Gravity waves accompanying supernova explosions

In this paper, we systematically study spacetimes of gravitational plane waves in Einstein-aether theory. Due to the presence of the timelike aether vector field, now the problem in general becomes overdetermined. In particular, for the linearly polarized plane waves, there are five independent vacuum Einstein-aether field equations for three unknown functions. Therefore, solutions exist only for particular choices of the four free parameters $c_{i}$'s of the theory. We find that there exist eight cases, in two of which any form of gravitational plane waves can exist, similar to that in general relativity, while in the other six cases, gravitational plane waves exist only in particular forms. Beyond these eight cases, solutions either do not exist or are trivial (simply representing a Minkowski spacetime with a constant or dynamical aether field.).

This paper derives the total power or energy loss rate generated in the form of gravitational waves by an inspiralling compact binary system to the five halves post-Newtonian (2.5PN) approximation of general relativity. Extending a recently developed gravitational-wave generation formalism valid for arbitrary (slowly-moving) systems, we compute the mass multipole moments of the system and the relevant tails present in the wave zone to 2.5PN order. In the case of two point-masses moving on a quasi-circular orbit, we find that the 2.5PN contribution in the energy loss rate is entirely due to tails. Relying on an energy balance argument we derive the laws of variation of the instantaneous frequency and phase of the binary. The 2.5PN order in the accumulated phase is significantly large, being grossly of the same order of magnitude as the previous 2PN order, but opposite in sign. However finite mass effects at 2.5PN order are small. The results of this paper should be useful when analyzing the data from inspiralling compact binaries in future gravitational-wave detectors like VIRGO and LIGO.

We have recently suggested a set of nonlocally extended field equations in which Newton’s constant [Formula: see text] was promoted to a covariant differential operator [Formula: see text] composed by two different contributions. These two terms independently operate in the infrared (IR) and ultraviolet (UV) energy regimes. Considering the recent spectacular direct gravitational radiation measurements, we aim to compute the nonlocally modified orbital dynamics of a two-body system. In a first attempt, we determine the effective Newtonian potential from the nonlocal UV-wave equation to work out the modified Kepler orbits. In addition, we use data obtained from the perihelion precession of Mercury in order to derive an upper bound for the dimensionless UV-parameter [Formula: see text]. Finally, we determine the energy per unit time (power) released by a binary system in the form of gravitational waves. In this context, we observe that in the limit of vanishing UV-parameters, we eventually recover the result obtained in the context of the standard quadrupole formula.

Core-collapse supernovae (CCSNe) are among the most energetic explosions in the universe, liberating the prodigious amount of ~ 1053 erg, the binding energy of their compact remnants, neutron stars or stellar mass black holes. While 99% of this energy is emitted in neutrinos, 1% goes into the internal and asymptotic kinetic energy of the ejecta, and it is reasonable to assume that a tiny fraction is radiated in gravitational waves (GWs). Ever since the first experimental efforts to detect GWs, CCSNe have been considered prime sources of gravitational waves for interferometric detectors. Besides neutrinos, which have already been observed in the context of stellar core collapse of SN1987A, GWs could provide us access to the electromagnetically hidden compact inner core of some such cataclysmic events, supplying us for example with valuable information about the angular momentum distribution and the baryonic equation of state, both of which are uncertain. Furthermore, they might even help to constrain theoretically predicted SN mechanisms. However, GW astronomy strongly depends on the extensive data processing of the detector output on the basis of reliable GW estimates, which only recently have become feasible with the emerging power of supercomputers. The work presented in this thesis is concerned with numerical CCSN models and their imprints in GWs. I performed an extensive series of more than 30 three-dimensional magnetohydrodynamical (MHD) core-collapse simulations. My models are based on a 15M [...] progenitor stemming from stellar evolution calculations, an effective general relativistic potential and either the Lattimer-Swesty (with three possible compressibilities) or the Shen equation of state (EoS) for hot, dense matter. Furthermore, the neutrino transport is tracked by computationally efficient algorithms for the radiative transfer of massless fermions. I systematically investigated the effects of the microphysical finite-temperature nuclear EoS, the initial rotation rate, both the toroidal and the poloidal magnetic fields, and multidimensional gravitational potentials on the GW signature. Based on the results of these calculations, I obtained the largest – and also one of the most realistic – catalogue of GW signatures from 3D MHD stellar core collapse simulations at present. I stress the importance of including postbounce neutrino physics, since it quantitatively alters the GW signature. Non- and slowly-rotating models show GW emission caused by prompt and protoneutron star (PNS) convection. Moreover, the signal stemming from prompt convection allows for the distinction between the two different nuclear EoS indirectly by different properties of the fluid instabilities. For simulations with moderate or even fast rotation rates, I only find the axisymmetric type I wave signature at core bounce. In line with recent results, I could confirm that the maximum GW amplitude scales roughly linearly with the ratio of rotational to gravitational energy (T/|W|) at core bounce below a threshold value of about 10%. Furthermore, I point out that PNS can become dynamically unstable to rotational instabilities at T/|W| values as low as ~ 2% at core bounce. Apart from these two points, I show that it is generally very difficult to discern the effects of the individual features of the input physics in a GW signal from a rotating CCSN that can be attributed unambiguously to a specific model. Weak magnetic fields do not notably influence the dynamical evolution of the core and thus the GW emission. However, for strong initial poloidal magnetic fields ≥ 1012G, the combined action of flux-freezing and field winding leads to conditions where the ratio of magnetic field pressure to matter pressure reaches about unity which leads to the onset of a jet-like supernova explosion. The collimated bipolar out-stream of matter is then reflected in the emission of a type IV GW signal. In contradiction to axisymmetric simulations, I find evidence that nonaxisymmetric fluid modes can counteract or even suppress jet formation for models with strong initial toroidal magnetic fields. I emphasize the importance of including multidimensional gravitational potentials in rapidly rotating 3D CCSN simulations: taking them into account can alter the resulting GW amplitudes up to a factor of 2 compared to simulations which encounter gravity only by a monopolar approximation. Moreover, I show that the postbounce dynamics occuring in the outer layers (at radii R ≥ 200km) of models run with 3D gravity deviates vastly from the ones run with a 1D or 2D gravitational potential. The latter finding implies that both spherically symmetric and axisymmetric treatments of gravity are too restrictive for a quantitative description of the overall postbounce evolution of rapidly rotating CCSN models. The results of models with continued neutrino emission show that including deleptonization during the postbounce phase is an indispensable issue for the quantitative prediction of GWs from core-collapse supernovae, because it can alter the GW amplitude up to a factor of 10 compared to a pure hydrodynamical treatment. My collapse simulations indicate that corresponding events in our Galaxy would be detectable either by LIGO, if the source is rotating, or at least by the advanced LIGO detector, if it is not or only slowly rotating.

In their third observing run, the LIGO–Virgo–KAGRA gravitational-wave (GW) observatory was sensitive to binary black hole (BBH) mergers out to redshifts z merge ≈ 1. Because GWs are inefficient at shrinking the binary orbit, some of these BBH systems likely experienced long delay times τ between the formation of their progenitor stars at z form and their GW merger at z merge. In fact, the distribution of delay times predicted by isolated binary evolution resembles a power law with slope −1 ≲ α τ ≲ −0.35 and a minimum delay time of . We use these predicted delay time distributions to infer the formation redshifts of the ∼70 BBH events reported in the third GW transient catalog GWTC-3 and the formation rate of BBH progenitors. For our default α τ = –1 delay time distribution, we find that GWTC-3 contains at least one system (with 90% credibility) that formed earlier than z form > 4.4. Comparing our inferred BBH progenitor formation rate to the star formation rate, we find that at z form = 4, the number of BBH progenitor systems formed per stellar mass was and this yield dropped to by z form = 0. We discuss implications of this measurement for the cosmic metallicity evolution, finding that for typical assumptions about the metallicity dependence of the BBH yield, the average metallicity at z form = 4 was , although the inferred metallicity can vary by a factor of ≈3 for different assumptions about the BBH yield. Our results highlight the promise of current GW observatories to probe high-redshift star formation.

We develop a temporal simulation of the potentially detectable gravitational wave background from neutron star formation at cosmological distances. By using a recent model for the evolving star formation rate, we investigate the statistical distribution of gravitational wave amplitudes due to supernovae that result in neutron star formation in the Einstein-de Sitter cosmology. We find that the gravitational wave amplitude distribution in our frame is highly skewed, with skewness related to the distribution of sources, and that the potentially detectable gravitational wave strain is dominated by sources at a redshift of 2-3. Time traces of the simulation, using selected waveforms, are presented graphically and are also made available as web-based audio files. The method developed can readily be extended to different cosmologies, as well as to incorporate other waveforms and source types. This type of simulation will be useful in testing and optimizing detection strategies for gravitational wave backgrounds due to various types of individually undetectable astrophysical sources.

We live in a visual age, an age of images-iconic, instant, and influential-that have crystallized our conception of the large, the small, and the complex, of both inner and outer space. Some, like Robert Hooke's first microscopic views of the natural world, arose because of new technical capabilities. Others, like the first graphs, were breathtakingly simple but perennially useful. The first stunning picture of Earth from space stimulated an environmental consciousness that has grown ever since; the mushroom clouds from atomic and nuclear explosions became the ultimate symbol of death and destruction; Mercator's flat map of the Earth cemented an entire worldview. John D. Barrow's collection encompasses the frontiers of modern science and its most memorable historic moments. But this is much more than a picture book. Entertaining and informative essays accompany the powerful display of images that have illuminated concepts of far-reaching significance.

We have calculated gravitational waves induced by a test particle with eccentric orbits around a Schwarzschild black hole. The energy and angular momentum fluxes of gravitational waves emitted from various types of the orbits are shown. Comparing our results with those calculated by the semi-relativistic quadrupole formula, we find that, even for orbits with r ∼30 M, the amount and wave form of gravitational radiation are predominantly determined by the relativistic property, such as higher multipole contribution and curvature scattering effect of gravitational waves. We find that even in the case of circular orbits the wave form is highly deformed from a sine curve, indicating the importance of higher multipole contributions. On the other hand, the total energy flux emitted by gravitational waves is well estimated by the semi-relativistic quadrupole formula accidentally. Implications of these results to future detection of gravitational waves from a coalescing binary are also discussed.

The Bodies of August: Photographic Realism and Controversy at the National Air and Space Museum Bryan C. Taylor The sight that greeted our eyes was quite beyond what we had expected, because we saw this cloud of boiling dust and debris below us, with this tremendous mushroom on top. And beneath that was hidden the ruins of the city of Hiroshima. — Col. Paul Tibbets, August 6,1945 1 The nation requires anthems, flags. The poet offers discord. Rags. — Salman Rushdie 2 One consistent site of critical scholarship has been "realist" discourse circulating in public affairs. This term includes a variety of modernist, institutional discourses claiming unmediated access to the fundamental truths of social and physical reality. Implicitly, these discourses presume that communication is transparent, and that objective information about phenomena can be unproblematically expressed. Critics typically reject this claim to expose the Real as the product, not the referent, of strategic rhetoric. The self-effacing quality of realism, critics claim, masks its activation of culturally preferred codes for representation (such as the shaky, hand-held camerawork which connotes immediacy and authenticity for the viewers of cinema-verite). These codes reproduce ideological premises concerning what is normal, good, and inevitable (and their opposites) in social life. In their repetition and mutual reinforcement, realist discourses create verisimilitude, not validity .3 Critics have investigated the genres of journalism, literature, ethnography, science, history, and international relations to show how the use of realism authorizes interested accounts, legitimates hegemonic identities, and obscures the contingency of narrative production.4 Frequently, these practices also mobilize competing interests and stimulate resistance among marginalized groups.5 In this essay, I am concerned with the relationship between realism and nuclear weapons. Three themes in this relationship are evoked in the epigraph from Paul Bryan C. Taylor is Associate Professor of Communication at the University of Colorado in Boulder, Colorado. © Rhetoric & Public Affairs Vol. 1, No. 3,1998, pp. 331-361 ISSN 1094-8392 332 Rhetoric & Public Affairs Tibbets, pilot of the world's first atomic bombing mission. One theme is the importance of vision for realism. Like all nuclear witnesses, Tibbets was faced with translating the awesome evidence of his senses for his audience (here, journalists requesting an account of his "reactions over the target"). Although the Enola Gay's crew experienced Hiroshima through a variety of senses—one excited crewman believed he could taste the bomb's radiation6—here it is vision that predominates, and vision that establishes Tibbets's complex credibility as an author, witness and survivor of the scene. Another theme in this account involves the excessive quality of the nuclear object. Although Tibbets had been briefed prior to his mission about the destructive force of the weapon, its effects were still "quite beyond" his expectations . His remark indicates the threat posed by nuclear excess to the adequacy of realism for projecting and depicting nuclear events. A final theme involves the tension between presence and absence in nuclear realism. Tibbets's language emphasizes the signs of nuclear explosion: "boiling dust and debris," and the iconic mushroom cloud. Yet in its concluding sentence, the account also acknowledges its limitations. Beyond the presence of these signs lie unseen and unspeakable phenomena. The mushroom cloud is both a sign of the bomb's detonation and a screen that prevents Tibbets from engaging the "hidden" fate of those below. "The ruins" of Hiroshima are a lacuna where his realism falters . Historically, his comments initiate a tradition in which nuclear excess has often remained "beneath" official rhetoric, a surplus of unrealized meaning signaled by its incompleteness. In this essay, I explore the operation of these themes in the related realisms of history , museology, and photography. Specifically, I am concerned with Hiroshima and Nagasaki as events which alternately defy and incite these discourses. Since 1945, nuclear realism has circulated in a variety of genres, such as personal narrative (which claims to transmit the truth of nuclear events through the direct witness of individual speakers), and orthodox historiography (which recovers the "facts" of those events from their encoding in the raw data of documents and testimony).7 These verbal and iconographie discourses do not operate exclusively; they frequently combine and interact in texts such...

This paper discusses the gravitational radiation that accompanies the formation of a rotating protoneutron star. Mainly large-scale entropy inhomogeneities develope inside the star. As a result, bubbles of hot nuclear substance are formed, and convective motions arise: bubbles of hot neutron matter float to the surface of the star, while cold matter sinks to its center. Such large-scale motions of material give rise to an inhomogeneous mass distribution inside the star. Variable asymmetry appears in the mass distribution, and this causes gravitational radiation.

We review the formation and evolution of compact binary stars consisting of white dwarfs (WDs), neutron stars (NSs), and black holes (BHs). Binary NSs and BHs are thought to be the primary astrophysical sources of gravitational waves (GWs) within the frequency band of ground-based detectors, while compact binaries of WDs are important sources of GWs at lower frequencies to be covered by space interferometers (LISA). Major uncertainties in the current understanding of properties of NSs and BHs most relevant to the GW studies are discussed, including the treatment of the natal kicks which compact stellar remnants acquire during the core collapse of massive stars and the common envelope phase of binary evolution. We discuss the coalescence rates of binary NSs and BHs and prospects for their detections, the formation and evolution of binary WDs and their observational manifestations. Special attention is given to AM CVn-stars — compact binaries in which the Roche lobe is filled by another WD or a low-mass partially degenerate helium-star, as these stars are thought to be the best LISA verification binary GW sources.

The next Galactic supernova is expected to bring great opportunities for the direct detection of gravitational waves (GW), full flavor neutrinos, and multi-wavelength photons. To maximize the science return from such a rare event, it is essential to have established classes of possible situations and preparations for appropriate observations. To this end, we use a long-term numerical simulation of the core-collapse supernova (CCSN) of a 17 solar-mass red supergiant progenitor to self-consistently model the multi-messenger signals expected in GW, neutrino, and electromagnetic messengers. This supernova model takes into account the formation and evolution of a protoneutron star, neutrino-matter interaction, and neutrino transport, all within a two-dimensional shock hydrodynamics simulation. With this, we separately discuss three situations: (i) a CCSN at the Galactic Center, (ii) an extremely nearby CCSN within hundreds of parsecs, and (iii) a CCSN in nearby galaxies within several Mpc. These distance regimes necessitate different strategies for synergistic observations. In a Galactic CCSN, neutrinos provide strategic timing and pointing information. We explore how these in turn deliver an improvement in the sensitivity of GW analyses and help to guarantee observations of early electromagnetic signals. To facilitate the detection of multi-messenger signals of CCSNe in extremely nearby and extragalactic distances, we compile a list of nearby red supergiant candidates and a list of nearby galaxies with their expected CCSN rates. By exploring the sequential multi-messenger signals of a nearby CCSN, we discuss preparations for maximizing successful studies of such an unprecedented stirring event.

In this paper, we obtain the NIRB and SBGWs from the early stars, which are constrained by the observation of reionization and star formation rate. We study the transition from Pop III to Pop II stars via the star formation model of different population, which takes into account the reionization and the metal enrichment evolution. We calculate the two main metal pollution channels arising from the supernova-driven protogalactic outflows and "genetic channel". We obtain the SFRs of Pop III and Pop II and their NIRB and SBGWs radiation. We predict that the upper limit of metallicity in metal-enriched IGM (the galaxies whose polluted via "genetic channel") reaches $Z_{\rm crit}=10^{-3.5}Z_{\odot}$ at $z\sim13$ ($z\sim11$), which is consistent with our star formation model. We constrain on the SFR of Pop III stars from the observation of reionization. The peak intensity of NIRB is about $0.03-0.2~nW m^{-2}{sr}^{-1}$ at $\sim 1 \mu m$ for $z>6$. The prediction of NIRB signal is consistent with the metallicity evolution. We also obtain the gravitational wave background from the black holes formed by these early stars. The predicted gravitational wave background has a peak amplitude of $\Omega_{GW}\simeq8\times10^{-9}$ at $\nu=158$ Hz for Pop II star remnants. However, the background generated by Pop III.2 stars is much less than Pop II stars, with a peak amplitude of $\Omega_{GW}\simeq1.2\times10^{-11}$ at $\nu=28~Hz$. The background of Pop III.1 shifts to lower frequencies, and the amplitude of $\Omega _{GW}$ for Pop III.1 stars shows a minimum value at $\nu\simeq 10$ Hz, due to the lack of gravitational wave signals from the stars with $140~M_{\odot}<M_\ast<260~M_{\odot}$.

We present a theory in Maxwellian form for gravitational waves in a flat background. This requires us to identify the gravitational analogues of the electric and magnetic fields for light. An important novelty, however, is that our analogues are not vector fields but rather rank-two tensor fields; in place of a three-component vector at each point in space, as in electromagnetism, our fields are three by three symmetric matrices at each point. The resulting Maxwell-like equations lead directly to a Poynting theorem for the local energy density associated with a gravitational wave and to associated local properties including densities of momentum and angular momentum.

The inspiral and merger of a binary neutron star (NSNS) can lead to the formation of a hypermassive neutron star (HMNS). As the HMNS loses thermal pressure due to neutrino cooling and/or centrifugal support due to gravitational wave emission, and/or magnetic breaking of differential rotation, it will collapse to a black hole. To assess the importance of shock-induced thermal pressure and cooling, we adopt an idealized equation of state and perform NSNS simulations in full general relativity through late inspiral, merger, and HMNS formation, accounting for cooling. We show that thermal pressure contributes significantly to the support of the HMNS against collapse and that thermal cooling accelerates its ``delayed'' collapse. Our simulations demonstrate explicitly that cooling can induce the catastrophic collapse of a hot hypermassive neutron star formed following the merger of binary neutron stars. Thus, cooling physics is important to include in NSNS merger calculations to accurately determine the lifetime of the HMNS remnant and to extract information about the neutron star equation of state, cooling mechanisms, bar instabilities and B-fields from the gravitational waves emitted during the transient phase prior to black hole formation.