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

Do Pressure Requirements Change over time with Auto titrating Positive Airway Pressure Therapy for Obstructive Sleep Apnea?

Study Objective: Prior studies have demonstrated reduced inflammation after chronic use of CPAP therapy. This may lead to reduced pressures over time as the upper airway becomes more compliant. We sought to determine if there was a reduction in 90th percentile pressure requirements in patients on Auto PAP for OSA. Methods: A retrospective chart review of 988 patients who underwent a sleep study at our sleep center was performed. Those with moderate to severe sleep apnea who were prescribed and compliant with Respironics Auto PAP were included, yielding a total of 46 patients for analysis. All statistical analysis analyses were performed using in SAS version 9.3. Results: Mean age of patients was 57.20 years and majority was male. Mean baseline AHI was 43.10. Mean follow up interval was 9.99 months. There was a trend towards decrease in pressure requirements over time, with a mean change of 0.46 cmH20 which was not significant. Patients with a baseline AHI ≥ 50 had a greater decrease in pressure requirements upon follow-up compared to those with an AHI Conclusions: Our study demonstrated that 90th percentile pressure decreased over time with continuous use of Auto CPAP in patients with severe OSA (AHI \u3e50) and in patients who lost weight. BRIEF SUMMARY: Study Rationale: Few previous studies have shown that chronic CPAP use may be lead to reduced upper airway inflammation and edema. We hypothesized that this may lead to reduced pressure requirements over time as the upper airway becomes more compliant. However, there have been no studies that have studied change in pressure requirements with Auto PAP treatment in patients not undergoing bariatric surgery. STUDY IMPACT: There was no significant change in pressure requirements for patients with moderate to severe OSA treated with Auto PAP, after a mean follow up interval of 10 months. On subgroup analysis, patients with a baseline AHI ≥ 50 (severe OSA) had a greater decrease in pressure compared to those with an AHI(non-severe OSA), potentially because they tend to lose weight on Auto CPAP while those with AHIOSA