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in subjects: "Binary Stars"

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Eclipsing binary stars in the Large and Small Magellanic Clouds from the MACHO project: The Sample

We present a new sample of 4634 eclipsing binary stars in the Large Magellanic Cloud (LMC), expanding on a previous sample of 611 objects and a new sample of 1509 eclipsing binary stars in the Small Magellanic Cloud (SMC), that were identified in the light curve database of the MACHO project. We perform a cross correlation with the OGLE-II LMC sample, finding 1236 matches. A cross correlation with the OGLE-II SMC sample finds 698 matches. We then compare the LMC subsamples corresponding to cent… more

Date: March 29, 2007

Creator: Faccioli, L.; Alcock, C.; Cook, K.; Prochter, G.; Protopapas, P. & Syphers, D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Post Main Sequence Orbital Circularization of Binary Stars in the Large and Small Magellanic Clouds.

We present results from a study of the orbits of eclipsing binary stars (EBs) in the Magellanic Clouds. The samples comprise 4510 EBs found in the Large Magellanic Cloud (LMC) by the MACHO project, 2474 LMC EBs found by the OGLE-II project (of which 1182 are also in the MACHO sample), 1380 in the Small Magellanic Cloud (SMC) found by the MACHO project, and 1317 SMC EBs found by the OGLE-II project (of which 677 are also in the MACHO sample); we also consider the EROS sample of 79 EBs in the bar… more

Date: November 20, 2007

Creator: Faccioli, L.; Alcock, C. & Cook, K.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Binary neutron star GRB model

In this paper we present the preliminary results of a model for the production of gamma-ray bursts (GRBs) through the compressional heating of binary neutron stars near their last stable orbit prior to merger. Recent numerical studies of the general relativistic (GR) hydrodynamics in three spatial dimensions of close neutron star binaries (NSBs) have uncovered evidence for the compression and heating of the individual neutron stars (NSs) prior to merger. This effect will have significant effect… more

Date: November 11, 1997

Creator: Wilson, J. R.; Salmonson, J. D. & Mathews, G. J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Molecular Design of Branched and Binary Molecules at Ordered Interfaces

This study examined five different branched molecular architectures to discern the effect of design on the ability of molecules to form ordered structures at interfaces. Photochromic monodendrons formed kinked packing structures at the air-water interface due to the cross-sectional area mismatch created by varying number of alkyl tails and the hydrophilic polar head group. The lower generations formed orthorhombic unit cell with long range ordering despite the alkyl tails tilted to a large degr… more

Date: December 27, 2005

Creator: Genson, Kirsten Larson

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department

open access

The Formation of Contact and Very Close Binaries

We explore the possibility that all close binaries, i.e. those with periods {approx}< 3 d, including contact (W UMa) binaries, are produced from initially wider binaries (periods of say 10's of days) by the action of a triple companion through the medium of Kozai Cycles with Tidal Friction (KCTF).

Date: August 10, 2007

Creator: Kisseleva-Eggleton, L & Eggleton, P P

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Measuring the mass of a pre-main sequence binary star through the orbit of TWA5A

We present the results of a five year monitoring campaign of the close binary TWA 5Aab in the TW Hydrae association, using speckle and adaptive optics on the W.M. Keck 10 m telescopes. These measurements were taken as part of our ongoing monitoring of pre-main sequence (PMS) binaries in an effort to increase the number of dynamically determined PMS masses and thereby calibrate the theoretical PMS evolutionary tracks. Our observations have allowed us to obtain the first determination of this sys… more

Date: January 18, 2007

Creator: Konopacky, Q; Ghez, A; Duchene, G; McCabe, C & Macintosh, B

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Proper motion with HST: Searching for high-velocity stars in the core of the globular cluster 47 Tucanae

Binary stars play an essential role during the late phases of the dynamical evolution of a globular cluster. They transfer energy to passing stars and so can strongly influence the cluster evolution, enough to delay, halt, and even reverse core collapse. Hard binaries are known to exist in cluster cores, e.g., in the form of millisecond pulsars (about half of the millisecond pulsars observed in 47 Tucanae are such hard binaries). The presence of hard binaries may also be revealed by searching f… more

Date: February 13, 1996

Creator: Meylan, G.; Minniti, D.; Pryor, C.; Tinney, C.G.; Phinney, E.S. & Sams, B.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

ORFEUS and EUVE observations of AM herculis

Far-UV spectra of AM Her in a high optical state were obtained in 1993 September with the University of California, Berkeley (UCB) spectrometer aboard the ORFEUS telescope. The UCB spectrometer has a spectral resolution {lambda}/{Delta}{lambda} 3000 and covers the 390-1170 {Angstrom} bandpass, but interstellar absorption leaves no detectable -flux below the Lyman limit. Spectra of AM Her were acquired during the intervals 04:19:40-04:36:26 UT on September 16 and 08:34:03-09:09:06 UT on Septembe… more

Date: April 6, 1995

Creator: Mauche, C.W.; Paerels, F.B.S. & Raymond, J.C.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

The DBV stars: Progress and problems

The DB white dwarfs comprise the majority of the 20% or so of non-DA white dwarfs, and have effective temperatures between 11,000 K and 30,000 K. The hottest DBs define the cool end of the so called ``DB gap`` that lies between 30,000 K and 45,000 K; in this region, no helium atmosphere white dwarf is known. The existence of this gap presents a great puzzle concerning the origin and evolution of helium atmosphere white dwarfs. Asteroseismology of the DBV stars as a class will tell scientists wh… more

Date: September 1995

Creator: Bradley, P. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

The Formation of Population III Binaries from Cosmological Initial Conditions

Previous high resolution cosmological simulations predict the first stars to appear in the early universe to be very massive and to form in isolation. Here we discuss a cosmological simulation in which the central 50M{sub {circle_dot}} clump breaks up into two cores, having a mass ratio of two to one, with one fragment collapsing to densities of 10{sup -8}g cm{sup -3}. The second fragment, at a distance of {approx}800 astronomical units, is also optically thick to its own cooling radiation from… more

Date: August 26, 2010

Creator: Turk, Matthew J.; Abel, Tom; /KIPAC, Menlo Park; O'Shea, Brian W. & U., /Michigan State

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Cataclysmic Variables From the Sloan Digital Sky Survey. VI. the Sixth Year (2005)

The 28 cataclysmic variables found in 2005 in the Sloan Digital Sky Survey are presented with their coordinates, magnitudes and spectra. Five of these systems are previously known CVs (HH Cnc, SX LMi, QZ Ser, RXJ1554.2+2721 and HS1016+3412) and the rest are new discoveries. Additional spectroscopic, photometric and/or polarimetric observations of 10 systems were carried out, resulting in estimates of the orbital periods for seven of the new binaries. The 23 new CVs include one eclipsing system,… more

Date: June 15, 2007

Creator: Szkody, Paula; Henden, Arne; Mannikko, Lee; Mukadam, Anjum; Schmidt, Gary D.; Bochanski, John J. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Gamma ray burst model

We present a model for gamma ray bursts based on the compression of neutron stars in close binary systems. Our general relativistic hydrodynamiccomputer simulations of close neutron star binaries have found that as the orbit shrinks the density of the neutron stars rises. This compressional effect has been estimated to produce thermal energies in the neutron stars of the order of magnitude 10{sup 52}to 10{sup 53} ergs on a timescale of a few seconds.This is a possible source of energy for gamma… more

Date: February 17, 1998

Creator: Wilson, J. R.; Salmonson, J. D. & Mathews, G. J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

High Resolution Imaging with AEOS

The U. S. Air Force Advanced Electro-Optical System (AEOS) which includes a 941 actuator adaptive optics system on a 3.7m telescope has recently been made available for astronomical programs. Operating at a wavelength of 750 nm, the diffraction-limited angular resolution of the system is 0.04 inches; currently, the magnitude limit is V {approx} 7 mag. At the distances of nearby open clusters, diffraction-limited images should resolve companions with separations as small as 4-6 AU--comparable to… more

Date: August 27, 2001

Creator: Patience, J.; Macintosh, B. A. & Max, C. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

10 microsecond time resolution studies of Cygnus X-1

Time variability analyses have been applied to data composed of event times of X-rays emitted from the binary system Cygnus X-1 to search for unique black hole signatures. The X-ray data analyzed was collected at ten microsecond time resolution or better from two instruments, the High Energy Astrophysical Observatory (HEAO) A-1 detector and the Rossi X-ray Timing Explorer (XTE) Proportional Counter Array (PCA). HEAO A-1 and RXTE/PCA collected data from 1977--79 and from 1996 on with energy sens… more

Date: June 1, 1997

Creator: Wen, H.C.

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department

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SDSS spectroscopic survey of stars

In addition to optical photometry of unprecedented quality, the Sloan Digital Sky Survey (SDSS) is also producing a massive spectroscopic database. They discuss determination of stellar parameters, such as effective temperature, gravity and metallicity from SDSS spectra, describe correlations between kinematics and metallicity, and study their variation as a function of the position in the Galaxy. They show that stellar parameter estimates by Beers et al. show a good correlation with the positi… more

Date: January 1, 2007

Creator: Ivezic, Zeljko; Schlegel, D.; Uomoto, A.; Bond, N.; Beers, T.; Allende Prieto, C. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Evolution of Close Binary Systems

We collected data on the masses, radii, etc. of three classes of close binary stars: low-temperature contact binaries (LTCBs), near-contact binaries (NCBs), and detached close binaries (DCBs). They restrict themselves to systems where (1) both components are, at least arguably, near the Main Sequence, (2) the periods are less than a day, and (3) there is both spectroscopic and photometric analysis leading to reasonably reliable data. They discuss the possible evolutionary connections between th… more

Date: January 24, 2005

Creator: Yakut, K & Eggleton, P

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Gamma-ray bursts via pair plasma fireballs from heated neutron stars

In this paper the authors model the emission from a relativistically expanding e{sup +}e{sup {minus}} pair plasma fireball originating near the surface of a heated neutron star. This pair fireball is deposited via the annihilation of neutrino pairs emanating from the surface of the hot neutron star. The heating of neutron stars may occur in close neutron star binary systems near their last stable orbit. The authors model the relativistic expansion and subsequent emission of the plasma and find … more

Date: January 11, 2000

Creator: Salmonson, J. D.; Wilson, J. R. & Matthews, G. J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Discovery of kHz fluctuations in Centaurus X-3: Evidence for photon bubble oscillations (PBO) and turbulence in a high mass x-ray binary pulsar

The authors report the discovery of kHz fluctuations, including quasi-periodic oscillations (QPO) at {approximately}330 Hz and {approximately}760 Hz and a broadband kHz continuum in the power density spectrum of the high mass X-ray binary pulsar Centaurus X-3 (Jernigan, Klein and Arons 2000). These observations of Cen X-3 were carried out with the Rossi X-ray Timing Explorer (RXTE). The fluctuation spectrum is flat from mHz to a few Hz, then steepens to f{sup {minus}2} behavior between a few Hz… more

Date: September 1, 1999

Creator: Klein, R I; Jernigan, J G & Arons, J

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Parametrization and Classification of 20 Billion LSST Objects: Lessons from SDSS

The Large Synoptic Survey Telescope (LSST) will be a large, wide-field ground-based system designed to obtain, starting in 2015, multiple images of the sky that is visible from Cerro Pachon in Northern Chile. About 90% of the observing time will be devoted to a deep-wide-fast survey mode which will observe a 20,000 deg{sup 2} region about 1000 times during the anticipated 10 years of operations (distributed over six bands, ugrizy). Each 30-second long visit will deliver 5{sigma} depth for point… more

Date: November 10, 2011

Creator: Ivezic, Z.; /Washington U., Seattle, Astron. Dept.; Axelrod, T.; /Large Binocular Telescope, Tucson; Becker, A. C.; /Washington U., Seattle, Astron. Dept. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Case A Binary Evolution

We undertake a comparison of observed Algol-type binaries with a library of computed Case A binary evolution tracks. The library consists of 5500 binary tracks with various values of initial primary mass M{sub 10}, mass ratio q{sub 0}, and period P{sub 0}, designed to sample the phase-space of Case A binaries in the range -0.10 {le} log M{sub 10} {le} 1.7. Each binary is evolved using a standard code with the assumption that both total mass and orbital angular momentum are conserved. This code … more

Date: March 28, 2001

Creator: Nelson, C A & Eggleton, P P

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Cygnus X-3 revisited: 10 years of muon and radio observations.

The Soudan 2 deep underground tracking calorimeter has recorded cosmic ray muon tracks from the direction of the galactic x-ray binary Cygnus X-3 on most transits during the interval 1989-1998. We analyze these events in the context of previous reports of Cygnus X-3-related muon flux during major radio flares of that source. We find some evidence for excess flux during a small number of transits coincident with major radio flares. We also find an indication that these events maybe distributed a… more

Date: June 23, 1999

Creator: Allison, W. W. M.; Alner, G. J.; Ayres, D. S.; Barrett, W. L.; Bode, C.; Fields, T. H. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

An April 1991 outburst from 4U0115+63 observed by BATSE

4U0115+63 is a recurrent transient X-ray pulsar in a moderately eccentric orbit with a Be star companion, V635 Cas. Many outbursts from this system have been reported over the past twenty years; yet despite the apparent relation between optical outbursts from the companion star and subsequent X-ray transient events, the physical mechanism for the mass transfer in the system remains unclear. In this paper, the authors present the preliminary results of analysis of observations made using BATSE d… more

Date: December 1, 1993

Creator: Cominsky, L.; Roberts, M. & Finger, M. H.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

The evolutionary status of PSR 1259-63

The PSR 1259--63 system is unique in that it is the first radio pulsar found to be in a binary system with a massive main sequence companion. As such, it may be the evolutionary missing link connecting the radio pulsars to the X-ray emitting Be binaries. In this paper, we consider the conditions under which PSR 1259-63 may be the progenitor of the less eccentric, more slowly rotating X-ray Be binaries such as 4U0115+63, A0535+26, and A0538-66. Scenarios invoking the interaction of the pulsar wi… more

Date: December 1, 1993

Creator: Cominsky, L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

The Use of Weighting in Periodicity Searches in All-Sky Monitor Data: Applications to the GLAST LAT

The light curves produced by all-sky monitors, such as the Rossi X-ray Timing Explorer All-Sky Monitor and the Swift Burst Alert Telescope (BAT), generally have non-uniform error bars. In searching for periodic modulation in this type of data using power spectra it can be important to use appropriate weighting of data points to achieve the best sensitivity. It was recently demonstrated that for Swift BAT data a simple weighting scheme can actually sometimes reduce the sensitivity of the power s… more

Date: June 25, 2009

Creator: Corbet, Robin & Dubois, Richard

Item Type: Article

Partner: UNT Libraries Government Documents Department