Search for gravitational-wave bursts from soft gamma repeaters

A Gravitational-Wave Perspective on Neutron-Star Seismology

We provide a bird’s-eye view of neutron-star seismology, which aims to probe the extreme physics associated with these objects, in the context of gravitational-wave astronomy. Focussing on the fundamental mode of oscillation, which is an efficient gravitational-wave emitter, we consider the seismology aspects of a number of astrophysically relevant scenarios, ranging from transients (like pulsar glitches and magnetar flares), to the dynamics of tides in inspiralling compact binaries and the eventual merged object and instabilities acting in isolated, rapidly rotating, neutron stars. The aim is not to provide a thorough review, but rather to introduce (some of) the key ideas and highlight issues that need further attention.

Prospects for observing and localizing gravitational-wave transients with Advanced LIGO, Advanced Virgo and KAGRA

We present our current best estimate of the plausible observing scenarios for the Advanced LIGO, Advanced Virgo and KAGRA gravitational-wave detectors over the next several years, with the intention of providing information to facilitate planning for multi-messenger astronomy with gravitational waves. We estimate the sensitivity of the network to transient gravitational-wave signals for the third (O3), fourth (O4) and fifth observing (O5) runs, including the planned upgrades of the Advanced LIGO and Advanced Virgo detectors. We study the capability of the network to determine the sky location of the source for gravitational-wave signals from the inspiral of binary systems of compact objects, that is binary neutron star, neutron star-black hole, and binary black hole systems. The ability to localize the sources is given as a sky-area probability, luminosity distance, and comoving volume. The median sky localization area (90% credible region) is expected to be a few hundreds of square degrees for all types of binary systems during O3 with the Advanced LIGO and Virgo (HLV) network. The median sky localization area will improve to a few tens of square degrees during O4 with the Advanced LIGO, Virgo, and KAGRA (HLVK) network. During O3, the median localization volume (90% credible region) is expected to be on the order of 10 5 , 10 6 , 10 7 Mpc 3 for binary neutron star, neutron star-black hole, and binary black hole systems, respectively. The localization volume in O4 is expected to be about a factor two smaller than in O3. We predict a detection count of 1 - 1 + 12 ( 10 - 10 + 52 ) for binary neutron star mergers, of 0 - 0 + 19 ( 1 - 1 + 91 ) for neutron star-black hole mergers, and 17 - 11 + 22 ( 79 - 44 + 89 ) for binary black hole mergers in a one-calendar-year observing run of the HLV network during O3 (HLVK network during O4). We evaluate sensitivity and localization expectations for unmodeled signal searches, including the search for intermediate mass black hole binary mergers.

Multimessenger Probes of High-energy Sources

Multimessenger observations may hold the key to learn about the most energetic sources in the universe. The recent construction of large scale observatories opened new possibilities in testing non thermal cosmic processes with alternative probes, such as high energy neutrinos and gravitational waves. We propose to combine information from gravitational wave detections, neutrino observations and electromagnetic signals to obtain a comprehensive picture of some of the most extreme cosmic processes. Gravitational waves are indicative of source dynamics, such as the formation, evolution and interaction of compact objects. These compact objects can play an important role in astrophysical particle acceleration, and are interesting candidates for neutrino and in general high-energy astroparticle studies. In particular we will concentrate on the most promising gravitational wave emitter sources: compact stellar remnants. The merger of binary black holes, binary neutron stars or black hole-neutron star binaries are abundant gravitational wave sources and will likely make up the majority of detections. However, stellar core collapse with rapidly rotating core may also be significant gravitational wave emitter, while slower rotating cores may be detectable only at closer distances. The joint detection of gravitational waves and neutrinos from these sources will probe the physics of the sources and will be a smoking gun of the presence of hadrons in these objects which is still an open question. Conversely, the non-detection of neutrinos or gravitational waves from these sources will be fundamental to constrain the hadronic content.

Magnetars: the physics behind observations. A review

Magnetars are the strongest magnets in the present universe and the combination of extreme magnetic field, gravity and density makes them unique laboratories to probe current physical theories (from quantum electrodynamics to general relativity) in the strong field limit. Magnetars are observed as peculiar, burst-active x-ray pulsars, the anomalous x-ray pulsars (AXPs) and the soft gamma repeaters (SGRs); the latter emitted also three 'giant flares', extremely powerful events during which luminosities can reach up to 10(47) erg s(-1) for about one second. The last five years have witnessed an explosion in magnetar research which has led, among other things, to the discovery of transient, or 'outbursting', and 'low-field' magnetars. Substantial progress has been made also on the theoretical side. Quite detailed models for explaining the magnetars' persistent x-ray emission, the properties of the bursts, the flux evolution in transient sources have been developed and confronted with observations. New insight on neutron star asteroseismology has been gained through improved models of magnetar oscillations. The long-debated issue of magnetic field decay in neutron stars has been addressed, and its importance recognized in relation to the evolution of magnetars and to the links among magnetars and other families of isolated neutron stars. The aim of this paper is to present a comprehensive overview in which the observational results are discussed in the light of the most up-to-date theoretical models and their implications. This addresses not only the particular case of magnetar sources, but the more fundamental issue of how physics in strong magnetic fields can be constrained by the observations of these unique sources.

New myotropic and metabotropic actions of pyrokinins in tenebrionid beetles

Pyrokinins are a large family of insect neuropeptides exhibiting pleiotropic activity, but are predominantly myostimulatory hormones. In this study, four pyrokinins Tenmo-PK-1 (HVVNFTPRLa), Tenmo-PK-2 (SPPFAPRLa), Tenmo-PK-3 (HLSPFSPRLa) and Zopat-PK-1 (LPHYPRLa) from the neuro-endocrine system of two tenebrionid beetles, Tenebrio molitor and Zophobas atratus, were tested in homologous bioassays to evaluate their putative myotropic and glycaemic actions. The four investigated bioassays systems (the heart, oviduct, ejaculatory duct and hindgut) revealed species-specific and organ-specific myotropic actions for the pyrokinins tested. In most bioassays with both beetles, the peptides showed myostimulatory properties with different efficacy. However, the T. molitor heart is not sensitive to Tenmo-PK-1, Tenmo-PK-2 and Tenmo-PK-3, and one of the peptides Tenmo-PK-1, is myoinhibitory on the oviduct. Tenmo-PK-2, which is also present in Z. atratus, exerted an inhibitory effect on the contractions of the heart and ejaculatory duct muscles in this beetle. Such myoinhibitory properties of pyrokinins in insects are shown here for the first time. Only one of the peptides tested, Tenmo-PK-2, stimulated a hyperglycaemic response in the haemolymph of larvae of T. molitor and Z. atratus, and this effect suggests a possible additional metabotropic function of this peptide in beetles. The differences in the myotropic and glycaemic responses to pyrokinins suggest that these peptides modulate contractions of muscles from visceral organs and free sugar levels in the haemolymph of the beetles, through complex and species-specific mechanisms.

Gravitational Wave Detection by Interferometry (Ground and Space)

Significant progress has been made in recent years on the development of gravitational-wave detectors. Sources such as coalescing compact binary systems, neutron stars in low-mass X-ray binaries, stellar collapses and pulsars are all possible candidates for detection. The most promising design of gravitational-wave detector uses test masses a long distance apart and freely suspended as pendulums on Earth or in drag-free spacecraft. The main theme of this review is a discussion of the mechanical and optical principles used in the various long baseline systems in operation around the world - LIGO (USA), Virgo (Italy/France), TAMA300 and LCGT (Japan), and GEO600 (Germany/U.K.) - and in LISA, a proposed space-borne interferometer. A review of recent science runs from the current generation of ground-based detectors will be discussed, in addition to highlighting the astrophysical results gained thus far. Looking to the future, the major upgrades to LIGO (Advanced LIGO), Virgo (Advanced Virgo), LCGT and GEO600 (GEO-HF) will be completed over the coming years, which will create a network of detectors with the significantly improved sensitivity required to detect gravitational waves. Beyond this, the concept and design of possible future "third generation" gravitational-wave detectors, such as the Einstein Telescope (ET), will be discussed.

Absence of TRIF signaling in lipopolysaccharide-stimulated murine mast cells

In macrophages, two signaling pathways, dependent on MyD88 or TIR domain-containing adaptor-inducing IFN-β (TRIF) signaling, emanate from the LPS receptor TLR4/MD-2. In this study, we show that in murine bone marrow-derived mast cells (BMMCs), only the MyD88-dependent pathway is activated by LPS. The TRIF signaling branch leading both to NF-κB activation and enhanced proinflammatory cytokine production, as well as to IRF3 activation and subsequent IFN-β production, is absent in LPS-stimulated BMMCs. IRF3 activation is also absent in peritoneal mast cells from LPS-injected mice. We observed strongly diminished TRAM expression in BMMCs, but overexpression of TRAM only moderately enhanced IL-6 and did not boost IFN-β responses to LPS in these cells. A combination of very low levels of TRAM and TLR4/MD-2 with the known absence of membrane-bound CD14 are expected to contribute to the defective TRIF signaling in mast cells. We also show that, unlike in macrophages, in BMMCs the TRIF-dependent and -independent IFN-αβ responses to other recognized IFN inducers (dsRNA, adenovirus, and B-DNA) are absent. These results show how the response to the same microbial ligand using the same receptor can be regulated in different cell types of the innate immune system.

Unobtrusive interferometer tracking by path length oscillation for multidimensional spectroscopy

We track the path difference between interferometer arms with few-nanometer accuracy without adding optics to the beam path. We measure the interference of a helium-neon beam that copropagates through the interferometer with midinfrared pulses used for multidimensional spectroscopy. This can indicate motion, but not direction. By oscillating the path length of one arm with a mirror on a piezoelectric stack and monitoring the oscillations of the recombined helium-neon beam, the direction can be calculated, and the path delay can be continuously tracked.

Gravitational wave forms for two- and three-body gravitating systems

Different numbers of self-gravitating particles (in different types of periodic motion) are most likely to generate very different shapes of gravitational waves, some of which, however, can be accidentally almost the same. One such example is a binary and three-body system for Lagrange's solution. To track the evolution of these similar wave forms, we define a chirp mass to the triple system. Thereby, we show that the quadrupole wave forms cannot distinguish the sources. It is suggested that wave forms with higher lth multipoles will be important for classification of them (with a conjecture of l<or=N for N particles).

Breaking strain of neutron star crust and gravitational waves

Mountains on rapidly rotating neutron stars efficiently radiate gravitational waves. The maximum possible size of these mountains depends on the breaking strain of the neutron star crust. With multimillion ion molecular dynamics simulations of Coulomb solids representing the crust, we show that the breaking strain of pure single crystals is very large and that impurities, defects, and grain boundaries only modestly reduce the breaking strain to around 0.1. Because of the collective behavior of the ions during failure found in our simulations, the neutron star crust is likely very strong and can support mountains large enough so that their gravitational wave radiation could limit the spin periods of some stars and might be detectable in large-scale interferometers. Furthermore, our microscopic modeling of neutron star crust material can help analyze mechanisms relevant in magnetar giant flares and microflares.