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Tidal disruption events (TDEs) offer a unique way to study dormant black holes. While the number of observed TDEs has grown thanks to the emergence of wide-field surveys in the past few decades, questions regarding the nature of the observed optical, UV, and X-ray emission remain. We present a uniformly selected sample of 30 spectroscopically classified TDEs from the Zwicky Transient Facility Phase I survey operations with follow-up \textit{Swift} UV and X-ray observations. Through our investigation into correlations between light curve properties, we recover a shallow positive correlation between the peak bolometric luminosity and decay timescales. We introduce a new spectroscopic class of TDE, TDE-featureless, which are characterized by featureless optical spectra. The new TDE-featureless class shows larger peak bolometric luminosities, peak blackbody temperatures, and peak blackbody radii. We examine the differences between the X-ray bright and X-ray faint populations of TDEs in this sample, finding that X-ray bright TDEs show higher peak blackbody luminosities than the X-ray faint sub-sample. This sample of optically selected TDEs is the largest sample of TDEs from a single survey yet, and the systematic discovery, classification, and follow-up of this sample allows for robust characterization of TDE properties, an important stepping stone looking forward toward the Rubin era., Comment: 44 pages, 22 figures, 9 tables, accepted to ApJ

To (a) evaluate the attitudes of local businesses, residents, and visitors regarding the trial of a voluntary smokefree and vapefree zone covering the central business streets of a popular tourist town in the South Island of New Zealand, and (b) observe smoking and vaping prevalence before and during the trial, to inform national and local smokefree environment advocacy work.The six-month smokefree and vapefree trial included an embedded mixed methods project evaluation to capture a range of stakeholder groups' views about the smokefree and vapefree zone. Data collection methods included face-to-face interviews, non-random pen and paper and online surveys, and observational scans. Qualitative data were analysed using a systematic iterative thematic approach, and simple descriptive quantitative analyses were applied to the survey data.The analysis synthesised information from almost 1,000 respondents. A large majority of respondents supported smokefree and vapefree within the zone (visitors 84%; residents 67%; businesses 63%). A majority of responding visitors indicated that the same rules should apply to both smoking and vaping and that they would be either more likely or as likely to visit other tourist destinations in New Zealand if they had smokefree and vapefree zones. Implementing the initiative was associated with a reduction in the number of people visibly smoking and vaping within the zone.The weight of evidence from the project evaluation points towards a net benefit both for individuals and for the community from implementing voluntary smokefree and vapefree zones in tourist destinations in New Zealand.

Background Seasonal malaria chemoprevention (SMC) involves administering antimalarial drugs at monthly intervals during the high malaria transmission period to children aged 3 to 59 months as recommended by the World Health Organization. Typically, a full SMC course is administered over four monthly cycles from July to October, coinciding with the rainy season. However, an analysis of rainfall patterns suggest that the malaria transmission season is longer and starting as early as June in the south of Burkina Faso, leading to a rise in cases prior to the first cycle. This study assessed the acceptability and feasibility of extending SMC from four to five cycles to coincide with the earlier rainy season in Mangodara health district. Methods The mixed-methods study was conducted between July and November 2019. Quantitative data were collected through end-of-cycle and end-of-round household surveys to determine the effect of the additional cycle on the coverage of SMC in Mangodara. The data were then compared with 22 other districts where SMC was implemented by Malaria Consortium. Eight focus group discussions were conducted with caregivers and community distributors and 11 key informant interviews with community, programme and national-level stakeholders. These aimed to determine perceptions of the acceptability and feasibility of extending SMC to five cycles. Results The extension was perceived as acceptable by caregivers, community distributors and stakeholders due to the positive impact on the health of children under five. However, many community distributors expressed concern over the feasibility, mainly due to the clash with farming activities in June. Stakeholders highlighted the need for more evidence on the impact of the additional cycle on parasite resistance prior to scale-up. End-of-cycle survey data showed no difference in coverage between five SMC cycles in Mangodara and four cycles in the 22 comparison districts. Conclusions The additional cycle should begin early in the day in order to not coincide with the agricultural activities of community distributors. Continuous sensitisation at community level is critical for the sustainability of SMC and acceptance of an additional cycle, which should actively engage male caregivers. Providing additional support in proportion to the increased workload from a fifth cycle, including timely remuneration, is critical to avoid the demotivation of community distributors. Further studies are required to understand the effectiveness, including cost-effectiveness, of tailoring SMC according to the rainy season. Understanding the impact of an additional cycle on parasite resistance to SPAQ is critical to address key informants’ concerns around the deviation from the current four-cycle policy recommendation.

While it is difficult to observe the first black hole seeds in the early Universe, we can study intermediate mass black holes (IMBHs) in local dwarf galaxies for clues about their origins. In this paper we present a sample of variability--selected AGN in dwarf galaxies using optical photometry from the Zwicky Transient Facility (ZTF) and forward--modeled mid--IR photometry of time--resolved Wide--field Infrared Survey Explorer ({\it WISE}) coadded images. We found that 44 out of 25,714 dwarf galaxies had optically variable AGN candidates, and 148 out of 79,879 dwarf galaxies had mid--IR variable AGN candidates, corresponding to active fractions of $0.17\pm0.03$\% and $0.19\pm0.02$\% respectively. We found that spectroscopic approaches to AGN identification would have missed 81\% of our ZTF IMBH candidates and 69\% of our {\it WISE} IMBH candidates. Only $9$ candidates have been detected previously in radio, X-ray, and variability searches for dwarf galaxy AGN. The ZTF and {\it WISE} dwarf galaxy AGN with broad Balmer lines have virial masses down to $10^{5.5}M_\odot$ and for the rest of the sample, BH masses predicted from host galaxy mass range between $10^{5.2}M_\odot, Comment: Submitted to ApJ. 25 pages, 10 figures, 4 tables

Background Bi-annual high dose vitamin A supplements administered to children aged 6–59 months can significantly reduce child mortality, but vitamin A supplementation (VAS) coverage is low in Nigeria. The World Health Organization recommends that VAS be integrated into other public health programmes which are aimed at improving child survival. Seasonal malaria chemoprevention (SMC) provides a ready platform for VAS integration to improve health outcomes. This study explored the feasibility and acceptability of integrating VAS with SMC in one local government area in Sokoto State. Methods A concurrent QUAN-QUAL mixed methods study was used to assess the feasibility and acceptability of co-implementing VAS with SMC in one LGA of Sokoto state. Existing SMC implementation tools and job aids were revised and SMC and VAS were delivered using a door-to-door approach. VAS and SMC coverage were subsequently assessed using questionnaires administered to 188 and 197 households at baseline and endline respectively. The qualitative component involved key informant interviews and focus group discussions with policymakers, programme officials and technical partners to explore feasibility and acceptability. Thematic analysis was carried out on the qualitative data. Results At endline, the proportion of children who received at least one dose of VAS in the last six months increased significantly from 2 to 59% (p p = 0.412) at endline. There was no significant change (p = 0.264) in the quality of SMC, measured by proportion of children receiving their first dose as directly observed treatment (DOT), at baseline (54%) compared to endline (68%). The qualitative findings are presented as two overarching themes relating to feasibility and acceptability of the integrated VAS-SMC strategy, and within each, a series of sub-themes describe study participants’ views of important considerations in implementing the strategy. Conclusion This study showed that it is feasible and acceptable to integrate VAS with SMC delivery in areas of high seasonal malaria transmission such as northern Nigeria, where SMC campaigns are implemented. SMC-VAS integrated campaigns can significantly increase vitamin A coverage but more research is required to demonstrate the feasibility of this integration in different settings and on a larger scale.

Background Seasonal malaria chemoprevention (SMC) is a WHO-recommended intervention for children aged 3–59 months living in areas of high malaria transmission to provide protection against malaria during the rainy season. Operational guidelines were developed, based on WHO guidance, to support countries to mitigate the risk of coronavirus disease 2019 (COVID-19) transmission within communities and among community distributors when delivering SMC. Methods A cross-sectional study to determine adherence to infection prevention and control (IPC) measures during two distribution cycles of SMC in Nigeria, Chad and Burkina Faso. Community distributors were observed receiving equipment and delivering SMC. Adherence across six domains was calculated as the proportion of indications in which the community distributor performed the correct action. Focus group discussions were conducted with community distributors to understand their perceptions of the IPC measures and barriers and facilitators to adherence. Results Data collectors observed community distributors in Nigeria (n = 259), Burkina Faso (n = 252) and Chad (n = 266) receiving IPC equipment and delivering SMC. Adherence to IPC indications varied. In all three countries, adherence to mask use was the highest (ranging from 73.3% in Nigeria to 86.9% in Burkina Faso). Adherence to hand hygiene for at least 30 s was low (ranging from 3.6% in Nigeria to 10.3% in Burkina Faso) but increased substantially when excluding the length of time spent hand washing (ranging from 36.7% in Nigeria to 61.4% in Burkina Faso). Adherence to safe distancing in the compound ranged from 5.4% in Chad to 16.4% in Nigeria. In Burkina Faso and Chad, where disinfection wipes widely available compliance with disinfection of blister packs for SMC was low (17.4% in Burkina Faso and 16.9% in Chad). Community distributors generally found the IPC measures acceptable, however there were barriers to optimal hand hygiene practices, cultural norms made social distancing difficult to adhere to and caregivers needed assistance to administer the first dose of SMC. Conclusion Adherence to IPC measures for SMC delivery during the COVID-19 pandemic varied across domains of IPC, but was largely insufficient, particularly for hand hygiene and safe distancing. Improvements in provision of protective equipment, early community engagement and adaptations to make IPC measures more feasible to implement could increase adherence.

Cosmic neutrinos provide a unique window into the otherwise-hidden mechanism of particle acceleration in astrophysical objects. A flux of high-energy neutrinos was discovered in 2013, and the IceCube Collaboration recently reported the likely association of one high-energy neutrino with a flare from the relativistic jet of an active galaxy pointed towards the Earth. However a combined analysis of many similar active galaxies revealed no excess from the broader population, leaving the vast majority of the cosmic neutrino flux unexplained. Here we present the likely association of a radio-emitting tidal disruption event, AT2019dsg, with a second high-energy neutrino. AT2019dsg was identified as part of our systematic search for optical counterparts to high-energy neutrinos with the Zwicky Transient Facility. The probability of finding any coincident radio-emitting tidal disruption event by chance is 0.5%, while the probability of finding one as bright in bolometric energy flux as AT2019dsg is 0.2%. Our electromagnetic observations can be explained through a multi-zone model, with radio analysis revealing a central engine, embedded in a UV photosphere, that powers an extended synchrotron-emitting outflow. This provides an ideal site for PeV neutrino production. Assuming that the association is genuine, our observations suggest that tidal disruption events with mildly-relativistic outflows contribute to the cosmic neutrino flux., Comment: Title and text modified during journal review. Version accepted for publication in Nature Astronomy

Author(s): Ward, C; Gezari, S; Frederick, S; Hammerstein, E; Nugent, P; Van Velzen, S; Drake, A; Garcia-Perez, A; Oyoo, I; Bellm, EC; Duev, DA; Graham, MJ; Kasliwal, MM; Kaye, S; Mahabal, AA; Masci, FJ; Rusholme, B; Soumagnac, MT; Yan, L | Abstract: A supermassive black hole (SMBH) ejected from the potential well of its host galaxy via gravitational wave recoil carries important information about the mass ratio and spin alignment of the pre-merger SMBH binary. Such a recoiling SMBH may be detectable as an active galactic nucleus (AGN) broad-line region offset by up to 10 kpc from a disturbed host galaxy. We describe a novel methodology using forward modeling with The Tractor to search for such offset AGNs in a sample of 5493 optically variable AGNs detected with the Zwicky Transient Facility (ZTF). We present the discovery of nine AGNs that may be spatially offset from their host galaxies and are candidates for recoiling SMBHs. Five of these offset AGNs exhibit double-peaked broad Balmer lines, which may have arisen from unobscured accretion disk emission, and four show radio emission indicative of a relativistic jet. The fraction of double-peaked emitters in our spatially offset AGN sample is significantly larger than the 16% double-peaked emitter fraction observed for ZTF AGNs overall. In our sample of variable AGNs we also identified 52 merging galaxies, including a new spectroscopically confirmed dual AGN. Finally, we detected the dramatic rebrightening of SDSS 1133, a previously discovered variable object and recoiling SMBH candidate, in ZTF. The flare was accompanied by the reemergence of strong P Cygni line features, indicating that SDSS 1133 may be an outbursting luminous blue variable star.

A common non-pharmaceutical intervention (NPI) during the Covid-19 pandemic has been group size limits. Further, educational settings of schools and universities have either fully closed or reduced their class sizes. As countries begin to reopen classrooms, a key question will be how large classes can be while still preventing local outbreaks of disease. Here we develop and analyse a simple, stochastic epidemiological model where individuals (considered as students) live in fixed households and are assigned to a fixed class for daily lessons. We compare key measures of the epidemic - the peak infected, the total infected by day 180 and the calculatedR0- as the size of class is varied. We find that class sizes of 10 could largely restrict outbreaks and often had overlapping inter-quartile ranges with our most cautious case of classes of 5. However, class sizes of 30 or more often result in large epidemics. Reducing the class size from 40 to 10 can reduceR0by over 30%, as well as signficantly reducing the numbers infected. Intermediate class sizes show considerable variation, with the total infected varying by as much as from 10% to 80% for the same class size. We show that additional in-class NPIs can limit the epidemic still further, but that reducing class sizes appears to have a larger effect on the epidemic. We do not specifically tailor our model for Covid-19, but our results stress the importance of small class sizes for preventing large outbreaks of infectious disease.

Efficient automated detection of flux-transient, re-occurring flux-variable, and moving objects is increasingly important for large-scale astronomical surveys. We present braai, a convolutional-neural-network, deep-learning real/bogus classifier designed to separate genuine astrophysical events and objects from false positive, or bogus, detections in the data of the Zwicky Transient Facility (ZTF), a new robotic time-domain survey currently in operation at the Palomar Observatory in California, USA. Braai demonstrates a state-of-the-art performance as quantified by its low false negative and false positive rates. We describe the open-source software tools used internally at Caltech to archive and access ZTF’s alerts and light curves (kowalski ), and to label the data (zwickyverse). We also report the initial results of the classifier deployment on the Edge Tensor Processing Units that show comparable performance in terms of accuracy, but in a much more (cost-) efficient manner, which has significant implications for current and future surveys.

The aims of this small-scale study were to explore the feasibility and outcomes of a parent-implemented intervention for two-year-olds at risk of language difficulties, and to explore the implications for the public health model of speech and language therapy (SLT). This adds to limited research into targeted SLT public health interventions. It is the first study to investigate early language intervention delivered by trained therapy assistants (TAs) rather than clinicians. Nine children aged between 26 and 31 months took part. Seven (78%) completed the six-session intervention. The outcome measure was the Words subscale of the Language Use Inventory. The gross motor subscale of the Ages and Stages Questionnaire was used as a control measure. Children’s skills were assessed twice before intervention and once afterwards. At baseline, six participants had expressive language delay and no wider speech, language and communication needs (SLCNs). Five of this subgroup showed language use skills within the typical range following intervention. At baseline, three participants had expressive language delay and previously undetected receptive language and/or social interaction difficulties. None of this sub-group showed improved age-adjusted language use skills following intervention. All nine participants had gross motor skills in the typical range at each time point. These exploratory findings suggest this targeted intervention is feasible. This study presents no evidence of short-term impact of this intervention for two-year-olds with expressive language delay and wider SLCNs. These findings suggest this targeted language intervention for two-year-olds may be associated with accelerated language development for some two-year-olds at risk of language difficulties because of expressive language delay; and may help identify two-year-olds with previously undetected wider SLCNs, and therefore facilitate early access to specialist support. We highlight limitations in the study size, design and outcome measures, and identify how these preliminary findings can inform future research.

Background Manual assessment of respiratory rate (RR) in children is unreliable, but remains the main method to diagnose pneumonia in low-resource settings. While automated RR counters offer a potential solution, there is currently no gold standard to validate these diagnostic aids. A video-based reference tool is proposed that allows users to annotate breaths and distortions including movement periods, allowing the exclusion of distortions from the computation of RR measures similar to how new diagnostic aids account for distortions automatically. This study evaluated the interrater agreement and acceptability of the new reference tool. Methods Annotations were based on previously recorded reference videos of children under five years old with cough and/or difficulty breathing (n = 50). Five randomly selected medical experts from a panel of ten annotated each video. RR measures (breaths per minute, bpm) were computed as the number of annotated certain breaths divided by the length of calm periods after removing annotated distorted periods. Results Reviewers showed good interrater agreement on continuous RR {standard error of measurement (SEM) [4.8 (95%CI 4.4–5.3)]} and substantial agreement on classification of fast breathing (Fleiss kappa, κ 0.71). Agreement was lowest in the youngest age group [< 2 months: SEM 6.2 (5.4–7.4) bpm, κ 0.48; 2–11 months: 4.7 (4.0–5.8) bpm, κ 0.84; 12–59 months: 2.6 (2.2–3.1) bpm, κ 0.8]. Reviewers found the functionalities of the tool helpful in annotating breaths, but remained uncertain about the validity of their annotations. Conclusions Before the new tool can be considered a reference standard for RR assessments, interrater agreement in children younger than 2 months must be improved.

BACKGROUND: To prevent malaria among children aged 3-59 months in areas with high seasonal transmission, seasonal malaria chemoprevention (SMC) is recommended. In Chad, there is evidence of SMC administration to children aged older than 5 years (referred to as "leakage"). This study aimed to understand the reasons for leakage and explore the feasibility and acceptability of extending the delivery of SMC to children aged 5-10 years in Chad. METHODS: We conducted a mixed-methods study in Massaguet health district with a cross-sectional survey to determine SMC coverage for children aged up to 10 years after SMC cycles 1 and 3 (n=90 and n=100 caregivers surveyed, respectively) and at the end of cycle 4 (n=101 caregivers surveyed). We conducted 14 key informant interviews at the national and district level and 8 focus group discussions with community distributors and caregivers. RESULTS: In the compounds surveyed, there were no children aged 5-10 years in cycle 1. In cycles 3 (n=1 children) and 4 (n=16 children), there was 100% (95% confidence interval [CI]=2.5, 100.0) and 62.5% (95% CI=35.4, 84.8) coverage of SMC in children aged 5-10 years, respectively. Extension of SMC to older children was considered acceptable, but there were concerns about feasibility and ensuring the sustainability of the current program in children aged 3-59 months. Key informants acknowledged the need to secure additional funding to pilot SMC in older age groups and were uncertain about the impact of the current SMC program at scale. CONCLUSION: Key informants considered extending SMC to children aged 5-10 years acceptable but did not deem it a current priority. They expressed an urgent need to address leakage and reinforce both the sustainability and quality of the current SMC program.

We study the properties of the galaxies hosting the first 19 tidal disruption events (TDEs) detected with the Zwicky Transient Facility (ZTF) within the context of a carefully constructed, representative host galaxy sample. We find that the ZTF sample of TDE hosts is dominated by compact "green valley" galaxies. After we restrict the comparison sample to galaxies with a similar concentration, as measured by the Sérsic index, we find this green valley overrepresentation is even larger. That is, concentrated red sequence galaxies are not producing TDEs at elevated levels. We present host galaxy spectra that show that E + A galaxies are overrepresented in the ZTF sample by a factor of ≈22, which is lower than previous TDE host galaxy studies have found. We find that this overrepresentation can be fully accounted for when taking into account the masses, colors, and Sérsic indices of the ZTF TDE hosts. The combination of both green colors and high Sérsic index of the typical TDE host galaxy could be explained if the TDE rate is temporarily enhanced following a merger that leads to a higher central concentration of stars.

While tidal disruption events (TDEs) have long been heralded as laboratories for the study of quiescent black holes, the small number of known TDEs and uncertainties in their emission mechanism have hindered progress towards this promise. Here present 17 new TDEs that have been detected recently by the Zwicky Transient Facility along with Swift UV and X-ray follow-up observations. Our homogeneous analysis of the optical/UV light curves, including 22 previously known TDEs from the literature, reveals a clean separation of light curve properties with spectroscopic class. The TDEs with Bowen fluorescence features in their optical spectra have smaller blackbody radii, as well as longer rise times and higher disruption rates compared to the rest of the sample. The Bowen fluorescence mechanism requires a high density which can be reached at smaller radii, which in turn yields longer diffusion timescales. Thus, the difference in rise times suggests the pre-peak TDE light curves are governed not by the fallback timescale, but instead by the diffusion of photons through the tidal debris. The small subset of TDEs that show only helium emission lines in their spectra have the longest rise times, the highest luminosities and the lowest rates. We also report, for the first time, the detection of soft X-ray flares from a TDE on day timescales. Based on the fact the flares peak at a luminosity similar to the optical/UV blackbody luminosity, we attribute them to brief glimpses through a reprocessing layer that otherwise obscures the inner accretion flow., 30 pages, 18 figures, 8 tables, to be submitted to ApJ, comments welcome

Aim Pneumonia is the leading infectious cause of death among children under five globally. Many pneumonia deaths result from inappropriate treatment due to misdiagnosis of signs and symptoms. This study aims to identify whether health extension workers (HEWs) in Ethiopia, using an automated multimodal device (Masimo Rad‐G), adhere to required guidelines while assessing and classifying under five children with cough or difficulty breathing and to understand device acceptability. Methods A cross‐sectional study was conducted in three districts of Southern Nations, Nationalities, and Peoples' Region, Ethiopia. Between September and December 2018, 133 HEWs were directly observed using Rad‐G while conducting 599 sick child consultations. Usability was measured as adherence to the World Health Organization requirements to assess fast breathing and device manufacturer instructions for use. Acceptability was assessed using semi‐structured interviews with HEWs, first‐level health facility workers and caregivers. Results Adherence using the Rad‐G routinely for 2 months was 85.3% (95% CI 80.2, 89.3). Health workers and caregivers stated a preference for Rad‐G. Users highlighted a number of device design issues. Conclusion While demonstrating high levels of acceptability and usability, the device modifications to consider include better probe fit, improved user interface with exclusive age categories and simplified classification outcomes.

We present the discovery of a luminous X-ray transient, serendipitously detected by Swift's X-ray Telescope (XRT) on 2020 February 5, located in the nucleus of the galaxy SDSS J143359.16+400636.0 at z=0.099 (luminosity distance $D_{\rm L}=456$ Mpc). The transient was observed to reach a peak luminosity of $\sim10^{44}$ erg s$^{-1}$ in the 0.3--10 keV X-ray band, which was $\sim20$ times more than the peak optical/UV luminosity. Optical, UV, and X-ray lightcurves from the Zwicky Transient Facility (ZTF) and Swift show a decline in flux from the source consistent with $t^{-5/3}$, and observations with NuSTAR and Chandra show a soft X-ray spectrum with photon index $\Gamma=2.9\pm0.1$. The X-ray/UV properties are inconsistent with well known AGN properties and have more in common with known X-ray tidal disruption events (TDE), leading us to conclude that it was likely a TDE. The broadband spectral energy distribution (SED) can be described well by a disk blackbody model with an inner disk temperature of $7.3^{+0.3}_{-0.8}\times10^{5}$ K, with a large fraction ($>40$%) of the disk emission up-scattered into the X-ray band. An optical spectrum taken with Keck/LRIS after the X-ray detection reveals LINER line ratios in the host galaxy, suggesting low-level accretion on to the supermassive black hole prior to the event, but no broad lines or other indications of a TDE were seen. The stellar velocity dispersion implies the mass of the supermassive black hole powering the event is log($M_{\rm BH}$/$M_{\odot}$)$=7.41\pm0.41$, and we estimate that at peak the Eddington fraction of this event was $\sim$50%. This likely TDE was not identified by wide-field optical surveys, nor optical spectroscopy, indicating that more events like this would be missed without wide-field UV or X-ray surveys., Comment: Accepted for publication by ApJ. Accepted version now replaces initial submission

The Zwicky Transient Facility (ZTF) has discovered five new events belonging to an emerging class of AGN undergoing smooth flares with large amplitudes and rapid rise times. This sample consists of several transients that were initially classified as supernovae with narrow spectral lines. However, upon closer inspection, all of the host galaxies display resolved Balmer lines characteristic of a narrow-line Seyfert 1 (NLSy1) galaxy. The transient events are long-lived, over 400 days on average. We report UV and X-ray follow-up of the flares and observe persistent UV-bright emission, with two of the five transients detected with luminous X-ray emission, ruling out a supernova interpretation. We compare the properties of this sample to previously reported flaring NLSy1 galaxies, and find that they fall into three spectroscopic categories: Transients with 1) Balmer line profiles and Fe II complexes typical of NLSy1s, 2) strong He II profiles, and 3) He II profiles including Bowen fluorescence features. The latter are members of the growing class of AGN flares attributed to enhanced accretion reported by Trakhtenbrot et al. (2019). We consider physical interpretations in the context of related transients from the literature. For example, two of the sources show high amplitude rebrightening in the optical, ruling out a simple tidal disruption event scenario for those transients. We conclude that three of the sample belong to the Trakhtenbrot et al. (2019) class, and two are TDEs in NLSy1s. We also aim to understand why NLSy1s are preferentially the sites of such rapid enhanced flaring activity., Submitted to ApJ, 27 pages, 11 figures

We present X-ray and radio observations of the Fast Blue Optical Transient (FBOT) CRTS-CSS161010 J045834-081803 (CSS161010 hereafter) at t=69-531 days. CSS161010 shows luminous X-ray ($L_x\sim5\times 10^{39}\,\rm{erg\,s^{-1}}$) and radio ($L_{\nu}\sim10^{29}\,\rm{erg\,s^{-1}Hz^{-1}}$) emission. The radio emission peaked at ~100 days post transient explosion and rapidly decayed. We interpret these observations in the context of synchrotron emission from an expanding blastwave. CSS161010 launched a mildly relativistic outflow with velocity $\Gamma\beta c\ge0.55c$ at ~100 days. This is faster than the non-relativistic AT2018cow ($\Gamma\beta c\sim0.1c$) and closer to ZTF18abvkwla ($\Gamma\beta c\ge0.3c$ at 63 days). The inferred initial kinetic energy of CSS161010 ($E_k\gtrsim10^{51}$ erg) is comparable to that of long Gamma Ray Bursts (GRBs), but the ejecta mass that is coupled to the mildly relativistic outflow is significantly larger ($\sim0.01-0.1\,\rm{M_{\odot}}$). This is consistent with the lack of observed gamma-rays. The luminous X-rays were produced by a different emission component to the synchrotron radio emission. CSS161010 is located at ~150 Mpc in a dwarf galaxy with stellar mass $M_{*}\sim10^{7}\,\rm{M_{\odot}}$ and specific star formation rate $sSFR\sim 0.3\,\rm{Gyr^{-1}}$. This mass is among the lowest inferred for host-galaxies of explosive transients from massive stars. Our observations of CSS161010 are consistent with an engine-driven aspherical explosion from a rare evolutionary path of a H-rich stellar progenitor, but we cannot rule out a stellar tidal disruption event on a centrally-located intermediate mass black hole. Regardless of the physical mechanism, CSS161010 establishes the existence of a new class of rare (rate $, Comment: Accepted to ApJL