Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

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

Abstract: 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 105, 106, 107Mpc3 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

Multi-messenger Observations of a Binary Neutron Star Merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ∼ 1.7 {{s}} with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of {40}-8+8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 {M}ȯ . An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ∼ 40 {{Mpc}}) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ∼10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ∼ 9 and ∼ 16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC 4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta.</p

Effects of Mitoxantrone on Excitation-Contraction Coupling in Guinea Pig Ventricular Myocytes 1

ABSTRACT The mechanisms of the inotropic effect of mitoxantrone (MTO), a synthetic dihydroxyanthracenedione derivative with antineoplastic activity, was investigated in guinea pig ventricular myocytes using whole-cell patch-clamp methods combined with fura-2 fluorescence and cell-edge tracking techniques. In right ventricular papillary muscles, 30 M MTO increased isometric force of contraction as well as action potential duration (APD) in a time-dependent manner. The force of contraction was increased approximately 3-fold within 4 h. This positive inotropic effect was accompanied by a prolongation of time to peak force and relaxation time. In current-clamped single myocytes treated with 30 M MTO for 30 min, an increase of cell shortening by 77% and a prolongation of APD by 19% was observed. Peak amplitude of the intracellular Ca 2ϩ transients was also increased by 10%. The contribution of APD prolongation to the enhancement of cell shortening induced by MTO was assessed by clamping control myocytes with action potentials of various duration. Prolongation of APD 90 (ADP measured at 90% of repolarization) by 24% led to an increase of cell shortening by 13%. When the cells were clamped by an action potential with constant APD, MTO still caused an increase of cell shortening by 59% within 30 min. No increase of the peak intracellular Ca 2ϩ transients, however, was observed under this condition. We conclude that both the APD prolongation and a direct interaction with the contractile proteins contributed to the positive inotropic effect of MTO

Rapid vibrational imaging with sum frequency generation microscopy.

We demonstrate rapid vibrational imaging based on sum frequency generation (SFG) microscopy with a collinear excitation geometry. Using the tunable picosecond pulses from a high-repetition-rate optical parametric oscillator, vibrationally selective imaging of collagen fibers is achieved with submicrometer lateral resolution. We furthermore show simultaneous SFG and second harmonic generation imaging to emphasize the compatibility of the microscope with other nonlinear optical modalities

Rapid vibrational imaging with sum frequency generation microscopy

We demonstrate rapid vibrational imaging based on sum frequency generation (SFG) microscopy with a collinear excitation geometry. Using the tunable picosecond pulses from a high-repetition-rate optical parametric oscillator, vibrationally selective imaging of collagen fibers is achieved with submicrometer lateral resolution. We furthermore show simultaneous SFG and second harmonic generation imaging to emphasize the compatibility of the microscope with other nonlinear optical modalities. © 2011 Optical Society of America OCIS codes: 180.4315, 190.4223. Sum frequency generation is a second-order nonlinear optical response that is exclusively sensitive to noncentrosymmetric media, which are usually provided by systems with nonsymmetric local structure or at symmetry breaking interfaces between different materials Unlike related vibrationally sensitive nonlinear imaging techniques, such as coherent anti-Stokes Raman scattering and stimulated Raman scattering, the VR-SFG approach requires mid-IR laser radiation to vibrationally address the material. Mid-IR radiation from low repetition rate (Hz-kHz), high pulse energy (μJ-mJ) laser systems used in VR-SFG microscopes In this work, we demonstrate a VR-SFG microscope that overcomes many of the existing shortcomings of this imaging technique. We have improved the VR-SFG microscope in two ways. First, we have used a high-repetition picosecond optical parametric oscillator (OPO) as the light source. Unlike low-repetition-rate laser systems, this source provides pulse energies that are sufficiently low for focusing the beams to diffraction-limited spots without damaging the sample, while at the same time maximizing signal yield due to the high pulse repetition rate. In addition, the spectral pulse width ensures a maximized signal to nonresonant background ratio. Furthermore, the light source delivers both the mid-IR and the near-IR pulses for the VR-SFG interaction, which form an intrinsically synchronized pulse pair. Second, we have adopted a collinear excitation geometry. Other than previous collinear implementation

Pregnancy switches adrenergic signal transduction in rat and human uterine myocytes as probed by BKCa channel activity

We used large conductance Ca2+-activated K+ (BKCa) channel activity as a probe to characterize the inhibitory/stimulatory G protein (Gi/Gs) signalling pathways in intact cells from pregnant (PM) and non-pregnant (NPM) myometrium.Isoprenaline (10 μM) enhanced the outward current (Iout) in PM cells and inhibited Iout in NPM cells. Additional application of the α2-adrenoceptor (α2-AR) agonist clonidine (10 μM) further enhanced the isoprenaline-modulated Iout in PM cells but partially antagonized Iout in NPM cells. Clonidine alone did not affect Iout. The specific cAMP kinase (PKA) inhibitor H-89 (1 μM) abolished the effects of isoprenaline and clonidine. The specific BKCa channel blocker iberiotoxin (0·1 μM) inhibited Iout by ≈80 %; the residual current was insensitive to isoprenaline.Inhibition of Gi activity by either pertussis toxin or the GTPase activating protein RGS16 abolished inhibitory as well as stimulatory effects of clonidine on Iout.Transducin-α, a scavenger of Gi βγ dimers, converted the stimulatory action of clonidine on Iout into an inhibitory effect. Free transducin-βγ enhanced both the stimulatory and the inhibitory effects of isoprenaline on Iout.The results demonstrate that BKCa channel activity is a sensitive probe to follow adenylyl cyclase–cAMP–PKA signalling in myometrial smooth muscle cells. Both Giα-mediated inhibition and Giβγ-mediated stimulation can occur in the same cell, irrespective of pregnancy. It is speculated that the coupling between α2-AR and Gi proteins is more efficient during pregnancy and that Giβγ at high levels simply override the inhibitory action of Gi α