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We present a comprehensive study of 29 short gamma-ray bursts (SGRBs) observed ≈0.8−60 days postburst using Chandra and XMM-Newton. We provide the inferred distributions of the SGRB jet opening angles and true event rates to compare against neutron star merger rates. We perform a uniform analysis and modeling of their afterglows, obtaining 10 opening angle measurements and 19 lower limits. We report on two new opening angle measurements (SGRBs 050724A and 200411A) and eight updated values, obtaining a median value of 〈θ_j〉 ≈ 6.°1 [−3.°2, +9.°3] (68% confidence on the full distribution) from jet measurements alone. For the remaining events, we inferθ_j≳ 0.°5–26°. We uncover a population of SGRBs with wider jets ofθ_j≳ 10° (including two measurements ofθ_j≳ 15°), representing ∼28% of our sample. Coupled with multiwavelength afterglow information, we derive a total true energy of 〈E_true,tot〉 ≈ 10⁴⁹–10⁵⁰erg, which is consistent with magnetohydrodynamic jet launching mechanisms. Furthermore, we determine a range for the beaming-corrected event rate of${\mathfrak{R}}_{\mathrm{true}}\approx 360-1800$Gpc⁻³yr⁻¹, set by the inclusion of a population of wide jets on the low end, and the jet measurements alone on the high end. From a comparison with the latest merger rates, our results are consistent with the majority of SGRBs originating from binary neutron star mergers. However, our inferred rates are well above the latest neutron star–black hole merger rates, consistent with at most a small fraction of SGRBs originating from such mergers.

 

A tidal disruption event (TDE) occurs when a star is destroyed by a supermassive black hole. Broad-band radio spectral observations of TDEs trace the emission from any outflows or jets that are ejected from the vicinity of the supermassive black hole. However, radio detections of TDEs are rare, with <20 published to date, and only 11 with multi-epoch broad-band coverage. Here we present the radio detection of the TDE AT2020vwl and our subsequent radio monitoring campaign of the outflow that was produced, spanning 1.5 yr post-optical flare. We tracked the outflow evolution as it expanded between 1016 and 1017 cm from the supermassive black hole, deducing it was non-relativistic and launched quasi-simultaneously with the initial optical detection through modelling the evolving synchrotron spectra of the event. We deduce that the outflow is likely to have been launched by material ejected from stream-stream collisions (more likely), the unbound debris stream, or an accretion-induced wind or jet from the supermassive black hole (less likely). AT2020vwl joins a growing number of TDEs with well-characterized prompt radio emission, with future timely radio observations of TDEs required to fully understand the mechanism that produces this type of radio emission in TDEs.

 

Engineering education researchers and practitioners have driven instructional innovation in undergraduate engineering instruction. Much of the research about educational innovation has focused on undergraduate classrooms in large enrollment courses and/or research-intensive institutions. Propagation of innovations across settings, especially those quite unlike the original context, has received less attention in the literature. This includes liberal arts institutions, which collectively educate a large number of undergraduate engineering students in various contexts. Therefore, this study focuses on the implementation of an instructional innovation in a liberal arts institution that started a new engineering program to educate a regional engineering workforce. This qualitative study documented the experiences of one engineering instructor who adopted and adapted a blended learning environment for undergraduate dynamics designed to promote active and collaborative learning in undergraduate engineering courses. We analyzed interviews, documents, artifacts, visual materials, and field notes to examine the propagation of the instructional system in context with cultural features in local institution settings. Our findings show how an engineering instructor orchestrated a culture-aligned adoption and adaptation of an instructional innovation. Using reflective practice, the research participant adapted the implemented innovative instruction to their hands-on institution culture, such as adjusting expectations in content, adapting resources to students’ individual needs, adjusting uncertainty of problem solving, and adapting to a hands-on institution culture. This research highlights the important role of institutional culture in local adaptations of educational innovations, and it provides the community with an expanded way to think about innovation propagation. 

Abstract The advent of sensitive gravitational-wave (GW) detectors, coupled with wide-field, high-cadence optical time-domain surveys, raises the possibility of the first joint GW–electromagnetic detections of core-collapse supernovae (CCSNe). For targeted searches of GWs from CCSNe, optical observations can be used to increase the sensitivity of the search by restricting the relevant time interval, defined here as the GW search window (GSW). The extent of the GSW is a critical factor in determining the achievable false alarm probability for a triggered CCSN search. The ability to constrain the GSW from optical observations depends on how early a CCSN is detected, as well as the ability to model the early optical emission. Here we present several approaches to constrain the GSW, ranging in complexity from model-independent analytical fits of the early light curve, model-dependent fits of the rising or entire light curve, and a new data-driven approach using existing well-sampled CCSN light curves from Kepler and the Transiting Exoplanet Survey Satellite. We use these approaches to determine the time of core-collapse and its associated uncertainty (i.e., the GSW). We apply our methods to two Type II SNe that occurred during LIGO/Virgo Observing Run 3: SN 2019fcn and SN 2019ejj (both in the same galaxy at d = 15.7 Mpc). Our approach shortens the duration of the GSW and improves the robustness of the GSW compared to the techniques used in past GW CCSN searches. 

Abstract We present late-time radio/millimeter (as well as optical/UV and X-ray) detections of tidal disruption event (TDE) AT2018hyz, spanning 970–1300 d after optical discovery. In conjunction with earlier deeper limits, including those at ≈700 days, our observations reveal rapidly rising emission at 0.8–240 GHz, steeper than F ν ∝ t 5 relative to the time of optical discovery. Such a steep rise cannot be explained in any reasonable scenario of an outflow launched at the time of disruption (e.g., off-axis jet, sudden increase in the ambient density), and instead points to a delayed launch. Our multifrequency data allow us to directly determine the radius and energy of the radio-emitting outflow, and we find from our modeling that the outflow was launched ≈750 days after optical discovery. The outflow velocity is mildly relativistic, with β ≈ 0.25 and ≈0.6 for a spherical geometry and a 10° jet geometry, respectively, and the minimum kinetic energy is E K ≈ 5.8 × 10 49 and ≈6.3 × 10 49 erg, respectively. This is the first definitive evidence for the production of a delayed mildly relativistic outflow in a TDE; a comparison to the recently published radio light curve of ASASSN-15oi suggests that the final rebrightening observed in that event (at a single frequency and time) may be due to a similar outflow with a comparable velocity and energy. Finally, we note that the energy and velocity of the delayed outflow in AT2018hyz are intermediate between those of past nonrelativistic TDEs (e.g., ASASSN-14li, AT2019dsg) and the relativistic TDE Sw J1644+57. We suggest that such delayed outflows may be common in TDEs. 

Abstract—This research-to-practice full paper investigates the alignment of a specific pedagogical innovation, the Freeform pedagogical system, with the student culture(s) of the mechanical engineering department of a small private college (SPC) in the upper Midwest of the United States, we ask the research question: What are the defining characteristics of the student culture or (sub)cultures in the engineering department where the Freeform system is being propagated? Based upon interviews with on-campus stakeholders (students, faculty, and staff), we constructed a 64-item survey to characterize the culture of their engineering department. We analyzed student responses using the cultural consensus theory model (CCT), a quantitative method that looks for patterns of responses to cultural statements. Grouped together, these patterns of responses indicate the values of the sub-cultures present within a participant group. Our results indicate that the best fitting model contains two student subcultures: student subculture 1 (SC1) (n = 15) and student subculture 2 (SC2) (n = 60). These two subcultures exhibit differences across a handful of items that focus on the student experience and in particular the sense of connectedness or belonging among students. Members of SC1 seem to be disconnected from both their peers and their instructors, work primarily alone, and seem to struggle to obtain access to academic assistance. SC1 members also feel overworked with (what they perceive to be) low-value-added activities, and they do not perceive alignment between how instructors teach and how they prefer to learn. In contrast, members of SC2 seem to be aligned with the institutional mission, which focuses on faculty-student relationships and learning in the community 

ABSTRACT CONTEXT This paper examines an engineering dynamics course at Purdue University that was specifically designed to create an active, blended, and collaborative environment. In addition to in-person classes and support, students have access to blended content such as solution videos, mechanics visualizations, a course discussion forum, and interactive simulations. PURPOSE Many studies have shown that students’ engagement in an online discussion forum enhances their learning performance (Davies & Graff, 2005; Hrastinski, 2008). However, our previous research showed that students’ engagement in the online forum of our dynamics course differed significantly across students’ demographics. We showed that women, white, or Asian American students were more likely to be involved in online discussions than men, international, or Hispanic students (Duan et al., 2018). In this paper, we take the previous analysis further by examining whether the observed differences in online student engagement mediate or moderate student performance. APPROACH To answer our research question, we will first investigate the mediation effect by creating two models. A first model with race/international status as the mediating variable and gender identity as a control variable, and a second model with gender identity as the mediating variable and race/international status as a control. Second, we will investigate the moderation effect of demographic factors by creating a regression model including interaction terms to show the relationship of each demographic’s discussion forum engagement to overall performance. The goal of investigating these interaction terms is to determine if a moderating relationship exists where demographic factors impact online engagement, which in turn impact course performance. CONCLUSIONS We find that gender identity is the only significant demographic factor that moderates the effect of a student’s engagement on their performance. Based on the findings of our previous work, students of various racial and ethnic identities do engage differently in the discussion forum. However, this analysis was unable to detect any significant difference in student engagement based on demographics. Our paper contributes to understanding the mechanisms through which students’ engagement can translate into academic performance by focusing on their demographic background. The moderating role of students’ demographic background calls for a more targeted design of instructional tools in blended and collaborative environments to better support students from various demographic backgrounds. 

ABSTRACT CONTEXT Culture influences the dynamics and outcomes of organizations in profound ways, including individual-level outcomes (like the quality of work products) and collective impacts (such as reputation or influence). As such, understanding organizational culture is a crucial element of understanding performance; from an anthropological perspective, ‘performance’ is not an outcome of culture, it is a part of culture. A key challenge in understanding organizational culture, especially in complex academic organizations, is the lack of a flexible, scalable approach for data collection and analysis. PURPOSE OR GOAL In this study, we report on our development of a survey-based cultural characterization tool that leverages both lightweight data collection from stakeholders in the organization and public information about that organization. We also integrate perspectives from prior literature about faculty, students, and staff in academic departments. Taken together, the resulting survey covers key elements of culture and allows for scalable data collection across settings via customizations and embedded logic in the survey itself. The outcome of this work is a design process for a new and promising tool for scalable cultural characterization, and we have deployed this tool across two institutions. APPROACH OR METHODOLOGY/METHODS We leverage prior research, our own preliminary data collection, and our experience with this approach in a different setting to develop a cultural characterization survey suitable for delivery to multiple engineering department stakeholders (faculty, staff, and students). We start with a modest number of interviews, stratified by these three groups and achieving saturation of responses, to understand their views on their organization, its strengths and weaknesses, and their perceptions of how it ‘works’. We merge this information with public data (for instance, departmental vision or mission statements, which convey a sense of priorities or values) as well as prior literature about higher education culture. We also draw upon our experience in another setting as well as pilot testing data, and the result is a carefully-constructed set of dichotomous items that are offered to department stakeholders in survey form using an electronic survey platform. We also collect background and demographic information in the survey. The resulting data are analyzed using Cultural Consensus Theory (CCT) to extract meaningful information about the departmental culture from the perspectives of the stakeholder groups. ACTUAL OR ANTICIPATED OUTCOMES The resulting survey consists of two parts, each with sub-components. The two top level survey parts contain: (i) items common to all respondents in all settings (i.e. all institutions in this study), and (ii) a set of institution-specific items. Within those sections, the framing of the items is calibrated for the stakeholder groups so that items make sense to them within the context of their experience. The survey has been administered, and the data are being analyzed and interpreted presently. We expect the results to capture the specific elements of local culture within these institutions, as well as differences in perspectives and experience among the three primary stakeholder groups. CONCLUSIONS/RECOMMENDATIONS/SUMMARY This study demonstrates a scalable approach to survey development for the purposes of cultural characterization, and its use across settings and with multiple stakeholder groups. This work enables a very nuanced view of culture within a department, and these results can be used within academic departments to enable discussion about change, priorities, performance, and the work environment. 

We present the discovery and extensive follow-up of a remarkable fast-evolving optical transient, AT 2022aedm, detected by the Asteroid Terrestrial impact Last Alert Survey (ATLAS). In the ATLASoband, AT 2022aedm exhibited a rise time of 9 ± 1 days, reaching a luminous peak withM_g≈ −22 mag. It faded by 2 mag in thegband during the next 15 days. These timescales are consistent with other rapidly evolving transients, though the luminosity is extreme. Most surprisingly, the host galaxy is a massive elliptical with negligible current star formation. Radio and X-ray observations rule out a relativistic AT 2018cow–like explosion. A spectrum in the first few days after explosion showed short-lived Heiiemission resembling young core-collapse supernovae, but obvious broad supernova features never developed; later spectra showed only a fast-cooling continuum and narrow, blueshifted absorption lines, possibly arising in a wind withv≈ 2700 km s⁻¹. We identify two further transients in the literature (Dougie in particular, as well as AT 2020bot) that share similarities in their luminosities, timescales, color evolution, and largely featureless spectra and propose that these may constitute a new class of transients: luminous fast coolers. All three events occurred in passive galaxies at offsets of ∼4–10 kpc from the nucleus, posing a challenge for progenitor models involving massive stars or black holes. The light curves and spectra appear to be consistent with shock breakout emission, though this mechanism is usually associated with core-collapse supernovae. The encounter of a star with a stellar-mass black hole may provide a promising alternative explanation.

 

Abstract GW190814 was a compact object binary coalescence detected in gravitational waves by Advanced LIGO and Advanced Virgo that garnered exceptional community interest due to its excellent localization and the uncertain nature of the binary’s lighter-mass component (either the heaviest known neutron star, or the lightest known black hole). Despite extensive follow-up observations, no electromagnetic counterpart has been identified. Here, we present new radio observations of 75 galaxies within the localization volume at Δ t ≈ 35–266 days post-merger. Our observations cover ∼32% of the total stellar luminosity in the final localization volume and extend to later timescales than previously reported searches, allowing us to place the deepest constraints to date on the existence of a radio afterglow from a highly off-axis relativistic jet launched during the merger (assuming that the merger occurred within the observed area). For a viewing angle of ∼46° (the best-fit binary inclination derived from the gravitational wave signal) and assumed electron and magnetic field energy fractions of ϵ e = 0.1 and ϵ B = 0.01, we can rule out a typical short gamma-ray burst-like Gaussian jet with an opening angle of 15° and isotropic-equivalent kinetic energy 2 × 10 51 erg propagating into a constant-density medium n ≳ 0.1 cm −3 . These are the first limits resulting from a galaxy-targeted search for a radio counterpart to a gravitational wave event, and we discuss the challenges—and possible advantages—of applying similar search strategies to future events using current and upcoming radio facilities.