Kinetic WISP detection) sensor. It is based on a thin Si3N4
micro-membrane placed inside a Fabry-Perot optical cavity. By monitoring the
cavity characteristic frequencies it is possible to detect the tiny membrane
displacements caused by an applied force. Far from the mechanical resonant
frequency of the membrane, the measured force sensitivity is 5.0e-14
N/sqrt(Hz), corresponding to a displacement sensitivity of 2.5e-15 m/sqrt(Hz),
while near resonance the sensitivity is 1.5e-14 N/sqrt(Hz), reaching the
estimated thermal limit, or, in terms of displacement, 7.5e-16 N/sqrt(Hz).
These displacement sensitivities are comparable to those that can be achieved
by large interferometric gravitational wave detectors.Comment: 9 pages, 8 figures in colo
Detecting solar chameleons through radiation pressure
Light scalar fields can drive the accelerated expansion of the universe.
Hence, they are obvious dark energy candidates. To make such models compatible
with tests of General Relativity in the solar system and "fifth force" searches
on Earth, one needs to screen them. One possibility is the so-called
"chameleon" mechanism, which renders an effective mass depending on the local
matter density. If chameleon particles exist, they can be produced in the sun
and detected on Earth exploiting the equivalent of a radiation pressure. Since
their effective mass scales with the local matter density, chameleons can be
reflected by a dense medium if their effective mass becomes greater than their
total energy. Thus, under appropriate conditions, a flux of solar chameleons
may be sensed by detecting the total instantaneous momentum transferred to a
suitable opto-mechanical force/pressure sensor. We calculate the solar
chameleon spectrum and the reach in the chameleon parameter space of an
experiment using the preliminary results from a force/pressure sensor,
currently under development at INFN Trieste, to be mounted in the focal plane
of one of the X-Ray telescopes of the CAST experiment at CERN. We show, that
such an experiment signifies a pioneering effort probing uncharted chameleon
parameter space.Comment: revised versio
The effect of dust obscuration in RR Tel on optical and IR long-term photometry and Fe II emission lines
Infrared and optical photometric and spectroscopic observations of the
symbiotic nova RR Tel are used to study the effects and properties of dust in
symbiotic binaries containing a cool Mira component, as well as showing
"obscuration events" of increased absorption, which are typical for such Miras.
A set of photometric observations of the symbiotic nova RR Tel in different
wavelength bands - visual from 1949 to 2002 and near-infrared (JHKL) from 1975
to 2002 - are presented. The variability due to the normal Mira pulsation was
removed from the JHKL data, which were then compared with the AAVSO visual
light curve. The changes of the Fe II emission line fluxes during the 1996-2000
obscuration episode were studied in the optical spectra taken with the
Anglo-Australian telescope.
We discuss the three periods during which the Mira component was heavily
obscured by dust as observed in the different wavelength bands. A change in the
correlations of J with other infrared magnitudes was observed with the colour
becoming redder after JD2446000. Generally, J-K was comparable, while K-L was
larger than typical values for single Miras. A distance estimate of 2.5 kpc,
based on the IR data, is given. A larger flux decrease for the permitted than
for the forbidden Fe II lines, during the obscuration episode studied, has been
found. There is no evidence for other correlations with line properties, in
particular with wavelength, which suggests obscuration due to separate
optically thick clouds in the outer layers.Comment: 19 pages, 11 figures, 3 table
Response-suggestion to The XENON1T excess: an overlooked dark matter signature?
The main alternatives of the recent XENON1T observation are solar axions,
neutrino magnetic moment and tritium. In this short note we suggest to
crosscheck whether the observation is related or not to dark matter (DM)
streams, by searching for planetary dependence of the observed excess. If such
a correlation is derived, this hint (<3.5sigma) can become the overlooked
direct DM discovery. To do this it is necessary to analyze the time
distribution of all the XENON1T data, and in particular the electronic events
with their time stamp and energy. Notably, the velocities of the dark sector
allow for planetary focusing effects towards the earth either by a single
celestial body or combined by the whole solar system. Surprisingly, as yet this
possibility has not been applied in the field of direct dark matter search,
even though DM velocities fit-in well planetary gravitational lensing effects.
The widely used signature of a direct dark matter search needs to be redefined,
while, with luck, such an analysis might confirm or exclude the solar origin of
the observed excess. Therefore, we suggest that XENON1T and DAMA release the
data.Comment: 1 pag
Search for axions in streaming dark matter
A new search strategy for the detection of the elusive dark matter (DM) axion
is proposed. The idea is based on streaming DM axions, whose flux might get
temporally enormously enhanced due to gravitational lensing. This can happen if
the Sun or some planet (including the Moon) is found along the direction of a
DM stream propagating towards the Earth location. The experimental requirements
to the axion haloscope are a wide-band performance combined with a fast axion
rest mass scanning mode, which are feasible. Once both conditions have been
implemented in a haloscope, the axion search can continue parasitically almost
as before. Interestingly, some new DM axion detectors are operating wide-band
by default. In order not to miss the actually unpredictable timing of a
potential short duration signal, a network of co-ordinated axion antennae is
required, preferentially distributed world-wide. The reasoning presented here
for the axions applies to some degree also to any other DM candidates like the
WIMPs.Comment: 5 page
Optomechanical sideband cooling of a thin membrane within a cavity
We present an experimental study of dynamical back-action cooling of the
fundamental vibrational mode of a thin semitransparent membrane placed within a
high-finesse optical cavity. We study how the radiation pressure interaction
modifies the mechanical response of the vibrational mode, and the experimental
results are in agreement with a Langevin equation description of the coupled
dynamics. The experiments are carried out in the resolved sideband regime, and
we have observed cooling by a factor 350 We have also observed the mechanical
frequency shift associated with the quadratic term in the expansion of the
cavity mode frequency versus the effective membrane position, which is
typically negligible in other cavity optomechanical devices.Comment: 15 pages, 7 figure
Dark Matter Detection in the Stratosphere
We investigate the prospects for the direct detection of dark matter (DM) particles, incident on the upper atmosphere. A recent work relating the burst-like temperature excursions in the stratosphere at heights of â38â47 km with low speed incident invisible streaming matter is the motivation behind this proposal. As an example, dark photons could match the reasoning presented in that work provided they constitute part of the local DM density. Dark photons emerge as a U(1) symmetry within extensions of the standard model. Dark photons mix with real photons with the same total energy without the need for an external field, as would be required, for instance, for axions. Furthermore, the ionospheric plasma column above the stratosphere can resonantly enhance the dark photon-to-photon conversion. Noticeably, the stratosphere is easily accessible with balloon flights. Balloon missions with up to a few tons of payload can be readily assembled to operate for months at such atmospheric heights. This proposal is not limited to streaming dark photons, as other DM constituents could be involved in the observed seasonal heating of the upper stratosphere. Therefore, we advocate a combination of different types of measurements within a multi-purpose parallel detector system, in order to increase the direct detection potential for invisible streaming constituents that affect, annually and around January, the upper stratosphere
Advances in optomechanical force sensors
Mechanical elements are successfully employed as force sensors in various devices. The sensors have reached impressive sensitivity of few nN/sqrt(Hz), but the quest for even more sensitive sensors is still on. The capability of sensing a single bacteria stuck to the sensor's surface in few seconds would provide unprecedented possibilities in various fields. Even in physics such sensitive sensors could be used in search for the elusive constituents of the dark sector. A possible interaction of either dark energy or dark matter with the sensor could be detected. A characterisation of an optimised sensor element will be presented along with it's properties
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