Mass Donor Research Articles

The Complex Field Theory and Mass Formation—An Alternative Model to Higgs Mechanism

The electromagnetic force, strong nuclear force, weak nuclear force, and gravitational force are the four fundamental forces of nature. The Standard Model (SM) succeeded in combining the first three forces to describe the most basic building blocks of matter and govern the universe. Despite the model’s great success in resolving many issues in particle physics but still has several setbacks and limitations. The model failed to incorporate the fourth force of gravity. It infers that all fermions and bosons are massless contrary to experimental facts. In addition, the model addresses neither the 95% of the universe’s energy of Dark Matter (DM) and Dark Energy (DE) nor the universe’s expansion. The Complex Field Theory (CFT) identifies DM and DE as complex fields of complex masses and charges that encompasses the whole universe, and pervade all matter. This presumption resolves the issue of failing to detect DM and DE for the last five decades. The theory also presents a model for the universe’s expansion and presumes that every material object carries a fraction of this complex field proportional to its mass. These premises clearly explain the physical nature of the gravitational force and its complex field and pave the way for gravity into the SM. On the other hand, to solve the issue of massless bosons and fermions in the SM, Higgs mechanism introduces a pure and abstractive theoretical model of unimaginable four potentials to generate fictitious bosons as mass donors to fermions and W± and Z bosons. The CFT in this paper introduces, for the first time, a physical explanation to the mystery of the mass formation of particles rather than Higgs’ pure mathematical derivations. The analyses lead to uncovering the mystery of electron-positron production near heavy nuclei and never in a vacuum. In addition, it puts a constraint on Einstein’s mass-energy equation that energy can never be converted to mass without the presence of dense dark matter and cannot be true in a vacuum. Furthermore, CFT provides different perspectives and resolves real-world physics concepts such as the nuclear force, Casimir force, Lamb’s shift, and the anomalous magnetic moment to be published elsewhere.

Gamma Cas Stars as Be+White Dwarf Binary Systems

The origin of the bright and hard X-ray emission flux among the γ Cas subgroup of B-emission line (Be) stars may be caused by gas accretion onto an orbiting white dwarf (WD) companion. Such Be+WD binaries are the predicted outcome of a second stage of mass transfer from a helium star mass donor to a rapidly rotating mass gainer star. The stripped donor stars become small and hot white dwarfs that are extremely faint compared to their Be star companions. Here we discuss model predictions about the physical and orbital properties of Be+WD binaries, and we show that current observational results on γ Cas systems are consistent with the expected large binary frequency, companion faintness and small mass, and relatively high mass range of the Be star hosts. We determine that the companions are probably not stripped helium stars (hot subdwarf sdO stars), because these are bright enough to detect in ultraviolet spectroscopy, yet their spectroscopic signatures are not observed in studies of γ Cas binaries. Interferometry of relatively nearby systems provides the means to detect very faint companions including hot subdwarf and cooler main-sequence stars. Preliminary observations of five γ Cas binaries with the CHARA Array interferometer show no evidence of the companion flux, leaving white dwarfs as the only viable candidates for the companions.

Low mass X-ray binary simulation data release

We present DABS (Database of Accreting Binary Simulations), an open-access database of modelled Low Mass X-ray Binaries (LMXBs). DABS has been created using evolutionary tracks of neutron star and black hole LMXBs, spanning a large set of initial conditions for the accretor mass, donor mass, and orbital period. The LMXBs are evolved with the Convection and Rotation Boosted Magnetic Braking prescription. The most important asset of this online database is the tool PEAS (Progenitor Extractor for Accreting Systems). This tool can be used to predict the progenitors of any user-entered LMXB system and view their properties before the start of mass transfer. This prediction can facilitate preliminary searches for the progenitors of observed LMXBs, which can help in streamlining further detailed analyses. The PEAS tool can also be used to constrain population synthesis techniques that specialize in supernova kicks in binaries and common envelope outcomes.

Robust Inference of Neutron-star Parameters from Thermonuclear Burst Observations

Thermonuclear (type-I) bursts arise from unstable ignition of accumulated fuel on the surface of neutron stars in low-mass X-ray binaries. Measurements of burst properties in principle enable observers to infer the properties of the host neutron star and mass donors, but a number of confounding astrophysical effects contribute to systematic uncertainties. Here we describe some commonly used approaches for determining system parameters, including composition of the burst fuel, and introduce a new suite of software tools, concord, intended to fully account for astrophysical uncertainties. The comparison of observed burst properties with the predictions of numerical models is a complementary method of constraining host properties, and the tools presented here are intended to make comprehensive model-observation comparisons straightforward. When combined with the extensive samples of burst observations accumulated by X-ray observatories, these software tools will provide a step change in the amount of information that can be inferred about typical burst sources.

White Dwarf—Red Giant Star Binaries as Type Ia Supernova Progenitors: With and without Magnetic Confinement

Various white-dwarf (WD) binary scenarios have been proposed trying to understand the nature and the diversity of type Ia supernovae (SNe Ia). In this work, we study the evolution of carbon–oxygen WD—red giant (RG) binaries (including the role of magnetic confinement) as possible SN Ia progenitors (the so-called symbiotic progenitor channel). Using the mesa stellar evolution code, we calculate the time dependence of the structure of the RG star, the wind mass loss, the Roche lobe-overflow mass-transfer rate, the polar mass-accretion rate (in the case of magnetic confinement), and the orbital and angular-momentum evolution. We consider cases where the WD is nonmagnetic and cases where the magnetic field is strong enough to force accretion onto the two small polar caps of the WD. Confined accretion onto a small area allows for more efficient hydrogen burning, potentially suppressing nova outbursts. This makes it easier for the WD to grow in mass toward the Chandrasekhar-mass limit and explode as a SN Ia. With magnetic confinement, the initial parameter space of the symbiotic channel for SNe Ia is shifted toward shorter orbital periods and lower donor masses compared to the case without magnetic confinement. Searches for low-mass He WDs or relatively low-mass giants with partially stripped envelopes that survived the supernova explosion and are found in SN remnants will provide crucial insights for our understanding of the contribution of this symbiotic channel.

Two decades of optical timing of the shortest-period binary star system HM Cancri

ABSTRACT The shortest-period binary star system known to date, RX J0806.3+1527 (HM Cancri), has now been observed in the optical for more than two decades. Although it is thought to be a double degenerate binary undergoing mass transfer, an early surprise was that its orbital frequency, f0, is currently increasing as the result of gravitational wave radiation. This is unusual since it was expected that the mass donor was degenerate and would expand on mass loss, leading to a decreasing f0. We exploit two decades of high-speed photometry to precisely quantify the trajectory of HM Cancri, allowing us to find that $\ddot{f}_0$ is negative, where $\ddot{f}_0~=~(-5.38\pm 2.10)\times 10^{-27}$ Hz s−2. Coupled with our positive frequency derivative, we show that mass transfer is counteracting gravitational-wave dominated orbital decay and that HM Cancri will turn around within 2100 ± 800 yr from now. We present Hubble Space Telescope ultra-violet spectra which display Lyman-α absorption, indicative of the presence of hydrogen accreted from the donor star. We use these pieces of information to explore a grid of permitted donor and accretor masses with the Modules for Experiments in Stellar Astrophysics suite, finding models in good accordance with many of the observed properties for a cool and initially hydrogen-rich extremely low mass white dwarf (≈0.17 M⊙) coupled with a high-accretor mass white dwarf (≈1.0 M⊙). Our measurements and models affirm that HM Cancri is still one of the brightest verification binaries for the Laser Interferometer Space Antenna spacecraft.

A synthetic population of Wolf-Rayet stars in the LMC based on detailed single and binary star evolution models

Context. Without a doubt, mass transfer in close binary systems contributes to the populations ofWolf-Rayet (WR) stars in the MilkyWay and the Magellanic Clouds. However, the binary formation channel is so far not well explored. Aims. We want to remedy this by exploring large grids of detailed binary and single star evolution models computed with the publicly available MESA code, for a metallicity appropriate for the Large Magellanic Cloud (LMC). Methods. The binary models were calculated through Roche-lobe overflow and mass transfer, until the initially more massive star exhausted helium in its core. We distinguish models of WR and helium stars based on the estimated stellar wind optical depth. We used these models to build a synthetic WR population, assuming constant star formation. Results. Our models can reproduce the WR population of the LMC to significant detail, including the number and luminosity functions of the main WR subtypes. We find that for binary fractions of 100% (50%), all LMC WR stars below 106 L⊙ (105.7 L⊙) are stripped binary mass donors. We also identify several insightful mismatches. With a single star fraction of 50%, our models produce too many yellow supergiants, calling either for a larger initial binary fraction, or for enhanced mass loss near the Humphreys-Davidson limit. Our models predict more long-period WR binaries than observed, arguably due to an observational bias toward short periods. Our models also underpredict the shortest-period WR binaries, which may have implications for understanding the progenitors of double black hole mergers. Conclusions. The fraction of binary-produced WR stars may be larger than often assumed and outline the risk to miscalibrate stellar physics when only single star models are used to reproduce the observed WR stars.

The spins of stripped B stars support magnetic internal angular momentum transport

In order to predict the spins of stellar remnants we need to understand the evolution of the internal rotation of stars, and to identify at which stage the rotation of the contracting cores of evolved stars decouples from their expanding envelopes. The donor stars of mass transferring binaries lose almost their entire envelope and may thus offer a direct view on their core rotation. After the mass transfer event they contract and fade rapidly, although they are well observable when caught in the short-lived B-star phase. The B-type primary of the galactic binary system LB-1, which was originally suggested to contain a massive black hole, is nicely explained as a stripped star accompanied by a fainter Be star. The narrow absorption lines in the primary’s spectrum signify extremely slow rotation, atypical of B-type main-sequence stars. Here we investigate the evolution of mass donors in generic grids of detailed binary evolution models, where both stars include differential rotation, internal angular momentum transport, and spin-orbit coupling. Whereas the mass gainers are typically spun-up during the mass transfer, we find that the spins of the stripped donor models depend sensitively on the employed mechanism for internal angular momentum transport. Purely hydrodynamic transport cannot explain the observed slow rotation, while models including magnetic angular momentum transport are able to reproduce the observed rotation of LB-1 and similar stars, independent of the initial rotation rate. In such models the spin of the white dwarfs that emerge at the end of the evolution is independent of the mass stripping. We find evidence that the mass transfer in LB-1 was moderately non-conservative.

On Variation Mechanisms in Recurrent Nova IM Normae

Light curves by Woudt and Warner (WW) of recurrent nova IM Nor show eclipse-like dips that they saw as too wide for eclipses alone, and interpreted as mainly a reflection effect due to irradiation of the companion (mass donor) star with some amplitude increase due to eclipse of IM Nor’s disk. A mainly reflection interpretation cannot be made to work because reflection does not produce dips over a restricted phase range but a somewhat distorted sinusoid that extends over the entire orbital cycle. Here, the dip features are interpreted in two ways, with testing via quantitative light curve modeling that includes an equipotential disk. One way is as alternating eclipses of and by the disk that surrounds this cataclysmic variable’s accreting white dwarf, rather than purely a succession of disk-by-star eclipses. WW’s estimated period of 0.d1026 was accordingly doubled to 0.d2052, with the observed dips now half of their previous width in phase, and with the modeled eclipses matching the observed dips in width and shape. In the 2nd interpretation, a toroidal disk’s capability to produce very wide eclipses is demonstrated computationally. Furthermore, much of the perceived eclipse width can be recognized as an apparent effect due to tidal stretching of the companion star and the disk. In overview, disk eclipses and tidal variation combine with reflection to produce a light curve waveform of approximately the observed shape and duration. Eclipses, tides, and reflection all have essential roles in the 2nd interpretation and no change from WW’s period is needed. Radial velocity observations will be crucial for identification of the correct resolution of the ”excessively wide eclipse” problem.

MAXI J1957+032: a new accreting millisecond X-ray pulsar in an ultra-compact binary

ABSTRACT The detection of coherent X-ray pulsations at ∼314 Hz (3.2 ms) classifies MAXI J1957+032 as a fast-rotating, accreting neutron star. We present the temporal and spectral analysis performed using NICER observations collected during the latest outburst of the source. Doppler modulation of the X-ray pulsation revealed the ultra-compact nature of the binary system characterized by an orbital period of ∼1 h and a projected semimajor axis of 14 lt-ms. The neutron star binary mass function suggests a minimum donor mass of 1.7 × 10−2 M⊙, assuming a neutron star mass of 1.4 M⊙ and a binary inclination angle lower than 60 deg. This assumption is supported by the lack of eclipses or dips in the X-ray light curve of the source. We characterized the 0.5–10 keV energy spectrum of the source in outburst as the superposition of a relatively cold black-body-like thermal emission compatible with the emission from the neutron star surface and a Comptonization component with photon index consistent with a typical hard state. We did not find evidence for iron K α lines or reflection components.

Evolution of AM CVn Binaries with White Dwarf Donors

The evolution and the stability of mass transfer of CO+He white dwarf (WD) binaries are not well understood. Observationally they may emerge as AM CVn binaries and are important gravitational wave (GW) emitters. In this work, we have modeled the evolution of double WD binaries with accretor masses of 0.50–1.30 M ⊙ and donor masses of 0.17–0.45 M ⊙ using the detailed stellar evolution code mesa. We find that the evolution of binaries with same donor masses but different accretor masses is very similar and binaries with same accretor masses but larger He donor masses have larger maximum mass transfer rates and smaller minimum orbital periods. We also demonstrate that the GW signal from AM CVn binaries can be detected by spaceborne GW observatories, such as LISA and TianQin. There is a linear relation between the donor mass and gravitational wave frequency during the mass transfer phase. In our calculation, all binaries can have dynamically stable mass transfer, which is very different from previous studies. The threshold donor mass of Eddington-limited mass transfer for a given accretor WD mass is lower than previous studies. Assuming that a binary may enter a common envelope if the mass transfer rate exceeds the maximum stable burning rate of He, we provide a new criterion for double WDs surviving mass transfer, which is below the threshold of the Eddington limit. Finally, we find that some systems with oxygen–neon (ONe) WDs in our calculation may evolve into detached binaries consisting of neutron stars and extremely low-mass He WDs, and further ultracompact X-ray binaries.

SRGA J181414.6-225604: A New Galactic Symbiotic X-Ray Binary Outburst Triggered by an Intense Mass-loss Episode of a Heavily Obscured Mira Variable

We present the discovery and multiwavelength characterization of SRGA J181414.6-225604, a Galactic hard X-ray transient discovered during the ongoing SRG/ART-XC sky survey. Using data from the Palomar Gattini-IR survey, we identify a spatially and temporally coincident variable infrared (IR) source, IRAS 18111-2257, and classify it as a very-late-type (M7–M8), long-period (1502 ± 24 days), and luminous (M K ≈ −9.9 ± 0.2) O-rich Mira donor star located at a distance of ≈14.6+2.9 −2.3 kpc. Combining multicolor photometric data over the last ≈25 yr, we show that the IR counterpart underwent a recent (starting ≈800 days before the X-ray flare) enhanced mass-loss (reaching ≈2.1 × 10−5 M ⊙ yr−1) episode, resulting in an expanding dust shell obscuring the underlying star. Multi-epoch follow-up observations from Swift, NICER, and NuSTAR reveal a ≈200 day long X-ray outburst reaching a peak luminosity of L X ≈ 2.5 × 1036 erg s−1, characterized by a heavily absorbed (N H ≈ 6 × 1022 cm−2) X-ray spectrum consistent with an optically thick Comptonized plasma. The X-ray spectral and timing behavior suggest the presence of clumpy wind accretion, together with a dense ionized nebula overabundant in silicate material surrounding the compact object. Together, we show that SRGA J181414.6-225604 is a new symbiotic X-ray binary in outburst, triggered by an intense dust-formation episode of a highly evolved donor. Our results offer the first direct confirmation for the speculated connection between enhanced late-stage donor mass loss and the active lifetimes of symbiotic X-ray binaries.

Measures of social support for blood donors during the formation of the donor movement in the USSR

Introduction. The period of formation of the donor community in the USSR fell on the 30–40s of the twentieth century. The first measures to organize the donor community were of a spontaneous nature. However, beginning in the 1930’s, with the support of the state and public organizations in the USSR, on the eve of the war, a mass donor community arose based on the ideology of the time and system of motivations.Aim — to reconstruct the measures of social support for blood donors, which contributed to the formation of the donor community in the USSR and to identify the role of the state in organizing the donor community in the USSR.Main findings. To conduct the study, a set of methods was used, including the study and generalization of experience based on archival sources, monographic description, and narrative analysis. A number of archival materials are introduced into scientific circulation for the first time. Decrees of the Council of People’s Commissars of the RSFSR, issued in the 30–40s of the 20th century, which formed the basis of the legal framework for organizing social support for donors, are given. This article is devoted to the emergence and development of the donor community in the USSR. A number of measures of social support for blood donors are described, which are characteristic of various stages in the development of the donor community (“attracting and retaining” donors in the 1930s, “survival” of donors at the beginning of the Great Patriotic War, and their “encouragement” at the final stage of the Great Patriotic War). Measures of social support for blood donors, which arose in the pre-war period, proved their effectiveness (attracting about 5.5 million people into the ranks of donors, from whom 1.7 million liters of blood were harvested) during the Great Patriotic War, and with some changes, maintain their relevance today.

Partial-envelope stripping and nuclear-timescale mass transfer from evolved supergiants at low metallicity

Stable mass transfer from a massive post-main sequence (post-MS) donor is thought to be a short-lived event of thermal-timescale mass transfer (∼10−3 M⊙ yr−1) which within ≲104 yr strips the donor star of nearly its entire H-rich envelope, producing a hot, compact helium star. This long-standing picture is based on stellar models with rapidly expanding Hertzprung gap (HG) donor stars. Motivated by a finding that in low-metallicity binaries, post-MS mass transfer may instead be initiated by donors already at the core-helium burning (CHeB) stage, we used the MESA stellar-evolution code to compute grids of detailed massive binary models at three metallicities: those of the Sun, the Large Magellanic Cloud (LMC, ZFe; LMC/ZFe; ⊙ ≈ 0.36), and the Small Magellanic Cloud (SMC, ZFe; SMC/ZFe; ⊙ ≈ 0.2). Our grids span a wide range in orbital periods (∼3 to 5000 days) and initial primary masses (10 M⊙ to 36 − 53 M⊙, depending on metallicity). We find that metallicity strongly influences the course and outcome of mass-transfer evolution. We identify two novel types of post-MS mass transfer: (a) mass exchange on the long nuclear timescale (ΔTMT ≳ 105 yr, Ṁ ∼ 10−5 M⊙ yr−1) that continues until the end of the CHeB phase, and (b) rapid mass transfer leading to detached binaries with mass losers that are only partially stripped of their envelopes. At LMC and SMC compositions, the majority of binary models with donor masses ≥17 M⊙ follow one of these two types of evolution. In neither (a) nor (b) does the donor become a fully stripped helium star by the end of CHeB. Boundaries between the different types of post-MS mass transfer evolution are associated with the degree of rapid post-MS expansion of massive stars and, for a given metallicity, are sensitive to the assumptions about internal mixing. At low metallicity, due to partial envelope stripping, we predict fewer hot fully stripped stars formed through binary interactions as well as higher compactness of the presupernova core structures of mass losers. Nuclear-timescale post-MS mass transfer suggests a strong preference for metal-poor host galaxies of ultra-luminous X-ray sources with black-hole (BH) accretors and massive donors, some of which might be the immediate progenitors of binary BH mergers. It also implies a population of interacting binaries with blue and yellow supergiant donors. Partially stripped stars could potentially explain the puzzling nitrogen-enriched slowly rotating (super)giants in the LMC.

Common patterns in pulse profiles of high-mass X-ray binaries

Context. X-ray pulsars are binary systems which consist of a neutron star in orbit with a mass donor (companion). In these systems the neutron accretes matter from the companion star, which creates accretion columns or hot spots on the neutron star surface and gives rise to pulsations in the X-ray light curve. The pulse profiles carry information about the accretion and magnetic field geometry. Here we present a study and classification of energy-resolved pulse profiles of a sample of X-ray pulsars, focusing on high-mass X-ray binaries. Aims. Our goal is to perform a classification of X-ray pulsars based on their observed pulse profiles and look for correlations between this classification and their principle physical observables. The analysis pipeline is available online. Methods. We analysed the pulse profiles of a sample of X-ray pulsars using data obtained with the X-ray Multi-Mirror Mission (XMM-Newton) and the Nuclear Spectroscopic Telescope Array (NuSTAR). We fitted the energy-resolved pulse profiles with a Fourier series of up to five harmonics. We then used the energy evolution of the different Fourier components to classify the pulse profiles into groups. We investigated relationships between the pulse profile properties and other observables of the systems (e.g. orbital period, magnetic field strength, and luminosity) to study the extreme physics of these systems. Results. The sources were divided into three groups using a classification based on the shape, the dominance of the fitted Fourier harmonics, and their respective evolution with energy. We do not find a conclusive correlation between the pulse profile shapes or groups and other parameters of the systems. However, a weak trend was found when comparing our classification to the sources’ locations in the spin period-orbital period diagram. Further studies are required to confirm this trend. Conclusions. Despite the large variety of pulse profiles of the X-ray pulsars, we found that with our approach clear categories emerge which we use to classify their behaviour as a function of energy. As we do not find a clear relationship between our classification scheme and other parameters, like the luminosity, the magnetic field strength, or the orbital and spin periods, we conclude that X-ray pulse profiles are influenced by other hidden variables.

Fluid Mechanics Inspired Sequential Blade‐Coating for High‐Performance Large‐Area Organic Solar Modules

AbstractDespite rapid advances in the field of organic solar cells (OSCs), high‐performance large‐scale OSC modules are limited. In this study, it is found that the non‐Newtonian fluid feature of conjugated polymer primarily causes the wedge‐shaped mass (donor and/or acceptor component)/phase distribution of blends in large‐scale blade coating, which results in the lower module efficiency. To address the critical issue in printing manufacturing, a reversible and sequential layer‐by‐layer (RS‐LBL) deposition method with sequential twice forward/reverse blade‐coating of polymer donor and forward blade‐coating of Y6 acceptor, is developed for precisely controlling fluid mechanics of PM6:Y6 active layer. Through using the RS‐LBL strategy, uniform morphology and favorable phase separation and crystallization are obtained in the 10 × 10 cm2 active layer. As a result, the RS‐LBL‐based OSCs show excellent operational stability, and an outstanding PCE of 13.47% is achieved with significantly suppressed charge recombination losses in the 36 cm2 large‐area OSC module, which represents the highest efficiency of binary solar modules with the area over 30 cm2. This study provides a feasible route for the next generation of high‐performance large‐area OSCs and OSC modules.

SXP 15.6 – an accreting pulsar close to spin equilibrium?

ABSTRACT SXP 15.6 is a recently established Be star X-ray binary system in the Small Magellanic Cloud (SMC). Like many such systems, the variable X-ray emission is driven by the underlying behaviour of the mass donor Be star. It is shown here that the neutron star in this system is exceptionally close to spin equilibrium averaged over several years, with the angular momentum gain from mass transfer being almost exactly balanced by radiative losses. This makes SXP 15.6 exceptional compared to all other known members of its class in the SMC, all of whom exhibit much higher spin period changes. In this paper, we report on X-ray observations of the brightest known outburst from this system. These observations are supported by contemporaneous optical and radio observations, as well as several years of historical data.

Mechanical Circulatory Support During Lung Transplantation: Choices, Outcomes and Impact of Duration

<h3>Purpose</h3> Venoarterial (VA) extracorporeal membrane oxygenation (ECMO) has recently replaced cardiopulmonary bypass (CPB) as the method of choice for mechanical circulatory support during lung transplantation (LTx). The aim of this study was to compare the outcomes of using ECMO versus CPB and examine the impact of its duration in a contemporary LTx cohort. <h3>Methods</h3> Between January 2017, and January 2020, 379 LTx were performed at our center. CPB was utilized in 111 and VA ECMO in 33 cases (unmatched cohort). After exclusion of patients who underwent concomitant cardiac procedures or retransplantation (all were in CPB group), the 33 VA ECMO patients were matched to CPB patients with a 1:2 ratio based on primary diagnosis, LTx type (bilateral or single), age, lung allocation score, body mass index, donor type (brain death or cardiac death), and duration of mechanical circulatory support. <h3>Results</h3> In the unmatched cohort, CPB group had a significantly higher incidence of re-exploration for bleeding and hospital mortality compared to ECMO group (15.3% vs 3.0%, <b>p = .047</b>; 10.8% vs 0%, <b>p = .038</b>, respectively). There were no statistically significant differences between CPB and ECMO groups in ICU stay, hospital stay, incidence of primary graft dysfunction (PGD) at 72 hours, postoperative tracheostomy, post-transplant ECMO use, re-admission, or 1-year survival. In the matched cohort, the differences between CPB and ECMO groups in both incidence of re-exploration for bleeding or hospital mortality were found to be statistically insignificant (13.6% vs 3.0%, <i>p</i> = .092; 7.6% vs 0%, <i>p</i> = .125, respectively). The differences between both groups in the other outcome endpoints remained insignificant. In the CPB group, patients with higher grades of PGD at 72 hours had significantly longer duration of CPB (PGD 0, 1, 2, 3 median 217, 209, 250, 289 minutes, <b>p = .014</b>, respectively). In the ECMO group, there were no differences in duration of ECMO between patients with different PGD grades. <h3>Conclusion</h3> Despite having a significantly higher incidence of re-exploration for bleeding and hospital mortality in CPB group in the unmatched cohort, there were no statistically significant differences between the two groups in the studied outcomes in the matched cohort, although there were strong trends. Notably, longer CPB time was associated with higher PGD grades whereas time on ECMO was not associated with PGD grades.

Spontaneous Donor Hypothermia is Independently Associated with Increased Risk of Primary Graft Dysfunction After Heart Transplant

<h3>Purpose</h3> Multiple donor and recipient characteristics contribute to the pathogenesis of primary graft dysfunction (PGD) after heart transplantation (HT). The purpose of this study was to determine the association between spontaneous donor hypothermia and PGD. <h3>Methods</h3> Consecutive adult HT recipients (n=1106) from 3/2012 to 12/2019 at two high-volume centers were included. Severe PGD was defined using the ISHLT consensus statement. Donor physiologic parameters were collected from the United Network for Organ Sharing Donor Management Goals registry. Univariable and multivariable logistic modeling were performed. <h3>Results</h3> Donors were predominantly male (66.6%), with a mean donor age of 34.9±13.0 years. Severe PGD occurred in 66 (6.0%) patients. Patients with severe PGD were more likely to receive organs from older donors (38.0±13.0 vs. 34.7±12.7 years, p=0.04) and lower donor to recipient heart mass ratio (1.00±0.15 vs. 1.05±0.20, p=0.048). Single variable modeling showed predicted heart mass ratio, donor age, and spontaneous donor hypothermia defined as less than 36 degrees Celsius at time of procurement to be significant predictors of severe PGD. Multivariable modeling showed that spontaneous donor hypothermia (OR 2.21, 95% CI: [1.21-4.03], p=0.01) was significantly associated with severe PGD after adjusting for donor age and predicted heart mass ratio. There was no increased incidence of severe PGD with spontaneous donor hypothermia either at time of referral (OR: 1.35, 95% CI: [0.78-2.35], p=0.28) or 12 to 18 hours later (OR: 1.16, 95% CI: [0.51-2.66], p=0.71). Spontaneous donor hyperthermia defined as greater than 37.5 degrees Celsius at time of procurement was not associated with severe PGD (OR: 1.69, 95% CI: [0.64-4.45], p=0.29). <h3>Conclusion</h3> Spontaneous donor hypothermia at time of organ procurement is associated with an increased risk of severe PGD.

Mass Transfer as an Explanation for the Lifetime Travel Time Discrepancy in IT Librae

Abstract The eclipsing binary IT Librae is an unusual system of two B-type stars that is situated about 1 kpc above the Galactic plane. The binary was probably ejected from its birthplace in the disk, but the implied time of flight to its current location exceeds the evolutionary lifetime of the primary star. Here we present a study of new high-dispersion spectroscopy and an exquisite light curve from the Kepler K2 mission in order to determine the system properties and resolve the timescale discrepancy. We derive a revised spectroscopic orbit from radial-velocity measurements and determine the component effective temperatures through comparison of reconstructed and model spectra (T 1 = 23.8 ± 1.8 kK, T 2 = 13.7 ± 2.5 kK). We use the Eclipsing Light Curve code to model the K2 light curve, and from the inclination of the fit we derive the component masses (M 1 = 9.6 ± 0.6 M ⊙, M 2 = 4.2 ± 0.2 M ⊙) and mean radii (R 1 = 6.06 ± 0.16 R ⊙, R 2 = 5.38 ± 0.14 R ⊙). The secondary star is overluminous for its mass and appears to fill its Roche lobe. This indicates that IT Librae is a post-mass-transfer system in which the current secondary was the mass donor star. The current primary star was rejuvenated by mass accretion, and its evolutionary age corresponds to the time since the mass transfer stage. Consequently, the true age of the binary is larger than the ejection time of flight, thus resolving the timescale discrepancy.