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

Observation of the Gamma-Ray Binary HESS J0632+057 with the HESS, MAGIC, and VERITAS Telescopes

The results of gamma-ray observations of the binary system HESS J0632 + 057 collected during 450 hr over 15 yr, between 2004 and 2019, are presented. Data taken with the atmospheric Cherenkov telescopes H.E.S.S., MAGIC, and VERITAS at energies above 350 GeV were used together with observations at X-ray energies obtained with Swift-XRT, Chandra, XMM-Newton, NuSTAR, and Suzaku. Some of these observations were accompanied by measurements of the H alpha emission line. A significant detection of the modulation of the very high-energy gamma-ray fluxes with a period of 316.7 +/- 4.4 days is reported, consistent with the period of 317.3 +/- 0.7 days obtained with a refined analysis of X-ray data. The analysis of data from four orbital cycles with dense observational coverage reveals short-timescale variability, with flux-decay timescales of less than 20 days at very high energies. Flux variations observed over a timescale of several years indicate orbit-to-orbit variability. The analysis confirms the previously reported correlation of X-ray and gamma-ray emission from the system at very high significance, but cannot find any correlation of optical H alpha parameters with fluxes at X-ray or gamma-ray energies in simultaneous observations. The key finding is that the emission of HESS J0632 + 057 in the X-ray and gamma-ray energy bands is highly variable on different timescales. The ratio of gamma-ray to X-ray flux shows the equality or even dominance of the gamma-ray energy range. This wealth of new data is interpreted taking into account the insufficient knowledge of the ephemeris of the system, and discussed in the context of results reported on other gamma-ray binary systems

GROWTH DIFFERENTIATION FACTOR 5 IS A PARACRINE REGULATOR IN SARCOPENIC OBESITY

Landen W. Saling1, Eleanor R. Schrems1, Seongkyun Lim1, Francielly Morena da Silva1, Ana Regina Cabrera1, Kevin A. Murach1, Nicholas P. Greene1, FACSM, Tyrone A. Washington1 1University of Arkansas, Fayetteville, Arkansas Sarcopenic obesity (SO) differentiates itself from sarcopenia and obesity by exhibiting a more detrimental and complex condition that increases the risk of mortality. Sarcopenic obese individuals suffer from greater physical disability and muscle weakness than sarcopenic and obese individuals alone. In addition, altered cellular signaling that regulates increased muscle loss in SO is largely unknown. Identifying key differentially expressed genes in SO muscle are important for future investigation and the creation of therapeutics and strategies aimed at attenuating or preventing muscle loss. PURPOSE: To examine global gene expression in muscle of SO mice to determine differentially expressed (DE) genes. METHODS: After weaning, twenty-four mice were randomly assigned to young (3-4 months old) or aged (22-24 months old) groups and then randomly assigned to either a high-fat (HFD, 60% fat) or normal chow (NC, 14% fat) diet. RNA was isolated from the plantaris muscle and Next Generation RNA sequencing was conducted to determine DE genes among experimental groups. Log2 Fold Change (Log2FC) ≥ 0.6, Log2FC ≤ -0.6 and p ≤ 0.05 were the criteria used to determine significant DE genes. Real-Time Polymerase Chain Reaction was used to confirm mRNA abundance of DE genes. RESULTS: Aged-HFD mice had an ̴ 39-49% (p ≤ 0.05) reduction in plantaris to body mass ratio compared to all other groups. CYP1A1, RAB15, and CDH22 showed significant main effects (p ≤ 0.05) for diet. Age and diet interacted to alter SMOX and GDF5 mRNA abundance. There was a ̴ 26-fold increase (p ≤ 0.05) in GDF-5 mRNA abundance in the aged-HFD mice compared to all other groups. CONCLUSION: GDF-5 is associated with TGF-β and SMAD signaling. The increased GDF-5 mRNA abundance seen in SO mice could be promoting increased collagen deposition within skeletal muscle affecting muscle function. These findings show that GDF5 may play a key role in altered cellular signaling and muscle atrophy in SO muscle. ACKNOWLEDGEMENTS: This study was funded by the Arkansas Bioscience Institute, the major research component of the Arkansas Tobacco Settlement Proceeds Act of 2000