2,471 research outputs found
A Planet at 5 AU Around 55 Cancri
We report precise Doppler shift measurements of 55 Cancri (G8V) obtained from
1989 to 2002 at Lick Observatory. The velocities reveal evidence for an outer
planetary companion to 55 Cancri orbiting at 5.5 AU. The velocities also
confirm a second, inner planet at 0.11 AU. The outer planet is the first
extrasolar planet found that orbits near or beyond the orbit of Jupiter. It was
drawn from a sample of ~50 stars observed with sufficient duration and quality
to detect a giant planet at 5 AU, implying that such planets are not rare. The
properties of this jupiter analog may be compared directly to those of the
Jovian planets in our Solar System. Its eccentricity is modest, e=0.16,
compared with e=0.05 for both Jupiter and Saturn. Its mass is at least 4.0
jupiter masses (M sin i). The two planets do not perturb each other
significantly. Moreover, a third planet of sub-Jupiter mass could easily
survive in between these two known planets. Indeed a third periodicity remains
in the velocity measurements with P = 44.3 d and a semi-amplitude of 13 m/s.
This periodicity is caused either by a third planet at a=0.24 AU or by
inhomogeneities on the stellar surface that rotates with period 42 d. The
planet interpretation is more likely, as the stellar surface is quiet,
exhibiting log(R'_{HK}) = -5.0 and brightness variations less than 1 millimag,
and any hypothetical surface inhomogeneity would have to persist in longitude
for 14 yr. Even with all three planets, an additional planet of
terrestrial--mass could orbit stably at ~1 AU. The star 55 Cancri is apparently
a normal, middle-aged main sequence star with a mass of 0.95 solar masses, rich
in heavy elements ([Fe/H] = +0.27). This high metallicity raises the issue of
the relationship between its age, rotation, and chromosphere.Comment: 47 pages, 4 tables, 12 figures, uses AASTE
The Large Aperture GRB Observatory
The Large Aperture GRB Observatory (LAGO) is aiming at the detection of the
high energy (around 100 GeV) component of Gamma Ray Bursts, using the single
particle technique in arrays of Water Cherenkov Detectors (WCD) in high
mountain sites (Chacaltaya, Bolivia, 5300 m a.s.l., Pico Espejo, Venezuela,
4750 m a.s.l., Sierra Negra, Mexico, 4650 m a.s.l). WCD at high altitude offer
a unique possibility of detecting low gamma fluxes in the 10 GeV - 1 TeV range.
The status of the Observatory and data collected from 2007 to date will be
presented.Comment: 4 pages, proceeding of 31st ICRC 200
Water Cherenkov Detectors response to a Gamma Ray Burst in the Large Aperture GRB Observatory
In order to characterise the behaviour of Water Cherenkov Detectors (WCD)
under a sudden increase of 1 GeV - 1 TeV background photons from a Gamma Ray
Burst (GRB), simulations were conducted and compared to data acquired by the
WCD of the Large Aperture GRB Observatory (LAGO). The LAGO operates arrays of
WCD at high altitude to detect GRBs using the single particle technique. The
LAGO sensitivity to GRBs is derived from the reported simulations of the gamma
initiated particle showers in the atmosphere and the WCD response to
secondaries.Comment: 5 pages, proceeding of the 31st ICRC 200
Neutrino Physics from Charged Higgs and Slepton Associated Production in AMSB
In the Minimal Supersymmetric Standard Model with bilinear R-Parity
violation, terms that violate R-Parity and lepton number are introduced in the
superpotential, and sneutrino vacuum expectation values are induced. As a
result, neutrino masses and mixing angles are generated via a low energy
see-saw mechanism. We show that this model embedded into an anomaly mediated
supersymmetry breaking scenario is testable at a linear collider using charged
Higgs boson production in association with a stau. This is possible in regions
of parameter space where the charged Higgs and stau have similar mass,
producing an enhancement of the charged scalar mixing angles. We show that the
bilinear parameter and the sneutrino vev can be determined from charged scalar
observables, and estimate the precision of this determination.Comment: 21 pages, including 8 figure
The Pierre Auger Observatory III: Other Astrophysical Observations
Astrophysical observations of ultra-high-energy cosmic rays with the Pierre
Auger ObservatoryComment: Contributions to the 32nd International Cosmic Ray Conference,
Beijing, China, August 201
Highlights from the Pierre Auger Observatory
The Pierre Auger Observatory is the world's largest cosmic ray observatory.
Our current exposure reaches nearly 40,000 km str and provides us with an
unprecedented quality data set. The performance and stability of the detectors
and their enhancements are described. Data analyses have led to a number of
major breakthroughs. Among these we discuss the energy spectrum and the
searches for large-scale anisotropies. We present analyses of our X
data and show how it can be interpreted in terms of mass composition. We also
describe some new analyses that extract mass sensitive parameters from the 100%
duty cycle SD data. A coherent interpretation of all these recent results opens
new directions. The consequences regarding the cosmic ray composition and the
properties of UHECR sources are briefly discussed.Comment: 9 pages, 12 figures, talk given at the 33rd International Cosmic Ray
Conference, Rio de Janeiro 201
Astrophysically Triggered Searches for Gravitational Waves: Status and Prospects
In gravitational-wave detection, special emphasis is put onto searches that
focus on cosmic events detected by other types of astrophysical observatories.
The astrophysical triggers, e.g. from gamma-ray and X-ray satellites, optical
telescopes and neutrino observatories, provide a trigger time for analyzing
gravitational wave data coincident with the event. In certain cases the
expected frequency range, source energetics, directional and progenitor
information is also available. Beyond allowing the recognition of gravitational
waveforms with amplitudes closer to the noise floor of the detector, these
triggered searches should also lead to rich science results even before the
onset of Advanced LIGO. In this paper we provide a broad review of LIGO's
astrophysically triggered searches and the sources they target
Duration of Treatment for Pseudomonas aeruginosa Bacteremia : a Retrospective Study
Introduction: There is no consensus regarding optimal duration of antibiotic therapy for Pseudomonas aeruginosa bacteremia. We aimed to evaluate the impact of short antibiotic course. Methods: We present a retrospective multicenter study including patients with P. aeruginosa bacteremia during 2009-2015. We evaluated outcomes of patients treated with short (6-10 days) versus long (11-15 days) antibiotic courses. The primary outcome was a composite of 30-day mortality or bacteremia recurrence and/or persistence. Univariate and inverse probability treatment-weighted (IPTW) adjusted multivariate analysis for the primary outcome was performed. To avoid immortal time bias, the landmark method was used. Results: We included 657 patients; 273 received a short antibiotic course and 384 a long course. There was no significant difference in baseline characteristics of patients. The composite primary outcome occurred in 61/384 patients in the long-treatment group (16%) versus 32/273 in the short-treatment group (12%) (p = 0.131). Mortality accounted for 41/384 (11%) versus 25/273 (9%) of cases, respectively. Length of hospital stay was significantly shorter in the short group [median 13 days, interquartile range (IQR) 9-21 days, versus median 15 days, IQR 11-26 days, p = 0.002]. Ten patients in the long group discontinued antibiotic therapy owing to adverse events, compared with none in the short group. On univariate and multivariate analyses, duration of therapy was not associated with the primary outcome. Conclusions: In this retrospective study, 6-10 days of antibiotic course for P. aeruginosa bacteremia were as effective as longer courses in terms of survival and recurrence. Shorter therapy was associated with reduced length of stay and less drug discontinuation
Measurement of the cross-section and charge asymmetry of bosons produced in proton-proton collisions at TeV with the ATLAS detector
This paper presents measurements of the and cross-sections and the associated charge asymmetry as a
function of the absolute pseudorapidity of the decay muon. The data were
collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with
the ATLAS experiment at the LHC and correspond to a total integrated luminosity
of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements
varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the
1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured
with an uncertainty between 0.002 and 0.003. The results are compared with
predictions based on next-to-next-to-leading-order calculations with various
parton distribution functions and have the sensitivity to discriminate between
them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables,
submitted to EPJC. All figures including auxiliary figures are available at
https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13
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