1,547 research outputs found
New measurements of from gamma-ray bursts
Context: Data from cosmic microwave background radiation (CMB), baryon
acoustic oscillations (BAO), and supernovae Ia (SNe-Ia) support a constant dark
energy equation of state with . Measuring the evolution of
along the redshift is one of the most demanding challenges for observational
cosmology. Aims: We discuss the existence of a close relation for GRBs, named
Combo-relation, based on characteristic parameters of GRB phenomenology such as
the prompt intrinsic peak energy , the X-ray afterglow, the initial
luminosity of the shallow phase , the rest-frame duration of the
shallow phase, and the index of the late power-law decay . We use it
to measure and the evolution of the dark energy equation of state.
We also propose a new calibration method for the same relation, which reduces
the dependence on SNe Ia systematics. Methods: We have selected a sample of
GRBs with 1) a measured redshift ; 2) a determined intrinsic prompt peak
energy , and 3) a good coverage (0.3-10) keV afterglow light curves.
The fitting technique of the rest.frame (0.3-10) keV luminosity light curves
represents the core of the Combo-relation. We separate the early steep decay,
considered a part of the prompt emission, from the X-ray afterglow additional
component. Data with the largest positive residual, identified as flares, are
automatically eliminated until the p-value of the fit becomes greater than 0.3.
Results: We strongly minimize the dependency of the Combo-GRB calibration on
SNe Ia. We also measure a small extra-Poissonian scatter of the Combo-relation,
which allows us to infer from GRBs alone
(1) for the CDM cosmological model, and , for the flat-Universe
variable equation of state case.Comment: 10 pages, 9 figures, 3 tables. Accepted for publication in A&A.
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PSZ2LenS. Weak lensing analysis of the Planck clusters in the CFHTLenS and in the RCSLenS
The possibly unbiased selection process in surveys of the Sunyaev Zel'dovich
effect can unveil new populations of galaxy clusters. We performed a weak
lensing analysis of the PSZ2LenS sample, i.e. the PSZ2 galaxy clusters detected
by the Planck mission in the sky portion covered by the lensing surveys
CFHTLenS and RCSLenS. PSZ2LenS consists of 35 clusters and it is a
statistically complete and homogeneous subsample of the PSZ2 catalogue. The
Planck selected clusters appear to be unbiased tracers of the massive end of
the cosmological haloes. The mass concentration relation of the sample is in
excellent agreement with predictions from the Lambda cold dark matter model.
The stacked lensing signal is detected at 14 sigma significance over the radial
range 0.1<R<3.2 Mpc/h, and is well described by the cuspy dark halo models
predicted by numerical simulations. We confirmed that Planck estimated masses
are biased low by b_SZ= 27+-11(stat)+-8(sys) per cent with respect to weak
lensing masses. The bias is higher for the cosmological subsample, b_SZ=
40+-14+-(stat)+-8(sys) per cent.Comment: v1: 23 pages. Comments are welcome. v2: 27 pages, in press on MNRAS.
Expanded discussion on systematics and lensing average
Source plane reconstruction of the giant gravitational arc in Abell 2667: a candidate Wolf-Rayet galaxy at z~1
We present a new analysis of HST, Spitzer telescope imaging and VLT imaging
and spectroscopic data of a bright lensed galaxy at =1.0334 in the lensing
cluster Abell~2667. Using this high-resolution imaging we present an updated
lens model that allows us to fully understand the lensing geometry and
reconstruct the lensed galaxy in the source plane. This giant arc gives a
unique opportunity to peer into the structure of a high-redshift disk galaxy.
We find that the lensed galaxy of Abell 2667 is a typical spiral galaxy with
morphology similar to the structure of its counterparts at higher redshift
. The surface brightness of the reconstructed source galaxy in the
z band reveals the central surface brightness mag
arcsec and the characteristic radius kpc at redshift
. The morphological reconstruction in different bands shows obvious
negative radial color gradients for this galaxy. Moreover, the redder central
bulge tends to contain a metal-rich stellar population, rather than being
heavily reddened by dust due to high and patchy obscuration. We analyze the
VIMOS/IFU spectroscopic data and find that, in the given wavelength range
( \AA), the combined arc spectrum of the source galaxy is
characterized by a strong continuum emission with strong UV absorption lines
(FeII and MgII) and shows the features of a typical starburst Wolf-Rayet galaxy
NGC5253. More specifically, we have measured the EWs of FeII and MgII lines in
the Abell 2667 spectrum, and obtained similar values for the same wavelength
interval of the NGC5253 spectrum. Marginal evidence for CIII] 1909 emission at
the edge of the grism range further confirms our expectation.Comment: 20 pages, 7 figures, 1 table, accepted by the Astronomical Journa
Diagnosing The Ejecta Properties of Engine-Driven Supernovae from Observables in Their Initial Phase
Engine-driven explosions with continuous energy input from the central system
have been suggested for supernovae (SNe) associated with a Gamma-Ray Burst
(GRB), super-luminous SNe (SLSNe), and at least a fraction of broad-lined SNe
Ic (SNe Ic-BL) even without an associated GRB. In the present work, we
investigate observational consequences in this scenario, focusing on the case
where the energy injection is sufficiently brief, which has been suggested for
GRB-SNe. We construct a simplified, spherical ejecta model sequence taking into
account the major effects of the central engine; composition mixing, density
structure, and the outermost ejecta velocity. Unlike most of the previous works
for GRB-SNe, we solve the formation of the photosphere self-consistently, with
which we can predict the photometric and spectroscopic observables. We find
that these ejecta properties strongly affect their observational appearance in
the initial phase (~ a week since the explosion), highlighted by blended lines
suffering from higher-velocity absorptions for the flatter density distribution
and/or higher outermost ejeca velocity. This behaviour also affects the
multi-band light curves in a non-monotonic way. Prompt follow-up observations
starting immediately after the explosion thus provides key diagnostics to
unveil the nature of the central engine behind GRB-SNe and SNe Ic-BL. For SN
2017iuk associated with GRB 171205A these diagnosing observational data are
available, and we show that the expected structure from the engine-driven
explosion, i.e., a flat power-law density structure extending up to >~ 100,000
km/s, can explain the observed spectral evolution reasonably well.Comment: 12 pages, 7 figures, 1 table. Accepted for publication in MNRA
GRB 110709B in the Induced Gravitational Collapse paradigm
Context: GRB110709B is the first source for which Swift BAT triggered twice,
with a time separation of ~10 min. The first emission (Ep. 1) goes from 40s
before the 1{\deg} trigger up to 60s after it. The second (Ep. 2) goes from 35s
before the 2{\deg} trigger to 100s after it.[...] Within the Induced
Gravitational Collapse (IGC) model, we assume the progenitor to be a close
binary system composed of a core of an evolved star and a Neutron Star (NS).
The evolved star explodes as a Supernova (SN) and ejects material that is
partially accreted by the NS. We identify this process with Ep. 1. The
accretion process brings the NS over its critical mass, thus gravitationally
collapsing to a BH. This process leads to the GRB emission, Ep. 2.[...] Aims:
We analyze the spectra and time variability of Ep. 1 and 2 and compute the
relevant parameters of the binary progenitor[...] in the IGC paradigm. Methods:
We perform a time-resolved spectral analysis of Ep. 1 with a blackbody (BB)
plus a power-law (PL) spectral model. We analyze Ep. 2 within the Fireshell
model, identifying the Proper-GRB (P-GRB) and simulating the light curve and
spectrum. We establish the redshift to be z=0.75 [...]. Results: We find for
Ep. 1 a BB temperature following a broken PL with time, with the PL slopes at
early and late times \alpha=0 and \beta=-4+/-2, respectively, and a break at
t=41.21s. The total energy of Ep. 1 and 2 are E_{iso}^1=1.42x10^{53}erg and
E_{iso}^2=2.43x10^{52}erg, respectively. We find at transparency a Lorentz
factor \Gamma~173, laboratory radius of 6.04x10^{13}cm, P-GRB observed
temperature kT_{P-GRB}=12.36keV, baryon load B=0.0057 and P-GRB energy
E_{P-GRB}=3.44x10^{50}erg. [...] Conclusions: We interpret GRB110709B as a
member of the IGC sources, together with GRB970828, GRB090618 and GRB101023.
The XRT data during Ep. 2 offers an unprecedented tool for improving the
diagnostic of GRBs emission.Comment: 12 pages, 17 figures, to appear on A&
Curiosity cloning: neural analysis of scientific knowledge
Event-related potentials (ERPs) are indicators of brain
activity related to cognitive processes. They can be de-
tected from EEG signals and thus constitute an attractive
non-invasive option to study cognitive information pro-
cessing. The P300 wave is probably the most celebrated
example of an event-related potential and it is classically
studied in connection to the odd-ball paradigm experi-
mental protocol, able to consistently provoke the brain
wave. We propose the use of P300 detection to identify
the scientific interest in a large set of images and train
a computer with machine learning algorithms using the
subject’s responses to the stimuli as the training data set. As a first step, we here describe a number of experiments designed to relate the P300 brain wave to the cognitive processes related to placing a scientific judgment on a picture and to study the number of images per seconds
that can be processed by such a system
Insufficient control of blood pressure and incident diabetes
OBJECTIVE:
Incidence of type 2 diabetes might be associated with preexisting hypertension. There is no information on whether incident diabetes is predicted by blood pressure control. We evaluated the hazard of diabetes in relation to blood pressure control in treated hypertensive patients.
RESEARCH DESIGN AND METHODS:
Nondiabetic, otherwise healthy, hypertensive patients (N = 1,754, mean +/- SD age 52 +/- 11 years, 43% women) participated in a network over 3.4 +/- 1 years of follow-up. Blood pressure was considered uncontrolled if systolic was >or=140 mmHg and/or diastolic was >or=90 mmHg at the last outpatient visit. Diabetes was defined according to American Diabetes Association guidelines.
RESULTS:
Uncontrolled blood pressure despite antihypertensive treatment was found in 712 patients (41%). At baseline, patients with uncontrolledblood pressure were slightly younger than patients with controlled blood pressure (51 +/- 11 vs. 53 +/- 12 years, P < 0.001), with no differences in sex distribution, BMI, duration of hypertension, baseline blood pressure, fasting glucose, serum creatinine and potassium, lipid profile, or prevalence of metabolic syndrome. During follow-up, 109 subjects developed diabetes. Incidence of diabetes was significantly higher in patients with uncontrolled (8%) than in those with controlled blood pressure (4%, odds ratio 2.08, P < 0.0001). In Cox regression analysis controlling for baseline systolic blood pressure and BMI, family history of diabetes, and physical activity, uncontrolled blood pressure doubled the risk of incident diabetes (hazard ratio [HR] 2.10, P < 0.001), independently of significant effects of age (HR 1.02 per year, P = 0.03) and baseline fasting glucose (HR 1.10 per mg/dl, P < 0.001).
CONCLUSIONS:
In a large sample of treated nondiabetic hypertensive subjects, uncontrolled blood pressure is associated with twofold increased risk of incident diabetes independently of age, BMI, baseline blood pressure, or fasting glucose
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