Showing papers by "John M. Blondin published in 2022"

Phase-resolved spectroscopic analysis of the eclipsing black hole X-ray binary M33 X-7: System properties, accretion, and evolution

Abstract: M33X-7 is the only known eclipsing black hole high mass X-ray binary. The system is reported to contain a very massive O supergiant donor and a massive black hole in a short orbit. The high X-ray luminosity and its location in the metal-poor galaxy M33 make it a unique laboratory for studying the winds of metal-poor donor stars with black hole companions and it helps us to understand the potential progenitors of black hole mergers. Using phase-resolved simultaneous HST - and XMM-Newton -observations, we traced the interaction of the stellar wind with the black hole. We observed a strong Hatchett-McCray e ff ect in M33X-7 for the full range of wind velocities. Our comprehensive spectroscopic investigation of the donor star (X-ray + UV + optical) yields new stellar and wind parameters for the system that di ff er significantly from previous estimates. In particular, the masses of the components are considerably reduced to ≈ 38 M (cid:12) for the O-star donor and ≈ 11 . 4 M (cid:12) for the black hole. The O giant is overfilling its Roche lobe and shows surface He enrichment. The donor shows a densely clumped wind with a mass-loss rate that matches theoretical predictions. An extended ionization zone is even present during the eclipse due to scattered X-ray photons. The X-ray ionization zone extends close to the photosphere of the donor during inferior conjunction. We investigated the wind-driving contributions from di ff erent ions and the changes in the ionization structure due to X-ray illumination. Toward the black hole, the wind is strongly quenched due to strong X-ray illumination. For this system, the standard wind-fed accretion scenario alone cannot explain the observed X-ray luminosity, pointing toward an additional mass overflow, which is in line with our acceleration calculations. The X-ray photoionization creates an He ii emission region around the system emitting ∼ 10 47 phs − 1 . We computed binary evolutionary tracks for the system using MESA. Currently, the system is transitioning toward an unstable mass transfer phase, possibly resulting in a common envelope of the black hole and the O-star donor. Since the mass ratio is q (cid:38) 3.3 and the period is short, the system is unlikely to survive the common envelope, but will rather merge.

Core Collapse Supernova Gravitational Wave Emission for Progenitors of 9.6, 15, and 25 Solar Masses

Abstract: We present gravitational wave emission predictions based on three core collapse supernova simulations corresponding to three different progenitor masses. The masses span a large range, between 9.6 and 25 Solar masses, are all initially non-rotating, and are of two metallicities: zero and Solar. We compute both the temporal evolution of the gravitational wave strains for both the plus and the cross polarizations, as well as their spectral decomposition and characteristic strains.

Use of Telemedicine for Postdischarge Assessment of the Surgical Wound

Abstract: Objective: This study aimed to determine whether remote wound reviews using telemedicine can be safely upscaled, and if standardized assessment tools are needed. Background: Surgical site infection (SSI) is the most common complication of surgery worldwide, and frequently occurs after hospital discharge. Evidence to support implementation of telemedicine during postoperative recovery will be an essential component of pandemic recovery. Methods: The primary outcome of this study was SSI reported up to 30 days after surgery (SSI), comparing rates reported using telemedicine (telephone and/or video assessment) to those with in-person review. The first part of this study analyzed primary data from an international cohort study of adult patients undergoing abdominal surgery who were discharged from hospital before 30 days after surgery. The second part combined this data with the results of a systematic review to perform a meta-analysis of all available data conducted in accordance with PRIMSA guidelines (PROSPERO:192596). Results: The cohort study included 15,358 patients from 66 countries (8069 high, 4448 middle, 1744 low income). Of these, 6907 (45.0%) were followed up using telemedicine. The SSI rate reported using telemedicine was slightly lower than with in-person follow-up (13.4% vs 11.1%, P<0.001), which persisted after risk adjustment in a mixed-effects model (adjusted odds ratio: 0.73, 95% confidence interval: 0.63–0.84, P<0.001). This association was consistent across sensitivity and subgroup analyses, including a propensity-score matched model. In 9 eligible nonrandomized studies identified, a pooled mean of 64% of patients underwent telemedicine follow-up. Upon meta-analysis, the SSI rate reported was lower with telemedicine (odds ratio: 0.67, 0.47–0.94) than in-person (reference) follow-up (I 2=0.45, P=0.12), although there a high risk of bias in included studies. Conclusions: Use of telemedicine to assess the surgical wound postdischarge is feasible, but risks underreporting of SSI. Standardized tools for remote assessment of SSI must be evaluated and adopted as telemedicine is upscaled globally.