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NASA NTRS1985

On the binary nature of cosmic gamma-ray burst sources

The binary model of gamma ray burst sources wherein the bursts are emitted by a collapsed object in a close-binary stellar system and a small fraction of the gamma radiation is reprocessed into optical radiation in the surface layers of a companion star is considered, and it is concluded that the model is viable. In particular, under the assumption that the optical flashes discovered by Schaefer (1981) and Schaefer et al. (1984) were produced by gamma-ray bursts of about the same intensity as those observed, it is found that nearby binary systems with secondaries whose masses are less than about 0.06 solar mass can fit all the observational constraints for the three optical/gamma-ray pair events.

Rappaport, S. A.↗

NASA NTRS1989

Time variability of the X-ray sources in M33

The results of a variability study of the X-ray sources detected by the Einstein Observatory in the galaxy M33 are reported. Two of the 15 known sources are variable above the 99.73 percent confidence level. The light curve of one of these sources, M33 X-7, exhibits a variability pattern of high and low states, suggesting an eclipsing binary X-ray source. Such a finding would be the first identification of a close accreting binary system with an X-ray source in an external galaxy other than the Magellanic Clouds. The data suggest a binary period of 1.7857 day and an eclipse duration of about 0.4 day. The nuclear source M33 X-8 varies only in the softest part of the spectrum. The observations suggest a rapid variability and show a rapid flare with a rise time shorter than three days together with longer timescale variability.

Peres, G.↗

NASA NTRS1997

Superluminal Jets and Other Properties of Black Holes Binaries

Discoveries in the past few years of radio jets in Galactic black hole candidates have provided a link between active galactic nuclei (AGNS) and the compact stars in binary systems. The availability of binary systems relatively close by is an opportunity to learn about the jet production mechanism on a timescale a million times shorter than that of an AGN. Evidence is clearly seen of correlated high energy X-ray and gamma ray emission to radio emission from jets, linking the accretion and jet production mechanisms. objects such as GRS 1915+105, GRO J1655-40 and Cyg X-3 show striking properties which distinguish them from other black hole candidates. Our theoretical understanding of these systems is still in the formative stages. I review some of the most recent multiwavelength data and point out questions raised by these observations.

Harmon, Alan↗

NASA NTRS2008

LISA Pathfinder

USA Pathfinder is a space mission dedicated to demonstrating technology for the Laser Interferometer Space Antenna (LISA). LISA is a joint ESA/NASA mission to detect low-frequency gravitational waves on the 0.0001 to 0.1 Hz frequency band. LISA is expected to observe 100's of merging massive black hole binaries out z-15, tens of thousands of close compact binary systems in the Milky Way, merging intermediate-mass black hole binaries, tens of stellar-mass black holes falling into supermassive black holes in galactic centers, and possibly other exotic sources. Several critical LISA technologies have not been demonstrated at the requisite level of performance. In spaceflight, and some fight hardware cannot be tested in a 1-g environment. Hence, the LISA Pathfinder mission is being implemented to demonstrate these critical LISA technologies in a relevant flight environment. LISA Pathfinder mimics one arm of the LISA constellation by shrinking the 5-million-kilometer armlength down to a few tens of centimeters. The experimental concept is to measure the relative separation between two test masses nominally following their own geodesics, and thereby determine the relative residual acceleration between them near 1 mHz, about a decade above the lowest frequency required by LISA. To implement such a concept, disturbances on the test masses must be kept very small by many design features, but chiefly by "drag-free" flight. A drag-free spacecraft follows a free-falling test mass which it encloses, but has no mechanical connection to. The spacecraft senses it's orientation and separation with respect to the proof mass, and its propulsion system is commanded to keep the spacecraft centered about the test mass. Thus, the spacecraft shields the test mass from most external influences, and minimizes the effect of force gradients arising from the spacecraft, and acting on the test mass. LISA Pathfinder will compare the geodesic of one test mass against that of the other. Only a metrology system based on interferometry can achieve the displacement sensitivity. Interferometers monitor the separation of both test masses with a sensitivity comparable to that required by LISA, and using the same technologies. LISA Pathfinder is scheduled to be launched in the first half of 1020 to a Lissajous orbit around the first Sun-Earth Lagrange point, L1. In addition to a complete European technology package (the LISA Technology Package, or LTP), LISA Pathfinder will also carry thrusters and software, known as ST-7, a part of NASA's New Millennium Program.

Stebbins, Robin↗

NASA NTRS2012

NASA's Gravitational - Wave Mission Concept Study

With the conclusion of the NASA/ESA partnership on the Laser Interferometer Space Antenna (LISA) Project, NASA initiated a study to explore mission concepts that will accomplish some or all of the LISA science objectives at lower cost. The Gravitational-Wave Mission Concept Study consisted of a public Request for Information (RFI), a Core Team of NASA engineers and scientists, a Community Science Team, a Science Task Force, and an open workshop. The RFI yielded were 12 mission concepts, 3 instrument concepts and 2 technologies. The responses ranged from concepts that eliminated the drag-free test mass of LISA to concepts that replace the test mass with an atom interferometer. The Core Team reviewed the noise budgets and sensitivity curves, the payload and spacecraft designs and requirements, orbits and trajectories and technical readiness and risk. The Science Task Force assessed the science performance by calculating the horizons. the detection rates and the accuracy of astrophysical parameter estimation for massive black hole mergers, stellar-mass compact objects inspiraling into central engines. and close compact binary systems. Three mission concepts have been studied by Team-X, JPL's concurrent design facility. to define a conceptual design evaluate kt,y performance parameters. assess risk and estimate cost and schedule. The Study results are summarized.

Stebbins, Robin↗

NASA NTRS2013

Technology Development Roadmap: A Technology Development Roadmap for a Future Gravitational Wave Mission

Humankind will detect the first gravitational wave (GW) signals from the Universe in the current decade using ground-based detectors. But the richest trove of astrophysical information lies at lower frequencies in the spectrum only accessible from space. Signals are expected from merging massive black holes throughout cosmic history, from compact stellar remnants orbiting central galactic engines from thousands of close contact binary systems in the Milky Way, and possibly from exotic sources, some not yet imagined. These signals carry essential information not available from electromagnetic observations, and which can be extracted with extraordinary accuracy. For 20 years, NASA, the European Space Agency (ESA), and an international research community have put considerable effort into developing concepts and technologies for a GW mission. Both the 2000 and 2010 decadal surveys endorsed the science and mission concept of the Laser Interferometer Space Antenna (LISA). A partnership of the two agencies defined and analyzed the concept for a decade. The agencies partnered on LISA Pathfinder (LPF), and ESA-led technology demonstration mission, now preparing for a 2015 launch. Extensive technology development has been carried out on the ground. Currently, the evolved Laser Interferometer Space Antenna (eLISA) concept, a LISA-like concept with only two measurement arms, is competing for ESA's L2 opportunity. NASA's Astrophysics Division seeks to be a junior partner if eLISA is selected. If eLISA is not selected, then a LISA-like mission will be a strong contender in the 2020 decadal survey. This Technology Development Roadmap (TDR) builds on the LISA concept development, the LPF technology development, and the U.S. and European ground-based technology development. The eLISA architecture and the architecture of the Mid-sized Space-based Gravitational-wave Observatory (SGO Mid)-a competitive design with three measurement arms from the recent design study for a NASA-led mission after 2020-both use the same technologies. Further, NASA participation in an ESA-led mission would likely augment the eLISA architecture with a third arm to become the SGO Mid architecture. For these reasons, this TDR for a future GW mission applies to both designs and both programmatic paths forward. It is adaptable to the different timelines and roles for an ESA-led or a NASA-led mission, and it is adaptable to available resources. Based on a mature understanding of the interaction between technology and risk, the authors of this TDR have chosen a set of objectives that are more expansive than is usual. The objectives for this roadmap are: (1) reduce technical and development risks and costs; (2) understand and, where possible, relieve system requirements and consequences; (3) increase technical insight into critical technologies; and (4) validate the design at the subsystem level. The emphasis on these objectives, particularly the latter two, is driven by outstanding programmatic decisions, namely whether a future GW mission is ESA-led or NASA-led, and availability of resources. The relative emphasis is best understood in the context of prioritization.

Laser Interferometry Space Antenna↗

NASA NTRS1986

The mass of the classical cepheid SU Cygni

Radial velocity differences between the classical Cepheid SU Cyg and a hot companion were measured from IUE high dispersion spectra. The blue star is itself a close binary. The triple system solution provides the mass ratio of the Cepheid to the masses of the pair of companions. The masses of the companions are inferred from the low dispersion IUE spectra. The mass derived for the Cepheid is 6.3 solar masses, with a range from 7.0 to 5.9 solar masses, which is very close to the evolutionary mass.

Evans, Nancy Remage↗

NASA NTRS1987

The mass of the classical Cepheid SU Cygni

Evans, Nancy Remage↗

NASA NTRS2003

Terrestrial Planet Formation Around Close Binary Stars

Most stars reside in multiple star systems; however, virtually all models of planetary growth have assumed an isolated single star. Numerical simulations of the collapse of molecular cloud cores to form binary stars suggest that disks will form within such systems. Observations indirectly suggest disk material around one or both components within young binary star systems. If planets form at the right places within such circumstellar disks, they can remain in stable orbits within the binary star systems for eons. We are simulating the late stages of growth of terrestrial planets around close binary stars, using a new, ultrafast, symplectic integrator that we have developed for this purpose. The sum of the masses of the two stars is one solar mass, and the initial disk of planetary embryos is the same as that used for simulating the late stages of terrestrial planet growth within our Solar System and in the Alpha Centauri wide binary star system. Giant planets &are included in the simulations, as they are in most simulations of the late stages of terrestrial planet accumulation in our Solar System. When the stars travel on a circular orbit with semimajor axis of up to 0.1 AU about their mutual center of mass, the planetary embryos grow into a system of terrestrial planets that is statistically identical to those formed about single stars, but a larger semimajor axis and/or a significantly eccentric binary orbit can lead to significantly more dynamically hot terrestrial planet systems.

Lissauer, Jack J.↗

NASA NTRS2022

Ultraviolet Spectropolarimetry Conservative and Nonconservative Mass Transfer in OB Interacting Binaries

The current consensus is that at least half of the OB stars are formed in binary or multiple star systems. The evolution of OB stars is greatly influenced by whether the stars begin as close binaries, and the evolution of the binary systems depend on whether the mass transfer is conservative or nonconservative. FUV/NUV spectropolarimetry is poised to answer the latter question. This paper discusses how the Polstar spectropolarimetry mission can characterize the degree of nonconservative mass transfer that occurs at various stages of binary evolution, from the initial mass reversal to the late Algol phase, and quantify its amount. The proposed instrument combines spectroscopic and polarimetric capabilities, where the spectroscopy can resolve Doppler shifts in UV resonance lines with 10 km/s precision, and polarimetry can resolve linear polarization with 10 −3 precision or better. The spectroscopy will identify absorption by mass streams and other plasmas seen in projection against the stellar disk as a function of orbital phase, as well as scattering from extended splash structures, including jets. The polarimetry tracks the light coming from material not seen against the stellar disk, allowing the geometry of the scattering to be tracked, resolving ambiguities left by the spectroscopy and light-curve information. For example, nonconservative mass streams ejected in the polar direction will produce polarization of the opposite sign from conservative transfer accreting in the orbital plane. Time domain coverage over a range of phases of the binary orbit are well supported by the Polstar observing strategy. Special attention will be given to the epochs of enhanced systemic mass loss that have been identified from IUE observations (pre-mass reversal and tangential gas stream impact). We show how the history of systemic mass and angular momentum loss/gain episodes can be inferred via ensemble evolution through the r–q diagram. Combining the above elements will significantly improve our understanding of the mass transfer process and the amount of mass that can escape from the system, an important channel for changing the final mass and ultimate supernova of a large number of massive stars found in binaries at close enough separation to undergo interaction.

Geraldine J. Peters↗

NASA NTRS1981

Accretion disk coronae

Recent observations of partial X-ray eclipses from 4U1822-37 have shown that the central X-ray source in this system is diffused by a large Compton-thick accretion disk corona (ADC). Another binary, 4U2129-47, also displays a partial eclipse and contains an ADC. The possible origin of an ADC is discussed and a simple hydrostatic evaporated ADC model is developed which, when applied to 4U1822-37, 4U2129+47 and Cyg X-3, can explain their temporal and spectral properties. The quasi-sinusoidal modulation of all three sources can be reconciled with the partial occultation of the ADC by a bulge at the edge of the accretion disk which is caused by the inflowing material. The height of this bulge is an order of magnitude larger than the hydrostatic disk height and is the result of turbulence in the outer region of the disk. The spectral properties of all three sources can be understood in terms of Compton scattering of the original source spectrum by the ADC. Spectral variations with epoch in Cyg X-3 are probably caused by changes in the optical depth of the corona. A consequence of our model is that any accreting neutron star X-ray source in a semi-detached binary system which is close to its Eddington limit most likely contains an optically thick ADC.

White, N. E.↗

NASA NTRS1984

On the origin of the Moon by rotational fission

Consistent with the current understanding of the Moon's bulk composition, internal structure, seismic and tectonic characteristics, evidence is discussed which suggests that the Moon originated by fission. The concepts discussed are: (1) all stars are members of close or contact binary systems; (2) advances in dynamical studies of the fission hypothesis show that stellar bodies also undergo fission; (3) the newly formed proto moon would have lost a large fraction of its original mass via mass transfer; and (4) due to the foregoing concepts the result would be a moon of terrestrial mantle material which was depleted in both metallic iron and volatiles.

Binder, A. B.↗

NASA NTRS1982

IUE spectroscopic investigation of interacting binary systems

The IUE observations of binaries consisting of at least one early type star, to the Algol systems, and to W Serpentis systems are discussed. The OB close binaries almost invaribly show a stellar wind. The difference between an unevolved early type system and a slightly evolved system is difficult to discern observationally and probably not meaningful in terms of Roche lobes. the zeta Aur stars show complex gas motions and shocks. Many of the Algol systems show peculiarities in their ultraviolet continua and the resonance lines, particularly Si IV, are of abnormal and variable strength. Emission lines were detected in several systems during the total eclipse. The W Ser stars are characterized by numerous strong emission lines in their ultraviolet spectra. It appears that these systems may be related to beta Lyrae as they seem to be in a phase of rapid mass transfer and their spectra show similarities to that of beta Lyrae.

Mccluskey, G. E., Jr.↗

NASA NTRS1994

Astronomical observations of phenomena in disks

Astronomical constraints on disks around young stellar objects are reviewed in this abstract. Since disks around the youngest stars cannot generally be resolved spatially, most results are based on analyses of the infrared and radio emission from circumstellar dust and gas. At least half of all young stars seem to have substantial circumstellar disks at an age of approximately 10(exp 6) yr. The young objects without disks tend to be binary stellar systems, though not exclusively, and some close binaries may have outer disks that are not tidally disrupted. Probably most, if not all, stars formed originally with circumstellar disks, but evolutionary timescales may differ dramatically. All the results, disk disappearance, disk mass around young stars, and long-wavelength dust opacities, are subject to the additional uncertainty of the effects of infalling dusty envelopes, which produce the disks in the first place.

Hartmann, L.↗

NASA NTRS1993

Detection of a white dwarf companion to the Hyades stars HD 27483

We observed with IUE a white dwarf (WD) companion to the Hyades F6 V binary stars HD 27483. This system is known to be a close binary of two nearly equal stars with an orbital period of 3.05 days. Our IUE observations revealed the presence of a third star, a white dwarf with an effective temperature of 23,000 +/- 1000 K and a mass of approximately 0.6 solar mass. Its presence in the Hyades cluster with a known age permits me to derive the mass of its progenitor, which must have been about 2.3 solar masses. The presence of the white dwarf in a binary system opens the possibility that some of the envelope material, which was expelled by the WD progenitor, may have been collected by the F6 stars. We may thus be able to study abundance anomalies of the WD progenitor with known mass on the surface of the F6 companions.

Boehm-Vitense, Erika↗

NASA NTRS1986

High energy neutrino absorption and its effects on stars in close X-ray binaries

The physics and astrophysics of high energy neutrino production and interactions in close X-ray binary systems are studied. These studies were stimulated by recent observations of ultrahigh energy gamma-rays and possibly other ultrahigh energy particles coming from the directions of Cygnus X-3 and other binary systems and possessing the periodicity characteristics of these systems. Systems in which a compact object, such as a neutron star, is a strong source of high energy particles which, in turn, produce photons, neutronos and other secondary particles by interactions in the atmosphere of the companion star were considered. The highest energy neutrinos are absorbed deep in the companion and the associated energy deposition may be large enough to effect its structure or lead to its ultimate disruption. This neutrino heating was evaluated, starting with a detailed numerical calculation of the hadronic cascade induced in the atmosphere of the companion star. For some theoretical models, the resulting energy deposition from neutrino absorption may be so great as to disrupt the companion star over an astronomically small timescale of the order of 10,000 years. Even if the energy deposition is smaller, it may still be high enough to alter the system substantially, perhaps leading to quenching of high energy signals from the source. Given the cosmic ray luminosities required to produce the observed gamma rays from cygnus X-3 and LMX X-4, such a situation may occur in these sources.

Gaisser, T. K.↗

NASA NTRS1990

Gravitational radiation from the Galaxy

The spectral flux of gravitational radiation incident on earth from the Galactic W UMa binaries, unevolved binaries, cataclysmic binaries, neutron star binaries, black hole-neutron star binaries, and close white dwarf binary (CWDB) systems is calculated. The peak values for the strain amplitude hv produced by the binaries are: log hv = -17.0/sq rt Hz at log v = -4.40 Hz for W UMa's; log hv = -16.5/sq rt Hz at log v = -5.50 Hz for unevolved binaries; log hv = -18.2/sq rt Hz at log v = -5.15 Hz for neutron star binaries; log hv = -17.0/sq rt Hz at log v = -4.7 Hz for black hole-neutron star binaries; log hv = -18.0 /sq rt Hz at log v = -4.10 Hz for cataclysmic binaries, and log hv = -27.0/sq rt Hz at log v = -4.0 Hz for CWDBs. The gravitational flux at ultralow frequencies is emitted mainly by unevolved binaries. The integrated flux incident on earth is about 2.4 x 10 to the -9th ergs/sq cm/s.

Hils, D.↗

NASA NTRS1992

IRAS observations of novae. III - The related objects

Results are presented on an analysis of IRAS observations of a selected sample of 116 objects that show properties similar to those of classical novae detected and modeled by Harrison and Gehrz (1988, 1991). These objects include dwarf novae, novalike variables, symbiotic stars, and planetary nebulae with close binary central-star systems. A high detection rate of 80 percent was found for this sample, as compared with about 50 percent detection rate found in the earlier examined sample. A reexamination of data showed that, at low galactic latitudes, source confusion can account for many of the detections of novae. The seemingly high detection rates of other objects and the many high-latitude novae are difficult to explain.

Harrison, Tom↗