Interaction-powered supernovae (SNe) explode within an optically-thick circumstellar medium (CSM) that could be ejected during eruptive events. To identify and characterize such pre-explosion ...outbursts we produce forced-photometry light curves for 196 interacting SNe, mostly of Type IIn, detected by the Zwicky Transient Facility between early 2018 and June 2020. Extensive tests demonstrate that we only expect a few false detections among the 70,000 analyzed pre-explosion images after applying quality cuts and bias corrections. We detect precursor eruptions prior to 18 Type IIn SNe and prior to the Type Ibn SN2019uo. Precursors become brighter and more frequent in the last months before the SN and month-long outbursts brighter than magnitude -13 occur prior to 25% (5 - 69%, 95% confidence range) of all Type IIn SNe within the final three months before the explosion. With radiative energies of up to \(10^{49}\,\text{erg}\), precursors could eject \(\sim1\,\text{M}_\odot\) of material. Nevertheless, SNe with detected precursors are not significantly more luminous than other SNe IIn and the characteristic narrow hydrogen lines in their spectra typically originate from earlier, undetected mass-loss events. The long precursor durations require ongoing energy injection and they could, for example, be powered by interaction or by a continuum-driven wind. Instabilities during the neon and oxygen burning phases are predicted to launch precursors in the final years to months before the explosion; however, the brightest precursor is 100 times more energetic than anticipated.
The first binary neutron star merger, GW170817, was accompanied by a radioactivity-powered optical/infrared transient called a kilonova. To date, no compelling kilonova has been found during optical ...surveys of the sky, independent of gravitational-wave triggers. In this work, we searched the first 23 months of the Zwicky Transient Facility (ZTF) data stream for candidate kilonovae in the form of rapidly evolving transients. We combined ZTF alert queries with forced point-spread-function photometry and nightly flux stacking to increase our sensitivity to faint and fast transients. Automatic queries yielded \(>11,200\) candidates, 24 of which passed quality checks and strict selection criteria based on a grid of kilonova models tailored for both binary neutron star and neutron star-black hole mergers. None of the candidates in our sample was deemed a possible kilonova after thorough vetting, catalog cross-matching, and study of their color evolution. The sources that passed our selection criteria are dominated by Galactic cataclysmic variables. In addition, we identified two fast transients at high Galactic latitude, one of which is the confirmed afterglow of long-duration GRB190106A, and the other is a possible cosmological afterglow. Using a survey simulation code, we constrained the kilonova rate for a range of models including top-hat and linearly decaying light curves and synthetic light curves obtained with radiative transfer simulations. For prototypical GW170817-like kilonovae, we constrain the rate to be \(R < 1775\) Gpc\(^{-3}\) yr\(^{-1}\) at 95% confidence level by requiring at least 2 high-significance detections. By assuming a population of kilonovae with the same geometry and composition of GW170817 observed under a uniform viewing angle distribution, we obtained a constraint on the rate of \(R < 4029\) Gpc\(^{-3}\) yr\(^{-1}\).
We present a systematic search for optical counterparts to 13 gravitational wave (GW) triggers involving at least one neutron star during LIGO/Virgo's third observing run. We searched binary neutron ...star (BNS) and neutron star black hole (NSBH) merger localizations with the Zwicky Transient Facility (ZTF) and undertook follow-up with the Global Relay of Observatories Watching Transients Happen (GROWTH) collaboration. The GW triggers had a median localization of 4480 deg^2, median distance of 267 Mpc and false alarm rates ranging from 1.5 to 1e-25 per yr. The ZTF coverage had a median enclosed probability of 39%, median depth of 20.8mag, and median response time of 1.5 hr. The O3 follow-up by the GROWTH team comprised 340 UVOIR photometric points, 64 OIR spectra, and 3 radio. We find no promising kilonova (radioactivity-powered counterpart) and we convert the upper limits to constrain the underlying kilonova luminosity function. Assuming that all kilonovae are at least as luminous as GW170817 at discovery (-16.1mag), we calculate our joint probability of detecting zero kilonovae is only 4.2%. If we assume that all kilonovae are brighter than -16.6mag (extrapolated peak magnitude of GW170817) and fade at 1 mag/day (similar to GW170817), the joint probability of zero detections is 7%. If we separate the NSBH and BNS populations, the joint probability of zero detections, assuming all kilonovae are brighter than -16.6mag, is 9.7% for NSBH and 7.9% for BNS mergers. Moreover, <57% (<89%) of putative kilonovae could be brighter than -16.6mag assuming flat (fading) evolution, at 90% confidence. If we further account for the online terrestrial probability for each GW trigger, we find that <68% of putative kilonovae could be brighter than -16.6mag. Comparing to model grids, we find that some kilonovae must have Mej < 0.03 Msun or Xlan>1e-4 or phi>30deg to be consistent with our limits. (Abridged)
(Abridged) Using the Zwicky Transient Facility alert stream, we are conducting a large campaign to spectroscopically classify all transients occurring in galaxies in the Census of the Local Universe ...(CLU) catalog. The aim of the experiment is to construct a spectroscopically complete, volume-limited sample of transients coincident within 100" of CLU galaxies out to 200 Mpc, and to a depth of 20 mag. We describe the survey design and spectroscopic completeness from the first 16 months of operations. 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 (out of 754 spectroscopically classified SNe). We report the detection of eight Calcium rich gap transients, and constrain their volumetric rate to be at least \(\approx 15\pm5\)% of the SN Ia rate. Combining this sample with ten events from the literature, we find a likely continuum of spectroscopic properties ranging from events with SN Ia-like features (Ca-Ia objects) to SN Ib/c-like features (Ca-Ib/c objects) at peak light. Within the Ca-Ib/c events, we find two populations of events distinguished by their red (\(g - r \approx 1.5\) mag) or green (\(g - r \approx 0.5\) mag) spectral colors at \(r\)-band peak, wherein redder events show strong line blanketing signatures, slower light curves, weaker He lines and lower Ca II/O I in the nebular phase. Together, we find that the spectroscopic continuum, volumetric rates and striking old environments are consistent with the explosive burning of He shells on low mass white dwarfs. We posit that Ca-Ia and red Ca-Ib/c objects are consistent with the double detonation of He shells with high He burning efficiency, while green Ca-Ib/c objects could arise from less efficient He burning scenarios such as detonations in low density He shells or He shell deflagrations.
On 2019 August 14, the Advanced LIGO and Virgo interferometers detected the high-significance gravitational wave (GW) signal S190814bv. The GW data indicated that the event resulted from a neutron ...star--black hole (NSBH) merger, or potentially a low-mass binary black hole merger. Due to the low false alarm rate and the precise localization (23 deg\(^2\) at 90\%), S190814bv presented the community with the best opportunity yet to directly observe an optical/near-infrared counterpart to a NSBH merger. To search for potential counterparts, the GROWTH collaboration performed real-time image subtraction on 6 nights of public Dark Energy Camera (DECam) images acquired in the three weeks following the merger, covering \(>\)98\% of the localization probability. Using a worldwide network of follow-up facilities, we systematically undertook spectroscopy and imaging of optical counterpart candidates. Combining these data with a photometric redshift catalog, we ruled out each candidate as the counterpart to S190814bv and we placed deep, uniform limits on the optical emission associated with S190814bv. For the nearest consistent GW distance, radiative transfer simulations of NSBH mergers constrain the ejecta mass of S190814bv to be \(M_\mathrm{ej} < 0.04\)~\(M_{\odot}\) at polar viewing angles, or \(M_\mathrm{ej} < 0.03\)~\(M_{\odot}\) if the opacity is \(\kappa < 2\)~cm\(^2\)g\(^{-1}\). Assuming a tidal deformability for the neutron star at the high end of the range compatible with GW170817 results, our limits would constrain the BH spin component aligned with the orbital momentum to be \( \chi < 0.7\) for mass ratios \(Q < 6\), with weaker constraints for more compact neutron stars. We publicly release the photometry from this campaign at http://www.astro.caltech.edu/~danny/static/s190814bv.
The effect of sainfoin (Onobrychis viciifolia) against ovine coccidia was evaluated in vivo and in vitro. In 3 in vivo trials weaned lambs were allocated into two treatment groups receiving diets ...with either lucerne (Medicago sativa) or sainfoin. During the trials, which lasted for 7 (trial 1) or 8 weeks (trials 2 and 3), oocysts per gram of faeces (OPGs), faecal scores and weight gain were recorded. In two of the experiments (trials 1 and 3) a reduction in the mean oocyst excretion rates was observed, starting three to four weeks after sainfoin hay feeding. This reduction ranged between 21.3% (trial 1) and 61.7% (trial 3) compared to the control values. As a result, a decrease in the total number of oocysts excreted (expressed as the mean area under the curve of the OPG) was observed from week 4 to the end of the two trials, respectively (trial 1: 42.6% reduction, p=0.05; trial 3: 52.4% reduction, p=0.06). The results did not show any significant diet effect on lamb growth rates and faecal scores. In the in vitro experiments the effect of 39 sainfoin extracts were tested in an oocyst sporulation inhibition assay. The Eimeria oocysts sporulation inhibition throughout the experiments did not exceed 10.7%, showing that extracts of this forages do not have a significant inhibitory effect on Eimeria oocyst sporulation. This was an initial attempt to investigate a possible anticoccidial effect of sainfoin and further studies are needed in order to better understand its mode of action against Eimeria.
The effect of different treatment protocols using the triazinone compounds diclazuril and toltrazuril on Eimeria oocyst excretion, diarrhoea and weight gain was evaluated in the present study. The ...protocols were designed in order to best fit to common management practices in dairy production systems as applied in Greece. During the first two trials comparative preventive (11 days after birth) and therapeutic (18 days after birth) single treatments using either drug were performed on an intensive farm. In Trial 3 the efficacy of a repeated diclazuril treatment after weaning (at the start and 4 weeks later) of the animals in a semi-intensive farm was tested. The last trial was performed in order to assess the effect of a single oral dose of toltrazuril after weaning of the animals on the same farm. During an observation period of 6–7 weeks after treatment animals in all trials were clinically examined for diarrhoea and faecal samples were regularly monitored for Eimeria oocysts at weekly intervals. Body weight was also determined at the start and end of each trial. A single treatment with toltrazuril resulted in a significant reduction of oocyst excretion over the study period compared to the control, with very high efficacy values during the first 2–3 weeks after treatment, irrespective of the treatment protocol and the management system applied. This in general could not be confirmed in the protocols using diclazuril, which showed a much lower and mostly variable efficacy pattern.
