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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Evolution of close binary stars - Observational aspects

Detached close binary systems define the main sequence band satisfactorily, but very little is known about the masses of giants and supergiants. High-dispersion IUE observations promise an improvement, since blue companions are now frequently found to late-type supergiants. The interesting cases of Mu Sagittarii and in particular of Epsilon Aurigae are discussed in more detail. The barium star abundance anomaly appears now to be due to mass transfer in interacting systems. The symbiotic stars are another type of binary systems containing late-type giants; several possible models for the hotter star and for the type of interaction are discussed. The W Serpentis stars appear to be Algols in the rapid phase of mass transfer, but a possible link relating them to the symbiotics is also indicated. Evidence of hot circumstellar plasmas has now been found in several ordinary Algols; there may exist a smooth transition between very quiescent Algols and the W Serpentis stars. Bet2 Lyrae is discussed in the light of new spectrophotometric results.

Plavec, M. J.↗
DOE OSTI2024

Fate of supernova progenitors in massive binary systems

ABSTRACT How massive stars end their lives depends on the core mass, core angular momentum, and hydrogen envelopes at death. However, these key physical facets of stellar evolution can be severely affected by binary interactions. In turn, the effectiveness of binary interactions itself varies greatly depending on the initial conditions of the binaries, making the situation much more complex. We investigate systematically how binary interactions influence core–collapse progenitors and their fates. Binary evolution simulations are performed to survey the parameter space of supernova progenitors in solar metallicity binary systems and to delineate major evolutionary paths. We first study fixed binary mass ratios ($q=M_2/M_1$ = 0.5, 0.7, and 0.9) to elucidate the impacts of initial mass and initial separation on the outcomes, treating separately Type Ibc supernova, Type II supernova, accretion-induced collapse (AIC), rapidly rotating supernova (Ibc-R), black hole formation, and long gamma ray burst (long GRB). We then conduct 12 binary population synthesis model calculations, varying the initial condition distributions and binary evolution parameters, to estimate various supernova fractions. We obtain a Milky Way supernova rate $R_{\rm SN} = (1.78$–$2.47) \times 10^{-2} \, {\rm yr}^{-1}$ which is consistent with observations. We find the rates of AIC, Ibc-R, and long GRB to be $\sim 1/100$ the rate of regular supernovae. Our estimated long GRB rates are higher than the observed long GRB rate and close to the low luminosity GRB rate, although care must be taken considering our models are computed with solar metallicity. Furthering binary modelling and improving the inputs one by one will enable more detailed studies of these and other transients associated with massive stars.

Astronomy & Astrophysics↗
NASA NTRS1973

The galactic space frequency of close binary systems

An investigation of the galactic space frequency of close binary systems and other stars with high angular momentum is made on the basis of several criteria for the binary nature of a star. Within an accessible range of 3 kpc around the sun, which includes parts of three spiral arms, there occurs no significant variation (to within a factor of about 2) in the space frequencies of B-type radial-velocity variables, M-type supergiants with blue companions, and Be stars. Implications of this result for the problems of the origin of close binary systems, the distribution of angular momentum in the Galaxy, and the relative numbers of blue and red supergiants are discussed.

Stothers, R.↗
DOE OSTI2021

Deep Learning with Quantized Neural Networks for Gravitational-wave Forecasting of Eccentric Compact Binary Coalescence

We present the first application of deep learning forecasting for binary neutron stars, neutron star–black hole systems, and binary black hole mergers that span an eccentricity range e ≤ 0.9. In this work, we train neural networks that describe these astrophysical populations, and then test their performance by injecting simulated eccentric signals in advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) noise available at the Gravitational Wave Open Science Center to (1) quantify how fast neural networks identify these signals before the binary components merge; (2) quantify how accurately neural networks estimate the time to merger once gravitational waves are identified; and (3) estimate the time-dependent sky localization of these events from early detection to merger. Our findings show that deep learning can identify eccentric signals from a few seconds (for binary black holes) up to tens of seconds (for binary neutron stars) prior to merger. A quantized version of our neural networks achieves 4× reduction in model size, and up to 2.5× inference speedup. These novel algorithms may be used to facilitate time-sensitive multimessenger astrophysics observations of compact binaries in dense stellar environments.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Mass measurements show slowdown of rapid proton capture process at waiting-point nucleus 64Ge

Abstract X-ray bursts are among the brightest stellar objects frequently observed in the sky by space-based telescopes. A type-I X-ray burst is understood as a violent thermonuclear explosion on the surface of a neutron star, accreting matter from a companion star in a binary system. The bursts are powered by a nuclear reaction sequence known as the rapid proton capture process (rp process), which involves hundreds of exotic neutron-deficient nuclides. At so-called waiting-point nuclides, the process stalls until a slower β + decay enables a bypass. One of the handful of rp process waiting-point nuclides is 64 Ge, which plays a decisive role in matter flow and therefore the produced X-ray flux. Here we report precision measurements of the masses of 63 Ge, 64,65 As and 66,67 Se—the relevant nuclear masses around the waiting-point 64 Ge—and use them as inputs for X-ray burst model calculations. We obtain the X-ray burst light curve to constrain the neutron-star compactness, and suggest that the distance to the X-ray burster GS 1826–24 needs to be increased by about 6.5% to match astronomical observations. The nucleosynthesis results affect the thermal structure of accreting neutron stars, which will subsequently modify the calculations of associated observables.

Physics↗
NASA NTRS1981

Chromospheres and coronae in binary systems

Recent observations and spectral analysis of chromospheres and coronae are discussed for various types of binary systems containing cool stars. These include the W UMa-type systems, the RS CVn variables, and selected widely separated binary systems such as VV Cephei and the giant stars in the Hyades cluster. In many cases evidence for extreme examples of solar activity are found. Radiative losses in ultraviolet resonance lines can be at least one or two orders of magnitude larger than those found in the quiet sun. In lambda And, a RS CVn type system, there is evidence for inhomogeneous structure in the chromosphere and transition region. Rotation appears to be a determinant in the energy losses of these atmospheres although not the only one.

Dupree, A. K.↗
DOE OSTI2022

Enhancement of double-close-binary quadruples

ABSTRACT Double-close-binary quadruples (2 + 2 systems) are hierarchical systems of four stars where two short-period binary systems move around their common centre of mass on a wider orbit. Using Gaia Early Data Release 3, we search for comoving pairs where both components are eclipsing binaries. We present eight 2 + 2 quadruple systems with inner orbital periods of <0.4 d and with outer separations of ≳1000 au. All of these systems but one are newly discovered by this work, and we catalogue their orbital information measured from their light curves. We find that the occurrence rate of 2 + 2 quadruples is 7.3 ± 2.6 times higher than what is expected from random pairings of field stars. At most a factor of ∼2 enhancement may be explained by the age and metallicity dependence of the eclipsing binary fraction in the field stellar population. The remaining factor of ∼3 represents a genuine enhancement of the production of short-period binaries in wide-separation (>103 au) pairs, suggesting a close-binary formation channel that may be enhanced by the presence of wide companions.

Fezenko, Gavin B. (ORCID:0000000217169430)↗
NASA NTRS1991

Optical and ultraviolet spectroscopy of three F + B binary stars

Optical and ultraviolet spectroscopy is presented for three F + B objects that are members of the first group of strongly interacting, F II + B systems. The data obtained confirm that HD 59771, HD 242257, and CoD -30 5135 are all binary star systems consisting of a luminous F-type component and a B star. Strong, variable H-alpha emission is seen in all the stars. It is found that the UV spectrum of HD 59771 resembles the spectrum of HD 207739. CoD -30 5135 has the most dramatic mid-UV spectrum seen among the scores of observed cool + hot star systems.

Bopp, Bernard W.↗
NASA NTRS2001

The Ever Changing X-ray Sky: X-ray Transients Observed With BATSE

X-ray transients are typically sources in our own galaxy. They are called "transient" because they usually spend more time in quiescence than in outburst. These transients consist of a compact object and a "normal" star in a binary system. The compact objects in some of these systems are known to be neutron stars because they exhibit X-ray bursts or periodic pulsations, Other systems are believed to contain black holes based upon their outburst behavior and in some cases, optical measurements of their masses. The Burst and Transient Source Experiment (BATSE), one of 4 instruments on the Compton Gamma Ray Observatory, was an all-sky instrument sensitive to photons from about 20 keV to 2 MeV, designed primarily to detect gamma-ray bursts. Transient and persistent hard X-ray point sources were extracted from the data using the Earth occultation method to measure source intensities. In this method, the change in count rate in a BATSE detector was measured just before and just after a source location was occulted by the Earth. For long period pulsars (>1 second) Fourier transforms and epoch-folded searches were used to measure pulse frequency and pulsed flux. Using these methods, 3 black hole candidates and 6 X-ray pulsars were discovered with BATSE during its 9 years in orbit. BATSE provided unprecedented temporal coverage in the 20 keV - 2 MeV band, allowing detection of numerous new outbursts of X-ray transients. In this talk, I will describe the BATSE instrument, discuss methods we use to detect hard X-ray sources, and describe observations of X-ray transients.

Wilson-Hodge, Colleen A.↗
NASA NTRS1989

Gravitational radiation from primordial solitons and soliton-star binaries

The possibility that both the formation of nontopological solitons in a primordial second-order phase transition and binary systems of soliton stars could generate a stochastic gravitational-wave background is examined. The present contribution of gravitational radiation to the energy density of the universe from these processes is estimated for a number of different models. The detectability of such contributions from the timing measurements of the millisecond pulsar and spaceborne laser interferometry is briefly discussed and compared to other cosmological and local sources of background gravitational waves.

Gleiser, Marcelo↗
NASA NTRS1985

Activity-driven structure variations as a cause of period changes in RS Canis Venaticorum-like systems

Magnetic activity cycles of a convective star in a close binary system may lead to orbit period changes through tidal spin-orbit coupling. An increase in the mean magnetic field throughout the convection zone provides an additional pressure support and increases the star's moment of inertia. In order for the system to conserve angular momentum instantaneously, the convective star must reduce its rotation rate. When this happens, the system is no longer synchronous; in particular, the equilibrium tide now suffers a phase lag. A tidal torque must act, transferring angular momentum from the star's rotation to the orbit, lengthening the period. When the field decays, these events reverse and the period shortens. Observed period changes in RS CVn-like systems are of the order delta p/p = 10 to the -6th, implying variations in the mean field strength at the base of the convection zone of approximately 1000 G over time scales of 10-30 yr. It is predicted that the strength of magnetic activity indicators will track orbital period changes in a given system: the period will be largest during the active portion of the magnetic cycle and smallest during the quiescent part.

Van Buren, D.↗
NASA NTRS1992

Production of recycled pulsars in globular clusters via two-body tidal capture

The numbers of binary systems containing a neutron star that are formed in the cores of globular clusters via two-body tidal capture are investigated. The subsequent evolution of the resulting binary systems is examined. Monte Carlo techniques are employed to trace the histories of many neutron stars in the core of a model globular cluster. Various scenarios for mass stripping during capture and orbital circularization, and the effects of magnetic braking on the circularized orbits are explored. Calculations are carried out for two model clusters: 47 Tuc and Omega Cen. Distributions of orbital periods for newly formed binaries containing a neutron star in orbit with either a main-sequence star or a giant are presented. Each binary is followed until contact between the captured star and the neutron star is established. It is argued that these systems should be regarded as potential progenitors of 'recycled' pulsars.

Di Stefano, R↗
NASA NTRSDate not supplied

Photonic Source for Binary Source Simulations

More than half of the sun-like stars are in binary systems or have companions that hinder the search for planets around them using traditional technologies. There are only 69 FGK dwarfs within ten pc that can harbor true earth analogs. Direct imaging can detect and study the habitability of those targets measuring the chemical composition of the atmosphere, and astrometry can measure the planet's mass. We use Multi-Star Wavefront Control (MSWC), a technique that removes stellar leakage from both stellar components to enable direct imaging of binary systems. Currently, there is a technology demonstration experiment of MSWC for the Roman coronagraph instrument at the High Contrast Imaging Testbeds operated at JPL. One of the challenges for this experiment is to produce a binary source where both stars are incoherent with each other at close physical separation. On the other hand, to measure masses, it is possible to obtain relative astrometry measurements between the binary. The TOLIMAN concept proposes to use a diffractive pupil to calibrate the distortion and detector effects to reach 1uas astrometric accuracy. JPL currently has a laboratory to demonstrate this technology, which faces the same challenge as the MSWC project of producing two incoherent nearby sources. We developed Photonic Chips with multiple waveguides in Silicon Nitride for both projects to create incoherent single sources as close as 15um. In this paper, we present the concept application, the chips design, and the first results.

photonic chips↗
DOE OSTI2020

The Multiplanet System TOI-421: A Warm Neptune and a Super Puffy Mini-Neptune Transiting a G9 V Star in a Visual Binary

We report the discovery of a warm Neptune and a hot sub-Neptune transiting TOI-421 (BD-14 1137, TIC 94986319), a bright (V = 9.9) G9 dwarf star in a visual binary system observed by the Transiting Exoplanet Survey Satellite (TESS) space mission in Sectors 5 and 6. We performed ground-based follow-up observations—comprised of Las Cumbres Observatory Global Telescope transit photometry, NIRC2 adaptive optics imaging, and FIbre-fed Echellé Spectrograph, CORALIE, High Accuracy Radial velocity Planet Searcher, High Resolution Échelle Spectrometer, and Planet Finder Spectrograph high-precision Doppler measurements—and confirmed the planetary nature of the 16 day transiting candidate announced by the TESS team. We discovered an additional radial velocity signal with a period of five days induced by the presence of a second planet in the system, which we also found to transit its host star. We found that the inner mini-Neptune, TOI-421 b, has an orbital period of P{sub b} = 5.19672 ± 0.00049 days, a mass of M{sub b} = 7.17 ± 0.66 M{sub ⊕}, and a radius of R{sub b} = 2.68{sub −0.18}{sup +0.19} R{sub ⊕}, whereas the outer warm Neptune, TOI-421 c, has a period of P{sub c} = 16.06819 ± 0.00035 days, a mass of M{sub c} = 16.42{sub −1.04}{sup +1.06} M{sub ⊕}, a radius of R{sub c} = 5.09{sub −0.15}{sup +0.16} R{sub ⊕}, and a density of ρ{sub c} = 0.685{sub −0.072}{sup +0.080} g cm{sup −3}. With its characteristics, the outer planet (ρ{sub c} = 0.685{sub −0.072}{sup +0.080} g cm{sup −3}) is placed in the intriguing class of the super-puffy mini-Neptunes. TOI-421 b and TOI-421 c are found to be well-suited for atmospheric characterization. Our atmospheric simulations predict significant Lyα transit absorption, due to strong hydrogen escape in both planets, as well as the presence of detectable CH{sub 4} in the atmosphere of TOI-421 c if equilibrium chemistry is assumed.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2020

The Multiplanet System TOI-421: A Warm Neptune and a Super Puffy Mini-Neptune Transiting a G9 V Star in a Visual Binary

We report the discovery of a warm Neptune and a hot sub-Neptune transiting TOI-421 (BD-14 1137, TIC 94986319), a bright (V = 9.9) G9 dwarf star in a visual binary system observed by the Transiting Exoplanet Survey Satellite (TESS) space mission in Sectors 5 and 6. We performed ground-based follow-up observations—comprised of Las Cumbres Observatory Global Telescope transit photometry, NIRC2 adaptive optics imaging, and FIbre-fed Echellé Spectrograph, CORALIE, High Accuracy Radial velocity Planet Searcher, High Resolution Échelle Spectrometer, and Planet Finder Spectrograph high-precision Doppler measurements—and confirmed the planetary nature of the 16 day transiting candidate announced by the TESS team. We discovered an additional radial velocity signal with a period of five days induced by the presence of a second planet in the system, which we also found to transit its host star. We found that the inner mini-Neptune, TOI-421 b, has an orbital period of P(b) = 5.19672 ± 0.00049 days, a mass of M(b) = 7.17 ± 0.66 Mꚛ, and a radius of R(b) = 2.68 (+0.19,-0.18) Rꚛ, whereas the outer warm Neptune, TOI-421 c, has a period of P(c) = 16.06819 ± 0.00035 days, a mass of M(c) = 16.42 (+1.06,-1.04) Mꚛ, a radius of R(c) = 5.09{+0.16,-0.15) Rꚛ, and a density of ρ(c) = 0.685 (+0.080,-0.072) g/cu. cm. With its characteristics, the outer planet (ρ(c) = .685 {+0.080,-0.072) g/cu cm) is placed in the intriguing class of the super-puffy mini-Neptunes. TOI-421 b and TOI-421 c are found to be well-suited for atmospheric characterization. Our atmospheric simulations predict significant Lyα transit absorption, due to strong hydrogen escape in both planets, as well as the presence of detectable CH4 in the atmosphere of TOI-421 c if equilibrium chemistry is assumed.

Ilaria Carleo↗
NASA NTRS2015

Parameter Estimation for Compact Binaries with Ground-Based Gravitational-Wave Observations Using the LALInference

The Advanced LIGO and Advanced Virgo gravitational wave (GW) detectors will begin operation in the coming years, with compact binary coalescence events a likely source for the first detections. The gravitational waveforms emitted directly encode information about the sources, including the masses and spins of the compact objects. Recovering the physical parameters of the sources from the GW observations is a key analysis task. This work describes the LALInference software library for Bayesian parameter estimation of compact binary signals, which builds on several previous methods to provide a well-tested toolkit which has already been used for several studies. We show that our implementation is able to correctly recover the parameters of compact binary signals from simulated data from the advanced GW detectors. We demonstrate this with a detailed comparison on three compact binary systems: a binary neutron star (BNS), a neutron star - black hole binary (NSBH) and a binary black hole (BBH), where we show a cross-comparison of results obtained using three independent sampling algorithms. These systems were analysed with non-spinning, aligned spin and generic spin configurations respectively, showing that consistent results can be obtained even with the full 15-dimensional parameter space of the generic spin configurations. We also demonstrate statistically that the Bayesian credible intervals we recover correspond to frequentist confidence intervals under correct prior assumptions by analysing a set of 100 signals drawn from the prior. We discuss the computational cost of these algorithms, and describe the general and problem-specific sampling techniques we have used to improve the efficiency of sampling the compact binary coalescence (CBC) parameter space.

gravitational wave↗
NASA NTRS1994

A general catalogue of close binary systems

A comprehensive catalog of close binary stars to be used for the study of the fundamental properties of stars and for the exploration and elucidation of evolutionary processes in those systems, is presented. Spectroscopic binaries, variable stars, suspected variable stars, and interacting binaries are included in the scope of the catalog.

Webbink, Ronald F.↗