The Zwicky Transient Facility Census of the Local Universe. I. Systematic Search for Calcium-rich Gap Transients Reveals Three Related Spectroscopic Subclasses

Using the Zwicky Transient Facility alert stream, we are conducting a large spectroscopic campaign to construct a complete, volume-limited sample of transients brighter than 20 mag, and coincident within 100" of galaxies in the Census of the Local Universe catalog. We describe the experiment design and spectroscopic completeness from the first 16 months of operations, which have classified 754 supernovae. We present results from a systematic search for calcium-rich gap transients in the sample of 22 low-luminosity (peak absolute magnitude M > −17), hydrogen-poor events found in the experiment. We report the detection of eight new events, and constrain their volumetric rate to ≳ 15% ± 5% of the SN Ia rate. Combining this sample with 10 previously known events, we find a likely continuum of spectroscopic properties ranging from events with SN Ia–like features (Ca-Ia objects) to those with SN Ib/c–like features (Ca-Ib/c objects) at peak light. Within the Ca-Ib/c events, we find two populations distinguished by their red (g − r ≈ 1.5 mag) or green (g - r ≈ 0.5 mag) colors at the r-band peak, wherein redder events show strong line blanketing features and slower light curves (similar to Ca-Ia objects), weaker He lines, and lower [Ca ii]/[O i] in the nebular phase. We find that all together the spectroscopic continuum, volumetric rates, and striking old environments are consistent with the explosive burning of He shells on low-mass white dwarfs. We suggest that Ca-Ia and red Ca-Ib/c objects arise from the double detonation of He shells, while green Ca-Ib/c objects are consistent with low-efficiency burning scenarios like detonations in low-density shells or deflagrations

Novel Methods for Analysing Bacterial Tracks Reveal Persistence in Rhodobacter sphaeroides

Tracking bacteria using video microscopy is a powerful experimental approach to probe their motile behaviour. The trajectories obtained contain much information relating to the complex patterns of bacterial motility. However, methods for the quantitative analysis of such data are limited. Most swimming bacteria move in approximately straight lines, interspersed with random reorientation phases. It is therefore necessary to segment observed tracks into swimming and reorientation phases to extract useful statistics. We present novel robust analysis tools to discern these two phases in tracks. Our methods comprise a simple and effective protocol for removing spurious tracks from tracking datasets, followed by analysis based on a two-state hidden Markov model, taking advantage of the availability of mutant strains that exhibit swimming-only or reorientating-only motion to generate an empirical prior distribution. Using simulated tracks with varying levels of added noise, we validate our methods and compare them with an existing heuristic method. To our knowledge this is the first example of a systematic assessment of analysis methods in this field. The new methods are substantially more robust to noise and introduce less systematic bias than the heuristic method. We apply our methods to tracks obtained from the bacterial species Rhodobacter sphaeroides and Escherichia coli. Our results demonstrate that R. sphaeroides exhibits persistence over the course of a tumbling event, which is a novel result with important implications in the study of this and similar species

SN 2022crv: IIb, Or Not IIb: That is the Question

We present optical and near-infrared observations of SN~2022crv, a stripped envelope supernova in NGC~3054, discovered within 12 hrs of explosion by the Distance Less Than 40 Mpc Survey. We suggest SN~2022crv is a transitional object on the continuum between SNe Ib and SNe IIb. A high-velocity hydrogen feature ($\sim$$-$20,000 -- $-$16,000 $\rm km\,s^{-1}$) was conspicuous in SN~2022crv at early phases, and then quickly disappeared around maximum light. By comparing with hydrodynamic modeling, we find that a hydrogen envelope of $\sim 10^{-3}$ \msun{} can reproduce the behaviour of the hydrogen feature observed in SN~2022crv. The early light curve of SN~2022crv did not show envelope cooling emission, implying that SN~2022crv had a compact progenitor with extremely low amount of hydrogen. The analysis of the nebular spectra shows that SN~2022crv is consistent with the explosion of a He star with a final mass of $\sim$4.5 -- 5.6 \msun{} that has evolved from a $\sim$16 -- 22 \msun{} zero-age main sequence star in a binary system with about 1.0 -- 1.7 \msun{} of oxygen finally synthesized in the core. The high metallicity at the supernova site indicates that the progenitor experienced a strong stellar wind mass loss. In order to retain a small amount of residual hydrogen at such a high metallicity, the initial orbital separation of the binary system is likely larger than $\sim$1000~$\rm R_{\odot}$. The near-infrared spectra of SN~2022crv show a unique absorption feature on the blue side of He I line at $\sim$1.005~$\mu$m. This is the first time that such a feature has been observed in a Type Ib/IIb, and could be due to \ion{Sr}{2}. Further detailed modelling on SN~2022crv can shed light on the progenitor and the origin of the mysterious absorption feature in the near infrared.Comment: 33 pages, 23 figures, submitted to Ap

Strong Carbon Features and a Red Early Color in the Underluminous Type Ia SN 2022xkq

We present optical, infrared, ultraviolet, and radio observations of SN 2022xkq, an underluminous fast-declining type Ia supernova (SN Ia) in NGC 1784 ($\mathrm{D}\approx31$ Mpc), from $<1$ to 180 days after explosion. The high-cadence observations of SN 2022xkq, a photometrically transitional and spectroscopically 91bg-like SN Ia, cover the first days and weeks following explosion which are critical to distinguishing between explosion scenarios. The early light curve of SN 2022xkq has a red early color and exhibits a flux excess which is more prominent in redder bands; this is the first time such a feature has been seen in a transitional/91bg-like SN Ia. We also present 92 optical and 19 near-infrared (NIR) spectra, beginning 0.4 days after explosion in the optical and 2.6 days after explosion in the NIR. SN 2022xkq exhibits a long-lived C I 1.0693 $\mu$m feature which persists until 5 days post-maximum. We also detect C II $\lambda$6580 in the pre-maximum optical spectra. These lines are evidence for unburnt carbon that is difficult to reconcile with the double detonation of a sub-Chandrasekhar mass white dwarf. No existing explosion model can fully explain the photometric and spectroscopic dataset of SN 2022xkq, but the considerable breadth of the observations is ideal for furthering our understanding of the processes which produce faint SNe Ia.Comment: 38 pages, 16 figures, accepted for publication in ApJ, the figure 15 input models and synthetic spectra are now available at https://zenodo.org/record/837925

Class 1C antiarrhythmic drugs in atrial fibrillation and coronary artery disease

Class 1C antiarrhythmic drugs (AAD) are effective first-line agents for atrial fibrillation (AF) treatment. However, these agents commonly are avoided in patients with known coronary artery disease (CAD), due to known increased risk in the post-myocardial infarction population. Whether 1C AADs are safe in patients with CAD but without clinical ischemia or infarct is unknown. Reduced coronary flow capacity (CFC) on positron emission tomography (PET) reliably identifies myocardial regions supplied by vessels with CAD causing flow limitation.To assess whether treatment with 1C AADs increases mortality in patients without known CAD but with CFC indicating significantly reduced coronary blood flow.In this pilot study, we compared patients with AF and LVEF ≥50% who were treated with 1C AADs, to age-matched AF patients without 1C AAD treatment. No patient had clinically evident CAD (i.e., reversible perfusion defect, known ≥70% epicardial lesion, PCI, CABG, or myocardial infarction). All patients had PET-based quantification of stress myocardial blood flow (sMBF) and CFC. Death was assessed by clinical follow-up and SSDI search.78 patients with 1C AAD exposure were matched to 78 controls. Over a mean follow-up of 2.0 years, the groups had similar survival (p=0.54). Among patients with CFC indicating the presence of occult CAD (i.e., reduced CFC involving ≥50% of myocardium), 1C-treated patients had survival similar to (p=0.44) those not treated with 1C agents.In a limited population of AF patients with preserved LV function and PET CFC indicating occult CAD, treatment with 1C AADs appears not to increase mortality. A larger study would be required to confidently assess safety of these drugs in this context. This article is protected by copyright. All rights reserved

Utility of serial measurement of biomarkers of cardiovascular stress and inflammation in systolic dysfunction

Evidence links markers of systemic inflammation and heart failure (HF) with ventricular arrhythmias (VA) and/or death. Biomarker levels, and the risk they indicate, may vary over time. We evaluated the utility of serial laboratory measurements of inflammatory biomarkers and HF, using time-dependent analysis.We prospectively enrolled ambulatory patients with left ventricular ejection fraction (LVEF) ≤35% and a primary-prevention implanted cardioverter-defibrillator (ICD). Levels of established inflammatory biomarkers [C-reactive protein, erythrocyte sedimentation rate (ESR), suppression of tumourigenicity 2 (ST2), tumour necrosis factor alpha (TNF-α)] and brain natriuretic peptide (BNP) were assessed at 3-month intervals for 1 year. We assessed relationships between biomarkers modelled as time-dependent variables, VA, and death. Among 196 patients (66±14 years, LVEF 23±8%), 33 experienced VA, and 18 died. Using only baseline values, BNP predicted VA, and both BNP and ST2 predicted death. Using serial measurements at 3-month intervals, time-varying BNP independently predicted VA, and time-varying ST2 independently predicted death. C-statistic analysis revealed no significant benefit to repeated testing compared with baseline-only measurement. C-reactive protein, ESR, and TNF-α, either at baseline or over time, did not predict either endpoint.In stable ambulatory patients with systolic cardiomyopathy and an ICD, BNP predicts ventricular tachyarrhythmia, and ST2 predicts death. Repeated laboratory measurements over a year's time do not improve risk stratification beyond baseline measurement alone.Clinicaltrials.gov NCT01892462 (https://clinicaltrials.gov/ct2/show/NCT01892462)

Positron emission tomography absolute stress myocardial blood flow for risk stratification in nonischemic cardiomyopathy

Sudden cardiac death is a substantial cause of mortality in patients with cardiomyopathy, but evidence supporting implantable cardioverter defibrillator (ICD) implantation is less robust in nonischemic cardiomyopathy (NICM) than in ischemic cardiomyopathy. Improved risk stratification is needed. We assessed whether absolute quantification of stress myocardial blood flow (sMBF) measured by positron emission tomography (PET) predicts ventricular arrhythmias (VA) and/or death in patients with NICM.In this pilot study, we prospectively followed patients with NICM (LVEF ≤35%) and an ICD who underwent cardiac PET stress imaging with sMBF quantification. NICM was defined as absence of angiographic obstructive coronary stenosis, significant relative perfusion defects on imaging, coronary revascularization, or acute coronary syndrome. Endpoints were appropriate device therapy for VA and all-cause mortality. Subgroup analysis was performed in patients who had no prior history of VA (i.e., the primary prevention population).We followed 37 patients (60±14 years, 46% male) for 41±23 months. The median sMBF was 1.56 mL/g/min [IQR 1.00-1.82]. Lower sMBF predicted VA, both in the whole population (HR for each 0.1 mL/g/min increase: 0.84, P=0.015) and in the primary prevention subset (n=27; HR for each 0.1 mL/g/min increase: 0.81, P=0.049). Patients with sMBF below the median had significantly more VA than those above the median, both in the whole population (P=0.004) and in the primary prevention subset (P=0.046). Estimated 3-year VA rates in the whole population were 67% among low-flow patients vs. 13% among high-flow patients, and 39% vs. 8% among primary-prevention patients. sMBF did not predict all-cause mortality.In patients with NICM, lower sMBF predicts VA. This relationship may be useful for risk stratification for ventricular arrhythmia and decision-making regarding ICD implantation. This article is protected by copyright. All rights reserved