Journal articles on the topic 'Explosive transients'
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1
Oguri, Masamune. "Strong gravitational lensing of explosive transients." Reports on Progress in Physics 82, no. 12 (November 7, 2019): 126901. http://dx.doi.org/10.1088/1361-6633/ab4fc5.
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Bersier, David, Mike Bode, Shiho Kobayashi, Carole Mundell, and Iain Steele. "Explosive transients: a time-variable sky." Astronomy & Geophysics 52, no. 1 (January 19, 2011): 1.10–1.14. http://dx.doi.org/10.1111/j.1468-4004.2011.52110.x.
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Vanderspek, Roland, and George R. Richer. "ETC Observations of the Gamma-ray Burst GRB 941014." International Astronomical Union Colloquium 151 (1995): 385–88. http://dx.doi.org/10.1017/s0252921100035405.
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AbstractThe Explosive Transient Camera (ETC) is a dedicated wide-field sky monitor for short-duration optical transients. The ETC operates completely automatically, searching for transients in the night sky without the need for a human observer on site. Data products from the ETC include data from any transients detected, as well as CCD images of the fields-of-view observed. We report here the imaging by the ETC of the 2.5σ error region of GRB 941014 90 seconds after the end of the burst.
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Justham, S. "Forming the Progenitors of Explosive Stellar Transients." Proceedings of the International Astronomical Union 14, S339 (November 2017): 33–38. http://dx.doi.org/10.1017/s1743921318002168.
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AbstractExplosive stellar transients arise from diverse situations, including deaths of massive stars, a variety of thermonuclear outbursts, and compact-object mergers. Stellar interactions are heavily implicated in explaining the observed populations of events, and not only those where binarity is obviously involved. Relationships between these classes probably help to elucidate our understanding; for example; the production of double neutron-star mergers from field binaries is thought to be heavily biased towards routes involving stripped core-collapse supernovæ. As we gain an ever more synoptic view of the changing sky, theorists should be mindful of developing an ability to take robust quantitative advantage of the available population information to help constrain the physics. This is complementary to aiming for deep understanding of individual events.
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Guépin, Claire, and Kumiko Kotera. "Can we observe neutrino flares in coincidence with explosive transients?" Astronomy & Astrophysics 603 (July 2017): A76. http://dx.doi.org/10.1051/0004-6361/201630326.
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The new generation of powerful instruments is reaching sensitivities and temporal resolutions that will allow multi-messenger astronomy of explosive transient phenomena, with high-energy neutrinos as a central figure. We derive general criteria for the detectability of neutrinos from powerful transient sources for given instrument sensitivities. In practice, we provide the minimum photon flux necessary for neutrino detection based on two main observables: the bolometric luminosity and the time variability of the emission. This limit can be compared to the observations in specified wavelengths in order to target the most promising sources for follow-ups. Our criteria can also help distinguishing false associations of neutrino events with a flaring source. We find that relativistic transient sources such as high- and low-luminosity gamma-ray bursts (GRBs), blazar flares, tidal disruption events, and magnetar flares could be observed with IceCube, as they have a good chance to occur within a detectable distance. Of the nonrelativistic transient sources, only luminous supernovae appear as promising candidates. We caution that our criterion should not be directly applied to low-luminosity GRBs and type Ibc supernovae, as these objects could have hosted a choked GRB, leading to neutrino emission without a relevant counterpart radiation. We treat a set of concrete examples and show that several transients, some of which are being monitored by IceCube, are far from meeting the criterion for detectability (e.g., Crab flares or Swift J1644+57).
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Muthukrishna, Daniel, Gautham Narayan, Kaisey S. Mandel, Rahul Biswas, and Renée Hložek. "RAPID: Early Classification of Explosive Transients Using Deep Learning." Publications of the Astronomical Society of the Pacific 131, no. 1005 (September 30, 2019): 118002. http://dx.doi.org/10.1088/1538-3873/ab1609.
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Leybourne, Allen E. "Frequency‐averaged, mean‐squared coherence of simulated underwater explosive transients." Journal of the Acoustical Society of America 85, S1 (May 1989): S126—S127. http://dx.doi.org/10.1121/1.2026713.
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Wyrzykowski, Łukasz, Simon T. Hodgkin, Nadejda Blagorodnova, and Vasily Belokurov. "The Explosive Universe with Gaia." Proceedings of the International Astronomical Union 9, S298 (May 2013): 446. http://dx.doi.org/10.1017/s1743921313007114.
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AbstractThe Gaia mission will observe the entire sky for 5 years providing ultra-precise astrometric, photometric and spectroscopic measurements for a billion stars in the Galaxy. Hence, naturally, Gaia becomes an all-sky multi-epoch photometric survey, which will monitor and detect variability with millimag precision as well as new transient sources such as supernovae, novae, microlensing events, tidal disruption events, asteroids, among others.Gaia data-flow allows for quick detections of anomalies within 24-48h after the observation. Such near-real-time survey will be able to detect about 6000 supernovae brighter than 19 mag up to redshifts of Z 0.15. The on-board low-resolution (R 100) spectrograph will allow for early and robust classification of transients and minimise the false-alert rate, even providing the estimates on redshift for supernovae. Gaia will also offer a unique possibility for detecting astrometric shifts in microlensing events, which, combined with Gaia's and ground-based photometry, will provide unique mass measurements of lenses, constrains on the dark matter content in the Milky Way and possible detections of free floating black holes.Alerts from Gaia will be publicly available soon after the detection is verified and tested. First alerts are expected early in 2014 and those will be used for ground-based verification. All facilities are invited to join the verification and the follow-up effort. Alerts will be published on a web page, via Skyalert.org and via emailing list. Each alert will contain coordinates, Gaia light curve and low-resolution spectra, classification and cross-matching results.More information on the Gaia Science Alerts can be found here: http://www.ast.cam.ac.uk/ioa/wikis/gsawgwiki/The full version of the poster is available here: http://www.ast.cam.ac.uk/ioa/wikis/gsawgwiki/images/1/13/GaiaAlertsPosterIAUS298.pdf
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Zenati, Yossef, Alexey Bobrick, and Hagai B. Perets. "Faint rapid red transients from neutron star–CO white dwarf mergers." Monthly Notices of the Royal Astronomical Society 493, no. 3 (February 20, 2020): 3956–65. http://dx.doi.org/10.1093/mnras/staa507.
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ABSTRACT Mergers of neutron stars (NS) and white dwarfs (WD) may give rise to observable explosive transient events. We use 3D hydrodynamical (smoothed particle hydrodynamics – SPH) simulations and 2D hydrodynamical–thermonuclear simulations (using the flash adaptive mesh refinement code) to model the disruption of CO-WDs by NSs, which produce faint transient events. We post-process the simulations using a large nuclear network and make use of the SuperNu radiation transfer code to predict the observational signatures and detailed properties of these transients. We calculate the light curves and spectra for five models of NS–CO-WD mergers. The small yields of 56Ni (few $\times 10^{-3}\, {\rm M_{\odot }}$) result in faint, rapidly evolving reddened transients (RRTs) with B(R) peak magnitudes of at most ∼−12 (−13) to ∼−13 (−15), much shorter and fainter than both regular and faint/peculiar Type Ia supernovae. These transients are likely to be accompanied by several months long, 1–2 mag dimmer red/infrared afterglows. We show that the spectra of RRTs share some similarities with rapidly evolving transients such as SN 2010X, although RRTs are significantly fainter, especially in the I/R bands, and show far stronger Si lines. We estimate that the upcoming Large Synoptic Survey Telescope could detect RRTs at a rate of up to ∼10–70 yr−1 through observations in the R/I bands. The qualitative agreement between the SPH and flash approaches supports the earlier hydrodynamical studies of these systems.
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Gress, O. A., V. M. Lipunov, D. Dornic, E. S. Gorbovskoy, V. G. Kornilov, N. V. Tyurina, P. V. Balanutsa, A. S. Kuznetsov, V. V. Vladimirov, and D. A. Kuvshinov. "MASTER INVESTIGATION OF ANTARES AND ICECUBE ALERTS." Revista Mexicana de Astronomía y Astrofísica Serie de Conferencias 51 (April 13, 2019): 89–95. http://dx.doi.org/10.22201/ia.14052059p.2019.51.15.
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This paper presents the first investigation results of possible coincidences of optical transients in the MASTER global robotic telescope net database with the localization regions of VHE and UHE neutrino alert events from ANTARES and IceCube observatories. MASTER is the first robotic telescopic system in Russia, dedicated to optical observation and registration of the most energetic and fastest explosive processes in the Universe. The goal is a deeper and more thorough study of space and time coincidences of the MASTER optical transients and high energy neutrinos.
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Morgan, R., K. Bechtol, R. Kessler, M. Sako, K. Herner, Z. Doctor, D. Scolnic, et al. "A DECam Search for Explosive Optical Transients Associated with IceCube Neutrino Alerts." Astrophysical Journal 883, no. 2 (September 26, 2019): 125. http://dx.doi.org/10.3847/1538-4357/ab3a45.
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Bianco, Federica B., Maria R. Drout, Melissa L. Graham, Tyler A. Pritchard, Rahul Biswas, Gautham Narayan, Igor Andreoni, Philip S. Cowperthwaite, and Tiago Ribeiro. "Presto-Color: A Photometric Survey Cadence for Explosive Physics and Fast Transients." Publications of the Astronomical Society of the Pacific 131, no. 1000 (April 25, 2019): 068002. http://dx.doi.org/10.1088/1538-3873/ab121a.
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Wiseman, P., M. Pursiainen, M. Childress, E. Swann, M. Smith, L. Galbany, C. Lidman, et al. "The host galaxies of 106 rapidly evolving transients discovered by the Dark Energy Survey." Monthly Notices of the Royal Astronomical Society 498, no. 2 (August 17, 2020): 2575–93. http://dx.doi.org/10.1093/mnras/staa2474.
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ABSTRACT Rapidly evolving transients (RETs), also termed fast blue optical transients, are a recently discovered group of astrophysical events that display rapid luminosity evolution. RETs typically rise to peak in less than 10 d and fade within 30, a time-scale unlikely to be compatible with the decay of Nickel-56 that drives conventional supernovae (SNe). Their peak luminosity spans a range of −15 < Mg < −22.5, with some events observed at redshifts greater than 1. Their evolution on fast time-scales has hindered high-quality follow-up observations, and thus their origin and explosion/emission mechanism remains unexplained. In this paper, we present the largest sample of RETs to date, comprising 106 objects discovered by the Dark Energy Survey, and perform the most comprehensive analysis of RET host galaxies. Using deep-stacked photometry and emission lines from OzDES spectroscopy, we derive stellar masses and star formation rates (SFRs) for 49 host galaxies, and metallicities ([O/H]) for 37. We find that RETs explode exclusively in star-forming galaxies and are thus likely associated with massive stars. Comparing RET hosts to samples of host galaxies of other explosive transients as well as field galaxies, we find that RETs prefer galaxies with high specific SFRs (〈log (sSFR)〉 ∼ −9.6), indicating a link to young stellar populations, similar to stripped-envelope SNe. RET hosts appear to show a lack of chemical enrichment, their metallicities akin to long-duration gamma-ray bursts and superluminous SN host galaxies (〈12 + log (O/H)〉 ∼ 9.4). There are no clear relationships between mass or SFR of the host galaxies and the peak magnitudes or decline rates of the transients themselves.
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KAMBLE, ATISH, and DAVID L. A. KAPLAN. "ELECTROMAGNETIC COUNTERPARTS OF GRAVITATIONAL WAVE SOURCES: MERGERS OF COMPACT OBJECTS." International Journal of Modern Physics D 22, no. 01 (January 2013): 1341011. http://dx.doi.org/10.1142/s0218271813410113.
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Mergers of compact objects are considered prime sources of gravitational waves (GW) and will soon be targets of GW observatories such as the Advanced-LIGO and VIRGO. Finding electromagnetic counterparts of these GW sources will be important to understand their nature. We discuss possible electromagnetic signatures of the mergers. We show that the BH–BH mergers could have luminosities which exceed Eddington luminosity from unity to several orders of magnitude depending on the masses of the merging BHs. As a result these mergers could be explosive, release up to 1051 erg of energy and shine as radio transients. At any given time we expect about a few such transients in the sky at GHz frequencies, which could be detected to be about 300 Mpc. It has also been argued that these radio transients would look alike radio supernovae with comparable detection rates. Multi-band follow-up could, however, distinguish between the mergers and supernovae.
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De Decker, Y., and F. Baras. "Bistability and explosive transients in surface reactions: the role of fluctuations and spatial correlations." European Physical Journal B 78, no. 2 (November 2010): 173–86. http://dx.doi.org/10.1140/epjb/e2010-10333-4.
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Pursiainen, M., C. P. Gutiérrez, P. Wiseman, M. Childress, M. Smith, C. Frohmaier, C. Angus, et al. "The mystery of photometric twins DES17X1boj and DES16E2bjy." Monthly Notices of the Royal Astronomical Society 494, no. 4 (April 13, 2020): 5576–89. http://dx.doi.org/10.1093/mnras/staa995.
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ABSTRACT We present an analysis of DES17X1boj and DES16E2bjy, two peculiar transients discovered by the Dark Energy Survey (DES). They exhibit nearly identical double-peaked light curves that reach very different maximum luminosities (Mr = −15.4 and −17.9, respectively). The light-curve evolution of these events is highly atypical and has not been reported before. The transients are found in different host environments: DES17X1boj was found near the nucleus of a spiral galaxy, while DES16E2bjy is located in the outskirts of a passive red galaxy. Early photometric data are well fitted with a blackbody and the resulting moderate photospheric expansion velocities (1800 km s−1 for DES17X1boj and 4800 km s−1 for DES16E2bjy) suggest an explosive or eruptive origin. Additionally, a feature identified as high-velocity Ca ii absorption ($v$ ≈ 9400 km s−1) in the near-peak spectrum of DES17X1boj may imply that it is a supernova. While similar light-curve evolution suggests a similar physical origin for these two transients, we are not able to identify or characterize the progenitors.
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Rozner, Mor, and Hagai B. Perets. "Binary Evolution, Gravitational-wave Mergers, and Explosive Transients in Multiple-population Gas-enriched Globular Clusters." Astrophysical Journal 931, no. 2 (June 1, 2022): 149. http://dx.doi.org/10.3847/1538-4357/ac6d55.
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Abstract Most globular clusters (GCs) show evidence for multiple stellar populations, suggesting the occurrence of several distinct star formation episodes. The large fraction of second population (2P) stars observed requires a very large 2P gaseous mass to have accumulated in the cluster core to form these stars. Hence, the first population of stars (1P) in the cluster core has had to become embedded in 2P gas, just prior to the formation of later populations. Here we explore the evolution of binaries in ambient 2P gaseous media of multiple-population GCs. We mostly focus on black hole binaries and follow their evolution as they evolve from wide binaries toward short periods through interaction with ambient gas, followed by gravitational-wave (GW) dominated inspiral and merger. We show that this novel GW merger channel could provide a major contribution to the production of GW sources. We consider various assumptions and initial conditions and calculate the resulting gas-mediated change in the population of binaries and the expected merger rates due to gas-catalyzed GW inspirals. For plausible conditions and assumptions, we find an expected GW merger rate observable by aLIGO of the order of up to a few tens of Gpc−3 yr−1 and an overall range for our various models of 0.08–25.51 Gpc−3 yr−1. Finally, our results suggest that the conditions and binary properties in the early stage of GCs could be critically affected by gas interactions and may require a major revision in the current modeling of the evolution of GCs.
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Rozner, Mor, and Hagai B. Perets. "Binary Evolution, Gravitational-wave Mergers, and Explosive Transients in Multiple-population Gas-enriched Globular Clusters." Astrophysical Journal 931, no. 2 (June 1, 2022): 149. http://dx.doi.org/10.3847/1538-4357/ac6d55.
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Abstract Most globular clusters (GCs) show evidence for multiple stellar populations, suggesting the occurrence of several distinct star formation episodes. The large fraction of second population (2P) stars observed requires a very large 2P gaseous mass to have accumulated in the cluster core to form these stars. Hence, the first population of stars (1P) in the cluster core has had to become embedded in 2P gas, just prior to the formation of later populations. Here we explore the evolution of binaries in ambient 2P gaseous media of multiple-population GCs. We mostly focus on black hole binaries and follow their evolution as they evolve from wide binaries toward short periods through interaction with ambient gas, followed by gravitational-wave (GW) dominated inspiral and merger. We show that this novel GW merger channel could provide a major contribution to the production of GW sources. We consider various assumptions and initial conditions and calculate the resulting gas-mediated change in the population of binaries and the expected merger rates due to gas-catalyzed GW inspirals. For plausible conditions and assumptions, we find an expected GW merger rate observable by aLIGO of the order of up to a few tens of Gpc−3 yr−1 and an overall range for our various models of 0.08–25.51 Gpc−3 yr−1. Finally, our results suggest that the conditions and binary properties in the early stage of GCs could be critically affected by gas interactions and may require a major revision in the current modeling of the evolution of GCs.
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Leybourne, Allen E. "An extension of underwater explosive models to include the high frequency transients following pulse maxima." Mathematical and Computer Modelling 14 (1990): 771–75. http://dx.doi.org/10.1016/0895-7177(90)90286-v.
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Tanikawa, Ataru, Yushi Sato, Ken’ichi Nomoto, Keiichi Maeda, Naohito Nakasato, and Izumi Hachisu. "Explosive nucleosynthesis in tidal disruption events of massive white dwarfs, and their debris." Proceedings of the International Astronomical Union 12, S324 (September 2016): 136–37. http://dx.doi.org/10.1017/s1743921317001491.
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AbstractWe perform SPH simulations coupled with nuclear reactions to follow tidal disruption events (TDEs) of white dwarfs (WDs) by intermediate mass black holes (IMBHs). We consider an oxygen-neon-magnesium (ONeMg) WD with 1.2M⊙ as well as a helium (He) WD with 0.3M⊙, and a carbon-oxygen (CO) WD with 0.6M⊙. Our WD models have different numbers of SPH particles, N, up to a few 10 million. We find that nucleosynthesis does not converge against N even for N > 107. For all the WDs, the amount of radioactive nuclei, such as 56Ni, decreases with increasing N. Nuclear reactions might be extinguished for infinitely large N. Our results show that these kinds of TDEs, if solely powered by radioactive decays, are much dimmer optical transients similar to Type Ia supernovae as previously suggested.
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Isern, J., R. Canal, D. García, M. Hernanz, and J. Labay. "Gravitational Collapse of Mass-Accreting White Dwarfs." International Astronomical Union Colloquium 114 (1989): 88–91. http://dx.doi.org/10.1017/s0252921100099346.
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Massive star (M ≥ 10 M ) core collapse is the standard mechanism for neutron star formation (see Brown 1988 for a recent review). It has long been realized (see, for instance, van den Heuvel 1988, and references therein) that the neutron stars found in different types of binary systems cannot come from such a standard mechanism. Those systems include wide binary radio pulsars, millisecond pulsars (not in wide binaries), galactic bulge X–ray sources (including QPO’s), type I X–ray burst sources and X–ray transients, andγ–ray sources. Formation of those neutron stars is now widely attributed to the gravitational collapse of a white dwarf, growing above Chandrasekhar’s limit by mass accretion from the current neutron star’s companion in the binary system (Canal and Schatzman 1976; Canal and Isern 1979; Canal, Isern, and Labay 1980; Miyaji et al. 1980). Mass growth up to dynamical instability means that both explosive ejection of the accreted layers and explosive disruption of the whole star must be avoided. The former is associated with the nova phenomenon. The latter, with the occurrence of type I supernovae.
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Guépin, Claire. "Signatures of secondary acceleration in neutrino flares." Astronomy & Astrophysics 641 (September 2020): A29. http://dx.doi.org/10.1051/0004-6361/202037576.
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High-energy neutrino flares are interesting prospective counterparts to photon flares since their detection would guarantee the presence of accelerated hadrons within a source, in addition to providing precious information about cosmic-ray acceleration and interactions, thus impacting the subsequent modeling of non-thermal emissions in explosive transients. In these sources, photomeson production can be efficient, producing a large amount of secondary particles, such as charged pions and muons, that decay and produce high-energy neutrinos. Before their decay, secondary particles can experience energy losses and acceleration, which can impact high-energy neutrino spectra and thus affect their detectability. In this work, we focus on the impact of secondary acceleration. We consider a one zone model, characterized mainly by a variability timescale tvar, luminosity Lbol, and bulk Lorentz factor Γ. The mean magnetic field B is deduced from these parameters. The photon field is modeled by a broken power-law. This generic model allows us to systematically evaluate the maximum energy of high-energy neutrinos in the parameter space of explosive transients and shows that it could be strongly affected by secondary acceleration for a large number of source categories. In order to determine the impact of secondary acceleration on the high-energy neutrino spectrum and, in particular, on its peak energy and flux, we complement these estimates with several case studies. We show that secondary acceleration can increase the maximum neutrino flux and produce a secondary peak at the maximum energy in the case of efficient acceleration. Secondary acceleration could, therefore, enhance the detectability of very-high-energy neutrinos that would be the target of next generation neutrino detectors, such as KM3NeT, IceCube-Gen2, POEMMA, or GRAND.
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Peter, H., Y. M. Huang, L. P. Chitta, and P. R. Young. "Plasmoid-mediated reconnection in solar UV bursts." Astronomy & Astrophysics 628 (July 25, 2019): A8. http://dx.doi.org/10.1051/0004-6361/201935820.
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Context. Ultraviolet bursts are transients in the solar atmosphere with an increased impulsive emission in the extreme UV lasting for one to several tens of minutes. They often show spectral profiles indicative of a bi-directional outflow in response to magnetic reconnection. Aims. To understand UV bursts, we study how motions of magnetic elements at the surface can drive the self-consistent formation of a current sheet resulting in plasmoid-mediated reconnection. In particular, we want to study the role of the height of the reconnection in the atmosphere. Methods. We conducted numerical experiments solving the 2D magnetohydrodynamic equations from the solar surface to the upper atmosphere. Motivated by observations, we drove a small magnetic patch embedded in a larger system of magnetic field of opposite polarity. This type of configuration creates an X-type neutral point in the initial potential field. The models are characterized by the (average) plasma-β at the height of this X point. Results. The driving at the surface stretches the X-point into a thin current sheet, where plasmoids appear, accelerating the reconnection, and a bi-directional jet forms. This is consistent with what is expected for UV bursts or explosive events, and we provide a self-consistent model of the formation of the reconnection region in such events. The gravitational stratification gives a natural explanation for why explosive events are restricted to a temperature range around a few 0.1 MK, and the presence of plasmoids in the reconnection process provides an understanding of the observed variability during the transient events on a timescale of minutes. Conclusions. Our numerical experiments provide a comprehensive understanding of UV bursts and explosive events, in particular of how the atmospheric response changes if the reconnection happens at different plasma-β, that is, at different heights in the atmosphere. This analysis also gives new insight into how UV bursts might be related to the photospheric Ellerman bombs.
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Joshi, Rishabh, and Associate Professor. "Transient Effect of Blast Loads on RCC Building." Asian Review of Civil Engineering 8, no. 1 (May 5, 2019): 9–19. http://dx.doi.org/10.51983/tarce-2019.8.1.2286.
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The increase in the number of terrorist attacks has shown that the effect of blast loading on structures is a serious matter that should be taken into consideration in the design process. The blast pressure on the structure due to nearby explosion is of very high magnitude and very short duration. Such an impulsive loading requires dynamic time-history analysis. This paper describes the nature of explosion of explosive materials and dynamic pressure developed on the nearby structure in lieu of explosion. Initially, efforts have been made to determine the effect of 1000 kg of C4 explosive material as an equivalent weight of TNT on different surfaces of a building model at a stand-off distance of 22.5m. The intensity of blast load on each surface is analytically determined as a record of pressure time history. Further attempts have been made to determine the effect of distance of blast for the same explosive material on building surfaces at stand-off distance of 10m, 18.5m, 22.5m and 27m. The effect of different explosives, i.e., TNT, C4, RDX and PETN on building surfaces at constant stand-off distance of 22.5m has also been determined. From the analysis, it is observed that the effect of blast load on front and rear surface of the building is critical. For close range explosions, deformations on front surface are more but with increase in stand-off distance, maximum deformations occur in roof surface.
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Ding, Xuheng, Kai Liao, Simon Birrer, Anowar J. Shajib, Tommaso Treu, and Lilan Yang. "Improved time-delay lens modelling and H0 inference with transient sources." Monthly Notices of the Royal Astronomical Society 504, no. 4 (May 4, 2021): 5621–28. http://dx.doi.org/10.1093/mnras/stab1240.
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ABSTRACT Strongly lensed explosive transients such as supernovae, gamma-ray bursts, fast radio bursts, and gravitational waves are very promising tools to determine the Hubble constant (H0) in the near future in addition to strongly lensed quasars. In this work, we show that the transient nature of the point source provides an advantage over quasars: The lensed host galaxy can be observed before or after the transient’s appearance. Therefore, the lens model can be derived from images free of contamination from bright point sources. We quantify this advantage by comparing the precision of a lens model obtained from the same lenses with and without point sources. Based on Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) observations with the same sets of lensing parameters, we simulate realistic mock data sets of 48 quasar lensing systems (i.e. adding AGN in the galaxy centre) and 48 galaxy–galaxy lensing systems (assuming the transient source is not visible but the time delay and image positions have been or will be measured). We then model the images and compare the inferences of the lens model parameters and H0. We find that the precision of the lens models (in terms of the deflector mass slope) is better by a factor of 4.1 for the sample without lensed point sources, resulting in an increase of H0 precision by a factor of 2.9. The opportunity to observe the lens systems without the transient point sources provides an additional advantage for time-delay cosmography over lensed quasars. It facilitates the determination of higher signal-to-noise stellar kinematics of the main deflector, and thus its mass density profile, which, in turn plays a key role in breaking the mass-sheet degeneracy and constraining H0.
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Kuroda, Ritsu, Kenji Kontani, Yasunari Kanda, Toshiaki Katada, Takashi Nakano, Yu-ichi Satoh, Norio Suzuki, and Hideyo Kuroda. "Increase of cGMP, cADP-ribose and inositol 1,4,5-trisphosphate preceding Ca2+ transients in fertilization of sea urchin eggs." Development 128, no. 22 (November 15, 2001): 4405–14. http://dx.doi.org/10.1242/dev.128.22.4405.
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Transient increases, or oscillations, of cytoplasmic free Ca2+ concentration, [Ca2+]i, occur during fertilization of animal egg cells. In sea urchin eggs, the increased Ca2+ is derived from intracellular stores, but the principal signaling and release system involved has not yet been agreed upon. Possible candidates are the inositol 1,4,5-trisphosphate receptor/channel (IP3R) and the ryanodine receptor/channel (RyR) which is activated by cGMP or cyclic ADP-ribose (cADPR). Thus, it seemed that direct measurements of the likely second messenger candidates during sea urchin fertilization would be essential to an understanding of the Ca2+ signaling pathway. We therefore measured the cGMP, cADPR and inositol 1,4,5-trisphosphate (IP3) contents of sea urchin eggs during the early stages of fertilization and compared these with the [Ca2+]i rise in the presence or absence of an inhibitor against soluble guanylate cyclase. We obtained three major experimental results: (1) cytosolic cGMP levels began to rise first, followed by cADPR and IP3 levels, all almost doubling before the explosive increase of [Ca2+]i; (2) most of the rise in IP3 occurred after the Ca2+ peak; IP3 production could also be induced by the artificial elevation of [Ca2+]i, suggesting the large increase in IP3 is a consequence, rather than a cause, of the Ca2+ transient; (3) the measured increase in cGMP was produced by the soluble guanylate cyclase of eggs, and inhibition of soluble guanylate cyclase of eggs diminished the production of both cADPR and IP3 and the [Ca2+]i increase without the delay of Ca2+ transients. Taken together, these results suggest that the RyR pathway involving cGMP and cADPR is not solely responsible for the initiating event, but contributes to the Ca2+ transients by stimulating IP3 production during fertilization of sea urchin eggs.
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Bravo, S., and X. Blanco-Cano. "Signatures of interplanetary transients behind shocks and their associated near-surface solar activity." Annales Geophysicae 16, no. 4 (April 30, 1998): 359–69. http://dx.doi.org/10.1007/s00585-998-0359-4.
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Abstract. Interplanetary transients with particular signatures different from the normal solar wind have been observed behind interplanetary shocks and also without shocks. In this paper we have selected four well-known transient interplanetary signatures, namely: magnetic clouds, helium enhancements and bidirectional electron and ion fluxes, found in the solar wind behind shocks, and undertaken a correlative study between them and the corresponding solar observations. We found that although commonly different signatures appear in a single interplanetary transient event, they are not necessarily simultaneous, that is, they may belong to different plasma regions within the ejecta, which suggests that they may be generated by complex processes involving the ejection of plasma from different solar regions. We also found that more than 90% of these signatures correspond to cases when an Hα flare and/or the eruption of a filament occurred near solar central meridian between 1 and 4 days before the observation of the disturbance at 1 AU, the highest association being with flares taking place between 2 and 3 days before. The majority of the Hα flares were also accompanied by soft X-ray events. We also studied the longitudinal distribution of the associated solar events and found that between 80% and 90% of the interplanetary ejecta were associated with solar events within a longitudinal band of ±30° from the solar central meridian. An east-west asymmetry in the associated solar events seems to exist for some of the signatures. We also look for coronal holes adjacent to the site of the explosive event and find that they were present almost in every case.Key words. Interplanetary physics · Interplanetary shocks · Solar wind plasma · Solar physics · Flares and mass ejections
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Raynaud, Raphaël, Jérôme Guilet, Hans-Thomas Janka, and Thomas Gastine. "Magnetar formation through a convective dynamo in protoneutron stars." Science Advances 6, no. 11 (March 2020): eaay2732. http://dx.doi.org/10.1126/sciadv.aay2732.
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The release of spin-down energy by a magnetar is a promising scenario to power several classes of extreme explosive transients. However, it lacks a firm basis because magnetar formation still represents a theoretical challenge. Using the first three-dimensional simulations of a convective dynamo based on a protoneutron star interior model, we demonstrate that the required dipolar magnetic field can be consistently generated for sufficiently fast rotation rates. The dynamo instability saturates in the magnetostrophic regime with the magnetic energy exceeding the kinetic energy by a factor of up to 10. Our results are compatible with the observational constraints on galactic magnetar field strength and provide strong theoretical support for millisecond protomagnetar models of gamma-ray burst and superluminous supernova central engines.
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Fragione, Giacomo, Brian D. Metzger, Rosalba Perna, Nathan W. C. Leigh, and Bence Kocsis. "Electromagnetic transients and gravitational waves from white dwarf disruptions by stellar black holes in triple systems." Monthly Notices of the Royal Astronomical Society 495, no. 1 (May 13, 2020): 1061–72. http://dx.doi.org/10.1093/mnras/staa1192.
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ABSTRACT Mergers of binaries comprising compact objects can give rise to explosive transient events, heralding the birth of exotic objects that cannot be formed through single-star evolution. Using a large number of direct N-body simulations, we explore the possibility that a white dwarf (WD) is dynamically driven to tidal disruption by a stellar-mass black hole (BH) as a consequence of the joint effects of gravitational wave (GW) emission and Lidov–Kozai oscillations imposed by the tidal field of an outer tertiary companion orbiting the inner BH–WD binary. We explore the sensitivity of our results to the distributions of natal kick velocities imparted to the BH and WD upon formation, adiabatic mass loss, semimajor axes and eccentricities of the triples, and stellar-mass ratios. We find rates of WD–tidal disruption events (TDEs) in the range 1.2 × 10−3 − 1.4 Gpc−3 yr−1 for z ≤ 0.1, rarer than stellar TDEs in triples by a factor of ∼3–30. The uncertainty in the TDE rates may be greatly reduced in the future using GW observations of Galactic binaries and triples with LISA. WD–TDEs may give rise to high-energy X-ray or gamma-ray transients of duration similar to long gamma-ray bursts but lacking the signatures of a core-collapse supernova, while being accompanied by a supernova-like optical transient that lasts for only days. WD–BH and WD–NS binaries will also emit GWs in the LISA band before the TDE. The discovery and identification of triple-induced WD–TDE events by future time domain surveys and/or GWs could enable the study of the demographics of BHs in nearby galaxies.
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Lazar, Alexandres, and Volker Bromm. "Probing the initial mass function of the first stars with transients." Monthly Notices of the Royal Astronomical Society 511, no. 2 (January 28, 2022): 2505–14. http://dx.doi.org/10.1093/mnras/stac176.
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ABSTRACT The emergence of the first, so-called Population III (Pop III), stars shaped early cosmic history in ways that crucially depends on their initial mass function (IMF). However, because of the absence of direct observational constraints, the detailed IMF remains elusive. Nevertheless, numerical simulations agree in broad terms that the first stars were typically massive and should often end their lives in violent, explosive deaths. These fates include extremely luminous pair-instability supernovae (PISNe) and bright gamma-ray bursts (GRBs), the latter arising from the collapse of rapidly rotating progenitor stars into black holes. These high-redshift transients are expected to be within the detection limits of upcoming space telescope missions, allowing to place effective constraints on the shape of the primordial IMF that is not easily accessible with other probes. This paper presents a framework to probe the Pop III IMF, utilizing the cosmological source densities of high-redshift PISNe and GRBs. Considering these transients separately could provide useful constraints on the Pop III IMF, but tighter bounds are obtainable by combining PISN and GRB counts. This combined diagnostic is more robust as it is independent of the underlying Pop III star formation rate density, an unknown prior. Future surveys promise to capture most high-redshift GRBs across the entire sky, but high-redshift PISN searches with future telescopes, e.g. Roman Space Telescope, will likely be substantially incomplete. Nevertheless, we demonstrate that even such lower bounds on the PISN count will be able to provide key constraints on the primordial IMF, in particular, if it is top-heavy or not.
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O'Brien, P., and P. Jonker. "Studying stellar explosions with Athena." Proceedings of the International Astronomical Union 11, A29B (August 2015): 243. http://dx.doi.org/10.1017/s1743921316005147.
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AbstractAthena is the second large mission selected in the ESA Cosmic Vision plan. With its large collecting area, high spectral-energy resolution (X-IFU instrument) and impressive grasp (WFI instrument), Athena will truly revolutionise X-ray astronomy. The most prodigious sources of high-energy photons are often transitory in nature. Athena will provide the sensitivity and spectral resolution coupled with rapid response to enable the study of the dynamic sky. Potential sources include: distant Gamma-Ray Bursts to probe the reionisation epoch and find missing baryons in the cosmic web; tidal disruption events to reveal dormant supermassive and intermediate-mass black holes; and supernova explosions to understand progenitors and their environments. We illustrate Athenas capabilities and show how it will be able to constrain the nature of explosive transients including gas metallicity and dynamics.
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Moriya, Takashi J. "Light-curve and spectral properties of ultra-stripped core-collapse supernovae." Proceedings of the International Astronomical Union 12, S329 (November 2016): 426. http://dx.doi.org/10.1017/s1743921317000187.
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AbstractWe discuss light-curve and spectral properties of ultra-stripped core-collapse supernovae. Ultra-stripped supernovae are supernovae with ejecta masses of only ~0.1M⊙ whose progenitors lose their envelopes due to binary interactions with their compact companion stars. We follow the evolution of an ultra-stripped supernova progenitor until core collapse and perform explosive nucleosynthesis calculations. We then synthesize light curves and spectra of ultra-stripped supernovae based on the nucleosynthesis results. We show that ultra-stripped supernovae synthesize ~0.01M⊙ of the radioactive 56Ni, and their typical peak luminosity is around 1042 erg s−1 or −16 mag. Their typical rise time is 5 − 10 days. By comparing synthesized and observed spectra, we find that SN 2005ek and some of so-called calcium-rich gap transients like PTF10iuv may be related to ultra-stripped supernovae.
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Burman, Aditya kumar. "Transient Effect of Random Loads on Reinforced Cement Concrete Building on RCC Building with Staad Pro. V8i." ECS Transactions 107, no. 1 (April 24, 2022): 15573–85. http://dx.doi.org/10.1149/10701.15573ecst.
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Abstract. Dynamic load is one which changes with time quickly in comparison to the structure's natural frequency. If it varies quickly, the activity must be determined with a dynamic analysis. Explosive loads and impact loads are transients, or loads that are applied dynamically as one-half cycle of high amplitude. This transient load is applied only for a specific and typically short period of time in the case of blast loads typically less than one-tenth of a second. The response of the engineering structural building due to the reason of periodic load RCC building structure has been severely damaged, collapse and develop cracks. Bomb blast is the best example for impulsive load. To determine the response of a G+3 RCC building model in STAAD Pro subjected to triangular, rectangular and sinusoidal impulsive force for 0.5 seconds with maximum magnitude of 100kN. Effect of such loads on front, roof and side portion of the building studied. Observe that the critical deformations obtained on the front and roof portion of building. Effect of deformation along height of building was parabolic in nature with maximum deflection at top floor of building. It was also noted i.e sufficient reinforcement should be provided in beam, columns and slabs to impart ductility to the building against impulse loads.There is more demand for construction of high buildings due to increasing urbanization and population.
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Antoniadis, J., S. Chanlaridis, G. Gräfener, and N. Langer. "Type Ia supernovae from non-accreting progenitors." Astronomy & Astrophysics 635 (March 2020): A72. http://dx.doi.org/10.1051/0004-6361/201936991.
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Type Ia supernovae (SNe Ia) are manifestations of stars that are deficient in hydrogen and helium, and disrupt in a thermonuclear runaway. While explosions of carbon-oxygen white dwarfs are thought to account for the majority of events, part of the observed diversity may be due to varied progenitor channels. We demonstrate that helium stars with masses between ∼1.8 and 2.5 M⊙ may evolve into highly degenerate cores with near-Chandrasekhar mass and helium-free envelopes that subsequently ignite carbon and oxygen explosively at densities of ∼(1.8−5.9) × 109 g cm−3. This occurs either due to core growth from shell burning (when the core has a hybrid CO/NeO composition), or following ignition of residual carbon triggered by exothermic electron captures on 24Mg (for a NeOMg-dominated composition). We argue that the resulting thermonuclear runaway is likely to prevent core collapse, leading to the complete disruption of the star. The available nuclear energy at the onset of explosive oxygen burning suffices to create ejecta with a kinetic energy of ∼1051 erg, as in typical SNe Ia. Conversely, if these runaways result in partial disruptions, the corresponding transients would resemble SN Iax events similar to SN 2002cx. If helium stars in this mass range indeed explode as SNe Ia, then the frequency of events would be comparable to the observed SN Ib/c rates, thereby sufficing to account for the majority of SNe Ia in star-forming galaxies.
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Bode, M. F., and W. T. Vestrand. "Small and Robotic Telescopes in the Era of Massive Time-Domain Surveys." Proceedings of the International Astronomical Union 7, S285 (September 2011): 235–38. http://dx.doi.org/10.1017/s1743921312000658.
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AbstractWe have entered an era in time-domain astronomy in which the detected rate of explosive transients and important ephemeral states in persistent objects threatens to overwhelm the world's supply of traditional follow-up telescopes. As new, comprehensive time-domain surveys become operational and wide-field multi-messenger observatories come on-line, that problem will become more acute. The goal of this workshop was to foster discussion about how autonomous robotic telescopes and small-aperture conventional telescopes can be employed in the most effective ways to help deal with the coming deluge of scientifically interesting follow-up opportunities. Discussion topics included the role of event brokers, automated event triage, the establishment of cooperative global telescope networks, and real-time coordination of observations at geographically diverse sites. It therefore included brief overviews of the current diverse landscape of telescopes and their interactions, and also considered planned and potential new facilities and operating models.
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Walkowicz, Lucianne M. "The Future of the Time Domain with LSST." Proceedings of the International Astronomical Union 7, S285 (September 2011): 158. http://dx.doi.org/10.1017/s1743921312000518.
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SummaryIn the coming decade LSST's combination of all-sky coverage, consistent long-term monitoring and flexible criteria for event identification will revolutionize studies of a wide variety of astrophysical phenomena. Time-domain science with LSST encompasses objects both familiar and exotic, from classical variables within our Galaxy to explosive cosmological events. Increased sample sizes of known-but-rare observational phenomena will quantify their distributions for the first time, thus challenging existing theories. Perhaps most excitingly, LSST will provide the opportunity to sample previously untouched regions of parameter space. LSST will generate ‘alerts’ within 60 seconds of detecting a new transient, permitting the community to follow up unusual events in greater detail. However, follow-up will remain a challenge as the volume of transients will easily saturate available spectroscopic resources. Characterization of events and access to appropriate ancillary data (e.g. from prior observations, either in the optical or in other passbands) will be of the utmost importance in prioritizing follow-up observations. The incredible scientific opportunities and unique challenges afforded by LSST demand organization, forethought and creativity from the astronomical community. To learn more about the telescope specifics and survey design, as well as obtaining a overview of the variety of the scientific investigations that LSST will enable, readers are encouraged to look at the LSST Science Book: http://www.lsst.org/lsst/scibook. Organizational details of the LSST science collaborations and management may be found at http://www.lsstcorp.org.
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Smith, Nathan, Jennifer E. Andrews, Armin Rest, Federica B. Bianco, Jose L. Prieto, Tom Matheson, David J. James, R. Chris Smith, Giovanni Maria Strampelli, and A. Zenteno. "Light echoes from the plateau in Eta Carinae’s Great Eruption reveal a two-stage shock-powered event." Monthly Notices of the Royal Astronomical Society 480, no. 2 (August 3, 2018): 1466–98. http://dx.doi.org/10.1093/mnras/sty1500.
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ABSTRACT We present multi-epoch photometry and spectroscopy of a light echo from η Carinae’s 19th century Great Eruption. This echo's light curve shows a steady decline over a decade, sampling the 1850s plateau of the eruption. Spectra show the bulk outflow speed increasing from ∼150 km s−1 at early times, up to ∼600 km s−1 in the plateau. Later phases also develop remarkably broad emission wings indicating mass accelerated to more than 10 000 km s−1. Together with other clues, this provides direct evidence for an explosive ejection. This is accompanied by a transition from a narrow absorption line spectrum to emission lines, often with broad or asymmetric P Cygni profiles. These changes imply that the pre-1845 luminosity spikes are distinct from the 1850s plateau. The key reason for this change may be that shock interaction with circumstellar material (CSM) dominates the plateau. The spectral evolution of η Car closely resembles that of the decade-long eruption of UGC 2773-OT, which had clear signatures of shock interaction. We propose a two-stage scenario for η Car’s eruption: (1) a slow outflow in the decades before the eruption, probably driven by binary interaction that produced a dense equatorial outflow, followed by (2) explosive energy injection that drove CSM interaction, powering the plateau and sweeping slower CSM into a fast shell that became the Homunculus. We discuss how this sequence could arise from a stellar merger in a triple system, leaving behind the eccentric binary seen today. This gives a self-consistent scenario that may explain interacting transients across a wide range of initial mass.
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Giuseppe, Di Sciascio. "The Science Case for a Southern Wide Field of View Detector." EPJ Web of Conferences 209 (2019): 01035. http://dx.doi.org/10.1051/epjconf/201920901035.
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EAS arrays are survey instruments able to monitor continuously all the overhead sky. Their sensitivity in the sub-TeV/TeV energy domain cannot compete with that of Cherenkov telescopes, but the wide field of view (about 2 sr) is ideal to complement directional detectors by performing unbiased sky surveys, by monitoring variable or flaring sources such as Active Galactic Nuclei (AGN) and to discover transients or explosive events (GRBs). Arrays are well suited to study extended sources, such as the Galactic diffuse emission, and to measure the spectra of Galactic sources at the highest energies (near or beyond 100 TeV). An EAS array is able to detect at the same time events induced by photons and charged cosmic rays, thus studying the connection between these two messengers of the non-thermal Universe. Therefore, these detectors are, by definition, multi-messenger instruments. All EAS arrays presently in operation or under installation are located in the Northern hemisphere. The scientific potential of a next-generation survey instrument in the Southern Hemisphere will be presented and briefly discussed.
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Bonalumi, Pamela, Matteo Colombo, and Marco di Prisco. "Internal Explosions in Embedded Concrete Pipes." Applied Mechanics and Materials 82 (July 2011): 452–57. http://dx.doi.org/10.4028/www.scientific.net/amm.82.452.
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Blast tests on a full-scale concrete pipe embedded in soft soil were carried out to evaluate the behavior of the soil-structure system under the internal detonation of high-energy solid explosives. Two different stages were considered: the former focused on the detonation of a low entity charge within the pipe to maintain the concrete in the elastic regime and the latter concerned with adopting larger quantities of explosive to produce cracking and failure of the structure. Cylindrical charges ranging from few grams to hundreds of grams of a high-energy solid explosive were investigated and different tests were performed for each quantity by inserting the explosive charge in a cardboard cylinder hanged up in the middle of the pipe central segment by means of three thin plastic wires. The following quantities were measured in different sections along the pipe: side-on and reflected pressure-time histories at the inner surface of the structure, pipe radial acceleration, peak particle acceleration of the surrounding soil by means of accelerometers placed at different distances and depths from the section where the explosion occurred. The experimental results obtained during the performed blast tests are thus analyzed to understand the soil-structure system behavior under such fast transient dynamic phenomena.
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Grishin, Evgeni, Alexey Bobrick, Ryosuke Hirai, Ilya Mandel, and Hagai B. Perets. "Supernova explosions in active galactic nuclear discs." Monthly Notices of the Royal Astronomical Society 507, no. 1 (July 12, 2021): 156–74. http://dx.doi.org/10.1093/mnras/stab1957.
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ABSTRACT Active galactic nuclei (AGNs) are prominent environments for stellar capture, growth, and formation. These environments may catalyse stellar mergers and explosive transients, such as thermonuclear and core-collapse supernovae (SNe). SN explosions in AGN discs generate strong shocks, leading to unique observable signatures. We develop an analytical model that follows the evolution of the shock propagating in the disc until it eventually breaks out. We derive the peak luminosity, bolometric light curve, and breakout time. The peak luminosities may exceed 1045 erg s−1 and last from hours to days. The brightest explosions occur in regions of reduced density: either off-plane, or in discs around low-mass central black holes (${\sim} 10^6\ \rm {M}_\odot$), or in starved subluminous AGNs. Explosions in the latter two sites are easier to observe due to a reduced AGN background luminosity. We perform suites of 1D Lagrangian radiative hydrodynamics snec code simulations to validate our results and obtain the luminosity in different bands, and 2D axisymmetric Eulerian hydrodynamics code hormone simulations to study the morphology of the ejecta and its deviation from spherical symmetry. The observed signature is expected to be a bright blue, UV or X-ray flare on top of the AGN luminosity from the initial shock breakout, while the subsequent red part of the light curve will largely be unobservable. We estimate the upper limit for the total event rate to be $\mathcal {R}\lesssim 100\ \rm yr^{-1}\ Gpc^{-3}$ for optimal conditions and discuss the large uncertainties in this estimate. Future high-cadence transient searches may reveal these events. Some existing tidal disruption event candidates may originate from AGN SNe.
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Toonen, S., H. B. Perets, A. P. Igoshev, E. Michaely, and Y. Zenati. "The demographics of neutron star – white dwarf mergers." Astronomy & Astrophysics 619 (November 2018): A53. http://dx.doi.org/10.1051/0004-6361/201833164.
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Context. The mergers of neutron stars (NSs) and white dwarfs (WDs) could give rise to explosive transients, potentially observable with current and future transient surveys. However, the expected properties and distribution of such events is not well understood. Aims. Here we characterise the rates of such events, their delay-time distributions, their progenitors, and the distribution of their properties. Methods. We use binary population synthesis models and consider a wide range of initial conditions and physical processes. In particular we consider different common-envelope evolution models and different NS natal kick distributions. We provide detailed predictions arising from each of the models considered. Results. We find that the majority of NS–WD mergers are born in systems in which mass-transfer played an important role, and the WD formed before the NS. For the majority of the mergers the WDs have a carbon-oxygen composition (60−80%) and most of the rest are with oxygen-neon WDs. The time-integrated rates of NS–WD mergers are in the range of 3−15% of the type Ia supernovae (SNe) rate. Their delay-time distribution is very similar to that of type Ia SNe, but is slightly biased towards earlier times. They typically explode in young 100 Myr < τ < 1 Gyr environments, but have a tail distribution extending to long, gigayear-timescales. Models including significant kicks give rise to relatively wide offset distribution extending to hundreds of kiloparsecs. Conclusions. The demographic and physical properties of NS–WD mergers suggest they are likely to be peculiar type Ic-like SNe, mostly exploding in late-type galaxies. Their overall properties could be related to a class of recently observed rapidly evolving SNe, while they are less likely to be related to the class of Ca-rich SNe.
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Yaari, Y., A. Konnerth, and U. Heinemann. "Nonsynaptic epileptogenesis in the mammalian hippocampus in vitro. II. Role of extracellular potassium." Journal of Neurophysiology 56, no. 2 (August 1, 1986): 424–38. http://dx.doi.org/10.1152/jn.1986.56.2.424.
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The role of extracellular K+ (K+o) in nonsynaptic epileptogenesis induced in the CA1 area of rat hippocampal slices by lowering [Ca2]o was studied with K+-selective microelectrodes (KSMs). Extracellular field potentials and [K+]o were recorded simultaneously with 1-2 KSMs in the CA1 stratum pyramidale. In slices perfused with an oxygenated standard physiological solution (containing 2 mM Ca2+), base-line [K+]o was stable for several hours. The washout of Ca2+o was accompanied by a gradual tonic rise of [K+]o. Spontaneous and stimulus-evoked maximal seizurelike events (SLEs) appeared when [K+]o was approximately 0.5 mM above the initial 5 mM base line. These changes were reversible in normal medium. When K+o was pressure ejected in the CA1 stratum pyramidale of spontaneously active slices, a local rise in [K+]o of approximately 0.5 mM was necessary to trigger a SLE. A similar apparent [K+]o "threshold" was associated with SLEs evoked by electrical stimulation. Increasing [K+] in the perfusing solution by small increments (1 mM) markedly enhanced SLEs frequency and velocity of spread and decreased the period of absolute refractoriness that succeeded each paroxysm. Similar changes occurred during periods of transient hypoxia. Small [K+] decreases in the perfusate had the converse effects. Spontaneous SLEs were associated with phasic increases in [K+]o. In simultaneous [K+]o recordings from two layers, these transients were largest (up to 3.5 mM above base line) and rose more steeply at the stratum pyramidale. Toward the outer dendritic layers they became smaller, slower in time course, and delayed in onset. We conclude that the main source for these [K+]o transients are the hippocampal pyramidal cell bodies, which discharge intensely during a SLE, and that excess K+o is spatially dispersed around the discharge zone of the paroxysm. [K+]o continued to rise, though at a slower rate, throughout the course of a SLE. Following SLE termination, [K+]o decayed slowly to base line. The invasion of a CA1 region by a propagating SLE was preceded quite often by a slow rise in [K+]o. A sudden transition to a steeply rising [K+]o marked the explosive recruitment of this region into the discharge zone of the spreading paroxysm. The total (tonic and phasic) increase in [K+]o during SLEs did not surpass a maximal level of approximately 9 mM, which was the ceiling level of [K+]o in low [Ca2+]o. However, when spreading depression occurred, [K+]o rose up to 30-40 mM for several minutes. Spreading depression rarely appeared spontaneously despite the recurrence of SLEs, but could be provoked by repetitive electrical stimulation.(ABSTRACT TRUNCATED AT 400 WORDS)
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Kong, Desen, Yu Xu, and Cheng Song. "Dynamic Response of Composite Steel Lining Structure under Blast Loading." Shock and Vibration 2020 (June 30, 2020): 1–12. http://dx.doi.org/10.1155/2020/2693659.
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According to the advantages of high tensile resistance and high shear strength of composite steel plate, a new antiexplosion protection method of composite steel plate lining structure is put forward. The numerical model of explosion impact of subway tunnel with composite steel plate lining structure was established by dynamic analysis software. The transient dynamic response of lining structure with the composite steel plate was simulated when explosion occurred. The research results show that the influence of explosive quantity on each point of composite steel plate lining structure is different and the change of acceleration near the centre of the detonation source is generally greater than the multiple of the increase of explosive quantity. The increase of velocity and displacement is basically consistent with the quantity of explosive. The influence of axial stress on the lining structure is the least, and the influence of the lining structure is greater in the y-direction than in the x-direction. The research results can provide the plan and basis for the emergency response of the subway tunnel.
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Ren, Jia, Ken Chen, Yun Wang, and Zi-Gao Dai. "Interacting Kilonovae: Long-lasting Electromagnetic Counterparts to Binary Mergers in the Accretion Disks of Active Galactic Nuclei." Astrophysical Journal Letters 940, no. 2 (November 29, 2022): L44. http://dx.doi.org/10.3847/2041-8213/aca025.
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Abstract We investigate the dynamics and electromagnetic (EM) signatures of neutron star–neutron star (NS–NS) or neutron star–black hole (NS–BH) merger ejecta that occur in the accretion disk of an active galactic nucleus (AGN). We find that the interaction between ejecta and disk gas leads to important effects on the dynamics and radiation. We show five stages of the ejecta dynamics: gravitational slowing down, coasting, Sedov–Taylor deceleration in the disk, reacceleration after the breakout from the disk surface, and momentum-conserved snowplow phase. Meanwhile, the radiation from the ejecta is so bright that its typical peak luminosity reaches a few times 1043–1044 erg s−1. Since most of the radiation energy has converted from the kinetic energy of merger ejecta, we call such an explosive phenomenon an interacting kilonova (IKN). It should be emphasized that IKNe are very promising, bright EM counterparts to NS–NS/BH–NS merger events in AGN disks. The bright peak luminosity and long rising time (i.e., 10 to 20 days in UV bands, 30 to 50 days in optical bands, and 100 days to hundreds of days in IR bands) allow most survey telescopes to have ample time to detect an IKN. However, the peak brightness, peak time, and evolution pattern of the light curve of an IKN are similar to a superluminous supernova in a galactic nucleus and a tidal disruption event making it difficult to distinguish between them. But it also suggests that IKNe might have been present in recorded AGN transients.
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Xue, Jiai, Hao Jiang, and Jun Yao. "Simulation and Experimental Research on Temperature Increase of Safety Gear Action of Explosive-Proof Lift." Applied Mechanics and Materials 152-154 (January 2012): 287–92. http://dx.doi.org/10.4028/www.scientific.net/amm.152-154.287.
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The kinetic energy of lift car will be consumed by the friction between the safety gear and guide rail in emergent braking process. This will lead to remarkable temperate increase of frictional surface. Due to the explosive atmospheres in which the explosive-proof lift servers, the high temperature may result in severe explosion accident. In this paper, an finite element model is developed to analysis this progress. The transient heat flux density is derived from energy transformation progress in safety gear action, and applied as boundary condition to the finite element model. Experiments are carried out to measure the temperature increase of safety gear frictional surface, and the results show good coincidence of temperature increase tendency between experiments and simulations.
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Litz, C. J. "Laser Doppler Vibrometer: Application of DOE/Taguchi Methodologies to Pyroshock Response Spectra." Shock and Vibration 4, no. 2 (1997): 115–23. http://dx.doi.org/10.1155/1997/617146.
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Statistical methodologies were employed for measuring and analyzing the explosively induced transient responses of a flat steel plate excited with shock. The application of design of experiment methodology was made to structure and test a Taguchi L9(32) full factorial experimental matrix (which uses nine tests to study two factors, with each factor examined at three levels) in which a helium-neon laser Doppler vibrometer and two piezocrystal accelerometers were used to monitor explosively induced vibrations ranging from 10 to 105Hz on a 96 × 48 × 0.25 in. flat steel plate. Resulting conclusions were drawn indicating how these techniques aid in understanding the pyroshock phenomenon with respect to the effects and interrelationships of explosive-charge weight and location on the laser Doppler and contract accelerometer recording systems.
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Perets, Hagai B. "Compact-object Formation, Retention, and Growth through Accretion onto Gas-embedded White Dwarfs/Neutron Stars in Gas-enriched Globular Clusters." Astrophysical Journal Letters 927, no. 2 (March 1, 2022): L23. http://dx.doi.org/10.3847/2041-8213/ac5822.
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Abstract Observations of pulsars in globular clusters (GCs) give evidence that more than >10%–20% of neutron stars (NSs) that ever formed in GCs were retained there. However, the velocity distribution of field pulsars peaks at 5–10 times the escape velocities of GCs. Consequently, only a small fraction of GC NSs should have been retained, which is potentially difficult to explain even accounting for low-velocity NSs formed through electron-capture supernovae (SNe). Thus, too few low-velocity NSs should have been retained, giving rise to the NS retention problem in GCs. Here we suggest a novel solution, in which the progenitors of most GC NSs were ONe white dwarfs (WDs) that accreted ambient intracluster gas and formed low-velocity NSs through accretion-induced collapse (AIC). The existence of an early gas-enriched environment in GCs is supported by observations of multiple stellar populations in GCs. It is thought that 10–100s of megayears after the formation of the first generation of stars, and after ONe WDs were already formed, GCs were replenished with gas, which formed a second generation of stars. Accretion of such replenished gas onto the ONe WDs catalyzed the AIC processes. The number of AIC-formed NSs is then sufficient to explain the large number of NSs retained in GCs. Similar processes might also drive CO WDs to produce Type Ia SNe or to merge and form NSs and similarly drive NSs to AIC and mergers producing BHs. Moreover, the wide variety of gas-catalyzed binary mergers and explosive transients suggested to occur in the gas-rich environments of an active galactic nucleus disk could similarly, and even more efficiently, occur in second-generation gas in GCs.
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Raspet, Richard, Jean Ezell, and Stephen V. Coggeshall. "Diffraction of an explosive transient." Journal of the Acoustical Society of America 79, no. 5 (May 1986): 1326–34. http://dx.doi.org/10.1121/1.393659.
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Yalinewich, Almog, and Christopher D. Matzner. "Optical transient from an explosion close to the stellar surface." Monthly Notices of the Royal Astronomical Society 490, no. 1 (September 16, 2019): 312–18. http://dx.doi.org/10.1093/mnras/stz2590.
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ABSTRACT We study the hydrodynamic evolution of an explosion close to the stellar surface, and give predictions for the radiation from such an event. We show that such an event will give rise to a multiwavelength transient. We apply this model to describe a precursor burst to the peculiar supernova iPTF14hls, which occurred in 1954, 60 yr before the supernova. We propose that the new generation of optical surveys might detect similar transients, and that they can be used to identify supernova progenitors well before the explosion.
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Jalinoos, Farrokh, and J. E. White. "Wave propagation from an explosive source." GEOPHYSICS 51, no. 3 (March 1986): 746–56. http://dx.doi.org/10.1190/1.1442127.
Full textAbstract:
The model proposed describes the radiation of the primary seismic pulse from an explosive source. The model incorporates a viscous Voigt liquid in description of the nonelastic rock deformation that the explosion causes. The problem is solved in the frequency domain, followed by Fourier synthesis to obtain waveforms. Comparisons of the theoretical results with field data in three sedimentary environments of shale, sandstone, and marl indicate good quantitative agreements in shape and duration of transient pulses. Values of angular normal stress obtained at the deformed boundary suggest a dynamic tensile strength of rocks that decreased with duration of the tensile stress transient. The radius of the deformed zone (B) scales with the charge size Q approximately as [Formula: see text] where n is [Formula: see text] or larger.