Journal articles on the topic 'Afterglow'
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1
Lamb, Gavin P., Lorenzo Nativi, Stephan Rosswog, D. Alexander Kann, Andrew Levan, Christoffer Lundman, and Nial Tanvir. "Inhomogeneous Jets from Neutron Star Mergers: One Jet to Rule Them All." Universe 8, no. 12 (November 23, 2022): 612. http://dx.doi.org/10.3390/universe8120612.
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Using the resultant profiles from 3D hydrodynamic simulations of relativistic jets interacting with neutron star merger wind ejecta, we show how the inhomogeneity of energy and velocity across the jet surface profile can alter the observed afterglow lightcurve. We find that the peak afterglow flux depends sensitively on the observer’s line-of-sight, not only via the jet inclination but also through the jet rotation: for an observer viewing the afterglow within the GRB-bright jet core, we find a peak flux variability on the order <0.5 dex through rotational orientation and <1.3 dex for the polar inclination. An observed afterglow’s peak flux can be used to infer the jet kinetic energy, and where a top-hat jet is assumed, we find the range of inferred jet kinetic energies for our various model afterglow lightcurves (with fixed model parameters), covers ∼1/3 of the observed short GRB population. Additionally, we present an analytic jet structure function that includes physically motivated parameter uncertainties due to variability through the rotation of the source. An approximation for the change in collimation due to the merger ejecta mass is included and we show that by considering the observed range of merger ejecta masses from short GRB kilonova candidates, a population of merger jets with a fixed intrinsic jet energy is capable of explaining the observed broad diversity seen in short GRB afterglows.
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Boersma, O. M., J. van Leeuwen, E. A. K. Adams, B. Adebahr, A. Kutkin, T. Oosterloo, W. J. G. de Blok, et al. "A search for radio emission from double-neutron star merger GW190425 using Apertif." Astronomy & Astrophysics 650 (June 2021): A131. http://dx.doi.org/10.1051/0004-6361/202140578.
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Context. Detection of the electromagnetic emission from coalescing binary neutron stars (BNS) is important for understanding the merger and afterglow. Aims. We present a search for a radio counterpart to the gravitational-wave (GW) source GW190425, a BNS merger, using Apertif on the Westerbork Synthesis Radio Telescope (WSRT). Methods. We observed a field of high probability in the associated localisation region for three epochs at ΔT = 68, 90, 109 d post merger. We identified all sources that exhibit flux variations consistent with the expected afterglow emission of GW190425. We also looked for possible transients. These are sources that are only present in one epoch. In addition, we quantified our ability to search for radio afterglows in the fourth and future observing runs of the GW detector network using Monte Carlo simulations. Results. We found 25 afterglow candidates based on their variability. None of these could be associated with a possible host galaxy at the luminosity distance of GW190425. We also found 55 transient afterglow candidates that were only detected in one epoch. All of these candidates turned out to be image artefacts. In the fourth observing run, we predict that up to three afterglows will be detectable by Apertif. Conclusions. While we did not find a source related to the afterglow emission of GW190425, the search validates our methods for future searches of radio afterglows.
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Gottlieb, Ore, Ehud Nakar, and Tsvi Piran. "Detectability of neutron star merger afterglows." Monthly Notices of the Royal Astronomical Society 488, no. 2 (July 11, 2019): 2405–11. http://dx.doi.org/10.1093/mnras/stz1906.
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ABSTRACT VLBI and JVLA observations revealed that GW170817 involved a narrow jet (θj ≈ 4°) that dominated the afterglow peak at our viewing angle, θobs ≈ 20°. This implies that at the time of the afterglow peak, the observed signal behaved like an afterglow of a top-hat jet seen at θobs ≫ θj, and it can be modelled by analytic expressions that describe such jets. We use a set of numerical simulations to calibrate these analytic relations and obtain generic equations for the peak time and flux of such an afterglow as seen from various observing angles. Using the calibrated equations and the estimated parameters of GW170817, we estimate the detectability of afterglows from future double neutron star mergers during the Advanced LIGO/Virgo observation run O3. GW170817 took place at a relatively low-density environment. Afterglows of similar events will be detectable only at small viewing angles, θobs ≲ 20°, and only 20 per cent of the GW detections of these events will be accompanied by a detectable afterglow. At higher densities, more typical to sGRB sites, up to $70\,\rm{per\,cent}$ of the GW detections are expected to be followed by a detectable afterglow, typically at θobs ∼ 30°. We also provide the latest time one should expect an afterglow detection. We find that for typical parameters, if the jet emission had not been detected within about a year after the merger, it is unlikely to be ever detected.
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Aksulu, M. D., R. A. M. J. Wijers, H. J. van Eerten, and A. J. van der Horst. "A new approach to modelling gamma-ray burst afterglows: using Gaussian processes to account for the systematics." Monthly Notices of the Royal Astronomical Society 497, no. 4 (August 5, 2020): 4672–83. http://dx.doi.org/10.1093/mnras/staa2297.
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ABSTRACT The afterglow emission from gamma-ray bursts (GRBs) is a valuable source of information to understand the physics of these energetic explosions. The fireball model has become the standard to describe the evolution of the afterglow emission over time and frequency. Because of 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 that 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 five 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.
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Zhu, Jin-Ping, Yuan-Pei Yang, Bing Zhang, He Gao, and Yun-Wei Yu. "Kilonova and Optical Afterglow from Binary Neutron Star Mergers. I. Luminosity Function and Color Evolution." Astrophysical Journal 938, no. 2 (October 1, 2022): 147. http://dx.doi.org/10.3847/1538-4357/ac8e60.
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Abstract In the first work of this series, we adopt a GW170817-like viewing-angle-dependent kilonova model and the standard afterglow model with a light-curve distribution based on the properties of cosmological short gamma-ray burst afterglows to simulate the luminosity functions and color evolution of both kilonovae and optical afterglow emissions from binary neutron star (BNS) mergers. We find that ∼10% of the nearly-on-axis afterglows are brighter than the associated kilonovae at the peak time. These kilonovae would be significantly polluted by the associated afterglow emission. Only at large viewing angles with sin θ v ≳ 0.20 , the electromagnetic signals of most BNS mergers would be kilonova-dominated and some off-axis afterglows may emerge at ∼5–10 days after the mergers. At a brightness dimmer than ∼23–24 mag, according to their luminosity functions, the number of afterglows is much larger than that of kilonovae. Because the search depth of the present survey projects is <22 mag, the number of afterglow events that are detected via serendipitous observations would be much higher than that of kilonova events, consistent with the current observations. For the foreseeable survey projects (e.g., Mephisto, WFST, and LSST), whose search depths can reach ≳23–24 mag, the detection rate of kilonovae could have the same order of magnitude as afterglows. We also find that it may be difficult to use the fading rate in a single band to directly identify kilonovae and afterglows among various fast-evolving transients by serendipitous surveys. However, the color evolution between the optical and infrared bands can identify them because the color evolution patterns of these phenomena are unique compared with those of other fast-evolving transients.
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Wang, X. G., E. W. Liang, L. Li, J. J. Wei, and B. Zhang. "Luminosity Distribution of Gamma-ray Burst Optical Afterglows." Proceedings of the International Astronomical Union 8, S290 (August 2012): 335–36. http://dx.doi.org/10.1017/s1743921312020285.
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AbstractWe derive the optical afterglow luminosity distributions at different epoches for gamma-ray bursts (GRBs) from a sample of 146 GRBs that have a well-sampled optical afterglow lightcurve, then explore the luminosity function of GRB optical afterglows using the Monte Carlo simulation. We show that an intrinsic broken power-law luminosity function can well reproduced the observed magnitude distributions.
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LIANG, EN-WEI, HOUJUN LÜ, SHUANG-XI YI, BING ZHANG, BIN-BIN ZHANG, and JIN ZHANG. "DISCERNING EMISSION COMPONENTS IN EARLY AFTERGLOW DATA AND CONSTRAINING THE INITIAL LORENTZ FACTOR OF LONG GRB FIREBALL." International Journal of Modern Physics D 20, no. 10 (September 2011): 1955–59. http://dx.doi.org/10.1142/s0218271811020007.
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We prove that both the canonical and single power-law decay X-ray afterglow lightcurves of gamma-ray bursts (GRBs) observed with the Swift X-ray telescope may be an emission component radiated by external shocks prior to the GRB trigger. Our systematical analysis on both the early optical and X-ray afterglow data also indicates that they might be from different components. The detected optical emission possibly is dominated by the afterglow of the GRB fireball. The X-ray afterglows may be detected for some GRBs, but most of the detected X-rays for most GRBs are likely dominated by the prior X-ray component. With the deceleration feature in the early optical afterglow data, we estimate the initial Lorentz factors of the GRBs and discover a tight relation of the Lorentz factor to the isotropic gamma-ray energy.
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Marongiu, M., C. Guidorzi, G. Stratta, A. Gomboc, N. Jordana-Mitjans, S. Dichiara, S. Kobayashi, D. Kopač, and C. G. Mundell. "Radio data challenge the broadband modelling of GRB 160131A afterglow." Astronomy & Astrophysics 658 (January 27, 2022): A11. http://dx.doi.org/10.1051/0004-6361/202140403.
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Context. Gamma-ray burst (GRB) afterglows originate from the interaction between the relativistic ejecta and the surrounding medium. Consequently, their properties depend on several aspects: radiation mechanisms, relativistic shock micro-physics, circumburst environment, and the structure and geometry of the relativistic jet. While the standard afterglow model accounts for the overall spectral and temporal evolution for a number of GRBs, its validity limits emerge when the data set is particularly rich and constraining, especially in the radio band. Aims. We aimed to model the afterglow of the long GRB 160131A (redshift z = 0.972), for which we collected a rich, broadband, and accurate data set, spanning from 6 × 108 Hz to 7 × 1017 Hz in frequency, and from 330 s to 160 days post-burst in time. Methods. We modelled the spectral and temporal evolution of this GRB afterglow through two approaches: (1) the adoption of empirical functions to model an optical/X-ray data set, later assessing their compatibility with the radio domain; and (2) the inclusion of the entire multi-frequency data set simultaneously through the Python package named SAGA (Software for AfterGlow Analysis), to obtain an exhaustive and self-consistent description of the micro-physics, geometry, and dynamics of the afterglow. Results. From deep broadband analysis (from radio to X-ray frequencies) of the afterglow light curves, GRB 160131A outflow shows evidence of jetted emission. Moreover, we observe dust extinction in the optical spectra, and energy injection in the optical/X-ray data. Finally, radio spectra are characterised by several peaks that could be due to either interstellar scintillation (ISS) effects or a multi-component structure. Conclusions. The inclusion of radio data in the broadband set of GRB 160131A makes a self-consistent modelling barely attainable within the standard model of GRB afterglows.
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Zhang, Bing, Peter Mészáros, and Junfeng Wang. "Some Recent Developments in γ-ray Burst Afterglow and Prompt Emission Models." Symposium - International Astronomical Union 214 (2003): 311–20. http://dx.doi.org/10.1017/s0074180900194641.
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Extensive observational campaigns of afterglow hunting have greatly enriched our understanding of the gamma-ray burst (GRB) phenomenon. Efforts have been made recently to explore some afterglow properties or signatures that will be tested by the on-going or the future observational campaigns yet come. These include the properties of GRB early afterglows in the temporal domain; the GeV-TeV afterglow signatures in the spectral domain; as well as a global view about the GRB universal structured jet configuration. These recent efforts are reviewed. Within the standard cosmological fireball model, the very model(s) responsible for the GRB prompt emission is (are) not identified. These models are critically reviewed and confronted with the current data.
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Guarini, Ersilia, Irene Tamborra, Damien Bégué, Tetyana Pitik, and Jochen Greiner. "Multi-messenger detection prospects of gamma-ray burst afterglows with optical jumps." Journal of Cosmology and Astroparticle Physics 2022, no. 06 (June 1, 2022): 034. http://dx.doi.org/10.1088/1475-7516/2022/06/034.
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Abstract Some afterglow light curves of gamma-ray bursts (GRBs) exhibit very complex temporal and spectral features, such as a sudden intensity jump about one hour after the prompt emission in the optical band. We assume that this feature is due to the late collision of two relativistic shells and investigate the corresponding high-energy neutrino emission within a multi-messenger framework, while contrasting our findings with the ones from the classic afterglow model. For a constant density circumburst medium, the total number of emitted neutrinos can increase by about an order of magnitude when an optical jump occurs with respect to the self-similar afterglow scenario. By exploring the detection prospects with the IceCube Neutrino Observatory and future radio arrays such as IceCube-Gen2 radio, RNO-G and GRAND200k, as well as the POEMMA spacecraft, we conclude that the detection of neutrinos with IceCube-Gen2 radio could enable us to constrain the fraction of GRB afterglows with a jump as well as the properties of the circumburst medium. We also investigate the neutrino signal expected for the afterglows of GRB 100621A and a GRB 130427A-like burst with an optical jump. The detection of neutrinos from GRB afterglows could be crucial to explore the yet-to-be unveiled mechanism powering the optical jumps.
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Lamb, Gavin P., and Shiho Kobayashi. "Reverse shocks in the relativistic outflows of gravitational wave-detected neutron star binary mergers." Monthly Notices of the Royal Astronomical Society 489, no. 2 (August 16, 2019): 1820–27. http://dx.doi.org/10.1093/mnras/stz2252.
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ABSTRACT The afterglows to gamma-ray bursts (GRBs) are due to synchrotron emission from shocks generated as an ultrarelativistic outflow decelerates. A forward and a reverse shock will form, however, where emission from the forward shock is well studied as a potential counterpart to gravitational wave-detected neutron star mergers the reverse shock has been neglected. Here, we show how the reverse shock contributes to the afterglow from an off-axis and structured outflow. The off-axis reverse shock will appear as a brightening feature in the rising afterglow at radio frequencies. For bursts at ∼100 Mpc, the system should be inclined ≲20° for the reverse shock to be observable at ∼0.1–10 d post-merger. For structured outflows, enhancement of the reverse shock emission by a strong magnetic field within the outflow is required for the emission to dominate the afterglow at early times. Early radio photometry of the afterglow could reveal the presence of a strong magnetic field associated with the central engine.
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STAFF, J., B. NIEBERGAL, and R. OUYED. "A THREE-STAGE MODEL FOR THE INNER ENGINE OF GRBs: PROMPT EMISSION AND EARLY AFTERGLOW." International Journal of Modern Physics D 17, no. 09 (September 2008): 1383–89. http://dx.doi.org/10.1142/s0218271808012954.
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We describe a model within the "quark-nova" scenario to interpret the recent observations of early X-ray afterglows of long gamma-ray bursts (GRBs) with the Swift satellite. This is a three-stage model within the context of a core-collapse supernova. STAGE 1 is an accreting (proto-) neutron star leading to a possible delay between the core collapse and the GRB. STAGE 2 is accretion onto a quark star, launching an ultrarelativistic jet generating the prompt GRB. This jet also creates the afterglow as the jet interacts with the surrounding medium creating an external shock. Slower shells ejected from the quark star (during accretion), can re-energize the external shock leading to a flatter segment in the X-ray afterglow. STAGE 3, which occurs only if the quark star collapses to form a black hole, consists of an accreting black hole. The jet launched in this accretion process interacts with the preceding quark star jet, and could generate the flaring activity frequently seen in early X-ray afterglows. Alternatively, a STAGE 2b can occur in our model if the quark star does not collapse to a black hole. The quark star in this case can then spin down due to magnetic braking, and the spin down energy may lead to flattening in the X-ray afterglow as well. This model seems to account for both the energies and the timescales of GRBs, in addition to the newly discovered early X-ray afterglow features.
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Duque, R., F. Daigne, and R. Mochkovitch. "Radio afterglows of binary neutron star mergers: a population study for current and future gravitational wave observing runs." Astronomy & Astrophysics 631 (October 17, 2019): A39. http://dx.doi.org/10.1051/0004-6361/201935926.
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Following the historical observations of GW170817 and its multi-wavelength afterglow, more radio afterglows from neutron star mergers are expected in the future as counterparts to gravitational wave inspiral signals. Our aim is to describe these events using our current knowledge of the population of neutron star mergers based on gamma-ray burst science, and taking into account the sensitivities of current and future gravitational wave and radio detectors. We combined analytical models for the merger gravitational wave and radio afterglow signals to a population model prescribing the energetics, circum-merger density and other relevant parameters of the mergers. We reported the expected distributions of observables (distance, orientation, afterglow peak time and flux, etc.) for future events and studied how these can be used to further probe the population of binary neutron stars, their mergers and related outflows during future observing campaigns. In the case of the O3 run of the LIGO-Virgo Collaboration, the radio afterglow of one third of gravitational-wave-detected mergers should be detectable (and detected if the source is localized thanks to the kilonova counterpart) by the Very Large Array. Furthermore, these events should have viewing angles similar to that of GW170817. These findings confirm the radio afterglow as a powerful insight into these events, although some key afterglow-related techniques, such as very long baseline interferometry imaging of the merger remnant, may no longer be feasible as the gravitational wave horizon increases.
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Liu, Zi Ran, Rui Xia Zhong, Hui Zhao, and Xiao Yan Zhang. "Influence on Afterglow Spectra due to Different Phases of Zn3(PO4)2: Mn2+." Applied Mechanics and Materials 423-426 (September 2013): 415–18. http://dx.doi.org/10.4028/www.scientific.net/amm.423-426.415.
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High temperature solid state reaction has been used to prepare Zn3(PO4)2: Mn2+. XRD analysis shows that different phases have been generated with different Mn2+ doping concentration at the same sintering temperature. Low Mn2+ doping concentration is conducive to form α phase, while γ is in favor of high Mn2+ doping concentration. In α phase, the emission spectrum of Mn2+ is a wide emission band peaking at 542 nm, green fluorescence. In γ phase, the emission spectrum of Mn2+ is a wide emission band peaking at 608 nm, red fluorescence. In the both phases, green and red afterglows have been observed. The red afterglow in γ phase has stronger initial brightness and longer afterglow decay time than the green afterglow in α phase, the reason of which lies in the larger trap concentration in γ phase.
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Chen, Shengnan, Xudong Wen, He Gao, Kai Liao, Liangduan Liu, Litao Zhao, Zhengxiang Li, et al. "Searching for Gravitationally Lensed Gamma-Ray Bursts with Their Afterglows." Astrophysical Journal 924, no. 2 (January 1, 2022): 49. http://dx.doi.org/10.3847/1538-4357/ac31ad.
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Abstract Gamma-ray bursts (GRBs) at high redshifts are expected to be gravitationally lensed by objects of different mass scales. Other than a single recent claim, no lensed GRB has been detected so far by using gamma-ray data only. In this paper, we suggest that multiband afterglow data might be an efficient way to search for lensed GRB events. Using the standard afterglow model, we calculate the characteristics of the lensed afterglow lightcurves under the assumption of two popular analytic lens models: the point-mass and singular isothermal sphere models. In particular, when different lensed images cannot be resolved, their signals would be superimposed together with a given time delay. In this case, the X-ray afterglows are likely to contain several X-ray flares of similar width in linear scale and similar spectrum, and the optical afterglow lightcurve will show re-brightening signatures. Since the lightcurves from the image arriving later would be compressed and deformed in the logarithmic timescale, the larger time delay (i.e., the larger mass of the lens), the easier it is to identify the lensing effect. We analyzed the archival data of optical afterglows and found one potential candidate of the lensed GRB (130831A) with time delay ∼500 s; however, observations of this event in gamma-ray and X-ray bands seem not to support the lensing hypothesis. In the future, with the cooperation of the all-sky monitoring gamma-ray detectors and multiband sky survey projects, the method proposed in this paper would be more efficient in searching for strongly lensed GRBs.
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Huang, Y. F., T. Lu, Z. G. Dai, and K. S. Cheng. "Beaming Effects in Gamma-Ray Burst Afterglows." Symposium - International Astronomical Union 214 (2003): 321–22. http://dx.doi.org/10.1017/s0074180900194653.
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Based on a refined dynamical model, afterglows from jetted γ-ray burst (GRB) remnants are investigated numerically. Measuring of GRB beaming by using orphan afterglow surveys is addressed. The possible existence of a kind of cylindrical jets is also discussed.
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Yamazaki, Ryo, Yuri Sato, Takanori Sakamoto, and Motoko Serino. "Less noticeable shallow decay phase in early X-ray afterglows of GeV/TeV-detected gamma-ray bursts." Monthly Notices of the Royal Astronomical Society 494, no. 4 (April 24, 2020): 5259–69. http://dx.doi.org/10.1093/mnras/staa1095.
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ABSTRACT The nature of the shallow decay phase in the X-ray afterglow of the gamma-ray burst (GRB) is not yet clarified. We analyse the data of early X-ray afterglows of 26 GRBs triggered by Burst Alert Telescope onboard Neil Gehrels Swift Observatory and subsequently detected by Fermi Large Area Telescope (LAT) and/or Imaging Atmospheric Cherenkov Telescopes. It is found that nine events (including two out of three very-high-energy gamma-ray events) have no shallow decay phase and that their X-ray afterglow light curves are well described by single power-law model except for the jet break at later epoch. The rest are fitted by double power-law model and have a break in the early epoch (around ks), however, eight events (including a very-high-energy gamma-ray event) have the pre-break decay index larger than 0.7. We also analyse the data of well-sampled X-ray afterglows of GRBs without LAT detection and compare their decay properties with those of high-energy and very-high-energy gamma-ray events. It is found that for the GeV/TeV bursts, the fraction of events whose X-ray afterglows are described by single power law is significantly larger than those for non-GeV/TeV GRBs. Even if the GeV/TeV GRBs have shallow decay phase, their decay slope tends to be steeper than non-GeV/TeV bursts, that is, they have less noticeable shallow decay phase in the early X-ray afterglow. A possible interpretation along with the energy injection model is briefly discussed.
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Laskar, Tanmoy, Alicia Rouco Escorial, Genevieve Schroeder, Wen-fai Fong, Edo Berger, Péter Veres, Shivani Bhandari, et al. "The First Short GRB Millimeter Afterglow: The Wide-angled Jet of the Extremely Energetic SGRB 211106A." Astrophysical Journal Letters 935, no. 1 (August 1, 2022): L11. http://dx.doi.org/10.3847/2041-8213/ac8421.
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Abstract We present the discovery of the first millimeter afterglow of a short-duration γ-ray burst (SGRB) and the first confirmed afterglow of an SGRB localized by the GUANO system on Swift. Our Atacama Large Millimeter/Sub-millimeter Array (ALMA) detection of SGRB 211106A establishes an origin in a faint host galaxy detected in Hubble Space Telescope imaging at 0.7 ≲ z ≲ 1.4. From the lack of a detectable optical afterglow, coupled with the bright millimeter counterpart, we infer a high extinction, A V ≳ 2.6 mag along the line of sight, making this one of the most highly dust-extincted SGRBs known to date. The millimeter-band light curve captures the passage of the synchrotron peak from the afterglow forward shock and reveals a jet break at t jet = 29.2 − 4.0 + 4.5 days. For a presumed redshift of z = 1, we infer an opening angle, θ jet = (15.°5 ± 1.°4), and beaming-corrected kinetic energy of log ( E K / erg ) = 51.8 ± 0.3 , making this one of the widest and most energetic SGRB jets known to date. Combining all published millimeter-band upper limits in conjunction with the energetics for a large sample of SGRBs, we find that energetic outflows in high-density environments are more likely to have detectable millimeter counterparts. Concerted afterglow searches with ALMA should yield detection fractions of 24%–40% on timescales of ≳2 days at rates of ≈0.8–1.6 per year, outpacing the historical discovery rate of SGRB centimeter-band afterglows.
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Yang, Tianjia, Yunzhong Wang, Jixuan Duan, Shuangyu Wei, Saixing Tang, and Wang Zhang Yuan. "Time-Dependent Afterglow from a Single Component Organic Luminogen." Research 2021 (August 27, 2021): 1–11. http://dx.doi.org/10.34133/2021/9757460.
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Pure organic luminogens with long-persistent luminescence have been extensively studied, on account of their fundamental research significance and diverse utilizations in anticounterfeiting, bioimaging, encryption, organic light-emitting diodes, chemo-sensing, etc. However, time-dependent color-tunable afterglow is rarely reported, especially for single-component materials. In this work, we reported an organic luminogen with time-dependent afterglow, namely, benzoyleneurea (BEU), with multiple persistent room-temperature phosphorescence (p-RTP) and thermally activated delayed fluorescence (TADF) in single crystals. While the lifetime of TADF is relatively short (~1.2 ms), those for p-RTP are as long as around 369~754 ms. The comparable but different decay rates of diversified p-RTP emissions endow BEU crystals with obvious time-dependent afterglow. The existence of multiple emissions can be reasonably illustrated by the clustering-triggered emission (CTE) mechanism. Single-crystal structure illustrates that the combination of benzene ring and nonconventional chromophores of ureide helps facilitate divergent intermolecular interactions, which contribute to the formation of varying emissive species. Moreover, its methyl- and chloro-substituted derivatives show similar multiple p-RTP emissions. However, no time-dependent afterglows are observed in their crystals, due to the highly approaching lifetimes. The afterglow color variation of BEU crystals grants its applications in advanced anticounterfeiting field and information encryption.
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Kann, D. A., P. Schady, E. F. Olivares, S. Klose, A. Rossi, D. A. Perley, B. Zhang, et al. "The optical/NIR afterglow of GRB 111209A: Complex yet not unprecedented." Astronomy & Astrophysics 617 (September 2018): A122. http://dx.doi.org/10.1051/0004-6361/201731292.
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Context. Afterglows of gamma-ray bursts (GRBs) are simple in the most basic model, but can show many complex features. The ultra-long duration GRB 111209A, one of the longest GRBs ever detected, also has the best-monitored afterglow in this rare class of GRBs. Aims. We want to address the question whether GRB 111209A was a special event beyond its extreme duration alone, and whether it is a classical GRB or another kind of high-energy transient. The afterglow may yield significant clues. Methods. We present afterglow photometry obtained in seven bands with the GROND imager as well as in further seven bands with the Ultraviolet/Optical Telescope (UVOT) on-board the Neil Gehrels Swift Observatory. The light curve is analysed by multi-band modelling and joint fitting with power-laws and broken power-laws, and we use the contemporaneous GROND data to study the evolution of the spectral energy distribution. We compare the optical afterglow to a large ensemble we have analysed in earlier works, and especially to that of another ultra-long event, GRB 130925A. We furthermore undertake a photometric study of the host galaxy. Results. We find a strong, chromatic rebrightening event at ≈0.8 days after the GRB, during which the spectral slope becomes redder. After this, the light curve decays achromatically, with evidence for a break at about 9 days after the trigger. The afterglow luminosity is found to not be exceptional. We find that a double-jet model is able to explain the chromatic rebrightening. The afterglow features have been detected in other events and are not unique. Conclusions. The duration aside, the GRB prompt emission and afterglow parameters of GRB 111209A are in agreement with the known distributions for these parameters. While the central engine of this event may differ from that of classical GRBs, there are multiple lines of evidence pointing to GRB 111209A resulting from the core-collapse of a massive star with a stripped envelope.
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Krühler, Thomas. "Optical and near-infrared flares in GRB afterglows." Proceedings of the International Astronomical Union 7, S279 (April 2011): 46–53. http://dx.doi.org/10.1017/s1743921312012677.
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AbstractAmong the diversities in the very early evolution of GRB afterglows are bright optical/near-infrared flares before or superimposed onto an otherwise smoothly decaying afterglow light curve. A lot has been learned about GRBs by using an optical flare or lack thereof as a diagnostic of the emission mechanisms and outflow conditions. In this contribution I will review the observational properties of rising and decaying light-curves in GRB afterglows, discuss their possible physical origins, and highlight in which way they help in understanding GRB and afterglows physics.
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Basu, D. "GRB 011211: An alternative interpretation of the optical and X-ray spectra in terms of blueshifts." Canadian Journal of Physics 87, no. 6 (June 2009): 721–27. http://dx.doi.org/10.1139/p09-057.
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The redshift of the gamma-ray burst (GRB) GRB 011211 has been determined as 2.14 from several absorption lines seen in the spectrum of its optical afterglow. The spectrum of its X-ray afterglow exhibited several emission lines, and their identification led to a mean redshift 1.862. A supernova model has been proposed based on the redshift of the GRB as 2.141. It is shown here that the redshift interpretation cannot explain the observed spectra, as some serious inconsistencies exist in the process of redshift determinations in spectra of both optical and X-ray afterglows. In view of that, an alternative interpretation of the spectra is presented in terms of blueshifts. An ejection mechanism is proposed as a possible scenario to explain the blueshifted spectrum.
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de Ugarte Postigo, Antonio. "Absorption features in the X-shooter GRB afterglow sample." Proceedings of the International Astronomical Union 11, A29B (August 2015): 252. http://dx.doi.org/10.1017/s1743921316005202.
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AbstractSince 2009 X-shooter has collected spectroscopy of over 80 gamma-ray burst afterglows with redshifts ranging from 0.05 to 6.3. Thanks to its efficiency, broad wavelength coverage (3,000 to 24,800 Å), and intermediate spectral resolution (R~8,000) it has become the most efficient tool for gamma-ray burst afterglow spectroscopy. In this Focus Meeting we presented the sample and some preliminary results of the analysis of absorption systems.
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Zhang, Bo, Liang-Duan Liu, Tian-Rui Sun, Fen Lyu, and Xue-Feng Wu. "Diagnosing the Circumburst Environment with Multiband Gamma-Ray Burst Radio Afterglows." Astrophysical Journal 927, no. 1 (March 1, 2022): 84. http://dx.doi.org/10.3847/1538-4357/ac4695.
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Abstract It has been widely recognized that gamma-ray burst (GRB) afterglows arise from interactions between the GRB outflow and circumburst medium, while their evolution follows the behaviors of relativistic shock waves. Assuming the distribution of circumburst medium follows a general power-law form, that is, n = A * R −k , where R denotes the distance from the burst, it is obvious that the value of the density-distribution index k can affect the behaviors of the afterglow. In this paper, we analyze the temporal and spectral behaviors of GRB radio afterglows with arbitrary k values. In the radio band, a standard GRB afterglow produced by a forward shock exhibits a late-time flux peak, and the relative peak fluxes, as well as peak times at different frequencies, show dependencies on k. Thus, with multiband radio-peak observations, one can determine the density profile of the circumburst medium by comparing the relations between peak flux/time and frequency at each observing band. Also, the effects of transrelativistic shock waves, as well as jets in afterglows, are discussed. By analyzing 31 long and 1 short GRB with multiband data of radio afterglows, we find that nearly half of them can be explained with a uniform interstellar medium (k = 0), ∼1/5 can be constrained to exhibiting a stellar-wind environment (k = 2), while less than ∼1/3 of the samples show 0 < k < 2.
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Mohan, Sreelekshmi, M. Saleem, and Lekshmi Resmi. "Detectability of electromagnetic counterparts from neutron star mergers: prompt emission versus afterglow." Monthly Notices of the Royal Astronomical Society 511, no. 2 (December 20, 2021): 2356–66. http://dx.doi.org/10.1093/mnras/stab3120.
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ABSTRACT Electromagnetic observations of the first binary neutron star (BNS) merger detected in gravitational waves, GW170817, have established that relativistic jets can be successfully launched in BNS mergers. Typically, such jets produce emission in two phases: γ-ray prompt emission and multiwavelength afterglow. Because of relativistic beaming and the jet’s angular structure, the detectability of both these counterparts is dependent on the angle (θ${\rm v}$) between the observer’s line of sight and the jet axis. We compare the detectability of prompt and afterglow emission from off-axis jets, assuming standard detector thresholds such as that of Fermi Gamma-ray Burst Monitor (GBM), Chandra, and Jansky Very Large Array (VLA). We find that for top-hat jets, afterglow is a more likely counterpart than the prompt emission even with unfavourable afterglow parameters. For structured jets with a Gaussian profile, prompt emission is more promising than the afterglows at extreme viewing angles, under the assumption that the total energy emitted in the prompt phase equals the kinetic energy of the outflow. Assuming a Gaussian jet profile, we forecast the population of γ-ray detections and find that extreme viewing angle events like GRB 170817A will be rare. In our simulated sample, the observed isotropic equivalent energy in γ-rays is moderately correlated with the viewing angle, such that a low Eiso,γ is almost always associated with a high off-axis viewing angle.
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Guessoum, N., H. Zitouni, and R. Mochkovitch. "Detecting the imprint of a kilonova or supernova in short gamma-ray burst afterglows." Astronomy & Astrophysics 620 (December 2018): A131. http://dx.doi.org/10.1051/0004-6361/201832940.
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Context. Short gamma-ray bursts (GRBs) result from mergers of two neutron stars or from collapsars, but probably at a smaller rate. In the first case, a kilonova occurs while in the second case a Type Ic supernova is expected. Aims. Even if future observations of kilonovae in association with gravitational wave events provide better data, detecting a kilonova during an afterglow follow-up would remain useful for exploring the diversity of the kilonova phenomenon. As supernovae produce a weaker gravitational signal, afterglow follow-up will be the only possible method to find one. In this work, we identify the conditions of the burst energy, external density, kilonova mass, supernova luminosity, that are necessary for the detection of a kilonova or supernova in the follow-up of short GRB afterglows. Methods. We have used a simple kilonova model to obtain the peak luminosities and times as a function of mass, expansion velocity and ejected matter opacity. Afterglow light curves are computed for a uniform medium and a stellar wind, in the kilonova and supernova cases, respectively. Results. We represent, using diagrams of the burst kinetic energy vs. density of the external medium, the domains where the kilonova or supernova at maximum is brighter than the afterglow. In the kilonova case we vary the mass, the jet opening angle and the microphysics parameters; for supernovae, we consider SN 98bw-like and ten times dimmer events, and again vary the jet opening angle and the microphysics parameters.
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Salafia, O. S., G. Ghirlanda, S. Ascenzi, and G. Ghisellini. "On-axis view of GRB 170817A." Astronomy & Astrophysics 628 (July 29, 2019): A18. http://dx.doi.org/10.1051/0004-6361/201935831.
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The peculiar short gamma-ray burst (SGRB) GRB 170817A has been firmly associated to the gravitational wave event GW170817, which has been unanimously interpreted as due to the coalescence of a double neutron star binary. The unprecedented behaviour of the non-thermal afterglow led to a debate over its nature, which was eventually settled by high-resolution VLBI observations that strongly support the off-axis structured jet scenario. Using information on the jet structure derived from multi-wavelength fitting of the afterglow emission and of the apparent VLBI image centroid motion, we compute the appearance of a GRB 170817A-like jet as seen by an on-axis observer and compare it to the previously observed population of SGRB afterglows and prompt emission events. We find that the intrinsic properties of the GRB 170817A jet are representative of a typical event in the SGRB population, hinting at a quasi-universal jet structure. The diversity in the SGRB afterglow population could therefore be ascribed in large part to extrinsic (redshift, density of the surrounding medium, viewing angle) rather than intrinsic properties. Although more uncertain, the comparison can be extended to the prompt emission properties, leading to similar conclusions.
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Zhao, Xiao-Hong, and Kang-Fa Cheng. "Afterglow Light Curves from Off-Axis GRB Jets in Stratified Circumburst Medium." Universe 8, no. 11 (November 7, 2022): 588. http://dx.doi.org/10.3390/universe8110588.
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We study the gamma-ray burst (GRB) afterglow light curves produced by an off-axis jet in a stratified circumburst medium and summarize the temporal indices of the coasting phase, the deceleration phase, the Newtonian phase, and the deep Newtonian phase for various viewing angles and power-law indices of medium density. Generally, the afterglow light curves of off-axis GRBs in the homogeneous interstellar medium have a steep rise arising due to jet deceleration. In the stratified medium, the flux rises is more shallow but peaks earlier for the same viewing angle due to faster deceleration of the jet running into the denser stratified medium, compared with the case of the interstellar medium (ISM). Observations of off-axis bursts will possibly increase over the coming years due to the arrival of the multi-messenger era and the forthcoming surveys in multiple bands. The temporal indices of off-axis afterglows derived in the paper will provide a reference for comparison with the observations and can diagnose the circumburst environment. The numerical code calculating the afterglow light curve also can be used to fit the multi-wavelength light curves.
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Jordan, A. Van. "afterglow." Callaloo 27, no. 3 (2004): 653. http://dx.doi.org/10.1353/cal.2004.0124.
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Tupper, Angie Lea. "Afterglow." UnderCurrents: Journal of Critical Environmental Studies 21 (October 18, 2022): 8–10. http://dx.doi.org/10.25071/2292-4736/40283.
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You can see Afterglow in motion at https://tiny.cc/uc_afterglow or https://youtu.be/kjKQr38c7qA.This mixed media piece explores the relationship between memory and home videos. The chosen scene is an everyday glimpse of childhood recreation: my cousins and I swivel in the sand at the water’s edge. I have a distinct memory of the sunshine wicking water droplets from my skin with its radiant warmth, but when I return to re-watch the home video, the light projecting from the screen is an undeniably overcast grey. Even with this discrepancy between my body memory and the recording, I question how much my recollection is a testimony of the immediate sensory experience and how much it is an adaptation of the home video that I have seen replayed so many times. It is one of few recordings that capture my cousin Oliver and me together; 2022 marks the fourteen-year anniversary of his death. The light that bounced off of our forms, that summer afternoon, is re-animated with each replaying of the video. Memory is re-minded with each re-watching.My process developed as a response to this shifting palimpsest of recollection. After transferring twelve evenly-spaced video frames to canvas, I hand-painted and beaded the degraded stills to match the coloration of my mind’s image. In their final iteration, the canvases are presented in sequence as a lenticular print. Moving in tandem with the viewer, the effect mirrors the physicality of body memory. Each retouched frame can only be viewed in a fugitive moment. The sequence provokes the viewer to waltz around the scene, back and forth, through impressions of time. In contrast, the vertical plastic lenses of the lenticular print recall the striations of traditional televisions. Painterly textures and interactive motion compete with an impression of flatness and locked recording.It is false to say that the screen is incapable of putting us ‘in the presence of’ the actor. It does so in the same way as a mirror . . . but it is a mirror with a delayed reflection, the tin foil of which retains the image. (Bazin 97)
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Vestrand, W. T., J. A. Wren, A. Panaitescu, P. R. Wozniak, H. Davis, D. M. Palmer, G. Vianello, et al. "The Bright Optical Flash and Afterglow from the Gamma-Ray Burst GRB 130427A." Science 343, no. 6166 (November 21, 2013): 38–41. http://dx.doi.org/10.1126/science.1242316.
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The optical light generated simultaneously with x-rays and gamma rays during a gamma-ray burst (GRB) provides clues about the nature of the explosions that occur as massive stars collapse. We report on the bright optical flash and fading afterglow from powerful burst GRB 130427A. The optical and >100–megaelectron volt (MeV) gamma-ray flux show a close correlation during the first 7000 seconds, which is best explained by reverse shock emission cogenerated in the relativistic burst ejecta as it collides with surrounding material. At later times, optical observations show the emergence of emission generated by a forward shock traversing the circumburst environment. The link between optical afterglow and >100-MeV emission suggests that nearby early peaked afterglows will be the best candidates for studying gamma-ray emission at energies ranging from gigaelectron volts to teraelectron volts.
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Pellouin, Clément, and Frédéric Daigne. "The Off-Axis Afterglow of GW170817: Flux Prediction at Very High Energies." Proceedings of the International Astronomical Union 16, S363 (June 2020): 216–19. http://dx.doi.org/10.1017/s1743921322000576.
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AbstractThe binary neutron star merger gravitational-wave event GW170817 and observations of the subsequent electromagnetic signals at different wavelengths have helped better understand the outflows that follow these mergers. In particular, the off-axis afterglow of the jetted ejecta has allowed to probe the lateral structure of such jets, especially thanks to VLBI imagery of the source. In this work, we model this afterglow including a decelerating jet with lateral structure, while synchrotron emission and synchrotron self-Compton scatterings power the jet radiation. In particular, we extend our analysis to very high energies and predict the light curve in the energy range of H.E.S.S. and the CTA. We finally discuss how future detections of afterglows by these observatories can help break the degeneracies in some key physical parameter measurements, and allow to probe efficiently a sub-population of fast-merging binaries.
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Schroeder, Genevieve, Tanmoy Laskar, Wen-fai Fong, Anya E. Nugent, Edo Berger, Ryan Chornock, Kate D. Alexander, et al. "A Radio-selected Population of Dark, Long Gamma-Ray Bursts: Comparison to the Long Gamma-Ray Burst Population and Implications for Host Dust Distributions." Astrophysical Journal 940, no. 1 (November 1, 2022): 53. http://dx.doi.org/10.3847/1538-4357/ac8feb.
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Abstract We present centimeter-band and millimeter-band afterglow observations of five long-duration γ-ray bursts (GRBs; GRB 130131A, 130420B, 130609A, 131229A, 140713A) with dust-obscured optical afterglow emission, known as “dark” GRBs. We detect the radio afterglow of two of the dark GRBs (GRB 130131A and 140713A), along with a tentative detection of a third (GRB 131229A) with the Karl G. Jansky Very Large Array (VLA). Supplemented by three additional VLA-detected dark GRBs from the literature, we present uniform modeling of their broadband afterglows. We derive high line-of-sight dust extinctions of A V,GRB ≈ 2.2– ≳ 10.6 mag. Additionally, we model the host galaxies of the six bursts in our sample, and derive host galaxy dust extinctions of A V,Host ≈ 0.3–4.7 mag. Across all tested γ-ray (fluence and duration) and afterglow properties (energy scales, geometries, and circumburst densities), we find dark GRBs to be representative of more typical unobscured long GRBs, except in fluence, for which observational biases and inconsistent classification may influence the dark GRB distribution. Additionally, we find that A V,GRB is not related to a uniform distribution of dust throughout the host, nor to the extremely local environment of the burst, indicating that a larger-scale patchy dust distribution is the cause of the high line-of-sight extinction. Since radio observations are invaluable to revealing heavily dust-obscured GRBs, we make predictions for the detection of radio emission from host star formation with the next-generation VLA.
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Zhang, H., I. M. Christie, M. Petropoulou, J. M. Rueda-Becerril, and D. Giannios. "Inverse Compton signatures of gamma-ray burst afterglows." Monthly Notices of the Royal Astronomical Society 496, no. 1 (June 5, 2020): 974–86. http://dx.doi.org/10.1093/mnras/staa1583.
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ABSTRACT The afterglow emission from gamma-ray bursts (GRBs) is believed to originate from a relativistic blast wave driven into the circumburst medium. Although the afterglow emission from radio up to X-ray frequencies is thought to originate from synchrotron radiation emitted by relativistic, non-thermal electrons accelerated by the blast wave, the origin of the emission at high energies (HE; ≳GeV) remains uncertain. The recent detection of sub-TeV emission from GRB 190114C by the Major Atmospheric Gamma Imaging Cherenkov Telescopes (MAGIC) raises further debate on what powers the very high energy (VHE; ≳300 GeV) emission. Here, we explore the inverse Compton scenario as a candidate for the HE and VHE emissions, considering two sources of seed photons for scattering: synchrotron photons from the blast wave (synchrotron self-Compton or SSC) and isotropic photon fields external to the blast wave (external Compton). For each case, we compute the multiwavelength afterglow spectra and light curves. We find that SSC will dominate particle cooling and the GeV emission, unless a dense ambient infrared photon field, typical of star-forming regions, is present. Additionally, considering the extragalactic background light attenuation, we discuss the detectability of VHE afterglows by existing and future gamma-ray instruments for a wide range of model parameters. Studying GRB 190114C, we find that its afterglow emission in the Fermi-Large Area Telescope (LAT) band is synchrotron dominated. The late-time Fermi-LAT measurement (i.e. t ∼ 104 s), and the MAGIC observation also set an upper limit on the energy density of a putative external infrared photon field (i.e. ${\lesssim} 3\times 10^{-9}\, {\rm erg\, cm^{-3}}$), making the inverse Compton dominant in the sub-TeV energies.
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GEHRELS, NEIL. "SWIFT OBSERVATIONS OF GAMMA-RAY BURSTS." International Journal of Modern Physics D 17, no. 09 (September 2008): 1311–17. http://dx.doi.org/10.1142/s0218271808012863.
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The Swift mission, launched on 20 November 2004, is detecting ~ 100 gamma-ray bursts (GRBs) each year, and immediately (within ~ 90 s) starting X-ray and UV/optical observations of the afterglow. It has already collected an impressive database including prompt emission to higher sensitivities than BATSE, uniform monitoring of afterglows, and rapid follow-up by other observatories notified through the Gamma-ray bursts Coordinates Network (GCN). The X-ray afterglows have been found to have complex temporal shapes including tails emission from the prompt phase and bright flares. X-ray and optical afterglow detections from short bursts have led to accurate localizations. It is found that they can occur in non-star forming galaxies or regions, whereas long GRBs are strongly concentrated within star forming regions. This is consistent with the NS merger model. Swift has greatly increased the redshift range of GRB detection. The highest redshift GRBs, at z ~ 5-6, are approaching the era of reionization. Ground-based deep optical spectroscopy of high redshift bursts is giving metallicity measurements and other information on the source environment to much greater distance than other techniques. The localization of GRB 060218 in a nearby galaxy, and association with SN 2006aj, added a valuable member to the class of GRBs with detected supernova. The prospects for future progress are excellent given the > 10 year orbital lifetime of the Swift satellite.
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Lin, Haoxiang, and Tomonori Totani. "Detectability of radio afterglows from binary neutron star mergers and implications for fast radio bursts." Monthly Notices of the Royal Astronomical Society 498, no. 2 (September 2, 2020): 2384–90. http://dx.doi.org/10.1093/mnras/staa2418.
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ABSTRACT Binary neutron star (BNS) mergers are one of the proposed origins for both repeating and non-repeating fast radio bursts (FRBs), which associates FRBs with gravitational waves and short gamma-ray bursts (GRBs). In this work, we explore detectability of radio afterglows from BNS mergers and compare it to the observed radio limits on FRB afterglow. We calculate the afterglow flux powered by the two components: a relativistic jet and a slower isotropic ejecta, and quantify the detection probability as a function of the source redshift, observing time, and flux sensitivity. The model parameter distributions inferred from short GRB afterglows are adopted, and viewing angle distributions (uniform spherical, gravitational-wave, on-axis biased) are assumed to reflect different searching scenario. Assuming that FRBs are not strongly beamed, we make comparison to FRBs detected with reported radio limits and find the detection probabilities are 1–10 per cent in general, and hence not a strong constraint on the BNS progenitor model considering the small sample number (<10). In particular for some nearby FRBs (e.g. 180916.J0158+65, 190608), we find a high chance of detection (>20 per cent at 10 μJy sensitivity) for the isotropic component that would peak around ∼1–10 yr after the merger. Therefore, a long-term radio monitoring of persistent radio emission for these objects is important.
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Yoshimura, Fumitaka, Mika Ishizaki, Fumihiro Wakai, Masahiko Hara, Osamu Odawara, and Hiroyuki Wada. "Optical Properties of Afterglow Nanoparticles : , Capped with Polyethylene Glycol." Advances in Optical Technologies 2012 (July 14, 2012): 1–6. http://dx.doi.org/10.1155/2012/814745.
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The optical properties of afterglow nanoparticles were successfully improved by the addition of polyethylene glycol (PEG) to an afterglow colloidal solution. Afterglow nanoparticles—: , —were prepared by laser ablation in liquid. The quantum yields and the decay curves were measured by a fluorescence spectrophotometer. An increase in the amount of PEG added to the solution increased the quantum yield of the nanoparticles and improved the afterglow property in the initial portion of the decay curve. However, the afterglow property did not change after a substantial amount of time had passed. The afterglow nanoparticles were capped with PEG molecules, and surface defects of the nanoparticles were passivated, which decreased the optical properties.
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Shi, Huifang, and Zhongfu An. "Ultraviolet afterglow." Nature Photonics 13, no. 2 (January 24, 2019): 74–75. http://dx.doi.org/10.1038/s41566-018-0345-7.
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Cowen, Ron. "Cosmic Afterglow." Science News 163, no. 12 (March 22, 2003): 180. http://dx.doi.org/10.2307/4014218.
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Zhang, B. "GRB afterglow." EAS Publications Series 61 (2013): 285–93. http://dx.doi.org/10.1051/eas/1361046.
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Zhong, Rui Xia, Zi Ran Liu, Qing Qiu, Jian Quan Qi, and Xiao Yan Zhang. "Influence on Red Long-Lasting Phosphorescence due to Different Doping Concentrations of ZnGa2O4:Cr3+." Applied Mechanics and Materials 423-426 (September 2013): 411–14. http://dx.doi.org/10.4028/www.scientific.net/amm.423-426.411.
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High temperature solid state reaction has been used to prepare the new red long-lasting phosphorescence (LLP) material ZnGa2O4:Cr3+ with different doping concentration. The afterglow properties of the samples have been investigated. Our study has shown that ZnGa2O4 samples without Cr3+ doping have blue-green afterglow. While the blue-green afterglow has disappeared and the red long-lasting phosphorescence according to the Cr3+ luminescence center covering 650 nm-750 nm has been observed when Cr3+ has been doped. In terms of brightness and decay time of the afterglow, the red afterglow and the blue-green afterglow have been entirely different. In this article the influence on LLP due to different doping concentrations of ZnGa2O4:Cr3+ has been discussed and the possible LLP mechanism has been proposed.
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Zhai, Bao-Gai, and Yuan-Ming Huang. "Green Afterglow of Undoped SrAl2O4." Nanomaterials 11, no. 9 (September 9, 2021): 2331. http://dx.doi.org/10.3390/nano11092331.
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Undoped SrAl2O4 nanocrystals were obtained via solution combustion using urea as fuel. The afterglow properties of undoped SrAl2O4 were investigated. Green afterglow from undoped SrAl2O4 is visible to the human eye when the 325 nm irradiation of a helium–cadmium laser (13 mW) is ceased. The afterglow spectrum of undoped SrAl2O4 is peaked at about 520 nm. From the peak temperature (321 K) of the broad thermoluminescence glow curve, the trap depth of trap levels in undoped SrAl2O4 is estimated to be 0.642 eV using Urbach’s formula. Based on first-principles density functional calculations, the bandstructures and densities of states are derived for oxygen-deficient SrAl2O4 and strontium-deficient SrAl2O4, respectively. Our results demonstrate that the green afterglow of undoped SrAl2O4 originates from the midgap states introduced by oxygen and strontium vacancies. The observation of green afterglow from undoped SrAl2O4 helps in gaining new insight in exploring the afterglow mechanisms of SrAl2O4-based afterglow materials.
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Tian, Xiao, Ying Qin, Mei Du, Shuang-Xi Yi, and Yan-Ke Tang. "Constraining the Circumburst Medium of Gamma-Ray Bursts with X-Ray Afterglows." Astrophysical Journal 925, no. 1 (January 1, 2022): 54. http://dx.doi.org/10.3847/1538-4357/ac3de4.
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Abstract Long gamma-ray bursts (GRBs) are considered to originate from core collapse of massive stars. It is believed that the afterglow property is determined by the density of the material in the surrounding interstellar medium (ISM). Therefore, the circumburst density can be used to distinguish between an interstellar wind, n(R) ∝ R −k , and a constant-density medium (ISM), n ( R ) = const . Previous studies with different afterglow samples show that the circumburst medium of GRBs is neither simply supported by an interstellar wind nor completely favored by an ISM. In this work, our new sample consists of 39 GRBs with smoothly onset bump-like features in early X-ray afterglows, in which 20 GRBs have the redshift measurements. By using a smooth broken power-law function to fit the bumps of X-ray light curves, we derive the FWHM as the feature width (ω), as well as the rise and decay timescales of the bumps (T r and T d ). The correlations between the timescales of X-ray bumps are similar to those found previously in the optical afterglows. Based on the fireball forward shock model of the thin shell case, we obtain the distribution of the electron spectral index p and further constrain the medium density distribution index k. The new inferred k is found to be concentrated at 1.0, with a range from 0.2 to 1.8. This finding is consistent with previous studies. The conclusion of our detailed investigation for X-ray afterglows suggests that the ambient medium of the selected GRBs is not homogeneous, i.e., neither ISM nor the typical interstellar wind.
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Zhou, Qi-Qi, Shuang-Xi Yi, Xiao-Li Huang, Shu-Qing Zhong, Yuan-Chuan Zou, Qing-Wen Tang, and Zhi-Fu Chen. "GRB 161017A, the circumburst environment is an intermediate regime between the homogeneous interstellar medium and wind-type medium." International Journal of Modern Physics D 29, no. 06 (April 2020): 2050043. http://dx.doi.org/10.1142/s0218271820500431.
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We investigate the multi-band properties of the GRB 161017A with [Formula: see text], which was detected by Swift and Fermi satellites, and other instruments. The optical and X-ray afterglows were all detected at early times after the prompt emission. The optical light curve shows a very bright onset peak at about 100 s for 13 mag of [Formula: see text]-band, while the X-ray light curve occurs several flares at the beginning. We investigate the origin of X-ray and optical afterglows by analyzing the optical and X-ray data. Considering the smooth onset bump in the early time of the optical band and the erratic pulses for the X-ray lightcurve, we suppose that the early optical afterglow may be produced by the external shock, while the early time of X-ray light curve is dominated by flares. Therefore, GRB optical afterglows with smooth onset bump features at early time are possibly produced by external — forward shock (FS). According to the fireball external-model, the temporal slopes of the onset bumps are determined by both the medium density profile and the electron spectral index. Therefore, the afterglow onset bumps would be an ideal probe to study the properties of the fireball and the circumburst medium. The density profile has a slope of [Formula: see text], which suggests that the circumburst environment of the GRB 161017A would be an intermediate regime that are between the homogeneous interstellar medium (ISM) and wind-type medium. In addition, the optical light curve of the GRB 161017A exhibits a plateau feature and rebrightening after the onset bump, which may be related to the long-acting central engine of GRBs.
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Peng, Chenxi, Xue Chen, Meiling Chen, Shenci Lu, Yu Wang, Suli Wu, Xiaowang Liu, and Wei Huang. "Afterglow Carbon Dots: From Fundamentals to Applications." Research 2021 (February 9, 2021): 1–27. http://dx.doi.org/10.34133/2021/6098925.
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The ability of carbon dots (CDs) to emit afterglow emission in addition to fluorescence in response to UV-to-visible excitation allows them to be a new class of luminescent materials. When compared with traditional organic or inorganic afterglow materials, CDs have a set of advantages, including small size, ease of synthesis, and absence of highly toxic metal ions. In addition, high dependence of their afterglow color output on temperature, excitation wavelength, and aggregation degrees adds remarkable flexibility in the creation of multimode luminescence of CDs without the need for changing their intrinsic attributes. These characteristics make CDs particularly attractive in the fields of sensing, anticounterfeiting, and data encryption. In this review, we first describe the general attributes of afterglow CDs and their fundamental afterglow mechanism. We then highlight recent strategic advances in the generation or activation of the afterglow luminescence of CDs. Considerable emphasis is placed on the summarization of their emergent afterglow properties in response to external stimulation. We further highlight the emerging applications of afterglow CDs on the basis of their unique optical features and present the key challenges needed to be addressed before the realization of their full practical utility.
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He, Xin-Bo, Pak-Hin Thomas Tam, Guang-Bo Long, Partha Sarathi Pal, Yong Zhang, and Li-Jun Zhang. "Searching for an additional high-energy component in Fermi-LAT GRB afterglows." Astronomy & Astrophysics 657 (January 2022): A111. http://dx.doi.org/10.1051/0004-6361/202040039.
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Context. The very high-energy (VHE; ≥100 GeV) component from at least two gamma-ray bursts (GRBs), that is, GRB 180720B and GRB 190114C, has been detected in the afterglow phase. It is widely discussed that the GeV to TeV emission originated from a synchrotron self-Compton (SSC) process. The VHE component may cause an upturn at the high-energy spectral ends in the Fermi-Large Area Telescope (Fermi-LAT) observing band. Aims. We aim to find out whether an additional high-energy component commonly exists in the afterglows of Fermi-LAT GRBs. This study will help us to better understand how common it is for a GRB afterglow detected by Fermi-LAT to involve a VHE component. Methods. First, we selected the GRBs that emit ≥10 GeV photons. The ≥10 GeV photons can be considered as a plausible proxy for a VHE component. We systematically analyzed 199 GRBs detected by Fermi-LAT from 2008–2019. If an additional high-energy component exists in the afterglows of Fermi-LAT GRBs, the best-fit spectral model could be a broken power law (BPL) model with an upturn above a break energy. We compared the afterglow spectra using power-law (PL) and BPL representations. Results. Out of the 30 GRBs with ≥10 GeV photons that arrived after T90 (the time duration when 90% of the prompt emission was detected), 25 GRBs are tentatively or significantly detected at 0.1–200 GeV after 2 × T90. The spectrum of GRB 131231A shows an upturn above an energy break of 1.6 ± 0.8 GeV, supporting the BPL model. For GRB 131231A, we performed a modeling of its X-ray and γ-ray spectra and found that the SSC model can explain the upturn with acceptable parameter values. In the cases of GRB 190114C, GRB 171210A, GRB 150902A, GRB 130907A, GRB 130427A, and GRB 090902B, the improvement of the BPL fit compared to the PL fit is tentative or marginal. Conclusions. There is no conclusive evidence that an additional higher energy component commonly exists in Fermi-LAT GRB afterglows, except for the group of Fermi-LAT GRBs mentioned above. Such an additional high-energy component may be explained by the SSC mechanism. Current and future VHE observations will provide important constraints on the issue.
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Xie, Gaozhan, Jiangchao Wang, Xudong Xue, Hui Li, Ningning Guo, Huanhuan Li, Danbei Wang, et al. "Achieving low driving voltage and high-efficiency afterglow organic light-emitting diodes through host–guest doping." Applied Physics Reviews 9, no. 3 (September 2022): 031410. http://dx.doi.org/10.1063/5.0093704.
Full textAbstract:
Achieving afterglow organic light-emitting diodes (OLEDs) that exhibit the organic ultralong room temperature phosphorescence (OURTP) emission after switching off the applied voltage is highly attractive. However, it is difficult to obtain appropriate emitting layers that are of excellent charge transport ability and OURTP properties simultaneously to fabricate highly efficient afterglow OLEDs. Here, we report an easy but effective strategy to construct afterglow OLEDs via host–guest doping by adopting the excellent carrier transporting materials as rigid host and the commendable OURTP emitters as guest. The resultant green afterglow OLEDs exhibit the state-of-the-art maximum external quantum efficiency, luminance, and OURTP lifetimes of up to 1.47%, 743 cd m−2, and 356 ms, respectively, with the low turn-voltage of 4.4 V. Due to the inherent stable afterglow properties and outstanding carrier transport ability of the emitting layer, the OLEDs show admirable afterglow emission stability with the intensity and lifetimes keeping almost the same for more than ten repeated voltage pulses. The current work paves the way to develop highly efficient and stable afterglow OLEDs by host–guest doping.
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Lamb, Gavin P., Joseph J. Fernández, Fergus Hayes, Albert K. H. Kong, En-Tzu Lin, Nial R. Tanvir, Martin Hendry, Ik Siong Heng, Surojit Saha, and John Veitch. "Inclination Estimates from Off-Axis GRB Afterglow Modelling." Universe 7, no. 9 (September 5, 2021): 329. http://dx.doi.org/10.3390/universe7090329.
Full textAbstract:
For gravitational wave (GW) detected neutron star mergers, one of the leading candidates for electromagnetic (EM) counterparts is the afterglow from an ultra-relativistic jet. Where this afterglow is observed, it will likely be viewed off-axis, such as the afterglow following GW170817/GRB 170817A. The temporal behaviour of an off-axis observed GRB afterglow can be used to reveal the lateral jet structure, and statistical model fits can put constraints on the various model free-parameters. Amongst these parameters is the inclination of the system to the line of sight. Along with the GW detection, the afterglow modelling provides the best constraint on the inclination to the line-of-sight and can improve the estimates of cosmological parameters, for example, the Hubble constant, from GW-EM events. However, modelling of the afterglow depends on the assumed jet structure and—often overlooked—the effects of lateral spreading. Here we show how the inclusion of lateral spreading in the afterglow models can affect the estimated inclination of GW-EM events.
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Wang, X. Y., Z. G. Dai, and T. Lu. "Possible Geometries for Afterglow of GRB990705." Symposium - International Astronomical Union 214 (2003): 341–42. http://dx.doi.org/10.1017/s0074180900194719.
Full textAbstract:
We investigate whether the circum-burst environment constrained by the absorption feature of GRB990705 could be consistent with the observed H-band afterglow. Two possible geometries of the afterglow-emitting regions are suggested: 1) afterglow emission produced by the impact of the fireball on the surrounding torus; 2)afterglow emission produced in the dense circum-burst medium inside the torus. In case 1), the faster decay at later time is attributed to the disappearance of the shock due to the counter-pressure in the hot torus illuminated by the burst and afterglow photons. For case 2), the circum-burst medium density is found to be very high (n ≳ 104 − 105cm−3).
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van Eerten, Hendrik. "GRB 170817A and the long-term aftermath of neutron star mergers." Proceedings of the International Astronomical Union 16, S363 (June 2020): 105–16. http://dx.doi.org/10.1017/s1743921322001971.
Full textAbstract:
AbstractGW170817/GRB 170817A has had a huge impact on our understanding of gamma-ray burst (GRB) afterglows, and has prompted a huge sustained effort at modeling the details of the geometry and emission from GRB jets. While no additional electro-magnetic counterparts have been detected to gravitational wave emission from neutron star mergers so far, it is certainly reasonable to expect further detections in the future. Whether these will be very similar in nature to GRB 170817A or instead will provide us with samplings of afterglow model parameters across a wide parameter space remains an open question. In this presentation I will survey some of the work done by the various active groups worldwide in theoretical modeling and understanding afterglows post 170817A.