Rapid radio brightening of GRB 210702A Anderson, G E; Russell, T D; Fausey, H M ...
Monthly notices of the Royal Astronomical Society,
06/2023, Letnik:
523, Številka:
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ABSTRACT
We observed the rapid radio brightening of GRB 210702A with the Australia Telescope Compact Array (ATCA) just 11 h post-burst, tracking early-time radio variability over a 5 h period on ∼15 ...min time-scales at 9.0, 16.7, and 21.2 GHz. A broken power law fit to the 9.0 GHz light curve showed that the 5 h flare peaked at a flux density of 0.4 ± 0.1 mJy at ∼13 h post-burst. The observed temporal and spectral evolution is not expected in the standard internal–external shock model, where forward and reverse shock radio emission evolves on much longer time-scales. The early-time (<1 d) optical and X-ray light curves from the Neil Gehrels Swift Observatory demonstrated typical afterglow forward shock behaviour, allowing us to use blast wave physics to determine a likely homogeneous circumburst medium and an emitting electron population power-law index of p = 2.9 ± 0.1. We suggest that the early-time radio flare is likely due to weak interstellar scintillation (ISS), which boosted the radio afterglow emission above the ATCA sensitivity limit on minute time-scales. Using relations for ISS in the weak regime, we were able to place an upper limit on the size of the blast wave of ≲6 × 1016 cm in the plane of the sky, which is consistent with the theoretical forward shock size prediction of 8 × 1016 cm for GRB 210702A at ∼13 h post-burst. This represents the earliest ISS size constraint on a gamma-ray burst (GRB) blast wave to date, demonstrating the importance of rapid (<1 d) radio follow-up of GRBs using several-hour integrations to capture the early afterglow evolution and to track the scintillation over a broad frequency range.
ABSTRACT
Future detection of high-redshift gamma-ray bursts (GRBs) will be an important tool for studying the early Universe. Fast and accurate redshift estimation for detected GRBs is key for ...encouraging rapid follow-up observations by ground- and space-based telescopes. Low-redshift dusty interlopers pose the biggest challenge for GRB redshift estimation using broad photometric bands, as their high extinction can mimic a high-redshift GRB. To assess false alarms of high-redshift GRB photometric measurements, we simulate and fit a variety of GRBs using phozzy, a simulation code developed to estimate GRB photometric redshifts, and test the ability to distinguish between high- and low-redshift GRBs when using simultaneously observed photometric bands. We run the code with the wavelength bands and instrument parameters for the Photo-z Infrared Telescope (PIRT), an instrument designed for the Gamow mission concept. We explore various distributions of host galaxy extinction as a function of redshift, and their effect on the completeness and purity of a high-redshift GRB search with the PIRT. We find that for assumptions based on current observations, the completeness and purity range from ∼82 to 88 per cent and from ∼84 to $\gt 99~{{\ \rm per\ cent}}$, respectively. For the priors optimized to reduce false positives, only $\sim 0.6~{{\ \rm per\ cent}}$ of low-redshift GRBs will be mistaken as a high-redshift one, corresponding to ∼1 false alarm per 500 detected GRBs.
Context . Gamma-ray bursts (GRBs) are ideal probes of the Universe at high redshift (ɀ), pinpointing the locations of the earliest star-forming galaxies and providing bright backlights with simple ...featureless power-law spectra that can be used to spectrally fingerprint the intergalactic medium and host galaxy during the period of reionization. Future missions such as Gamow Explorer (hereafter Gamow) are being proposed to unlock this potential by increasing the rate of identification of high-ɀ (ɀ > 5) GRBs in order to rapidly trigger observations from 6 to 10 m ground telescopes, the James Webb Space Telescope (JWST), and the upcoming Extremely Large Telescopes (ELTs). Aims . Gamow was proposed to the NASA 2021 Medium-Class Explorer (MIDEX) program as a fast-slewing satellite featuring a wide-field lobster-eye X-ray telescope (LEXT) to detect and localize GRBs with arcminute accuracy, and a narrow-field multi-channel photo-ɀ infrared telescope (PIRT) to measure their photometric redshifts for > 80% of the LEXT detections using the Lyman- α dropout technique. We use a large sample of observed GRB afterglows to derive the PIRT sensitivity requirement. Methods . We compiled a complete sample of GRB optical–near-infrared (optical-NIR) afterglows from 2008 to 2021, adding a total of 66 new afterglows to our earlier sample, including all known high-ɀ GRB afterglows. This sample is expanded with over 2837 unpublished data points for 40 of these GRBs. We performed full light-curve and spectral-energy-distribution analyses of these after-glows to derive their true luminosity at very early times. We compared the high-ɀ sample to the comparison sample at lower redshifts. For all the light curves, where possible, we determined the brightness at the time of the initial finding chart of Gamow, at different high redshifts and in different NIR bands. This was validated using a theoretical approach to predicting the afterglow brightness. We then followed the evolution of the luminosity to predict requirements for ground- and space-based follow-up. Finally, we discuss the potential biases between known GRB afterglow samples and those to be detected by Gamow. Results . We find that the luminosity distribution of high-ɀ GRB afterglows is comparable to those at lower redshift, and we therefore are able to use the afterglows of lower-ɀ GRBs as proxies for those at high ɀ. We find that a PIRT sensitivity of 15 µJy (21 mag AB) in a 500 s exposure simultaneously in five NIR bands within 1000 s of the GRB trigger will meet the Gamow mission requirements. Depending on the ɀ and NIR band, we find that between 75% and 85% of all afterglows at ɀ > 5 will be recovered by Gamow at 5 σ detection significance, allowing the determination of a robust photo-ɀ. As a check for possible observational biases and selection effects, we compared the results with those obtained through population-synthesis models, and find them to be consistent. Conclusions . Gamow and other high-ɀ GRB missions will be capable of using a relatively modest 0.3 m onboard NIR photo-ɀ telescope to rapidly identify and report high-ɀ GRBs for further follow-up by larger facilities, opening a new window onto the era of reionization and the high-redshift Universe.
Knowing accurate saturated vapor pressures of explosives at ambient conditions is imperative to provide realistic boundaries on available vapor for ultra-trace detection. In quantifying vapor content ...emanating from low-volatility explosives, we observed discrepancies between the quantity of explosive expected based on literature vapor pressure values and the amount detected near ambient temperatures. Most vapor pressure measurements for low-volatility explosives, such as RDX (1,3,5-trinitro-1,3,5-triazinane) and HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazocane), have been made at temperatures far exceeding 25 °C and linear extrapolation of these higher temperature trends appears to underestimate vapor pressures near room temperature. Our goal was to measure vapor pressures as a function of temperature closer to ambient conditions. We used saturated RDX and HMX vapor sources at controlled temperatures to produce vapors that were then collected and analyzed via atmospheric flow tube-mass spectrometry (AFT-MS). The parts-per-quadrillion (ppqv) sensitivity of AFT-MS enabled measurement of RDX vapor pressures at temperatures as low as 7 °C and HMX vapor pressures at temperatures as low as 40 °C for the first time. Furthermore, these vapor pressures were corroborated with analysis of vapor generated by nebulizing low concentration solutions of RDX and HMX. We report updated vapor pressure values for both RDX and HMX. Based on our measurements, the vapor pressure of RDX at 25 °C is 3 ± 1 × 10–11 atm (i.e., 30 parts per trillion by volume, pptv), the vapor pressure of HMX is 1.0 ± 0.6 × 10–14 atm (10 ppqv) at 40 °C and, with extrapolation, HMX has a vapor pressure of 1.0 ± 0.6 × 10–15 atm (1.0 ppqv) at 25 °C.
Currently, over a billion people around the world lack access to clean drinking water, industrial wastewater treatment and reuse is limited, and conventional water treatment systems cannot adequately ...treat all contaminants of concern. Nanotechnology-enabled water treatment (NWT) has begun to emerge as a viable option to address many of the problems facing the water treatment status quo, either through cost reducing performance enhancements or filling unmet niches. Advancements in fundamental nanoscience allow unprecedented use of catalysis and energy from across the broad electromagnetic spectrum, as well as unique physicochemical properties, to purify drinking water, treat industrial wastewater, and access unconventional water supplies. However, before fully adopting NWT, it is imperative that the devices are both safe and sustainable, enhancing acceptance from consumers, government, non-government organizations, and industry. We suggest that we are in a unique window of time to "do nano right" by making key sustainability considerations very early in nano-water technology development. To this end, we have developed a framework based on three guiding research questions aimed at understanding the breadth of sustainability considerations for NWT at each of the four major life cycle stages - extraction, production, use, and end-of-life. In following this framework, researchers and product developers can design nano-enabled water treatment devices that perform well and are both safe and sustainable. By presenting the current state of sustainable NWT and specifying gaps in the literature, the present review aims to further develop NWT to be the best alternative to conventional water treatment across a variety of sectors.
Nanotechnology-enabled water treatment technologies have the potential to outperform conventional water treatment systems, but we must understand how to produce, use, and dispose of these technologies in a safe and sustainable way.
Future detection of high-redshift gamma-ray bursts (GRBs) will be an important tool for studying the early Universe. Fast and accurate redshift estimation for detected GRBs is key for encouraging ...rapid follow-up observations by ground- and space-based telescopes. Low-redshift dusty interlopers pose the biggest challenge for GRB redshift estimation using broad photometric bands, as their high extinction can mimic a high-redshift GRB. To assess false alarms of high-redshift GRB photometric measurements, we simulate and fit a variety of GRBs using phozzy, a simulation code developed to estimate GRB photometric redshifts, and test the ability to distinguish between high- and low-redshift GRBs when using simultaneously observed photometric bands. We run the code with the wavelength bands and instrument parameters for the Photo-z Infrared Telescope (PIRT), an instrument designed for the Gamow mission concept. We explore various distributions of host galaxy extinction as a function of redshift, and their effect on the completeness and purity of a high-redshift GRB search with the PIRT. We find that for assumptions based on current observations, the completeness and purity range from \(\sim 82\) to \(88\%\) and from \(\sim 84\) to \(>99\%\), respectively. For the priors optimized to reduce false positives, only \(\sim 0.6\%\) of low-redshift GRBs will be mistaken as a high-redshift one, corresponding to \(\sim 1\) false alarm per 500 detected GRBs.
Gamma-ray bursts (GRBs) are ideal probes of the Universe at high redshift (z > 5), pinpointing the locations of the earliest star-forming galaxies and providing bright backlights that can be used to ...spectrally fingerprint the intergalactic medium and host galaxy during the period of reionization. Future missions such as Gamow Explorer are being proposed to unlock this potential by increasing the rate of identification of high-z GRBs to rapidly trigger observations from 6-10 m ground telescopes, JWST, and the Extremely Large Telescopes. Gamow was proposed to the NASA 2021 Medium-Class Explorer (MIDEX) program as a fast-slewing satellite featuring a wide-field lobster-eye X-ray telescope (LEXT) to detect and localize GRBs, and a 30 cm narrow-field multi-channel photo-z infrared telescope (PIRT) to measure their photometric redshifts using the Lyman-alpha dropout technique. To derive the PIRT sensitivity requirement we compiled a complete sample of GRB optical-near-infrared afterglows from 2008 to 2021, adding a total of 66 new afterglows to our earlier sample, including all known high-z GRB afterglows. We performed full light-curve and spectral-energy-distribution analyses of these afterglows to derive their true luminosity at very early times. For all the light curves, where possible, we determined the brightness at the time of the initial finding chart of Gamow, at different high redshifts and in different NIR bands. We then followed the evolution of the luminosity to predict requirements for ground and space-based follow-up. We find that a PIRT sensitivity of 15 micro-Jy (21 mag AB) in a 500 s exposure simultaneously in five NIR bands within 1000s of the GRB trigger will meet the Gamow mission requirement to recover > 80% of all redshifts at z > 5.
The Epoch of Reionization (EoR) is a key period of cosmological history in which the intergalactic medium (IGM) underwent a major phase change from being neutral to almost completely ionized. ...Gamma-ray bursts (GRBs) are luminous and unique probes of their environments that can be used to study the timeline for the progression of the EoR. Here we present a detailed analysis of the ESO Very Large Telescope X-shooter spectrum of GRB 210905A, which resides at a redshift of z ~ 6.3. We focus on estimating the fraction of neutral hydrogen, xHI, on the line of sight to the host galaxy of GRB 210905A by fitting the shape of the Lyman-alpha damping wing of the afterglow spectrum. The X-shooter spectrum has a high signal to noise ratio, but the complex velocity structure of the host galaxy limits the precision of our conclusions. The statistically preferred model suggests a low neutral fraction with an 3-sigma upper limit of xHI < 0.15, indicating that the IGM around the GRB host galaxy is mostly ionized. We discuss complications in current analyses and potential avenues for future studies of the progression of the EoR and its evolution with redshift.
The valid assessment of vocabulary development in dual‐language‐learning infants is critical to developmental science. We developed the Dual Language Learners English‐Spanish (DLL‐ES) Inventories to ...measure vocabularies of U.S. English‐Spanish DLLs. The inventories provide translation equivalents for all Spanish and English items on Communicative Development Inventory (CDI) short forms; extended inventories based on CDI long forms; and Spanish language‐variety options. Item‐Response Theory analyses applied to Wordbank and Web‐CDI data (n = 2603, 12–18 months; n = 6722, 16–36 months; half female; 1% Asian, 3% Black, 2% Hispanic, 30% White, 64% unknown) showed near‐perfect associations between DLL‐ES and CDI long‐form scores. Interviews with 10 Hispanic mothers of 18‐ to 24‐month‐olds (2 White, 1 Black, 7 multi‐racial; 6 female) provide a proof of concept for the value of the DLL‐ES for assessing the vocabularies of DLLs.
We observed the rapid radio brightening of GRB 210702A with the Australian Telescope Compact Array (ATCA) just 11hr post-burst, tracking early-time radio variability over a 5hr period on ~15min ...timescales at 9.0, 16.7, and 21.2GHz. A broken power-law fit to the 9.0GHz light curve showed that the 5hr flare peaked at a flux density of 0.4+/-0.1mJy at ~13hr post-burst with a steep rise and decline. The observed temporal and spectral evolution are not expected in the standard internal-external shock model, where forward and reverse shock radio emission evolves on much longer timescales. The early-time (<1day) optical and X-ray light curves from the Neil Gehrels Swift Observatory demonstrated typical afterglow forward shock behaviour, allowing us to use blast wave physics to determine a likely homogeneous circumburst medium and an emitting electron population power-law index of p=2.9+/-0.1. We suggest the early-time radio flare is likely due to weak interstellar scintillation (ISS), which boosted the radio afterglow emission above the ATCA sensitivity limit on minute timescales. Using weak ISS relations, we were able to place an upper limit on the size of the blast wave of \(\leq6 \times 10^{16}\)cm in the plane of the sky, which is consistent with the theoretical forward shock size prediction of \(8\times10^{16}\)cm for GRB 210702A at ~13h post-burst. This represents the earliest ISS size constraint on a GRB blast wave to date, demonstrating the importance of rapid (<1day) radio follow-up of GRBs using several-hour integrations to capture the early afterglow evolution, and to track scintillation over a broad frequency range.
