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Sample records for hole-neutron star binaries

  1. The Signature of Black Hole-Neutron Star Binaries

    NASA Astrophysics Data System (ADS)

    Liebling, Steven; Anderson, Matthew; Hirschmann, Eric; Lehner, Luis; Motl, Patrick; Neilsen, David; Palenzuela, Carlos

    2011-04-01

    Black hole-neutron star (BHNS) binaries are key gravitational wave sources, merging in the frequency band to which Earth-based GW detectors are most sensitive. Furthermore, as possible candidates for short-hard gamma ray bursts, combined observations in both gravitational and electromagnetic bands of BHNS mergers is thus an exciting possibility. This talk will discuss results from simulations that account for gravitational and magnetic effects as well as connections with processes capable of explaining key features of gamma ray bursts.

  2. Black Hole - Neutron Star Binary Simulations at Georgia Tech

    NASA Astrophysics Data System (ADS)

    Haas, Roland

    2009-05-01

    Mixed compact object binaries consisting of a black hole and a neutron star are expected to be not only one of the primary sources of gravitational radiation to be observed by interferometric detectors but also the central engine of short gamma-ray bursts. We report on the status of our effort at Georgia Tech to model these mixed binary systems using the moving puncture method. The results are obtained with an enhanced version our vacuum MayaKranc code coupled to the hydrodynamics Whisky code. We present preliminary results of gravitational waveforms and the disruption of the neutron star for simple polytropic equations of state.

  3. ELECTROMAGNETIC EXTRACTION OF ENERGY FROM BLACK-HOLE-NEUTRON-STAR BINARIES

    SciTech Connect

    McWilliams, Sean T.; Levin, Janna

    2011-12-01

    The coalescence of black-hole-neutron-star binaries is expected to be a principal source of gravitational waves for the next generation of detectors, Advanced LIGO and Advanced Virgo. For black hole masses not much larger than the neutron star mass, the tidal disruption of the neutron star by the black hole provides one avenue for generating an electromagnetic counterpart. However, in this work, we demonstrate that, for all black-hole-neutron-star binaries observable by Advanced LIGO/Virgo, the interaction of the black hole with the magnetic field of the neutron star will generate copious luminosity, comparable to supernovae and active galactic nuclei. This novel effect may have already been observed as a new class of very short gamma-ray bursts by the Swift Gamma-Ray Burst Telescope. These events may be observable to cosmological distances, so that any black-hole-neutron-star coalescence detectable with gravitational waves by Advanced LIGO/Virgo could also be detectable electromagnetically.

  4. Initial data for high-compactness black hole-neutron star binaries

    NASA Astrophysics Data System (ADS)

    Henriksson, Katherine; Foucart, François; Kidder, Lawrence E.; Teukolsky, Saul A.

    2016-05-01

    For highly compact neutron stars, constructing numerical initial data for black hole-neutron star binary evolutions is very difficult. We describe improvements to an earlier method that enable it to handle these more challenging cases. These improvements were found by invoking a general relaxation principle that may be helpful in improving robustness in other initial data solvers. We examine the case of a 6:1 mass ratio system in inspiral close to merger, where the star is governed by a polytropic {{Γ }}=2, an SLy, or an LS220 equation of state (EOS). In particular, we are able to obtain a solution with a realistic LS220 EOS for a star with compactness 0.26 and mass 1.98 M ⊙, which is representative of the highest reliably determined neutron star masses. For the SLy EOS, we can obtain solutions with a comparable compactness of 0.25, while for a family of polytropic equations of state, we obtain solutions with compactness up to 0.21, the largest compactness that is stable in this family. These compactness values are significantly higher than any previously published results.

  5. Black hole - neutron star merger simulations: Precessing binaries with neutrino treatment

    NASA Astrophysics Data System (ADS)

    Desai, Dhruv; Foucart, Francois; Kasen, Daniel

    2016-06-01

    Black hole-neutron star (BH-NS) mergers are exciting events to model, as they are a source of gravitational waves, like those discovered for the first time by Advanced LIGO earlier this year. These mergers are also the source of gamma-ray bursts and radioactively powered transients. We present here an outline of our entire research process. We first display results of general relativistic-hydrodynamic simulations using the Spectral Einstein Code (SpEC). We ran a set of BH-NS merger simulations varying three of the initial parameters of the black hole: mass, spin magnitude, and spin inclination (relative to the orbital angular momentum of the binary system). The code factors in neutrino cooling and use a temperature dependent, nuclear theory based equation of state, as opposed to simpler equations of state previously used. Though systems which treat precession and neutrino cooling have been simulated individually, the systems we analyzed are the first to take both into account. Once a disk has formed and settled down, we take data from the GR simulations and input it into the particle evolution code, which reads in the positions/velocities and further evolves the system in a Newtonian potential. We then present the fallback rate of bound particles throughout this period of evolution, the approximate density evolution, and the spatial distribution of ejecta.

  6. Fully Relativistic Simulations of the Inspiral and Merger of Black Hole - Neutron Star Binaries

    NASA Astrophysics Data System (ADS)

    Motl, Patrick M.; Anderson, M.; Besselman, M.; Chawla, S.; Hirschmann, E. W.; Lehner, L.; Liebling, S. L.; Neilsen, D.; Tohline, J. E.

    2010-01-01

    We present fully relativistic simulations of the inspiral and merger of quasi-equilibrium binaries composed of a neutron star and a black hole. We vary the mass ratio of the binary, the spin angular momentum of the black hole and the initial separation in a series of simulations. We also explore the role of magnetic fields by including a dipole field in the neutron star and evolve the field in the MHD approximation. We use the adaptive mesh refinement package HAD to resolve the disparate length scales in the problem ranging from the radiation zone down to the internal dynamics of the initial neutron star and tidal remnant. We will briefly highlight our results for the gravitational radiation waveform as well as the fate of the neutron star's material including the fraction that forms a debris disk. This work was supported by the NSF through grants PHY-0803629 and PHY-0653375 to LSU. The computations presented here were performed on resources from the Teragrid and the Louisiana Optical Network Initiative (LONI).

  7. General-relativistic simulations of binary black hole-neutron stars: Precursor electromagnetic signals

    NASA Astrophysics Data System (ADS)

    Paschalidis, Vasileios; Etienne, Zachariah B.; Shapiro, Stuart L.

    2013-07-01

    We perform the first general relativistic force-free simulations of neutron star magnetospheres in orbit about spinning and nonspinning black holes. We find promising precursor electromagnetic emission: typical Poynting luminosities at, e.g., an orbital separation of r=6.6RNS are LEM˜6×1042(BNS,p/1013G)2(MNS/1.4M⊙)2erg/s. The Poynting flux peaks within a broad beam of ˜40° in the azimuthal direction and within ˜60° from the orbital plane, establishing a possible lighthouse effect. Our calculations, though preliminary, preview more detailed simulations of these systems that we plan to perform in the future.

  8. GR simulations of binary black hole-neutron stars: Precursor electromagnetic signals

    NASA Astrophysics Data System (ADS)

    Paschalidis, Vasileios; Etienne, Zachariah B.; Shapiro, Stuart L.

    2014-03-01

    We present a new computational method for smoothly matching general relativistic ideal magnetohydrodynamics (MHD) to its force-free limit. The method is based on a flux-conservative formalism for MHD and its force-free limit, and a vector potential formulation for the induction equation to maintain the zero divergence constraint for the magnetic field. The force-free formulation evolves the magnetic field and the Poynting vector. Our force-free code passes a robust suite of tests, performed both in 1D flat spacetime and in 3D curved (black hole) spacetimes. Our matching technique successfully reproduces the aligned rotator force-free solution. As an application, we performed the first general relativistic, force-free simulations of neutron star (NS) magnetospheres in orbit about spinning and non-spinning black holes with BH:NS mass ratio 3:1. We find promising precursor EM emission: typical Poynting luminosities at, e.g., an orbital separation of 6.6 times the NS radius, are L ~ 6 ×1042 erg/s for a 1 . 4M⊙ NS endowed with a dipolar magnetic field with polar strength 1013G. The Poynting flux peaks within a broad beam of 40 degrees in the azimuthal direction, establishing a possible lighthouse effect.

  9. Exploring the Magnetic field and Black Hole Spin in Black Hole--Neutron star mergers

    NASA Astrophysics Data System (ADS)

    Chawla, Sarvnipun; Anderson, Matthew; Lehner, Luis; Liebling, Steven; Megevand, Miguel; Motl, Patrick; Neilsen, David; Palenzuela, Carlos

    2010-02-01

    A sizable magnetic field in neutron star-black hole binaries can have a strong influence on the merger dynamics of the fluid by redistributing angular momentum through different mechanisms. The magnetic field can also be responsible for collimating jets. BH spin can increase the number of orbits before merger as compared to a binary with a non-spinning BH. The corresponding decrease in ISCO can alter the tidal disruption suffered by the NS. We present results of fully relativistic black hole--neutron star simulations proceeding from quasi-circular initial data generated with the Lorene libraries. We explore the effect of magnetic field and spin by evolving four sets of nearly identical initial data which differ in their magnetic field and spin values. We examine the gravitational wave signature through direct simulation. Finally, we compare the fluid structure and explore the magnetic field configuration in the post-merger remnant disk. )

  10. Pulsations in short gamma ray bursts from black hole-neutron star mergers

    NASA Astrophysics Data System (ADS)

    Stone, Nicholas; Loeb, Abraham; Berger, Edo

    2013-04-01

    The precise of short gamma ray bursts (SGRBs) remains an important open question in relativistic astrophysics. Increasingly, observational evidence suggests the merger of a binary compact object system as the source for most SGRBs, but it is currently unclear how to distinguish observationally between a binary neutron star progenitor and a black hole-neutron star progenitor. We suggest the quasiperiodic signal of jet precession as an observational signature of SGRBs originating in mixed binary systems, and quantify both the fraction of mixed binaries capable of producing SGRBs and the distributions of precession amplitudes and periods. The difficulty inherent in disrupting a neutron star outside the horizon of a stellar mass black hole biases the jet precession signal towards low amplitude and high frequency. Precession periods of ˜0.01-0.1s and disk-black hole spin misalignments ˜10° are generally expected, although sufficiently high viscosity may prevent the accumulation of multiple precession periods during the SGRB. The precessing jet will naturally cover a larger solid angle in the sky than would standard SGRB jets, enhancing observability for both prompt emission and optical afterglows.

  11. Parameter estimation of gravitational waves from precessing black hole-neutron star inspirals with higher harmonics

    NASA Astrophysics Data System (ADS)

    O'Shaughnessy, Richard; Farr, Benjamin; Ochsner, Evan; Cho, Hee-Suk; Raymond, V.; Kim, Chunglee; Lee, Chang-Hwan

    2014-05-01

    Precessing black hole-neutron star (BH-NS) binaries produce a rich gravitational wave signal, encoding the binary's nature and inspiral kinematics. Using the lalinference_mcmc Markov chain Monte Carlo parameter estimation code, we use two fiducial examples to illustrate how the geometry and kinematics are encoded into the modulated gravitational wave signal, using coordinates well adapted to precession. Extending previous work, we demonstrate that the performance of detailed parameter estimation studies can often be estimated by "effective" studies: comparisons of a prototype signal with its nearest neighbors, adopting a fixed sky location and idealized two-detector network. Using a concrete example, we show that higher harmonics provide nonzero but small local improvement when estimating the parameters of precessing BH-NS binaries. We also show that higher harmonics can improve parameter estimation accuracy for precessing binaries by breaking leading-order discrete symmetries and thus ruling out approximately degenerate source orientations. Our work illustrates quantities gravitational wave measurements can provide, such as the orientation of a precessing short gamma ray burst progenitor relative to the line of sight. More broadly, "effective" estimates may provide a simple way to estimate trends in the performance of parameter estimation for generic precessing BH-NS binaries in next-generation detectors. For example, our results suggest that the orbital chirp rate, precession rate, and precession geometry are roughly independent observables, defining natural variables to organize correlations in the high-dimensional BH-NS binary parameter space.

  12. New results in black hole-neutron star merger models

    NASA Astrophysics Data System (ADS)

    Duez, Matthew

    2010-10-01

    I report on the SXS group's recent progress in using numerical general relativity to model one of the most violent and fascinating events in nature: the devouring of a neutron star by a black hole. I will discuss our efforts to simulate more representative and generic binary configurations and also our efforts to incorporate more realistic neutron star microphysics. Our numerical simulations allow us to predict post-merger states and gravitational wave signals.

  13. Relativistic simulations of black hole-neutron star coalescence: the jet emerges I

    NASA Astrophysics Data System (ADS)

    Paschalidis, Vasileios; Ruiz, Milton; Shapiro, Stuart

    2015-04-01

    The merger of binary black hole-neutron stars (BHNS) can form accretion disks, which are thought to support relativistic jets, thus providing the engine for a short-hard gamma-ray burst (sGRB). Until recently there existed no self-consistent calculation in full GR that starts from the late BHNS inspiral and demonstrates that jets can be launched after NS tidal disruption. This step is crucial to establishing BHNS systems as viable central engines for sGRBs and solidifying their role as multimessenger systems. In this talk I will provide the motivation for and review the fully relativistic simulations we have performed which, for the first time, show that BHNS mergers naturally give rise to jets.

  14. Black hole-neutron star mergers with a hot equation of state and neutrino cooling

    NASA Astrophysics Data System (ADS)

    Foucart, Francois

    2014-03-01

    Black hole-neutron star (BHNS) and neutron star-neutron star mergers will be prime candidates for the joint detection of gravitational wave and electromagnetic (EM) signals once the Advanced LIGO/VIRGO/KAGRA detectors come online. For BHNS binaries, the result of the merger strongly depends on the parameters of the system. EM emissions from a post-merger disk (e.g. gamma-ray bursts) are only possible for low mass or high spin black holes. The amount of ejected neutron-rich material, which has important consequences for the emission of more isotropic EM signals and the production of r-process elements, can also vary by a few orders of magnitudes - with high mass, high spin black holes ejecting more than 0 . 1M⊙ of unbound material. I will describe recent simulations of BHNS mergers performed by the SXS collaboration, which explore the parameter space dependence of these mergers while using a hot nuclear equation of state (LS220) and approximate neutrino cooling of the post-merger accretion disk. I will discuss the qualitative differences between these mergers and earlier simulations performed with polytropic equations of state, as well as the effect of neutrino cooling on the post-merger evolution and the general properties of the neutrino radiation.

  15. Black-hole-neutron-star mergers at realistic mass ratios: Equation of state and spin orientation effects

    NASA Astrophysics Data System (ADS)

    Foucart, Francois; Deaton, M. Brett; Duez, Matthew D.; Kidder, Lawrence E.; MacDonald, Ilana; Ott, Christian D.; Pfeiffer, Harald P.; Scheel, Mark A.; Szilagyi, Bela; Teukolsky, Saul A.

    2013-04-01

    Black-hole-neutron-star mergers resulting in the disruption of the neutron star and the formation of an accretion disk and/or the ejection of unbound material are prime candidates for the joint detection of gravitational-wave and electromagnetic signals when the next generation of gravitational-wave detectors comes online. However, the disruption of the neutron star and the properties of the postmerger remnant are very sensitive to the parameters of the binary (mass ratio, black-hole spin, neutron star radius). In this paper, we study the impact of the radius of the neutron star and the alignment of the black-hole spin on black-hole-neutron-star mergers within the range of mass ratio currently deemed most likely for field binaries (MBH˜7MNS) and for black-hole spins large enough for the neutron star to disrupt (JBH/MBH2=0.9). We find that (i) In this regime, the merger is particularly sensitive to the radius of the neutron star, with remnant masses varying from 0.3MNS to 0.1MNS for changes of only 2 km in the NS radius; (ii) 0.01M⊙-0.05M⊙ of unbound material can be ejected with kinetic energy ≳1051ergs, a significant increase compared to low mass ratio, low spin binaries. This ejecta could power detectable postmerger optical and radio afterglows. (iii) Only a small fraction of the Advanced LIGO events in this parameter range have gravitational-wave signals which could offer constraints on the equation of state of the neutron star (at best ˜3% of the events for a single detector at design sensitivity). (iv) A misaligned black-hole spin works against disk formation, with less neutron-star material remaining outside of the black hole after merger, and a larger fraction of that material remaining in the tidal tail instead of the forming accretion disk. (v) Large kicks vkick≳300km/s can be given to the final black hole as a result of a precessing black-hole-neutron-star merger, when the disruption of the neutron star occurs just outside or within the innermost

  16. The r-process in black hole-neutron star mergers based on a fully general-relativistic simulation

    NASA Astrophysics Data System (ADS)

    Nishimura, N.; Wanajo, S.; Sekiguchi, Y.; Kiuchi, K.; Kyutoku, K.; Shibata, M.

    2016-01-01

    We investigate the black hole-neutron star binary merger in the contest of the r-process nucleosynthesis. Employing a hydrodynamical model simulated in the framework of full general relativity, we perform nuclear reaction network calculations. The extremely neutron-rich matter with the total mass 0.01 M⊙ is ejected, in which a strong r-process with fission cycling proceeds due to the high neutron number density. We discuss relevant astrophysical issues such as the origin of r-process elements as well as the r-process powered electromagnetic transients.

  17. Influence of neutrinos on r-process nucleosynthesis in black hole-neutron star mergers

    NASA Astrophysics Data System (ADS)

    Lippuner, Jonas; Roberts, Luke F.; Duez, Matthew D.; Faber, Joshua A.; Foucart, Francois; Lombardi, James C.; Ott, Christian D.; Ponce, Marcelo

    2016-03-01

    During a black hole-neutron star merger, baryonic material can be dynamically ejected. Because this ejecta is extremely neutron-rich, the r-process rapidly synthesizes heavy nuclides as the material expands and cools. This can contribute to galactic chemical evolution of the r-process elements and lead to a short-lived optical transient, called a kilonova, powered by the radioactive decay of the heavy nuclides. We use the nuclear reaction network SkyNet to model r-process nucleosynthesis under varying levels of neutrino irradiation by post-processing tracer particles in the ejecta of a full numerical relativity simulation of a black hole-neutron star merger. We find the ejected material robustly produces the second and third r-process peaks, whose abundances remain unchanged even for very high neutrino luminosities, due to the rapid velocities of the outflow. Nonetheless, we find that neutrinos can have an impact on the detailed abundance pattern by significantly enhancing the amount of material produced in the first peak around A ~ 78 . Electron neutrinos are captured by neutrons to produce protons while neutron capture is occurring. These protons rapidly form low-mass seed nuclei, a fraction of which eventually ends up in the first peak after neutron capture ceases. Partially supported by NASA and NSF under AST-1205732, AST-1313091, AST-1333520, PF3-140114, PF4-150122, and PHY-1151197.

  18. Binary stars.

    PubMed

    Paczynacuteski, B

    1984-07-20

    Most stars in the solar neighborhood are either double or multiple systems. They provide a unique opportunity to measure stellar masses and radii and to study many interesting and important phenomena. The best candidates for black holes are compact massive components of two x-ray binaries: Cygnus X-1 and LMC X-3. The binary radio pulsar PSR 1913 + 16 provides the best available evidence for gravitational radiation. Accretion disks and jets observed in close binaries offer a very good testing ground for models of active galactic nuclei and quasars. PMID:17749544

  19. Black hole, neutron star and white dwarf candidates from microlensing with OGLE-III★

    NASA Astrophysics Data System (ADS)

    Wyrzykowski, Ł.; Kostrzewa-Rutkowska, Z.; Skowron, J.; Rybicki, K. A.; Mróz, P.; Kozłowski, S.; Udalski, A.; Szymański, M. K.; Pietrzyński, G.; Soszyński, I.; Ulaczyk, K.; Pietrukowicz, P.; Poleski, R.; Pawlak, M.; Iłkiewicz, K.; Rattenbury, N. J.

    2016-05-01

    Most stellar remnants so far have been found in binary systems, where they interact with matter from their companions. Isolated neutron stars and black holes are difficult to find as they are dark, yet they are predicted to exist in our Galaxy in vast numbers. We explored the OGLE-III data base of 150 million objects observed in years 2001-2009 and found 59 microlensing events exhibiting a parallax effect due to the Earth's motion around the Sun. Combining parallax and brightness measurements from microlensing light curves with expected proper motions in the Milky Way, we identified 13 microlensing events which are consistent with having a white dwarf, neutron star or a black hole lens and we estimated their masses and distances. The most massive of our black hole candidates has 9.3 M⊙ and is at a distance of 2.4 kpc. The distribution of masses of our candidates indicates a continuum in mass distribution with no mass gap between neutron stars and black holes. We also present predictions on how such events will be observed by the astrometric Gaia mission.

  20. Spectroscopic Binary Stars

    NASA Astrophysics Data System (ADS)

    Batten, A.; Murdin, P.

    2000-11-01

    Historically, spectroscopic binary stars were binary systems whose nature was discovered by the changing DOPPLER EFFECT or shift of the spectral lines of one or both of the component stars. The observed Doppler shift is a combination of that produced by the constant RADIAL VELOCITY (i.e. line-of-sight velocity) of the center of mass of the whole system, and the variable shift resulting from the o...

  1. SPIN-PRECESSION: BREAKING THE BLACK HOLE-NEUTRON STAR DEGENERACY

    SciTech Connect

    Chatziioannou, Katerina; Cornish, Neil; Klein, Antoine; Yunes, Nicolás

    2015-01-01

    Mergers of compact stellar remnants are prime targets for the LIGO/Virgo gravitational wave detectors. The gravitational wave signals from these merger events can be used to study the mass and spin distribution of stellar remnants, and provide information about black hole horizons and the material properties of neutron stars. However, it has been suggested that degeneracies in the way that the star's mass and spin are imprinted in the waveforms may make it impossible to distinguish between black holes and neutron stars. Here we show that the precession of the orbital plane due to spin-orbit coupling breaks the mass-spin degeneracy, and allows us to distinguish between standard neutron stars and alternative possibilities, such as black holes or exotic neutron stars with large masses and spins.

  2. Parameter estimation of gravitational waves from nonprecessing black hole-neutron star inspirals with higher harmonics: Comparing Markov-chain Monte Carlo posteriors to an effective Fisher matrix

    NASA Astrophysics Data System (ADS)

    O'Shaughnessy, Richard; Farr, Ben; Ochsner, Evan; Cho, Hee-Suk; Kim, Chunglee; Lee, Chang-Hwan

    2014-03-01

    Most calculations of the gravitational wave signal from merging compact binaries limit attention to the leading-order quadrupole when constructing models for detection or parameter estimation. Some studies have claimed that if additional "higher harmonics" are included consistently in the gravitational wave signal and search model, binary parameters can be measured much more precisely. Using the lalinference Markov-chain Monte Carlo parameter estimation code, we construct posterior parameter constraints associated with two distinct nonprecessing black hole-neutron star (BH-NS) binaries, each with and without higher-order harmonics. All simulations place a plausible signal into a three-detector network with Gaussian noise. Our simulations suggest that higher harmonics provide little information, principally allowing us to measure a previously unconstrained angle associated with the source geometry well but otherwise improving knowledge of all other parameters by a few percent for our loud fiducial signal (ρ =20). Even at this optimistic signal amplitude, different noise realizations have a more significant impact on parameter accuracy than higher harmonics. We compare our results with the "effective Fisher matrix" introduced previously as a method to obtain robust analytic predictions for complicated signals with multiple significant harmonics. We find generally good agreement with these predictions, confirm that intrinsic parameter measurement accuracy is nearly independent of detector network geometry, and show that uncertainties in extrinsic and intrinsic parameters can, to a good approximation, be separated. For our fiducial example, the individual masses can be determined to lie between 7.11-11.48M⊙ and 1.77-1.276M⊙ at greater than 99% confidence level, accounting for unknown BH spin. Assuming comparable control over waveform systematics, measurements of BH-NS binaries can constrain the BH and perhaps NS mass distributions. Using analytic arguments to

  3. Modeling Binary Neutron Stars

    NASA Astrophysics Data System (ADS)

    Park, Conner; Read, Jocelyn; Flynn, Eric; Lockett-Ruiz, Veronica

    2016-03-01

    Gravitational waves, predicted by Einstein's Theory of Relativity, are a new frontier in astronomical observation we can use to observe phenomena in the universe. Laser Interferometer Gravitational wave Observatory (LIGO) is currently searching for gravitational wave signals, and requires accurate predictions in order to best extract astronomical signals from all other sources of fluctuations. The focus of my research is in increasing the accuracy of Post-Newtonian models of binary neutron star coalescence to match the computationally expensive Numerical models. Numerical simulations can take months to compute a couple of milliseconds of signal whereas the Post-Newtonian can generate similar signals in seconds. However the Post-Newtonian model is an approximation, e.g. the Taylor T4 Post-Newtonian model assumes that the two bodies in the binary neutron star system are point charges. To increase the effectiveness of the approximation, I added in tidal effects, resonance frequencies, and a windowing function. Using these observed effects from simulations significantly increases the Post-Newtonian model's similarity to the Numerical signal.

  4. Chemical Evolution of Binary Stars

    NASA Astrophysics Data System (ADS)

    Izzard, R. G.

    2013-02-01

    Energy generation by nuclear fusion is the fundamental process that prevents stars from collapsing under their own gravity. Fusion in the core of a star converts hydrogen to heavier elements from helium to uranium. The signature of this nucleosynthesis is often visible in a single star only for a very short time, for example while the star is a red giant or, in massive stars, when it explodes. Contrarily, in a binary system nuclear-processed matter can captured by a secondary star which remains chemically polluted long after its more massive companion star has evolved and died. By probing old, low-mass stars we gain vital insight into the complex nucleosynthesis that occurred when our Galaxy was much younger than it is today. Stellar evolution itself is also affected by the presence of a companion star. Thermonuclear novae and type Ia supernovae result from mass transfer in binary stars, but big questions still surround the nature of their progenitors. Stars may even merge and one of the challenges for the future of stellar astrophysics is to quantitatively understand what happens in such extreme systems. Binary stars offer unique insights into stellar, galactic and extragalactic astrophysics through their plethora of exciting phenomena. Understanding the chemical evolution of binary stars is thus of high priority in modern astrophysics.

  5. BINARIES AMONG DEBRIS DISK STARS

    SciTech Connect

    Rodriguez, David R.; Zuckerman, B.

    2012-02-01

    We have gathered a sample of 112 main-sequence stars with known debris disks. We collected published information and performed adaptive optics observations at Lick Observatory to determine if these debris disks are associated with binary or multiple stars. We discovered a previously unknown M-star companion to HD 1051 at a projected separation of 628 AU. We found that 25% {+-} 4% of our debris disk systems are binary or triple star systems, substantially less than the expected {approx}50%. The period distribution for these suggests a relative lack of systems with 1-100 AU separations. Only a few systems have blackbody disk radii comparable to the binary/triple separation. Together, these two characteristics suggest that binaries with intermediate separations of 1-100 AU readily clear out their disks. We find that the fractional disk luminosity, as a proxy for disk mass, is generally lower for multiple systems than for single stars at any given age. Hence, for a binary to possess a disk (or form planets) it must either be a very widely separated binary with disk particles orbiting a single star or it must be a small separation binary with a circumbinary disk.

  6. BDB: The Binary Star Database

    NASA Astrophysics Data System (ADS)

    Dluzhnevskaya, O.; Kaygorodov, P.; Kovaleva, D.; Malkov, O.

    2014-05-01

    Description of the Binary star DataBase (BDB, http://bdb.inasan.ru), the world's principal database of binary and multiple systems of all observational types, is presented in the paper. BDB contains data on physical and positional parameters of 100,000 components of 40,000 systems of multiplicity 2 to 20, belonging to various observational types: visual, spectroscopic, eclipsing, etc. Information on these types of binaries is obtained from heterogeneous sources of data - astronomical and. Organization of the information is based on the careful cross-identification of the objects. BDB can be queried by star identifier, coordinates, and other parameters.

  7. The Michigan Binary Star Program

    NASA Astrophysics Data System (ADS)

    Lindner, Rudi P.

    2007-07-01

    At the end of the nineteenth century, William J. Hussey and Robert G. Aitken, both at Lick Observatory, began a systematic search for unrecorded binary stars with the aid of the 12" and 36" refracting telescopes at Lick Observatory. Aitken's work (and book on binary stars) are well known, Hussey's contributions less so. In 1905 Hussey, a Michigan engineering graduate, returned to direct the Ann Arbor astronomy program, and immediately he began to design new instrumentation for the study of binary stars and to train potential observers. For a time, he spent six months a year at the La Plata Observatory, where he discovered a number of new pairs and decided upon a major southern hemisphere campaign. He spent a decade obtaining the lenses for a large refractor, through the vicissitudes of war and depression. Finally, he obtained a site in South Africa, a 26" refractor, and a small corps of observers, but he died in London en route to fulfill his dream. His right hand man, Richard Rossiter, established the observatory and spent the next thirty years discovering and measuring binary stars: his personal total is a record for the field. This talk is an account of the methods, results, and utility of the extraordinary binary star factory in the veldt.

  8. Binary Stars in SBS Survey

    NASA Astrophysics Data System (ADS)

    Erastova, L. K.

    2016-06-01

    Thirty spectroscopic binary stars were found in the Second Byurakan Survey (SBS). They show composite spectra - WD(DA)+dM or dC (for example Liebert et al. 1994). They may have red color, if the radiation of the red star dominates, and blue one, if the blue star is brighter and have peculiar spectrum in our survey plate. We obtained slit spectra for most of such objects. But we often see the spectrum of one component, because our slit spectra did not cover all optical range. We examine by eye the slit spectra of all SBS stellar objects (˜700) in SDSS DR7, DR8 or DR9 independent on our observations. We confirmed or discovered the duplicity of 30 stars. Usually they are spectroscopic binaries, where one component is WD (DA) and the second one is a red star with or without emission. There also are other components combinations. Sometimes there are emission lines, probably, indicating variable ones.

  9. Spectroscopic Binary Frequency among CNO Stars

    NASA Astrophysics Data System (ADS)

    Levato, H.; Malaroda, S.; Garcia, B.; Morell, N.

    1987-05-01

    ABSTRACT. Radial velocity variations are- analyzed through a sample of 35 OB stars with CH anomalies.Bolton and Rogers' proposal (1978) is con- firmed in the sense that the OBN stars appear preferably in short-period binary systems, in contrast to OBC stars. : STARS-BINARY - STARS-EARLY TYPE

  10. Gamma-ray bursts as the death throes of massive binary stars

    NASA Technical Reports Server (NTRS)

    Narayan, Ramesh; Paczynski, Bohdan; Piran, Tsvi

    1992-01-01

    We propose that gamma-ray bursts are created in the mergers of double neutron star binaries and black hole neutron star binaries at cosmological distances. Two different processes provide the electromagnetic energy for the bursts: neutrino-antineutrino annihilation into electron-position pairs during the merger, and magnetic flares generated by the Parker instability in a postmerger differentially rotating disk. In both cases, an optically thick fireball of size less than or approximately equal to 100 km is initially created, which expands ultrarelativistically to large radii before radiating. The scenario is only qualitative at this time, but it eliminates many previous objections to the cosmological merger model. The strongest bursts should be found close to, but not at the centers of, galaxies at redshifts of order 0.1, and should be accompanied by bursts of gravitational radiation from the spiraling-in binary which could be detected by LIGO.

  11. BLACK HOLE-NEUTRON STAR MERGERS WITH A HOT NUCLEAR EQUATION OF STATE: OUTFLOW AND NEUTRINO-COOLED DISK FOR A LOW-MASS, HIGH-SPIN CASE

    SciTech Connect

    Deaton, M. Brett; Duez, Matthew D.; Foucart, Francois; O'Connor, Evan; Ott, Christian D.; Scheel, Mark A.; Szilagyi, Bela; Kidder, Lawrence E.; Muhlberger, Curran D. E-mail: m.duez@wsu.edu

    2013-10-10

    Neutrino emission significantly affects the evolution of the accretion tori formed in black hole-neutron star mergers. It removes energy from the disk, alters its composition, and provides a potential power source for a gamma-ray burst. To study these effects, simulations in general relativity with a hot microphysical equation of state (EOS) and neutrino feedback are needed. We present the first such simulation, using a neutrino leakage scheme for cooling to capture the most essential effects and considering a moderate mass (1.4 M{sub ☉} neutron star, 5.6 M{sub ☉} black hole), high-spin (black hole J/M {sup 2} = 0.9) system with the K{sub 0} = 220 MeV Lattimer-Swesty EOS. We find that about 0.08 M{sub ☉} of nuclear matter is ejected from the system, while another 0.3 M{sub ☉} forms a hot, compact accretion disk. The primary effects of the escaping neutrinos are (1) to make the disk much denser and more compact, (2) to cause the average electron fraction Y{sub e} of the disk to rise to about 0.2 and then gradually decrease again, and (3) to gradually cool the disk. The disk is initially hot (T ∼ 6 MeV) and luminous in neutrinos (L{sub ν} ∼ 10{sup 54} erg s{sup –1}), but the neutrino luminosity decreases by an order of magnitude over 50 ms of post-merger evolution.

  12. Gravity darkening in binary stars

    NASA Astrophysics Data System (ADS)

    Espinosa Lara, F.; Rieutord, M.

    2012-11-01

    Context. Interpretation of light curves of many types of binary stars requires the inclusion of the (cor)relation between surface brightness and local effective gravity. Until recently, this correlation has always been modeled by a power law relating the flux or the effective temperature and the effective gravity, namely Teff ∝ geffβ . Aims: We look for a simple model that can describe the variations of the flux at the surface of stars belonging to a binary system. Methods: This model assumes that the energy flux is a divergence-free vector anti-parallel to the effective gravity. The effective gravity is computed from the Roche model. Results: After explaining in a simple manner the old result of Lucy (1967, Z. Astrophys., 65, 89), which says that β ~ 0.08 for solar type stars, we first argue that one-dimensional models should no longer be used to evaluate gravity darkening laws. We compute the correlation between log Teff and log geff using a new approach that is valid for synchronous, weakly magnetized, weakly irradiated binaries. We show that this correlation is approximately linear, validating the use of a power law relation between effective temperature and effective gravity as a first approximation. We further show that the exponent β of this power law is a slowly varying function, which we tabulate, of the mass ratio of the binary star and the Roche lobe filling factor of the stars of the system. The exponent β remains mostly in the interval [0.20,0.25] if extreme mass ratios are eliminated. Conclusions: For binary stars that are synchronous, weakly magnetized and weakly irradiated, the gravity darkening exponent is well constrained and may be removed from the free parameters of the models.

  13. Young and Waltzing Binary Stars

    NASA Astrophysics Data System (ADS)

    2001-10-01

    ADONIS Observes Low-mass Eclipsing System in Orion Summary A series of very detailed images of a binary system of two young stars have been combined into a movie . In merely 3 days, the stars swing around each other. As seen from the earth, they pass in front of each other twice during a full revolution, producing eclipses during which their combined brightness diminishes . A careful analysis of the orbital motions has now made it possible to deduce the masses of the two dancing stars . Both turn out to be about as heavy as our Sun. But while the Sun is about 4500 million years old, these two stars are still in their infancy. They are located some 1500 light-years away in the Orion star-forming region and they probably formed just 10 million years ago . This is the first time such an accurate determination of the stellar masses could be achieved for a young binary system of low-mass stars . The new result provides an important piece of information for our current understanding of how young stars evolve. The observations were obtained by a team of astronomers from Italy and ESO [1] using the ADaptive Optics Near Infrared System (ADONIS) on the 3.6-m telescope at the ESO La Silla Observatory. PR Photo 29a/01 : The RXJ 0529.4+0041 system before primary eclipse PR Photo 29b/01 : The RXJ 0529.4+0041 system at mid-primary eclipse PR Photo 29c/01 : The RXJ 0529.4+0041 system after primary eclipse PR Photo 29d/01 : The RXJ 0529.4+0041 system before secondary eclipse PR Photo 29e/01 : The RXJ 0529.4+0041 system at mid-secondary eclipse PR Photo 29f/01 : The RXJ 0529.4+0041 system after secondary eclipse PR Video Clip 06/01 : Video of the RXJ 0529.4+0041 system Binary stars and stellar masses Since some time, astronomers have noted that most stars seem to form in binary or multiple systems. This is quite fortunate, as the study of binary stars is the only way in which it is possible to measure directly one of the most fundamental quantities of a star, its mass. The mass of a

  14. Contact binary stars

    NASA Astrophysics Data System (ADS)

    Mochnacki, S. W.

    1981-04-01

    Densities, corrected primary colors, minimum periods, inferred masses, luminosities, and specific angular momenta are computed from data on 37 W Ursae Majoris systems. A-type systems, having lower densities and angular momenta than the W-type systems, are shown to be evolved, and a new class of contact binary is identified, the OO Aquilae systems, whose members have evolved into contact. Evolutionary grids based on the contact condition agree with observation, except in that the evolved A-type systems have lost more angular momentum than predicted by gravitational radiation alone. This is accounted for by stellar wind magnetic braking, which is shown to be effective on a shorter time scale and to be important in other kinds of binaries containing a cool, tidally coupled component.

  15. Neutron Star Mass Distribution in Binaries

    NASA Astrophysics Data System (ADS)

    Lee, Chang-Hwan; Kim, Young-Min

    2016-05-01

    Massive neutron stars with ∼ 2Mʘ have been observed in neutron star-white dwarf binaries. On the other hand, well-measured neutron star masses in double-neutron-star binaries are still consistent with the limit of 1.5Mʘ. These observations raised questions on the neutron star equations of state and the neutron star binary evolution processes. In this presentation, a hypothesis of super-Eddington accretion and its implications are discussed. We argue that a 2Mʘ neutron star is an outcome of the super-Eddington accretion during the evolution of neutron star-white dwarf binary progenitors. We also suggest the possibility of the existence of new type of neutron star binary which consists of a typical neutron star and a massive compact companion (high-mass neutron star or black hole) with M ≥ 2Mʘ.

  16. Young and Waltzing Binary Stars

    NASA Astrophysics Data System (ADS)

    2001-10-01

    ADONIS Observes Low-mass Eclipsing System in Orion Summary A series of very detailed images of a binary system of two young stars have been combined into a movie . In merely 3 days, the stars swing around each other. As seen from the earth, they pass in front of each other twice during a full revolution, producing eclipses during which their combined brightness diminishes . A careful analysis of the orbital motions has now made it possible to deduce the masses of the two dancing stars . Both turn out to be about as heavy as our Sun. But while the Sun is about 4500 million years old, these two stars are still in their infancy. They are located some 1500 light-years away in the Orion star-forming region and they probably formed just 10 million years ago . This is the first time such an accurate determination of the stellar masses could be achieved for a young binary system of low-mass stars . The new result provides an important piece of information for our current understanding of how young stars evolve. The observations were obtained by a team of astronomers from Italy and ESO [1] using the ADaptive Optics Near Infrared System (ADONIS) on the 3.6-m telescope at the ESO La Silla Observatory. PR Photo 29a/01 : The RXJ 0529.4+0041 system before primary eclipse PR Photo 29b/01 : The RXJ 0529.4+0041 system at mid-primary eclipse PR Photo 29c/01 : The RXJ 0529.4+0041 system after primary eclipse PR Photo 29d/01 : The RXJ 0529.4+0041 system before secondary eclipse PR Photo 29e/01 : The RXJ 0529.4+0041 system at mid-secondary eclipse PR Photo 29f/01 : The RXJ 0529.4+0041 system after secondary eclipse PR Video Clip 06/01 : Video of the RXJ 0529.4+0041 system Binary stars and stellar masses Since some time, astronomers have noted that most stars seem to form in binary or multiple systems. This is quite fortunate, as the study of binary stars is the only way in which it is possible to measure directly one of the most fundamental quantities of a star, its mass. The mass of a

  17. Rotating and binary relativistic stars with magnetic field

    NASA Astrophysics Data System (ADS)

    Markakis, Charalampos

    We develop a geometrical treatment of general relativistic magnetohydrodynamics for perfectly conducting fluids in Einstein--Maxwell--Euler spacetimes. The theory is applied to describe a neutron star that is rotating or is orbiting a black hole or another neutron star. Under the hypotheses of stationarity and axisymmetry, we obtain the equations governing magnetohydrodynamic equilibria of rotating neutron stars with poloidal, toroidal or mixed magnetic fields. Under the hypothesis of an approximate helical symmetry, we obtain the first law of thermodynamics governing magnetized equilibria of double neutron star or black hole - neutron star systems in close circular orbits. The first law is written as a relation between the change in the asymptotic Noether charge deltaQ and the changes in the area and electric charge of black holes, and in the vorticity, baryon rest mass, entropy, charge and magnetic flux of the magnetofluid. In an attempt to provide a better theoretical understanding of the methods used to construct models of isolated rotating stars and corotating or irrotational binaries and their unexplained convergence properties, we analytically examine the behavior of different iterative schemes near a static solution. We find the spectrum of the linearized iteration operator and show for self-consistent field methods that iterative instability corresponds to unstable modes of this operator. On the other hand, we show that the success of iteratively stable methods is due to (quasi-)nilpotency of this operator. Finally, we examine the integrability of motion of test particles in a stationary axisymmetric gravitational field. We use a direct approach to seek nontrivial constants of motion polynomial in the momenta---in addition to energy and angular momentum about the symmetry axis. We establish the existence and uniqueness of quadratic constants and the nonexistence of quartic constants for stationary axisymmetric Newtonian potentials with equatorial symmetry

  18. Recent Minima of 193 Eclipsing Binary Stars

    NASA Astrophysics Data System (ADS)

    Samolyk, G.

    2016-06-01

    This paper continues the publication of times of minima for eclipsing binary stars from observations reported to the AAVSO Eclipsing Binary section. Times of minima from CCD observations received by the author from November 2015 through January 2016 are presented.

  19. The rate of neutron star binary mergers in the universe - Minimal predictions for gravity wave detectors

    NASA Technical Reports Server (NTRS)

    Phinney, E. S.

    1991-01-01

    Of the many sources which gravitational wave observatories might see, merging neutron star binaries are the most predictable. Their waveforms at the observable frequencies are easy to calculate. And three systems which will merge in less than a Hubble time have already been observed as binary pulsars: two in the disk of the Galaxy, and one in a globular cluster. From the lifetimes and positions of these, a lower limit to the merger rate in the Galaxy and globular cluster system are inferred with confidence. Taking the merger rate in other galaxies to scale with the star formation rate, the merger rate expected in the local universe is computed. An ultraconservative lower limit to the rate gives three per year within 1 Gpc. The best estimate, still conservative in that it considers only systems like those already observed, gives three per year within 200 Mpc. An upper limit of three mergers per year within 23/h Mpc is set by the rate of Type Ib supernovae. The rates of black hole binary mergers and black hole-neutron star binary mergers are model-dependent, but could be comparable to the given rate of neutron-star binary mergers.

  20. Massive Stars in Interactive Binaries

    NASA Astrophysics Data System (ADS)

    St.-Louis, Nicole; Moffat, Anthony F. J.

    Massive stars start their lives above a mass of ~8 time solar, finally exploding after a few million years as core-collapse or pair-production supernovae. Above ~15 solar masses, they also spend most of their lives driving especially strong, hot winds due to their extreme luminosities. All of these aspects dominate the ecology of the Universe, from element enrichment to stirring up and ionizing the interstellar medium. But when they occur in close pairs or groups separated by less than a parsec, the interaction of massive stars can lead to various exotic phenomena which would not be seen if there were no binaries. These depend on the actual separation, and going from wie to close including colliding winds (with non-thermal radio emission and Wolf-Rayet dust spirals), cluster dynamics, X-ray binaries, Roche-lobe overflow (with inverse mass-ratios and rapid spin up), collisions, merging, rejuventation and massive blue stragglers, black-hole formation, runaways and gamma-ray bursts. Also, one wonders whether the fact that a massive star is in a binary affects its parameters compared to its isolated equivalent. These proceedings deal with all of these phenomena, plus binary statistics and determination of general physical properties of massive stars, that would not be possible with their single cousins. The 77 articles published in these proceedings, all based on oral talks, vary from broad revies to the lates developments in the field. About a third of the time was spent in open discussion of all participants, both for ~5 minutes after each talk and 8 half-hour long general dialogues, all audio-recorded, transcribed and only moderately edited to yield a real flavour of the meeting. The candid information in these discussions is sometimes more revealing than the article(s) that preceded them and also provide entertaining reading. The book is suitable for researchers and graduate students interested in stellar astrophysics and in various physical processes involved when

  1. Magnetic field effects on non-vacuum binaries

    NASA Astrophysics Data System (ADS)

    Anderson, Matthew; Hirschmann, Eric; Lehner, Luis; Liebling, Steven; Motl, Patrick; Neilsen, David; Palenzuela, Carlos; Tohline, Joel

    2009-05-01

    Observational evidence suggests that sizeable magnetic fields are present in a fair number of neutron star binaries and neutron star-black hole binaries. These magnetic fields can have a strong influence on the fluid's dynamics, the energetics of the system and even the production of gravitational radiation. We present results of non-vacuum binary neutron star and black hole- neutron star collisions and examine the influence of magnetic fields on the gravitational waves, fluid structure and dynamical behavior of the system.

  2. Terrestrial Planet Formation Around Close Binary Stars

    NASA Technical Reports Server (NTRS)

    Lissauer, Jack J.; Quintana, Elisa V.

    2003-01-01

    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.

  3. Cool Star Binaries with ALEXIS

    NASA Technical Reports Server (NTRS)

    Stern, Robert A.

    1998-01-01

    We proposed to search for high-temperature, flare-produced Fe XXIII line emission from active cool star binary systems using the ALEXIS all-sky survey. Previous X-ray transient searches with ARIEL V and HEAO-1, and subsequent shorter duration monitoring with the GINGA and EXOSAT satellites demonstrated that active binaries can produce large (EM approximately equals 10(exp 55-56/cu cm) X-ray flares lasting several hours or longer. Hot plasma from these flares at temperatures of 10(exp 7)K or more should produce Fe XXIII line emission at lambda = 132.8 A, very near the peak response of ALEXIS telescopes 1A and 2A. Our primary goals were to estimate flare frequency for the largest flares in the active binary systems, and, if the data permitted, to derive a distribution of flare energy vs. frequency for the sample as a whole. After a long delay due to the initial problems with the ALEXIS attitude control, the heroic efforts on the part of the ALEXIS satellite team enabled us to carry out this survey. However, the combination of the higher than expected and variable background in the ALEXIS detectors, and the lower throughput of the ALEXIS telescopes resulted in no convincing detections of large flares from the active binary systems. In addition, vignetting-corrected effective exposure times from the ALEXIS aspect solution were not available prior to the end of this contract; therefore, we were unable to convert upper limits measured in ALEXIS counts to the equivalent L(sub EUV).

  4. Terrestrial Planet Formation in Binary Star Systems

    NASA Technical Reports Server (NTRS)

    Lissauer, Jack J.; Quintana, Elisa V.; Chambers, John; Duncan, Martin J.; Adams, Fred

    2003-01-01

    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 within binary star systems, using a new, ultrafast, symplectic integrator that we have developed for this purpose. We show that the late stages of terrestrial planet formation can indeed take place in a wide variety of binary systems and we have begun to delineate the range of parameter space for which this statement is true. Results of our initial simulations of planetary growth around each star in the alpha Centauri system and other 'wide' binary systems, as well as around both stars in very close binary systems, will be presented.

  5. Close binary stars in globular clusters

    NASA Technical Reports Server (NTRS)

    Margon, Bruce

    1991-01-01

    Although close binary stars are thought theoretically to play a major role in globular cluster dynamics, virtually no non-degenerate close binaries are known in clusters. We review the status of observations in this area, and report on two new programs which are finally yielding candidate systems suitable for further study. One of the objects, a close eclipsing system in omega Cen, is also a big straggler, thus finally proving firm evidence that globular cluster blue stragglers really are binary stars.

  6. Encounters between binaries and neutron stars

    NASA Technical Reports Server (NTRS)

    Davies, M. B.; Benz, W.; Hills, J. G.

    1993-01-01

    We simulated encounters between a neutron star and primordial and tidal-capture binaries. In the case of encounters involving a tidal-capture binary, comprising a white dwarf and a main-sequence star, we find that most exchange encounters will produce a single merged object with the white dwarf and neutron star engulfed in a common envelope of gas donated by the main-sequence primary of the original binary. A small fraction of exchanges induce a merger of the white dwarf and main-sequence star, with this object being unbound to the neutron star, and the two objects having a large relative speed at infinity. For encounters involving a primordial binary, fewer encounters require the inclusion of hydrodynamical effects. Those involving collisions or close encounters tend to produce a binary comprised of the two merged stars (now forming one star) and the third star. The binaries produced typically have large enough separations to prevent the formation of a single merged object until subsequent stellar evolution of one of the components causes it to fill its Roche lobe. Clean exchanges produce binaries with large eccentricities; they are typically sufficiently wide to avoid circularization.

  7. Terrestrial Planet Formation in Binary Star Systems

    NASA Technical Reports Server (NTRS)

    Lissauer, J. J.; Quintana, E. V.; Adams, F. C.; Chambers, J. E.

    2006-01-01

    Most stars reside in binary/multiple star systems; however, previous models of planet formation have studied growth of bodies orbiting an isolated single star. Disk material has been observed around one or both components of various young close binary star systems. If planets form at the right places within such disks, they can remain dynamically stable for very long times. We have simulated the late stages of growth of terrestrial planets in both circumbinary disks around 'close' binary star systems with stellar separations ($a_B$) in the range 0.05 AU $\\le a_B \\le$ 0.4 AU and binary eccentricities in the range $0 \\le e \\le 0.8$ and circumstellar disks around individual stars with binary separations of tens of AU. 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 around individual stars in the Alpha Centauri system (Quintana et al. 2002, A.J., 576, 982); giant planets analogous to Jupiter and Saturn are included if their orbits are stable. The planetary systems formed around close binaries with stellar apastron distances less than or equal to 0.2 AU with small stellar eccentricities are very similar to those formed in the Sun-Jupiter-Saturn, whereas planetary systems formed around binaries with larger maximum separations tend to be sparser, with fewer planets, especially interior to 1 AU. Likewise, when the binary periastron exceeds 10 AU, terrestrial planets can form over essentially the entire range of orbits allowed for single stars with Jupiter-like planets, although fewer terrestrial planets tend to form within high eccentricity binary systems. As the binary periastron decreases, the radial extent of the terrestrial planet systems is reduced accordingly. When the periastron is 5 AU, the formation of Earth-like planets near 1 AU is compromised.

  8. Radio Detection of Neutron Star Binary Mergers

    NASA Astrophysics Data System (ADS)

    Bear, Brandon; Cardena, Brett; Dispoto, Dana; Papadopoulos, Joanna; Kavic, Michael; Simonetti, John

    2011-10-01

    Neutron star binary systems lose energy through gravitational radiation, and eventually merge. The gravitational radiation from the merger can be detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO). It is expected that a transient radio pulse will also be produced during the merger event. Detection of such radio transients would allow for LIGO to search for signals within constrained time periods. We calculate the LWA-1 detection rate of transient events from neutron star binary mergers. We calculate the detection rate of transient events from neutron star binary mergers for the Long Wavelength Array and the Eight-meter-wavelength Transient Array.

  9. Binary stars in the Orion Nebula Cluster

    NASA Astrophysics Data System (ADS)

    Köhler, R.; Petr-Gotzens, M. G.; McCaughrean, M. J.; Bouvier, J.; Duchêne, G.; Quirrenbach, A.; Zinnecker, H.

    2006-11-01

    We report on a high-spatial-resolution survey for binary stars in the periphery of the Orion Nebula Cluster, at 5-15 arcmin (0.65-2 pc) from the cluster center. We observed 228 stars with adaptive optics systems, in order to find companions at separations of 0.13 arcsec-1.12 arcsec (60-500 AU), and detected 13 new binaries. Combined with the results of Petr (1998), we have a sample of 275 objects, about half of which have masses from the literature and high probabilities to be cluster members. We used an improved method to derive the completeness limits of the observations, which takes into account the elongated point spread function of stars at relatively large distances from the adaptive optics guide star. The multiplicity of stars with masses >2 M⊙ is found to be significantly larger than that of low-mass stars. The companion star frequency of low-mass stars is comparable to that of main-sequence M-dwarfs, less than half that of solar-type main-sequence stars, and 3.5 to 5 times lower than in the Taurus-Auriga and Scorpius-Centaurus star-forming regions. We find the binary frequency of low-mass stars in the periphery of the cluster to be the same or only slightly higher than for stars in the cluster core (<3 arcmin from θ^1C Ori). This is in contrast to the prediction of the theory that the low binary frequency in the cluster is caused by the disruption of binaries due to dynamical interactions. There are two ways out of this dilemma: Either the initial binary frequency in the Orion Nebula Cluster was lower than in Taurus-Auriga, or the Orion Nebula Cluster was originally much denser and dynamically more active.

  10. Binary Stars in the Orion Nebula Cluster

    NASA Astrophysics Data System (ADS)

    Köhler, Rainer; Petr-Gotzens, Monika G.; McCaughrean, Mark J.; Bouvier, Jerome; Duchêne, Gaspard; Quirrenbach, Andreas; Zinnecker, Hans

    2007-08-01

    We report on a high-spatial-resolution survey for binary stars in the periphery of the Orion Nebula Cluster, at 5 - 15 arcmin (0.65 - 2 pc) from the cluster center. We observed 228 stars with adaptive optics systems, in order to find companions at separations of 0.13 - 1.12 arcsec (60 - 500 AU), and detected 13 new binaries. Combined with the results of Petr (1998), we have a sample of 275 objects, about half of which have masses from the literature and high probabilities to be cluster members. We used an improved method to derive the completeness limits of the observations, which takes into account the elongated point spread function of stars at relatively large distances from the adaptive optics guide star. The multiplicity of stars with masses >2 Msun is found to be significantly larger than that of low-mass stars. The companion star frequency of low-mass stars is comparable to that of main-sequence M-dwarfs, less than half that of solar-type main-sequence stars, and 3.5 to 5 times lower than in the Taurus-Auriga and Scorpius-Centaurus star-forming regions. We find the binary frequency of low-mass stars in the periphery of the cluster to be the same or only slightly higher than for stars in the cluster core (<3 arcmin from θ1C Ori). This is in contrast to the prediction of the theory that the low binary frequency in the cluster is caused by the disruption of binaries due to dynamical interactions. There are two ways out of this dilemma: Either the initial binary frequency in the Orion Nebula Cluster was lower than in Taurus-Auriga, or the Orion Nebula Cluster was originally much denser and dynamically more active.

  11. Recent Minima of 171 Eclipsing Binary Stars

    NASA Astrophysics Data System (ADS)

    Samolyk, G.

    2015-12-01

    This paper continues the publication of times of minima for 171 eclipsing binary stars from observations reported to the AAVSO EB section. Times of minima from observations received by the author from March 2015 thru October 2015 are presented.

  12. BLACK HOLE-NEUTRON STAR MERGERS AND SHORT GAMMA-RAY BURSTS: A RELATIVISTIC TOY MODEL TO ESTIMATE THE MASS OF THE TORUS

    SciTech Connect

    Pannarale, Francesco; Tonita, Aaryn; Rezzolla, Luciano E-mail: aaryn.tonita@aei.mpg.de

    2011-02-01

    The merger of a binary system composed of a black hole (BH) and a neutron star (NS) may leave behind a torus of hot, dense matter orbiting around the BH. While numerical-relativity simulations are necessary to simulate this process accurately, they are also computationally expensive and unable at present to cover the large space of possible parameters, which include the relative mass ratio, the stellar compactness, and the BH spin. To mitigate this and provide a first reasonable coverage of the space of parameters, we have developed a method for estimating the mass of the remnant torus from BH-NS mergers. The toy model makes use of an improved relativistic affine model to describe the tidal deformations of an extended tri-axial ellipsoid orbiting around a Kerr BH and measures the mass of the remnant torus by considering which of the fluid particles composing the star are on bound orbits at the time of the tidal disruption. We tune the toy model by using the results of fully general-relativistic simulations obtaining relative precisions of a few percent and use it to investigate the space of parameters extensively. In this way, we find that the torus mass is largest for systems with highly spinning BHs, small stellar compactnesses, and large mass ratios. As an example, tori as massive as M{sub b,tor} {approx_equal} 1.33 M{sub sun} can be produced for a very extended star with compactness C {approx_equal} 0.1 inspiralling around a BH with dimensionless spin parameter a = 0.85 and mass ratio q {approx_equal} 0.3. However, for a more astrophysically reasonable mass ratio q {approx_equal} 0.14 and a canonical value of the stellar compactness C {approx_equal} 0.145, the toy model sets a considerably smaller upper limit of M{sub b,tor} {approx}< 0.34 M{sub sun}.

  13. Eclipsing Binary B-Star Mass Determinations

    NASA Astrophysics Data System (ADS)

    Townsend, Amanda; Eikenberry, Stephen S.

    2016-01-01

    B-stars in binary pairs provide a laboratory for key astrophysical measurements of massive stars, including key insights for the formation of compact objects (neutron stars and black holes). In their paper, Martayan et al (2004) find 23 Be binary star pairs in NGC2004 in the Large Magellanic Cloud, five of which are both eclipsing and spectroscopic binaries with archival data from VLT-Giraffe and photometric data from MACHO. By using the Wilson eclipsing binary code (e.g., Wilson, 1971), we can determine preliminary stellar masses of the binary components. We present the first results from this analysis. This study also serves as proof-of-concept for future observations with the Photonic Synthesis Telescope Array (Eikenberry et al., in prep) that we are currently building for low-cost, precision spectroscopic observations. With higher resolution and dedicated time for observations, we can follow-up observations of these Be stars as well as Be/X-ray binaries, for improved mass measurements of neutron stars and black holes and better constraints on their origin/formation.

  14. Binary Star database BDB: datasets and services

    NASA Astrophysics Data System (ADS)

    Malkov, O. Yu.; Kaygorodov, P. V.; Koravleva, D. A.; Oblak, E.; Debray, B.

    Description of the Binary star DataBase (BDB, http://bdb.inasan.ru), the world's principal database of binary and multiple systems of all observational types, is presented in the paper. BDB contains data on physical and positional parameters of 100,000 components of 40,000 systems of multiplicity 2 to 20, belonging to various observational types: visual, spectroscopic, eclipsing, etc. Information on these types of binaries is obtained from heterogeneous sources of data astronomical catalogues and surveys. Organization of the information is based on the careful cross-identification of the objects. BDB can be queried by star identifier, coordinates, and other paramete

  15. Contact binary stars as standard candles

    NASA Astrophysics Data System (ADS)

    Klagyivik, P.; Csizmadia, Sz.

    2004-06-01

    Rucinski (1996) suggested to use contact binary stars as standard candles. We investigated the properties of contact binary stars in order to search for possibility of their using as standard candles. For this purpose a catalogue of their light curve solution was compiled and on the basis of the catalogue data we calculated the rate of energy transfer between the two components. This allowed us to determine the mass-luminosity relation of the primary as well as secondary components in a contact binary and using Kepler's third law and the strict geometry a very reliable distance determination method was developed.

  16. Exploring the Birth of Binary Stars

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-08-01

    More than half of all stars are thought to be in binary or multiple star systems. But how do these systems form? The misaligned spins of some binary protostars might provide a clue.Two Formation ModelsIts hard to tell how multiple-star systems form, since these systems are difficult to observe in their early stages. But based on numerical simulations, there are two proposed models for the formation of stellar binaries:Turbulent fragmentationTurbulence within a single core leads to multiple dense clumps. These clumps independently collapse to form stars that orbit each other.Disk fragmentationGravitational instabilities in a massive accretion disk cause the formation of a smaller, secondary disk within the first, resulting in two stars that orbit each other.Log column density for one of the authors simulated binary systems, just after the formation of two protostars. Diamonds indicate the protostar positions. [Adapted from Offner et al. 2016]Outflows as CluesHow can we differentiate between these formation mechanisms? Led by Stella Offner (University of Massachusetts), a team of scientists has suggested that the key isto examine the alignment of the stars protostellar outflows jets that are often emitted from the poles of young, newly forming stars.Naively, wed expect that disk fragmentation would produce binary stars with common angular momentum. As the stars spins would be aligned, they would therefore also launch protostellar jets that were aligned with each other. Turbulent fragmentation, on the other hand, would cause the stars to have independent angular momentum. This would lead to randomly oriented spins, so the protostellar jets would be misaligned.Snapshots from the authors simulations. Left panel of each pair: column density; green arrows giveprotostellar spin directions. Right panel: synthetic observations produced from the simulations; cyan arrows giveprotostellar outflow directions. [Offner et al. 2016]Simulations of FragmentationIn order to better

  17. Last orbits of binary strange quark stars

    SciTech Connect

    Limousin, Francois; Gourgoulhon, Eric; Gondek-Rosinska, Dorota

    2005-03-15

    We present the first relativistic calculations of the final phase of inspiral of a binary system consisting of two stars built predominantly of strange quark matter (strange quark stars). We study the precoalescing stage within the Isenberg-Wilson-Mathews approximation of general relativity using a multidomain spectral method. A hydrodynamical treatment is performed under the assumption that the flow is either rigidly rotating or irrotational, taking into account the finite density at the stellar surface--a distinctive feature with respect to the neutron star case. The gravitational-radiation driven evolution of the binary system is approximated by a sequence of quasiequilibrium configurations at fixed baryon number and decreasing separation. We find that the innermost stable circular orbit (ISCO) is given by an orbital instability both for synchronized and irrotational systems. This contrasts with neutron stars for which the ISCO is given by the mass-shedding limit in the irrotational case. The gravitational wave frequency at the ISCO, which marks the end of the inspiral phase, is found to be {approx}1400 Hz for two irrotational 1.35 M{sub {center_dot}} strange stars and for the MIT bag model of strange matter with massless quarks and a bag constant B=60 MeV fm{sup -3}. Detailed comparisons with binary neutrons star models, as well as with third order post-Newtonian point-mass binaries are given.

  18. Adiabatic Mass Loss Model in Binary Stars

    NASA Astrophysics Data System (ADS)

    Ge, H. W.

    2012-07-01

    Rapid mass transfer process in the interacting binary systems is very complicated. It relates to two basic problems in the binary star evolution, i.e., the dynamically unstable Roche-lobe overflow and the common envelope evolution. Both of the problems are very important and difficult to be modeled. In this PhD thesis, we focus on the rapid mass loss process of the donor in interacting binary systems. The application to the criterion of dynamically unstable mass transfer and the common envelope evolution are also included. Our results based on the adiabatic mass loss model could be used to improve the binary evolution theory, the binary population synthetic method, and other related aspects. We build up the adiabatic mass loss model. In this model, two approximations are included. The first one is that the energy generation and heat flow through the stellar interior can be neglected, hence the restructuring is adiabatic. The second one is that he stellar interior remains in hydrostatic equilibrium. We model this response by constructing model sequences, beginning with a donor star filling its Roche lobe at an arbitrary point in its evolution, holding its specific entropy and composition profiles fixed. These approximations are validated by the comparison with the time-dependent binary mass transfer calculations and the polytropic model for low mass zero-age main-sequence stars. In the dynamical time scale mass transfer, the adiabatic response of the donor star drives it to expand beyond its Roche lobe, leading to runaway mass transfer and the formation of a common envelope with its companion star. For donor stars with surface convection zones of any significant depth, this runaway condition is encountered early in mass transfer, if at all; but for main sequence stars with radiative envelopes, it may be encountered after a prolonged phase of thermal time scale mass transfer, so-called delayed dynamical instability. We identify the critical binary mass ratio for the

  19. A field guide to the binary stars

    NASA Astrophysics Data System (ADS)

    Trimble, V.

    1983-05-01

    Details and examples of the six phases of existence for a binary star system are described. The birth and pre-main-sequence contraction is generally obscured from observation by the presence of gas and dust clouds; it comprises 1/1000th of a system's lifetime. The main sequence, i.e., hydrogen burning, takes up to 90 pct of a star's lifetime, and has been detected in stars with masses ranging from 0.07-32 solar masses. In binary systems, the main sequence stars may or may not interact, or one companion may burn out before the other leaves the main sequence. The primary in a binary system expands to fill its Roche lobe before mass transfer begins, then continues on a Kelvin-Helmholtz time scale until the primary is smaller than the secondary, when transfer proceeds on a nuclear time scale. The depletion of hydrogen fuel or He ignition stops the mass transfer, leading to formation of a white dwarf, neutron star, or supernova that sends both the neutron star and the OB secondary off at high speeds. Back transfer can be initiated in a fifth phase and can produce black holes or dwarf novae, or supernovae. Finally, the system terminates when both stars are extinguished and fall into one another, which can also yield supernovae or black holes.

  20. Binary Origin of Blue Straggler Stars in Star Clusters

    NASA Astrophysics Data System (ADS)

    Xin, Yu

    2015-08-01

    Close-binary evolution is one of the major formation channels of blue straggler stars (BSSs). We present binary evolution models, including case-A and/or case-B mass transfer (MT) in the intermediate- and low-mass stars, to try to understand the binary origin of BSS populations in star clusters. With the help of Monte-Carlo simulations, we compared the distribution of our synthetic MT BSSs with observations in the color-magnitude diagram (CMD) of M67 and M30. The current results show that primordial binary MT can only contribute to a small part of BSSs in M67, and it can credibly explain the formation of the red-BSS sequence observed in the CMD of M30. We also analyzed the spectral properties of BSS populations in open clusters (OCs) based on the LAMOST data, and a small part of BSSs indeed present Carbon depletion compared with the main sequence stars, which indicate their binary origin. Unfortunately, a statistical resfult of how much the binary MT can contribute to BSS fomation in OCs still requires larger working sample.

  1. Interrupted Binary Mass Transfer in Star Clusters

    NASA Astrophysics Data System (ADS)

    Leigh, Nathan W. C.; Geller, Aaron M.; Toonen, Silvia

    2016-02-01

    Binary mass transfer (MT) is at the forefront of some of the most exciting puzzles of modern astrophysics, including SNe Ia, gamma-ray bursts, and the formation of most observed exotic stellar populations. Typically, the evolution is assumed to proceed in isolation, even in dense stellar environments such as star clusters. In this paper, we test the validity of this assumption via the analysis of a large grid of binary evolution models simulated with the SeBa code. For every binary, we calculate analytically the mean time until another single or binary star comes within the mean separation of the mass-transferring binary, and compare this timescale to the mean time for stable MT to occur. We then derive the probability for each respective binary to experience a direct dynamical interruption. The resulting probability distribution can be integrated to give an estimate for the fraction of binaries undergoing MT that are expected to be disrupted as a function of the host cluster properties. We find that for lower-mass clusters (≲ {10}4 {M}⊙ ), on the order of a few to a few tens of percent of binaries undergoing MT are expected to be interrupted by an interloping single, or more often binary, star, over the course of the cluster lifetime, whereas in more massive globular clusters we expect \\ll 1% to be interrupted. Furthermore, using numerical scattering experiments performed with the FEWBODY code, we show that the probability of interruption increases if perturbative fly-bys are considered as well, by a factor ˜2.

  2. Are All Dwarf Carbon Stars Binary?

    NASA Astrophysics Data System (ADS)

    Farihi, Jay; Harris, Hugh; Subasavage, John; Bergfors, Carolina; Green, Paul; Gansicke, Boris

    2014-08-01

    The origin of dwarf carbon stars is a persistent astrophysical curiosity dating back to 1977. Only giant stars dredge up interior carbon, and hence the discovery of an unevolved dwarf star with C/O >1 was a big surprise. Astronomers are no closer to understanding these rare and spectrally peculiar stars 37 years later(!). The bulk of dwarf carbon stars show no sign of an evolved companion necessary to account for their externally polluted atmospheres. These stars are sensitive tracers of Galactic chemical evolution and star formation, and provide strong constraints on the potential for carbon-dominated (single star) planetary systems. We propose to conclusively validate or refute the hypothetical binary nature of dwarf carbon stars, and hence their chemical and physical formation channel(s). For all binaries, we will initially constrain and eventually measure orbital periods. By determining their physical separation during the previous epoch of mass transfer, we will distinguish between the Roche lobe overflow and wind capture models for the creation of carbon dwarfs.

  3. The evolution of close binary stars

    NASA Astrophysics Data System (ADS)

    Tutukov, A. V.; Cherepashchuk, A. M.

    2016-05-01

    A review of our current understanding of the physics and evolution of close binary stars with various masses under the influence of the nuclear evolution of their components and their magnetic stellar winds is presented. The role of gravitational-wave radiation by close binaries on their evolution and the loss of their orbital angular momentum is also considered. The final stages in the evolution of close binary systems are described. The review also notes the main remaining tasks related to studies of the physics and evolution of various classes of close binaries, including analyses of collisions of close binaries and supermassive black holes in galactic nuclei. Such a collision could lead to the capture of one of the components by the black hole and the acceleration of the remaining component to relativistic speeds.

  4. Dynamics and Habitability in Binary Star Systems

    NASA Astrophysics Data System (ADS)

    Eggl, Siegfried; Georgakarakos, Nikolaos; Pilat-Lohinger, Elke

    2014-07-01

    Determining planetary habitability is a complex matter, as the interplay between a planet's physical and atmospheric properties with stellar insolation has to be studied in a self consistent manner. Standardized atmospheric models for Earth-like planets exist and are commonly accepted as a reference for estimates of Habitable Zones. In order to define Habitable Zone boundaries, circular orbital configurations around main sequence stars are generally assumed. In gravitationally interacting multibody systems, such as double stars, however, planetary orbits are forcibly becoming non circular with time. Especially in binary star systems even relatively small changes in a planet's orbit can have a large impact on habitability. Hence, we argue that a minimum model for calculating Habitable Zones in binary star systems has to include dynamical interactions.

  5. White dwarfs in Be star binary systems

    NASA Technical Reports Server (NTRS)

    Apparao, K. M. V.

    1991-01-01

    An evaluation is made of possible reasons for the persistent inability to identify white dwarf stars in the Be binary systems. It is noted that many Be stars exhibiting large optical enhancements may be Be + WD and Be + He systems, and that observations of pulsations in the H-alpha emission, as well as observation of time delays between enhancements of optical line and continuum, can identify such systems.

  6. Merger of Magnetized Binary Neutron Stars

    NASA Astrophysics Data System (ADS)

    Motl, Patrick M.; Anderson, Matthew; Lehner, Luis; Liebling, Steven L.; Hirschmann, Eric; Neilsen, David; Palenzuela, Carlos

    2016-01-01

    We present simulations of the merger of binary neutron star systems calculated with full general relativity and incorporating the global magnetic field structure for the stars evolved with resistive magnetohydrodynamics. We also incorporate the effects of neutrino transport and tabular equations of state to describe the degenerate matter. We gratefully acknowledge the support of NASA through the Astrophysics Theory Program grant NNX13AH01G.

  7. An electrically powered binary star?

    NASA Astrophysics Data System (ADS)

    Wu, Kinwah; Cropper, Mark; Ramsay, Gavin; Sekiguchi, Kazuhiro

    2002-03-01

    We propose a model for stellar binary systems consisting of a magnetic and a non-magnetic white dwarf pair which is powered principally by electrical energy. In our model the luminosity is caused by resistive heating of the stellar atmospheres arising from induced currents driven within the binary. This process is reminiscent of the Jupiter-Io system, but greatly increased in power because of the larger companion and stronger magnetic field of the primary. Electrical power is an alternative stellar luminosity source, following on from nuclear fusion and accretion. We find that this source of heating is sufficient to account for the observed X-ray luminosity of the 9.5-min binary RX J1914+24, and provides an explanation for its puzzling characteristics.

  8. Orbits of Six Binary Stars

    NASA Astrophysics Data System (ADS)

    Olevic, D.; Cvetkovic, Z.

    2005-04-01

    Preliminary orbital elements of binary systems WDS 03494-1956 = RST 2324, WDS 03513+2621 = A 1830, WDS 04093-2025 = RST 2333, WDS 06485-1226 = A 2935, WDS 07013-0906 = A 671, and WDS 18323-1439 = CHR 73 are presented. For all systems but WDS 18323-1439 the individual masses and dynamical parallaxes are derived.

  9. FU Orionis: A Binary Star?

    NASA Astrophysics Data System (ADS)

    Wang, Hongchi; Apai, Dániel; Henning, Thomas; Pascucci, Ilaria

    2004-01-01

    By using the Adaptive Optics with a Laser for Astronomy system at the 3.6 m telescope of the Calar Alto Observatory, we detected a faint red star in the apparent vicinity of FU Ori, the prototype of the FUor outburst stars. Independent confirmation of the detection is obtained from archival Probing the Universe with Enhanced Optics/Canada-France-Hawaii Telescope images. The separation between the companion candidate and FU Ori is 0.50", and their brightness contrast is around 4 mag. We discuss the possible nature of the newly detected star based on near-infrared photometry and its proper motion relative to FU Ori. The photometric data are consistent with a nearby late-type main-sequence star, a background giant star, and a pre-main-sequence star. On the basis of the proper motion and the stellar surface density in the direction toward FU Ori, we argue that the probabilities of the first two options are very low.

  10. Division G Commission 42: Close Binary Stars

    NASA Astrophysics Data System (ADS)

    Richards, Mercedes T.; Pribulla, Theodor; Ribas, Ignasi; Bradstreet, David H.; Dreschsel, Horst; Maceroni, Carla; Mikolajewska, Joanna; Munari, Ulisse; Prsa, Andrej; Scharfe, Colin; Southworth, John; Trimble, Virginia

    2016-04-01

    Commission 42 began life as Photometric Double Stars in 1948 at the 7th General Assembly in Zurich, under the presidency of Zdenek Kopal. As early as 1961, then General Secretary Lukas Plaut recommended a merger between C42 and C26, Double Stars, one of the original 32 commissions going back to 1919-22 (first president Aitken, assistant director at Lick). C42 became Close Binary Stars in 1970, at the 14th GA in Brighton (the first one I attended). Table 1 shows the presidents of C42, and vice presidents, from when the office started, through the history of the Commission.

  11. Nonparametric statistical modeling of binary star separations

    NASA Astrophysics Data System (ADS)

    Heacox, William D.; Gathright, John

    1994-09-01

    We develop a comprehensive statistical model for the distribution of observed separations in binary star systems, in terms of distributions of orbital elements, projection effects, and distances to systems. We use this model to derive several diagnostics for estimating the completeness of imaging searches for stellar companions, and the underlying stellar multiplicities. In application to recent imaging searches for low-luminosity companions to nearby M dwarf stars, and for companions to young stars in nearby star-forming regions, our analyses reveal substantial uncertainty in estimates of stellar multiplicity. For binary stars with late-type dwarf companions, semimajor axes appear to be distributed approximately as a-1 for values ranging from about one to several thousand astronomical units. About one-quarter of the companions to field F and G dwarf stars have semimajor axes less than 1 AU, and about 15% lie beyond 1000 AU. The geometric efficiency (fraction of companions imaged onto the detector) of imaging searches is nearly independent of distances to program stars and orbital eccentricities, and varies only slowly with detector spatial limitations.

  12. Nonparametric statistical modeling of binary star separations

    NASA Technical Reports Server (NTRS)

    Heacox, William D.; Gathright, John

    1994-01-01

    We develop a comprehensive statistical model for the distribution of observed separations in binary star systems, in terms of distributions of orbital elements, projection effects, and distances to systems. We use this model to derive several diagnostics for estimating the completeness of imaging searches for stellar companions, and the underlying stellar multiplicities. In application to recent imaging searches for low-luminosity companions to nearby M dwarf stars, and for companions to young stars in nearby star-forming regions, our analyses reveal substantial uncertainty in estimates of stellar multiplicity. For binary stars with late-type dwarf companions, semimajor axes appear to be distributed approximately as a(exp -1) for values ranging from about one to several thousand astronomical units. About one-quarter of the companions to field F and G dwarf stars have semimajor axes less than 1 AU, and about 15% lie beyond 1000 AU. The geometric efficiency (fraction of companions imaged onto the detector) of imaging searches is nearly independent of distances to program stars and orbital eccentricities, and varies only slowly with detector spatial limitations.

  13. Component Properties of T Tauri Star Binaries

    NASA Astrophysics Data System (ADS)

    Muzzio, Ryan; L. Prato, T. Allen, N. Wright-Garba, L. Biddle, J. McLane (Lowell Observatory), G. Schaefer (GSU & CHARA)

    2016-01-01

    This poster describes our study of the properties of individual components of young T Tauri binary stars. We observed about 100 multi-star systems in the near-infrared, within the relatively close star forming regions Taurus and Ophiuchus. Here we specifically focus on four systems in the Taurus sample, IS Tau, UZ Tau B, IW Tau, and Haro 6- 37 A. Their spectra were taken with the Keck 2 telescope's NIRSPEC spectrograph and the imaging data with the Keck 2 NIRC2 camera, both with adaptive optics. Properties that we determined include spectral type, radial velocity, vsini, veiling, and near-infrared colors. On the basis of these data, we estimate stellar and circumstellar disk properties for the subset of binaries presented here.

  14. The impact of IUE on binary star studies

    NASA Technical Reports Server (NTRS)

    Plavec, M. J.

    1981-01-01

    The use of IUE observations in the investigation of binary stars is discussed. The results of data analysis of several classes of binary systems are briefly reviewed including zeta Aurigae and VV Cephei stars, mu Sagittarii, epsilon Aurigae, beta Lyrae and the W Serpentis stars, symbiotic stars, and the Algols.

  15. Transit Timing Variations In Binary Star Systems

    NASA Astrophysics Data System (ADS)

    Sansone, Eric; Haghighipour, N.

    2012-01-01

    We present the results of a study of the effect of a stellar companion on the transit timing variations (TTV) of a planetary system. The purpose of our study is to determine the ranges of the orbital elements of a secondary star for which the amplitude of a currently existing TTV is enhanced. We chose the system of Kepler 9 as this system represents the first planetary system detected by the transit timing variation method, and studied its TTVs by considering a hypothetical secondary star in this system. By varying the mass, semi-major axis, and eccentricity of the fictitious binary companion, we tested the stability of the known planets Kepler-9c and Kepler-9b and identified the region of the parameter-space for which the binary planetary system would be stable. We calculated TTVs for the two planets of the system for different values of the orbital elements of the secondary star and calculated its difference with the system's already existing TTVs. Results of our study indicate that the effect of the binary companion is significant only when the secondary star is in a highly eccentric orbit and/or the planets of the system are within the range of Super-Earth or terrestrial sizes. This work was funded by the National Science Foundation in the form of a Research Experience for Undergraduates program at the University of Hawaii at Manoa.

  16. Light curves from binary neutron star coalescence

    NASA Astrophysics Data System (ADS)

    Ortiz, Nestor; Green, Stephen; Lehner, Luis; Ponce, Marcelo; HAD Collaboration

    2015-04-01

    Evolution of binary neutron stars, and the extraction of associated gravitational waveforms, have acquired certain maturity using numerical simulations. In this work we look to augment the observational predictions by extracting electromagnetic counterparts. That is, given results from a merger simulation, we produce a photon emission sky map. Our ray-tracing algorithm employ the two-pole caustic model of gamma-ray emission from the binary system's magnetosphere. The combined measurement of both gravitational and electromagnetic wave signals provides additional information to characterize the merger.

  17. Binary-binary collisions involving main-sequence stars, white dwarfs and neutron stars in globular clusters

    SciTech Connect

    Leonard, P.J.T.; Davies, M.B.

    1993-12-31

    We consider collisions between dynamically-evolved primordial binaries consisting of main-sequence stars, white dwarfs and neutron stars in globular clusters. In our four-body binary-binary scattering experiments, we allow stars to ``stick`` if they pass close enough to each other, which leads to the formation of a wide variety of exotic objects. Most of these objects have binary companions. Also, relatively clean exchange interactions can produce binaries containing neutron stars that eventually receive material from their companions. Such systems will be observable as X-ray binaries.

  18. On the formation of Be stars through binary interaction

    SciTech Connect

    Shao, Yong; Li, Xiang-Dong

    2014-11-20

    Be stars are rapidly rotating B-type stars. The origin of their rapid rotation is not certain, but binary interaction remains as a possibility. In this work, we investigate the formation of Be stars resulting from mass transfer in binaries in the Galaxy. We calculate binary evolution with both stars evolving simultaneously and consider different possible mass accretion histories for the accretor. From the calculated results, we obtain the critical mass ratios q {sub cr} that determine the stability of the mass transfer. We also numerically calculate the parameter λ in common envelope evolution and then incorporate both q {sub cr} and λ into the population synthesis calculations. We present the predicted numbers and characteristics of Be stars in binary systems with different types of companions, including helium stars, white dwarfs, neutron stars, and black holes. We find that in Be/neutron star binaries, the Be stars can have a lower mass limit ∼8 M {sub ☉} if they are formed by stable (i.e., without the occurrence of common envelope evolution) and nonconservative mass transfer. We demonstrate that isolated Be stars may originate from both mergers of two main-sequence stars and disrupted Be binaries during the supernova explosions of the primary stars, but mergers seem to play a much more important role. Finally, the fraction of Be stars that have involved binary interactions in all B-type stars can be as high as ∼13%-30%, implying that most Be stars may result from binary interaction.

  19. Binary neutron stars with arbitrary spins in numerical relativity

    NASA Astrophysics Data System (ADS)

    Tacik, Nick; Foucart, Francois; Pfeiffer, Harald P.; Haas, Roland; Ossokine, Serguei; Kaplan, Jeff; Muhlberger, Curran; Duez, Matt D.; Kidder, Lawrence E.; Scheel, Mark A.; Szilágyi, Béla

    2015-12-01

    We present a code to construct initial data for binary neutron star systems in which the stars are rotating. Our code, based on a formalism developed by Tichy, allows for arbitrary rotation axes of the neutron stars and is able to achieve rotation rates near rotational breakup. We compute the neutron star angular momentum through quasilocal angular momentum integrals. When constructing irrotational binary neutron stars, we find a very small residual dimensionless spin of ˜2 ×10-4 . Evolutions of rotating neutron star binaries show that the magnitude of the stars' angular momentum is conserved, and that the spin and orbit precession of the stars is well described by post-Newtonian approximation. We demonstrate that orbital eccentricity of the binary neutron stars can be controlled to ˜0.1 % . The neutron stars show quasinormal mode oscillations at an amplitude which increases with the rotation rate of the stars.

  20. Coalescence of Magnetized Binary Neutron Star Systems

    NASA Astrophysics Data System (ADS)

    Motl, Patrick M.; Anderson, Matthew; Lehner, Luis; Liebling, Steven L.; Neilsen, David; Palenzuela, Carlos; Ponce, Marcelo

    2015-01-01

    We present simulations of the merger of binary neutron star systems calculated with full general relativity and incorporating the global magnetic field structure for the stars evolved with resistive magnetohydrodynamics. Our simulation tools have recently been improved to incorporate the effects of neutrino cooling and have been generalized to allow for tabular equations of state to describe the degenerate matter. Of particular interest are possible electromagnetic counterparts to the gravitational radiation that emerges from these systems. We focus on magnetospheric interactions that ultimately tap into the gravitational potential energy of the binary to power a Poynting flux and deposition of energy through Joule heating and magnetic reconnection. We gratefully acknowledge the support of NASA through the Astrophysics Theory Program grant NNX13AH01G.

  1. Mergers of Binary Neutron Star Systems

    NASA Astrophysics Data System (ADS)

    Motl, Patrick M.; Anderson, Matthew; Lehner, Luis; Liebling, Steven; Neilsen, David; Palenzuela, Carlos

    2016-04-01

    We present results from fully relativistic simulations of binary neutron star mergers varying the tabular equation of state used to approximate the degenerate material and the mass ratio. The simulations incorporate both magnetic fields and the effects of neutrino cooling. In particular, we examine the amount and properties of material ejected from the merger. We gratefully acknowledge the support of NASA through the Astrophysics Theory Program grant NNX13AH01G.

  2. Nonlinear Tides in Coalescing Binary Neutron Stars

    NASA Astrophysics Data System (ADS)

    Weinberg, Nevin

    2016-03-01

    Coalescing binary neutron stars are among the most promising sources for ground-based gravitational wave detectors such as Advanced LIGO. Tidal interactions in such systems extract energy from the orbit and, at some level, modify the gravitational wave signal. Previous studies found that tidal effects are probably too small to be detected from individual systems with LIGO. However, these studies typically assumed that the tide can be treated as a linear perturbation to the star. I will show that the linear approximation is invalid even during the early stages of inspiral and that nonlinear fluid effects in the form of tide-internal wave interactions become important around the time the binary first enters LIGO's bandpass (at gravitational wave frequencies around 30 Hz). Although the precise influence of nonlinear fluid effects is not yet well constrained, I will show that they may significantly modify the gravitational wave signal and electromagnetic emission from coalescing binary neutron stars. This research was supported by NASA Grant NNX14AB40G.

  3. A Numerical Study of Boson Star Binaries

    NASA Astrophysics Data System (ADS)

    Mundim, Bruno C.

    2010-02-01

    This thesis describes a numerical study of binary boson stars within the context of an approximation to general relativity. The approximation we adopt places certain restrictions on the dynamical variables of general relativity (conformal flatness of the 3-metric), and on the time-slicing of the spacetime (maximal slicing). The resulting modeling problem requires the solution of a coupled nonlinear system of 4 hyperbolic, and 5 elliptic partial differential equations (PDEs) in three space dimensions and time. We approximately solve this system as an initial-boundary value problem, using finite difference techniques and well known, computationally efficient numerical algorithms such as the multigrid method in the case of the elliptic equations. Careful attention is paid to the issue of code validation, and a key part of the thesis is the demonstration that, as the basic scale of finite difference discretization is reduced, our numerical code generates results that converge to a solution of the continuum system of PDEs as desired. The thesis concludes with a discussion of results from some initial explorations of the orbital dynamics of boson star binaries. In particular, we describe calculations in which motion of such a binary is followed for more than two orbital periods, which is a significant advance over previous studies. We also present results from computations in which the boson stars merge, and where there is evidence for black hole formation.

  4. Binary interaction dominates the evolution of massive stars.

    PubMed

    Sana, H; de Mink, S E; de Koter, A; Langer, N; Evans, C J; Gieles, M; Gosset, E; Izzard, R G; Le Bouquin, J-B; Schneider, F R N

    2012-07-27

    The presence of a nearby companion alters the evolution of massive stars in binary systems, leading to phenomena such as stellar mergers, x-ray binaries, and gamma-ray bursts. Unambiguous constraints on the fraction of massive stars affected by binary interaction were lacking. We simultaneously measured all relevant binary characteristics in a sample of Galactic massive O stars and quantified the frequency and nature of binary interactions. More than 70% of all massive stars will exchange mass with a companion, leading to a binary merger in one-third of the cases. These numbers greatly exceed previous estimates and imply that binary interaction dominates the evolution of massive stars, with implications for populations of massive stars and their supernovae. PMID:22837522

  5. B-type stars in eclipsing binaries

    NASA Astrophysics Data System (ADS)

    Ratajczak, Milena; Pigulski, Andrzej

    2016-07-01

    B-type stars in eclipsing binary systems are unique astrophysical tools to test several aspects of stellar evolution. Such objects can be used e.g. to determine the masses of Beta Cephei variable stars, as well as help to place tighter constraints on the value of the convective core overshooting parameter α. Both precise photometry and high-resolution spectroscopy with high SNR are required to achieve these goals, but since many of the targets are bright enough, the challenge is fair. Following this assumption, we shall explain how we plan to examine both the aforementioned aspects of stellar evolution using observations of B-type stars obtained with a wide range of spectrographs, as well as BRITE-Constellation satellites.

  6. Coordinate System Issues in Binary Star Computations

    NASA Astrophysics Data System (ADS)

    Kaplan, George H.

    2015-08-01

    It has been estimated that half of all stars are components of binary or multiple systems. Yet the number of known orbits for astrometric and spectroscopic binary systems together is less than 7,000 (including redundancies), almost all of them for bright stars. A new generation of deep all-sky surveys such as Pan-STARRS, Gaia, and LSST are expected to lead to the discovery of millions of new systems. Although for many of these systems, the orbits may be undersampled initially, it is to be expected that combinations of new and old data sources will eventually lead to many more orbits being known. As a result, a revolution in the scientific understanding of these systems may be upon us.The current database of visual (astrometric) binary orbits represents them relative to the “plane of the sky”, that is, the plane orthogonal to the line of sight. Although the line of sight to stars constantly changes due to proper motion, aberration, and other effects, there is no agreed upon standard for what line of sight defines the orbital reference plane. Furthermore, the computation of differential coordinates (component B relative to A) for a given date must be based on the binary system’s direction at that date. Thus, a different “plane of the sky” is appropriate for each such date, i.e., each observation. However, projection effects between the reference planes, differential aberration, and the curvature of the sky are generally neglected in such computations. Usually the only correction applied is for the change in the north direction (position angle zero) due to precession (and sometimes also proper motion). This paper will present an algorithm for a more complete model of the geometry involved, and will show that such a model is necessary to avoid errors in the computed observables that are significant at modern astrometric accuracy. The paper will also suggest where conventions need to be established to avoid ambiguities in how quantities related to binary star

  7. Stellar and Binary Evolution in Star Clusters

    NASA Technical Reports Server (NTRS)

    McMillan, Stephen L. W.

    2001-01-01

    This paper presents a final report on research activities covered on Stellar and Binary Evolution in Star Clusters. Substantial progress was made in the development and dissemination of the "Starlab" software environment. Significant improvements were made to "kira," an N-body simulation program tailored to the study of dense stellar systems such as star clusters and galactic nuclei. Key advances include (1) the inclusion of stellar and binary evolution in a self-consistent manner, (2) proper treatment of the anisotropic Galactic tidal field, (3) numerous technical enhancements in the treatment of binary dynamics and interactions, and (4) full support for the special-purpose GRAPE-4 hardware, boosting the program's performance by a factor of 10-100 over the accelerated version. The data-reduction and analysis tools in Starlab were also substantially expanded. A Starlab Web site (http://www.sns.ias.edu/-starlab) was created and developed. The site contains detailed information on the structure and function of the various tools that comprise the package, as well as download information, "how to" tips and examples of common operations, demonstration programs, animations, etc. All versions of the software are freely distributed to all interested users, along with detailed installation instructions.

  8. Design and Implementation of BDB, the Binary Star Database

    NASA Astrophysics Data System (ADS)

    Kaygorodov, P.; Kovaleva, D.; Malkov, O.

    2013-02-01

    The Binary star DataBase (BDB, http://bdb.inasan.ru) is created to provide liasons between binary star catalogue data of various origin. Information on different observational types of binaries is obtained from heterogeneous sources of data - astronomical catalogues and surveys. The database allows a variety of query options useful for selected stars investigation purposes, for binary observations planning, and for construction and examination of binary datasets with certain characteristics.

  9. MAGNETIC INTERACTIONS IN COALESCING NEUTRON STAR BINARIES

    SciTech Connect

    Piro, Anthony L.

    2012-08-10

    It is expected on both evolutionary and empirical grounds that many merging neutron star (NS) binaries are composed of a highly magnetized NS in orbit with a relatively low magnetic field NS. I study the magnetic interactions of these binaries using the framework of a unipolar inductor model. The electromotive force generated across the non-magnetic NS as it moves through the magnetosphere sets up a circuit connecting the two stars. The exact features of this circuit depend on the uncertain resistance in the space between the stars R{sub space}. Nevertheless, I show that there are interesting observational and/or dynamical effects irrespective of its exact value. When R{sub space} is large, electric dissipation as great as {approx}10{sup 46} erg s{sup -1} (for magnetar-strength fields) occurs in the magnetosphere, which would exhibit itself as a hard X-ray precursor in the seconds leading up to merger. With less certainty, there may also be an associated radio transient. When R{sub space} is small, electric dissipation largely occurs in the surface layers of the magnetic NS. This can reach {approx}10{sup 49} erg s{sup -1} during the final {approx}1 s before merger, similar to the energetics and timescales of short gamma-ray bursts. In addition, for dipole fields greater than Almost-Equal-To 10{sup 12} G and a small R{sub space}, magnetic torques spin up the magnetized NS. This drains angular momentum from the binary and accelerates the inspiral. A faster coalescence results in less orbits occurring before merger, which would impact matched-filtering gravitational-wave searches by ground-based laser interferometers and could create difficulties for studying alternative theories of gravity with compact inspirals.

  10. Neutron star binaries, pulsars and burst sources

    NASA Technical Reports Server (NTRS)

    Lamb, F. K.

    1981-01-01

    Unresolved issues involving neutron star binaries, pulsars, and burst sources are described. Attention is drawn to the types of observations most likely to resolve them. Many of these observations are likely to be carried out during the next decade by one or more missions that have been approved or proposed. Flux measurements with an imaging detector and broad-band spectroscopic studies in the energy range 30-150 keV are discussed. The need for soft X-ray and X-ray observations with an instrument which has arcminute angular resolution and an effective area substantially greater than of ROSAT or EXOSAT is also discussed.

  11. Synchronization of magnetic stars in binary systems

    NASA Technical Reports Server (NTRS)

    Lamb, F. K.; Aly, J.-J.; Cook, M. C.; Lamb, D. Q.

    1983-01-01

    Asynchronous rotation of magnetic stars in close binary systems drives substantial field-aligned electrical currents between the magnetic star and its companion. The resulting magnetohydrodynamic torque is able to account for the heretofore unexplained synchronous rotation of the strongly magnetic degenerate dwarf component in systems like AM Her, VV Pup, AN UMa, and EF Eri as well as the magnetic A type component in systems like HD 98088 and 41 Tauri. The electric fields produced by even a small asynchronism are large and may accelerate some electrons to high energies, producing radio emission. The total energy dissipation rate in systems with degenerate dwarf spin periods as short as 1 minute may reach 10 to the 33rd ergs/s. Total luminosities of this order may be a characteristic feature of such systems.

  12. BINARY NEUTRON STARS IN QUASI-EQUILIBRIUM

    SciTech Connect

    Taniguchi, Keisuke; Shibata, Masaru

    2010-05-15

    Quasi-equilibrium sequences of binary neutron stars are constructed for a variety of equations of state in general relativity. Einstein's constraint equations in the Isenberg-Wilson-Mathews approximation are solved together with the relativistic equations of hydrostationary equilibrium under the assumption of irrotational flow. We focus on unequal-mass sequences as well as equal-mass sequences, and compare those results. We investigate the behavior of the binding energy and total angular momentum along a quasi-equilibrium sequence, the endpoint of sequences, and the orbital angular velocity as a function of time, changing the mass ratio, the total mass of the binary system, and the equation of state of a neutron star. It is found that the orbital angular velocity at the mass-shedding limit can be determined by an empirical formula derived from an analytic estimation. We also provide tables for 160 sequences, which will be useful as a guideline of numerical simulations for the inspiral and merger performed in the near future.

  13. CALCULATING THE HABITABLE ZONE OF BINARY STAR SYSTEMS. II. P-TYPE BINARIES

    SciTech Connect

    Haghighipour, Nader; Kaltenegger, Lisa

    2013-11-10

    We have developed a comprehensive methodology for calculating the circumbinary habitable zone (HZ) in planet-hosting P-type binary star systems. We present a general formalism for determining the contribution of each star of the binary to the total flux received at the top of the atmosphere of an Earth-like planet and use the Sun's HZ to calculate the inner and outer boundaries of the HZ around a binary star system. We apply our calculations to the Kepler's currently known circumbinary planetary systems and show the combined stellar flux that determines the boundaries of their HZs. We also show that the HZ in P-type systems is dynamic and, depending on the luminosity of the binary stars, their spectral types, and the binary eccentricity, its boundaries vary as the stars of the binary undergo their orbital motion. We present the details of our calculations and discuss the implications of the results.

  14. Quasistatic Evolution of Binary Neutron Star Systems Before Merging

    NASA Astrophysics Data System (ADS)

    Eriguchi, Y.; Usui, F.

    Binary neutron star systems evolve due to the back reaction of gravitational wave emission. Although this evolution is essentially a time dependent phenomenon, most stages of the evolution can be regarded as if the system were in a stationary state. Consequently we can follow the evolution of binary neutron star systems quasistatically by connecting quasiequilibrium states of binary neutron stars. On the equilibrium sequences of congruent binary neutron star systems there are two important states of equilibrium configurations: 1) the minimum angular momentum state where some unstable phenomenon sets in and 2) the contact state from which a single body sequence will continue. Recent numerical results of quasiequilibrium approaches for the binary neutron star evolution are briefly reviewed and some problems in general relativistic treatments are discussed.

  15. Time markers in interstellar communication. [with binary star civilizations

    NASA Technical Reports Server (NTRS)

    Pace, G. W.; Walker, J. C. G.

    1975-01-01

    The chances that two civilizations establish contact with each other by means of interstellar radio communication are exceedingly small in the absence of time markers which will tell the two civilizations when to search for one another. In the case of binary stars, suitable time markers are provided by the apastron and the periastron. Single star civilization would transmit signals to binaries at the observation of apastron and periastron and the binary star civilization would scan single stars at the proper time for the reception of these signals.

  16. Planetary system disruption by Galactic perturbations to wide binary stars.

    PubMed

    Kaib, Nathan A; Raymond, Sean N; Duncan, Martin

    2013-01-17

    Nearly half the exoplanets found within binary star systems reside in very wide binaries with average stellar separations greater than 1,000 astronomical units (one astronomical unit (AU) being the Earth-Sun distance), yet the influence of such distant binary companions on planetary evolution remains largely unstudied. Unlike their tighter counterparts, the stellar orbits of wide binaries continually change under the influence of the Milky Way's tidal field and impulses from other passing stars. Here we report numerical simulations demonstrating that the variable nature of wide binary star orbits dramatically reshapes the planetary systems they host, typically billions of years after formation. Contrary to previous understanding, wide binary companions may often strongly perturb planetary systems, triggering planetary ejections and increasing the orbital eccentricities of surviving planets. Although hitherto not recognized, orbits of giant exoplanets within wide binaries are statistically more eccentric than those around isolated stars. Both eccentricity distributions are well reproduced when we assume that isolated stars and wide binaries host similar planetary systems whose outermost giant planets are scattered beyond about 10 AU from their parent stars by early internal instabilities. Consequently, our results suggest that although wide binaries eventually remove the most distant planets from many planetary systems, most isolated giant exoplanet systems harbour additional distant, still undetected planets. PMID:23292514

  17. STAR HOPPERS: PLANET INSTABILITY AND CAPTURE IN EVOLVING BINARY SYSTEMS

    SciTech Connect

    Kratter, Kaitlin M.; Perets, Hagai B.

    2012-07-01

    Many planets are observed in stellar binary systems, and their frequency may be comparable to that of planetary systems around single stars. Binary stellar evolution in such systems influences the dynamical evolution of the resident planets. Here, we study the evolution of a single planet orbiting one star in an evolving binary system. We find that stellar evolution can trigger dynamical instabilities that drive planets into chaotic orbits. This instability leads to planet-star collisions, exchange of the planet between the binary stars ('star hoppers'), and ejection of the planet from the system. The means by which planets can be recaptured is similar to the pull-down capture mechanism for irregular solar system satellites. Because planets often suffer close encounters with the primary on the asymptotic giant branch, captures during a collision with the stellar envelope are also possible for more massive planets. Such capture could populate the habitable zone around white dwarfs.

  18. Einstein observations of selected close binaries and shell stars

    NASA Technical Reports Server (NTRS)

    Guinan, E. F.; Koch, R. H.; Plavec, M. J.

    1984-01-01

    Several evolved close binaries and shell stars were observed with the IPC aboard the HEAO 2 Einstein Observatory. No eclipsing target was detected, and only two of the shell binaries were detected. It is argued that there is no substantial difference in L(X) for eclipsing and non-eclipsing binaries. The close binary and shell star CX Dra was detected as a moderately strong source, and the best interpretation is that the X-ray flux arises primarily from the corona of the cool member of the binary at about the level of Algol-like or RS CVn-type sources. The residual visible-band light curve of this binary has been modeled so as to conform as well as possible with this interpretation. HD 51480 was detected as a weak source. Substantial background information from IUE and ground scanner measurements are given for this binary. The positions and flux values of several accidentally detected sources are given.

  19. A New Eclipsing Binary Discovered in a Crowded Star Field

    NASA Astrophysics Data System (ADS)

    Larson, Jessica A.; Ranquist, E.; Hernandez, A.; Stoker, E.; Gaillard, C.

    2013-06-01

    Using the 0.9 meter telescope on West Mountain to follow-up possible transiting planets with ground based photometry, we discovered a previously unknown eclipsing binary system. This eclipsing binary is located in a crowded star field and so could not be reduced using photometry. In order to figure out which object in our field of view is the eclipsing binary, we learned how to use DAO phot. By using DAO phot we hope to be able to learn more about the individual stars that make up the binary system and their parameters.

  20. NIP of Stars: early results and new eclipsing binaries

    NASA Astrophysics Data System (ADS)

    Jaque Arancibia, M.; Barba, R.; Morrell, N.; Roman Lopes, A.; Torres Robledo, S.; Gunthardt, G.; Soto, M.; Ferrero, G.; Arias, J. I.; Gamen, R.; Fernadez Lajus, E.

    2014-10-01

    We have performed a near-infrared photometric monitoring of 39 galactic young star clusters and star-forming regions, known as NIP of Stars, between the years 2009-2011, using the Swope telescope at Las Campanas Observatory (Chile) and the RetroCam camera, in H- and Y-bands. This monitoring program is complementary to the Vista Variables in the Via Láctea (VVV), as the brightest sources observed in NIP of Stars are saturated in VVV. The aim of this campaign is to perform a census of photometric variability of such clusters and star-forming regions, with the main goal of discovering massive eclipsing binary stars. In this work, we present a preliminary analysis of this photometric monitoring program with the discovery of tens of candidates for variable stars, among them candidates for massive eclipsing binaries. We included also to the analysis of variability, a small set of images obtained in the Ks with the VISTA telescope in the framework of VVV survey (Minniti et al. 2010). In special, we announce the infrared discovering of four massive eclipsing binaries in the massive young cluster NGC 3603. The stars have been classified spectroscopically as O-type stars, and one of them, MTT 58, has a rare star with a spectral type of O2 If*/WN6, as one of its components. We present a preliminary analysis of the light-curves of these binaries.

  1. Identification and Spectral Classification of Close Red Dwarf Binary Stars

    NASA Astrophysics Data System (ADS)

    Chivers, James

    2015-01-01

    The position angle, angular and linear separation, distance, and spectral class of 713 red dwarf binary star systems are reported based on data-mining the Sloan Digital Sky Survey Data Release 10. 707 of these systems are new discoveries.

  2. BINARY STAR SYNTHETIC PHOTOMETRY AND DISTANCE DETERMINATION USING BINSYN

    SciTech Connect

    Linnell, Albert P.; DeStefano, Paul; Hubeny, Ivan E-mail: pdestefa@uw.edu

    2013-09-15

    This paper extends synthetic photometry to components of binary star systems. The paper demonstrates accurate recovery of single star photometric properties for four photometric standards, Vega, Sirius, GD153, and HD209458, ranging over the HR diagram, when their model synthetic spectra are placed in fictitious binary systems and subjected to synthetic photometry processing. Techniques for photometric distance determination have been validated for all four photometric standards.

  3. Phenomenological modelling of eclipsing binary stars

    NASA Astrophysics Data System (ADS)

    Andronov, I. L.; Tkachenko, M. G.; Chinarova, L. L.

    2016-03-01

    We review the method NAV ("New Algol Variable") first introduced in (2012Ap.....55..536A) which uses the locally-dependent shapes of eclipses in an addition to the trigonometric polynomial of the second order (which typically describes the "out-of-eclipse" part of the light curve with effects of reflection, ellipticity and O'Connell). Eclipsing binary stars are believed to show distinct eclipses only if belonging to the EA (Algol) type. With a decreasing eclipse width, the statistically optimal value of the trigonometric polynomial s(2003ASPC..292..391A) drastically increases from ~2 for elliptic (EL) variables without eclipses, ~6-8 for EW and up to ~30-50 for some EA with narrow eclipses. In this case of large number of parameters, the smoothing curve becomes very noisy and apparent waves (the Gibbs phenomenon) may be seen. The NAV set of the parameters may be used for classification in the GCVS, VSX and similar catalogs. The maximal number of parameters is m=12, which corresponds to s=5, if correcting both the period and the initial epoch. We have applied the method to few stars, also in a case of multi-color photometry (2015JASS...32..127A), when it is possible to use the phenomenological parameters from the NAV fit to estimate physical parameters using statistical dependencies. For the one-color observations, one may estimate the ratio of the surface brightnesses of the components. We compiled a catalog of phenomenological characteristics based on published observations. We conclude that the NAV approximation is better than the TP one even for the case of EW-type stars with much wider eclipses. It may also be used to determine timings (see 2005ASPC..335...37A for a review of methods) or to determine parameters in the case of variable period, using a complete light curve modeling the phase variations. The method is illustrated on 2MASS J11080447-6143290 (EA-type), USNO-B1.0 1265-0306001 and USNO-B1.01266-0313413 (EW-type) and compared to various other methods

  4. THE CLOSE BINARY FRACTION OF DWARF M STARS

    SciTech Connect

    Clark, Benjamin M.; Blake, Cullen H.; Knapp, Gillian R.

    2012-01-10

    We describe a search for close spectroscopic dwarf M star binaries using data from the Sloan Digital Sky Survey to address the question of the rate of occurrence of multiplicity in M dwarfs. We use a template-fitting technique to measure radial velocities from 145,888 individual spectra obtained for a magnitude-limited sample of 39,543 M dwarfs. Typically, the three or four spectra observed for each star are separated in time by less than four hours, but for {approx}17% of the stars, the individual observations span more than two days. In these cases we are sensitive to large-amplitude radial velocity variations on timescales comparable to the separation between the observations. We use a control sample of objects having observations taken within a four-hour period to make an empirical estimate of the underlying radial velocity error distribution and simulate our detection efficiency for a wide range of binary star systems. We find the frequency of binaries among the dwarf M stars with a < 0.4 AU to be 3%-4%. Comparison with other samples of binary stars demonstrates that the close binary fraction, like the total binary fraction, is an increasing function of primary mass.

  5. Binary nature of the HADS stars AN Lyn & BE Lyn

    NASA Astrophysics Data System (ADS)

    Peña, J. H.; Rentería, A.; Villarreal, C.; Pani, A.; Huepa, H.; Huepa, J. L.; Bernal, A.; Arenas, A.; García, C.; León, R.; Ramírez, E.; Trejo, O.; Colorado, E.; Sánchez-Cruces, M.; Rechy-García, J. S.

    2015-04-01

    From newly determined times of maxima from CCD photometry of the HADS stars AN Lyn & BE Lyn and a compilation of previous times of maxima, we are able to determine the binary nature of these stars. We determine their physical parameters by means of uvby-β photometry.

  6. The close-binary content of massive star clusters

    NASA Astrophysics Data System (ADS)

    van den Berg, Maureen C.

    2015-08-01

    The fates of star clusters and the binaries in them are closely intertwined. Close binaries support a cluster against core collapse, while stellar encounters in the dense cores of massive star clusters shape the properties and numbers of the binaries. Observations of massive globular clusters with the Chandra X-ray Observatory have revealed hundreds of close binaries. I will present new results from deep HST observations of massive star clusters including 47Tuc, M28, and M4, that are aimed at classifying the X-ray source populations. Besides exotic systems such as low-mass X-ray binaries and millisecond pulsars, more mundane systems such as magnetically active binaries and accreting white dwarfs have been found. I will discuss how a breakdown of sources by class has revealed how the various binary populations bear the imprints of stellar encounters: some are dominated by dynamical creation, others by dynamical destruction. I will also discuss the effects on the integrated X-ray emissivity of massive star clusters, which is suppressed compared to lower-density environments.

  7. MASS TRANSFER IN BINARY STARS USING SMOOTHED PARTICLE HYDRODYNAMICS. II. ECCENTRIC BINARIES

    SciTech Connect

    Lajoie, Charles-Philippe; Sills, Alison E-mail: asills@mcmaster.ca

    2011-01-10

    Despite numerous efforts to better understand binary star evolution, some aspects of it remain poorly constrained. In particular, the evolution of eccentric binaries has remained elusive mainly because the Roche lobe formalism derived for circular binaries does not apply. Here we report the results of our smoothed particle hydrodynamic simulations of mass transfer in eccentric binaries using an alternate method in which we model only the outermost layers of the stars with appropriate boundary conditions. Using this technique, along with properly relaxed model stars, we characterize the mass transfer episodes of binaries with various orbital parameters. In particular, we show that these episodes can be described by Gaussians with an FWHM of {approx}0.12P{sub orb} and that the peak rates occur after periastron, at an orbital phase of {approx}0.58, independently of the eccentricity and mass of the stars. The accreted material is observed to form a rather sparse envelope around either or both stars. Although the fate of this envelope is not modeled in our simulations, we show that a constant fraction ({approx}5%) of the material transferred is ejected from the systems. We discuss this result in terms of the non-conservative mass transfer scenario. We suggest that our results could be incorporated in analytical and binary population synthesis studies to help better understand the evolution of eccentric binaries and the formation of exotic stellar populations.

  8. Modelling of binary stars from observations. (Italian Title: Creare modelli di stelle binarie dalle osservazioni)

    NASA Astrophysics Data System (ADS)

    Marino, G.

    2011-08-01

    A review on basic physical parameters of closed binary stars introduces to modelling observational data. PHOEBE and other modelling software are described. As example of application, for the first time photometric elements of the eclipsing binary V400 Lyr are obtained.

  9. Milankovitch Cycles of Terrestrial Planets in Binary Star Systems

    NASA Astrophysics Data System (ADS)

    Forgan, Duncan

    2016-08-01

    The habitability of planets in binary star systems depends not only on the radiation environment created by the two stars, but also on the perturbations to planetary orbits and rotation produced by the gravitational field of the binary and neighbouring planets. Habitable planets in binaries may therefore experience significant perturbations in orbit and spin. The direct effects of orbital resonances and secular evolution on the climate of binary planets remain largely unconsidered. We present latitudinal energy balance modelling of exoplanet climates with direct coupling to an N Body integrator and an obliquity evolution model. This allows us to simultaneously investigate the thermal and dynamical evolution of planets orbiting binary stars, and discover gravito-climatic oscillations on dynamical and secular timescales. We investigate the Kepler-47 and Alpha Centauri systems as archetypes of P and S type binary systems respectively. In the first case, Earthlike planets would experience rapid Milankovitch cycles (of order 1000 years) in eccentricity, obliquity and precession, inducing temperature oscillations of similar periods (modulated by other planets in the system). These secular temperature variations have amplitudes similar to those induced on the much shorter timescale of the binary period. In the Alpha Centauri system, the influence of the secondary produces eccentricity variations on 15,000 year timescales. This produces climate oscillations of similar strength to the variation on the orbital timescale of the binary. Phase drifts between eccentricity and obliquity oscillations creates further cycles that are of order 100,000 years in duration, which are further modulated by neighbouring planets.

  10. Binary stars can provide the `missing photons' needed for reionization

    NASA Astrophysics Data System (ADS)

    Ma, Xiangcheng; Hopkins, Philip F.; Kasen, Daniel; Quataert, Eliot; Faucher-Giguère, Claude-André; Kereš, Dušan; Murray, Norman; Strom, Allison

    2016-07-01

    Empirical constraints on reionization require galactic ionizing photon escape fractions fesc ≳ 20 per cent, but recent high-resolution radiation-hydrodynamic calculations have consistently found much lower values ˜1-5 per cent. While these models include strong stellar feedback and additional processes such as runaway stars, they almost exclusively consider stellar evolution models based on single (isolated) stars, despite the fact that most massive stars are in binaries. We re-visit these calculations, combining radiative transfer and high-resolution cosmological simulations with detailed models for stellar feedback from the Feedback in Realistic Environments project. For the first time, we use a stellar evolution model that includes a physically and observationally motivated treatment of binaries (the Binary Population and Spectral Synthesis model). Binary mass transfer and mergers enhance the population of massive stars at late times (≳3 Myr) after star formation, which in turn strongly enhances the late-time ionizing photon production (especially at low metallicities). These photons are produced after feedback from massive stars has carved escape channels in the interstellar medium, and so efficiently leak out of galaxies. As a result, the time-averaged `effective' escape fraction (ratio of escaped ionizing photons to observed 1500 Å photons) increases by factors ˜4-10, sufficient to explain reionization. While important uncertainties remain, we conclude that binary evolution may be critical for understanding the ionization of the Universe.

  11. Evolution of binary stars in multiple-population globular clusters - II. Compact binaries

    NASA Astrophysics Data System (ADS)

    Hong, Jongsuk; Vesperini, Enrico; Sollima, Antonio; McMillan, Stephen L. W.; D'Antona, Franca; D'Ercole, Annibale

    2016-04-01

    We present the results of a survey of N-body simulations aimed at exploring the evolution of compact binaries in multiple-population globular clusters. We show that as a consequence of the initial differences in the structural properties of the first-generation (FG) and the second-generation (SG) populations and the effects of dynamical processes on binary stars, the SG binary fraction decreases more rapidly than that of the FG population. The difference between the FG and SG binary fraction is qualitatively similar to but quantitatively smaller than that found for wider binaries in our previous investigations. The evolution of the radial variation of the binary fraction is driven by the interplay between binary segregation, ionization and ejection. Ionization and ejection counteract in part the effects of mass segregation but for compact binaries the effects of segregation dominate and the inner binary fraction increases during the cluster evolution. We explore the variation of the difference between the FG and the SG binary fraction with the distance from the cluster centre and its dependence on the binary binding energy and cluster structural parameters. The difference between the binary fraction in the FG and the SG populations found in our simulations is consistent with the results of observational studies finding a smaller binary fraction in the SG population.

  12. Eccentricity boost of stars around shrinking massive black hole binaries

    NASA Astrophysics Data System (ADS)

    Iwasa, Mao; Seto, Naoki

    2016-06-01

    Based on a simple geometrical approach, we analyze the evolution of the Kozai-Lidov mechanism for stars around shrinking massive black hole binaries on circular orbits. We find that, due to a peculiar bifurcation pattern induced by the Newtonian potential of stellar clusters, the orbit of stars could become highly eccentric. This transition occurs abruptly for stars with small initial eccentricities. The approach presented in this paper may be useful for studying the Kozai-Lidov mechanism in various astrophysical contexts.

  13. Observations of hot stars and eclipsing binaries with FRESIP

    NASA Technical Reports Server (NTRS)

    Gies, Douglas R.

    1994-01-01

    The FRESIP project offers an unprecedented opportunity to study pulsations in hot stars (which vary on time scales of a day) over a several year period. The photometric data will determine what frequencies are present, how or if the amplitudes change with time, and whether there is a connection between pulsation and mass loss episodes. It would initiate a new field of asteroseismology studies of hot star interiors. A search should be made for selected hot stars for inclusion in the list of project targets. Many of the primary solar mass targets will be eclipsing binaries, and I present estimates of their frequency and typical light curves. The photometric data combined with follow up spectroscopy and interferometric observations will provide fundamental data on these stars. The data will provide definitive information on the mass ratio distribution of solar-mass binaries (including the incidence of brown dwarf companions) and on the incidence of planets in binary systems.

  14. Formation and Evolution of Binary Systems Containing Collapsed Stars

    NASA Technical Reports Server (NTRS)

    Rappaport, Saul; West, Donald (Technical Monitor)

    2003-01-01

    This research includes theoretical studies of the formation and evolution of five types of interacting binary systems. Our main focus has been on developing a number of comprehensive population synthesis codes to study the following types of binary systems: (i) cataclysmic variables (#3, #8, #12, #15), (ii) low- and intermediate-mass X-ray binaries (#13, #20, #21), (iii) high-mass X-ray binaries (#14, #17, #22), (iv) recycled binary millisecond pulsars in globular clusters (#5, #10, #ll), and (v) planetary nebulae which form in interacting binaries (#6, #9). The numbers in parentheses refer to papers published or in preparation that are listed in this paper. These codes take a new unified approach to population synthesis studies. The first step involves a Monte Carlo selection of the primordial binaries, including the constituent masses, and orbital separations and eccentricities. Next, a variety of analytic methods are used to evolve the primary star to the point where either a dynamical episode of mass transfer to the secondary occurs (the common envelope phase), or the system evolves down an alternate path. If the residual core of the primary is greater than 2.5 solar mass, it will evolve to Fe core collapse and the production of a neutron star and a supernova explosion. In the case of systems involving neutron stars, a kick velocity is chosen randomly from an appropriate distribution and added to the orbital dynamics which determine the state of the binary system after the supernova explosion. In the third step, all binaries which commence stable mass transfer from the donor star (the original secondary in the binary system) to the compact object, are followed with a detailed binary evolution code. Finally, we include all the relevant dynamics of the binary system. For example, in the case of LMXBs, the binary system, with its recoil velocity from the supernova explosion, is followed in time through its path in the Galactic potential. For our globular cluster

  15. Misaligned protoplanetary disks in a young binary star system.

    PubMed

    Jensen, Eric L N; Akeson, Rachel

    2014-07-31

    Many extrasolar planets follow orbits that differ from the nearly coplanar and circular orbits found in our Solar System; their orbits may be eccentric or inclined with respect to the host star's equator, and the population of giant planets orbiting close to their host stars suggests appreciable orbital migration. There is at present no consensus on what produces such orbits. Theoretical explanations often invoke interactions with a binary companion star in an orbit that is inclined relative to the planet's orbital plane. Such mechanisms require significant mutual inclinations between the planetary and binary star orbital planes. The protoplanetary disks in a few young binaries are misaligned, but often the measurements of these misalignments are sensitive only to a small portion of the inner disk, and the three-dimensional misalignment of the bulk of the planet-forming disk mass has hitherto not been determined. Here we report that the protoplanetary disks in the young binary system HK Tauri are misaligned by 60 to 68 degrees, such that one or both of the disks are significantly inclined to the binary orbital plane. Our results demonstrate that the necessary conditions exist for misalignment-driven mechanisms to modify planetary orbits, and that these conditions are present at the time of planet formation, apparently because of the binary formation process. PMID:25079553

  16. CALCULATING THE HABITABLE ZONE OF BINARY STAR SYSTEMS. I. S-TYPE BINARIES

    SciTech Connect

    Kaltenegger, Lisa; Haghighipour, Nader

    2013-11-10

    We have developed a comprehensive methodology for calculating the boundaries of the habitable zone (HZ) of planet-hosting S-type binary star systems. Our approach is general and takes into account the contribution of both stars to the location and extent of the binary HZ with different stellar spectral types. We have studied how the binary eccentricity and stellar energy distribution affect the extent of the HZ. Results indicate that in binaries where the combination of mass-ratio and orbital eccentricity allows planet formation around a star of the system to proceed successfully, the effect of a less luminous secondary on the location of the primary's HZ is generally negligible. However, when the secondary is more luminous, it can influence the extent of the HZ. We present the details of the derivations of our methodology and discuss its application to the binary HZ around the primary and secondary main-sequence stars of an FF, MM, and FM binary, as well as two known planet-hosting binaries α Cen AB and HD 196886.

  17. General relativistic models of binary neutron stars in quasiequilibrium

    NASA Astrophysics Data System (ADS)

    Baumgarte, T. W.; Cook, G. B.; Scheel, M. A.; Shapiro, S. L.; Teukolsky, S. A.

    1998-06-01

    We perform fully relativistic calculations of binary neutron stars in corotating, circular orbit. While Newtonian gravity allows for a strict equilibrium, a relativistic binary system emits gravitational radiation, causing the system to lose energy and slowly spiral inwards. However, since inspiral occurs on a time scale much longer than the orbital period, we can treat the binary to be in quasiequilibrium. In this approximation, we integrate a subset of the Einstein equations coupled to the relativistic equation of hydrostatic equilibrium to solve the initial value problem for binaries of arbitrary separation. We adopt a polytropic equation of state to determine the structure and maximum mass of neutron stars in close binaries for polytropic indices n=1, 1.5 and 2. We construct sequences of constant rest-mass and locate turning points along energy equilibrium curves to identify the onset of orbital instability. In particular, we locate the innermost stable circular orbit and its angular velocity. We construct the first contact binary systems in full general relativity. These arise whenever the equation of state is sufficiently soft (n>~1.5). A radial stability analysis reveals no tendency for neutron stars in close binaries to collapse to black holes prior to merger.

  18. Searching for pulsations in Kepler eclipsing binary stars

    NASA Astrophysics Data System (ADS)

    Gaulme, Patrick; Guzik, Joyce A.

    2014-02-01

    Eclipsing binaries can in principle provide additional constraints to facilitate asteroseismology of one or more pulsating components. We have identified 94 possible eclipsing binary systems in a sample of over 1800 stars observed in long cadence as part of the Kepler Guest Observer Program to search for γ Doradus and δ Scuti star candidates. We show the results of a procedure to fold the light curve to identify the potential binary period, subtract a fit to the binary light curve, and perform a Fourier analysis on the residuals to search for pulsation frequencies that may arise in one or both of the stellar components. From this sample, we have found a large variety of light curve types; about a dozen stars show frequencies consistent with δ Sct or γ Dor pulsations, or light curve features possibly produced by stellar activity (rotating spots). For several stars, the folded candidate `binary' light curve resembles more closely that of an RR Lyr, Cepheid, or high-amplitude δ Sct star. We show highlights of our results and discuss the potential for asteroseismology of the most interesting objects.

  19. Photometric binary stars in Praesepe and the search for globular cluster binaries

    NASA Technical Reports Server (NTRS)

    Bolte, Michael

    1991-01-01

    A radial velocity study of the stars which are located on a second sequence above the single-star zero-age main sequence at a given color in the color-magnitude diagram of the open cluster Praesepe, (NGC 2632) shows that 10, and possibly 11, of 17 are binary systems. Of the binary systems, five have full amplitudes for their velocity variations that are greater than 50 km/s. To the extent that they can be applied to globular clusters, these results suggests that (1) observations of 'second-sequence' stars in globular clusters would be an efficient way of finding main-sequence binary systems in globulars, and (2) current instrumentation on large telescopes is sufficient for establishing unambiguously the existence of main-sequence binary systems in nearby globular clusters.

  20. Changes in the orbital periods of close binary stars

    NASA Technical Reports Server (NTRS)

    Marsh, T. R.; Pringle, J. E.

    1990-01-01

    A number of close binary stars show erratic changes in their orbital periods on time scales of order 5-10 yr. Recently it has been proposed that the period changes are the result of changes in the quadrupole moment of one star, caused in turn by an alteration of the internal structure of that star. Magnetic pressure, which either distorts the shape of the star or changes its tidally induced quadrupole moment, is suggested as the driving force behind the alteration. Here, the amount of energy required to distort one component of a binary and match the observed period changes is estimated. The rate at which energy is produced or lost is governed by the thermal time scale of the star, and the estimates indicate that the observed period changes would take at least 1000 yr for the tidal quadrupole mechanism, and of order 60 yr to match a period change in V471 Tau which took only 4 yr.

  1. Binary Stars Can Provide the "Missing Photons" Needed for Reionization

    NASA Astrophysics Data System (ADS)

    Ma, Xiangcheng; Hopkins, Philip F.; Kasen, Daniel; Quataert, Eliot; Faucher-Giguère, Claude-André; Kereš, Dušan; Murray, Norman; Strom, Allison

    2016-04-01

    Empirical constraints on reionization require galactic ionizing photon escape fractions fesc ≳ 20%, but recent high-resolution radiation-hydrodynamic calculations have consistently found much lower values ˜1-5%. While these models include strong stellar feedback and additional processes such as runaway stars, they almost exclusively consider stellar evolution models based on single (isolated) stars, despite the fact that most massive stars are in binaries. We re-visit these calculations, combining radiative transfer and high-resolution cosmological simulations with detailed models for stellar feedback from the Feedback in Realistic Environments (FIRE) project. For the first time, we use a stellar evolution model that includes a physically and observationally motivated treatment of binaries (the BPASS model). Binary mass transfer and mergers enhance the population of massive stars at late times (≳ 3 Myr) after star formation, which in turn strongly enhances the late-time ionizing photon production (especially at low metallicities). These photons are produced after feedback from massive stars has carved escape channels in the ISM, and so efficiently leak out of galaxies. As a result, the time-averaged "effective" escape fraction (ratio of escaped ionizing photons to observed 1500 Å photons) increases by factors ˜4-10, sufficient to explain reionization. While important uncertainties remain, we conclude that binary evolution may be critical for understanding the ionization of the Universe.

  2. KOI-3278: A Self-Lensing Binary Star System

    NASA Astrophysics Data System (ADS)

    Kruse, Ethan; Agol, Eric

    2014-04-01

    Over 40% of Sun-like stars are bound in binary or multistar systems. Stellar remnants in edge-on binary systems can gravitationally magnify their companions, as predicted 40 years ago. By using data from the Kepler spacecraft, we report the detection of such a “self-lensing” system, in which a 5-hour pulse of 0.1% amplitude occurs every orbital period. The white dwarf stellar remnant and its Sun-like companion orbit one another every 88.18 days, a long period for a white dwarf-eclipsing binary. By modeling the pulse as gravitational magnification (microlensing) along with Kepler’s laws and stellar models, we constrain the mass of the white dwarf to be ~63% of the mass of our Sun. Further study of this system, and any others discovered like it, will help to constrain the physics of white dwarfs and binary star evolution.

  3. KOI-3278: a self-lensing binary star system.

    PubMed

    Kruse, Ethan; Agol, Eric

    2014-04-18

    Over 40% of Sun-like stars are bound in binary or multistar systems. Stellar remnants in edge-on binary systems can gravitationally magnify their companions, as predicted 40 years ago. By using data from the Kepler spacecraft, we report the detection of such a "self-lensing" system, in which a 5-hour pulse of 0.1% amplitude occurs every orbital period. The white dwarf stellar remnant and its Sun-like companion orbit one another every 88.18 days, a long period for a white dwarf-eclipsing binary. By modeling the pulse as gravitational magnification (microlensing) along with Kepler's laws and stellar models, we constrain the mass of the white dwarf to be ~63% of the mass of our Sun. Further study of this system, and any others discovered like it, will help to constrain the physics of white dwarfs and binary star evolution. PMID:24744369

  4. Optical and ultraviolet spectroscopy of three F + B binary stars

    NASA Astrophysics Data System (ADS)

    Bopp, Bernard W.; Dempsey, Robert C.; Parsons, Sidney B.

    1991-05-01

    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.

  5. Magnetic field effects on gravitational waves from binary neutron stars

    NASA Astrophysics Data System (ADS)

    Anderson, Matthew; Hirschmann, Eric; Lehner, Luis; Liebling, Steven; Motl, Patrick; Neilsen, David; Palenzuela, Carlos; Tohline, Joel

    2008-04-01

    Observational evidence indicates that a fair number of neutron star binaries and neutron star-black hole binaries have a sizable magnetic field which can be responsible for powering pulsars and colimating jets. Magnetic field effects additionally can have a strong influence on the dynamics of the fluid by redistributing angular momentum through different mechanisms (magnetic winding and braking, magneto-rotational instabilities) depending on the strength of the magnetic field and the typical time scales involved in the process. These processes can affect the multipolar structure of the source and consequently the produced gravitational wave. We present results of neutron star binary mergers both with and without magnetic field and discuss the magnetic effects on the gravitational waves, fluid structure, and merger timescale.

  6. Accuracy and precision of gravitational-wave models of inspiraling neutron star-black hole binaries with spin: Comparison with matter-free numerical relativity in the low-frequency regime

    NASA Astrophysics Data System (ADS)

    Bhagwat, Swetha; Kumar, Prayush; Barkett, Kevin; Afshari, Nousha; Brown, Duncan A.; Lovelace, Geoffrey; Scheel, Mark A.; Szilagyi, Bela; LIGO Collaboration

    2016-03-01

    Detection of gravitational wave involves extracting extremely weak signal from noisy data and their detection depends crucially on the accuracy of the signal models. The most accurate models of compact binary coalescence are known to come from solving the Einstein's equation numerically without any approximations. However, this is computationally formidable. As a more practical alternative, several analytic or semi analytic approximations are developed to model these waveforms. However, the work of Nitz et al. (2013) demonstrated that there is disagreement between these models. We present a careful follow up study on accuracies of different waveform families for spinning black-hole neutron star binaries, in context of both detection and parameter estimation and find that SEOBNRv2 to be the most faithful model. Post Newtonian models can be used for detection but we find that they could lead to large parameter bias. Supported by National Science Foundation (NSF) Awards No. PHY-1404395 and No. AST-1333142.

  7. TRIPLE-STAR CANDIDATES AMONG THE KEPLER BINARIES

    SciTech Connect

    Rappaport, S.; Deck, K.; Sanchis-Ojeda, R.; Levine, A.; Borkovits, T.; Carter, J.; El Mellah, I.; Kalomeni, B. E-mail: kdeck@mit.edu E-mail: aml@space.mit.edu E-mail: jacarter@cfa.harvard.edu

    2013-05-01

    We present the results of a search through the photometric database of Kepler eclipsing binaries looking for evidence of hierarchical triple-star systems. The presence of a third star orbiting the binary can be inferred from eclipse timing variations. We apply a simple algorithm in an automated determination of the eclipse times for all 2157 binaries. The ''calculated'' eclipse times, based on a constant period model, are subtracted from those observed. The resulting O - C (observed minus calculated times) curves are then visually inspected for periodicities in order to find triple-star candidates. After eliminating false positives due to the beat frequency between the {approx}1/2 hr Kepler cadence and the binary period, 39 candidate triple systems were identified. The periodic O - C curves for these candidates were then fit for contributions from both the classical Roemer delay and so-called physical delay, in an attempt to extract a number of the system parameters of the triple. We discuss the limitations of the information that can be inferred from these O - C curves without further supplemental input, e.g., ground-based spectroscopy. Based on the limited range of orbital periods for the triple-star systems to which this search is sensitive, we can extrapolate to estimate that at least 20% of all close binaries have tertiary companions.

  8. Triple-star Candidates among the Kepler Binaries

    NASA Astrophysics Data System (ADS)

    Rappaport, S.; Deck, K.; Levine, A.; Borkovits, T.; Carter, J.; El Mellah, I.; Sanchis-Ojeda, R.; Kalomeni, B.

    2013-05-01

    We present the results of a search through the photometric database of Kepler eclipsing binaries looking for evidence of hierarchical triple-star systems. The presence of a third star orbiting the binary can be inferred from eclipse timing variations. We apply a simple algorithm in an automated determination of the eclipse times for all 2157 binaries. The "calculated" eclipse times, based on a constant period model, are subtracted from those observed. The resulting O - C (observed minus calculated times) curves are then visually inspected for periodicities in order to find triple-star candidates. After eliminating false positives due to the beat frequency between the ~1/2 hr Kepler cadence and the binary period, 39 candidate triple systems were identified. The periodic O - C curves for these candidates were then fit for contributions from both the classical Roemer delay and so-called physical delay, in an attempt to extract a number of the system parameters of the triple. We discuss the limitations of the information that can be inferred from these O - C curves without further supplemental input, e.g., ground-based spectroscopy. Based on the limited range of orbital periods for the triple-star systems to which this search is sensitive, we can extrapolate to estimate that at least 20% of all close binaries have tertiary companions.

  9. Binary Neutron Star Mergers: Prospects for Multimessenger Observations

    NASA Astrophysics Data System (ADS)

    Neilsen, David; Anderson, Matthew; Lehner, Luis; Liebling, Steven; Palenzuela, Carlos

    2016-03-01

    Binary neutron star mergers are possible progenitors for short gamma-ray bursts. We evolve a binary system of two neutron stars using the fully relativistic Einstein equations from an initial quasi-circular orbit, through and past merger. We consider different finite-temperature, nuclear equations of state, which vary from soft to quite stiff, and allow for magnetization of the system and neutrino cooling via a leakage scheme. We focus on potential observables, other than gravitational waves, produced mainly by the hot, strongly magnetized matter resulting from the merger.

  10. The CHARA Catalog of Orbital Elements of Spectroscopic Binary Stars

    NASA Astrophysics Data System (ADS)

    Taylor, Stuart F.; Harvin, James A.; McAlister, Harold A.

    2003-05-01

    Optical interferometry is entering a new age, with several ground-based long-baseline observatories now making observations of unprecedented resolution. Interferometers bring a new level of resolution to bear on spectroscopic binaries, enabling the full extraction of the physical parameters for the component stars with high accuracy. In the case of double-lined systems, a geometrically determined orbital parallax becomes available as well. The first step in preparing to observe spectroscopic binaries is to list them, which has not been done since the 1989 publication of the Eighth Catalogue of the Orbital Elements of Spectroscopic Binaries by Batten et al. We present a new catalog with roughly half again as many listings as the Eighth Catalogue. Angular separation predictions are made for each catalog entry. The numbers of spectroscopic binaries available for study as a function of several important observational parameters are explored, and in particular, the number of spectroscopic binaries as a function of expected separation is discussed.

  11. The Binary Nature of CH-Like Stars

    NASA Astrophysics Data System (ADS)

    Sperauskas, J.; Začs, L.; Schuster, W. J.; Deveikis, V.

    2016-07-01

    Yamashita has described a group of early carbon stars with enhanced lines of barium that resemble the CH stars but have low radial velocities. It is not clear whether they represent a class of stars separate from early R stars. Radial-velocity measurements and abundance analyses are applied in order to clarify the evolutionary status of CH-like stars. Radial-velocity monitoring was performed over a time interval of about 10 years. Abundance analysis was carried out using high-resolution spectra and the method of atmospheric models for three CH-like candidate stars. The radial-velocity monitoring confirmed regular variations for all of the classified CH-like stars, except for two, in support of their binary nature. The calculated orbital parameters are similar to those observed for barium stars in the disk of the Galaxy and their counterparts in the halo, that is, the CH stars. The relatively low luminosity of CH-like stars and the overabundance of s-process elements in the atmospheres are in agreement with a mass-transfer scenario from the secondary—an AGB star in the past. The kinematic data and metallicities support the idea that CH-like stars are thin/thick-disk population objects.

  12. Observations of Disks Around Pre--Main-Sequence Binary Stars

    NASA Astrophysics Data System (ADS)

    Jensen, Eric L. N.

    1996-08-01

    This work is an observational study of disks around low-mass, pre--main-sequence binary stars. Its purpose is to study the extent of binary-disk interactions and to determine whether binaries modify the structure of their associated disks. We present 800 micron continuum photometry of pre--main-sequence binary stars with projected separations ap < 150 AU in the Scorpius-Ophiuchus and Taurus-Auriga star-forming regions. Combining our observations with published 1300 micron continuum photometry, we find that binaries with 1 < ap < 50--100 AU have lower submillimeter continuum fluxes than wider binaries or single stars with a confidence level of greater than 99%, implying reduced disk masses. Thus, binary companions with separations less than 50--100 AU significantly influence the nature of associated disks. A simple model suggests that large gaps in disks with surface densities typical of wide-binary or single-star disks can reduce submillimeter fluxes to levels consistent with the observed limits. This model shows that the present submillimeter flux upper limits do not necessarily imply a large reduction in disk surface densities outside of cleared gaps. IRAS 60 micron fluxes show that most binaries have at least one circumstellar disk, with typical lower limits of Mdisk = 10-5 Modot. Thus, circumstellar disk surface densities are no more than two orders of magnitude smaller than those of typical disks around single stars. Our upper limits on submillimeter fluxes place upper limits of 0.005 Modot on circumbinary disk masses among binaries with 1 < ap < 50--100 AU; however, circumbinary disks are found around some binaries with separations less than a few AU null. We then present λ = 1.3 and 3 mm aperture synthesis imaging of the multiple T Tauri system UZ Tauri. UZ Tau is a hierarchical quadruple composed of a sub-AU spectroscopic binary, UZ Tau E, 530 AU distant from a 50 AU binary, UZ Tau W null. Both dust and gas emission from the 50 AU binary are at least a

  13. Ring Planetary Nebulae Ejected from Close Binary Stars

    NASA Astrophysics Data System (ADS)

    Bond, H. E.; Ciardullo, R.; Webbink, R.

    1996-12-01

    We report photometric observations of the central stars of three planetary nebulae (PNe) which appear to be thin circular rings. All three central stars have proven to be close binaries, from CCD observations made at the CTIO and KPNO 0.9-m telescopes. The southern-hemisphere PN Sp 1 is a nearly perfect circular ring. Its central star has a light curve which is a low-amplitude sinusoid with a period of 2.9 days, suggesting a reflection effect in a binary system seen nearly pole-on. We therefore suggested (Bond & Livio, ApJ 355, 568, 1990) that the nebula must be a true toroidal annulus, likewise seen nearly pole-on. SuWt 2 is another southern PN, which appears as a thin ellipse. If it were an Sp 1-like PN, seen almost edge-on, and also ejected from a close binary, we might hope to detect actual stellar eclipses. This has proven to be the case: the central star is an eclipsing binary with a period of 4.8 days. WeBo 1 is a northern PN recently discovered by Webbink and Bond. Morphologically the nebula is extremely similar to SuWt 2, in being an almost mathematically perfect ellipse. Recent observations at KPNO reveal that its central star is also a close binary, with a sinusoidal light curve and a period of approximately 5 days. It is thus becoming clear that some close binaries can undergo a common-envelope interaction that results in a much shorter orbital period accompanied by ejection of a thin nebular ring. Parallels with other objects, including SN 1987A, should be explored.

  14. Hydrodynamical evolution of coalescing binary neutron stars

    NASA Technical Reports Server (NTRS)

    Rasio, Frederic A.; Shapiro, Stuart L.

    1992-01-01

    The hydrodynamics of the final merging of two neutron stars and the corresponding gravitational wave emission is studied in detail. Various test calculations are presented, including the compressible Roche and Darwin problems and the head-on collision of two polytropes. A complete coalescence calculation is presented for the simplest case of two identical neutron stars, represented by Gamma = 2 polytropes, in a circular orbit, with their spins aligned and synchronized with the orbital rotation.

  15. Binary star orbits from speckle interferometry. 5: A combined speckle/spectroscopic study of the O star binary 15 Monocerotis

    NASA Technical Reports Server (NTRS)

    Gies, Douglas R.; Mason, Brian D.; Hartkopf, William I.; Mcalister, Harold A.; Frazin, Richard A.; Hahula, Michael E.; Penny, Laura R.; Thaller, Michelle L.; Fullerton, Alexander W.; Shara, Michael M.

    1993-01-01

    We report on the discovery of a speckle binary companion to the O7 V (f) star 15 Monocerotis. A study of published radial velocities in conjunction with new measurements from Kitt Peak National Observatory (KPNO) and IUE suggests that the star is also a spectroscopic binary with a period of 25 years and a large eccentricity. Thus, 15 Mon is the first O star to bridge the gap between the spectroscopic and visual separation regimes. We have used the star's membership in the cluster NGC 2264 together with the cluster distance to derive masses of 34 and 19 solar mass for the primary and secondary, respectively. Several of the He I line profiles display a broad shallow component which we associate with the secondary, and we estimate the secondary's classification to be O9.5 Vn. The new orbit leads to several important predictions that can be tested over the next few years.

  16. RADIAL VELOCITY STUDIES OF CLOSE BINARY STARS. XIV

    SciTech Connect

    Pribulla, Theodor; Rucinski, Slavek M.; DeBond, Heide; De Ridder, Archie; Karmo, Toomas; Thomson, J. R.; Croll, Bryce; Ogloza, Waldemar; Pilecki, Bogumil; Siwak, Michal E-mail: rucinski@astro.utoronto.ca E-mail: ridder@astro.utoronto.ca E-mail: croll@astro.utoronto.ca E-mail: pilecki@astrouw.edu.pl

    2009-03-15

    Radial velocity (RV) measurements and sine curve fits to the orbital RV variations are presented for 10 close binary systems: TZ Boo, VW Boo, EL Boo, VZ CVn, GK Cep, RW Com, V2610 Oph, V1387 Ori, AU Ser, and FT UMa. Our spectroscopy revealed two quadruple systems, TZ Boo and V2610 Oph, while three stars showing small photometric amplitudes, EL Boo, V1387 Ori, and FT UMa, were found to be triple systems. GK Cep is a close binary with a faint third component. While most of the studied eclipsing systems are contact binaries, VZ CVn and GK Cep are detached or semidetached double-lined binaries, and EL Boo, V1387 Ori, and FT UMa are close binaries of uncertain binary type. The large fraction of triple and quadruple systems found in this sample supports the hypothesis of formation of close binaries in multiple stellar systems; it also demonstrates that low photometric amplitude binaries are a fertile ground for further discoveries of multiple systems.

  17. Hydrodynamics of coalescing binary neutron stars: Ellipsoidal treatment

    NASA Technical Reports Server (NTRS)

    Lai, Dong; Shapiro, Stuart L.

    1995-01-01

    We employ an approximate treatment of dissipative hydrodynamics in three dimensions to study the coalescence of binary neutron stars driven by the emission of gravitational waves. The stars are modeled as compressible ellipsoids obeying a polytropic equation of state; all internal fluid velocities are assumed to be linear functions of the coordinates. The hydrodynamics equations then reduce to a set of coupled ordinary differential equations for the evolution of the principal axes of the ellipsoids, the internal velocity parameters, and the binary orbital parameters. Gravitational radiation reaction and viscous dissipation are both incorporated. We set up exact initial binary equilibrium configurations and follow the transition from the quasi-static, secular decay of the orbit at large separation to the rapid dynamical evolution of the configurations just prior to contact. A hydrodynamical instability resulting from tidal interactions significantly accelerates the coalescence at small separation, leading to appreciable radial infall velocity and tidal lag angles near contact. This behavior is reflected in the gravitational waveforms and may be observable by gravitational wave detectors under construction. In cases where the neutron stars have spins which are not aligned with the orbital angular momentum, the spin-induced quadrupole moment can lead to precession of the orbital plane and therefore modulation of the gravitational wave amplitude even at large orbital radius. However, the amplitude of the modulation is small for typical neutron star binaries with spins much smaller than the orbital angular momentum.

  18. The LIGO Scientific Collaboration search for inspiralling binary neutron stars

    NASA Astrophysics Data System (ADS)

    Brown, Duncan

    2006-04-01

    The three LIGO interferometers and the GEO600 interferometer operate as a network of detectors under the LIGO Scientific Collaboration (LSC). This network has now reached unprecedented levels of sensitivity. In this talk we will present the status and current results from the binary neutron star search in LIGO/GEO data.

  19. Electromagnetic and Gravitational Outputs from Binary-Neutron-Star Coalescence

    NASA Astrophysics Data System (ADS)

    Palenzuela, Carlos; Lehner, Luis; Ponce, Marcelo; Liebling, Steven L.; Anderson, Matthew; Neilsen, David; Motl, Patrick

    2013-08-01

    The late stage of an inspiraling neutron-star binary gives rise to strong gravitational wave emission due to its highly dynamic, strong gravity. Moreover, interactions between the stellar magnetospheres can produce considerable electromagnetic radiation. We study this scenario using fully general relativistic, resistive magnetohydrodynamic simulations. We show that these interactions extract kinetic energy from the system, dissipate heat, and power radiative Poynting flux, as well as develop current sheets. Our results indicate that this power can (i) outshine pulsars in binaries, (ii) display a distinctive angular- and time-dependent pattern, and (iii) radiate within large opening angles. These properties suggest that some binary neutron-star mergers are ideal candidates for multimessenger astronomy.

  20. Observations of binary stars by speckle interferometry. II

    NASA Astrophysics Data System (ADS)

    Morgan, B. L.; Beckmann, G. K.; Scaddan, R. J.

    1980-07-01

    This is the second paper in a series describing observations of binary stars using the technique of speckle interferometry. Observations were made using the 2.5-m Newton Telescope and the 1-m telescope of the Royal Greenwich Observatory and the 1.9-m telescope of the South African Astronomical Observatory. The classical Rayleigh diffraction limits are 0.050 arcsec for the 2.5-m telescope, 0.065 arcsec for the 1.9-m telescope and 0.125 arcsec for the 1-m telescope, at a wavelength of 500 nm. The results of 29 measurements of 26 objects are presented. The objects include long period spectroscopic binaries from the 6th Catalog of Batten, close visual binary systems from the 3rd Catalog of Finsen and Worley and variable stars. Nine of the objects have not been previously resolved by speckle interferometry. New members are detected in the systems Beta Cep, p Vel and Iota UMa.

  1. Cool and luminous transients from mass-losing binary stars

    NASA Astrophysics Data System (ADS)

    Pejcha, Ondřej; Metzger, Brian D.; Tomida, Kengo

    2016-07-01

    Motivated by the recently established link between luminous red novae (LRN) and catastrophic phases of binary star evolution, we perform smoothed particle hydrodynamic calculations of outflows from binary stars with realistic equation of state and opacities. We focus on the case of mass loss from the outer Lagrangian point (L2), where the resulting spiral stream experiences tidal torques from the binary and becomes unbound. As the individual spiral arms merge and collide near the binary, the outflow thermalizes about 5% of its kinetic energy. For reasonable binary parameters, the outflow can produce luminosities up to 106 L ⨀ with effective temperatures between 500 and 6000 K, depending on the optical depth through the outflow. This is compatible with many examples of the LRN such as V838 Mon and V1309 Sco. The luminosity and the expansion velocity are correlated, as is roughly observed in the known LRN. The outflow readily forms dust, leading to great variations of the appearance of the transient as a function of the viewing angle. Our results are relevant for a more general class of equatorial outflows with asymptotic velocity and heating rate near the binary proportional to its orbital speed.

  2. Orbital evolution of eccentric interacting binary star systems

    NASA Astrophysics Data System (ADS)

    Sepinsky, Jeremy Francis

    2009-06-01

    We provide a comprehensive description of the long-term (secular) orbital evolution of eccentric interacting binary systems. The evolution of circular interacting binary systems is a well studied phenomenon, but observations have shown the existence of a small but significant number of eccentric interacting binary systems. We begin by extending the commonly accepted Roche formalism for binary interacting to include eccentric orbits and asynchronously rotating stars. Using this, we calculate orbital trajectories for particles ejected from a Roche lobe-filling donor star at the periastron of the eccentric orbit. These particles admit of three possible trajectories: direct impact onto the secondary star, self accretion back onto the donor star, and the formation of a disk about the accretor. We provide a proscription for determining a priorithe trajectory of the particle given the initial system parameters, as well as describe the secular evolution of the system for each of the three cases described above. We find that these orbital evolution timescales are comparable to the mass transfer timescale which can be significantly longer than expected from the literature. Furthermore, while it is commonly assumed that any mass transfer interactions will act to circularize the orbit, we find that there are regimes of parameter space where mass transfer can cause an increase in eccentricity, and can do so at a timescale comparable to the circularization timescale created by tidal interactions. The formalism presented here can be incorporated into binary evolution and population synthesis models to create a self-consistent treatment of mass transfer in eccentric binaries.

  3. Active Longitudes and Flip-Flops in Binary Stars

    NASA Astrophysics Data System (ADS)

    Korhonen, Heidi; Järvinen, Silva P.

    2007-08-01

    In many active stars the spots concentrate on two permanent active longitudes which are 180 degrees apart. In some of these stars the dominant part of the spot activity changes the longitude every few years. This so-called flip-flop phenomenon was first reported in the early 1990's in the single, late type giant FK Com. Since then flip-flops have been reported also on binary stars, young solar type stars and the Sun itself. Even though this phenomenon has been detected on many different kinds of active stars, still less than ten stars are known to exhibit this effect. Therefore no statistically significant correlation between the stellar parameters and the flip-flop phenomenon can be carried out. Here we present results from investigation where we have studied the long-term photometry of several magnetically active RS CVn binaries to see whether or not they show permanent active longitudes and the flip-flop phenomenon. We find that it is very common for the active regions to occur on permanent active longitudes, and some of these stars also show clear flip-flop phenomenon.

  4. Binary stars and the UVX in early-type galaxies

    NASA Astrophysics Data System (ADS)

    Hernández-Pérez, Fabiola; Bruzual, Gustavo

    2014-11-01

    We use the Hernández-Pérez and Bruzual (HB13) stellar population synthesis models to study the role of interacting binary pairs as progenitors of extreme horizontal branch (EHB) stars. We assemble a sample of 3417 early-type galaxies observed both in the optical (SDSS-DR8) and the UV (GALEX-GR6). The galaxies in our sample can be classified according to their position in the colour-colour diagram as UV-weak or red-sequence galaxies (˜48 per cent), UV-strong or UVX galaxies (˜9 per cent), and recent star-forming galaxies (˜43 per cent). Analysing this sample using the HB13 models for various choices of basic model parameters, we conclude that (a) the UVr colours of UV-weak and UV-strong galaxies are reproduced by the models as long as the fraction of binary stars is at least 15 per cent. (b) Higher metallicity models (Z = 0.02 and 0.03) reproduce the colours of UV-weak and UV-strong galaxies better than lower Z models. The Z = 0.03 model is slightly bluer than the Z = 0.02 model in the UV-strong region, indicating a weak relationship between UVX and Z. (c) The strength of UVX increases with age in the model population. This is at variance with the results of other models that include binary stars as progenitors of EHB stars.

  5. Δ μ binaries among stars with large proper motions

    NASA Astrophysics Data System (ADS)

    Khovritchev, M. Yu.; Kulikova, A. M.

    2015-12-01

    Based on observations performed with the Pulkovo normal astrograph in 2008-2015 and data from sky surveys (DSS, 2MASS, SDSS DR12, WISE), we have investigated the motions of 1308 stars with proper motions larger than 300 mas yr-1 down to magnitude 17. The main idea of our search for binary stars based on this material is reduced to comparing the quasi-mean (POSS2-POSS1; an epoch difference of ≈50 yr) and quasi-instantaneous (2МASS, SDSS, WISE, Pulkovo; an epoch difference of ≈10 yr) proper motions. If the difference is statistically significant compared to the proper motion errors, then the object may be considered as a Δ μ-binary candidate. One hundred and twenty one stars from among those included in the observational program satisfy this requirement. Additional confirmations of binarity for a number of stars have been obtained by comparing the calculated proper motions with the data from several programs of stellar trigonometric parallax determinations and by analyzing the asymmetry of stellar images on sky-survey CCD frames. Analysis of the highly accurate SDSS photometric data for four stars (J0656+3827, J0838+3940, J1229+5332, J2330+4639) allows us to reach a conclusion about the probability that these Δ μ binaries are white dwarf +Mdwarf pairs.

  6. Merger of binary neutron stars in numerical relativity

    NASA Astrophysics Data System (ADS)

    Shibata, Masaru

    2014-09-01

    The merger of binary neutron stars is one of most promising sources of gravitational waves. It is also a promising candidate for the central engine of short-hard gamma-ray bursts and a source of the strong transient electromagnetic signal that could be the counterpart of gravitational-wave signals. Numerical relativity is probably the unique tool for theoretically exploring the merger process, and now, it is powerful enough to provide us a wide variety of aspects of the binary-neutron-star merger. In this talk, I will summarize our current understanding of the entire merger event that is obtained by a large-scale numerical-relativity simulations. In particular, I focus on the relation between the neutron-star equation of state and gravitational waves emitted during the late inspiral and merger phase, and observable electromagnetic signal that is likely to be emitted by the dynamical ejecta through r-process nucleosynthesis.

  7. Photometric study of the active binary star V1430 Aquilae

    NASA Astrophysics Data System (ADS)

    Erdem, A.; Sürgit, D.

    2006-05-01

    New BVR light curves and a photometric analysis of the eclipsing binary star V1430 Aql are presented. The light curves were obtained at the Çanakkale Onsekiz Mart University Observatory in 2004. The light curves are generally those of detached eclipsing binaries, but there are large asymmetries between maxima. New BVR light curves were analysed with an ILOT procedure. Light curve asymmetries of the system were explained in terms of large dark starspots on the primary component. The primary star shows a long-lived and quasi-poloidal spot distribution with active longitudes in opposite hemispheres. Absolute parameters of the system were derived. We also discuss the evolution of the system: the components are likely to be pre-main sequence stars, but a post-main sequence stage cannot be ruled out. More observations are needed to decide this point.

  8. Magnetised winds in single and binary star systems

    NASA Astrophysics Data System (ADS)

    Johnstone, Colin

    2016-07-01

    Stellar winds are fundamentally important for the stellar magnetic activity evolution and for the immediate environment surrounding their host stars. Ionised winds travel at hundreds of km/s, impacting planets and clearing out large regions around the stars called astropheres. Winds influence planets in many ways: for example, by compressing the magnetosphere and picking up atmospheric particles, they can cause significant erosion of a planetary atmosphere. By removing angular momentum, winds cause the rotation rates of stars to decrease as they age. This causes the star's magnetic dynamo to decay, leading to a significant decay in the star's levels of X-ray and extreme ultraviolet emission. Despite their importance, little is currently known about the winds of other Sun-like stars. Their small mass fluxes have meant that no direct detections have so far been possible. What is currently known has either been learned indirectly or through analogies with the solar wind. In this talk, I will review what is known about the properties and evolution of the winds of other Sun-like stars. I will also review wind dynamics in binary star systems, where the winds from both stars impact each other, leading to shocks and compression regions.

  9. ADIABATIC MASS LOSS IN BINARY STARS. I. COMPUTATIONAL METHOD

    SciTech Connect

    Ge Hongwei; Chen Xuefei; Han Zhanwen; Webbink, Ronald F. E-mail: mshjell@gmail.co

    2010-07-10

    The asymptotic response of donor stars in interacting binary systems to very rapid mass loss is characterized by adiabatic expansion throughout their interiors. In this limit, energy generation and heat flow through the stellar interior can be neglected. We model this response by constructing model sequences, beginning with a donor star filling its Roche lobe at an arbitrary point in its evolution, holding its specific entropy and composition profiles fixed as mass is removed from the surface. The stellar interior remains in hydrostatic equilibrium. Luminosity profiles in these adiabatic models of mass-losing stars can be reconstructed from the specific entropy profiles and their gradients. These approximations are validated by comparison with time-dependent binary mass transfer calculations. We describe how adiabatic mass-loss sequences can be used to quantify threshold conditions for dynamical timescale mass transfer, and to establish the range of post-common envelope binaries that are allowed energetically. In dynamical timescale mass transfer, the adiabatic response of the donor star drives it to expand beyond its Roche lobe, leading to runaway mass transfer and the formation of a common envelope with its companion star. For donor stars with surface convection zones of any significant depth, this runaway condition is encountered early in mass transfer, if at all; but for main-sequence stars with radiative envelopes, it may be encountered after a prolonged phase of thermal timescale mass transfer, a so-called delayed dynamical instability. We identify the critical binary mass ratio for the onset of dynamical timescale mass transfer as that ratio for which the adiabatic response of the donor star radius to mass loss matches that of its Roche lobe at some point during mass transfer; if the ratio of donor to accretor masses exceeds this critical value, dynamical timescale mass transfer ensues. In common envelope evolution, the dissipation of orbital energy of the

  10. Synergies in Astrometry: Predicting Navigational Error of Visual Binary Stars

    NASA Astrophysics Data System (ADS)

    Gessner Stewart, Susan

    2015-08-01

    Celestial navigation can employ a number of bright stars which are in binary systems. Often these are unresolved, appearing as a single, center-of-light object. A number of these systems are, however, in wide systems which could introduce a margin of error in the navigation solution if not handled properly. To illustrate the importance of good orbital solutions for binary systems - as well as good astrometry in general - the relationship between the center-of-light versus individual catalog position of celestial bodies and the error in terrestrial position derived via celestial navigation is demonstrated. From the list of navigational binary stars, fourteen such binary systems with at least 3.0 arcseconds apparent separation are explored. Maximum navigational error is estimated under the assumption that the bright star in the pair is observed at maximum separation, but the center-of-light is employed in the navigational solution. The relationships between navigational error and separation, orbital periods, and observers' latitude are discussed.

  11. Ba STARS AND OTHER BINARIES IN FIRST AND SECOND GENERATION STARS IN GLOBULAR CLUSTERS

    SciTech Connect

    D'Orazi, Valentina; Gratton, Raffaele; Lucatello, Sara; Carretta, Eugenio; Bragaglia, Angela; Marino, Anna F.

    2010-08-20

    The determination of the Ba abundance in globular cluster (GC) stars is a very powerful test to address several issues in the framework of multiple population scenarios. We measured the Ba content for a sample of more than 1200 stars in 15 Galactic GCs, using high-resolution FLAMES/Giraffe spectra. We found no variation in [Ba/Fe] ratios for different stellar populations within each cluster; this means that low-mass asymptotic giant branch stars do not significantly contribute to the intracluster pollution. Very interestingly, we found that the fraction of Ba stars in first generation (FG) stars is close to the values derived for field stars ({approx}2%); on the other hand, second generation (SG) stars present a significantly lower fraction. An independent and successful test, based on radial velocity variations among giant stars in NGC 6121, confirms our finding: the binary fraction among FG stars is about {approx}12%, to be compared with {approx}1% of SG stars. This is an evidence that SG stars formed in a denser environment, where infant mortality of binary systems was particularly efficient.

  12. Electromagnetic field dynamics in Binary Neutron Stars

    NASA Astrophysics Data System (ADS)

    Palenzuela, Carlos; Anderson, Matthew; Hirschmann, Eric; Lehner, Luis; Liebling, Steven; Neilsen, David; Motl, Patrick

    2011-04-01

    Neutron star mergers represent one of the most promising sources of gravitational waves (GW) within the bandwidth of advLIGO. In addition to GW, strong magnetic fields may offer the possibility of a characteristic electromagnetic signature allowing for concurrent detection. In this talk we present results from numerical evolutions of such mergers, studying the dynamics of both the gravitational and electromagnetic degrees of freedom.

  13. The MACHO Project LMC variable star inventory. V. Classification and orbits of 611 eclipsing binary stars

    SciTech Connect

    The MACHO Collaboration

    1997-07-01

    We report the characteristics of 611 eclipsing binary stars in the Large Megallanic Cloud found by using the MACHO Project photometry database. The sample is magnitude limited, and extends down the main sequence to about spectral type A0. Many evolved binaries are also included. Each eclipsing binary is classified according to the traditional scheme of the {ital General Catalogue of Variable Stars} (EA and EB), and also according to a new decimal classification scheme defined in this paper. The new scheme is sensitive to the two major sources of variance in eclipsing binary star light curves{emdash}the sum of radii, and the surface-brightness ratio, and allow greater precision in characterizing the light curves. Examples of each type of light curve and their variations are given. Sixty-four of the eclipsing binaries have eccentric, rather than circular, orbits. The ephemeris and principal photometric characteristics of each eclipsing binary are listed in a table. Photometric orbits based on the Nelson{endash}Davis{endash}Etzel model have been fitted to all light curves. These data will be useful for planning future observations of these binaries. Plots of all data and fitted orbits and a table of the fitted orbital parameters are available on the AAS CD-ROM series, Vol. 9, 1997. These data are also available at the MACHO home page (http://wwwmacho.mcmaster.ca/). {copyright} {ital 1997 American Astronomical Society.}

  14. Resolving subdwarf B stars in binaries by HST imaging

    NASA Astrophysics Data System (ADS)

    Heber, U.; Moehler, S.; Napiwotzki, R.; Thejll, P.; Green, E. M.

    2002-03-01

    The origin of subluminous B stars is still an unsolved problem in stellar evolution. Single star as well as close binary evolution scenarios have been invoked but until now have met with little success. We have carried out a small survey of spectroscopic binary candidates (19 systems consisting of an sdB star and late type companion) with the Planetary Camera of the WFPC2 onboard Hubble Space Telescope to test these scenarios. Monte Carlo simulations indicate that by imaging the programme stars in the R-band about one third of the sample (6-7 stars) should be resolved at a limiting angular resolution of 0.1 arcsec if they have linear separations like main sequence stars (``single star evolution''). None should be resolvable if all systems were produced by close binary evolution. In addition we expect three triple systems to be present in our sample. Most of these, if not all, should be resolvable. Components were resolved in 6 systems with separations between 0.2 arcsec and 4.5 arcsec. However, only in the two systems TON 139 and PG 1718+519 (separations 0.32 arcsec and 0.24 arcsec, respectively) do the magnitudes of the resolved components match the expectations from the deconvolution of the spectral energy distribution. These two stars could be physical binaries whereas in the other cases the nearby star may be a chance projection or a third component. Radial velocity measurements indicate that the resolved system TON 139 is a triple system, with the sdB having a close companion that does not contribute detectably to the integrated light of the system. Radial velocity information for the second resolved system, PG 1718+519, is insufficient. Assuming that it is not a triple system, it would be the only resolved system in our sample. Accordingly the success rate would be only 5% which is clearly below the prediction for single star evolution. We conclude that the distribution of separations of sdB binaries deviates strongly from that of normal stars. Our results

  15. Unification of Binary Star Ephemeris Solutions

    NASA Astrophysics Data System (ADS)

    Wilson, R. E.; Van Hamme, W.

    2014-01-01

    Time-related binary system characteristics such as orbital period, its rate of change, apsidal motion, and variable light-time delay due to a third body, are measured in two ways that can be mutually complementary. The older way is via eclipse timings, while ephemerides by simultaneous whole light and velocity curve analysis have appeared recently. Each has its advantages, for example, eclipse timings typically cover relatively long time spans while whole curves often have densely packed data within specific intervals and allow access to systemic properties that carry additional timing information. Synthesis of the two information sources can be realized in a one step process that combines several data types, with automated weighting based on their standard deviations. Simultaneous light-velocity-timing solutions treat parameters of apsidal motion and the light-time effect coherently with those of period and period change, allow the phenomena to interact iteratively, and produce parameter standard errors based on the quantity and precision of the curves and timings. The logic and mathematics of the unification algorithm are given, including computation of theoretical conjunction times as needed for generation of eclipse timing residuals. Automated determination of eclipse type, recovery from inaccurate starting ephemerides, and automated data weighting are also covered. Computational examples are given for three timing-related cases—steady period change (XY Bootis), apsidal motion (V526 Sagittarii), and the light-time effect due to a binary's reflex motion in a triple system (AR Aurigae). Solutions for all combinations of radial velocity, light curve, and eclipse timing input show consistent results, with a few minor exceptions.

  16. Unification of binary star ephemeris solutions

    SciTech Connect

    Wilson, R. E.; Van Hamme, W. E-mail: vanhamme@fiu.edu

    2014-01-10

    Time-related binary system characteristics such as orbital period, its rate of change, apsidal motion, and variable light-time delay due to a third body, are measured in two ways that can be mutually complementary. The older way is via eclipse timings, while ephemerides by simultaneous whole light and velocity curve analysis have appeared recently. Each has its advantages, for example, eclipse timings typically cover relatively long time spans while whole curves often have densely packed data within specific intervals and allow access to systemic properties that carry additional timing information. Synthesis of the two information sources can be realized in a one step process that combines several data types, with automated weighting based on their standard deviations. Simultaneous light-velocity-timing solutions treat parameters of apsidal motion and the light-time effect coherently with those of period and period change, allow the phenomena to interact iteratively, and produce parameter standard errors based on the quantity and precision of the curves and timings. The logic and mathematics of the unification algorithm are given, including computation of theoretical conjunction times as needed for generation of eclipse timing residuals. Automated determination of eclipse type, recovery from inaccurate starting ephemerides, and automated data weighting are also covered. Computational examples are given for three timing-related cases—steady period change (XY Bootis), apsidal motion (V526 Sagittarii), and the light-time effect due to a binary's reflex motion in a triple system (AR Aurigae). Solutions for all combinations of radial velocity, light curve, and eclipse timing input show consistent results, with a few minor exceptions.

  17. Gravitational and Electromagnetic Emission from Binary Neutron Star Mergers

    NASA Astrophysics Data System (ADS)

    Motl, Patrick M.; Palenzuela, C.; Lehner, L.; Ponce, M.; Liebling, S. L.; Anderson, M.; Neilsen, D.

    2013-06-01

    The inspiral of a neutron star - neutron star binary is a leading candidate for strong emission of gravitational waves. The interaction between the stellar magnetospheres may also give rise to electromagnetic emissions accompanying the gravity waves as the neutron stars inspiral and merge. We present results from a set of resistive magnetohydrodynamic simulations of mergers computed with full general relativity. We vary the initial magnetic field of the neutron stars including cases where the fields are initially aligned, anit-aligned and where one star’s field dominates over its companion. This presentation is based upon work supported by the National Aeronautics and Space Administration under grant No. NNX13AH01G through the astrophysics theory program.

  18. A Binary Model for the Emission Line Star FX Velorum

    NASA Astrophysics Data System (ADS)

    Blake, M.; Hunter, M.

    2015-06-01

    FX Vel is a southern, young variable star which shows large variations in brightness. In examining the environments where planets may form, disks around young stars provide important clues as to how long such disks might last. We discuss several possible scenarios for the structure of FX Vel, including a binary model similar to EE Cep and the possibility that FX Vel may be a UXor variable, a class of young stars with disks. This could also explain the colors and irregular variation in brightness of the star. We suggest FX Vel may be a blue straggler member of the open cluster ASCC48 based upon its position on the cluster CMD and proper motions. More data is required examine the alternate possibility of FX Vel being a member of Teutsch 101. A spectroscopic study of FX Vel would be valuable.

  19. SPECTROSCOPIC METALLICITY DETERMINATIONS FOR W UMa-TYPE BINARY STARS

    SciTech Connect

    Rucinski, Slavek M.; Pribulla, Theodor; Budaj, Jan E-mail: pribulla@ta3.sk

    2013-09-15

    This study is the first attempt to determine the metallicities of W UMa-type binary stars using spectroscopy. We analyzed about 4500 spectra collected at the David Dunlap Observatory. To circumvent problems caused by the extreme spectral line broadening and blending and by the relatively low quality of the data, all spectra were subject to the same broadening function (BF) processing to determine the combined line strength in the spectral window centered on the Mg I triplet between 5080 A and 5285 A. All individual integrated BFs were subsequently orbital-phase averaged to derive a single line-strength indicator for each star. The star sample was limited to 90 W UMa-type (EW) binaries with the strict phase-constancy of colors and without spectral contamination by spectroscopic companions. The best defined results were obtained for an F-type sub-sample (0.32 < (B - V){sub 0} < 0.62) of 52 binaries for which integrated BF strengths could be interpolated in the model atmosphere predictions. The logarithmic relative metallicities, [M/H], for the F-type sub-sample indicate metal abundances roughly similar to the solar metallicity, but with a large scatter which is partly due to combined random and systematic errors. Because of the occurrence of a systematic color trend resulting from inherent limitations in our approach, we were forced to set the absolute scale of metallicities to correspond to that derived from the m{sub 1} index of the Stroemgren uvby photometry for 24 binaries of the F-type sub-sample. The trend-adjusted metallicities [M/H]{sub 1} are distributed within -0.65 < [M/H]{sub 1} < +0.50, with the spread reflecting genuine metallicity differences between stars. One half of the F-sub-sample binaries have [M/H]{sub 1} within -0.37 < [M/H]{sub 1} < +0.10, a median of -0.04 and a mean of -0.10, with a tail toward low metallicities, and a possible bias against very high metallicities. A parallel study of kinematic data, utilizing the most reliable and recently

  20. Spectroscopic Metallicity Determinations for W UMa-type Binary Stars

    NASA Astrophysics Data System (ADS)

    Rucinski, Slavek M.; Pribulla, Theodor; Budaj, Ján

    2013-09-01

    This study is the first attempt to determine the metallicities of W UMa-type binary stars using spectroscopy. We analyzed about 4500 spectra collected at the David Dunlap Observatory. To circumvent problems caused by the extreme spectral line broadening and blending and by the relatively low quality of the data, all spectra were subject to the same broadening function (BF) processing to determine the combined line strength in the spectral window centered on the Mg I triplet between 5080 Å and 5285 Å. All individual integrated BFs were subsequently orbital-phase averaged to derive a single line-strength indicator for each star. The star sample was limited to 90 W UMa-type (EW) binaries with the strict phase-constancy of colors and without spectral contamination by spectroscopic companions. The best defined results were obtained for an F-type sub-sample (0.32 < (B - V)0 < 0.62) of 52 binaries for which integrated BF strengths could be interpolated in the model atmosphere predictions. The logarithmic relative metallicities, [M/H], for the F-type sub-sample indicate metal abundances roughly similar to the solar metallicity, but with a large scatter which is partly due to combined random and systematic errors. Because of the occurrence of a systematic color trend resulting from inherent limitations in our approach, we were forced to set the absolute scale of metallicities to correspond to that derived from the m 1 index of the Strömgren uvby photometry for 24 binaries of the F-type sub-sample. The trend-adjusted metallicities [M/H]1 are distributed within -0.65 < [M/H]1 < +0.50, with the spread reflecting genuine metallicity differences between stars. One half of the F-sub-sample binaries have [M/H]1 within -0.37 < [M/H]1 < +0.10, a median of -0.04 and a mean of -0.10, with a tail toward low metallicities, and a possible bias against very high metallicities. A parallel study of kinematic data, utilizing the most reliable and recently obtained proper motion and radial

  1. Spectral Classification of Unresolved Binary Stars with Artificial Neural Networks

    NASA Astrophysics Data System (ADS)

    Weaver, Wm. Bruce

    2000-09-01

    An artificial neural network technique has been developed to perform two-dimensional spectral classification of the components of binary stars. The spectra are based on the 15 Å resolution near-infrared (NIR) spectral classification system described by Torres-Dodgen & Weaver. Using the spectrum with no manual intervention except wavelength registration, a single artificial neural network (ANN) can classify these spectra with Morgan-Keenan types with an average accuracy of about 2.5 types (subclasses) in temperature and about 0.45 classes in luminosity for up to 3 mag of difference in luminosity. The error in temperature classification does not increase substantially until the secondary contributes less than 10% of the light of the system. By following the coarse-classification ANN with a specialist ANN, the mean absolute errors are reduced to about 0.5 types in temperature and 0.33 classes in luminosity. The resulting ANN network was applied to seven binary stars.

  2. Cool and luminous transients from mass-losing binary stars

    NASA Astrophysics Data System (ADS)

    Pejcha, Ondřej; Metzger, Brian D.; Tomida, Kengo

    2016-02-01

    We study transients produced by equatorial disc-like outflows from catastrophically mass-losing binary stars with an asymptotic velocity and energy deposition rate near the inner edge which are proportional to the binary escape velocity vesc. As a test case, we present the first smoothed-particle radiation-hydrodynamics calculations of the mass loss from the outer Lagrange point with realistic equation of state and opacities. The resulting spiral stream becomes unbound for binary mass ratios 0.06 ≲ q ≲ 0.8. For synchronous binaries with non-degenerate components, the spiral-stream arms merge at a radius of ˜10a, where a is the binary semi-major axis, and the accompanying shock thermalizes about 10 per cent of the kinetic power of the outflow. The mass-losing binary outflows produce luminosities reaching up to ˜106 L⊙ and effective temperatures spanning 500 ≲ Teff ≲ 6000 K, which is compatible with many of the class of recently discovered red transients such as V838 Mon and V1309 Sco. Dust readily forms in the outflow, potentially in a catastrophic global cooling transition. The appearance of the transient is viewing angle-dependent due to vastly different optical depths parallel and perpendicular to the binary plane. We predict a correlation between the peak luminosity and the outflow velocity, which is roughly obeyed by the known red transients. Outflows from mass-losing binaries can produce luminous (105 L⊙) and cool (Teff ≲ 1500 K) transients lasting a year or longer, as has potentially been detected by Spitzer surveys of nearby galaxies.

  3. RADIAL VELOCITY STUDIES OF CLOSE BINARY STARS. XV

    SciTech Connect

    Pribulla, Theodor; Rucinski, Slavek M.; Blake, R. M.; Lu, Wenxian; Thomson, J. R.; DeBond, Heide; Karmo, Toomas; De Ridder, Archie; Ogloza, Waldemar; Stachowski, Greg; Siwak, Michal E-mail: rucinski@astro.utoronto.ca E-mail: karmo@astro.utoronto.ca E-mail: ogloza@ap.krakow.pl E-mail: siwak@oa.uj.edu.pl

    2009-03-15

    Radial velocity (RV) measurements and sine curve fits to the orbital RV variations are presented for the last eight close binary systems analyzed in the same way as in the previous papers of this series: QX And, DY Cet, MR Del, HI Dra, DD Mon, V868 Mon, ER Ori, and Y Sex. For another seven systems (TT Cet, AA Cet, CW Lyn, V563 Lyr, CW Sge, LV Vir, and MW Vir), phase coverage is insufficient to provide reliable orbits but RVs of individual components were measured. Observations of a few complicated systems observed throughout the David Dunlap Observatory (DDO) close binary program are also presented; among them is an especially interesting multiple system V857 Her which-in addition to the contact binary-very probably contains one or more subdwarf components of much earlier spectral type. All suspected binaries which were found to be most probably pulsating stars are briefly discussed in terms of mean RVs and projected rotation velocities (vsin i) as well as spectral-type estimates. In two of them, CU CVn and V752 Mon, the broadening functions show a clear presence of nonradial pulsations. The previously missing spectral types for Paper I are given here in addition to such estimates for most of the program stars of this paper.

  4. A catalogue of temperatures for Kepler eclipsing binary stars

    NASA Astrophysics Data System (ADS)

    Armstrong, D. J.; Gómez Maqueo Chew, Y.; Faedi, F.; Pollacco, D.

    2014-02-01

    We have combined the Kepler Eclipsing Binary Catalogue with information from the HES, KIS and 2MASS photometric surveys to produce spectral energy distribution fits to over 2600 eclipsing binaries in the catalogue over a wavelength range of 0.36-2.16 Å. We present primary (T1) and secondary (T2) stellar temperatures, plus information on the stellar radii and system distance ratios. The derived temperatures are on average accurate to 370 K in T1 and 620 K in T2. Our results improve on the similarly derived physical parameters of the Kepler Input Catalogue through consideration of both stars of the binary system rather than a single star model, and inclusion of additional U-band photometry. We expect these results to aid future uses of the Kepler eclipsing binary data, both in target selection and to inform users of the extremely high-precision light curves available. We do not include surface gravities or system metallicities, as these were found to have an insignificant effect on the observed photometric bands.

  5. Kitt Peak Speckle Interferometry of Close Visual Binary Stars (Abstract)

    NASA Astrophysics Data System (ADS)

    Gener, R.; Rowe, D.; Smith, T. C.; Teiche, A.; Harshaw, R.; Wallace, D.; Weise, E.; Wiley, E.; Boyce, G.; Boyce, P.; Branston, D.; Chaney, K.; Clark, R. K.; Estrada, C.; Estrada, R.; Frey, T.; Green, W. L.; Haurberg, N.; Jones, G.; Kenney, J.; Loftin, S.; McGieson, I.; Patel, R.; Plummer, J.; Ridgely, J.; Trueblood, M.; Westergren, D.; Wren, P.

    2014-12-01

    (Abstract only) Speckle interferometry can be used to overcome normal seeing limitations by taking many very short exposures at high magnification and analyzing the resulting speckles to obtain the position angles and separations of close binary stars. A typical speckle observation of a close binary consists of 1,000 images, each 20 milliseconds in duration. The images are stored as a multi-plane FITS cube. A portable speckle interferometry system that features an electron-multiplying CCD camera was used by the authors during two week-long observing runs on the 2.1-meter telescope at Kitt Peak National Observatory to obtain some 1,000 data cubes of close binaries selected from a dozen different research programs. Many hundreds of single reference stars were also observed and used in deconvolution to remove undesirable atmospheric and telescope optical effects. The database of well over one million images was reduced with the Speckle Interferometry Tool of platesolve3. A few sample results are provided. During the second Kitt Peak run, the McMath-Pierce 1.6- and 0.8-meter solar telescopes were evaluated for nighttime speckle interferometry, while the 0.8-meter Coude feed was used to obtain differential radial velocities of short arc binaries.

  6. VX Her: Eclipsing Binary System or Single Variable Star

    NASA Astrophysics Data System (ADS)

    Perry, Kathleen; Castelaz, Michael; Henson, Gary; Boghozian, Andrew

    2015-01-01

    VX Her is a pulsating variable star with a period of .4556504 days. It is believed to be part of an eclipsing binary system (Fitch et al. 1966). This hypothesis originated from Fitch seeing VX Her's minimum point on its light curve reaching a 0.7 magnitude fainter than normal and remaining that way for nearly two hours. If VX Her were indeed a binary system, I would expect to see similar results with a fainter minimum and a broader, more horizontal dip. Having reduced and analyzed images from the Southeastern Association for Research in Astronomy Observatory in Chile and Kitt Peak, as well as images from a 0.15m reflector at East Tennessee State University, I found that VX Her has the standard light curve of the prototype variable star, RR Lyrae. Using photometry, I found no differing features in its light curve to suggest that it is indeed a binary system. However, more observations are needed in case VX Her is a wide binary.

  7. Single versus binary star progenitors of Type IIb supernovae

    NASA Astrophysics Data System (ADS)

    Sravan, Niharika

    2016-07-01

    Stripped-envelope supernovae (SNe) represent a challenge to our understanding of massive star evolution. Wind mass loss and binary interactions are the leading candidates to explain observations. The latter has gained support in the recent years with growing evidence that mass-loss rates due to line-driven winds are, in reality, 2 - 3 times lower. Type IIb SNe retain a small amount of their Hydrogen envelope before undergoing core-collapse and are the only class of stripped-envelope SNe with identified progenitors. Thus they are powerful tools for testing our understanding of massive stellar evolution. To identify possible evolutionary pathways to Type IIb SNe, we use Modules for Experiments in Stellar Astrophysics (MESA) to model a large population of single and binary star sequences covering a broad parameter space with a wide range of component masses and initial orbital periods and identify those that undergo core-collapse with 0.01 to 0.5 solar masses of residual Hydrogen envelope. We find no single star Type IIb progenitors in the parameter space covered. We find a few Type IIb binary progenitors. These sequences have initial mass ratios greater than 0.6, wide orbital periods and undergo non-conservative mass transfer.

  8. Linking electromagnetic and gravitational radiation in coalescing binary neutron stars

    NASA Astrophysics Data System (ADS)

    Palenzuela, Carlos; Lehner, Luis; Liebling, Steven L.; Ponce, Marcelo; Anderson, Matthew; Neilsen, David; Motl, Patrick

    2013-08-01

    We expand on our study of the gravitational and electromagnetic emissions from the late stage of an inspiraling neutron star binary as presented in Palenzuela et al. [Phys. Rev. Lett. 111, 061105 (2013)]. Interactions between the stellar magnetospheres, driven by the extreme dynamics of the merger, can yield considerable outflows. We study the gravitational and electromagnetic waves produced during the inspiral and merger of a binary neutron star system using a full relativistic, resistive magnetohydrodynamics evolution code. We show that the interaction between the stellar magnetospheres extracts kinetic energy from the system and powers radiative Poynting flux and heat dissipation. These features depend strongly on the configuration of the initial stellar magnetic moments. Our results indicate that this power can strongly outshine pulsars in binaries and have a distinctive angular and time-dependent pattern. Our discussion provides more detail than Palenzuela et al., showing clear evidence of the different effects taking place during the inspiral. Our simulations include a few milliseconds after the actual merger and study the dynamics of the magnetic fields during the formation of the hypermassive neutron star. We also briefly discuss the possibility of observing such emissions.

  9. Neutron-Star-Black-Hole Binaries Produced by Binary-Driven Hypernovae.

    PubMed

    Fryer, Chris L; Oliveira, F G; Rueda, J A; Ruffini, R

    2015-12-01

    Binary-driven hypernovae (BdHNe) within the induced gravitational collapse paradigm have been introduced to explain energetic (E_{iso}≳10^{52}  erg), long gamma-ray bursts (GRBs) associated with type Ic supernovae (SNe). The progenitor is a tight binary composed of a carbon-oxygen (CO) core and a neutron-star (NS) companion, a subclass of the newly proposed "ultrastripped" binaries. The CO-NS short-period orbit causes the NS to accrete appreciable matter from the SN ejecta when the CO core collapses, ultimately causing it to collapse to a black hole (BH) and producing a GRB. These tight binaries evolve through the SN explosion very differently than compact binaries studied in population synthesis calculations. First, the hypercritical accretion onto the NS companion alters both the mass and the momentum of the binary. Second, because the explosion time scale is on par with the orbital period, the mass ejection cannot be assumed to be instantaneous. This dramatically affects the post-SN fate of the binary. Finally, the bow shock created as the accreting NS plows through the SN ejecta transfers angular momentum, braking the orbit. These systems remain bound even if a large fraction of the binary mass is lost in the explosion (well above the canonical 50% limit), and even large kicks are unlikely to unbind the system. Indeed, BdHNe produce a new family of NS-BH binaries unaccounted for in current population synthesis analyses and, although they may be rare, the fact that nearly 100% remain bound implies that they may play an important role in the compact merger rate, important for gravitational waves that, in turn, can produce a new class of ultrashort GRBs. PMID:26684106

  10. Neutron-Star-Black-Hole Binaries Produced by Binary-Driven Hypernovae

    NASA Astrophysics Data System (ADS)

    Fryer, Chris L.; Oliveira, F. G.; Rueda, J. A.; Ruffini, R.

    2015-12-01

    Binary-driven hypernovae (BdHNe) within the induced gravitational collapse paradigm have been introduced to explain energetic (Eiso≳1052 erg ), long gamma-ray bursts (GRBs) associated with type Ic supernovae (SNe). The progenitor is a tight binary composed of a carbon-oxygen (CO) core and a neutron-star (NS) companion, a subclass of the newly proposed "ultrastripped" binaries. The CO-NS short-period orbit causes the NS to accrete appreciable matter from the SN ejecta when the CO core collapses, ultimately causing it to collapse to a black hole (BH) and producing a GRB. These tight binaries evolve through the SN explosion very differently than compact binaries studied in population synthesis calculations. First, the hypercritical accretion onto the NS companion alters both the mass and the momentum of the binary. Second, because the explosion time scale is on par with the orbital period, the mass ejection cannot be assumed to be instantaneous. This dramatically affects the post-SN fate of the binary. Finally, the bow shock created as the accreting NS plows through the SN ejecta transfers angular momentum, braking the orbit. These systems remain bound even if a large fraction of the binary mass is lost in the explosion (well above the canonical 50% limit), and even large kicks are unlikely to unbind the system. Indeed, BdHNe produce a new family of NS-BH binaries unaccounted for in current population synthesis analyses and, although they may be rare, the fact that nearly 100% remain bound implies that they may play an important role in the compact merger rate, important for gravitational waves that, in turn, can produce a new class of ultrashort GRBs.

  11. The CHARA Catalog of Orbital Elements of Spectroscopic Binary Stars

    NASA Astrophysics Data System (ADS)

    Taylor, S. F.; McAlister, H. A.; Harvin, J. A.

    2003-12-01

    Optical interferometry is entering a new age with several ground-based longbaseline observatories now making observations of unprecedented resolution. Interferometers bring a new level of resolution to bear on spectroscopic binaries, enabling the full extraction of the physical parameters for the component stars with high accuracy. In the case of double-lined systems, a geometrically determined orbital parallax becomes available as well. The first step in preparing to observe spectroscopic binaries is to list them, which has not been done since the 1989 publication of the Eighth Catalogue of the Orbital Elements of Spectroscopic Binaries by Batten, et al. (1989). We present a new catalog with roughly half again as many listings as the Eighth Catalog. Angular separation predictions are made for each catalog entry. The numbers of spectroscopic binaries available for study as a function of several important observational parameters are explored, and in particular, the number of spectroscopic binaries as a function of expected separation is discussed. CHARA gratefully acknowledges the support of the National Science Foundation, the offices of the Dean of the College of Arts and Sciences, the Vice President for Research at Georgia State University, the W.M. Keck Foundation, and the David and Lucile Packard Foundation.

  12. Magnetic Energy Production by Turbulence in Binary Neutron Star Mergers

    NASA Astrophysics Data System (ADS)

    Zrake, Jonathan; MacFadyen, Andrew I.

    2013-06-01

    The simultaneous detection of electromagnetic and gravitational wave emission from merging neutron star binaries would greatly aid in their discovery and interpretation. By studying turbulent amplification of magnetic fields in local high-resolution simulations of neutron star merger conditions, we demonstrate that magnetar-level (gsim 1016 G) fields are present throughout the merger duration. We find that the small-scale turbulent dynamo converts 60% of the randomized kinetic energy into magnetic fields on a merger timescale. Since turbulent magnetic energy dissipates through reconnection events that accelerate relativistic electrons, turbulence may facilitate the conversion of orbital kinetic energy into radiation. If 10-4 of the ~1053 erg of orbital kinetic available gets processed through reconnection and creates radiation in the 15-150 keV band, then the fluence at 200 Mpc would be 10-7 erg cm-2, potentially rendering most merging neutron stars in the advanced LIGO and Virgo detection volumes detectable by Swift BAT.

  13. Simulating binary neutron stars: Dynamics and gravitational waves

    NASA Astrophysics Data System (ADS)

    Anderson, Matthew; Hirschmann, Eric W.; Lehner, Luis; Liebling, Steven L.; Motl, Patrick M.; Neilsen, David; Palenzuela, Carlos; Tohline, Joel E.

    2008-01-01

    We model two mergers of orbiting binary neutron stars, the first forming a black hole and the second a differentially rotating neutron star. We extract gravitational waveforms in the wave zone. Comparisons to a post-Newtonian analysis allow us to compute the orbital kinematics, including trajectories and orbital eccentricities. We verify our code by evolving single stars and extracting radial perturbative modes, which compare very well to results from perturbation theory. The Einstein equations are solved in a first-order reduction of the generalized harmonic formulation, and the fluid equations are solved using a modified convex essentially non-oscillatory method. All calculations are done in three spatial dimensions without symmetry assumptions. We use the had computational infrastructure for distributed adaptive mesh refinement.

  14. Binary interactions with high accretion rates onto main sequence stars

    NASA Astrophysics Data System (ADS)

    Shiber, Sagiv; Schreier, Ron; Soker, Noam

    2016-07-01

    Energetic outflows from main sequence stars accreting mass at very high rates might account for the powering of some eruptive objects, such as merging main sequence stars, major eruptions of luminous blue variables, e.g., the Great Eruption of Eta Carinae, and other intermediate luminosity optical transients (ILOTs; red novae; red transients). These powerful outflows could potentially also supply the extra energy required in the common envelope process and in the grazing envelope evolution of binary systems. We propose that a massive outflow/jets mediated by magnetic fields might remove energy and angular momentum from the accretion disk to allow such high accretion rate flows. By examining the possible activity of the magnetic fields of accretion disks, we conclude that indeed main sequence stars might accrete mass at very high rates, up to ≈ 10‑2 M ⊙ yr‑1 for solar type stars, and up to ≈ 1 M ⊙ yr‑1 for very massive stars. We speculate that magnetic fields amplified in such extreme conditions might lead to the formation of massive bipolar outflows that can remove most of the disk's energy and angular momentum. It is this energy and angular momentum removal that allows the very high mass accretion rate onto main sequence stars.

  15. Effectual template bank for the detection of gravitational waves from inspiralling compact binaries with generic spins

    NASA Astrophysics Data System (ADS)

    Ajith, P.; Fotopoulos, N.; Privitera, S.; Neunzert, A.; Mazumder, N.; Weinstein, A. J.

    2014-04-01

    We report the construction of a three-dimensional template bank for the search for gravitational waves from inspiralling binaries consisting of spinning compact objects. The parameter space consists of two dimensions describing the mass parameters and one "reduced-spin" parameter, which describes the secular (nonprecessing) spin effects in the waveform. The template placement is based on an efficient stochastic algorithm and makes use of the semianalytical computation of a metric in the parameter space. We demonstrate that for "low-mass" (m1+m2≲12M⊙) binaries, this template bank achieves effective fitting factors ˜0.92- 0.99 towards signals from generic spinning binaries in the advanced detector era over the entire parameter space of interest (including binary neutron stars, binary black holes, and black-hole neutron-star binaries). This provides a powerful and viable method for searching for gravitational waves from generic spinning low-mass compact binaries. Under the assumption that spin magnitudes of black holes (neutron stars) are uniformly distributed between 0-0.98 [0-0.4] and spin angles are isotropically distributed, the expected improvement in the average detection volume (at a fixed signal-to-noise-ratio threshold) of a search using this reduced-spin bank is ˜20%-52%, as compared to a search using a nonspinning bank.

  16. Observed rotational properties of the O-type stars in 30 Doradus: single stars and binaries

    NASA Astrophysics Data System (ADS)

    Hernan Ramirez Agudelo, Oscar; Sana, Hugues; de Koter, Alex; Tramper, Frank; de Mink, Selma; Vlt-Flames Tarantula Survey

    2015-01-01

    The initial distribution of the spin rates of massive stars is a fingerprint of their formation process. The stellar spin rate is also one of the main properties that control the evolution and ultimate fate of these objects.Using ground-based multi-object optical spectroscopy obtained in the framework of the VLT/FLAMES Tarantula Survey we established the projected rotational velocities, vsini, of a sample of ~330 O-type objects located in the 30 Doradus (30 Dor) region in the Large Magellanic Cloud. The sample is composed by ~200 spectroscopic single stars and ~110 stars in binary systems (~110 primaries and ~30 secondaries). The vsini values are derived from the most commonly used methods, i.e. full-width at half-maximum, Fourier transform, and line profile fitting, applied to a set of spectral lines.The most distinctive feature of the vsini distributions of the presumed-single stars, primaries, and secondaries in 30 Dor is a low-velocity peak at around 100 km/s. Stellar winds are not expected to have spun-down the bulk of the stars significantly since their arrival on the main sequence and therefore the peak of presumed-single stars is likely to represent the outcome of the formation process. Whereas the spin distribution of presumed-single stars shows a well developed tail of stars rotating more rapidly than 300 km/s, primaries and secondaries do not feature such a high-velocity tail. The tail of the presumed-single star distribution is attributed for the most part -- and could potentially be completely due -- to spun-up binary products that appear as single stars or that have merged. This would be consistent with the lack of such post-interaction products in the binary sample, that is expected to be dominated by pre-interaction systems. The peak in this distribution is broader and is shifted toward somewhat higher spin rates compared to the distribution of spectroscopic-single stars. Systems displaying large radial velocity variations, typical for short period

  17. Generalized Solution for Binary Star Ephemerides and Apsidal Motion

    NASA Astrophysics Data System (ADS)

    van Hamme, W. V.; Wilson, R. E.

    1998-12-01

    We demonstrate generalized determination of apsidal motion rates (domega /dt's), orbital periods (P's), and period changes (dP/dt's) in binary stars. Our method can use eclipses but is not restricted to eclipse data. A general binary star program solves for domega /dt and/or ephemeris parameters together with other binary star quantities, and combines radial velocities and light curves within a coherent analysis. We can use data that may have large timewise gaps and may be far less than optimally distributed over time. The method is particularly useful when the apsidal period is long and eclipse timings cover only a small part of the cycle. We show apsidal motion results for AS Cam and find a domega /dt of 18.20+/-0.66 arcdeg /100;yr. This result compares to a domega /dt of 13.2+/-1.8 arcdeg /100;yr obtained from a traditional weighted least squares fit to almost 100 years of times of minima, which is 3.3 times smaller than predicted by theory. Other published estimates for the apsidal motion rate are 15.0+/-5.3 arcdeg /100;yr by Maloney, Guinan & Mukherjee (1991, AJ, 102, 256), and 18.3+/-2.6 arcdeg /100;yr by Wolf, \\u{S}arounova & Diethelm (1996, A&AS, 116, 463). Apsidal motion determined from times of minima depends on the value of the eccentricity e. Our result is for e = 0.1633, obtained from the light and velocity solution. The new domega /dt from the general analysis is 2.4 times smaller than theory, with a standard error 3 times smaller than in the traditional method. Our apsidal period of 1978+/-71 year is based on only 30 years of light and velocity curves, or 1.5% of the cycle. The method also works well in measuring period changes in long period giant binaries (such as symbiotics), considering that these stars are typically observed in fragments and that very few show eclipses that are useful as timing ticks. Our dP/dt results for the symbiotic binary AG Peg have implications for its future evolution. Natural extensions of the idea can include other

  18. Estimating the Binary Fraction of Central Stars of Planetary Nebulae

    NASA Astrophysics Data System (ADS)

    Douchin, Dimitri

    2015-01-01

    Planetary nebulae are the end-products of intermediate-mass stars evolution, following a phase of expansion of their atmospheres at the end of their lives. Observationally, it has been estimated that 80% of them have non-spherical shapes. Such a high fraction is puzzling and has occupied the planetary nebula community for more than 30 years. One scenario that would allow to justify the observed shapes is that a comparable fraction of the progenitors of central stars of planetary nebula (CSPN) are not single, but possess a companion. The shape of the nebulae would then be the result of an interaction with this companion. The high fraction of non-spherical planetary nebulae would thus imply a high fraction of binary central stars of planetary nebulae, making binarity a preferred channel for planetary nebula formation. After presenting the current state of knowledge regarding planetary nebula formation and shaping and reviewing the diverse efforts to find binaries in planetary nebulae, I present my work to detect a near-infrared excess that would be the signature of the presence of cool companions. The first part of the project consists in the analysis of data and photometry acquired and conducted by myself. The second part details an attempt to make use of archived datasets: the Sloan Digital Sky Survey Data Release 7 optical survey and the extended database assembled by Frew (2008). I also present results from a radial velocity analysis of VLT/UVES spectra for 14 objects aiming to the detection of spectroscopic companions. Finally I give details of the analysis of optical photometry data from our observations associated to the detection of companions around central stars of planetary nebulae using the photometric variability technique. The main result of this thesis is from the near-infrared excess studies which I combine with previously published data. I conclude that if the detected red and NIR flux excess is indicative of a stellar companion then the binary

  19. Radial Velocity Studies of Close Binary Stars. XV

    NASA Astrophysics Data System (ADS)

    Pribulla, Theodor; Rucinski, Slavek M.; Blake, R. M.; Lu, Wenxian; Thomson, J. R.; DeBond, Heide; Karmo, Toomas; De Ridder, Archie; Ogłoza, Waldemar; Stachowski, Greg; Siwak, Michal

    2009-03-01

    Radial velocity (RV) measurements and sine curve fits to the orbital RV variations are presented for the last eight close binary systems analyzed in the same way as in the previous papers of this series: QX And, DY Cet, MR Del, HI Dra, DD Mon, V868 Mon, ER Ori, and Y Sex. For another seven systems (TT Cet, AA Cet, CW Lyn, V563 Lyr, CW Sge, LV Vir, and MW Vir), phase coverage is insufficient to provide reliable orbits but RVs of individual components were measured. Observations of a few complicated systems observed throughout the David Dunlap Observatory (DDO) close binary program are also presented; among them is an especially interesting multiple system V857 Her which—in addition to the contact binary—very probably contains one or more subdwarf components of much earlier spectral type. All suspected binaries which were found to be most probably pulsating stars are briefly discussed in terms of mean RVs and projected rotation velocities (vsin i) as well as spectral-type estimates. In two of them, CU CVn and V752 Mon, the broadening functions show a clear presence of nonradial pulsations. The previously missing spectral types for Paper I are given here in addition to such estimates for most of the program stars of this paper. Based on the data obtained at the David Dunlap Observatory, University of Toronto, Toronto, Canada.

  20. CHARACTERIZATION OF THE MOST LUMINOUS STAR IN M33: A SUPER SYMBIOTIC BINARY

    SciTech Connect

    Mikołajewska, Joanna; Iłkiewicz, Krystian; Caldwell, Nelson; Shara, Michael M.

    2015-01-30

    We present the first spectrum of the most luminous infrared star in M33, and use it to demonstrate that the object is almost certainly a binary composed of a massive O star and a dust-enshrouded red hypergiant. This is the most luminous symbiotic binary ever discovered. Its radial velocity is an excellent match to that of the hydrogen gas in the disk of M33, supporting our interpretation that it is a very young and massive binary star.

  1. Equilibrium Structures of Differentially Rotating Primary Components of Binary Stars

    NASA Astrophysics Data System (ADS)

    Mohan, C.; Lal, A. K.; Singh, V. P.

    1997-11-01

    In this paper a method is proposed for computing the equilibrium structures and various other observable physical parameters of the primary components of stars in binary systems assuming that the primary is more massive than the secondary and is rotating differentially about its axis. Kippenhahn and Thomas averaging approach (1970) is used in a manner earlier used by Mohan, Saxena and Agarwal (1990) to incorporate the rotational and tidal effects in the equations of stellar structure. Explicit expressions for the distortional terms appearing in the stellar structure equations have been obtained by assuming a general law of differential rotation of the typeω2 = b 0+b 1 s 2+b 2 s 4, where ω is the angular velocity of rotation of a fluid element in the star at a distance s from the axis of rotation, and b 0, b 1, b 2 are suitably chosen numerical constants. The expressions incorporate the effects of differential rotation and tidal distortions up to second order terms. The use of the proposed method has been illustrated by applying it to obtain the structures and observable parameters of certain differentially rotating primary components of the binary stars assuming the primary components to have polytropic structures.

  2. Winds of Binary AGB Stars as Observed by Herschel

    NASA Astrophysics Data System (ADS)

    Mayer, A.; Jorissen, A.; Kerschbaum, F.; Ottensamer, R.; Mečina, M.; Paladini, C.; Cox, N. L. J.; Nowotny, W.; Aringer, B.; Pourbaix, D.; Mohamed, S.; Siopis, C.; Groenewegen, M. A. T.

    2015-08-01

    We present Herschel/PACS observations of the large-scale environments of binary AGB stars as part of the Mass-loss of Evolved StarS (MESS) sample. From the literature we found 18 of the objects to be members of physically bound multiple systems. Several show a large-scale far-IR emission which differs significantly from spherical symmetry. A probable cause is the gravitational force of the companion on the stellar AGB wind and the mass-losing star itself. A spiral pattern is thereby imprinted in the dusty stellar wind. The most remarkable structures are found around o Ceti, W Aquilæ, R Aquarii, and π1 Gruis. The environments of o Cet and W Aql show a spiral pattern while the symbiotic nature of R Aqr is revealed as two opposing arms which reflect a nova outburst. The emission around π1 Gru is dominated by two structures, a disk and an arc, which are presumably not caused by the same companion. We found evidence that π1 Gru is a hierarchical triple system in which a close companion attracts the AGB wind onto the orbital plane and the outer companion forms a spiral arm. These far-IR observations underline the role of a companion as a major external influence in creating asymmetric winds in the AGB phase, even before the star becomes a planetary nebula (PN).

  3. Phenomenological Modelling of a Group of Eclipsing Binary Stars

    NASA Astrophysics Data System (ADS)

    Andronov, Ivan L.; Tkachenko, Mariia G.; Chinarova, Lidia L.

    2016-03-01

    Phenomenological modeling of variable stars allows determination of a set of the parameters, which are needed for classification in the "General Catalogue of Variable Stars" and similar catalogs. We apply a recent method NAV ("New Algol Variable") to eclipsing binary stars of different types. Although all periodic functions may be represented as Fourier series with an infinite number of coefficients, this is impossible for a finite number of the observations. Thus one may use a restricted Fourier series, i.e. a trigonometric polynomial (TP) of order s either for fitting the light curve, or to make a periodogram analysis. However, the number of parameters needed drastically increases with decreasing width of minimum. In the NAV algorithm, the special shape of minimum is used, so the number of parameters is limited to 10 (if the period and initial epoch are fixed) or 12 (not fixed). We illustrate the NAV method by application to a recently discovered Algol-type eclipsing variable 2MASS J11080308-6145589 (in the field of previously known variable star RS Car) and compare results to that obtained using the TP fits. For this system, the statistically optimal number of parameters is 44, but the fit is still worse than that of the NAV fit. Application to the system GSC 3692-00624 argues that the NAV fit is better than the TP one even for the case of EW-type stars with much wider eclipses. Model parameters are listed.

  4. Cool and Luminous Transients from Mass-Losing Binary Stars

    NASA Astrophysics Data System (ADS)

    Pejcha, Ondrej; Metzger, Brian D.; Tomida, Kengo

    2016-01-01

    We study transients produced by equatorial disk-like outflows from catastrophically mass-losing binary stars with an asymptotic velocity and energy deposition rate near the inner edge which are proportional to the binary escape velocity. As a test case, we present the first smoothed-particle radiation-hydrodynamics calculations of the mass loss from the outer Lagrange point with realistic equation of state and opacities. The mass-losing binary outflows produce luminosities reaching up to 106 L⊙ and the effective temperatures are between 500 and 6000 K, which is compatible with those of many of the class of recently-discovered red transients such as V838 Mon and V1309 Sco. Dust readily forms in the outflow, potentially in a catastrophic global cooling transition. The appearance of the transient is viewing angle-dependent due to vastly different optical depths parallel and perpendicular to the binary plane. We predict a correlation between the peak luminosity and the outflow velocity, which is roughly obeyed by the known red transients.

  5. Electromagnetic Counterparts from Tilted Magnetized Binary Neutron-Stars Mergers

    NASA Astrophysics Data System (ADS)

    Ponce, Marcelo; Palenzuela, Carlos; Motl, Patrick M.; Anderson, Matthew; Hirschmann, Eric W.; Lehner, Luis; Liebling, Steven L.; Neilsen, David

    2014-03-01

    Recent studies have demonstrated that the interaction of magnetospheres in binary neutron star systems can radiate strongly electromagnetically. We study here a broader set of configurations accounting for tilted/misaligned dipoles in coalescing binaries and analyze the resulting Poynting flux and its correlation to the dynamics. In particular, the misalignment of the dipoles results in a very dynamic system with magnetic reconnections, sheer layers, and current sheets. The electromagnetic radiation displays a distinctive pulsating behaviour tied to the orbital dynamics and stellar dipole orientations and the overall power of this radiation. This work was supported by the NSF grants PHY-0969827 (LIU), PHY-0969811 (BYU), NASA's ATP grant NNX13AH01G, and NSERC through a Discovery Grant.

  6. Observational Investigations on Contact Binaries in Multiple-star Systems and Star Clusters

    NASA Astrophysics Data System (ADS)

    Liu, L.

    2013-01-01

    The W UMa-type contact binaries are strongly interacting systems whose components both fill their critical Roche lobes and share a convective common envelope. The models of contact binaries are bottlenecked due to too many uncertain parameters. In the 1960s and 1970s, the common convective envelope model was accepted after several fierce controversies. And then, the thermal relaxation oscillation (TRO) model, the discontinuity model, and the angular momentum loss (AML) model appeared. However, in the past forty years, there lacked remarkable advance. The coexistence of many unknown parameters blocks the theoretical development of contact binaries. A study on the contact binaries in multiple star systems and star clusters, which could provide lots of information for their formation and evolution, may be a potential growing point for understanding these objects. More and more evidence shows that many of contact binaries are located in multiple star systems and star clusters. In this thesis, we observed and analyzed contact binaries in the forementioned systems. The observational and theoretical studies for contact binary are also summarized briefly. The results obtained are as follows: (1) Three contact binaries V1128 Tau, GZ And, VW Boo which possess visual companions show periodic oscillations. The period ranges from 16.7 years to 46.5 years. These oscillations probably come from the orbital movement of a close third body. (2) Four contact binaries GSC 02393-00680, V396 Mon, FU Dra, SS Ari which do not have visual companions also present periodic oscillations. Whether they are real members of multiple star systems needs further investigations. These oscillations probably result from the orbital movement of a close M-type companion. (3) The periods of three contact binaries EQ Cep, ER Cep and V371 Cep in the old open cluster NGC 188 show a long-term increase. There is a cyclic period oscillation in ER Cep, with a period of 5.4 years. We find that the total mass of

  7. Quasiequilibrium sequences of binary neutron stars undergoing dynamical scalarization

    NASA Astrophysics Data System (ADS)

    Taniguchi, Keisuke; Shibata, Masaru; Buonanno, Alessandra

    2015-01-01

    We calculate quasiequilibrium sequences of equal-mass, irrotational binary neutron stars in a scalar-tensor theory of gravity that admits dynamical scalarization. We model neutron stars with realistic equations of state (notably through piecewise polytropic equations of state). Using these quasiequilibrium sequences we compute the binary's scalar charge and binding energy versus orbital angular frequency. We find that the absolute value of the binding energy is smaller than in general relativity, differing at most by ˜14 % at high frequencies for the cases considered. We use the newly computed binding energy and the balance equation to estimate the number of gravitational-wave (GW) cycles during the adiabatic, quasicircular inspiral stage up to the end of the sequence, which is the last stable orbit or the mass-shedding point, depending on which comes first. We find that, depending on the scalar-tensor parameters, the number of GW cycles can be substantially smaller than in general relativity. In particular, we obtain that when dynamical scalarization sets in around a GW frequency of ˜130 Hz , the sole inclusion of the scalar-tensor binding energy causes a reduction of GW cycles from ˜120 Hz up to the end of the sequence (˜1200 Hz ) of ˜11 % with respect to the general-relativity case. (The number of GW cycles from ˜120 Hz to the end of the sequence in general relativity is ˜270 .) We estimate that when the scalar-tensor energy flux is also included the reduction in GW cycles becomes of ˜24 %. Quite interestingly, dynamical scalarization can produce a difference in the number of GW cycles with respect to the general-relativity point-particle case that is much larger than the effect due to tidal interactions, which is on the order of only a few GW cycles. These results further clarify and confirm recent studies that have evolved binary neutron stars either in full numerical relativity or in post-Newtonian theory, and point out the importance of developing

  8. Binary Neutron Star Mergers: Prospects for Multimessenger Observations

    NASA Astrophysics Data System (ADS)

    Liebling, Steven; Anderson, Matthew; Lehner, Luis; Motl, Patrick; Neilsen, David; Palenzuela, Carlos; Ponce, Marcelo

    2015-04-01

    We evolve a binary system of two, equal-mass neutron stars in a quasi-circular orbit through and past merger. We consider different nuclear equations of state, which vary from soft to quite stiff, and allow for magnetization of the system and neutrino cooling via a leakage scheme. Here, I focus on potential observables, other than gravitational waves, produced mainly by the hot, strongly magnetized matter resulting from the merger and study their dependence on both the equation of state and the initial magnetic field strength.

  9. Visual Measurements of the Binary Star S 654

    NASA Astrophysics Data System (ADS)

    Frey, Thomas; Achildiyev, Irina; Alduenda, Chandra; Bridgeman, Reid; Chamberlain, Rebecca; Hendrix, Alex

    2011-01-01

    A member of the faculty and students from The Evergreen State College, Olympia, Washington, participated in the 2010 summer astronomy workshop at Pine Mountain Observatory. They learned the proper techniques and skills required for measuring the separation and position angle of binary star S 654. They learned how to calibrate an astrometric eyepiece, make appropriate measurements, do a statistical analysis, and analyze the data. The separation and position angle values obtained were 69.9 arc seconds and 237 degrees, respectively. The percent difference for each value was less than 0.5% from the literature value.

  10. Gravitational radiation from primordial solitons and soliton-star binaries

    NASA Technical Reports Server (NTRS)

    Gleiser, Marcelo

    1989-01-01

    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.

  11. Orbiting binary black hole evolutions with a multipatch high order finite-difference approach

    SciTech Connect

    Pazos, Enrique; Tiglio, Manuel; Duez, Matthew D.; Kidder, Lawrence E.; Teukolsky, Saul A.

    2009-07-15

    We present numerical simulations of orbiting black holes for around 12 cycles, using a high order multipatch approach. Unlike some other approaches, the computational speed scales almost perfectly for thousands of processors. Multipatch methods are an alternative to adaptive mesh refinement, with benefits of simplicity and better scaling for improving the resolution in the wave zone. The results presented here pave the way for multipatch evolutions of black hole-neutron star and neutron star-neutron star binaries, where high resolution grids are needed to resolve details of the matter flow.

  12. ABSOLUTE PROPERTIES OF THE ECLIPSING BINARY STAR V335 SERPENTIS

    SciTech Connect

    Lacy, Claud H. Sandberg; Fekel, Francis C.; Claret, Antonio E-mail: fekel@evans.tsuniv.edu

    2012-08-15

    V335 Ser is now known to be an eccentric double-lined A1+A3 binary star with fairly deep (0.5 mag) partial eclipses. Previous studies of the system are improved with 7456 differential photometric observations from the URSA WebScope and 5666 from the NFO WebScope, and 67 high-resolution spectroscopic observations from the Tennessee State University 2 m automatic spectroscopic telescope. From dates of minima, the apsidal period is about 880 years. Accurate (better than 2%) masses and radii are determined from analysis of the two new light curves and the radial velocity curve. Theoretical models match the absolute properties of the stars at an age of about 380 Myr, though the age agreement for the two components is poor. Tidal theory correctly confirms that the orbit should still be eccentric, but we find that standard tidal theory is unable to match the observed asynchronous rotation rates of the components' surface layers.

  13. ABSOLUTE PROPERTIES OF THE ECLIPSING BINARY STAR HY VIRGINIS

    SciTech Connect

    Sandberg Lacy, Claud H.; Fekel, Francis C. E-mail: fekel@evans.tsuniv.edu

    2011-12-15

    HY Vir is found to be a double-lined F0m+F5 binary star with relatively shallow (0.3 mag) partial eclipses. Previous studies of the system are improved with 7509 differential photometric observations from the URSA WebScope and 8862 from the NFO WebScope, and 68 high-resolution spectroscopic observations from the Tennessee State University 2 m automatic spectroscopic telescope, and the 1 m coude-feed spectrometer at Kitt Peak National Observatory. Very accurate (better than 0.5%) masses and radii are determined from analysis of the new light curves and radial velocity curves. Theoretical models match the absolute properties of the stars at an age of about 1.35 Gy.

  14. Systematic Parameter Errors in Inspiraling Neutron Star Binaries

    NASA Astrophysics Data System (ADS)

    Favata, Marc

    2014-03-01

    The coalescence of two neutron stars is an important gravitational wave source for LIGO and other detectors. Numerous studies have considered the precision with which binary parameters (masses, spins, Love numbers) can be measured. Here I consider the accuracy with which these parameters can be determined in the presence of systematic errors due to waveform approximations. These approximations include truncation of the post-Newtonian (PN) series and neglect of neutron star (NS) spin, tidal deformation, or orbital eccentricity. All of these effects can yield systematic errors that exceed statistical errors for plausible parameter values. In particular, neglecting spin, eccentricity, or high-order PN terms causes a significant bias in the NS Love number. Tidal effects will not be measurable with PN inspiral waveforms if these systematic errors are not controlled.

  15. The Challenge of Observing the Zeta Aurigae Binary Stars

    NASA Astrophysics Data System (ADS)

    Melillo, Frank J.

    2013-07-01

    This author, in Holtsville, NY, has contributed to the observations of the Zeta Auriga binary stars, which included Zeta Aurigae itself and 32 Cygni. Both Zeta Aur and 32 Cygni were monitored in V and B bands during the most recent eclipses in the fall of 2011 and in late summer 2012, respectively. In addition, some spectra of both stars were captured to monitor the brightness in the near-UV section, that traces the hot companion being eclipsed. The lightcurves of both Zeta Aurigae and 32 Cygni show precise timing during the entire recent eclipses. The magnitude and duration of the eclipses in photometric V and B bands are described here, and forecasts made for future eclipses. This poster represents the work by Frank J Melillo and the observations were spaced closely enough to generate the true shape of the V and B lightcurves.

  16. Systematic parameter errors in inspiraling neutron star binaries.

    PubMed

    Favata, Marc

    2014-03-14

    The coalescence of two neutron stars is an important gravitational wave source for LIGO and other detectors. Numerous studies have considered the precision with which binary parameters (masses, spins, Love numbers) can be measured. Here I consider the accuracy with which these parameters can be determined in the presence of systematic errors due to waveform approximations. These approximations include truncation of the post-Newtonian (PN) series and neglect of neutron star (NS) spin, tidal deformation, or orbital eccentricity. All of these effects can yield systematic errors that exceed statistical errors for plausible parameter values. In particular, neglecting spin, eccentricity, or high-order PN terms causes a significant bias in the NS Love number. Tidal effects will not be measurable with PN inspiral waveforms if these systematic errors are not controlled. PMID:24679276

  17. Hybridizing Gravitationl Waveforms of Inspiralling Binary Neutron Star Systems

    NASA Astrophysics Data System (ADS)

    Cullen, Torrey; LIGO Collaboration

    2016-03-01

    Gravitational waves are ripples in space and time and were predicted to be produced by astrophysical systems such as binary neutron stars by Albert Einstein. These are key targets for Laser Interferometer and Gravitational Wave Observatory (LIGO), which uses template waveforms to find weak signals. The simplified template models are known to break down at high frequency, so I wrote code that constructs hybrid waveforms from numerical simulations to accurately cover a large range of frequencies. These hybrid waveforms use Post Newtonian template models at low frequencies and numerical data from simulations at high frequencies. They are constructed by reading in existing Post Newtonian models with the same masses as simulated stars, reading in the numerical data from simulations, and finding the ideal frequency and alignment to ``stitch'' these waveforms together.

  18. Absolute properties of the eclipsing binary star V501 Herculis

    SciTech Connect

    Lacy, Claud H. Sandberg; Fekel, Francis C. E-mail: fekel@evans.tsuniv.edu

    2014-10-01

    V501 Her is a well detached G3 eclipsing binary star with a period of 8.597687 days for which we have determined very accurate light and radial-velocity curves using robotic telescopes. Results of these data indicate that the component stars have masses of 1.269 ± 0.004 and 1.211 ± 0.003 solar masses, radii of 2.001 ± 0.003 and 1.511 ± 0.003 solar radii, and temperatures of 5683 ± 100 K and 5720 ± 100 K, respectively. Comparison with the Yonsei-Yale series of evolutionary models results in good agreement at an age of about 5.1 Gyr for a somewhat metal-rich composition. Those models indicate that the more massive, larger, slightly cooler star is just beyond core hydrogen exhaustion while the less massive, smaller, slightly hotter star has not quite reached core hydrogen exhaustion. The orbit is not yet circularized, and the components are rotating at or near their pseudosynchronous velocities. The distance to the system is 420 ± 30 pc.

  19. Binary dynamics on star networks under external perturbations

    NASA Astrophysics Data System (ADS)

    Moreira, Carolina A.; Schneider, David M.; de Aguiar, Marcus A. M.

    2015-10-01

    We study a binary dynamical process that is a representation of the voter model with two candidates and opinion makers. The voters are represented by nodes of a network of social contacts with internal states labeled 0 or 1 and nodes that are connected can influence each other. The network is also perturbed by opinion makers, a set of external nodes whose states are frozen in 0 or 1 and that can influence all nodes of the network. The quantity of interest is the probability of finding m nodes in state 1 at time t . Here we study this process on star networks, which are simple representations of hubs found in complex systems, and compare the results with those obtained for networks that are fully connected. In both cases a transition from disordered to ordered equilibrium states is observed as the number of external nodes becomes small. For fully connected networks the probability distribution becomes uniform at the critical point. For star networks, on the other hand, we show that the equilibrium distribution splits in two peaks, reflecting the two possible states of the central node. We obtain approximate analytical solutions for the equilibrium distribution that clarify the role of the central node in the process. We show that the network topology also affects the time scale of oscillations in single realizations of the dynamics, which are much faster for the star network. Finally, extending the analysis to two stars we compare our results with simulations in simple scale-free networks.

  20. Binary dynamics on star networks under external perturbations.

    PubMed

    Moreira, Carolina A; Schneider, David M; de Aguiar, Marcus A M

    2015-10-01

    We study a binary dynamical process that is a representation of the voter model with two candidates and opinion makers. The voters are represented by nodes of a network of social contacts with internal states labeled 0 or 1 and nodes that are connected can influence each other. The network is also perturbed by opinion makers, a set of external nodes whose states are frozen in 0 or 1 and that can influence all nodes of the network. The quantity of interest is the probability of finding m nodes in state 1 at time t. Here we study this process on star networks, which are simple representations of hubs found in complex systems, and compare the results with those obtained for networks that are fully connected. In both cases a transition from disordered to ordered equilibrium states is observed as the number of external nodes becomes small. For fully connected networks the probability distribution becomes uniform at the critical point. For star networks, on the other hand, we show that the equilibrium distribution splits in two peaks, reflecting the two possible states of the central node. We obtain approximate analytical solutions for the equilibrium distribution that clarify the role of the central node in the process. We show that the network topology also affects the time scale of oscillations in single realizations of the dynamics, which are much faster for the star network. Finally, extending the analysis to two stars we compare our results with simulations in simple scale-free networks. PMID:26565294

  1. KEPLER ECLIPSING BINARY STARS. II. 2165 ECLIPSING BINARIES IN THE SECOND DATA RELEASE

    SciTech Connect

    Slawson, Robert W.; Doyle, Laurance R.; Prsa, Andrej; Engle, Scott G.; Conroy, Kyle; Coughlin, Jared; Welsh, William F.; Orosz, Jerome A.; Gregg, Trevor A.; Fetherolf, Tara; Short, Donald R.; Windmiller, Gur; Rucker, Michael; Batalha, Natalie; Fabrycky, Daniel C.; Jenkins, Jon M.; Mullally, F.; Seader, Shawn E.

    2011-11-15

    The Kepler Mission provides nearly continuous monitoring of {approx}156,000 objects with unprecedented photometric precision. Coincident with the first data release, we presented a catalog of 1879 eclipsing binary systems identified within the 115 deg{sup 2} Kepler field of view (FOV). Here, we provide an updated catalog augmented with the second Kepler data release which increases the baseline nearly fourfold to 125 days. Three hundred and eighty-six new systems have been added, ephemerides and principal parameters have been recomputed. We have removed 42 previously cataloged systems that are now clearly recognized as short-period pulsating variables and another 58 blended systems where we have determined that the Kepler target object is not itself the eclipsing binary. A number of interesting objects are identified. We present several exemplary cases: four eclipsing binaries that exhibit extra (tertiary) eclipse events; and eight systems that show clear eclipse timing variations indicative of the presence of additional bodies bound in the system. We have updated the period and galactic latitude distribution diagrams. With these changes, the total number of identified eclipsing binary systems in the Kepler FOV has increased to 2165, 1.4% of the Kepler target stars. An online version of this catalog is maintained at http://keplerEBs.villanova.edu.

  2. Using stellar population models with binary stars to study the early type galaxies

    NASA Astrophysics Data System (ADS)

    Yu, Zhang

    2015-08-01

    The stellar mass, mean ages, metallicities and star formation histories of galaxy are now commonly determined via fitting multiband photometric properties of galaxies to the spectral energy distributions (SEDs) of stellar population models. The stellar population models are still poorly calibrated for certain stellar evolution stages, especially for the treatment of binary stars, which are very common in the Universe and their evolution is very different from single stars. In this work, we use the stellar population with and without binary stars to study the star formation histories (SFHs) for early type galaxies sample. Our results show that for the SFHs obtained by models with binary star are different from that without binary stars for 10% galaxy sample.

  3. The VLT Unravels the Nature of the Fastest Binary Star

    NASA Astrophysics Data System (ADS)

    2002-03-01

    Two Hot White Dwarfs Perform a Tight Dance Summary Observations with ESO's Very Large Telescope (VLT) in Chile and the Italian Telescopio Nazionale Galileo (TNG) on the Canary Islands during the past two years have enabled an international group of astronomers [1] to unravel the true nature of an exceptional binary stellar system. This system, designated RX J0806.3+1527 , was first discovered as an X-ray source of variable brightness - once every five minutes, it "switches off" for a short moment. The new observations have shown beyond doubt that this period reflects the orbital motion of two "white dwarf" stars that revolve around each other at a distance of only 80,000 km . Each of the stars is about as large as the Earth and this is the shortest orbital period known for any binary stellar system. The VLT spectrum displays lines of ionized helium, indicating that the presence of an exceedingly hot area on one of the stars - a "hot spot" with a temperature of approx. 250,000 degrees. The system is currently in a rarely seen, transitory evolutionary state . PR Photo 10a/02 : U- and R-band images of RX J0806.3+1527. PR Photo 10b/02 : Spectrum of RX J0806.3+1527 An amazing stellar binary system ESO PR Photo 10a/02 ESO PR Photo 10a/02 [Preview - JPEG: 800 x 400 pix - 440k] [Normal - JPEG: 1600 x 800 pix - 1.1M] Caption : PR Photo 10a/02 shows U and R filter images of the sky field around RX J0806.3+1527 (at centre of circle), obtained with the FORS2 multi-mode instrument on VLT KUEYEN. The object is brightest at the shorter wavelength (U-band) - reflecting its very high temperature. Technical information about the photo is available below. One year is the time it takes the Earth to move once around the Sun, our central star. This may seem quite fast when measured on the scale of the Universe, but this is a snail's motion compared to the the speed of two recently discovered stars. They revolve around each other 100,000 times faster; one full revolution takes only 321

  4. New systemic radial velocities of suspected RR Lyrae binary stars

    NASA Astrophysics Data System (ADS)

    Guggenberger, E.; Barnes, T. G.; Kolenberg, K.

    2016-05-01

    Among the tens of thousands of known RR Lyrae stars there are only a handful that show indications of possible binarity. The question why this is the case is still unsolved, and has recently sparked several studies dedicated to the search for additional RR Lyraes in binary systems. Such systems are particularly valuable because they might allow to constrain the stellar mass. Most of the recent studies, however, are based on photometry by finding a light time effect in the timings of maximum light. This approach is a very promising and successful one, but it has a major drawback: by itself, it cannot serve as a definite proof of binarity, because other phenomena such as the Blazhko effect or intrinsic period changes could lead to similar results. Spectroscopic radial velocity measurements, on the other hand, can serve as definite proof of binarity. We have therefore started a project to study spectroscopically RR Lyrae stars that are suspected to be binaries. We have obtained radial velocity (RV) curves with the 2.1m telescope at McDonald observatory. From these we derive systemic RVs which we will compare to previous measurements in order to find changes induced by orbital motions. We also construct templates of the RV curves that can facilitate future studies. We also observed the most promising RR Lyrae binary candidate, TU UMa, as no recent spectroscopic measurements were available. We present a densely covered pulsational RV curve, which will be used to test the predictions of the orbit models that are based on the O - C variations.

  5. Investigating Binary Wolf-Rayet Binary Stars as Potential Gamma-Ray Source

    NASA Astrophysics Data System (ADS)

    Meadows, Jacqueline; Alexander, Michael J.; McSwain, M. Virginia

    2015-01-01

    Wolf-Rayets are massive, hot, and luminous evolved stars with strong stellar winds. When paired with another massive star emitting strong stellar winds, the region where their winds collide produces a bow shock that may emit gamma-rays. This work seeks to find such a colliding wind binary by correlating the orbital period of a binary Wolf-Rayet with periodic changes in flux in nearby gamma-ray sources observed by Fermi Gamma-ray Space Telescope Large Area Telescope (LAT). We selected three binary Wolf-Rayet stars for analysis. WR 39 and WR 48 are in close proximity to unassociated sources from the LAT 2-Year Point Source Catalog (2FGL). WR 140 was selected on the basis of being a double-lined spectroscopic binary; the close passage of the two stars may contribute to colliding winds that could produce gamma-rays. We first used the Fermi Science Tools to calculate average flux values. The orbital period of WR 39 has not been established; so rather than creating a folded light curve, photon data for its proposed 2FGL counterpart were next analyzed using seven-day time bins in an attempt to use periodic behavior in the 2FGL source to find the orbital period of WR 39. However, no periodic behavior was evident in the plotted data. Since WR 48 lies just outside error ellipse of its proposed 2FGL counterpart, we performed the six-year likelihood analysis twice. First, WR 48 was manually inserted as a point source; this resulted in a non-converging fit. Instead, we used the proposed 2FGL counterpart as the object of interest. After calculating the average flux, we separated the photon data into phase bins based on the 18.34 day period of WR 48. The resulting folded light curve does not show any periodic behavior. WR 140 was also manually inserted as a point source; the analysis of the six-year data set failed to establish the existence of a gamma-ray source at the location of WR 140 and no further analysis was performed on this source.This research took place at Lehigh

  6. Dynamical mass ejection from binary neutron star mergers

    NASA Astrophysics Data System (ADS)

    Radice, David; Galeazzi, Filippo; Lippuner, Jonas; Roberts, Luke F.; Ott, Christian D.; Rezzolla, Luciano

    2016-08-01

    We present fully general-relativistic simulations of binary neutron star mergers with a temperature and composition dependent nuclear equation of state. We study the dynamical mass ejection from both quasi-circular and dynamical-capture eccentric mergers. We systematically vary the level of our treatment of the microphysics to isolate the effects of neutrino cooling and heating and we compute the nucleosynthetic yields of the ejecta. We find that eccentric binaries can eject significantly more material than quasi-circular binaries and generate bright infrared and radio emission. In all our simulations the outflow is composed of a combination of tidally- and shock-driven ejecta, mostly distributed over a broad $\\sim 60^\\circ$ angle from the orbital plane, and, to a lesser extent, by thermally driven winds at high latitudes. Ejecta from eccentric mergers are typically more neutron rich than those of quasi-circular mergers. We find neutrino cooling and heating to affect, quantitatively and qualitatively, composition, morphology, and total mass of the outflows. This is also reflected in the infrared and radio signatures of the binary. The final nucleosynthetic yields of the ejecta are robust and insensitive to input physics or merger type in the regions of the second and third r-process peaks. The yields for elements on the first peak vary between our simulations, but none of our models is able to explain the Solar abundances of first-peak elements without invoking additional first-peak contributions from either neutrino and viscously-driven winds operating on longer timescales after the mergers, or from core-collapse supernovae.

  7. Dynamical mass ejection from binary neutron star mergers

    NASA Astrophysics Data System (ADS)

    Radice, David; Galeazzi, Filippo; Lippuner, Jonas; Roberts, Luke F.; Ott, Christian D.; Rezzolla, Luciano

    2016-08-01

    We present fully general-relativistic simulations of binary neutron star mergers with a temperature and composition dependent nuclear equation of state. We study the dynamical mass ejection from both quasi-circular and dynamical-capture eccentric mergers. We systematically vary the level of our treatment of the microphysics to isolate the effects of neutrino cooling and heating and we compute the nucleosynthetic yields of the ejecta. We find that eccentric binaries can eject significantly more material than quasi-circular binaries and generate bright infrared and radio emission. In all our simulations the outflow is composed of a combination of tidally- and shock-driven ejecta, mostly distributed over a broad ˜60° angle from the orbital plane, and, to a lesser extent, by thermally driven winds at high latitudes. Ejecta from eccentric mergers are typically more neutron rich than those of quasi-circular mergers. We find neutrino cooling and heating to affect, quantitatively and qualitatively, composition, morphology, and total mass of the outflows. This is also reflected in the infrared and radio signatures of the binary. The final nucleosynthetic yields of the ejecta are robust and insensitive to input physics or merger type in the regions of the second and third r-process peaks. The yields for elements on the first peak vary between our simulations, but none of our models is able to explain the Solar abundances of first-peak elements without invoking additional first-peak contributions from either neutrino and viscously-driven winds operating on longer time-scales after the mergers, or from core-collapse supernovae.

  8. Dynamical Mass Ejection from Binary Neutron Star Mergers

    NASA Astrophysics Data System (ADS)

    Radice, David; Galeazzi, Filippo; Lippuner, Jonas; Roberts, Luke F.; Ott, Christian D.; Rezzolla, Luciano

    2016-05-01

    We present fully general-relativistic simulations of binary neutron star mergers with a temperature and composition dependent nuclear equation of state. We study the dynamical mass ejection from both quasi-circular and dynamical-capture eccentric mergers. We systematically vary the level of our treatment of the microphysics to isolate the effects of neutrino cooling and heating and we compute the nucleosynthetic yields of the ejecta. We find that eccentric binaries can eject significantly more material than quasi-circular binaries and generate bright infrared and radio emission. In all our simulations the outflow is composed of a combination of tidally- and shock-driven ejecta, mostly distributed over a broad ˜60° angle from the orbital plane, and, to a lesser extent, by thermally driven winds at high latitudes. Ejecta from eccentric mergers are typically more neutron rich than those of quasi-circular mergers. We find neutrino cooling and heating to affect, quantitatively and qualitatively, composition, morphology, and total mass of the outflows. This is also reflected in the infrared and radio signatures of the binary. The final nucleosynthetic yields of the ejecta are robust and insensitive to input physics or merger type in the regions of the second and third r-process peaks. The yields for elements on the first peak vary between our simulations, but none of our models is able to explain the Solar abundances of first-peak elements without invoking additional first-peak contributions from either neutrino and viscously-driven winds operating on longer timescales after the mergers, or from core-collapse supernovae.

  9. The VLT Unravels the Nature of the Fastest Binary Star

    NASA Astrophysics Data System (ADS)

    2002-03-01

    Two Hot White Dwarfs Perform a Tight Dance Summary Observations with ESO's Very Large Telescope (VLT) in Chile and the Italian Telescopio Nazionale Galileo (TNG) on the Canary Islands during the past two years have enabled an international group of astronomers [1] to unravel the true nature of an exceptional binary stellar system. This system, designated RX J0806.3+1527 , was first discovered as an X-ray source of variable brightness - once every five minutes, it "switches off" for a short moment. The new observations have shown beyond doubt that this period reflects the orbital motion of two "white dwarf" stars that revolve around each other at a distance of only 80,000 km . Each of the stars is about as large as the Earth and this is the shortest orbital period known for any binary stellar system. The VLT spectrum displays lines of ionized helium, indicating that the presence of an exceedingly hot area on one of the stars - a "hot spot" with a temperature of approx. 250,000 degrees. The system is currently in a rarely seen, transitory evolutionary state . PR Photo 10a/02 : U- and R-band images of RX J0806.3+1527. PR Photo 10b/02 : Spectrum of RX J0806.3+1527 An amazing stellar binary system ESO PR Photo 10a/02 ESO PR Photo 10a/02 [Preview - JPEG: 800 x 400 pix - 440k] [Normal - JPEG: 1600 x 800 pix - 1.1M] Caption : PR Photo 10a/02 shows U and R filter images of the sky field around RX J0806.3+1527 (at centre of circle), obtained with the FORS2 multi-mode instrument on VLT KUEYEN. The object is brightest at the shorter wavelength (U-band) - reflecting its very high temperature. Technical information about the photo is available below. One year is the time it takes the Earth to move once around the Sun, our central star. This may seem quite fast when measured on the scale of the Universe, but this is a snail's motion compared to the the speed of two recently discovered stars. They revolve around each other 100,000 times faster; one full revolution takes only 321

  10. Time-Resolved Spectroscopy of Active Binary Stars

    NASA Technical Reports Server (NTRS)

    Brown, Alexander

    2000-01-01

    This NASA grant covered EUVE observing and data analysis programs during EUVE Cycle 5 GO observing. The research involved a single Guest Observer project 97-EUVE-061 "Time-Resolved Spectroscopy of Active Binary Stars". The grant provided funding that covered 1.25 months of the PI's salary. The activities undertaken included observation planning and data analysis (both temporal and spectral). This project was awarded 910 ksec of observing time to study seven active binary stars, all but one of which were actually observed. Lambda-And was observed on 1997 Jul 30 - Aug 3 and Aug 7-14 for a total of 297 ksec; these observations showed two large complex flares that were analyzed by Osten & Brown (1999). AR Psc, observed for 350 ksec on 1997 Aug 27 - Sep 13, showed only relatively small flares that were also discussed by Osten & Brown (1999). EUVE observations of El Eri were obtained on 1994 August 24-28, simultaneous with ASCA X-ray spectra. Four flares were detected by EUVE with one of these also observed simultaneously, by ASCA. The other three EUVE observations were of the stars BY Dra (1997 Sep 22-28), V478 Lyr (1998 May 18-27), and sigma Gem (1998 Dec 10-22). The first two stars showed a few small flares. The sigma Gem data shows a beautiful complete flare with a factor of ten peak brightness compared to quiescence. The flare rise and almost all the decay phase are observed. Unfortunately no observations in other spectral regions were obtained for these stars. Analysis of the lambda-And and AR Psc observations is complete and the results were published in Osten & Brown (1999). Analysis of the BY Dra, V478 Lyr and sigma Gem EUVE data is complete and will be published in Osten (2000, in prep.). The El Eri EUV analysis is also completed and the simultaneous EUV/X-ray study will be published in Osten et al. (2000, in prep.). Both these latter papers will be submitted in summer 2000. All these results will form part of Rachel Osten's PhD thesis.

  11. Merging binary stars and the magnetic white dwarfs

    NASA Astrophysics Data System (ADS)

    Briggs, Gordon P.; Ferrario, Lilia; Tout, Christopher A.; Wickramasinghe, Dayal T.; Hurley, Jarrod R.

    2015-02-01

    A magnetic dynamo driven by differential rotation generated when stars merge can explain strong fields in certain classes of magnetic stars, including the high field magnetic white dwarfs (HFMWDs). In their case the site of the differential rotation has been variously proposed to be within a common envelope, the massive hot outer regions of a merged degenerate core or an accretion disc formed by a tidally disrupted companion that is subsequently incorporated into a degenerate core. We synthesize a population of binary systems to investigate the stellar merging hypothesis for observed single HFMWDs. Our calculations provide mass distribution and the fractions of white dwarfs that merge during a common envelope phase or as double degenerate systems in a post-common-envelope phase. We vary the common envelope efficiency parameter α and compare with observations. We find that this hypothesis can explain both the observed incidence of magnetism and the mass distribution of HFMWDs for a wide range of α. In this model, the majority of the HFMWDs are of the carbon-oxygen type and merge within a common envelope. Less than about a quarter of a per cent of HFMWDs originate from double degenerate stars that merge after common envelope evolution and these populate the high-mass tail of the HFMWD mass distribution.

  12. MAGNETIC ENERGY PRODUCTION BY TURBULENCE IN BINARY NEUTRON STAR MERGERS

    SciTech Connect

    Zrake, Jonathan; MacFadyen, Andrew I.

    2013-06-01

    The simultaneous detection of electromagnetic and gravitational wave emission from merging neutron star binaries would greatly aid in their discovery and interpretation. By studying turbulent amplification of magnetic fields in local high-resolution simulations of neutron star merger conditions, we demonstrate that magnetar-level ({approx}> 10{sup 16} G) fields are present throughout the merger duration. We find that the small-scale turbulent dynamo converts 60% of the randomized kinetic energy into magnetic fields on a merger timescale. Since turbulent magnetic energy dissipates through reconnection events that accelerate relativistic electrons, turbulence may facilitate the conversion of orbital kinetic energy into radiation. If 10{sup -4} of the {approx}10{sup 53} erg of orbital kinetic available gets processed through reconnection and creates radiation in the 15-150 keV band, then the fluence at 200 Mpc would be 10{sup -7} erg cm{sup -2}, potentially rendering most merging neutron stars in the advanced LIGO and Virgo detection volumes detectable by Swift BAT.

  13. ellc: Light curve model for eclipsing binary stars and transiting exoplanets

    NASA Astrophysics Data System (ADS)

    Maxted, P. F. L.

    2016-03-01

    ellc analyzes the light curves of detached eclipsing binary stars and transiting exoplanet systems. The model represents stars as triaxial ellipsoids, and the apparent flux from the binary is calculated using Gauss-Legendre integration over the ellipses that are the projection of these ellipsoids on the sky. The code can also calculate the fluxweighted radial velocity of the stars during an eclipse (Rossiter-McLaghlin effect). ellc can model a wide range of eclipsing binary stars and extrasolar planetary systems, and can enable the use of modern Monte Carlo methods for data analysis and model testing.

  14. Dynamics of primordial binary stars in multiple-population globular clusters

    NASA Astrophysics Data System (ADS)

    Hong, Jongsuk; Vesperini, Enrico; Sollima, Antonio; McMillan, Steve; D'Antona, Franca; D'Ercole, Annibale

    2016-02-01

    We have performed a survey of N-body simulations to explore the dynamics of primordial binaries in multiple-population globular clusters. We show that, as a consequence of the initial differences between the spatial distribution of first-generation (FG) and second-generation (SG) stars, SG binaries are disrupted more efficiently than FG binaries. The effects of dynamical evolution on the surviving binaries produces a difference between the SG and the FG binary binding energy distribution with the SG population characterized by a larger fraction of high binding energy (more bound) binaries. We also explore the evolution of the radial variation of the SG-to-FG binary number ratio and find that although the global binary fraction decreases more rapidly for the SG population, the local binary fraction measured in the cluster inner regions may still be dominated by SG binaries.

  15. Are either X Her or g Her Binary Stars?

    NASA Astrophysics Data System (ADS)

    Shawl, Stephen J.; Scarfe, C.

    2007-12-01

    X Her (HD 144205) and g Her (HD 148783) were observed by Shawl (AJ, 80, 602, 1975) to exhibit polarization position angles that varied with time in peculiar ways. For example, for X Her, the variations in the B- and I-filters were significant and uncorrelated, while for g Her a possible periodic position angle variation was found. At the time of that work, a literature search found no papers indicating that either star was binary, which conceivably could explain the observed variations. For this reason, in spring 2001 these stars were placed on the observing list of the second author to obtain high precision radial velocities (2001-2003 using the DAO radial velocity scanner, while from 2004 onward using a CCD). The velocity errors are estimated to be les than 1 km/s. Nearly 100 observations were collected over a range of 2343 days. After we began collecting data, Hinkle et al. (AJ 123, 1002, 2002) published a paper that included radial velocity observations of both our program stars. For both stars they had 25 spectra during 1849 days between 1995 and 2000. X Her showed obvious velocity variations with a 666 day period. Lebzelter (Astron. Astrophys 351, 644, 1999) obtained a finer grid of data and found some complex short-period variations. For g Her, they found an 838 day period, which is consistent with the long-period variation in the V-band. We will present the interim results of our analysis of the more recent data. * Guest observer at the Dominion Astrophysical Observatory, Herzberg Institute of Astrophysics, National Research Council of Canada.

  16. Database of candidates for RR Lyrae stars in binary systems - RRLyrBinCan

    NASA Astrophysics Data System (ADS)

    Liska, J.; Skarka, M.

    2016-05-01

    A new on-line database with RR Lyrae stars bound in binary systems is presented. Its purpose is to give a quick overview about known and suspected RR Lyrae stars in binaries on the basis of available literature. The first released version of the catalogue contains information about 61 double-star candidates, their orbital periods, method of detection, comments and active links to published papers.

  17. Optical microflaring on the nearby flare star binary UV Ceti

    NASA Astrophysics Data System (ADS)

    Schmitt, J. H. M. M.; Kanbach, G.; Rau, A.; Steinle, H.

    2016-05-01

    We present extremely high time resolution observations of the visual flare star binary UV Cet obtained with the Optical Pulsar Timing Analyzer (OPTIMA) at the 1.3 m telescope at Skinakas Observatory (SKO) in Crete, Greece. OPTIMA is a fiber-fed optical instrument that uses Single Photon Avalanche Diodes to measure the arrival times of individual optical photons. The time resolution of the observations presented here was 4 μs, allowing to resolve the typical millisecond variability time scales associated with stellar flares. We report the detection of very short impulsive bursts in the blue band with well resolved rise and decay time scales of about 2 s. The overall energetics put these flares at the lower end of the known flare distribution of UV Cet.

  18. Gravitational lensing of gravitational waves from merging neutron star binaries

    SciTech Connect

    Wang, Yun; Stebbins, Albert; Turner, Edwin L.

    1996-05-01

    We discuss the gravitational lensing of gravitational waves from merging neutron star binaries, in the context of advanced LIGO type gravitational wave detectors. We consider properties of the expected observational data with cut on the signal-to-noise ratio \\rho, i.e., \\rho>\\rho_0. An advanced LIGO should see unlensed inspiral events with a redshift distribution with cut-off at a redshift z_{\\rm max} < 1 for h \\leq 0.8. Any inspiral events detected at z>z_{\\rm max} should be lensed. We compute the expected total number of events which are present due to gravitational lensing and their redshift distribution for an advanced LIGO in a flat Universe. If the matter fraction in compact lenses is close to 10\\%, an advanced LIGO should see a few strongly lensed events per year with \\rho >5.

  19. Absolute properties of the eclipsing binary star IM Persei

    SciTech Connect

    Lacy, Claud H. Sandberg; Torres, Guillermo; Fekel, Francis C.; Muterspaugh, Matthew W.; Southworth, John E-mail: gtorres@cfa.harvard.edu E-mail: matthew1@coe.tsuniv.edu

    2015-01-01

    IM Per is a detached A7 eccentric eclipsing binary star. We have obtained extensive measurements of the light curve (28,225 differential magnitude observations) and radial velocity curve (81 spectroscopic observations) which allow us to fit orbits and determine the absolute properties of the components very accurately: masses of 1.7831 ± 0.0094 and 1.7741 ± 0.0097 solar masses, and radii of 2.409 ± 0.018 and 2.366 ± 0.017 solar radii. The orbital period is 2.25422694(15) days and the eccentricity is 0.0473(26). A faint third component was detected in the analysis of the light curves, and also directly observed in the spectra. The observed rate of apsidal motion is consistent with theory (U = 151.4 ± 8.4 year). We determine a distance to the system of 566 ± 46 pc.

  20. Observational Study of the Evolution of Massive Binary Stars

    NASA Astrophysics Data System (ADS)

    Burki, G.; Mayor, M.

    Six years ago an observational program on supergiant stars using CORAVEL was initiated at Geneva Observatory. About 1500 radial velocities were obtained out of a sample of 181 northern supergiants of F, G, K, M type. Nineteen new SB have been discovered and 16 others are suspected to be SB. From the catalogue of Batten et al. (1978) and the results of the authors' survey, the orbital elements are known for 25 SB having at least one supergiant component of type F to M. In each luminosity class all systems with Pcirc = P(1-e)3/2 (P, e are period and eccentricity of a binary system) shorter than a critical value have nearly circular orbits. The critical value is very well defined for class Ib: 350 - 440 days. This value is larger for classes Iab and Ia (1400 - 3900 days for class Ia).

  1. SELF-REGULATED SHOCKS IN MASSIVE STAR BINARY SYSTEMS

    SciTech Connect

    Parkin, E. R.; Sim, S. A. E-mail: s.sim@qub.ac.uk

    2013-04-20

    In an early-type, massive star binary system, X-ray bright shocks result from the powerful collision of stellar winds driven by radiation pressure on spectral line transitions. We examine the influence of the X-rays from the wind-wind collision shocks on the radiative driving of the stellar winds using steady-state models that include a parameterized line force with X-ray ionization dependence. Our primary result is that X-ray radiation from the shocks inhibits wind acceleration and can lead to a lower pre-shock velocity, and a correspondingly lower shocked plasma temperature, yet the intrinsic X-ray luminosity of the shocks, L{sub X}, remains largely unaltered, with the exception of a modest increase at small binary separations. Due to the feedback loop between the ionizing X-rays from the shocks and the wind driving, we term this scenario as self-regulated shocks. This effect is found to greatly increase the range of binary separations at which a wind-photosphere collision is likely to occur in systems where the momenta of the two winds are significantly different. Furthermore, the excessive levels of X-ray ionization close to the shocks completely suppress the line force, and we suggest that this may render radiative braking less effective. Comparisons of model results against observations reveal reasonable agreement in terms of log (L{sub X}/L{sub bol}). The inclusion of self-regulated shocks improves the match for kT values in roughly equal wind momenta systems, but there is a systematic offset for systems with unequal wind momenta (if considered to be a wind-photosphere collision).

  2. THE HOT R CORONAE BOREALIS STAR DY CENTAURI IS A BINARY

    SciTech Connect

    Kameswara Rao, N.; Lambert, David L.; McArthur, Barbara; Garcia-Hernandez, D. A.; Woolf, Vincent M. E-mail: dll@astro.as.utexas.edu

    2012-11-20

    The remarkable hot R Coronae Borealis (RCB) star DY Cen is revealed to be the first and only binary system to be found among the RCB stars and their likely relatives, including the extreme helium stars and the hydrogen-deficient carbon stars. Radial velocity determinations from 1982 to 2010 have shown that DY Cen is a single-lined spectroscopic binary in an eccentric orbit with a period of 39.67 days. It is also one of the hottest and most H-rich member of the class of RCB stars. The system may have evolved from a common envelope to its current form.

  3. ABSOLUTE PROPERTIES OF THE ECLIPSING BINARY STAR BF DRACONIS

    SciTech Connect

    Sandberg Lacy, Claud H.; Torres, Guillermo; Fekel, Francis C.; Sabby, Jeffrey A.; Claret, Antonio E-mail: gtorres@cfa.harvard.edu E-mail: jsabby@siue.edu

    2012-06-15

    BF Dra is now known to be an eccentric double-lined F6+F6 binary star with relatively deep (0.7 mag) partial eclipses. Previous studies of the system are improved with 7494 differential photometric observations from the URSA WebScope and 9700 from the NFO WebScope, 106 high-resolution spectroscopic observations from the Tennessee State University 2 m automatic spectroscopic telescope and the 1 m coude-feed spectrometer at Kitt Peak National Observatory, and 31 accurate radial velocities from the CfA. Very accurate (better than 0.6%) masses and radii are determined from analysis of the two new light curves and four radial velocity curves. Theoretical models match the absolute properties of the stars at an age of about 2.72 Gyr and [Fe/H] = -0.17, and tidal theory correctly confirms that the orbit should still be eccentric. Our observations of BF Dra constrain the convective core overshooting parameter to be larger than about 0.13 H{sub p}. We find, however, that standard tidal theory is unable to match the observed slow rotation rates of the components' surface layers.

  4. Very wide binary stars as the primary source of stellar collisions in the galaxy

    SciTech Connect

    Kaib, Nathan A.; Raymond, Sean N.

    2014-02-20

    We present numerical simulations modeling the orbital evolution of very wide binaries, pairs of stars separated by over ∼10{sup 3} AU. Due to perturbations from other passing stars and the Milky Way's tide, the orbits of very wide binary stars occasionally become extremely eccentric, which forces close encounters between the companion stars. We show that this process causes a stellar collision between very wide binary companion stars once every 1000-7500 yr on average in the Milky Way. One of the main uncertainties in this collision rate is the amount of energy dissipated by dynamic tides during close (but not collisional) periastron passages. This dissipation presents a dynamical barrier to stellar collisions and can instead transform very wide binaries into close or contact binaries. However, for any plausible tidal dissipation model, very wide binary stars are an unrealized, and potentially the dominant, source of stellar collisions in our Galaxy. Such collisions should occur throughout the thin disk of the Milky Way. Stellar collisions within very wide binaries should yield a small population of single, Li-depleted, rapidly rotating massive stars.

  5. Binary star formation: gravitational fragmentation followed by capture

    NASA Astrophysics Data System (ADS)

    Turner, J. A.; Chapman, S. J.; Bhattal, A. S.; Disney, M. J.; Pongracic, H.; Whitworth, A. P.

    1995-11-01

    We describe in detail one of a sequence of numerical simulations which realize the mechanism of binary star formation proposed by Pringle. In these simulations, collisions between stable molecular cloud clumps produce dense shocked layers, which cool radiatively and fragment gravitationally. The resulting fragments then condense to form protostellar discs, which at the same time fall together and, as a result of tidal and viscous interactions, capture one another to form binary systems. We refer to this mechanism as shock-induced gravitational fragmentation followed by capture, or SGF+C. When the initial clumps are sufficiently massive and/or the Mach number of the collision is sufficiently high, a large number (>~10) of protostellar discs is produced; under these circumstances, the layer fragments first into filaments, and then into beads along the filaments. The marriage of two protostellar discs in this way is `arranged' in the sense that the protostellar discs involved do not form independently. First, they both condense out of the same layer, and probably also out of the same filament within this layer; this significantly increases the likelihood of them interacting dynamically. Secondly, there tends to be alignment between the orbital and spin angular momenta of the interacting protostellar discs, reflecting the fact that these angular momenta derive mainly from the systematic global angular momentum of the off-axis collision which produced the layer; this alignment of the various angular momenta pre-disposes the discs to very dissipative interactions, thereby increasing the probability of producing a strongly bound, long-lasting union. It is a marriage because the binary orbit stabilizes itself rather quickly. Any subsequent orbit evolution, as the protostellar discs `mop up' the surrounding residual gas and interact tidally, tends to harden the orbit. Therefore, as long as a third body does not intervene, the union is binding. Even if a third body does

  6. Evidence for prolonged main sequence stellar evolution of F stars in close binaries

    NASA Astrophysics Data System (ADS)

    Suchkov, A. A.

    2001-04-01

    Binary F stars exhibit large brightness anomaly, which is defined here as the difference between the absolute magnitude from the \\mboxuvby photometry and the actual absolute magnitude of the star. We have found that the anomaly inversely correlates with the binary components separation. There is evidence that the correlation reflects actual population differences between close and wide binary pairs, in which case it indicates that the anomaly is somehow associated with the interaction of binary's components. The anomaly has also been found to correlate with both kinematics and metallicity. The sense of the correlations implies that the anomaly increases as the star evolves, suggesting a peculiar evolution of a primary F star in a tight binary pair. This conclusion has further been supported by the study of the age-velocity relation (AVR) of F stars that are cataloged in the HIPPARCOS as single. Among these stars, those with brightness anomaly were previously shown to be most likely unidentified close binaries. We have found that the AVR of these binary candidates is different from that of the ``truly single'' F stars. The discrepancy between the two AVRs indicates that the putative binaries are, on average, older than similar normal single F stars at the same effective temperature and luminosity, which is consistent with the inferred peculiar evolution in close binaries. It appears that this peculiarity is caused by the impact of the components interaction in a tight pair on stellar evolution, which results in the prolonged main sequence lifetime of the primary F star. Based on the data from the Hipparcos astrometry satellite (European Space Agency).

  7. FM stars II: a Fourier view of pulsating binary stars - determining binary orbital parameters photometrically for highly eccentric cases

    NASA Astrophysics Data System (ADS)

    Shibahashi, Hiromoto; Kurtz, Donald W.; Murphy, Simon J.

    2015-07-01

    Continuous and precise space-based photometry has made it possible to measure the orbital frequency modulation of pulsating stars in binary systems with extremely high precision over long time spans. Frequency modulation caused by binary orbital motion manifests itself as a multiplet with equal spacing of the orbital frequency in the Fourier transform. The amplitudes and phases of the peaks in these multiplets reflect the orbital properties, hence the orbital parameters can be extracted by analysing such precise photometric data alone. We derive analytically the theoretical relations between the multiplet properties and the orbital parameters, and present a method for determining these parameters, including the eccentricity and the argument of periapsis, from a quintuplet or a higher order multiplet. This is achievable with the photometry alone, without spectroscopic radial velocity measurements. We apply this method to Kepler mission data of KIC 8264492, KIC 9651065, and KIC 10990452, each of which is shown to have an eccentricity exceeding 0.5. Radial velocity curves are also derived from the Kepler photometric data. We demonstrate that the results are in good agreement with those obtained by another technique based on the analysis of the pulsation phases.

  8. Constraining the neutron star equation of state with gravitational wave signals from coalescing binary neutron stars

    NASA Astrophysics Data System (ADS)

    Agathos, M.; Meidam, J.; Del Pozzo, W.; Li, T. G. F.; Tompitak, M.; Veitch, J.; Vitale, S.; Van Den Broeck, C.

    2015-07-01

    Recently exploratory studies were performed on the possibility of constraining the neutron star equation of state (EOS) using signals from coalescing binary neutron stars, or neutron star-black hole systems, as they will be seen in upcoming advanced gravitational wave detectors such as Advanced LIGO and Advanced Virgo. In particular, it was estimated to what extent the combined information from multiple detections would enable one to distinguish between different equations of state through hypothesis ranking or parameter estimation. Under the assumption of zero neutron star spins both in signals and in template waveforms and considering tidal effects to 1 post-Newtonian (1PN) order, it was found that O (20 ) sources would suffice to distinguish between a stiff, moderate, and soft equation of state. Here we revisit these results, this time including neutron star tidal effects to the highest order currently known, termination of gravitational waveforms at the contact frequency, neutron star spins, and the resulting quadrupole-monopole interaction. We also take the masses of neutron stars in simulated sources to be distributed according to a relatively strongly peaked Gaussian, as hinted at by observations, but without assuming that the data analyst will necessarily have accurate knowledge of this distribution for use as a mass prior. We find that especially the effect of the latter is dramatic, necessitating many more detections to distinguish between different EOSs and causing systematic biases in parameter estimation, on top of biases due to imperfect understanding of the signal model pointed out in earlier work. This would get mitigated if reliable prior information about the mass distribution could be folded into the analyses.

  9. Photometric and Spectroscopic Analysis for the Determination of Physical Parameters of an Eclipsing Binary Star System

    NASA Astrophysics Data System (ADS)

    Reid, Piper

    2013-01-01

    A binary star system is a pair of stars that are bound together by gravity. Most of the stars that we see in the night sky are members of multiple star systems. A system of stars where one star passes in front of the other (as observed from Earth) on a periodic basis is called an eclipsing binary. Eclipsing binaries can have very short rotational periods and in all cases these pairs of stars are so far away that they can only be resolved from Earth as a single point of light. The interaction of the two stars serves to produce physical phenomena that can be observed and used to study stellar properties. By careful data collection and analysis is it possible for an amateur astronomer using commercial, low cost equipment (including a home built spectroscope) to gather photometric (brightness versus time) and spectroscopic (brightness versus wavelength) data, analyze the data, and calculate the physical properties of a binary star system? Using a CCD camera, tracking mount and telescope photometric data of BB Pegasi was collected and a light curve produced. 57 Cygni was also studied using a spectroscope, tracking mount and telescope to prove that Doppler shift of Hydrogen Balmer absorption lines can be used to determine radial velocity. The orbital period, orbital velocity, radius of each star, separation of the two stars and mass of each star was calculated for the eclipsing binary BB Pegasi using photometric and spectroscopic data and Kepler’s 3rd Law. These data were then compared to published data. By careful use of consumer grade astronomical equipment it is possible for an amateur astronomer to determine an array of physical parameters of a distant binary star system from a suburban setting.

  10. Kepler Eclipsing Binary Stars. I. Catalog and Principal Characterization of 1879 Eclipsing Binaries in the First Data Release

    NASA Astrophysics Data System (ADS)

    Prša, Andrej; Batalha, Natalie; Slawson, Robert W.; Doyle, Laurance R.; Welsh, William F.; Orosz, Jerome A.; Seager, Sara; Rucker, Michael; Mjaseth, Kimberly; Engle, Scott G.; Conroy, Kyle; Jenkins, Jon; Caldwell, Douglas; Koch, David; Borucki, William

    2011-03-01

    The Kepler space mission is devoted to finding Earth-size planets orbiting other stars in their habitable zones. Its large, 105 deg2 field of view features over 156,000 stars that are observed continuously to detect and characterize planet transits. Yet, this high-precision instrument holds great promise for other types of objects as well. Here we present a comprehensive catalog of eclipsing binary stars observed by Kepler in the first 44 days of operation, the data being publicly available through MAST as of 2010 June 15. The catalog contains 1879 unique objects. For each object, we provide its Kepler ID (KID), ephemeris (BJD0, P 0), morphology type, physical parameters (T eff, log g, E(B - V)), the estimate of third light contamination (crowding), and principal parameters (T 2/T 1, q, fillout factor, and sin i for overcontacts, and T 2/T 1, (R 1 + R 2)/a, esin ω, ecos ω, and sin i for detached binaries). We present statistics based on the determined periods and measure the average occurrence rate of eclipsing binaries to be ~1.2% across the Kepler field. We further discuss the distribution of binaries as a function of galactic latitude and thoroughly explain the application of artificial intelligence to obtain principal parameters in a matter of seconds for the whole sample. The catalog was envisioned to serve as a bridge between the now public Kepler data and the scientific community interested in eclipsing binary stars.

  11. Formation of the widest binary stars from dynamical unfolding of triple systems.

    PubMed

    Reipurth, Bo; Mikkola, Seppo

    2012-12-13

    The formation of very wide binary systems, such as the α Centauri system with Proxima (also known as α Centauri C) separated from α Centauri (which itself is a close binary A/B) by 15,000 astronomical units (1 AU is the distance from Earth to the Sun), challenges current theories of star formation, because their separation can exceed the typical size of a collapsing cloud core. Various hypotheses have been proposed to overcome this problem, including the suggestion that ultrawide binaries result from the dissolution of a star cluster--when a cluster star gravitationally captures another, distant, cluster star. Recent observations have shown that very wide binaries are frequently members of triple systems and that close binaries often have a distant third companion. Here we report N-body simulations of the dynamical evolution of newborn triple systems still embedded in their nascent cloud cores that match observations of very wide systems. We find that although the triple systems are born very compact--and therefore initially are more protected against disruption by passing stars--they can develop extreme hierarchical architectures on timescales of millions of years as one component is dynamically scattered into a very distant orbit. The energy of ejection comes from shrinking the orbits of the other two stars, often making them look from a distance like a single star. Such loosely bound triple systems will therefore appear to be very wide binaries. PMID:23222523

  12. Formation of the widest binary stars from dynamical unfolding of triple systems

    NASA Astrophysics Data System (ADS)

    Reipurth, Bo; Mikkola, Seppo

    2012-12-01

    The formation of very wide binary systems, such as the α Centauri system with Proxima (also known as α Centauri C) separated from α Centauri (which itself is a close binary A/B) by 15,000 astronomical units (1 AU is the distance from Earth to the Sun), challenges current theories of star formation, because their separation can exceed the typical size of a collapsing cloud core. Various hypotheses have been proposed to overcome this problem, including the suggestion that ultrawide binaries result from the dissolution of a star cluster--when a cluster star gravitationally captures another, distant, cluster star. Recent observations have shown that very wide binaries are frequently members of triple systems and that close binaries often have a distant third companion. Here we report N-body simulations of the dynamical evolution of newborn triple systems still embedded in their nascent cloud cores that match observations of very wide systems. We find that although the triple systems are born very compact--and therefore initially are more protected against disruption by passing stars--they can develop extreme hierarchical architectures on timescales of millions of years as one component is dynamically scattered into a very distant orbit. The energy of ejection comes from shrinking the orbits of the other two stars, often making them look from a distance like a single star. Such loosely bound triple systems will therefore appear to be very wide binaries.

  13. Compact Binary Mergers as Multimessenger Sources of Gravitational Waves

    NASA Astrophysics Data System (ADS)

    Shapiro, Stuart

    2015-04-01

    On the centennial anniversary of Einstein's theory of general relativity, we are on the verge of directly detecting one of its most remarkable predictions - gravitational waves (GWs). The inspiral and merger of compact binaries - binaries with black hole, neutron star or white dwarf companions - are among the most promising sources of GWs. Many of these sources are likely to generate observable electromagnetic (EM) and/or neutrino counterparts to the GWs, constituting a major advance in multimessenger astronomy. By way of illustration, we describe recent magnetohydrodynamic simulations in general relativity (GRMHD) that show how black hole-neutron star mergers can launch jets, lending support to the idea that such mergers could be the engines that power short-hard gamma-ray bursts. We also discuss other recent GRMHD simulations that show how an inspiraling, supermassive binary black hole in a galaxy core stirs and accretes magnetized plasma that orbits the holes in a circumbinary disk. This process can generate ``precursor'' and ``aftermath'' EM radiation with respect to the peak GW emission at merger. Computer-generated movies highlighting some of these simulations will be shown. We gratefully acknowledge support from NSF Grant PHY-1300903 and NASA Grant NNX13AH44G at the University of Illinois at Urbana-Champaign.

  14. Radial Velocity Solution for Kepler Eclipsing Binary Stars from SDSS APOGEE

    NASA Astrophysics Data System (ADS)

    Clark, Joni Marie; Mason, Paul A.; Rawls, Meredith L.; Jackiewicz, Jason; SDSS NMSU FAST

    2016-06-01

    Proper characterization of binary stars is provided by high quality spectra combined with light curves allowing for precise determination of stellar masses, radii, and effective temperatures along with binary semi-major axes and eccentricities. A program to extract radial velocities of Kepler eclipsing binaries observed by SDSS APOGEE is presented. We combine the quality light curves from the Kepler telescope with high precision radial velocity measurements from SDSS APOGEE in order to characterize the binary and stellar components. We report on the first results of this program on three eclipsing binaries, KIC 6864859, KIC 6698670, and KIC 7121885.

  15. New Positions and/or Orbits for Binary Stars Observed at the SOR

    NASA Astrophysics Data System (ADS)

    Drummond, J.

    2012-09-01

    Many binary stars observed at the SOR during adaptive optics calibration on the 3.5 m telescope turn out to be 'off orbit', especially those from the 'All Binaries' spreadsheet (as opposed to the 'Calibration Binaries' spreadsheet) that I made available at the AMOS Conference last year. In some cases new companions have been discovered. New positions and relative magnitudes will be reported, and for some, new orbits. At the separations available through AO, most binaries show motion, making the best calibrators those with derived orbits. The conclusion is that many new binary discoveries can be made by simply turning on AO in the IR.

  16. In what sense a neutron star-black hole binary is the holy grail for testing gravity?

    NASA Astrophysics Data System (ADS)

    Bagchi, Manjari; Torres, Diego F.

    2014-08-01

    Pulsars in binary systems have been very successful to test the validity of general relativity in the strong field regime [1-4]. So far, such binaries include neutron star-white dwarf (NS-WD) and neutron star-neutron star (NS-NS) systems. It is commonly believed that a neutron star-black hole (NS-BH) binary will be much superior for this purpose. But in what sense is this true? Does it apply to all possible deviations?

  17. In what sense a neutron star-black hole binary is the holy grail for testing gravity?

    SciTech Connect

    Bagchi, Manjari; Torres, Diego F. E-mail: dtorres@ieec.uab.es

    2014-08-01

    Pulsars in binary systems have been very successful to test the validity of general relativity in the strong field regime [1-4]. So far, such binaries include neutron star-white dwarf (NS-WD) and neutron star-neutron star (NS-NS) systems. It is commonly believed that a neutron star-black hole (NS-BH) binary will be much superior for this purpose. But in what sense is this true? Does it apply to all possible deviations?.

  18. Eclipsing Binary Stars in the OGLE-III Fields of the Small Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Pawlak, M.; Graczyk, D.; Soszyński, I.; Pietrukowicz, P.; Poleski, R.; Udalski, A.; Szymański, M. K.; Kubiak, M.; Pietrzyński, G.; Wyrzykowski, Ł.; Ulaczyk, K.; Kozłowski, S.; Skowron, J.

    2013-09-01

    We present a large sample of eclipsing binary stars detected in the Small Magellanic Cloud fields covering about 14 square degrees that have been monitored for eight years during the third phase of the OGLE survey. This is the largest set of such variables containing 6138 objects, of which 777 are contact and 5361 non-contact binaries. The estimated completeness of this sample is around 82%. We analyze the statistical properties of the sample and present selected interesting objects: 32 systems having eccentric orbit with visible apsidal motion, one Transient Eclipsing Binary, ten RS CVn type stars, 22 still unexplained Double-Periodic Variable stars, and 15 candidates for doubly eclipsing quadruple systems. Based on the OGLE-III proper motions, we classified 47 binaries from our sample as foreground Galactic stars. We also list candidates suitable for the SMC distance determination.

  19. VizieR Online Data Catalog: Binary star discoveries in the URAT1 catalog (Nicholson, 2015)

    NASA Astrophysics Data System (ADS)

    Nicholson, M. P.

    2015-05-01

    Astrometric and photometric data are presented for 9450 common proper motion binary star system using results from the first U.S. Naval Observatory Astrometric Robotic Telescope Catalog (URAT1) (1 data file).

  20. RADIAL VELOCITIES OF GALACTIC O-TYPE STARS. II. SINGLE-LINED SPECTROSCOPIC BINARIES

    SciTech Connect

    Williams, S. J.; Gies, D. R.; Hillwig, T. C.; McSwain, M. V.; Huang, W. E-mail: gies@chara.gsu.edu E-mail: mcswain@lehigh.edu

    2013-02-01

    We report on new radial velocity measurements of massive stars that are either suspected binaries or lacking prior observations. This is part of a survey to identify and characterize spectroscopic binaries among O-type stars with the goal of comparing the binary fraction of field and runaway stars with those in clusters and associations. We present orbits for HDE 308813, HD 152147, HD 164536, BD-16 Degree-Sign 4826, and HDE 229232, Galactic O-type stars exhibiting single-lined spectroscopic variation. By fitting model spectra to our observed spectra, we obtain estimates for effective temperature, surface gravity, and rotational velocity. We compute orbital periods and velocity semiamplitudes for each system and note the lack of photometric variation for any system. These binaries probably appear single-lined because the companions are faint and because their orbital Doppler shifts are small compared to the width of the rotationally broadened lines of the primary.

  1. Identification and Spectral Classification of Red Dwarf Common Proper Motion Binary Stars Part 2

    NASA Astrophysics Data System (ADS)

    Chivers, James

    2014-10-01

    The position angle, separation, and spectral class of 1042 common proper motion red dwarf binary stars are reported based on data-mining the Sloan Digital Sky Survey Data Release 10. 727 of these are new discoveries.

  2. AM CVn Stars: Structure and Evolution of Ultra-Short Period Interacting Binaries

    NASA Technical Reports Server (NTRS)

    Froning, Cynthia

    2005-01-01

    This is the final report of a FUSE program to study the physics of accretion and outflows in ultra-compact, helium dominated, disk-accreting binaries. With FUSE, we observed the AM CVn binary V803 Cen, which is one of only two AM CVn systems observed by FUSE to date. V803 Cen is a short-period interacting binary in which a hydrogen-deficient white dwarf transfers mass to another white dwarf via a hot, steady-state accretion disk. Unlike other cataclysmic variables (CVs), AM CVn stars have undergone double common envelope evolution (one for each white dwarf in the binary) and so probe an alternate route of evolution in binary stars. Our goals in this project were to investigate how the structure of the accretion disk and the link between the disk and wind outflows are affected by the absence of hydrogen in the system and by the compact size of the binary and the accretion disk.

  3. Wolf-Rayet stars in the Small Magellanic Cloud. II. Analysis of the binaries

    NASA Astrophysics Data System (ADS)

    Shenar, T.; Hainich, R.; Todt, H.; Sander, A.; Hamann, W.-R.; Moffat, A. F. J.; Eldridge, J. J.; Pablo, H.; Oskinova, L. M.; Richardson, N. D.

    2016-06-01

    Context. Massive Wolf-Rayet (WR) stars are evolved massive stars (Mi ≳ 20 M⊙) characterized by strong mass-loss. Hypothetically, they can form either as single stars or as mass donors in close binaries. About 40% of all known WR stars are confirmed binaries, raising the question as to the impact of binarity on the WR population. Studying WR binaries is crucial in this context, and furthermore enable one to reliably derive the elusive masses of their components, making them indispensable for the study of massive stars. Aims: By performing a spectral analysis of all multiple WR systems in the Small Magellanic Cloud (SMC), we obtain the full set of stellar parameters for each individual component. Mass-luminosity relations are tested, and the importance of the binary evolution channel is assessed. Methods: The spectral analysis is performed with the Potsdam Wolf-Rayet (PoWR) model atmosphere code by superimposing model spectra that correspond to each component. Evolutionary channels are constrained using the Binary Population and Spectral Synthesis (BPASS) evolution tool. Results: Significant hydrogen mass fractions (0.1 stars in our sample are not chemically homogeneous. The WR component in the binary AB 6 is found to be very luminous (log L ≈ 6.3 [L⊙]) given its orbital mass (≈10 M⊙), presumably because of observational contamination by a third component. Evolutionary paths derived for our objects suggest that Roche lobe overflow had occurred in most systems, affecting their evolution. However, the implied initial masses (≳60 M⊙) are large enough for the primaries to have entered the WR phase, regardless of binary interaction. Conclusions: Together with the results for the putatively single SMC WR stars, our study suggests that the binary evolution channel does not dominate the formation of WR stars at

  4. Loud and Bright: Gravitational and possible electromagnetic signals induced by binary neutron star mergers

    NASA Astrophysics Data System (ADS)

    Palenzuela, Carlos; Lehner, Luis; Ponce, Marcelo; Thompson, Chris; Liebling, Steve; Neilsen, Dave; Hirschmann, Eric; Anderson, Matt; Motl, Patrick

    2013-04-01

    Our main goal is to investigate how the strongly gravitating and highly dynamical behavior of magnetized binary neutron stars can affect the plasma in the magnetosphere in such a way that powerful electromagnetic emissions can be induced, as well as stressing its connection with gravitational waves produced by the system. Such phenomena is a natural candidate for bright (EM) and loud (GW) emissions, as pulsars are strong electromagnetic emitters on one hand, and merging binary neutron stars are powerful sources of gravitational radiation.

  5. Binary star formation and mass outflows: MHD nested grid simulation

    NASA Astrophysics Data System (ADS)

    Machida, M. N.; Tomisaka, K.; Matsumoto, T.

    2004-08-01

    We study the binary star formation process from a rotating magnetized molecular cloud. We assume an isothermal cylindrical cloud in hydrostatic balance whose rotation axis and the direction of global magnetic field lines are both identical, and parallel to the cylinder axis. We added axisymmetric and non-axisymmetric density perturbations to the initial state and followed the subsequent evolutions. The evolution is characterized by three parameters: the amplitude of the non-axisymmetric perturbations, the rotation speed, and the magnetic field strength. As a result, it is found that non-axisymmetry hardly evolves in the early phase, but begins to grow after the gas contracts and forms a thin disk. There are two types of fragmentation: fragmentation from a ring and that from a bar. Thin adiabatic cores fragments if a thickness is smaller than 1/4 of the radius. For the fragments to survive, they should be formed in a heavily elongated barred core or a flat round disk. In the models showing fragmentation, outflows from respective fragments are found as well as those driven by the rotating bar or the disk.

  6. Fragmentation of Molecular Clouds and Binary Star Formation

    NASA Astrophysics Data System (ADS)

    Machida, Masahiro N.; Tomisaka, Kohji; Matsumoto, Tomoaki

    Using three-dimensional MHD nested-grid simulations we study the binary star formation process paying particular attention to the fragmentation of a rotating magnetized molecular cloud. We assume an isothermal rotating and magnetized cylindrical cloud in hydrostatic balance. Non-axisymmetric as well as axisymmetric perturbations are added to the initial state and the subsequent evolutions are studied. The evolution is characterized by three parameters: the amplitude of the non-axisymmetric perturbations the rotation speed and the magnetic field strength. As a result it is found that non-axisymmetry hardly evolves in the early phase but begins to grow after the gas contracts and forms a thin disk. Disk formation is strongly promoted by the rotation speed and the magnetic field strength. There are two types of fragmentation: fragmentation from a ring and that from a bar. Thin adiabatic cores fragments if a thickness is smaller than 1/4 of the radius. For the fragments to survive they should be formed in a heavily elongated barred core or a flat round disk. In the models showing fragmentation outflows from respective fragments are found as well as those driven by the rotating bar or the disk

  7. Differential Rotation of Close Binary Stars: Application to HR 1099

    NASA Astrophysics Data System (ADS)

    Petit, P.; Donati, J.-F.; Wade, G. A.; Landstreet, J. D.; Oliveira, J. M.; Shorlin, S. L. S.; Sigut, T. A. A.; Collier Cameron, A.

    We propose a new method for estimating differential rotation in binary stars, for which only moderate to poor phase coverage can be obtained (rotation period of order of a few days), preventing the use of conventional cross-correlation methods. Assuming a solar-like differential rotation law with two independent parameters (equatorial rotation rate φeq and rotational shear between pole and equator dφ), we reconstruct Doppler images for different values of the two parameters, and derive the optimal φeq, dφ and associated error bars from the corresponding 2 ° map. Simulations show that φeq and dφ can be recovered with good accuracy, even if the phase coverage per rotation cycle is poor, provided the total data set is long enough. From observations of the HR 1099 K1 subgiant secured in 1998, 1999 and 2000, we obtain that the equator rotates faster than the pole with a rotational shear about 3 times smaller than solar.

  8. Modelling of the Semi-Detached Binary Star WZ Corvi

    NASA Astrophysics Data System (ADS)

    Virnina, N. A.; Zola, S.; Krajci, T.

    We present results from modeling of multicolor light curves of the semi-detached, algol- type binary system WZ Corvi. We analyzed V R data gathered in 2010 and new BV RcIc observations collected in 2012. Two models for WZ Crv are considered: the first was derived under the assumption that the temperature of the primary component, having the dominant contribution to total system light, corresponds to spectral type F7, and the second model, in which the temperature of the secondary was estimated from the colors observed at the at bottom of the primary minimum. The new set of observations shows almost no difference in maxima heights, obvious in the earlier, 2010 data. However, primary minimum in V and R is deeper than in the 2010 light curve. We explain the variable shape of the system light curve as spot(s) present on primary or secondary component(s) due to their magnetic activity. Based on the derived solutions, we calculate relative physical (assuming the primary component to be a Main Sequence star) parameters of WZ Crv for both models.

  9. Absolute properties of the eclipsing binary star AP Andromedae

    SciTech Connect

    Sandberg Lacy, Claud H.; Torres, Guillermo; Fekel, Francis C.; Muterspaugh, Matthew W. E-mail: gtorres@cfa.harvard.edu E-mail: matthew1@coe.tsuniv.edu

    2014-06-01

    AP And is a well-detached F5 eclipsing binary star for which only a very limited amount of information was available before this publication. We have obtained very extensive measurements of the light curve (19,097 differential V magnitude observations) and a radial velocity curve (83 spectroscopic observations) which allow us to fit orbits and determine the absolute properties of the components very accurately: masses of 1.277 ± 0.004 and 1.251 ± 0.004 M {sub ☉}, radii of 1.233 ± 0.006 and 1.1953 ± 0.005 R {sub ☉}, and temperatures of 6565 ± 150 K and 6495 ± 150 K. The distance to the system is about 400 ± 30 pc. Comparison with the theoretical properties of the stellar evolutionary models of the Yonsei-Yale series of Yi et al. shows good agreement between the observations and the theory at an age of about 500 Myr and a slightly sub-solar metallicity.

  10. Binary star detectability in Kepler data from phase modulation of different types of oscillations

    NASA Astrophysics Data System (ADS)

    Compton, D. L.; Bedding, T. R.; Murphy, S. J.; Stello, D.

    2016-09-01

    Detecting binary stars in photometric time series is traditionally done by measuring eclipses. This requires the orbital plane to be aligned with the observer. A new method without that requirement uses stellar oscillations to measure delays in the light arrival time and has been successfully applied to δ Scuti stars. However, application to other types of stars has not been explored. To investigate this, we simulated light curves with a range of input parameters. We find a correlation between the signal to noise of the pulsation modes and the time delay required to detect binary motion. The detectability of the binarity in the simulations and in real, Kepler data show strong agreement, hence, we describe the factors that have prevented this method from discovering binary companions to stars belonging to various classes of pulsating stars.