Characterization of a Maximum Likelihood Gamma-Ray Reconstruction Algorithm for VERITAS

We characterize the improved angular and energy resolution of a new likelihood gamma-ray reconstruction for VERITAS. The algorithm uses the average photoelectrons stored in templates that are based on simulations of large numbers of showers as a function of 5 gamma-ray parameters: energy, zenith angle, core location (x,y), and depth of first interaction in the atmosphere. Comparing the template predictions of the average photoelectrons in each pixel to observed photoelectrons allows us to calculate the likelihood. By maximizing the likelihood, we find the optimal gamma-ray parameters. The maximum likelihood reconstruction improves on the standard VERITAS analysis which relies on: 1. the weighted average of the axis of elongation in the images to determine the gamma-ray direction and 2. look-up tables that relate the observed energy deposition of Cherenkov photons to the true gamma-ray energy. Not only is the maximum likelihood method more accurate, but it is also not biased by missing pixel information due to the edge of the camera or pixel cleaning. The drawback is that it takes more CPU time (80 ms/event).Comment: 8 pages, 7 figures, In Proceedings of the 35th International Cosmic Ray Conference (ICRC 2017), Busan (South Korea

Temporal and Spectral Analysis of 1ES 2344+514 in Two Flaring States Observed by VERITAS

VERITAS observed the bright blazar 1ES 2344+514 during two flaring periods, one from Dec. 17 to Dec. 18, 2015 (MJD 57373-57374) with a peak flux of ~60% of the Crab and another from Nov. 28 to Dec. 3, 2021 (MJD 59546-59551) with a peak flux of ~20% of the Crab. This blazar, located at a redshift of z = 0.044, is classified as an extreme high-frequency-peaked BL Lacertae object (HBL). It is known to be variable, including several previous day-scale flares: Whipple on Dec. 20, 1995, VERITAS on Dec. 7, 2007, and MAGIC on Aug. 11, 2016. The VERITAS near-nightly monitoring of 1ES 2344+514 during the 2015-2016 and 2021-2022 seasons provides good coverage of the pre- and post-flare flux as well as the rise/fall time of the flares. We present the multiwavelength light curves of each flare as well as the very high-energy spectra in the two flare states and the two pre-flare states.Comment: 9 pages, 4 figures, International Cosmic Ray Conference, Nagoya, Japa

Computing Accurate Age and Distance Factors in Cosmology

As the universe expands astronomical observables such as brightness and angular size on the sky change in ways that differ from our simple Cartesian expectation. We show how observed quantities depend on the expansion of space and demonstrate how to calculate such quantities using the Friedmann equations. The general solution to the Friedmann equations requires a numerical solution which is easily coded in any computing language (including EXCEL). We use these numerical calculations in four student projects that help to build their understanding of high-redshift phenomena and cosmology. Instructions for these projects are available as supplementary materials

An Examination of the Structured Assessment of Protective Factors for Violence Risk – Youth Version (SAPROF-YV) in Canadian Adolescents

The Structured Assessment of Protective Factors for Violence Risk – Youth Version (SAPROF-YV; de Vries Robbé et al., 2015) is a new measure of protective factors that is used with a risk-focused tool, such as the Structured Assessment of Violence Risk in Youth (SAVRY; Borum et al., 2006), to provide a more balanced and comprehensive assessment of violence risk in adolescents. Currently, there are no published studies on the SAPROF-YV’s predictive validity. The present study investigated the relationship between the SAPROF-YV and aggression in a sample of 69 adolescents. Using a retrospective follow-up study design, files were reviewed at an inpatient treatment center and a probation office. Results indicated that the SAPROF-YV demonstrated good convergent and discriminant validity with the SAVRY. The SAPROF-YV was predictive of the absence of minor verbal aggression. While the SAPROF-YV added incremental predictive validity to SAVRY Protective factors for minor verbal aggression, it did not add incrementally to SAVRY Risk factors in the prediction of any type of aggression. Implications for future research and clinical applications are discussed

Predictive Validity of the Structured Assessment of Violence Risk in Youth (SAVRY) among a Sample of Asian Canadian Youth on Probation

Objective: Although past studies suggest that the Structured Assessment of Violence Risk in Youth (SAVRY; Borum et al., 2006) has moderate predictive validity, its predictive validity with Asian youth in Western countries is unknown. We therefore compared the SAVRY’s predictive validity in a sample of Asian Canadian versus White Canadian youth. Hypotheses: Given that the SAVRY is normed on samples comprising mostly youth who are White, we expected its predictive validity for recidivism would be lower for Asian Canadians than White Canadians. Method: We examined youth probation officers’ SAVRY assessments for 573 youth (445 White Canadians, 56 East/Southeast Asian Canadians, and 72 South Asian Canadians) on community supervision (i.e., probation) in a Canadian province. Youth were prospectively followed for an average of 1.97 years (SD = 0.56 years) to determine if they were subsequently charged with violent or non-violent offenses. Results: Asian Canadians scored significantly lower on Risk Total scores compared to White Canadians. Predictive validity for violent and non-violent recidivism fell in the medium to large range for East/Southeast Asian Canadians (AUCs = .69 to .89) and South Asian Canadians (AUCs = .64 to .83). In comparison, predictive validity for White Canadians was generally lower (AUCs = .63 to .77; small to large range). Risk Total scores and non-violent risk ratings significantly predicted non-violent recidivism better for East/Southeast Asian Canadians (AUCs = .89 and .87, respectively) than White Canadians (AUCs = .77 and .71, respectively). Despite few significant differences between Asian subgroups, predictive validity for non-violent risk ratings was significantly higher in East/Southeast Asian Canadians (AUC = .87) than South Asian Canadians (AUC = .64). Conclusions: The SAVRY may be a useful tool for predicting recidivism with Asian Canadians. However, future research should examine the SAVRY’s predictive validity for youth of Asian descent in different countries and contexts

Community-Acquired Pneumonia Due to Pandemic A(H1N1)2009 Influenzavirus and Methicillin Resistant Staphylococcus aureus Co-Infection

BACKGROUND: Bacterial pneumonia is a well described complication of influenza. In recent years, community-onset methicillin-resistant Staphylococcus aureus (cMRSA) infection has emerged as a contributor to morbidity and mortality in patients with influenza. Since the emergence and rapid dissemination of pandemic A(H1N1)2009 influenzavirus in April 2009, initial descriptions of the clinical features of patients hospitalized with pneumonia have contained few details of patients with bacterial co-infection. METHODOLOGY/PRINCIPAL FINDINGS: Patients with community-acquired pneumonia (CAP) caused by co-infection with pandemic A(H1N1)2009 influenzavirus and cMRSA were prospectively identified at two tertiary hospitals in one Australian city during July to September 2009, the period of intense influenza activity in our region. Detailed characterization of the cMRSA isolates was performed. 252 patients with pandemic A(H1N1)2009 influenzavirus infection were admitted at the two sites during the period of study. Three cases of CAP due to pandemic A(H1N1)2009/cMRSA co-infection were identified. The clinical features of these patients were typical of those with S. aureus co-infection or sequential infection following influenza. The 3 patients received appropriate empiric therapy for influenza, but inappropriate empiric therapy for cMRSA infection; all 3 survived. In addition, 2 fatal cases of CAP caused by pandemic A(H1N1)2009/cMRSA co-infection were identified on post-mortem examination. The cMRSA infections were caused by three different cMRSA clones, only one of which contained genes for Panton-Valentine Leukocidin (PVL). CONCLUSIONS/SIGNIFICANCE: Clinicians managing patients with pandemic A(H1N1)2009 influenzavirus infection should be alert to the possibility of co-infection or sequential infection with virulent, antimicrobial-resistant bacterial pathogens such as cMRSA. PVL toxin is not necessary for the development of cMRSA pneumonia in the setting of pandemic A( H1N1) 2009 influenzavirus co-infection

VERITAS discovery of very high energy gamma-ray emission from S3 1227+25 and multiwavelength observations

We report the detection of very high energy gamma-ray emission from the blazar S3 1227+25 (VER J1230+253) with the Very Energetic Radiation Imaging Telescope Array System (VERITAS). VERITAS observations of the source were triggered by the detection of a hard-spectrum GeV flare on May 15, 2015 with the Fermi-Large Area Telescope (LAT). A combined five-hour VERITAS exposure on May 16th and May 18th resulted in a strong 13$\sigma$ detection with a differential photon spectral index, $\Gamma$ = 3.8 $\pm$ 0.4, and a flux level at 9% of the Crab Nebula above 120 GeV. This also triggered target of opportunity observations with Swift, optical photometry, polarimetry and radio measurements, also presented in this work, in addition to the VERITAS and Fermi-LAT data. A temporal analysis of the gamma-ray flux during this period finds evidence of a shortest variability timescale of $\tau_{obs}$ = 6.2 $\pm$ 0.9 hours, indicating emission from compact regions within the jet, and the combined gamma-ray spectrum shows no strong evidence of a spectral cut-off. An investigation into correlations between the multiwavelength observations found evidence of optical and gamma-ray correlations, suggesting a single-zone model of emission. Finally, the multiwavelength spectral energy distribution is well described by a simple one-zone leptonic synchrotron self-Compton radiation model.Comment: 18 pages, 6 figures. Accepted for publication in the Astrophysical Journal (ApJ

Search for Cosmic Strings in the GOODS Survey

We search Hubble Space Telescope Treasury Program images collected as part of the Great Observatories Origins Deep Survey for pairs of galaxies consistent with the gravitational lensing signature of a cosmic string. Our technique includes estimates of the efficiency for finding the lensed galaxy pair. In the north (south) survey field we find no evidence out to a redshift of greater than 0.5 (0.3) for cosmic strings to a mass per unit length limit of Gμ/c2 \u3c 3.0 × 10−7 at 95% confidence limits (C.L.). In the combined 314.9 arcmin2 of the north and south survey fields this corresponds to a global limit on Ωstrings \u3c 0.02. Our limit on Gμ/c2 is more than an order of magnitude lower than searches for individual strings in cosmic microwave background (CMB) data. Our limit is higher than other CMB and gravitational wave searches, however, we note that it is less model dependent than these other searches

Search for Cosmic Strings in the COSMOS Survey

We search the COSMOS survey for pairs of galaxies consistent with the gravitational lensing signature of a cosmic string. The COSMOS survey imaged 1.64 square degrees using the Advanced Camera for Surveys (ACS) aboard the Hubble Space Telescope (HST). Our technique includes estimates of the efficiency for finding the lensed galaxy pair. We find no evidence for cosmic strings with a mass per unit length of Gμ/c2 \u3c 3.0 × 10−7 out to redshifts greater than 0.6 and set 95% upper limits. This corresponds to a global 95% upper limit of Ωstrings \u3c 0.0028