A new approach to modelling γ-ray burst afterglows: Using Gaussian processes to account for the systematics

The afterglow emission from gamma-ray bursts (GRBs) is a valuable source of information to understand the physics of these energetic explosions. The blast wave model has become the standard to describe the evolution of the afterglow emission over time and frequency. Thanks to recent developments in the theory of afterglows and numerical simulations of relativistic outflows, we are able to model the afterglow emission with realistic dynamics and radiative processes. Although the models agree with observations remarkably well, the afterglow emission still contains additional physics, instrumental systematics, and propagation effects which make the modelling of these events challenging. In this work, we present a new approach to modelling GRB afterglows, using Gaussian processes (GPs) to take into account systematics in the afterglow data. We show that, using this new approach, it is possible to obtain more reliable estimates of the explosion and microphysical parameters of GRBs. We present fit results for 5 long GRBs and find a preliminary correlation between the isotropic energetics and opening angles of GRBs, which confirms the idea of a common energy reservoir for the kinetic energy of long GRBs.Comment: Accepted to MNRAS. 10 pages, 5 figure

Rapid-response radio observations of short GRB 181123B with the Australia Telescope Compact Array

We introduce the Australia Telescope Compact Array (ATCA) rapid-response mode by presenting the first successful trigger on the short-duration gamma-ray burst (GRB) 181123B. Early-time radio observations of short GRBs may provide vital insights into the radio afterglow properties of Advanced LIGO- and Virgo-detected gravitational wave events, which will in turn inform follow-up strategies to search for counterparts within their large positional uncertainties. The ATCA was on target within 12.6 hr post-burst, when the source had risen above the horizon. While no radio afterglow was detected during the 8.3 hr observation, we obtained force-fitted flux densities of $7 \pm 12$ and $15 \pm 11~\mu$Jy at 5.5 and 9 GHz, respectively. Afterglow modelling of GRB 181123B showed that the addition of the ATCA force-fitted radio flux densities to the Swift X-ray Telescope detections provided more stringent constraints on the fraction of thermal energy in the electrons (log$\epsilon_e = -0.75^{+0.39}_{-0.40}$ rather than log$\epsilon_e = -1.13^{+0.82}_{-1.2}$ derived without the inclusion of the ATCA values), which is consistent with the range of typical $\epsilon_e$ derived from GRB afterglow modelling. This allowed us to predict that the forward shock may have peaked in the radio band $\sim10$ days post-burst, producing detectable radio emission $\gtrsim3-4$ days post-burst. Overall, we demonstrate the potential for extremely rapid radio follow-up of transients and the importance of triggered radio observations for constraining GRB blast wave properties, regardless of whether there is a detection, via the inclusion of force-fitted radio flux densities in afterglow modelling efforts.Comment: 15 pages, 7 figures, accepted for publication in MNRA

Geospatial information infrastructures

Manual of Digital Earth / Editors: Huadong Guo, Michael F. Goodchild, Alessandro Annoni .- Springer, 2020 .- ISBN: 978-981-32-9915-3Geospatial information infrastructures (GIIs) provide the technological, semantic,organizationalandlegalstructurethatallowforthediscovery,sharing,and use of geospatial information (GI). In this chapter, we introduce the overall concept and surrounding notions such as geographic information systems (GIS) and spatial datainfrastructures(SDI).WeoutlinethehistoryofGIIsintermsoftheorganizational andtechnologicaldevelopmentsaswellasthecurrentstate-of-art,andreflectonsome of the central challenges and possible future trajectories. We focus on the tension betweenincreasedneedsforstandardizationandtheever-acceleratingtechnological changes. We conclude that GIIs evolved as a strong underpinning contribution to implementation of the Digital Earth vision. In the future, these infrastructures are challengedtobecomeflexibleandrobustenoughtoabsorbandembracetechnological transformationsandtheaccompanyingsocietalandorganizationalimplications.With this contribution, we present the reader a comprehensive overview of the field and a solid basis for reflections about future developments

Rapid-response radio observations of short GRB 181123B with the Australia Telescope Compact Array

We introduce the Australia Telescope Compact Array (ATCA) rapid-response mode by presenting the first successful trigger on the short-duration gamma-ray burst (GRB) 181123B. Early-time radio observations of short GRBs may provide vital insights into the radio afterglow properties of Advanced LIGO- and Virgo-detected gravitational wave events, which will in turn inform follow-up strategies to search for counterparts within their large positional uncertainties. The ATCA was on target within 12.6 hr post-burst, when the source had risen above the horizon. While no radio afterglow was detected during the 8.3 hr observation, we obtained force-fitted flux densities of $7 \pm 12$ and $15 \pm 11~\mu$Jy at 5.5 and 9 GHz, respectively. Afterglow modelling of GRB 181123B showed that the addition of the ATCA force-fitted radio flux densities to the Swift X-ray Telescope detections provided more stringent constraints on the fraction of thermal energy in the electrons (log$\epsilon_e = -0.75^{+0.39}_{-0.40}$ rather than log$\epsilon_e = -1.13^{+0.82}_{-1.2}$ derived without the inclusion of the ATCA values), which is consistent with the range of typical $\epsilon_e$ derived from GRB afterglow modelling. This allowed us to predict that the forward shock may have peaked in the radio band $\sim10$ days post-burst, producing detectable radio emission $\gtrsim3-4$ days post-burst. Overall, we demonstrate the potential for extremely rapid radio follow-up of transients and the importance of triggered radio observations for constraining GRB blast wave properties, regardless of whether there is a detection, via the inclusion of force-fitted radio flux densities in afterglow modelling efforts

X-ray detector XRD on BeEagleSat and the development of the improved x-ray detector iXRD

Many interesting astrophysical objects are intense X-ray emitters. Hard X-ray observatories in various sizes have been operating in space and providing exciting scientific results that we cannot obtain in our laboratories on Earth. Nanosatellites with CdZnTe hard X-ray detectors have been launched into orbit as well, and the future holds great promise with such small satellites contributing significantly to high energy astrophysics. One of those satellites is the BeEagleSat which carried the X-ray detector (XRD)to low Earth orbit. The XRD has a 15⨯15⨯3 mm 3 volume CdZnTe detector, a cross-strip electrode design, a RENA readout chip controlled by an MSP 430 microcontroller. Due to a communication problem with the receiver, no science data could have been downloaded from the XRD. Recently, an improved version of the XRD has been designed (called the iXRD)and currently it is in the production phase. The improvements compared to the XRD are the larger volume crystal with almost three times the collecting area, a collimator to limit the field of view for focused scientific return, and a motherboard-daughterboard design to reduce electronic noise

EURAMET supplementary comparison EURAMET.L-S26.1, measurement of groove depth standards in the range 5 μm up to 0.9 mm

Main text In this supplementary comparison depths of six v-shaped grooves with nominal values 5/20/50/200/600 and 900 ?m were measured. The depths were measured according to ISO 5436-1. The PTB nickel depth setting standard was used as reference standard. PTB and MIKES measures all depths, CEM 2 and UME 3 larger depths. The results with associated uncertainties were in agreement. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/. The final report has been peer-reviewed and approved for publication by the CCL, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).</p