54 research outputs found
No UV-bright Eruptions from SN 2023ixf in GALEX Imaging 15-20 Years Before Explosion
We analyze pre-explosion ultraviolet (UV) imaging of the nearby Type II
supernova SN 2023ixf in search of precursor variability. No outbursts are seen
in observations obtained 15-20 yr prior to explosion to a limit of and . The time period of
these non-detections roughly corresponds to changes in the circumstellar
density inferred from early spectra and photometry.Comment: 4 pages, 1 figure. Submitted to AAS Research Note
Model Independent Bounds on Magnetic Moments of Majorana Neutrinos
We analyze the implications of neutrino masses for the magnitude of neutrino
magnetic moments. By considering electroweak radiative corrections to the
neutrino mass, we derive model-independent naturalness upper bounds on neutrino
magnetic moments, , generated by physics above the electroweak scale.
For Dirac neutrinos, the bound is several orders of magnitude more stringent
than present experimental limits. However, for Majorana neutrinos the magnetic
moment contribution to the mass is Yukawa suppressed. The bounds we derive for
magnetic moments of Majorana neutrinos are weaker than present experimental
limits if is generated by new physics at ~ 1 TeV, and surpass current
experimental sensitivity only for new physics scales > 10 -- 100 TeV. The
discovery of a neutrino magnetic moment near present limits would thus signify
that neutrinos are Majorana particles.Comment: 8 pages, 5 figure
SDSS J124602.54+011318.8: A Highly Luminous Optical Transient at z=0.385
We report the discovery of a highly luminous optical transient (OT), SDSS
J124602.54+011318.8, associated with a galaxy at a redshift of 0.385. In this
paper we consider the possibility that the OT may be a GRB afterglow. Three
sets of images and two sets of spectra were obtained as part of the normal
operations of the Sloan Digital Sky Survey (SDSS). In the first two image sets,
observed two nights apart, the object appears as a point source at
. The third image set, observed about 410 days later, shows an
extended source which is more than 2.5 magnitudes fainter. The spectra were
observed about 400 and 670 days after the first two image sets, and both show
an apparently normal galaxy at a redshift of 0.385. Associating the OT with the
galaxy, the absolute magnitude was , which is over 4 magnitudes
brighter than the most luminous supernova ever measured. The spectral energy
distributions of the galaxy-subtracted OT derived from the first two image sets
are well-fit by single power-laws with indices of and -1.29
respectively, similar to most GRB afterglows. Based upon the luminosity of the
OT, non-detections in contemporaneous ROTSE-I images, and the change in
spectral slope, the OT, if an afterglow, was likely discovered early during a
``plateau'' or slowly-fading phase. The discovery of a GRB afterglow at this
stage of the SDSS is consistent with expectations, but only if the optical
emission is much less strongly beamed than the gamma-rays. We emphasize that
other explanations for the OT cannot be ruled out; a recent follow-up study by
[galyam02] provides strong evidence that this source is in fact an unusual AGN.Comment: Updated version to appear in Ap
SNEWS: The SuperNova Early Warning System
This paper provides a technical description of the SuperNova Early Warning
System (SNEWS), an international network of experiments with the goal of
providing an early warning of a galactic supernova.Comment: 25 pages, for New Journal of Physics Focus Issue on Neutrino Physic
Catching Element Formation In The Act
Gamma-ray astronomy explores the most energetic photons in nature to address
some of the most pressing puzzles in contemporary astrophysics. It encompasses
a wide range of objects and phenomena: stars, supernovae, novae, neutron stars,
stellar-mass black holes, nucleosynthesis, the interstellar medium, cosmic rays
and relativistic-particle acceleration, and the evolution of galaxies. MeV
gamma-rays provide a unique probe of nuclear processes in astronomy, directly
measuring radioactive decay, nuclear de-excitation, and positron annihilation.
The substantial information carried by gamma-ray photons allows us to see
deeper into these objects, the bulk of the power is often emitted at gamma-ray
energies, and radioactivity provides a natural physical clock that adds unique
information. New science will be driven by time-domain population studies at
gamma-ray energies. This science is enabled by next-generation gamma-ray
instruments with one to two orders of magnitude better sensitivity, larger sky
coverage, and faster cadence than all previous gamma-ray instruments. This
transformative capability permits: (a) the accurate identification of the
gamma-ray emitting objects and correlations with observations taken at other
wavelengths and with other messengers; (b) construction of new gamma-ray maps
of the Milky Way and other nearby galaxies where extended regions are
distinguished from point sources; and (c) considerable serendipitous science of
scarce events -- nearby neutron star mergers, for example. Advances in
technology push the performance of new gamma-ray instruments to address a wide
set of astrophysical questions.Comment: 14 pages including 3 figure
ANTARES constrains a blazar origin of two IceCube PeV neutrino events
Context. The source(s) of the neutrino excess reported by the IceCube Collaboration is unknown. The TANAMI Collaboration recently reported on the multiwavelength emission of six bright, variable blazars which are positionally coincident with two of the most energetic IceCube events. Objects like these are prime candidates to be the source of the highest-energy cosmic rays, and thus of associated neutrino emission. Aims. We present an analysis of neutrino emission from the six blazars using observations with the ANTARES neutrino telescope. Methods. The standard methods of the ANTARES candidate list search are applied to six years of data to search for an excess of muons Âż and hence their neutrino progenitors Âż from the directions of the six blazars described by the TANAMI Collaboration, and which are possibly associated with two IceCube events. Monte Carlo simulations of the detector response to both signal and background particle fluxes are used to estimate the sensitivity of this analysis for different possible source neutrino spectra. A maximum-likelihood approach, using the reconstructed energies and arrival directions of through-going muons, is used to identify events with properties consistent with a blazar origin. Results. Both blazars predicted to be the most neutrino-bright in the TANAMI sample (1653â329 and 1714â336) have a signal flux fitted by the likelihood analysis corresponding to approximately one event. This observation is consistent with the blazar-origin hypothesis of the IceCube event ICâ14 for a broad range of blazar spectra, although an atmospheric origin cannot be excluded. No ANTARES events are observed from any of the other four blazars, including the three associated with IceCube event IC20. This excludes at a 90% confidence level the possibility that this event was produced by these blazars unless the neutrino spectrum is flatter than â2.4
Canagliflozin and renal outcomes in type 2 diabetes and nephropathy
BACKGROUND Type 2 diabetes mellitus is the leading cause of kidney failure worldwide, but few effective long-term treatments are available. In cardiovascular trials of inhibitors of sodiumâglucose cotransporter 2 (SGLT2), exploratory results have suggested that such drugs may improve renal outcomes in patients with type 2 diabetes. METHODS In this double-blind, randomized trial, we assigned patients with type 2 diabetes and albuminuric chronic kidney disease to receive canagliflozin, an oral SGLT2 inhibitor, at a dose of 100 mg daily or placebo. All the patients had an estimated glomerular filtration rate (GFR) of 30 to <90 ml per minute per 1.73 m2 of body-surface area and albuminuria (ratio of albumin [mg] to creatinine [g], >300 to 5000) and were treated with reninâangiotensin system blockade. The primary outcome was a composite of end-stage kidney disease (dialysis, transplantation, or a sustained estimated GFR of <15 ml per minute per 1.73 m2), a doubling of the serum creatinine level, or death from renal or cardiovascular causes. Prespecified secondary outcomes were tested hierarchically. RESULTS The trial was stopped early after a planned interim analysis on the recommendation of the data and safety monitoring committee. At that time, 4401 patients had undergone randomization, with a median follow-up of 2.62 years. The relative risk of the primary outcome was 30% lower in the canagliflozin group than in the placebo group, with event rates of 43.2 and 61.2 per 1000 patient-years, respectively (hazard ratio, 0.70; 95% confidence interval [CI], 0.59 to 0.82; P=0.00001). The relative risk of the renal-specific composite of end-stage kidney disease, a doubling of the creatinine level, or death from renal causes was lower by 34% (hazard ratio, 0.66; 95% CI, 0.53 to 0.81; P<0.001), and the relative risk of end-stage kidney disease was lower by 32% (hazard ratio, 0.68; 95% CI, 0.54 to 0.86; P=0.002). The canagliflozin group also had a lower risk of cardiovascular death, myocardial infarction, or stroke (hazard ratio, 0.80; 95% CI, 0.67 to 0.95; P=0.01) and hospitalization for heart failure (hazard ratio, 0.61; 95% CI, 0.47 to 0.80; P<0.001). There were no significant differences in rates of amputation or fracture. CONCLUSIONS In patients with type 2 diabetes and kidney disease, the risk of kidney failure and cardiovascular events was lower in the canagliflozin group than in the placebo group at a median follow-up of 2.62 years
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