Abstract
Type Iax supernovae (SNe Iax) are the largest known class of peculiar white dwarf SNe, distinct from normal Type Ia supernovae (SNe Ia). The unique properties of SNe Iax, especially their ...strong photospheric lines out to extremely late times, allow us to model their optical spectra and derive the physical parameters of the long-lasting photosphere. We present an extensive spectral timeseries, including 21 new spectra, of SN Iax 2014dt from +11 to +562 days after maximum light. We are able to reproduce the entire timeseries with a self-consistent, nearly unaltered deflagration explosion model from Fink et al. using
TARDIS
, an open source radiative-transfer code. We find that the photospheric velocity of SN 2014dt slows its evolution between +64 and +148 days, which closely overlaps the phase when we see SN 2014dt diverge from the normal spectral evolution of SNe Ia (+90 to +150 days). The photospheric velocity at these epochs, ∼400–1000 km s
−1
, may demarcate a boundary within the ejecta below which the physics of SNe Iax and normal SNe Ia differ. Our results suggest that SN 2014dt is consistent with a weak deflagration explosion model that leaves behind a bound remnant and drives an optically thick, quasi-steady-state wind creating the photospheric lines at late times. The data also suggest that this wind may weaken at epochs past +450 days, perhaps indicating a radioactive power source that has decayed away.
ABSTRACT
Strong gravitationally lensed supernovae (glSNe) are a powerful probe to obtain a measure of the expansion rate of the Universe, but they are also extremely rare. To date, only two glSNe ...with multiple images strongly lensed by galaxies have been found, but their short time delays make them unsuitable for cosmography. Here, we simulate a realistic catalogue of lensed supernovae and study the characteristics of the population of detectable systems for different surveys. Compared to previous studies, our simulations also account for the effect of microlensing and its impact on the glSNe yields. We show that the properties of glSNe in shallow surveys (such as the Zwicky Transient Facility) are determined by the need for large magnifications, which favours systems of four images with short time delays and low image separations. This picture is consistent with the properties of iPTF16geu and SN Zwicky, but is not representative of the population found in deeper surveys, which are limited by the volume of the Universe that is strongly lensed. For deeper surveys, such as the Legacy Survey of Space and Time (LSST), glSNe show longer time delays and greater angular separations, and the inclusion of microlensing results in 8 per cent of glSNe becoming demagnified under the detection threshold. In the 10 yr of the survey LSST should be able to find ≈180 systems, of which 70 will be suited for cosmography enabling a ≈1.2 per cent precision H0 measurement with LSST glSNe.
HIV is an ongoing global epidemic with estimates of more than a million new infections occurring annually. To combat viral spread, continuous innovations in areas including testing and treatment are ...necessary. In the United States, the Centers for Disease Control and Prevention recommend that laboratories follow an HIV testing algorithm that first uses a US Food and Drug Administration approved immunoassay to detect antibodies to HIV-1 or HIV-2 as well as HIV-1 p24 antigen in serum or plasma samples. An initially reactive specimen is tested by a supplemental assay for confirmation and to differentiate antibodies to HIV-1 or HIV-2. There are few Food and Drug Administration (FDA)-approved supplemental differentiation tests currently available. A multicenter investigation was conducted to determine the clinical performance for two independent versions of the Avioq VioOne HIV Profile Supplemental Assay (Avioq, Inc., Research Triangle Park, NC). The performance of both assay versions compared favorably with the performance parameters for the Geenius HIV 1/2 Supplemental Assay as published in that assay package insert (Bio-Rad Laboratories, Hercules, CA), the current gold standard for HIV supplemental testing. When comparing the two VioOne assays, version 2 (lacking HIV-2 p27 antibody detection) demonstrated improved reproducibility, specificity, and sensitivity as compared to its predecessor. IMPORTANCE We evaluated the reproducibility, sensitivity, and specificity data for two versions of the VioOne HIV Profile Supplemental Assay and compared these results back to similar results for the Geenius HIV 1/2 Supplemental Assay that are publicly available. Our study concluded that the VioOne HIV Profile Supplemental Assay compared favorably with the Geenius HIV 1/2 Supplemental Assay, thus providing an additional option for clinical laboratories to improve and expand their HIV testing capabilities.
Type Iax supernovae as a few-parameter family Barna, Barnabás; Szalai, Tamás; Kerzendorf, Wolfgang E ...
Monthly notices of the Royal Astronomical Society,
11/2018, Letnik:
480, Številka:
3
Journal Article
ABSTRACT
Early observations of transient explosions can provide vital clues to their progenitor origins. In this paper, we present the nearby Type Iax (02cx-like) supernova (SN), SN 2020udy, that was ...discovered within hours (∼7 h) of estimated first light. An extensive data set of ultra-violet, optical, and near-infrared observations was obtained, covering out to ∼150 d after explosion. SN 2020udy peaked at −17.86 ± 0.43 mag in the r band and evolved similarly to other ‘luminous’ SNe Iax, such as SNe 2005hk and 2012Z. Its well-sampled early light curve allows strict limits on companion interaction to be placed. Main-sequence companion stars with masses of 2 and 6 M⊙ are ruled out at all viewing angles, while a helium-star companion is allowed from a narrow range of angles (140–180° away from the companion). The spectra and light curves of SN 2020udy are in good agreement with those of the ‘N5def’ deflagration model of a near Chandrasekhar-mass carbon–oxygen white dwarf. However, as has been seen in previous studies of similar luminosity events, SN 2020udy evolves slower than the model. Broad-band linear polarization measurements taken at and after peak are consistent with no polarization, in agreement with the predictions of the companion-star configuration from the early light-curve measurements. The host galaxy environment is low metallicity and is consistent with a young stellar population. Overall, we find the most plausible explosion scenario to be the incomplete disruption of a CO white dwarf near the Chandrasekhar-mass limit, with a helium-star companion.
ABSTRACT
We investigate the ability of human ‘expert’ classifiers to identify strong gravitational lens candidates in Dark Energy Survey like imaging. We recruited a total of 55 people that completed ...more than 25 per cent of the project. During the classification task, we present to the participants 1489 images. The sample contains a variety of data including lens simulations, real lenses, non-lens examples, and unlabelled data. We find that experts are extremely good at finding bright, well-resolved Einstein rings, while arcs with g-band signal to noise less than ∼25 or Einstein radii less than ∼1.2 times the seeing are rarely recovered. Very few non-lenses are scored highly. There is substantial variation in the performance of individual classifiers, but they do not appear to depend on the classifier’s experience, confidence or academic position. These variations can be mitigated with a team of 6 or more independent classifiers. Our results give confidence that humans are a reliable pruning step for lens candidates, providing pure and quantifiably complete samples for follow-up studies.
ABSTRACT
We test the adequacy of ultraviolet (UV) spectra for characterizing the outer structure of Type Ia supernova (SN) ejecta. For this purpose, we perform spectroscopic analysis for ASASSN-14lp, ...a normal SN Ia showing low continuum in the mid-UV regime. To explain the strong UV suppression, two possible origins have been investigated by mapping the chemical profiles over a significant part of their ejecta. We fit the spectral time series with mid-UV coverage obtained before and around maximum light by HST, supplemented with ground-based optical observations for the earliest epochs. The synthetic spectra are calculated with the one-dimensional MC radiative transfer code tardis from self-consistent ejecta models. Among several physical parameters, we constrain the abundance profiles of nine chemical elements. We find that a distribution of 56Ni (and other iron-group elements) that extends towards the highest velocities reproduces the observed UV flux well. The presence of radioactive material in the outer layers of the ejecta, if confirmed, implies strong constraints on the possible explosion scenarios. We investigate the impact of the inferred 56Ni distribution on the early light curves with the radiative transfer code turtls, and confront the results with the observed light curves of ASASSN-14lp. The inferred abundances are not in conflict with the observed photometry. We also test whether the UV suppression can be reproduced if the radiation at the photosphere is significantly lower in the UV regime than the pure Planck function. In this case, solar metallicity might be sufficient enough at the highest velocities to reproduce the UV suppression.
Abstract
We present the discovery of ZTF 21aaoryiz/SN 2021fcg—an extremely low luminosity Type Iax supernova. SN 2021fcg was discovered by the Zwicky Transient Facility in the star-forming galaxy ...IC0512 at a distance of ≈27 Mpc. It reached a peak absolute magnitude of
M
r
= −12.66 ± 0.20 mag, making it the least luminous thermonuclear supernova discovered to date. The
E
(
B
−
V
) contribution from the underlying host galaxy is unconstrained. However, even if it were as large as 0.5 mag, the peak absolute magnitude would be
M
r
= −13.78 ± 0.20 mag—still consistent with being the lowest-luminosity SN. Optical spectra of SN 2021fcg taken at 37 and 65 days post-maximum show strong Ca
ii
, Ca
ii
, and Na
i
D emission and several weak Fe
ii
emission lines. The Ca
ii
emission in the two spectra has extremely low velocities of ≈1300 and 1000 km s
−1
, respectively. The spectra very closely resemble those of the very low luminosity Type Iax supernovae SN 2008 ha, SN 2010ae, and SN 2019gsc taken at similar phases. The peak bolometric luminosity of SN 2021fcg is ≈
2.5
−
0.3
+
1.5
×
10
40
erg s
−1
, which is a factor of 3 lower than that for SN 2008 ha. The bolometric lightcurve of SN 2021fcg is consistent with a very low ejected nickel mass (
M
Ni
≈
0.8
−
0.5
+
0.4
×
10
−
3
M
⊙
). The low luminosity and nickel mass of SN 2021fcg pose a challenge to the picture that low-luminosity SNe Iax originate from deflagrations of near-
M
ch
hybrid carbon–oxygen–neon white dwarfs. Instead, the merger of a carbon–oxygen and oxygen–neon white dwarf is a promising model to explain SN 2021fcg.
The effect of display size on ultrasound interpretation Magee, Mark A.; Au, Arthur K.; Flashner, Lillian ...
The American journal of emergency medicine,
January 2022, 2022-Jan, 2022-01-00, 20220101, Letnik:
51
Journal Article
Recenzirano
Odprti dostop
Ultrasound (US) is an essential component of emergency department patient care. US machines have become smaller and more affordable. Handheld ultrasound (HUS) machines are even more portable and easy ...to use at the patient's bedside. However, miniaturization may come with consequences. The ability to accurately interpret ultrasound on a smaller screen is unknown. This pilot study aims to assess how screen size affects the ability of emergency medicine clinicians to accurately interpret US videos.
This pilot study enrolled a prospective convenience sample of emergency medicine physicians. Participants completed a survey and were randomized to interpret US videos starting with either a phone-sized screen or a laptop-sized screen, switching to the other device at the halfway point. 50 unique US videos depicting right upper quadrant (RUQ) views of the Focused Assessment with Sonography in Trauma (FAST) examination were chosen for inclusion in the study. There were 25 US videos per device. All of the images were previously obtained on a cart-based machine (Mindray M9) and preselected by the study authors. Participants answered “Yes” or “No” in response to whether they identified free fluid. The time that each participant took to interpret each video was also recorded. Following the assessment, participants completed a post-interpretation survey. The goal of the pilot was to determine the accuracy of image interpretation on a small screen as compared to a laptop-sized screen. Statistical analyses were performed using MATLAB (The MathWorks, Inc., Natick, MA). Nonparametric statistical tests were utilized to compare subgroups, with a Wilcoxon signed rank test used for paired data and a Wilcoxon rank sum test for unpaired data.
52 emergency medicine physicians were enrolled in the study. The median accuracy of US interpretation for phone versus laptop image screen was 88.0% and 87.6% (p = 0.67). The mean time to interpret with phone versus laptop screen was 293 and 290 s (p = 0.66).
The study found no statistically significant difference in the accuracy of US interpretation nor time spent interpreting when the pre-selected RUQ videos generated on a cart-based ultrasound machine were reviewed on a phone-sized versus a laptop-sized screen. This pilot study suggests that the accuracy of US interpretation may not be dependent upon the size of the screen utilized.
Numerous studies have demonstrated the accuracy of point-of-care ultrasound (POCUS). Portable, handheld devices have expanded the clinical scope of POCUS at a fraction of the cost of traditional, ...cart-based models. There is a paucity of data assessing the diagnostic accuracy of portable devices. Our objective in this study was to compare the diagnostic accuracy of a portable device with a cart-based model.
This was an institutional review board-approved, observational, prospective, randomized clinical trial (NCT05196776) of a convenience sample of adult patients who presented to a university-based health system. Patients who required a cardiac, lung, renal, aorta, or biliary POCUS were randomized to a portable device or to a cart-based model. We hypothesized that the cart-based model would have a 90% diagnostic accuracy vs 70% for the handheld device. To detect a 20% difference, the sample size was calculated to be 98, with 49 patients randomized to each arm. We used standard 2x2 tables to calculate test characteristics with 95% confidence intervals (CI).
A total of 110 patients were enrolled, with 56 patients randomized to the cart-based model and 54 to the handheld device. The sensitivity, specificity, and diagnostic accuracy of the cart-based vs handheld were 77.8% (40-97.2) vs 92.9% (66.1-99.8), 91.5% (79.6-97.6) vs 92.3% (79.1-98.4%), and 89.3% (78.1-96) vs 92.5% (81.8-97.9), respectively.
The diagnostic accuracy of a portable, handheld device is similar to that of a cart-based model.
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