We present optical light curves, redshifts, and classifications for spectroscopically confirmed Type Ia supernovae (SNe Ia) discovered by the Pan-STARRS1 (PS1) Medium Deep Survey. We detail ...improvements to the PS1 SN photometry, astrometry, and calibration that reduce the systematic uncertainties in the PS1 SN Ia distances. We combine the subset of PS1 SNe Ia (0.03 < z < 0.68) with useful distance estimates of SNe Ia from the Sloan Digital Sky Survey (SDSS), SNLS, and various low-z and Hubble Space Telescope samples to form the largest combined sample of SNe Ia, consisting of a total of SNe Ia in the range of 0.01 < z < 2.3, which we call the "Pantheon Sample." When combining Planck 2015 cosmic microwave background (CMB) measurements with the Pantheon SN sample, we find and for the wCDM model. When the SN and CMB constraints are combined with constraints from BAO and local H0 measurements, the analysis yields the most precise measurement of dark energy to date: and for the CDM model. Tension with a cosmological constant previously seen in an analysis of PS1 and low-z SNe has diminished after an increase of 2× in the statistics of the PS1 sample, improved calibration and photometry, and stricter light-curve quality cuts. We find that the systematic uncertainties in our measurements of dark energy are almost as large as the statistical uncertainties, primarily due to limitations of modeling the low-redshift sample. This must be addressed for future progress in using SNe Ia to measure dark energy.
Abstract
We present panchromatic observations and modeling of supernova (SN) 2020tlf, the first normal Type II-P/L SN with confirmed precursor emission, as detected by the Young Supernova Experiment ...transient survey. Pre-SN activity was detected in
riz
-bands at −130 days and persisted at relatively constant flux until first light. Soon after discovery, “flash” spectroscopy of SN 2020tlf revealed narrow, symmetric emission lines that resulted from the photoionization of circumstellar material (CSM) shed in progenitor mass-loss episodes before explosion. Surprisingly, this novel display of pre-SN emission and associated mass loss occurred in a red supergiant (RSG) progenitor with zero-age main-sequence mass of only 10–12
M
⊙
, as inferred from nebular spectra. Modeling of the light curve and multi-epoch spectra with the non-LTE radiative-transfer code CMFGEN and radiation-hydrodynamical code HERACLES suggests a dense CSM limited to
r
≈ 10
15
cm, and mass-loss rate of 10
−2
M
⊙
yr
−1
. The luminous light-curve plateau and persistent blue excess indicates an extended progenitor, compatible with an RSG model with
R
⋆
= 1100
R
⊙
. Limits on the shock-powered X-ray and radio luminosity are consistent with model conclusions and suggest a CSM density of
ρ
< 2 × 10
−16
g cm
−3
for distances from the progenitor star of
r
≈ 5 × 10
15
cm, as well as a mass-loss rate of
M
̇
<
1.3
×
10
−
5
M
☉
yr
−
1
at larger distances. A promising power source for the observed precursor emission is the ejection of stellar material following energy disposition into the stellar envelope as a result of gravity waves emitted during either neon/oxygen burning or a nuclear flash from silicon combustion.
A diet rich in dairy and calcium (Ca) has been variably associated with improvements in body composition and decreased risk of type 2 diabetes. Our objective was to determine if a dietary pattern ...high in dairy and Ca improves weight loss and subjective appetite to a greater extent than a low dairy/Ca diet during energy restriction in overweight and obese adults with metabolic syndrome.
A total of 49 participants were randomized to one of two treatment groups: Control (low dairy, ≈ 700 mg/day Ca, -500 kcal/day) or Dairy/Ca (high dairy, ≈ 1400 mg/day Ca, -500 kcal/day) for 12 weeks. Body composition, subjective ratings of appetite, food intake, plasma satiety hormones, glycemic response and inflammatory cytokines were measured.
Control (-2.2 ± 0.5 kg) and Dairy/Ca (-3.3 ± 0.6 kg) had similar weight loss. Based on self-reported energy intake, the percentage of expected weight loss achieved was higher with Dairy/Ca (82.1 ± 19.4%) than Control (32.2 ± 7.7%; P=0.03). Subjects in the Dairy/Ca group reported feeling more satisfied (P=0.01) and had lower dietary fat intake (P=0.02) over 12 weeks compared with Control. Compared with Control, Dairy/Ca had higher plasma levels of peptide tyrosine tyrosine (PYY, P=0.01) during the meal tolerance test at week 12. Monocyte chemoattractant protein-1 was reduced at 30 min with Dairy/Ca compared with Control (P=0.04).
In conclusion, a dairy- and Ca-rich diet was not associated with greater weight loss than control. Modest increases in plasma PYY concentrations with increased dairy/Ca intake, however, may contribute to enhanced sensations of satisfaction and reduced dietary fat intake during energy restriction.
The affinity A_{Ps} of positronium (Ps) atoms for a metal is the negative of the maximum kinetic energy with which Ps is emitted into vacuum when thermalized positrons in a metal encounter the ...surface. When this quantity is measured by ground state Ps time of flight (TOF), the precision is severely limited by the short triplet state lifetime of 142 ns. By quickly converting the emitted Ps atoms into long-lived Rydberg states, we are able to dramatically increase the TOF to allow precision measurements of A_{Ps}. From our measurements made on a Cu(110) sample at T=128 K, we find A_{Ps}(128 K)=(-2.476±0.010_{stat}±0.013_{syst}) eV, compared with the result A_{Ps}(128 K)=(-2.545±0.010_{num}±0.010_{syst}) eV found using highly accurate generalized gradient approximations for both electrons and positrons within density functional theory. Such precision opens up opportunities in the quest for an improved density functional.
We assess the impact of transport of pollution from midlatitudes on the abundance of ozone in the Arctic in summer 2006 using the GEOS‐Chem global chemical transport model and its adjoint. We find ...that although the impact of midlatitude emissions on ozone abundances in the Arctic is at a maximum in fall and winter, in July transport from North America, Asia, and Europe together contributed about 25% of surface ozone abundances in the Arctic. Throughout the summer, the dominant source of ozone in the Arctic troposphere was photochemical production within the Arctic, which accounted for more than 50% of the ozone in the Arctic boundary layer and as much as 30%–40% of the ozone in the middle troposphere. An adjoint sensitivity analysis of the impact of NOx emissions on ozone at Alert shows that on synoptic time scales in both the lower and middle troposphere, ozone abundances are more sensitive to emissions between 50°N and 70°N, with important influences from anthropogenic, biomass burning, soil, and lightning sources. Although local surface NOx emissions contribute to ozone formation, transport of NOx in the form of peroxyacetyl nitrate (PAN) from outside the Arctic and from the upper troposphere also contributed to ozone production in the lower troposphere. We find that in late May and June the release of NOx from PAN decomposition accounted for 93% and 55% of ozone production at the Arctic surface, respectively.
Key Points
Midlatitude source regions contribute 10‐25% of Arctic ozone in summer
On short time scales, Arctic O3 is most sensitive to NOx emissions at 50‐70N
NOx transported as PAN constitutes most of O3 produced in the Arctic spring
This Letter reports on a cavity haloscope search for dark matter axions in the Galactic halo in the mass range 2.81-3.31 μeV. This search utilizes the combination of a low-noise Josephson parametric ...amplifier and a large-cavity haloscope to achieve unprecedented sensitivity across this mass range. This search excludes the full range of axion-photon coupling values predicted in benchmark models of the invisible axion that solve the strong CP problem of quantum chromodynamics.
We report the results from a haloscope search for axion dark matter in the 3.3-4.2 μeV mass range. This search excludes the axion-photon coupling predicted by one of the benchmark models of ..."invisible" axion dark matter, the Kim-Shifman-Vainshtein-Zakharov model. This sensitivity is achieved using a large-volume cavity, a superconducting magnet, an ultra low noise Josephson parametric amplifier, and sub-Kelvin temperatures. The validity of our detection procedure is ensured by injecting and detecting blind synthetic axion signals.
Variational methods are widely used to solve geophysical inverse problems. Although gradient‐based minimization algorithms are available for high‐dimensional problems (dimension >106), they do not ...provide an estimate of the errors in the optimal solution. In this study, we assess the performance of several numerical methods to approximate the analysis‐error covariance matrix, assuming reasonably linear models. The evaluation is performed for a CO2 flux estimation problem using synthetic remote‐sensing observations of CO2 columns. A low‐dimensional experiment is considered in order to compare the analysis error approximations to a full‐rank finite‐difference inverse Hessian estimate, followed by a realistic high‐dimensional application. Two stochastic approaches, a Monte‐Carlo simulation and a method based on random gradients of the cost function, produced analysis error variances with a relative error <10%. The long‐distance error correlations due to sampling noise are significantly less pronounced for the gradient‐based randomization, which is also particularly attractive when implemented in parallel. Deterministic evaluations of the inverse Hessian using the Broyden–Fletcher–Goldfarb–Shanno (BFGS) algorithm are also tested. While existing BFGS preconditioning techniques yield poor approximations of the error variances (relative error >120%), a new preconditioner that efficiently accumulates information on the diagonal of the inverse Hessian dramatically improves the results (relative error <50%). Furthermore, performing several cycles of the BFGS algorithm using the same gradient and vector pairs enhances its performance (relative error <30%) and is necessary to obtain convergence. Leveraging those findings, we proposed a BFGS hybrid approach which combines the new preconditioner with several BFGS cycles using information from a few (3–5) Monte‐Carlo simulations. Its performance is comparable to the stochastic approximations for the low‐dimensional case, while good scalability is obtained for the high‐dimensional experiment. Potential applications of these new BFGS methods range from characterizing the information content of high‐dimensional inverse problems to improving the convergence rate of current minimization algorithms.
Many industrial applications make use of ultrasonic vibration to soften metals. The existing understanding of such an acoustoplastic effect is one in which the ultrasonic irradiation either imposes ...additional stress waves to augment the quasi-static applied load, or causes heating of the metal, whereas the metal’s intrinsic deformation resistance or mechanism is assumed to be unaltered by the ultrasound. In this study, indentation experiments performed on aluminum samples simultaneously excited by ultrasound reveal that the latter intrinsically alters the deformation characteristics of the metal. The deformation microstructures underneath the indents were investigated by a combination of cross-sectional microscopic techniques involving focused-ion-beam milling, transmission electron microscopy and crystal orientation mapping by electron backscattered diffraction. The softening effect of the ultrasound is found to constitute recovery associated with extensive enhancement of subgrain formation during deformation. By comparing the microstructures of samples deformed with and without simultaneous application of ultrasound, and those subsequently excited by ultrasound after deformation, the enhanced subgrain formation is proved to be one due to the combined application of the quasi-static loading and the ultrasound, but not a simple addition of the two. Similarly, by comparing with samples deformed while being simultaneously or subsequently heated up, the enhanced subgrain formation by the ultrasound is proved to be a lot greater than that due to the heat that it generates within the metal. Such effects of the ultrasound are interpreted by its ability to enhance dipole annihilation. The superimposed ultrasound causes dislocations to travel longer distances in a jerky manner, so that they can continuously explore until dipole annihilation.
We present light curves and classification spectra of 17 hydrogen-poor superluminous supernovae (SLSNe) from the Pan-STARRS1 Medium Deep Survey (PS1 MDS). Our sample contains all objects from the PS1 ...MDS sample with spectroscopic classification that are similar to either of the prototypes SN 2005ap or SN 2007bi, without an explicit limit on luminosity. With a redshift range , PS1 MDS is the first SLSN sample primarily probing the high-redshift population; our multifilter PS1 light curves probe the rest-frame UV emission, and hence the peak of the spectral energy distribution. We measure the temperature evolution and construct bolometric light curves, and find peak luminosities of erg s−1 and lower limits on the total radiated energies of erg. The light curve shapes are diverse, with both rise and decline times spanning a factor of ∼5 and several examples of double-peaked light curves. When correcting for the flux-limited nature of our survey, we find a median peak luminosity at 4000 of and a spread of .
PDF
