An Injection System for the CHIME/FRB Experiment

Dedicated surveys searching for Fast Radio Bursts (FRBs) are subject to selection effects which bias the observed population of events. Software injection systems are one method of correcting for these biases by injecting a mock population of synthetic FRBs directly into the realtime search pipeline. The injected population may then be used to map intrinsic burst properties onto an expected signal-to-noise ratio (SNR), so long as telescope characteristics such as the beam model and calibration factors are properly accounted for. This paper presents an injection system developed for the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst project (CHIME/FRB). The system was tested to ensure high detection efficiency, and the pulse calibration method was verified. Using an injection population of ~85,000 synthetic FRBs, we found that the correlation between fluence and SNR for injected FRBs was consistent with that of CHIME/FRB detections in the first CHIME/FRB catalog. We also noted that the sensitivity of the telescope varied strongly as a function of the broadened burst width, but not as a function of the dispersion measure. We conclude that some of the machine-learning based Radio Frequency Interference (RFI) mitigation methods used by CHIME/FRB can be re-trained using injection data to increase sensitivity to wide events, and that planned upgrades to the presented injection system will allow for determining a more accurate CHIME/FRB selection function in the near future.Comment: 13 pages, 8 figures. Submitted to A

A Distant Fast Radio Burst Associated with Its Host Galaxy by the Very Large Array

We present the discovery and subarcsecond localization of a new fast radio burst (FRB) by the Karl G. Jansky Very Large Array (VLA) and realfast search system. The FRB was discovered on 2019 June 14 with a dispersion measure of 959 pc cm⁻³. This is the highest DM of any localized FRB and its measured burst fluence of 0.6 Jy ms is less than nearly all other FRBs. The source is not detected to repeat in 15 hr of VLA observing and 153 hr of CHIME/FRB observing. We describe a suite of statistical and data quality tests we used to verify the significance of the event and its localization precision. Follow-up optical/infrared photometry with Keck and Gemini associate the FRB with a pair of galaxies with r ∼ 23 mag. The false-alarm rate for radio transients of this significance that are associated with a host galaxy is roughly 3×10⁻⁴ hr⁻¹. The two putative host galaxies have similar photometric redshifts of z_(phot) ∼ 0.6, but different colors and stellar masses. Comparing the host distance to that implied by the dispersion measure suggests a modest (~ 50 pc/cm⁻³) electron column density associated with the FRB environment or host galaxy/galaxies

Comprehensive Bayesian analysis of FRB-like bursts from SGR 1935+2154 observed by CHIME/FRB

The bright millisecond-duration radio burst from the Galactic magnetar SGR 1935+2154 in 2020 April was a landmark event, demonstrating that at least some fast radio burst (FRB) sources could be magnetars. The two-component burst was temporally coincident with peaks observed within a contemporaneous short X-ray burst envelope, marking the first instance where FRB-like bursts were observed to coincide with X-ray counterparts. In this study, we detail five new radio burst detections from SGR 1935+2154, observed by the CHIME/FRB instrument between October 2020 and December 2022. We develop a fast and efficient Bayesian inference pipeline that incorporates state-of-the-art Markov chain Monte Carlo techniques and use it to model the intensity data of these bursts under a flexible burst model. We revisit the 2020 April burst and corroborate that both the radio sub-components lead the corresponding peaks in their high-energy counterparts. For a burst observed in 2022 October, we find that our estimated radio pulse arrival time is contemporaneous with a short X-ray burst detected by GECAM and HEBS, and Konus-Wind and is consistent with the arrival time of a radio burst detected by GBT. We present flux and fluence estimates for all five bursts, employing an improved estimator for bursts detected in the side-lobes. We also present upper limits on radio emission for X-ray emission sources which were within CHIME/FRB's field-of-view at trigger time. Finally, we present our exposure and sensitivity analysis and estimate the Poisson rate for FRB-like events from SGR 1935+2154 to be $0.005^{+0.082}_{-0.004}$ events/day above a fluence of $10~\mathrm{kJy~ms}$ during the interval from 28 August 2018 to 1 December 2022, although we note this was measured during a time of great X-ray activity from the source.Comment: 22 pages, 6 figures, 4 tables. To be submitted to Ap

CHIME Discovery of a Binary Pulsar with a Massive Non-Degenerate Companion

Of the more than 3000 radio pulsars currently known, only ∼300 are in binary systems, and only five of these consist of young pulsars with massive nondegenerate companions. We present the discovery and initial timing, accomplished using the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope, of the sixth such binary pulsar, PSR J2108+4516, a 0.577 s radio pulsar in a 269 day orbit of eccentricity 0.09 with a companion of minimum mass 11 M⊙. Notably, the pulsar undergoes periods of substantial eclipse, disappearing from the CHIME 400–800 MHz observing band for a large fraction of its orbit, and displays significant dispersion measure and scattering variations throughout its orbit, pointing to the possibility of a circumstellar disk or very dense stellar wind associated with the companion star. Subarcsecond resolution imaging with the Karl G. Jansky Very Large Array unambiguously demonstrates that the companion is a bright, V ≃ 11 OBe star, EM* UHA 138, located at a distance of 3.26(14) kpc. Archival optical observations of EM* UHA 138 approximately suggest a companion mass ranging from 17.5 M⊙ < Mc < 23 M⊙, in turn constraining the orbital inclination angle to 50fdg3 ≲ i ≲ 58fdg3. With further multiwavelength follow-up, PSR J2108+4516 promises to serve as another rare laboratory for the exploration of companion winds, circumstellar disks, and short-term evolution through extended-body orbital dynamics

Children’s moderate-to-vigorous physical activity on weekdays versus weekend days:A multi-country analysis

PURPOSE: The Structured Days Hypothesis (SDH) posits that children's behaviors associated with obesity - such as physical activity - are more favorable on days that contain more 'structure' (i.e., a pre-planned, segmented, and adult-supervised environment) such as school weekdays, compared to days with less structure, such as weekend days. The purpose of this study was to compare children's moderate-to-vigorous physical activity (MVPA) levels on weekdays versus weekend days using a large, multi-country, accelerometer-measured physical activity dataset. METHODS: Data were received from the International Children's Accelerometer Database (ICAD) July 2019. The ICAD inclusion criteria for a valid day of wear, only non-intervention data (e.g., baseline intervention data), children with at least 1 weekday and 1 weekend day, and ICAD studies with data collected exclusively during school months, were included for analyses. Mixed effects models accounting for the nested nature of the data (i.e., days within children) assessed MVPA minutes per day (min/day MVPA) differences between weekdays and weekend days by region/country, adjusted for age, sex, and total wear time. Separate meta-analytical models explored differences by age and country/region for sex and child weight-status. RESULTS/FINDINGS: Valid data from 15 studies representing 5794 children (61% female, 10.7 ± 2.1 yrs., 24% with overweight/obesity) and 35,263 days of valid accelerometer data from 5 distinct countries/regions were used. Boys and girls accumulated 12.6 min/day (95% CI: 9.0, 16.2) and 9.4 min/day (95% CI: 7.2, 11.6) more MVPA on weekdays versus weekend days, respectively. Children from mainland Europe had the largest differences (17.1 min/day more MVPA on weekdays versus weekend days, 95% CI: 15.3, 19.0) compared to the other countries/regions. Children who were classified as overweight/obese or normal weight/underweight accumulated 9.5 min/day (95% CI: 6.9, 12.2) and 10.9 min/day (95% CI: 8.3, 13.5) of additional MVPA on weekdays versus weekend days, respectively. CONCLUSIONS: Children from multiple countries/regions accumulated significantly more MVPA on weekdays versus weekend days during school months. This finding aligns with the SDH and warrants future intervention studies to prioritize less-structured days, such as weekend days, and to consider providing opportunities for all children to access additional opportunities to be active

Size and Shape Constraints of (486958) Arrokoth from Stellar Occultations

We present the results from four stellar occultations by (486958) Arrokoth, the flyby target of the New Horizons extended mission. Three of the four efforts led to positive detections of the body, and all constrained the presence of rings and other debris, finding none. Twenty-five mobile stations were deployed for 2017 June 3 and augmented by fixed telescopes. There were no positive detections from this effort. The event on 2017 July 10 was observed by the Stratospheric Observatory for Infrared Astronomy with one very short chord. Twenty-four deployed stations on 2017 July 17 resulted in five chords that clearly showed a complicated shape consistent with a contact binary with rough dimensions of 20 by 30 km for the overall outline. A visible albedo of 10% was derived from these data. Twenty-two systems were deployed for the fourth event on 2018 August 4 and resulted in two chords. The combination of the occultation data and the flyby results provides a significant refinement of the rotation period, now estimated to be 15.9380 ± 0.0005 hr. The occultation data also provided high-precision astrometric constraints on the position of the object that were crucial for supporting the navigation for the New Horizons flyby. This work demonstrates an effective method for obtaining detailed size and shape information and probing for rings and dust on distant Kuiper Belt objects as well as being an important source of positional data that can aid in spacecraft navigation that is particularly useful for small and distant bodies.Fil: Buie, Marc W.. Southwest Research Institute.; Estados UnidosFil: Porter, Simon B.. Southwest Research Institute.; Estados UnidosFil: Tamblyn, Peter. Southwest Research Institute.; Estados UnidosFil: Terrell, Dirk. Southwest Research Institute.; Estados UnidosFil: Parker, Alex Harrison. Southwest Research Institute.; Estados UnidosFil: Baratoux, David. Géosciences Environnement Toulouse; Francia. Centre National de la Recherche Scientifique; FranciaFil: Kaire, Maram. Ministry of Higher Education Research and Innovation; Senegal. Asociación Senegalesa para la Promoción de la Astronomía; SenegalFil: Leiva, Rodrigo. Southwest Research Institute.; Estados UnidosFil: Verbiscer, Anne J.. University of Virginia; Estados UnidosFil: Zangari, Amanda M.. Southwest Research Institute.; Estados UnidosFil: Colas, François. Centre National de la Recherche Scientifique. Observatoire de Paris; Francia. Sorbonne University; Francia. Centre National de la Recherche Scientifique; FranciaFil: Diop, Baidy Demba. Direction de la Formation et de la Communication; SenegalFil: Samaniego, Joseph I.. University of Colorado; Estados UnidosFil: Wasserman, Lawrence H.. Lowell Observatory; Estados UnidosFil: Benecchi, Susan D.. Planetary Science Institute; Estados UnidosFil: Caspi, Amir. Southwest Research Institute.; Estados UnidosFil: Gwyn, Stephen. Herzberg Astronomy and Astrophysics Research Centre; CanadáFil: Kavelaars, J. J.. Herzberg Astronomy and Astrophysics Research Centre; CanadáFil: Ocampo Uría, Adriana C.. National Aeronautics and Space Administration; Estados UnidosFil: Rabassa, Jorge Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Skrutskie, M. F.. University of Virginia; Estados UnidosFil: Soto, Alejandro. Southwest Research Institute.; Estados UnidosFil: Tanga, Paolo. Université Côte d’Azur; Francia. Centre National de la Recherche Scientifique; FranciaFil: Young, Eliot F.. Southwest Research Institute.; Estados UnidosFil: Stern, S. Alan. Southwest Research Institute.; Estados UnidosFil: Andersen, Bridget C.. University of Virginia; Estados UnidosFil: Arango Pérez, Mauricio E.. Universidad de Antioquia; ColombiaFil: Arredondo, Anicia. Massachusetts Institute of Technology; Estados UnidosFil: Artola, Rodolfo Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: García Migani, Esteban Andrés. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Geofísica y Astronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; Argentin

Understanding adolescent and young adult use of family physician services: a cross-sectional analysis of the Canadian Community Health Survey

BACKGROUND: Primary health care is known to have positive effects on population health and may reduce at-risk behavior and health problems in adolescence. Yet little is known about the factors that are associated with adolescent and young adult utilization of family physician services. It is critical to determine the factors associated with utilization to inform effective primary health care policy. We address this gap in the primary health care literature by examining three issues concerning adolescent and young adult family physician use: inequity; the unique developmental stage of adolescence; and the distinction between utilization (users versus non-users) and intensity (high users versus low users). METHODS: We conducted nested logistic regressions for two outcomes: utilization and intensity of family physician services for early adolescence, middle adolescence, and young adulthood using the 2005 Canadian Community Health Survey. RESULTS: Chronic conditions were associated with utilization in early and middle adolescence and intensity in all age groups. Respondents from Quebec had lower odds of utilization. Those without a regular medical doctor had much lower odds of being users. The factors associated with use in early and middle adolescence were in keeping with parental involvement while the factors in young adulthood show the emerging independence of this group. CONCLUSIONS: We highlight key messages not known previously for adolescent and young adult use of family physician services. There is inequity concerning regional variation and for those who do not have a regular medical doctor. There is variation in factors associated with family physician services across the three age groups of adolescence. Health care and health care policies aimed at younger adolescents must consider that parents are still the primary decision-maker while older adolescents are more autonomous. There is variation in the factors associated with the two outcomes of utilization and intensity of services. Factors associated with utilization must be understood when considering the equitability of access to primary health care while factors associated with intensity must be understood when considering appropriate use of resources. The understanding gained from this study can inform health care policy that is responsive to the critical developmental stage of adolescence and young adulthood

Sub-second periodicity in a fast radio burst

Fast radio bursts (FRBs) are millisecond-duration flashes of radio waves that are visible at distances of billions of light-years. The nature of their progenitors and their emission mechanism remain open astrophysical questions. Here we report the detection of the multi-component FRB 20191221A and the identification of a periodic separation of 216.8(1) ms between its components with a significance of 6.5 sigmas. The long (~3 s) duration and nine or more components forming the pulse profile make this source an outlier in the FRB population. Such short periodicity provides strong evidence for a neutron-star origin of the event. Moreover, our detection favours emission arising from the neutron-star magnetosphere, as opposed to emission regions located further away from the star, as predicted by some models.Comment: Updated to conform to the accepted versio

A Distant Fast Radio Burst Associated with Its Host Galaxy by the Very Large Array

We present the discovery and subarcsecond localization of a new fast radio burst (FRB) by the Karl G. Jansky Very Large Array (VLA) and realfast search system. The FRB was discovered on 2019 June 14 with a dispersion measure of 959 pc cm⁻³. This is the highest DM of any localized FRB and its measured burst fluence of 0.6 Jy ms is less than nearly all other FRBs. The source is not detected to repeat in 15 hr of VLA observing and 153 hr of CHIME/FRB observing. We describe a suite of statistical and data quality tests we used to verify the significance of the event and its localization precision. Follow-up optical/infrared photometry with Keck and Gemini associate the FRB with a pair of galaxies with r ∼ 23 mag. The false-alarm rate for radio transients of this significance that are associated with a host galaxy is roughly 3×10⁻⁴ hr⁻¹. The two putative host galaxies have similar photometric redshifts of z_(phot) ∼ 0.6, but different colors and stellar masses. Comparing the host distance to that implied by the dispersion measure suggests a modest (~ 50 pc/cm⁻³) electron column density associated with the FRB environment or host galaxy/galaxies