Double Star Measurements at the Southern Sky with a 50 cm Reflector and a Fast CCD Camera in 2014

NASA Astrophysics Data System (ADS)

Anton, Rainer

2015-04-01

A Ritchey-Chrétien reflector with 50 cm aperture was used in Namibia for recordings of double stars with a fast CCD camera and a notebook computer. From superposition of "lucky images", measurements of 91 pairings in 79 double and multiple systems were obtained and compared with literature data. Occasional deviations are discussed. Some images of noteworthy systems are also presented.

The double-degenerate, super-Chandrasekhar nucleus of the planetary nebula Henize 2-428.

PubMed

Santander-García, M; Rodríguez-Gil, P; Corradi, R L M; Jones, D; Miszalski, B; Boffin, H M J; Rubio-Díez, M M; Kotze, M M

2015-03-05

The planetary nebula stage is the ultimate fate of stars with masses one to eight times that of the Sun (M(⊙)). The origin of their complex morphologies is poorly understood, although several mechanisms involving binary interaction have been proposed. In close binary systems, the orbital separation is short enough for the primary star to overfill its Roche lobe as the star expands during the asymptotic giant branch phase. The excess gas eventually forms a common envelope surrounding both stars. Drag forces then result in the envelope being ejected into a bipolar planetary nebula whose equator is coincident with the orbital plane of the system. Systems in which both stars have ejected their envelopes and are evolving towards the white dwarf stage are said to be double degenerate. Here we report that Henize 2-428 has a double-degenerate core with a combined mass of ∼1.76M(⊙), which is above the Chandrasekhar limit (the maximum mass of a stable white dwarf) of 1.4M(⊙). This, together with its short orbital period (4.2 hours), suggests that the system should merge in 700 million years, triggering a type Ia supernova event. This supports the hypothesis of the double-degenerate, super-Chandrasekhar evolutionary pathway for the formation of type Ia supernovae.

CCD Astrometric Measurements of WDS 05247+3723

NASA Astrophysics Data System (ADS)

Chasin, Mike; Adas, Matthew; Tanon, Naylynn; Boyce, Grady; Boyce, Pat

2017-07-01

Theta and rho astrometric measurements were made of the double star system WDS 05247+3723 pairs AB, AC, and CD. These measurements compared favorably with the historic data from the Washington Double Star Catalog (WDS). We also measured the AD, BC, & BD pair relative astrometry.

High-resolution spectroscopy of extremely metal-poor stars from SDSS/Segue. II. Binary fraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aoki, Wako; Suda, Takuma; Beers, Timothy C.

2015-02-01

The fraction of binary systems in various stellar populations of the Galaxy and the distribution of their orbital parameters are important but not well-determined factors in studies of star formation, stellar evolution, and Galactic chemical evolution. While observational studies have been carried out for a large sample of nearby stars, including some metal-poor Population II stars, almost no constraints on the binary nature for extremely metal-poor (EMP; [Fe/H] <−3.0) stars have yet been obtained. Here we investigate the fraction of double-lined spectroscopic binaries and carbon-enhanced metal-poor (CEMP) stars, many of which could have formed as pairs of low-mass and intermediate-massmore » stars, to estimate the lower limit of the fraction of binary systems having short periods. The estimate is based on a sample of very metal-poor stars selected from the Sloan Digital Sky Survey and observed at high spectral resolution in a previous study by Aoki et al. That survey reported 3 double-lined spectroscopic binaries and 11 CEMP stars, which we consider along with a sample of EMP stars from the literature compiled in the SAGA database. We have conducted measurements of the velocity components for stacked absorption features of different spectral lines for each double-lined spectroscopic binary. Our estimate indicates that the fraction of binary stars having orbital periods shorter than 1000 days is at least 10%, and possibly as high as 20% if the majority of CEMP stars are formed in such short-period binaries. This result suggests that the period distribution of EMP binary systems is biased toward short periods, unless the binary fraction of low-mass EMP stars is significantly higher than that of other nearby stars.« less

How bright planets became dim stars: planetary speculations in John Herschel's double star astronomy

NASA Astrophysics Data System (ADS)

Case, S.

2014-03-01

Previous research on the origins of double star astronomy in the early nineteenth century emphasized the role mathematical methods and instrumentation played in motivating early observations of these objects. The work of the British astronomer John Herschel, however, shows that questions regarding the physical nature of double stars were also important. In particular, an analysis of John Herschel's early work on double stars illustrates the way in which speculations regarding these objects were shaped by assumptions of the properties of stars themselves. For Herschel, a major consideration in double star astronomy was distinguishing between types of double stars. Optical doubles were useful in determining parallax while binary doubles were not. In practice, classification of a specific double star pair into one of these categories was based on the assumption that stars were of approximately the same luminosity and thus differences in relative brightness between stars were caused by difference in distances. Such assumptions, though ultimately abandoned, would lead Herschel in the 1830s to advance the possibility that the dim companion stars in certain double star pairs were not stars at all but in fact planets.

How bright planets became dim stars: planetary speculations in John Herschel's double star astronomy.

PubMed

Case, Stephen

2014-03-01

Previous research on the origins of double star astronomy in the early nineteenth century emphasized the role mathematical methods and instrumentation played in motivating early observations of these objects. The work of the British astronomer John Herschel, however, shows that questions regarding the physical nature of double stars were also important. In particular, an analysis of John Herschel's early work on double stars illustrates the way in which speculations regarding these objects were shaped by assumptions of the properties of stars themselves. For Herschel, a major consideration in double star astronomy was distinguishing between types of double stars. Optical doubles were useful in determining parallax while binary doubles were not. In practice, classification of a specific double star pair into one of these categories was based on the assumption that stars were of approximately the same luminosity and thus differences in relative brightness between stars were caused by difference in distances. Such assumptions, though ultimately abandoned, would lead Herschel in the 1830s to advance the possibility that the dim companion stars in certain double star pairs were not stars at all but in fact planets. Copyright © 2014 Elsevier Ltd. All rights reserved.

Hamilton Jeffers and the Double Star Catalogues

NASA Astrophysics Data System (ADS)

Tenn, Joseph S.

2013-01-01

Astronomers have long tracked double stars in efforts to find those that are gravitationally-bound binaries and then to determine their orbits. Court reporter and amateur astronomer Shelburne Wesley Burnham (1838-1921) published a massive double star catalogue containing more than 13,000 systems in 1906. The next keeper of the double stars was Lick Observatory astronomer Robert Grant Aitken (1864-1951), who produced a much larger catalogue in 1932. Aitken maintained and expanded Burnham’s records of observations on handwritten file cards, eventually turning them over to Lick Observatory astrometrist Hamilton Moore Jeffers (1893-1976). Jeffers further expanded the collection and put all the observations on punched cards. With the aid of Frances M. "Rete" Greeby (1921-2002), he made two catalogues: an Index Catalogue with basic data about each star, and a complete catalogue of observations, with one observation per punched card. He enlisted Willem van den Bos of Johannesburg to add southern stars, and they published the Index Catalogue of Visual Double Stars, 1961.0. As Jeffers approached retirement he became greatly concerned about the disposition of the catalogues. He wanted to be replaced by another "double star man," but Lick Director Albert E. Whitford (1905-2002) had the new 120-inch reflector, the world’s second largest telescope, and he wanted to pursue modern astrophysics instead. Jeffers was vociferously opposed to turning over the card files to another institution, and especially against their coming under the control of Kaj Strand of the U.S. Naval Observatory. In the end the USNO got the files and has maintained the records ever since, first under Charles Worley (1935-1997), and, since 1997, under Brian Mason. Now called the Washington Double Star Catalog (WDS), it is completely online and currently contains more than 1,000,000 measures of more than 100,000 pairs.

Double and Multiple Star Measurements at the Southern Sky with a 50cm-Cassegrain and a Fast CCD Camera in 2008

NASA Astrophysics Data System (ADS)

Anton, Rainer

2011-04-01

Using a 50cm Cassegrain in Namibia, recordings of double and multiple stars were made with a fast CCD camera and a notebook computer. From superpositions of "lucky images", measurements of 149 systems were obtained and compared with literature data. B/W and color images of some remarkable systems are also presented.

Double and Multiple Star Measurements in the Northern Sky with a 10" Newtonian and a Fast CCD Camera in 2006 through 2009

NASA Astrophysics Data System (ADS)

Anton, Rainer

2010-07-01

Using a 10" Newtonian and a fast CCD camera, recordings of double and multiple stars were made at high frame rates with a notebook computer. From superpositions of "lucky images", measurements of 139 systems were obtained and compared with literature data. B/w and color images of some noteworthy systems are also presented.

Anomalous double-mode RR Lyrae stars in the Magellanic Clouds

NASA Astrophysics Data System (ADS)

Soszyński, I.; Smolec, R.; Dziembowski, W. A.; Udalski, A.; Szymański, M. K.; Wyrzykowski, Ł.; Ulaczyk, K.; Poleski, R.; Pietrukowicz, P.; Kozłowski, S.; Skowron, D.; Skowron, J.; Mróz, P.; Pawlak, M.

2016-12-01

We report the discovery of a new subclass of double-mode RR Lyrae stars in the Large and Small Magellanic Clouds. The sample of 22 pulsating stars has been extracted from the latest edition of the Optical Gravitational Lensing Experiment collection of RR Lyrae variables in the Magellanic System. The stars pulsating simultaneously in the fundamental (F) and first-overtone (1O) modes have distinctly different properties than regular double-mode RR Lyrae variables (RRd stars). The P1O/PF period ratios of our anomalous RRd stars are within a range of 0.725-0.738, while `classical' double-mode RR Lyrae variables have period ratios in the range of 0.742-0.748. In contrast to the typical RRd stars, in the majority of the anomalous pulsators, the F-mode amplitudes are higher than the 1O-mode amplitudes. The light curves associated with the F-mode in the anomalous RRd stars show different morphology than the light curves of, both, regular RRd stars and single-mode RRab stars. Most of the anomalous double-mode stars show long-term modulations of the amplitudes (Blazhko-like effect). Translating the period ratios into the abundance parameter, Z, we find for our stars Z ∈ (0.002, 0.005) - an order of magnitude higher values than typical for RR Lyrae stars. The mass range of the RRd stars inferred from the WI versus PF diagram is (0.55-0.75) M⊙. These parameters cannot be accounted for with single star evolution assuming a Reimers-like mass-loss. Much greater mass-loss caused by interaction with other stars is postulated. We blame the peculiar pulsation properties of our stars to the parametric resonance instability of the 1O-mode to excitation of the F- and 2O-modes as with the inferred parameters of the stars 2ω1O ≈ ωF + ω2O.

The Influence of Mass Loss on the Eccentricity of Double Star Orbits

NASA Astrophysics Data System (ADS)

Docobo, J. A.; Prieto, C.; Ling, J. F.

In this comunication we study the behaviour of the eccentricity of double star orbits (visual and wide spectroscopic binaries) according to simplified laws of mass loss. Applications to the systems WDS 05245S0224 - HD 35411, WDS 05387S0236 - HD 37468 and WDS 06154S0902 - HD 43362 are included.

ScienceCast 77: Weird Planets

NASA Image and Video Library

2012-09-06

Once, astronomers thought planets couldn't form around binary stars. Now Kepler has found a whole system of planers orbiting a double star. This finding shows that planetary systems are weirder and more abundant than previously thought.

Colliding Neutron Stars as the Source of Heavy Elements

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-09-01

Where do the heavy elements the chemical elements beyond iron in our universe come from? One of the primary candidate sources is the merger of two neutron stars, but recent observations have cast doubt on this model. Can neutron-star mergers really be responsible?Elements from Collisions?Periodic table showing the origin of each chemical element. Those produced by the r-process are shaded orange and attributed to supernovae in this image; though supernovae are one proposed source of r-process elements, an alternative source is the merger of two neutron stars. [Cmglee]When a binary-neutron-star system inspirals and the two neutron stars smash into each other, a shower of neutrons are released. These neutrons are thought to bombard the surrounding atoms, rapidly producing heavy elements in what is known as r-process nucleosynthesis.So could these mergers be responsible for producing the majority of the universes heavy r-process elements? Proponents of this model argue that its supported by observations. The overall amount of heavy r-process material in the Milky Way, for instance, is consistent with the expected ejection amounts from mergers, based both on predicted merger rates for neutron stars in the galaxy, and on the observed rates of soft gamma-ray bursts (which are thought to accompany double-neutron-star mergers).Challenges from Ultra-Faint DwarfsRecently, however, r-process elements have been observed in ultra-faint dwarf satellite galaxies. This discovery raises two major challenges to the merger model for heavy-element production:When neutron stars are born during a core-collapse supernova, mass is ejected, providing the stars with asymmetric natal kicks. During the second collapse in a double-neutron-star binary, wouldnt the kick exceed the low escape velocity of an ultra-faint dwarf, ejecting the binary before it could merge and enrich the galaxy?Ultra-faint dwarfs have very old stellar populations and the observation of r-process elements in these stars requires mergers to have occurred very early in the galaxys history. Can double-neutron-star systems merge quickly enough to account for the observed chemical enrichment?Small Kicks and Fast MergersFraction of double-neutron-star systems that remain bound, vs. the magnitude of the kick they receive. A typical escape velocity for an ultra-faint dwarf is ~15 km/s; roughly 55-65% of binaries receive smaller kicks than that and wouldnt be ejected from an ultra-faint dwarf. [Beniamini et al. 2016]Led by Paz Beniamini, a team of scientists from the Racah Institute of Physics at the Hebrew University of Jerusalem has set out to answer these questions. Using the statistics of our galaxys double-neutron-star population, the team performed Monte Carlo simulations to estimate the distributions of mass ejection and kick velocities for the systems.Beniamini and collaborators find that, for typical initial separations, more than half of neutron star binaries are born with small enough kicks that they remain bound and arent ejected even from small, ultra-faint dwarf galaxies.The team also used their statistics to calculate the time until merger for the population of binaries, finding that ~90% of the double-neutron-star systems merge within 300 Myr, and around 15% merge within 100 Myr quick enough to enrich even the old population of stars.This population of systems that remain confined to the galaxy and merge rapidly can therefore explain the observations of r-process material in ultra-faint dwarf galaxies. Beniamini and collaborators work suggests that the merger of neutron stars is indeed a viable model for the production of heavy elements in our universe.CitationPaz Beniamini et al 2016 ApJ 829 L13. doi:10.3847/2041-8205/829/1/L13

Activities and Achievements of the Double Star Committee of the Socié té Astronomique de France

NASA Astrophysics Data System (ADS)

Agati, Jean-Louis; Caille, Sébastien; Debackère, André; Durand, Pierre; Losse, Florent; Manté, René; Mauroy, Florence; Mauroy, Pascal; Morlet, Guy; Pinlou, Claude; Salaman, Maurice; Soulié, Edgar; Thorel, Yvonne; Thorel, Jean-Claude

2007-08-01

In a synthesis article (see ref. below), the double star expert Paul COUTEAU put the work of French pioneers of double stars observation in the perspective of the double star work carried in the world. After Antoine Yvon VILLARCEAU and Camille FLAMMARION, one prominent pioneer of double stars was Robert JONCKHEERE (1888toiles Doubles, Maurice DURUY (1894le with a 40-cm and later a 60-cm telescope at Le Rouret (Alpes1995) had started the measurement of double stars as an amateur. He was granted permission to measure them with the 38-cm of the Paris Observatory and made an impressive number of measures during his long 2006) made double star observations for the book which was then in preparation under the title La revue des constellations. Their measures remained unpublished; but publication of the measures made by Robert SAGOT is in preparation. At about the same time, the neurology professor Jacques LE BEAU (1908toiles doubles visuelles. That book triggered the interest of more amateur astronomers for double stars and indirectly influenced the creation of a group of double star observers which was transformed into the Commission des É toiles Doubles

Ghostly Remnant of an Explosive Past

NASA Image and Video Library

2007-03-07

This enhanced image from the far-ultraviolet detector on NASA Galaxy Evolution shows a ghostly shell of ionized gas around Z Camelopardalis, a binary, or double-star system featuring a collapsed, dead star known as a white dwarf, and a companion star.

Double Star Measurements at the Northern Sky with a 10 inch Newtonian in 2014 and 2015

NASA Astrophysics Data System (ADS)

Anton, Rainer

2017-07-01

A 10 inch Newtonian was used for recordings of double stars with a CCD webcam, and measurements of 120 pairs were done with the technique of “lucky imaging”. A rather accurate value of the image scale was obtained with reference systems from the recently published Gaia catalogue of very precise position data. For several pairs, deviations from currently assumed orbits were found. Some images of noteworthy systems are also presented.

LIADA's Double Star Section: Studies Of Visual Double Star By Amateurs

NASA Astrophysics Data System (ADS)

Rica, F. M.; Benavides, R.; Masa, E.; Ling, J.

2007-08-01

LIADA's Double Star Section has as main goal to perform measures of relative astrometry of neglected and unconfirmed wide pairs, as well as to determine the astrophysical properties for their components and classify them, according to their nature, as phyisical, common origin, common proper motion or optical pairs. BVIJHK photometry, relative astrometry and kinematical data in addition to other astrophysical parameters, were obtained from literature to characterize the components and the stellar systems. VizieR, Simbad. Aladin and the "services abstract" tools were used from the website of Centre De Données Stellaires de Strasbourg (CDS). USNO catalogs (USNO-B1.0 and UCAC-2) in addition to ESA catalogs (Tycho-2 and HIPPARCOS) were often used. Spectral types, luminosity classes, absolute magnitudes, photometric distances were determined by using several tables, two colours and reduced proper motion diagrams. Astrophysical properties were corrected by reddening by using several maps. CCD cameras, micrometric eyepieces, photographic plates from Digitalized Sky Survey (DSS) and other surveys were used to perform our astrometric measures. According to their nature double stars are classified by using several professional criteria. Since 2001 LIADA has studied about 500 visual double stars, has discovered about 150 true binaries and several candidates to be white dwarfs, subdwarfs and nearby stars. Several orbits have been calculated. Our results were published in national and international journals such as Journal of Double Star Observations (JDSO), in Information Circulars edited by Commision 26 of IAU and our measures were included in WDS catalog. LIADA publish a circular twice a year with our results.

Radio Emission from Binary Stars

NASA Astrophysics Data System (ADS)

Hjellming, R.; Murdin, P.

2000-11-01

Stellar radio emission is most common in double star systems where each star provides something essential in producing the large amounts of radio radiation needed for it to be detectable by RADIO TELESCOPES. They transfer mass, supply energy or, when one of the stars is a NEUTRON STAR or BLACK HOLE, have the strong gravitational fields needed for the energetic particles and magnetic fields needed...

Stars

NASA Astrophysics Data System (ADS)

Capelato, Hugo Vicente

1999-01-01

We will begin our study with a more or less superficial inspection of the "forest" of stars that we see in the skies. The first thing we notice is that, as sources of light, they are much weaker than the Sun. Second, their apparent colors vary; from a bluish-white in most of them to a reddish-yellow, which is rarer. There is also a third aspect, though it is not very obvious to the naked eye: most of the stars group themselves in small families of two, three or more members. A good example is the Alpha Centauri, the closest star to us, which, in fact, is a triple system of stars. Another is the group of 7 stars that make up the Pleiades, which will be discussed later on. In fact, almost half of the stars are double systems with only two members, called binary stars. Most of these double stars, though together, are separated by several astronomical units (one astronomical unit, AU, is the distance from Earth to the sun: see Chapter 1), and revolve around each other over periods of several years. And yet the revolutions of some binary stars, separated by much smaller distances, occur in only a few hours! These stars are so close to each other that they can share enveloping material. Often this exchange occurs in a somewhat violent manner. Local explosions may occur, expelling matter away from the system. In other binary systems, where one of the components is a very compact, dense star, companion material flows more calmly, making up a light disk around the compact star.

Double Star Measurements at the Southern Sky with a 50 cm Reflector in 2016

NASA Astrophysics Data System (ADS)

Anton, Rainer

2017-10-01

A 50 cm Ritchey-Chrétien reflector was used for recordings of double stars with a CCD webcam, and measurements of 95 pairs were mostly obtained from “lucky images”, and in some cases by speckle interferometry. The image scale was calibrated with reference systems from the recently published Gaia catalogue of precise position data. For several pairs, deviations from currently assumed orbits were found. Some images of noteworthy systems are also pre-sented.

Refuting S 825AB System Classification through Astrometry and Gaia Satellite Data

NASA Astrophysics Data System (ADS)

Lyman, Noah; Musegades, Lila; Davis, Edward; Briney, Micah; Francis, Aaron; Niebuhr, Cole; Rowe, David; Harshaw, Richard; Genet, Russell

2018-04-01

A student-led team of researchers studied double star S 825AB (WDS 23100+3651). Analysis of ten CCD images obtained by the Sierra Research Observatory yielded an average position angle of 318.37º and an average separation of 67.38". Comparing these results to published findings in the Washington Double Star Catalog and measurements taken from the European Space Agency's Gaia astrometry satellite, the team concluded that S 825AB is not a binary system.

Accretion onto neutron stars with the presence of a double layer

NASA Technical Reports Server (NTRS)

Williams, A. C.; Weisskopf, M. C.; Elsner, R. F.; Darbro, W.; Sutherland, P. G.

1986-01-01

It is known from laboratory experiments that double layers can form in plasmas, usually in the presence of an electric current. It is argued that a double layer may be present in the accretion column of a neutron star in a binary system. It is suggested that the double layer may be the predominant deceleration mechanism for the accreting ions, especially for sources with X-ray luminosities of less than about 10 to the 37th erg/s. Previous models have involved either a collisionless shock or an assumed gradual deceleration of the accreting ions to thermalize the energy of the infalling matter.

Accretion onto neutron stars with the presence of a double layer

NASA Technical Reports Server (NTRS)

Williams, A. C.; Weisskopf, M. C.; Elsner, R. F.; Darbro, W.; Sutherland, P. G.

1987-01-01

It is known, from laboratory experiments, that double layers will form in plasmas, usually in the presence of an electric current. It is argued that a double layer may be present in the accretion column of a neutron star in a binary system. It is suggested that the double layer may be the predominant deceleration mechanism for the accreting ions, especially for sources with X-ray luminosities of less than about 10 to the 37th erg/s. Previous models have involved either a collisionless shock or an assumed gradual deceleration of the accreting ions to thermalize the energy of the infalling matter.

Measurements of Neglected Double Stars: February 2018 Report

NASA Astrophysics Data System (ADS)

Carro, Joseph M.

2018-07-01

This article presents measurements of 53 neglected double stars. The stars were selected from the Washington Double Star Catalog published by the United States Naval Observatory. The photographs were taken by remote telescopes. The measurements were done by the author.

An accessible echelle pipeline and its application to a binary star

NASA Astrophysics Data System (ADS)

Carmichael, Theron; Johnson, John Asher

2018-01-01

Nearly every star observed in the Galaxy has one or more companions that play an integral role in the evolution of the star. Whether it is a planet or another star, a companion opens up opportunities for unique forms of analysis to be done on a system. Some 2400 lightyears away, there is a 3-10 Myr old binary system called KH 15D, which not only includes two T Tauri K-type stars in a close orbit of 48 days, but also a truncated, coherently precessing warped disk in a circumbinary orbit.In binary systems, a double-lined spectroscopic binary may be observable in spectra. This is a spectrum that contains a mixture of each star's properties and manifests as two sets of spectral emission and absorption lines that correspond to each star. Slightly different is a single-lined spectroscopic binary, where only one set of spectral lines from one star is visible. The data of KH 15D are studied in the form of a double single-lined spectroscopic binary. This means that at two separate observing times, a single-lined spectroscopic binary is obtained from one of the stars of KH 15D. This is possible because of the circumbinary disk that blocks one star at a time from view.Here, we study this binary system with a combination of archival echelle data from the Keck Observatory and new echelle data from Las Campanas Observatory. This optical data is reduced with a new Python-based pipeline available on GitHub. The objective is to measure the mass function of the binary star and refine the current values of each star's properties.

A Weekend Workshop on Double Stars for Students

NASA Astrophysics Data System (ADS)

Brewer, Mark; Estrada, Chris; Estrada, Reed; Gillette, Sean

2016-01-01

A weekend double star workshop was held by Vanguard Preparatory for selected eighth grade students with the purpose of introducing them to astrometric observational science. The students were selected based on an essay provided by their language arts class. Collaboration with local visiting astronomers was established to provide telescopes equipped with an astrometric eyepiece, observational supervision, and expertise. During the workshop students learned how to determine the scale constant of an astrometric eyepiece, and the procedure for measuring separations and position angles of double stars. The students compared their data to past measurements reported in the Washington Double Star Catalog. Three goals were set for the student's outcome: 1) observe, record, and report observations of double stars, 2) write a scientific paper for publication in the Journal of Double Star Observations, and 3) present a PowerPoint presentation to their peers. This paper chronicles the planning, preparation, funding, and execution required to complete a double star workshop at a public middle school.

Hydrodynamical simulations of the tidal stripping of binary stars by massive black holes

NASA Astrophysics Data System (ADS)

Mainetti, Deborah; Lupi, Alessandro; Campana, Sergio; Colpi, Monica

2016-04-01

In a galactic nucleus, a star on a low angular momentum orbit around the central massive black hole can be fully or partially disrupted by the black hole tidal field, lighting up the compact object via gas accretion. This phenomenon can repeat if the star, not fully disrupted, is on a closed orbit. Because of the multiplicity of stars in binary systems, also binary stars may experience in pairs such a fate, immediately after being tidally separated. The consumption of both the binary components by the black hole is expected to power a double-peaked flare. In this paper, we perform for the first time, with GADGET2, a suite of smoothed particle hydrodynamics simulations of binary stars around a galactic central black hole in the Newtonian regime. We show that accretion luminosity light curves from double tidal disruptions reveal a more prominent knee, rather than a double peak, when decreasing the impact parameter of the encounter and when elevating the difference between the mass of the star which leaves the system after binary separation and the mass of the companion. The detection of a knee can anticipate the onset of periodic accretion luminosity flares if one of the stars, only partially disrupted, remains bound to the black hole after binary separation. Thus knees could be precursors of periodic flares, which can then be predicted, followed up and better modelled. Analytical estimates in the black hole mass range 105-108 M⊙ show that the knee signature is enhanced in the case of black holes of mass 106-107 M⊙.

How do stars form

NASA Astrophysics Data System (ADS)

Tscharnuter, W. M.

1980-02-01

Modes and model concept of star formation are reviewed, beginning with the theory of Kant (1755), via Newton's exact mathematical formulation of the laws of motion, his recognition of the universal validity of general gravitation, to modern concepts and hypotheses. Axisymmetric and spherically symmetric collapse models are discussed, and the origin of double and multiple star systems is examined.

LSS 2018: A double-lined spectroscopic binary central star with an extremely large reflection effect

NASA Technical Reports Server (NTRS)

Drilling, J. S.

1985-01-01

LSS 2018, the central star of the planetry nebulae DS1, was found to be a double-lined spectroscopic binary with a period of 8.571 hours. Light variations with the same period were observed in U, B, and V; in the wavelength regions defined by the two IUE cameras; and in the strength of the CIII 4647 emission line. The light variations can be accurately predicted by a simple reflection effect, and an analysis of the light curves yields the angular diameter and effective temperature of the primary, the radii of the two stars in terms of their separation, and the inclination of the system. Analysis of the radial velocities then yields the masses of the two stars, their separation, the distance of the system, the absolute magnitude of the primary, and the size of the nebula.

HST Observations of Astrophysically Important Visual Binaries

NASA Astrophysics Data System (ADS)

Bond, Howard

2013-10-01

We propose to continue our long-term program of astrometry of close visual binaries, with the primary goal of determining purely dynamical masses for 3 important main-sequence stars and 9 white dwarfs {WDs}. A secondary aim is to set limits on third bodies in the systems down to planetary mass. Three of our targets are naked-eye stars with much fainter companions that are extremely difficult to image from the ground. Our other 2 targets are double WDs, whose small separations and faintness likewise make them difficult to measure using ground-based techniques. Observations have been completed for a 3rd double WD.The bright stars, to be imaged with WFC3, are: {1} Procyon {P = 40.83 yr}, containing a bright F star and a much fainter WD companion. With the continued monitoring proposed here, we will obtain masses to an accuracy of better than 1%, providing a testbed for theories of both Sun-like stars and WDs. {2} Sirius {P = 50.14 yr}, an A-type star also having a faint WD companion, Sirius B, the nearest and brightest of all WDs. {3} Mu Cas {P = 21.08 yr}, a nearby metal-deficient G dwarf for which accurate masses will lead to the stars' helium contents, with cosmological implications. The faint double WDs, to be observed with FGS, are: {1} G 107-70 {P = 18.84 yr}, and {2} WD 1818+126 {P = 12.19 yr}. Our astrometry of these systems will add 4 accurate masses to the handful of WD masses that are directly known from dynamical measurements. The FGS measurements will also provide precise parallaxes for the systems, a necessary ingredient in the mass determinations.

HST Observations of Astrophysically Important Visual Binaries

NASA Astrophysics Data System (ADS)

Bond, Howard

2015-10-01

We propose to continue our long-term program of astrometry of close visual binaries, with the primary goal of determining purely dynamical masses for 3 important main-sequence stars and 9 white dwarfs (WDs). A secondary aim is to set limits on third bodies in the systems down to planetary mass. Three of our targets are naked-eye stars with much fainter companions that are extremely difficult to image from the ground. Our other 2 targets are double WDs, whose small separations and faintness likewise make them difficult to measure using ground-based techniques. Observations have been completed for a 3rd double WD.The bright stars, to be imaged with WFC3, are: (1) Procyon (P = 40.83 yr), containing a bright F star and a much fainter WD companion. With the continued monitoring proposed here, we will obtain masses to an accuracy of better than 1%, providing a testbed for theories of both Sun-like stars and WDs. (2) Sirius (P = 50.14 yr), an A-type star also having a faint WD companion, Sirius B, the nearest and brightest of all WDs. (3) Mu Cas (P = 21.08 yr), a nearby metal-deficient G dwarf for which accurate masses will lead to the stars' helium contents, with cosmological implications. The faint double WDs, to be observed with FGS, are: (1) G 107-70 (P = 18.84 yr), and (2) WD 1818+126 (P = 12.19 yr). Our astrometry of these systems will add 4 accurate masses to the handful of WD masses that are directly known from dynamical measurements. The FGS measurements will also provide precise parallaxes for the systems, a necessary ingredient in the mass determinations.

HST Observations of Astrophysically Important Visual Binaries

NASA Astrophysics Data System (ADS)

Bond, Howard

2014-10-01

We propose to continue our long-term program of astrometry of close visual binaries, with the primary goal of determining purely dynamical masses for 3 important main-sequence stars and 9 white dwarfs (WDs). A secondary aim is to set limits on third bodies in the systems down to planetary mass. Three of our targets are naked-eye stars with much fainter companions that are extremely difficult to image from the ground. Our other 2 targets are double WDs, whose small separations and faintness likewise make them difficult to measure using ground-based techniques. Observations have been completed for a 3rd double WD.The bright stars, to be imaged with WFC3, are: (1) Procyon (P = 40.83 yr), containing a bright F star and a much fainter WD companion. With the continued monitoring proposed here, we will obtain masses to an accuracy of better than 1%, providing a testbed for theories of both Sun-like stars and WDs. (2) Sirius (P = 50.14 yr), an A-type star also having a faint WD companion, Sirius B, the nearest and brightest of all WDs. (3) Mu Cas (P = 21.08 yr), a nearby metal-deficient G dwarf for which accurate masses will lead to the stars' helium contents, with cosmological implications. The faint double WDs, to be observed with FGS, are: (1) G 107-70 (P = 18.84 yr), and (2) WD 1818+126 (P = 12.19 yr). Our astrometry of these systems will add 4 accurate masses to the handful of WD masses that are directly known from dynamical measurements. The FGS measurements will also provide precise parallaxes for the systems, a necessary ingredient in the mass determinations.

Studing the Post Merger Evolution of White Dwarf Mergers with FLASH

NASA Astrophysics Data System (ADS)

Jenks, Malia

2017-06-01

There is still uncertainty as to the progenitor systems of type Ia supernova (SN Ia). Both single and double degenerate systems have been suggested as progenitors. In a double degenerate system a merger between the two white dwarfs, with total mass at or exceeding the Chandrasekhar mass, leads to the supernova. If the explosion occurs during the merging process it is a violent merger. If an explosion doesn't occur while the stars merge the system becomes a white dwarf of unstable mass. For mergers of this type with differing starting masses it has been shown that during the viscous evolution carbon burning starts far from the center and stably converts the star to oxygen and neon. In this case the star will eventually collapse to a neutron star and not produce an SN Ia. The case of similar mass mergers has been much less explored. Using the results of a smooth particle hydrodynamic merger we simulate the viscous evolution of an equal mass model with FLASH. These simulations test if a similar mass merger can lead to an SN Ia.

Exploring the Binary Nature of STF 2128 Using Separation and Position Angle Measurements

NASA Astrophysics Data System (ADS)

Minarik, Holly; Helm, Victoria; Asquith, Ezra; Hoffman, Andrew; Fielding, Alec; Gaytan, Humberto; Marvier, Kevin; Warneke, Walter; Howell, James; Rowe, David; Freed, Rachel; Genet, Russell

2018-01-01

A team of nine students from Cuesta College studied double star STF 2128 (WDS 17033+5935) using ten CCD images obtained at the Sierra Remote Observatories. Calculations of these ten observations yielded an average separation of 12.203" and an average position angle of 42.957°. By comparing these values with past observations from the Washington Double Star Catalogue, we concluded that STF 2128 is likely a true binary system.

Building an Unusual White-Dwarf Duo

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-09-01

A new study has examined how the puzzling wide binary system HS 2220+2146 which consists of two white dwarfs orbiting each other might have formed. This system may be an example of a new evolutionary pathway for wide white-dwarf binaries.Evolution of a BinaryMore than 100 stellar systems have been discovered consisting of two white dwarfs in a wide orbit around each other. How do these binaries form? In the traditional picture, the system begins as a binary consisting of two main-sequence stars. Due to the large separation between the stars, the stars evolve independently, each passing through the main-sequence and giant branches and ending their lives as white dwarfs.An illustration of a hierarchical triple star system, in which two stars orbit each other, and a third star orbits the pair. [NASA/JPL-Caltech]Because more massive stars evolve more quickly, the most massive of the two stars in a binary pair should be the first to evolve into a white dwarf. Consequently, when we observe a double-white-dwarf binary, its usually a safe bet that the more massive of the two white dwarfs will also be the older and cooler of the pair, since it should have formed first.But in the case of the double-white-dwarf binary HS 2220+2146, the opposite is true: the more massive of the two white dwarfs appears to be the younger and hotter of the pair. If it wasnt created in the traditional way, then how did this system form?Two From Three?Led by Jeff Andrews (Foundation for Research and Technology-Hellas, Greece and Columbia University), a team of scientists recently examined this system more carefully, analyzing its spectra to confirm our understanding of the white dwarfs temperatures and masses.Based on their observations, Andrews and collaborators determined that there are no hidden additional companions that could have caused the unusual evolution of this system. Instead, the team proposed that this unusual binary might be an example of an evolutionary channel that involves three stars.The authors proposed formation scenario for H220+2146. In this picture, the inner binary merges to form a blue straggler. This star and the remaining main-sequence star then evolve independently into white dwarfs, forming the system observed today. [Andrews et al. 2016]An Early MergerIn the model the authors propose for HS 2220+2146, the binary system began as a hierarchical triple system of main-sequence stars. The innermost binary then merged to form a large star known as a blue straggler a star that, due to the merger, will evolve more slowly than its larger mass implies it should.The blue straggler and the remaining main-sequence star, still in a wide orbit, then continued to evolve independently of each other. The smaller star ended its main-sequence lifetime and became a white dwarf first, followed by the more massive but slowly evolving blue straggler thus forming the system we observe today.If the authors model is correct, then HS 2220+2146 would be the first binary double white dwarf known to have formed through this channel. ESAs Gaia mission, currently underway, is expected to discover up to a million new white dwarfs, many of which will likely be in wide binary systems. Among these, we may well find many other systems like HS 2220+2146 that formed in the same way.CitationJeff J. Andrews et al 2016 ApJ 828 38. doi:10.3847/0004-637X/828/1/38

HEARTBEAT STARS: SPECTROSCOPIC ORBITAL SOLUTIONS FOR SIX ECCENTRIC BINARY SYSTEMS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smullen, Rachel A.; Kobulnicky, Henry A., E-mail: rsmullen@email.arizona.edu

2015-08-01

We present multi-epoch spectroscopy of “heartbeat stars,” eccentric binaries with dynamic tidal distortions and tidally induced pulsations originally discovered with the Kepler satellite. Optical spectra of six known heartbeat stars using the Wyoming Infrared Observatory 2.3 m telescope allow measurement of stellar effective temperatures and radial velocities from which we determine orbital parameters including the periods, eccentricities, approximate mass ratios, and component masses. These spectroscopic solutions confirm that the stars are members of eccentric binary systems with eccentricities e > 0.34 and periods P = 7–20 days, strengthening conclusions from prior works that utilized purely photometric methods. Heartbeat stars inmore » this sample have A- or F-type primary components. Constraints on orbital inclinations indicate that four of the six systems have minimum mass ratios q = 0.3–0.5, implying that most secondaries are probable M dwarfs or earlier. One system is an eclipsing, double-lined spectroscopic binary with roughly equal-mass mid-A components (q = 0.95), while another shows double-lined behavior only near periastron, indicating that the F0V primary has a G1V secondary (q = 0.65). This work constitutes the first measurements of the masses of secondaries in a statistical sample of heartbeat stars. The good agreement between our spectroscopic orbital elements and those derived using a photometric model support the idea that photometric data are sufficient to derive reliable orbital parameters for heartbeat stars.« less

CCD Astrometric Measurements of WDS 04155+0611

NASA Astrophysics Data System (ADS)

Cao, Zhixin; Li, Junyao; Li, Jeff; Qu, Steve; Fene, Michael; Boyce, Grady; Boyce, Pat

2016-01-01

Twenty-two separations and position angle astrometric measurements were made of the multiple star system WDS 04155+0611. This system includes the pairs STTA 45 AB, H 6 98 AC, H 6 98 CD, and STU 18 CE. All measurements were compared with historical measurements from the Washington Double Star Catalog. Our astrometric results compare favorably with other recent observations.

Double Star Measurements at the Internationale Amateur Sternwarte (IAS) in Namibia in 2008 and 2009

NASA Astrophysics Data System (ADS)

Anton, Rainer

2010-04-01

A 40-cm-Cassegrain telescope in Namibia was used for observing double and multiple systems in the southern sky. Digital images were recorded with a CCD camera at high frame rates via a firewire interface directly in a computer. Measurements of 34 double and multiple systems are presented and compared with literature data. Some noteworthy objects are discussed in more detail.

fd3: Spectral disentangling of double-lined spectroscopic binary stars

NASA Astrophysics Data System (ADS)

Ilijić, Saša

2017-05-01

The spectral disentangling technique can be applied on a time series of observed spectra of a spectroscopic double-lined binary star (SB2) to determine the parameters of orbit and reconstruct the spectra of component stars, without the use of template spectra. fd3 disentangles the spectra of SB2 stars, capable also of resolving the possible third companion. It performs the separation of spectra in the Fourier space which is faster, but in several respects less versatile than the wavelength-space separation. (Wavelength-space separation is implemented in the twin code CRES.) fd3 is written in C and is designed as a command-line utility for a Unix-like operating system. fd3 is a new version of FDBinary (ascl:1705.011), which is now deprecated.

A novel double fine guide sensor design on space telescope

NASA Astrophysics Data System (ADS)

Zhang, Xu-xu; Yin, Da-yi

2018-02-01

To get high precision attitude for space telescope, a double marginal FOV (field of view) FGS (Fine Guide Sensor) is proposed. It is composed of two large area APS CMOS sensors and both share the same lens in main light of sight. More star vectors can be get by two FGS and be used for high precision attitude determination. To improve star identification speed, the vector cross product in inter-star angles for small marginal FOV different from traditional way is elaborated and parallel processing method is applied to pyramid algorithm. The star vectors from two sensors are then used to attitude fusion with traditional QUEST algorithm. The simulation results show that the system can get high accuracy three axis attitudes and the scheme is feasibility.

Gravitational microlensing by double stars and planetary systems

NASA Technical Reports Server (NTRS)

Mao, Shunde; Paczynski, Bohdan

1991-01-01

Almost all stars are in binary systems. When the separation between the two components is comparable to the Einstein ring radius corresponding to the combined mass of the binary acting as a gravitational lens, then an extra pair of images can be created, and the light curve of a lensed source becomes complicated. It is estimated that about 10 percent of all lensing episodes of the Galactic bulge stars will strongly display the binary nature of the lens. The effect is strong even if the companion is a planet. A massive search for microlensing of the Galactic bulge stars may lead to a discovery of the first extrasolar planetary systems.

Forming short-period Wolf-Rayet X-ray binaries and double black holes through stable mass transfer

NASA Astrophysics Data System (ADS)

van den Heuvel, E. P. J.; Portegies Zwart, S. F.; de Mink, S. E.

2017-11-01

We show that black hole high-mass X-ray binaries (HMXBs) with O- or B-type donor stars and relatively short orbital periods, of order one week to several months may survive spiral-in, to then form Wolf-Rayet (WR) X-ray binaries with orbital periods of order a day to a few days; while in systems where the compact star is a neutron star, HMXBs with these orbital periods never survive spiral-in. We therefore predict that WR X-ray binaries can only harbour black holes. The reason why black hole HMXBs with these orbital periods may survive spiral-in is: the combination of a radiative envelope of the donor star and a high mass of the compact star. In this case, when the donor begins to overflow its Roche lobe, the systems are able to spiral in slowly with stable Roche lobe overflow, as is shown by the system SS433. In this case, the transferred mass is ejected from the vicinity of the compact star (so-called isotropic re-emission mass-loss mode, or SS433-like mass-loss), leading to gradual spiral-in. If the mass ratio of donor and black hole is ≳3.5, these systems will go into common-envelope evolution and are less likely to survive. If they survive, they produce WR X-ray binaries with orbital periods of a few hours to one day. Several of the well-known WR+O binaries in our Galaxy and the Magellanic Clouds, with orbital periods in the range between a week and several months, are expected to evolve into close WR-black hole binaries, which may later produce close double black holes. The galactic formation rate of double black holes resulting from such systems is still uncertain, as it depends on several poorly known factors in this evolutionary picture. It might possibly be as high as ˜10-5 yr-1.

Tests of general relativity from timing the double pulsar.

PubMed

Kramer, M; Stairs, I H; Manchester, R N; McLaughlin, M A; Lyne, A G; Ferdman, R D; Burgay, M; Lorimer, D R; Possenti, A; D'Amico, N; Sarkissian, J M; Hobbs, G B; Reynolds, J E; Freire, P C C; Camilo, F

2006-10-06

The double pulsar system PSR J0737-3039A/B is unique in that both neutron stars are detectable as radio pulsars. They are also known to have much higher mean orbital velocities and accelerations than those of other binary pulsars. The system is therefore a good candidate for testing Einstein's theory of general relativity and alternative theories of gravity in the strong-field regime. We report on precision timing observations taken over the 2.5 years since its discovery and present four independent strong-field tests of general relativity. These tests use the theory-independent mass ratio of the two stars. By measuring relativistic corrections to the Keplerian description of the orbital motion, we find that the "post-Keplerian" parameter s agrees with the value predicted by general relativity within an uncertainty of 0.05%, the most precise test yet obtained. We also show that the transverse velocity of the system's center of mass is extremely small. Combined with the system's location near the Sun, this result suggests that future tests of gravitational theories with the double pulsar will supersede the best current solar system tests. It also implies that the second-born pulsar may not have formed through the core collapse of a helium star, as is usually assumed.

The chemically peculiar double-lined spectroscopic binary HD 90264

NASA Astrophysics Data System (ADS)

Quiroga, C.; Torres, A. F.; Cidale, L. S.

2010-10-01

Context. HD 90264 is a chemically peculiar (CP) double-lined spectroscopic binary system of the type He-weak. Double-lined binaries are unique sources of data for stellar masses, physical properties, and evolutionary aspects of stars. Therefore, the determination of orbital elements is of great importance to study how the physical characteristics of CP stars are affected by a companion. Aims: We carried out a detailed spectral and polarimetric study of the spectroscopic binary system HD 90264 to characterize its orbit, determine the stellar masses, and investigate the spectral variability and possible polarization of the binary components. Methods: We employed medium-resolution échelle spectra and polarimetric data obtained at the 2.15-m telescope at CASLEO Observatory, Argentina. We measured radial velocities and line equivalent widths with IRAF packages. The radial velocity curves of both binary components were obtained combining radial velocity data derived from the single line of Hg II λ3984 Åand the double lines of Mg II λ4481 Å. Polarimetric data were studied by means of the statistical method of Clarke & Stewart and the Welch test. Results: We found that both components of the binary system are chemically peculiar stars, deficient in helium, where the primary is a He variable and the secondary is a Hg-Mn star. We derived for the first time the orbital parameters of the binary system. We found that the system has a quasi-circular orbit (e ~ 0.04) with an orbital period of 15.727 days. Taking into account the circular orbit solution, we derived a mass ratio of q = MHe-w/MHg-Mn = 1.22. We also found a rotational period of around 15-16 days, suggesting a spin-orbit synchronization. Possible signs of intrinsic polarization have also been detected. Conclusions: HD 90264 is the first known binary system comprised of a He variable star as the primary component and a Hg-Mn star as the secondary one. Based on observations taken at Complejo Astronómico El Leoncito (CASLEO), operated under an agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina, the Secretaría de Ciencia y Tecnología de la Nación and the National Universities of La Plata, Córdoba and San Juan.

HR 7578 - A K dwarf double-lined spectroscopic binary with peculiar abundances

NASA Technical Reports Server (NTRS)

Fekel, F. C., Jr.; Beavers, W. I.

1983-01-01

The number of double-lined K and M dwarf binaries which is currently known is quite small, only a dozen or less of each type. The HR 7578 system was classified as dK5 on the Mount Wilson system and as K2 V on the MK ystem. A summary of radial-velocity measurements including the observatory and weight of each observation is given in a table. The star with the stronger lines has been called component A. The final orbital element solution with all observations appropriately weighted was computed with a differential corrections computer program described by Barker et al. (1967). The program had been modified for the double-lined case. Of particular interest are the very large eccentricity of the system and the large minimum masses for each component. These large minimum masses suggest that eclipses may be detectable despite the relatively long period and small radii of the stars.

CCD Astrometric Measurements of WDS 08167+4053 Using the iTelescope Network

NASA Astrophysics Data System (ADS)

Riley, Bill; Li, Dewei; Li, Junyao; Dennis, Aren; Boyce, Grady; Boyce, Pat

2016-10-01

Separations and position angle astrometric measurements were made of the multiple star system WDS 08167+4053 AB, AC, and BC components. Our measurements compared favorably with historical measurements from the United States Naval Observatory Washington Double Star Catalog, confirming the trend.

Studying white dwarf merger remnants with FLASH

NASA Astrophysics Data System (ADS)

Jenks, Malia

2017-01-01

There is still uncertainty as to the progenitor systems of type Ia supernova (SN Ia). Both single and double degenerate systems have been suggested as progenitors. In a double degenerate system a merger between the two white dwarfs, with total mass at or exceeding the Chandrasekhar mass, leads to the supernova. If the explosion occurs during the merging process it is a violent merger. If an explosion doesn't occur while the stars merge the system becomes a white dwarf of unstable mass. For mergers of this type with differing starting masses it has been shown that during the viscous evolution carbon burning starts far from the center and stably converts the star to oxygen and neon. In this case the star will eventually collapse to a neutron star and not produce an SN Ia. The case of similar mass mergers has been much less explored. Using the results of a smooth particle hydrodynamic merger we simulate the viscous evolution of models of different mass ratios with FLASH. These simulations test if a similar mass merger can lead to an SN Ia, and begin to probe where the transition from similar to dissimilar mass occurs.

The Maui International Double Star Conference

NASA Astrophysics Data System (ADS)

Genet, Russell

2013-04-01

A three-day double star conference in February, 2013, covered double star observations from simple eyepiece astrometry of wide binaries, with orbital periods of centuries, to amplitude interferometry of binaries with periods measured in days or even hours. A wide range of participants, from students and amateurs to professionals shared their perspectives in panel discussions. This was the first conference of the newly-formed International Association of Double Star Observers (IADSO). PDFs of 22 of the talks and YouTube links to 23 of the talks and panels are available at www.IADSO.org.

Student Measurements of the Double Star Eta Cassiopeiae

NASA Astrophysics Data System (ADS)

Brewer, Mark; Cacace, Gabriel; Do, Vivian; Griffith, Nicholas; Malan, Alexandria; Paredes, Hanna; Peticolas, Brian; Stasiak, Kathryne

2016-10-01

The double star Eta Cassiopeiae was measured at Vanguard Preparatory School. Digital measurements were made with a 14-inch telescope equipped with a CCD camera. The plate scale was determined to be 0.50 arcseconds per pixel. The separations and position angles were determined to be 13.3 arcseconds and 340.4 degrees, by the use of astronomy software. Previous observations reported in the Washington Double Star Catalog were used as a comparison. The camera angle was found to be the ultimate issue in the skewed data gathered for the double star.

Visual Double Stars - St. Mary's High School Astronomy Club

NASA Astrophysics Data System (ADS)

Bensel, Holly; Tran, Thanh; Hicks, Sean; He, Yifan; Moczygemba, Mitchell; Shi, Yuqi; Sternenberg, Leah; Watson, Kaycia; Rooney, Kieran; Birmingham, Paige; You, Ruiyang

2017-01-01

The St. Mary’s School Astronomy Club is working towards measuring positions and angles of relatively unstudied visual binary stars. We are starting with confirming prior results we obtained at the Pine Mountain Observatory Summer Science Research Workshop in 2009 - 2012 on ARY 52 (Frey et al. 2009, JDSO), Iota Bootis (Bensel et al. 2009, JDSO), and Mizar (Bensel et al. 2009, JDSO). We are also comparing our results with those published in the Washington Double Star Catalog (Mason 2009). We are using Pine Mountain Observatory’s remote imaging 14-inch Meade Schmidt-Cassegrain telescope equipped with a CCD camera operated by Scott Fisher at the University of Oregon and local astronomer Sean Curry’s 12.5" PlaneWave CDK telescope. We are practicing using tools such as astrometry.net and DS9 software to measure positions and angles on known double stars with well established values before attempting new measurements. Our next project will be to study “neglected visual double stars,” lesser studied double stars with fainter magnitudes. (A neglected double star is one that has not been observed extensively or recently.)Double star analysis is relatively straight forward and can be performed with equipment available to most high schools.Educational outcomes include instrument setup, orientation, instruction, observations, analysis, presentation of data, and writing up findings for publication. Accurate recording of data is a useful and important life skill for all students to learn. Another important life skill is learning to work together to accomplish a specific goal. This project allows novice and experienced observers to work hand-in-hand to accomplish a specific goal, such as the publishing of a research paper in the Journal of Double Star Observations.

CCD Astrometric Measurements of Double Stars BAL 746, BPM 342, KU 92, and STF 897

NASA Astrophysics Data System (ADS)

Smith, Schuyler

2017-07-01

Double stars WDS 06589-0106 (BAL 746), WDS 06579+1430 (BPM 342), WDS 07006+0921 (KU 92), and WDS 06224+2640 (STF 897) were measured as part of a science fair project for the 2016 Greater San Diego Science and Engineering Fair. The goal was to measure the separation and position angles of stars by using a telescope with a charge-coupled device (CCD) on the iTelescope network. Five images were taken of each of the stars. These images were plate solved with Visual PinPoint and measured using Aladin Sky Atlas. Measurements for all five doubles compare well to the more recent values in the Washington Double Star Catalog.

Visual Double Stars with More Than One WDS Number

NASA Astrophysics Data System (ADS)

Rica, F. M.

2005-04-01

WDS catalog is one of the most important reference for double star observers and we must consider it as something that is ours and so we must maintain it, for example, detecting and communicating errors to the database administrator. In this work the author presents two double stars that had two entries in WDS catalog. The doubles were studied, their nature determined and the errors corrected in WDS.

Reclassification of WDS 18224+4545 from a Binary to Optical Double Star

NASA Astrophysics Data System (ADS)

Parent, Ian; Vaughn, S.; Conover, Ellery; Williams, Michelle; Steed, Jordan; Orman, Daniel; Gardella, Jessica; Siverson, Nels; Ogden, Jonathan; Genet, Russell

2017-07-01

In 1998, based exclusively on visual observations, Wulff Heintz calculated an orbital path, with a period of 234 years and a semi-major axis of 0.55", and determined that WDS 18224+4545 (A700) was a gravitationally bound binary star system. The research presented here disputes this and presents an optical double star system solution with a linear trajectory. Using data from the first speckle interferometry observation for A700, collected on October 22, 2013, with the 2.1-meter telescope at Kitt Peak National Observatory (KPNO), new separation and position angles were determined to be 0.623" and 127.872 deg, respectively. These results diverge radically from Heintz’s predicted orbit, and when correlated with past observational data, they follow a linear trend that returns a fit with an R2 value of 0.977. New calculations predict a minimum separation of 0.076" in the year 1953.

Radial velocities of southern visual multiple stars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tokovinin, Andrei; Pribulla, Theodor; Fischer, Debra, E-mail: atokovinin@ctio.noao.edu, E-mail: pribulla@ta3.sk, E-mail: debra.fischer@gmail.com

2015-01-01

High-resolution spectra of visual multiple stars were taken in 2008–2009 to detect or confirm spectroscopic subsystems and to determine their orbits. Radial velocities of 93 late-type stars belonging to visual multiple systems were measured by numerical cross-correlation. We provide the individual velocities, the width, and the amplitude of the Gaussians that approximate the correlations. The new information on the multiple systems resulting from these data is discussed. We discovered double-lined binaries in HD 41742B, HD 56593C, and HD 122613AB, confirmed several other known subsystems, and constrained the existence of subsystems in some visual binaries where both components turned out tomore » have similar velocities. The orbits of double-lined subsystems with periods of 148 and 13 days are computed for HD 104471 Aa,Ab and HD 210349 Aa,Ab, respectively. We estimate individual magnitudes and masses of the components in these triple systems and update the outer orbit of HD 104471 AB.« less

Concerning the Video Drift Method to Measure Double Stars

NASA Astrophysics Data System (ADS)

Nugent, Richard L.; Iverson, Ernest W.

2015-05-01

Classical methods to measure position angles and separations of double stars rely on just a few measurements either from visual observations or photographic means. Visual and photographic CCD observations are subject to errors from the following sources: misalignments from eyepiece/camera/barlow lens/micrometer/focal reducers, systematic errors from uncorrected optical distortions, aberrations from the telescope system, camera tilt, magnitude and color effects. Conventional video methods rely on calibration doubles and graphically calculating the east-west direction plus careful choice of select video frames stacked for measurement. Atmospheric motion is one of the larger sources of error in any exposure/measurement method which is on the order of 0.5-1.5. Ideally, if a data set from a short video can be used to derive position angle and separation, with each data set self-calibrating independent of any calibration doubles or star catalogues, this would provide measurements of high systematic accuracy. These aims are achieved by the video drift method first proposed by the authors in 2011. This self calibrating video method automatically analyzes 1,000's of measurements from a short video clip.

The OGLE Collection of Variable Stars. Over 450 000 Eclipsing and Ellipsoidal Binary Systems Toward the Galactic Bulge

NASA Astrophysics Data System (ADS)

Soszyński, I.; Pawlak, M.; Pietrukowicz, P.; Udalski, A.; Szymański, M. K.; Wyrzykowski, Ł.; Ulaczyk, K.; Poleski, R.; Kozłowski, S.; Skowron, D. M.; Skowron, J.; Mróz, P.; Hamanowicz, A.

2016-12-01

We present a collection of 450 598 eclipsing and ellipsoidal binary systems detected in the OGLE fields toward the Galactic bulge. The collection consists of binary systems of all types: detached, semi-detached, and contact eclipsing binaries, RS CVn stars, cataclysmic variables, HW Vir binaries, double periodic variables, and even planetary transits. For all stars we provide the I- and V-band time-series photometry obtained during the OGLE-II, OGLE-III, and OGLE-IV surveys. We discuss methods used to identify binary systems in the OGLE data and present several objects of particular interest.

Observing quantum vacuum lensing in a neutron star binary system.

PubMed

Dupays, Arnaud; Robilliard, Cécile; Rizzo, Carlo; Bignami, Giovanni F

2005-04-29

In this Letter we study the propagation of light in the neighborhood of magnetized neutron stars. Because of the optical properties of quantum vacuum in the presence of a magnetic field, the light emitted by background astronomical objects is deviated, giving rise to a phenomenon of the same kind as the gravitational one. We give a quantitative estimation of this effect, and we discuss the possibility of its observation. We show that this effect could be detected by monitoring the evolution of the recently discovered double neutron star system J0737-3039.

The Sproul 24-Inch Refractor: Entering A New Century of Research

NASA Astrophysics Data System (ADS)

Augensen, H. J.; Heintz, W. D.; Schultz, M. R.; Hassel, G. E., Jr.; Inoue, S.; Howanski, R.; Fanning, T.

1999-05-01

The Sproul Observatory, located in Swarthmore, Pennsylvania, has been in operation since 1912. Its major research instrument is a 24-inch, f/18 refracting telescope with lenses made by Brashear. The research conducted during the 20th century concentrated on obtaining parallaxes of nearby stars and also on the exploration of visual double and multiple star systems. The Sproul plate vault contains some 90,000 plates, from which 1500 stellar parallaxes, or about 10% of the current parallax database, have been extracted. Heintz made 54,000 observations (including those made with other telescopes) of double stars over 43 years (47,500 by micrometer, 6500 by photography), resulting in the calculation of 500 orbits and 900 newly discovered double stars. Photographic observations ceased in 1994. In 1998 the refractor was fitted with an Apogee AP-6 CCD camera, which contains a Kodak KAF 1000 chip with 1024 x 1024 pixel array, and gives a 0.45 arcseconds per pixel image scale and 8 x 8 arcminute field of view at the focal plane. The camera is operated using PMIS software. A filter wheel constructed by ISI Systems and attached to the camera contains 5-mm thick B, V, and R filters. The Sproul telescope has now been given a new task: the study of variable stars. Currently under investigation are RV Tauri and semiregular variables, SX Phoenicis stars, and also stars which are suspected of being variable, taken from the New Catalogue of Stars Suspected of Variability of Light, Nauka Publishing, Moscow 1982. Thus far, the most convincing cases for variability are NSV 656 (irregular?), 1098 (large amplitude, probably Mira type), 1470 (short P, eclipsing?), and 13514 (P 105d?). This work has been supported by a Provost Grant from Swarthmore College and by the Howard Hughes Medical Institute-Supported Summer Research in Science Program.

Double Star Measurements at the Internationale Amateur Sternwarte (IAS) in Namibia in 2009

NASA Astrophysics Data System (ADS)

Anton, Rainer

2012-01-01

This paper is a continuation of earlier work published in JDSO in 2010. Using a 40-cm-Cassegrain telescope in Namibia and a fast CCD camera, 87 double and multiple systems were recorded and analyzed with the technique of "lucky imaging". Measurements are compared with literature data. Some noteworthy systems are discussed in more detail.

New orbits of wide visual double stars

NASA Astrophysics Data System (ADS)

Kiyaeva, O. V.; Romanenko, L. G.; Zhuchkov, R. Ya.

2017-05-01

Based on photographic and CCD observations with the Pulkovo 26-inch refractor, radial velocity measurements with the 1.5-m RTT-150 telescope (TUBITAK National Observatory, Turkey), and highly accurate observations published in the WDS catalog, we have obtained the orbits of ten wide visual double stars by the apparent motion parameter method. The orientation of the orbits in the Galactic coordinate system has been determined. For the outer pair of the multiple star HIP 12780 we have calculated a family of orbits with a minimum period P = 4634 yr. Two equivalent solutions with the same period have been obtained for the stars HIP 50 ( P = 949 yr) and HIP 66195 ( P = 3237 yr). We have unambiguously determined the orbits of six stars: HIP 12777 ( P = 3327 yr), HIP 15058 ( P = 420 yr), HIP 33287 ( P = 1090 yr), HIP 48429 ( P = 1066 yr), HIP 69751 ( P = 957 yr), and HIP 73846 ( P = 1348 yr). The orbit of HIP 55068 is orientated perpendicularly to the plane of the sky, P >1000 yr. The star HIP 48429 is suspected to have an invisible companion.

The 1.17 Day Orbit of the Double-degenerate (DA+DQ) NLTT 16249

NASA Astrophysics Data System (ADS)

Vennes, S.; Kawka, A.; O'Toole, S. J.; Thorstensen, J. R.

2012-09-01

New spectroscopic observations show that the double-degenerate system NLTT 16249 is in a close orbit (a = 5.6 ± 0.3 R ⊙) with a period of 1.17 days. The total mass of the system is estimated between 1.47 and 2.04 M ⊙ but it is not expected to merge within a Hubble timescale (t merge ≈ 1011 yr). Vennes & Kawka originally identified the system because of the peculiar composite hydrogen (DA class) and molecular (C2-DQ class and CN) spectra and the new observations establish this system as the first DA plus DQ close double degenerate. Also, the DQ component was the first of its class to show nitrogen dredged up from the core in its atmosphere. The star may be viewed as the first known DQ descendant of the born-again PG1159 stars. Alternatively, the presence of nitrogen may be the result of past interactions and truncated evolution in a close binary system. Based on observations made with ESO telescopes at the La Silla Paranal Observatory under program ID 86.D-0562.

Student Observations of Double Star Delta Orionis (STFA 14 AC)

NASA Astrophysics Data System (ADS)

Estrada, Reed; Aguilera, Sophia; Bowden, Sam; Gillette, Travis; Givens, Jalynn; Reder, Gabriel; Rhoades, Breauna; Sharpe, Scott; Shattles, Jenna; Cha, Brendon; Do, Vicky; Ewing, Malachi; Kiamco, Alex Junior; Nelms, Brenda; Peña, Emilie; Maricarmen, Richard; Thielen, Austin

2018-01-01

A group of eight eighth graders and eight high schoolers studied the double star STFA 14 AC. They used the procedure from Argyle's book to get the separation and position angle for the double star. The students used a Celestron C8 Schmidt-Cassegrain telescope with a Baader Planetarium microguide eyepiece with similar markings to a Celestron Eyepiece. The students determined the separation to be 56 arcseconds and the position angle to be 4.19°. They compared their results to the Washington Double Star Catalog and found that they had a 2.88 arcseconds difference in separation and a 2.19° in position angle.

VizieR Online Data Catalog: RV of candidate hybrid variable stars (Lampens+, 2018)

NASA Astrophysics Data System (ADS)

Lampens, P.; Fremat, Y.; Vermeylen, L.; Sodor, A.; Skarka, M.; De Cat, P.; Bognar, Zs.; de Nutte, R.; Dumortier, L.; Escorza, A.; Oomen, G. M.; van de Steene, G.; Kamath, D.; Laverick, M.; Samadi, A.; Triana, S.; Lehmann, H.

2017-09-01

We present the individual radial velocity measurements of 50 candidate delta Scuti - gamma Doradus hybrid stars and one delta Scuti star from the Kepler mission collected with the Hermes and Ace spectrographs over a time span of months to years. The radial velocities were measured using spectrum synthesis and a two-dimensional cross-correlation technique in the case of double- and triple-lined systems. (5 data files).

Data and Analysis of the Double Stars STFA 10AB and STFA 1744AB

NASA Astrophysics Data System (ADS)

Arcilla, Marisa; Bowden, Sam; DeBlase, Jacqueline; Hall, Anthony; Hall, Corielyn; Hernandez, Alyssa; Renna, Danielle; Rodriguez, Fatima; Salazar, Cassandra; Sanchez, Andres; Teeter, Dayton; Brewer, Mark; Funk, Benjamin; Gillette, Travis; Sharpe, Scott

2017-04-01

Eighth grade students at Vanguard Preparatory School measured the double stars STFA 10AB and STFA 1744AB. A 22-inch Newtonian Alt/Az telescope and a 14-inch Celestron Schmidt Cassegrain telescope were used. The star Bellatrix was used as the calibration star to determine the scale constant of the 22-inch telescope to be 7.8 “/tick marks. The double star STFA 1744AB was used as the calibration star to determine the scale constant of the 14-inch telescope to be 5.1 “/tick marks. The separation and position angle of STFA 10AB was determined by the 22-inch telescope to be 347.9” and 339.3°. The separation and position angle of STFA 1744AB was determined by the 14-inch telescope to be 3.6” and 158.1°. The measurements that were calculated were compared to the most recent measurements listed in the Washington Double Star Catalog.

Analyzing the Proper Motion of Two Double Star Systems from Astrometric Measurements

NASA Astrophysics Data System (ADS)

Falatoun, Alex; Barrera, Janet; de Neef, Anna; Gonzalez, Aura; Calanog, Jae; Boyce, Pat; Boyce, Grady

2018-04-01

The iTelescope network was used to obtain astrometric measurements of double star systems WDS 12202-1408 (STF 1631) and WDS 12339+5522 (STI 2286). Through astrometric measurement softwares SAOImage DS9 and Mira Pro x64, a mean position angle for STF 1631 of 304.8° ± 0.9° and a mean separation 14.7" ± 0.2" was measured. For STI 2286, a newly measured mean position angle of 85.9° ± 0.9° and mean separation 11.5" ± 0.3" were obtained. The relative proper motion of 1631 shows that the system could be demonstrating a linear path or an approximately circular orbit with a period of 1400 years. Parallax measurements of the secondary star will aid in classifying if this system is a physical or a visual pair. The proper motion of STI 2286 indicates that it could be a physical pair, featuring an orbit nearing a turning point. Follow-up observations in three to four year intervals will further validate or refute this claim and constrain the shape of a possible orbit.

A novel mechanism for creating double pulsars

NASA Technical Reports Server (NTRS)

Sigurdsson, Steinn; Hernquist, Lars

1992-01-01

Simulations of encounters between pairs of hard binaries, each containing a neutron star and a main-sequence star, reveal a new formation mechanism for double pulsars in dense cores of globular clusters. In many cases, the two normal stars are disrupted to form a common envelope around the pair of neutron stars, both of which will be spun up to become millisecond pulsars. We predict that a new class of pulsars, double millisecond pulsars, will be discovered in the cores of dense globular clusters. The genesis proceeds through a short-lived double-core common envelope phase, with the envelope ejected in a fast wind. It is possible that the progenitor may also undergo a double X-ray binary phase. Any circular, short-period double pulsar found in the galaxy would necessarily come from disrupted disk clusters, unlike Hulse-Taylor class pulsars or low-mass X-ray binaries which may be ejected from clusters or formed in the galaxy.

Variable Stars in the Draco Dwarf Spheroidal Galaxy

NASA Astrophysics Data System (ADS)

Harris, H. C.; Silberman, N. A.; Smith, H. A.

A new survey of the variable stars in the Draco dwarf spheroidal galaxy updates the pioneering study of this galaxy by Baade and Swope (1961). Our improved data, taken in BVI filters with CCD cameras on three telescopes at more than 80 epochs, allow us to investigate the known variables and to discover new, mostly low-amplitude variables. Approximately 300 variables are found and classified, more than double the number of variables analyzed previously. Most are RR Lyraes, with a small fraction of Anomalous Cepheids. This large sample of variables provides a unique opportunity to study the properties of these stars in a single system. This paper discusses the census of RR Lyraes, including RRc-type, double-mode, and Blazhko-effect RR Lyraes, as well as Anomalous Cepheids, and Type II Cepheids in Draco.

PALFA Discovers Neutron Stars on a Collision Course

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2018-03-01

Got any plans in 46 million years? If not, you should keep an eye out for PSR J1946+2052 around that time this upcoming merger of two neutron stars promises to be an exciting show!Survey SuccessAverage profile for PSR J1946+2052 at 1.43 GHz from a 2 hr observation from the Arecibo Observatory. [Stovall et al. 2018]It seems like we just wrote about the dearth of known double-neutron-star systems, and about how new surveys are doing their best to find more of these compact binaries. Observing these systems improves our knowledge of how pairs of evolved stars behave before they eventually spiral in, merge, and emit gravitational waves that detectors like the Laser Interferometer Gravitational-wave Observatory might observe.Todays study, led by Kevin Stovall (National Radio Astronomy Observatory), goes to show that these surveys are doing a great job so far! Yet another double-neutron-star binary, PSR J1946+2052, has now been discovered as part of the Arecibo L-Band Feed Array pulsar (PALFA) survey. This one is especially unique due to the incredible speed with which these neutron stars orbit each other and their correspondingly (relatively!) short timescale for merger.An Extreme ExampleThe PALFA survey, conducted with the enormous 305-meter radio dish at Arecibo, has thus far resulted in the discovery of 180 pulsars including two double-neutron-star systems. The most recent discovery by Stovall and collaborators brings that number up to three, for a grand total of 16 binary-neutron-star systems (confirmed and unconfirmed) known to date.The 305-m Arecibo Radio Telescope, built into the landscape at Arecibo, Puerto Rico. [NOAO/AURA/NSF/H. Schweiker/WIYN]The newest binary in this collection, PSR J1946+2052, exhibits a pulsar with a 17-millisecond spin period thatwhips around its compact companion at a terrifying rate: the binary period is just 1.88 hours. Follow-up observations with the Jansky Very Large Array and other telescopes allowed the team to identify the binarys location to high precision and establish additional parameters of the system.PSR J1946+2052 is a system of extremes. The binarys total mass is found to be 2.5 solar masses, placing it among the lightest binary-neutron-star systems known. Its orbital period is the shortest weve observed, and the two neutron stars are on track to merge in less time than any other known neutron-star binaries: in just 46 million years. When the two stars reach the final stages of their merger, the effects of the pulsars rapid spin on the gravitational-wave signal will be the largest of any such system discovered to date.More Tests of General RelativityWhat can PSR J1946+2052 do for us? This extreme system will be especially useful as a gravitational laboratory. Continued observations of PSR J1946+2052 will pin down with unprecedented precision parameters like the Einstein delay and the rate of decay of the binarys orbit due to the emission of gravitational waves, testing the predictions of general relativity to an order of magnitude higher precision than was possible before.As we expect there to be thousands of systems like PSR J1946+2052 in our galaxy alone, better understanding this binary and finding more like it continue to be important steps toward interpreting compact-object merger observations in the future.CitationK. Stovall et al 2018 ApJL 854 L22. doi:10.3847/2041-8213/aaad06

An absence of ex-companion stars in the type Ia supernova remnant SNR 0509-67.5.

PubMed

Schaefer, Bradley E; Pagnotta, Ashley

2012-01-11

A type Ia supernova is thought to begin with the explosion of a white dwarf star. The explosion could be triggered by the merger of two white dwarfs (a 'double-degenerate' origin), or by mass transfer from a companion star (the 'single-degenerate' path). The identity of the progenitor is still controversial; for example, a recent argument against the single-degenerate origin has been widely rejected. One way to distinguish between the double- and single-degenerate progenitors is to look at the centre of a known type Ia supernova remnant to see whether any former companion star is present. A likely ex-companion star for the progenitor of the supernova observed by Tycho Brahe has been identified, but that claim is still controversial. Here we report that the central region of the supernova remnant SNR 0509-67.5 (the site of a type Ia supernova 400 ± 50 years ago, based on its light echo) in the Large Magellanic Cloud contains no ex-companion star to a visual magnitude limit of 26.9 (an absolute magnitude of M(V) = +8.4) within a region of radius 1.43 arcseconds. (This corresponds to the 3σ maximum distance to which a companion could have been 'kicked' by the explosion.) This lack of any ex-companion star to deep limits rules out all published single-degenerate models for this supernova. The only remaining possibility is that the progenitor of this particular type Ia supernova was a double-degenerate system.

CCD Astrometry with Robotic Telescopes

NASA Astrophysics Data System (ADS)

AlZaben, Faisal; Li, Dewei; Li, Yongyao; Dennis, Aren Fene, Michael; Boyce, Grady; Boyce, Pat

2016-01-01

CCD images were acquired of three binary star systems: WDS06145+1148, WDS06206+1803, and WDS06224+2640. The astrometric solution, position angle, and separation of each system were calculated with MaximDL v6 and Mira Pro x64 software suites. The results were consistent with historical measurements in the Washington Double Star Catalog. Our analysis found some differences in measurements between single-shot color CCD cameras and traditional monochrome CCDs using a filter wheel.

Quasi-Speckle Measurements of Close Double Stars With a CCD Camera

NASA Astrophysics Data System (ADS)

Harshaw, Richard

2017-01-01

CCD measurements of visual double stars have been an active area of amateur observing for several years now. However, most CCD measurements rely on “lucky imaging” (selecting a very small percentage of the best frames of a larger frame set so as to get the best “frozen” atmosphere for the image), a technique that has limitations with regards to how close the stars can be and still be cleanly resolved in the lucky image. In this paper, the author reports how using deconvolution stars in the analysis of close double stars can greatly enhance the quality of the autocorellogram, leading to a more precise solution using speckle reduction software rather than lucky imaging.

Patrick Moore's Data Book of Astronomy

NASA Astrophysics Data System (ADS)

Moore, Patrick; Rees, Robin

2014-01-01

1. The Solar System; 2. The Sun; 3. The Moon; 4. Mercury; 5. Venus; 6. Earth; 7. Mars; 8. The asteroid belt; 9. Jupiter; 10. Saturn; 11. Uranus; 12. Neptune; 13. Beyond Neptune: the Kuiper Belt; 14. Comets; 15. Meteors; 16. Meteorites; 17. Glows and atmospheric effects; 18. The stars; 19. Stellar spectra and evolution; 20. Extrasolar planets; 21. Double stars; 22. Variable stars; 23. Stellar clusters; 24. Nebulae; 25. The Galaxy; 26. The evolution of the Universe; 27. The constellations; 28. The star catalogue; 29. Telescopes and observatories; 30. Non-optical astronomy; 31. The history of astronomy; 32. Astronomers; 33. Glossary; Index.

Photometry of Faint and Wide Doubles in Vulpecula

NASA Astrophysics Data System (ADS)

Knapp, Wilfried; Thuemen, Chris

2016-04-01

Images of several double stars in Vulpecula published on the "Double Star Imaging Project" Yahoo Group page suggest magnitude issues compared with the corresponding WDS catalog data per April 2015. Taking additional images with V-filter enabled photometry for these pairs, providing confirming results.

Photometry of Faint and Wide Doubles in Sagitta

NASA Astrophysics Data System (ADS)

Knapp, Wilfried; Thuemen, Chris

2016-02-01

Images of several double stars in Sagitta published on the "Double Star Imaging Project" Yahoo Group page suggest magnitude issues compared with the corresponding WDS catalog data per April 2015. Taking additional images with V-filter enabled photometry for these pairs, provided confirming results.

Dynamic Studies of Struve Double Stars: STF4 and STF 236AB Appear Gravitationally Bound

NASA Astrophysics Data System (ADS)

Wiley, E. O.; Rica, F. M.

2015-01-01

Dynamics of two Struve double stars, WDS 00099+0827 (STF 4) and WDS 02556+2652 (STF 326 AB) are analyzed using astrometric criteria to determine their natures as gravitationally bound or unbound systems. If gravitationally bound, then observed relative velocity will be within limits according to the orbital energy conservation equation. Full implementation of this criterion was possible because the relative radial velocities as well as proper motions have been estimated. Other physical parameters were taken from literature or estimated using published protocols. Monte Carlo analysis indicates that both pairs have a high probability of being gravitationally bound and thus are long-period binaries.

Statistical studies in stellar rotation 2: A method of analyzing rotational coupling in double stars and an introduction to its applications

NASA Technical Reports Server (NTRS)

Bernacca, P. L.

1971-01-01

The correlation between the equatorial velocities of the components of double stars is studied from a statistical standpoint. A theory of rotational correlation is developed and discussed with regard to its applicability to existing observations. The theory is then applied to a sample of visual binaries which are the least studied for rotational coupling. Consideration of eclipsing systems and spectroscopic binaries is limited to show how the degrees of freedom in the spin parallelism problem can be reduced. The analysis lends support to the existence of synchronism in closely spaced binaries.

Photometry and Measurement of Faint and Wide Doubles in Eridanus

NASA Astrophysics Data System (ADS)

Knapp, Wilfried; Thuemen, Chris

2015-07-01

Images of several double stars in Eridanus published on the "Double Star Imaging Project" Yahoo Group page suggest magnitude issues compared with the corresponding WDS catalog data per 2014.12. Taking additional images with V-filter enabled photometry for these pairs with confirming results.

Velocity Curve Analysis of Spectroscopic Binary Stars AI Phe, GM Dra, HD 93917 and V502 Oph by Nonlinear Regression

NASA Astrophysics Data System (ADS)

Karami, K.; Mohebi, R.

2007-08-01

We introduce a new method to derive the orbital parameters of spectroscopic binary stars by nonlinear least squares of (o-c). Using the measured radial velocity data of the four double lined spectroscopic binary systems, AI Phe, GM Dra, HD 93917 and V502 Oph, we derived both the orbital and combined spectroscopic elements of these systems. Our numerical results are in good agreement with the those obtained using the method of Lehmann-Filhé.

Formation of Double Neutron Star Systems

NASA Astrophysics Data System (ADS)

Tauris, T. M.; Kramer, M.; Freire, P. C. C.; Wex, N.; Janka, H.-T.; Langer, N.; Podsiadlowski, Ph.; Bozzo, E.; Chaty, S.; Kruckow, M. U.; van den Heuvel, E. P. J.; Antoniadis, J.; Breton, R. P.; Champion, D. J.

2017-09-01

Double neutron star (DNS) systems represent extreme physical objects and the endpoint of an exotic journey of stellar evolution and binary interactions. Large numbers of DNS systems and their mergers are anticipated to be discovered using the Square Kilometre Array searching for radio pulsars, and the high-frequency gravitational wave detectors (LIGO/VIRGO), respectively. Here we discuss all key properties of DNS systems, as well as selection effects, and combine the latest observational data with new theoretical progress on various physical processes with the aim of advancing our knowledge on their formation. We examine key interactions of their progenitor systems and evaluate their accretion history during the high-mass X-ray binary stage, the common envelope phase, and the subsequent Case BB mass transfer, and argue that the first-formed NSs have accreted at most ˜ 0.02 {M}⊙ . We investigate DNS masses, spins, and velocities, and in particular correlations between spin period, orbital period, and eccentricity. Numerous Monte Carlo simulations of the second supernova (SN) events are performed to extrapolate pre-SN stellar properties and probe the explosions. All known close-orbit DNS systems are consistent with ultra-stripped exploding stars. Although their resulting NS kicks are often small, we demonstrate a large spread in kick magnitudes that may, in general, depend on the past interaction history of the exploding star and thus correlate with the NS mass. We analyze and discuss NS kick directions based on our SN simulations. Finally, we discuss the terminal evolution of close-orbit DNS systems until they merge and possibly produce a short γ-ray burst.

Photometry of Faint Wide Doubles in Hydra

NASA Astrophysics Data System (ADS)

Knapp, Wilfried; Thuemen, Chris; Gould, Ross

2015-11-01

Images of several double stars in Hydra published on the "Double Star Imaging Project" Yahoo Group page suggest magnitude issues compared with the corresponding WDS catalog data per end of 2014. Taking additional images with V and B filters enabled photometry for these pairs, suggesting significant corrections to the old data in WDS.

Effects of Neutron-Star Dynamic Tides on Gravitational Waveforms within the Effective-One-Body Approach

NASA Astrophysics Data System (ADS)

Hinderer, Tanja; Taracchini, Andrea; Foucart, Francois; Buonanno, Alessandra; Steinhoff, Jan; Duez, Matthew; Kidder, Lawrence E.; Pfeiffer, Harald P.; Scheel, Mark A.; Szilagyi, Bela; Hotokezaka, Kenta; Kyutoku, Koutarou; Shibata, Masaru; Carpenter, Cory W.

2016-05-01

Extracting the unique information on ultradense nuclear matter from the gravitational waves emitted by merging neutron-star binaries requires robust theoretical models of the signal. We develop a novel effective-one-body waveform model that includes, for the first time, dynamic (instead of only adiabatic) tides of the neutron star as well as the merger signal for neutron-star-black-hole binaries. We demonstrate the importance of the dynamic tides by comparing our model against new numerical-relativity simulations of nonspinning neutron-star-black-hole binaries spanning more than 24 gravitational-wave cycles, and to other existing numerical simulations for double neutron-star systems. Furthermore, we derive an effective description that makes explicit the dependence of matter effects on two key parameters: tidal deformability and fundamental oscillation frequency.

Effects of Neutron-Star Dynamic Tides on Gravitational Waveforms within the Effective-One-Body Approach.

PubMed

Hinderer, Tanja; Taracchini, Andrea; Foucart, Francois; Buonanno, Alessandra; Steinhoff, Jan; Duez, Matthew; Kidder, Lawrence E; Pfeiffer, Harald P; Scheel, Mark A; Szilagyi, Bela; Hotokezaka, Kenta; Kyutoku, Koutarou; Shibata, Masaru; Carpenter, Cory W

2016-05-06

Extracting the unique information on ultradense nuclear matter from the gravitational waves emitted by merging neutron-star binaries requires robust theoretical models of the signal. We develop a novel effective-one-body waveform model that includes, for the first time, dynamic (instead of only adiabatic) tides of the neutron star as well as the merger signal for neutron-star-black-hole binaries. We demonstrate the importance of the dynamic tides by comparing our model against new numerical-relativity simulations of nonspinning neutron-star-black-hole binaries spanning more than 24 gravitational-wave cycles, and to other existing numerical simulations for double neutron-star systems. Furthermore, we derive an effective description that makes explicit the dependence of matter effects on two key parameters: tidal deformability and fundamental oscillation frequency.

Student Measurements of Double Star STF 747AB

NASA Astrophysics Data System (ADS)

Bateman, Grace; Funk, Benjamin; Gillette, Travis; Rhoades, Breauna; Rhoades, Mark; Schlosser, Ruth; Sharpe, Scott; Thompson, Leone

2017-04-01

Data gathered from a 22-Inch Newtonian Alt/Az telescope and a Celestron Micro Guide eyepiece were used to measure the double star STF 747AB. Students from Apple Valley High School determined the separation to be 39.97 arc sec and the position angle to be 227.91 degrees. The students also used data from the digitized sky survey and determined a separation of 39.99 arc sec and a position angle of 225 degrees. The research was semi-independent from the Vanguard Double Star Workshop 2016 in Apple Valley, California.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Apellániz, J. Maíz; Sota, A.; Alfaro, E. J.

This is the third installment of the Galactic O-Star Spectroscopic Survey (GOSSS), a massive spectroscopic survey of Galactic O stars, based on new homogeneous, high signal-to-noise ratio, R  ∼ 2500 digital observations selected from the Galactic O-Star Catalog. In this paper, we present 142 additional stellar systems with O stars from both hemispheres, bringing the total of O-type systems published within the project to 590. Among the new objects, there are 20 new O stars. We also identify 11 new double-lined spectroscopic binaries, 6 of which are of O+O type and 5 of O+B type, and an additional new tripled-lined spectroscopic binary of O+O+Bmore » type. We also revise some of the previous GOSSS classifications, present some egregious examples of stars erroneously classified as O-type in the past, introduce the use of luminosity class IV at spectral types O4-O5.5, and adapt the classification scheme to the work of Arias et al.« less

Measuring Visual Double Stars with Robotic Telescopes

NASA Astrophysics Data System (ADS)

Boyce, Pat; Boyce, Grady; Genet, Russell M.; Faisal Al-Zaben, Dewei Li, Yongyao Li, Aren Dennis, Zhixin Cao, Junyao Li, Steven Qu, Jeff Li, Michael Fene, Allen Priest, Stephen Priest, Rex Qiu, , and, Bill Riley

2016-06-01

The Astronomy Research Seminars introduce students to scientific research by carrying out the entire process: planning a scientific research project, writing a research proposal, gathering and analyzing observational data, drawing conclusions, and presenting the research results in a published paper and presentation.In 2015 Cuesta College and Russell Genet sponsored a new hybrid format for the seminar enabling distance learning. Boyce Research Initiatives and Education Foundation (BRIEF) conducted the course at The Army and Navy Academy (ANA) in Carlsbad, California, in the spring and fall of 2015.The course objective is to complete the research and publish the paper within one semester. Our program schedule called for observations to be performed within a two week period. Measurement of visual binary stars was chosen because sufficient observations could be made in just two evenings of good weather. We quickly learned that our location by the ocean did not provide reliable weather to use local telescopes.The iTelescope network of robotic telescopes located in Australia, Spain and the U.S. solved the problem. Reservations for these systems are booked online and include date, time, exposure and filters. The high quality telescopes range from 4" to 27" in size with excellent cameras. By watching the weather forecasts for the sites, we were able to schedule our observations within the two week time frame required.Timely and reliable data reduction was the next hurdle. The students were using widely varying equipment (PCs, MACs, tablets, smart phones) with incompatible software. After wasting time trying to be computer technicians, we settled a on standard set of software relying on Mirametrics' Mira Pro x64. We installed the software on an old laptop, downloaded the iTelescope data files, gave the students remote access using GoToMyPC.These efficiencies enabled us to meet the demanding one semester schedule and assure a better learning experience. We have been able to produce four published research papers on seven visual double star systems and have our data added to the Washington Double Star Catalog. A school can adopt these techniques to do visual double star research with a minimal investment.

Measurements of Faint and Wide Doubles in Boötes and Corona Borealis

NASA Astrophysics Data System (ADS)

Knapp, Wilfried; Thuemen, Chris

2017-01-01

Images of several double stars in Boötes and Corona Borealis published on the “Double Star Imaging Project” Yahoo Group page suggest magnitude issues compared with the corresponding WDS catalog data per Jan 2016. Taking additional images with V-filter enabled photometry and astrometry for these pairs as a counter-check.

Vanguard Preparatory School Observations of the Double Star STF 1692

NASA Astrophysics Data System (ADS)

Anderson, Serenity; Buccola, Breck; Garcia, Karen; Gosney, Matthew; Housatchenko, Jonathan; Martinez, Lilian; Myskow, Wyatt; Renteria, Noah; Schlosser, Ruth; Thompson, Leone; Estrada, Reed; Estrada, Chris

2016-01-01

Using a 22-inch Newtonian Alt/Az telescope and a Celestron Micro Guide eyepiece, students from Vanguard Preparatory observed the binary star Cor Caroli (STF 1692) and found a position angle of 228 degrees as well as an average separation of 21.10". This project was a part of the Vanguard Preparatory Double Star Workshop 2015 in Apple Valley, California.

Discovery of Par 1802 as a Low-Mass, Pre-Main-Sequence Eclipsing Binary in the Orion Star-Forming Region

NASA Astrophysics Data System (ADS)

Cargile, P. A.; Stassun, K. G.; Mathieu, R. D.

2008-02-01

We report the discovery of a pre-main-sequence (PMS), low-mass, double-lined, spectroscopic, eclipsing binary in the Orion star-forming region. We present our observations, including radial velocities derived from optical high-resolution spectroscopy, and present an orbit solution that permits the determination of precise empirical masses for both components of the system. We find that Par 1802 is composed of two equal-mass (0.39 +/- 0.03, 0.40 +/- 0.03 M⊙) stars in a circular, 4.7 day orbit. There is strong evidence, such as the system exhibiting strong Li lines and a center-of-mass velocity consistent with cluster membership, that this system is a member of the Orion star-forming region and quite possibly the Orion Nebula Cluster, and therefore has an age of only a few million years. As there are currently only a few empirical mass and radius measurements for low-mass, PMS stars, this system presents an interesting test for the predictions of current theoretical models of PMS stellar evolution.

A new look inside planetary nebula LoTr 5: a long-period binary with hints of a possible third component

NASA Astrophysics Data System (ADS)

Aller, A.; Lillo-Box, J.; Vučković, M.; Van Winckel, H.; Jones, D.; Montesinos, B.; Zorotovic, M.; Miranda, L. F.

2018-05-01

LoTr 5 is a planetary nebula with an unusual long-period binary central star. As far as we know, the pair consists of a rapidly rotating G-type star and a hot star, which is responsible for the ionization of the nebula. The rotation period of the G-type star is 5.95 d and the orbital period of the binary is now known to be ˜2700 d, one of the longest in central star of planetary nebulae. The spectrum of the G central star shows a complex H α double-peaked profile which varies with very short time-scales, also reported in other central stars of planetary nebulae and whose origin is still unknown. We present new radial velocity observations of the central star which allow us to confirm the orbital period for the long-period binary and discuss the possibility of a third component in the system at ˜129 d to the G star. This is complemented with the analysis of archival light curves from Super Wide Angle Search for Planets, All Sky Automated Survey, and Optical Monitoring Camera. From the spectral fitting of the G-type star, we obtain an effective temperature of Teff = 5410 ± 250 K and surface gravity of log g = 2.7 ± 0.5, consistent with both giant and subgiant stars. We also present a detailed analysis of the H α double-peaked profile and conclude that it does not present correlation with the rotation period and that the presence of an accretion disc via Roche lobe overflow is unlikely.

Observations of the star Cor Caroli at the Apple Valley Workshop 2016

NASA Astrophysics Data System (ADS)

Estrada, Reed; Boyd, Sidney; Estrada, Chris; Evans, Cody; Rhoades, Hannah; Rhoades, Mark; Rhoades, Trevor

2017-06-01

Using a 22-inch Newtonian Alt/Az telescope and Celestron Micro Guide eyepiece, students participating in a workshop observed the binary star Cor Caroli (STF 1692) and found a position angle of 231.0 degrees as well as an average separation of 18.7" This observation compared favorably with the 2015 Washington Double Star published position. This project was part of Mark Brewer's Apple Valley Double Star Workshop. The results were analyzed using bias and circle error probability calculations.

RADIAL VELOCITY MONITORING OF KEPLER HEARTBEAT STARS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shporer, Avi; Fuller, Jim; Isaacson, Howard

2016-09-20

Heartbeat stars (HB stars) are a class of eccentric binary stars with close periastron passages. The characteristic photometric HB signal evident in their light curves is produced by a combination of tidal distortion, heating, and Doppler boosting near orbital periastron. Many HB stars continue to oscillate after periastron and along the entire orbit, indicative of the tidal excitation of oscillation modes within one or both stars. These systems are among the most eccentric binaries known, and they constitute astrophysical laboratories for the study of tidal effects. We have undertaken a radial velocity (RV) monitoring campaign of Kepler HB stars inmore » order to measure their orbits. We present our first results here, including a sample of 22 Kepler HB systems, where for 19 of them we obtained the Keplerian orbit and for 3 other systems we did not detect a statistically significant RV variability. Results presented here are based on 218 spectra obtained with the Keck/HIRES spectrograph during the 2015 Kepler observing season, and they have allowed us to obtain the largest sample of HB stars with orbits measured using a single instrument, which roughly doubles the number of HB stars with an RV measured orbit. The 19 systems measured here have orbital periods from 7 to 90 days and eccentricities from 0.2 to 0.9. We show that HB stars draw the upper envelope of the eccentricity–period distribution. Therefore, HB stars likely represent a population of stars currently undergoing high eccentricity migration via tidal orbital circularization, and they will allow for new tests of high eccentricity migration theories.« less

Spectroscopic and photometric analysis of NSV24512: an early-type eclipsing binary embedded in a dust cloud

NASA Astrophysics Data System (ADS)

Çakırlı, Ö.; Ibanoǧlu, C.; Southworth, J.; Frasca, A.; Hernandez, J.

2008-09-01

We present differential V-band photometric observations and the first radial velocities of NSV24512, which is embedded in the Serpens star-forming region. This double-lined system has an eccentric orbit with an eccentricity of 0.193. The system is a member of visual double star ADS11410AB with a separation of about 0.3 arcsec and an apparent visual magnitude difference of 0.125 mag; we find that the fainter component (component B) is responsible for the periodic light variation. Therefore, we subtracted the light contribution of component A from the total light. The V-band photometric data and radial velocities were then analysed simultaneously using the Wilson-Devinney program. From the blue-wavelength spectroscopic observations and radial velocities, we classify the primary and secondary components as B8V and B9V stars, respectively. The masses and radii of the component stars have been derived as 3.68 +/- 0.05 and 3.36 +/- 0.04Msolar and 3.21 +/- 0.05 and 2.93 +/- 0.05Rsolar, respectively. Comparison with theoretical evolutionary models indicates that both components are pre-main-sequence stars with an age of about 2.1 Myr. The projected rotational velocities of the components measured by us are much smaller than the synchronous rotational velocities. The high asynchronism is further evidence of the very young age of the system. Using the radiative properties of the stars, we have redetermined the distance to NSV24512 as 247 +/- 5 pc, which is in good agreement with, and more precise than, previous determinations. Adopting the same interstellar extinction and distance, we classify component A to be of spectral type B7, if it is a single star. Based on observations collected at Catania Astrophysical Observatory (Italy) and Ege University Observatory (Turkey). E-mail: omur.cakirli@gmail.com

A triangle voting algorithm based on double feature constraints for star sensors

NASA Astrophysics Data System (ADS)

Fan, Qiaoyun; Zhong, Xuyang

2018-02-01

A novel autonomous star identification algorithm is presented in this study. In the proposed algorithm, each sensor star constructs multi-triangle with its bright neighbor stars and obtains its candidates by triangle voting process, in which the triangle is considered as the basic voting element. In order to accelerate the speed of this algorithm and reduce the required memory for star database, feature extraction is carried out to reduce the dimension of triangles and each triangle is described by its base and height. During the identification period, the voting scheme based on double feature constraints is proposed to implement triangle voting. This scheme guarantees that only the catalog star satisfying two features can vote for the sensor star, which improves the robustness towards false stars. The simulation and real star image test demonstrate that compared with the other two algorithms, the proposed algorithm is more robust towards position noise, magnitude noise and false stars.

Warm debris disks candidates in transiting planets systems

NASA Astrophysics Data System (ADS)

Ribas, Á.; Merín, B.; Ardila, D. R.; Bouy, H.

2012-05-01

We have bandmerged candidate transiting planetary systems (from the Kepler satellite) and confirmed transiting planetary systems (from the literature) with the recent Wide-field Infrared Survey Explorer (WISE) preliminary release catalog. We have found 13 stars showing infrared excesses at either 12 μm and/or 22 μm. Without longer wavelength observations it is not possible to conclusively determine the nature of the excesses, although we argue that they are likely due to debris disks around the stars. If confirmed, our sample ~doubles the number of currently known warm excess disks around old main sequence stars. The ratios between the measured fluxes and the stellar photospheres are generally larger than expected for Gyr-old stars, such as these planetary hosts. Assuming temperature limits for the dust and emission from large dust particles, we derive estimates for the disk radii. These values are comparable to the planet's semi-major axis, suggesting that the planets may be stirring the planetesimals in the system.

Chico High School Students' Astrometric Observations of the Visual Double Star STF 1657

NASA Astrophysics Data System (ADS)

Ahiligwo, Jonelle; Bergamini, Clara; Berglund, Kallan; Bhardwaj, Mohit; Chelson, Spud; Costa, Amanda; Epis, Ashley; Grant, Azure; Osteen, Courtney; Reiner, Skyla; Rose, Adam; Schmidt, Emily; Sears, Forest; Sullivan-Hames, Maddie; Johnson, Jolyon

2012-01-01

In the spring of 2011, Chico Senior High School students participated in an astronomy seminar at the Gateway Science Museum, University of California, Chico. The observers used a Celestron NexStar 6 SE telescope and a Celestron MicroGuide eyepiece to determine the separation and position angle of the visual double star STF 1657. Observations were made in approximately one hour on the evening of May 1, 2011. The observers determined that the separation of STF 1657 was 22.1" and the position angle was 273.4&°. Seminar members then used the spectral type, parallax, and proper motion vectors of the two stars to determine if they are a line-of-sight optical pair or physically bound by gravity. Due to large errors in the parallax and the proper motion vector for the secondary star, the results were inconclusive. Through this experience, the students learned the skills needed to observe, analyze, and report on double stars.

Doubled-lined eclipsing binary system KIC~2306740 with pulsating component discovered from Kepler space photometry

NASA Astrophysics Data System (ADS)

Yakut, Kadri

2015-08-01

We present a detailed study of KIC 2306740, an eccentric double-lined eclipsing binary system with a pulsating component.Archive Kepler satellite data were combined with newly obtained spectroscopic data with 4.2\\,m William Herschel Telescope(WHT). This allowed us to determine rather precise orbital and physical parameters of this long period, slightly eccentric, pulsating binary system. Duplicity effects are extracted from the light curve in order to estimate pulsation frequencies from the residuals.We modelled the detached binary system assuming non-conservative evolution models with the Cambridge STARS(TWIN) code.

Documentation for the machine-readable version of the SAO-HD-GC-DM cross index version 1983

NASA Technical Reports Server (NTRS)

Roman, N. G.; Warren, W. H., Jr.; Schofield, N., Jr.

1983-01-01

An updated and extended machine readable version of the Smithsonian Astrophysical Observatory star catalog (SAO) is described. A correction of all errors which were found since preparation of the original catalog which resulted from misidentifications and omissions of components in multiple star systems and missing Durchmusterung numbers (the common identifier) in the SAO Catalog are included and component identifications from the Index of Visual Double Stars (IDS) are appended to all multiple SAO entries with the same DM numbers, and lower case letter identifiers for supplemental BD stars are added. A total of 11,398 individual corrections and data additions is incorporated into the present version of the cross index.

Spatially Resolved Imaging and Spectroscopy of Candidate Dual Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

McGurk, R. C.; Max, C. E.; Medling, A. M.; Shields, G. A.; Comerford, J. M.

2015-09-01

When galaxies merge, both central supermassive black holes are immersed in a dense and chaotic environment. If there is sufficient gas in the nuclear regions, one expects to see close pairs of active galactic nuclei (AGNs), or dual AGNs, in a fraction of galaxy mergers. However, finding them remains a challenge. The presence of double-peaked [O iii] emission lines has been proposed as a technique to select dual AGNs efficiently. We studied a sample of double-peaked narrow [O iii] emitting AGNs from Sloan Digital Sky Survey (SDSS) DR7. By obtaining new and archival high spatial resolution images taken with the Keck II Laser Guide Star Adaptive Optics system and the near-infrared camera NIRC2, we show that 30% of 140 double-peaked [O iii] emission line SDSS AGNs have two spatial components within a 3″ radius. However, spatially resolved spectroscopy or X-ray observations are needed to confirm these galaxy pairs as systems containing two AGNs. We followed up three spatially double candidate dual AGNs with integral field spectroscopy from Keck OSIRIS and 10 candidates with long-slit spectroscopy from the Shane Kast Double Spectrograph at Lick Observatory. We find that the double-peaked emission lines in our sample of 12 candidates are caused by: one dual AGN (SDSS J114642.47+511029.6), one confirmed outflow and four likely outflows, two pairs of star-forming galaxies, one candidate indeterminate due to sky line interference, and three AGNs with spatially coincident double [O iii] peaks, likely due to unresolved complex narrow line kinematics, outflows, binary AGN, or small-scale jets.

A Statistical Study of the Mass Distribution of Neutron Stars

NASA Astrophysics Data System (ADS)

Cheng, Zheng; Zhang, Cheng-Min; Zhao, Yong-Heng; Wang, De-Hua; Pan, Yuan-Yue; Lei, Ya-Juan

2014-07-01

By reviewing the methods of mass measurements of neutron stars in four different kinds of systems, i.e., the high-mass X-ray binaries (HMXBs), low-mass X-ray binaries (LMXBs), double neutron star systems (DNSs) and neutron star-white dwarf (NS-WD) binary systems, we have collected the orbital parameters of 40 systems. By using the boot-strap method and the Monte-Carlo method, we have rebuilt the likelihood probability curves of the measured masses of 46 neutron stars. The statistical analysis of the simulation results shows that the masses of neutron stars in the X-ray neutron star systems and those in the radio pulsar systems exhibit different distributions. Besides, the Bayes statistics of these four different kind systems yields the most-probable probability density distributions of these four kind systems to be (1.340 ± 0.230)M8, (1, 505 ± 0.125)M8,(1.335 ± 0.055)M8 and (1.495 ± 0.225)M8, respectively. It is noteworthy that the masses of neutron stars in the HMXB and DNS systems are smaller than those in the other two kind systems by approximately 0.16M8. This result is consistent with the theoretical model of the pulsar to be accelerated to the millisecond order of magnitude via accretion of approximately 0.2M8. If the HMXBs and LMXBs are respectively taken to be the precursors of the BNS and NS-WD systems, then the influence of the accretion effect on the masses of neutron stars in the HMXB systems should be exceedingly small. Their mass distributions should be very close to the initial one during the formation of neutron stars. As for the LMXB and NS-WD systems, they should have already under- gone the process of suffcient accretion, hence there arises rather large deviation from the initial mass distribution.

Young Star Probably Ejected From Triple System

NASA Astrophysics Data System (ADS)

2003-01-01

Astronomers analyzing nearly 20 years of data from the National Science Foundation's Very Large Array radio telescope have discovered that a small star in a multiple-star system in the constellation Taurus probably has been ejected from the system after a close encounter with one of the system's more-massive components, presumed to be a compact double star. This is the first time any such event has been observed. Path of Small Star, 1983-2001 "Our analysis shows a drastic change in the orbit of this young star after it made a close approach to another object in the system," said Luis Rodriguez of the Institute of Astronomy of the National Autonomous University of Mexico (UNAM). "The young star was accelerated to a large velocity by the close approach, and certainly now is in a very different, more remote orbit, and may even completely escape its companions," said Laurent Loinard, leader of the research team that also included Monica Rodriguez in addition to Luis Rodriguez. The UNAM astronomers presented their findings at the American Astronomical Society's meeting in Seattle, WA. The discovery of this chaotic event will be important for advancing our understanding of classical dynamic astronomy and of how stars evolve, including possibly providing an explanation for the production of the mysterious "brown dwarfs," the astronomers said. The scientists analyzed VLA observations of T Tauri, a multiple system of young stars some 450 light-years from Earth. The observations were made from 1983 to 2001. The T Tauri system includes a "Northern" star, the famous star that gives its name to the class of young visible stars, and a "Southern" system of stars, all orbiting each other. The VLA data were used to track the orbit of the smaller Southern star around the larger Southern object, presumed to be a pair of stars orbiting each other closely. The astronomers' plot of the smaller star's orbit shows that it followed an apparently elliptical orbit around its twin companions, moving at about 6 miles per second. Then, between 1995 and 1998, it came within about 200 million miles (about two times the distance between the Sun and the Earth) of its companions. Following that encounter, it changed its path, moving away from its companion at about 12 miles per second, double its previous speed. "We clearly see that this star's orbit has changed dramatically after the encounter with its larger companions," said Luis Rodriguez. "By watching over the next five years or so, we should be able to tell if it will escape completely," he added. "We are very lucky to have been able to observe this event," said Loinard. Though studies with computer simulations long have shown that such close approaches and stellar ejections are likely, the time scales for these events in the real Universe are long -- thousands of years. The chance to study an actual ejection of a star from a multiple system can provide a critical test for the dynamical theories. If a young star is ejected from the system in which it was born, it would be cut off from the supply of gas and dust it needs to gain more mass, and thus its development would be abruptly halted. This process, the astronomers explain, could provide an explanation for the very-low-mass "failed stars" called brown dwarfs. "A brown dwarf could have had its growth stopped by being ejected from its parent system," Loinard said. The VLA observations were made at radio frequencies of 8 and 15 GHz. T Tauri, the "Northern" star in this system, is a famous variable star, discovered in October of 1852 by J.R. Hind, a London astronomer using a 7-inch diameter telescope. At its brightest, it is some 40 times brighter than when at its faintest. It has been studied extensively as a nearby example of a young stellar system. While readily accessible with a small telescope, it is not visible to the naked eye. The observed orbital changes took place in the southern components of the system, displaced from the visible star by about one hundred times the distance between the Sun and the Earth. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Speckle interferometry at the OAN-SPM México: astrometry of double stars measured in 2011

NASA Astrophysics Data System (ADS)

Guerrero, C. A.; Orlov, V. G.; Borges Fernandes, M.; Ángeles, F.

2018-04-01

We present speckle interferometric measurements of binary stars performed during 2011 February and April with the 1.5-m telescope and during 2011 July and November with the 2.1-m telescope of the Observatorio Astronómico Nacional, San Pedro Mártir, México, focusing on objects from the Washington Double Star Catalog with separations less than 1 arcsec. Among these objects, we have been interested in performing a follow-up observation of new double stars discovered by Hipparcos. For these observations, we developed a new detector, which is a combination of CCD Watec 120N with a third generation image intensifier. This image intensifier allows us to perform near-infrared speckle interferometric observations for the first time. In this paper, we report 761 astrometric measurements of 478 pairs, with angular separations ranging from 0.09 to 2.61 arcsec. We found that 722 of our measured separations are smaller than 1 arcsec. We estimated a mean error in separation of 16 mas and 1.29° in position angle. In order to overcome the usual 180° ambiguity inherent to speckle measurements, we created a shift-and-add reconstructed image of each source, to establish the true quadrant of the secondary star. We confirmed 40 double stars discovered by Hipparcos and found 4 field stars resolved as interferometric pairs for the first time, with separations smaller than 0.60 arcsec.

Wide-Field Variability Survey of the Globular Cluster M 79 and a New Period-Luminosity Relation for SX Phe Stars

NASA Astrophysics Data System (ADS)

Kopacki, G.

2015-03-01

We present the results of a search for variable stars in a 26×39 arcmin2 field around globular cluster M 79 (NGC 1904). The search was made by means of an extended version of image subtraction, which allows us to analyze in a uniform manner CCD frames obtained with different telescopes and cameras of different sizes and resolutions. The search resulted in finding 20 new variable stars, among which 13 are cluster members. The members include one new RR Lyr star of subtype c, three SX Phe stars, and nine variable red giants. We also show that V7 is a W Vir star with a period of 13.985 d. Revised mean periods of RRab and RRc stars, ab=0.71 d and c=0.34 d, respectively, and relative percentage of RRc stars, Nc/(Nab+Nc)=45% confirm that M 79 belongs to the Oosterhoff II group of globular clusters. The mean V magnitude of the horizontal branch of M 79 based on ten RR Lyr stars has been estimated to be VHB=RR=16.11±0.03 mag. In one RRc star, V9, light changes with three close frequencies were detected, indicating excitation of nonradial modes. An SX Phe star, V18, is a double-mode pulsator with two radial modes excited, fundamental and first overtone. Moreover, we have discovered two SX Phe or δ Sct stars and one W UMa type system, all likely field objects. We also studied the period-luminosity relation for SX Phe stars. Using 62 fundamental and fundamentalized periods of radial double-mode and high-amplitude SX Phe stars known in Galactic globular clusters, we have derived the slope and zero point of this relation to be, -3.3±0.27 and 2.68±0.03 mag (at log(P/d)=-1.24), respectively.

Chromospherically active stars. 13: HD 30957: A double lined K dwarf binary

NASA Technical Reports Server (NTRS)

Fekel, Francis C.; Dadonas, Virgilijus; Sperauskas, Julius; Vaccaro, Todd R.; Patterson, L. Ronald

1994-01-01

HD 30957 is a double-lined spectroscopic binary with a period of 44.395 days and a modest eccentricity of 0.09. The spectral types of the components are K2-3 V and K5 V. The measured v sin i for both components is less than or equal to 3 km/s and the orbital inclination is estimated to be 69 deg. The system is relatively nearby with a parallax of 0.025 sec or a distance of 40 pc. Space motions of the system indicate that it does not belong to any of the known moving groups. Absolute surface fluxes of the Ca II H and K lines have been recomputed and indicate only modest chromospheric activity. If the stars are rotating pseudosynchronously, the lack of light variability is consistent with the value of the critical Rossby number for starspot activity.

A Speckle survey of Southern Hipparcos Visual Doubles and Geneva-Copenhagen Spectroscopic Binaries

NASA Astrophysics Data System (ADS)

Mendez, R. A.; Tokovinin, A.; Horch, E.

2018-01-01

We present a speckle survey of Hipparcos visual doubles and spectroscopic binary stars identified by the Geneva-Copenhagen spectroscopic survey with the SOAR 4m telescope + HRCam. These systems represent our best chance to take advantage of Gaia parallaxes for the purpose of stellar mass determinations. Many of these systems already have mass fractions (although generally no spectroscopic orbit - an astrometric orbit will determine individual masses), metallicity information, and Hipparcos distances. They will be used to improve our knowledge of the mass-luminosity relation, particularly for lower-metallicity stars. Our survey will create the first all-sky, volume-limited, speckle archive for the two primary samples, complementing a similar effort that has been recently been completed at the WIYN 3.5-m telescope in the Northern Hemisphere. This extension to the Southern Hemisphere will fill out the picture for a wider metallicity range.

Formation Mechanisms for Helium White Dwarfs in Binaries

NASA Astrophysics Data System (ADS)

Sandquist, E. L.; Taam, R. E.; Burkert, A.

1999-05-01

We discuss the constraints that can be placed on formation mechanisms for helium degenerate stars in binary systems, as well as the orbital parameters of the progenitor binaries, by using observed systems and numerical simulations of common envelope evolution. For pre-cataclysmic variable stars having a helium white dwarf, common envelope simulations covering the range of observed companion masses indicate that the initial mass of the red giant (parent of the white dwarf) can be constrained by the final period of the system. The formation mechanisms for double helium degenerate systems are also restricted. Using energy arguments, we find that there are almost no parameter combinations for which such a system can be formed using two successive common envelope phases. Observed short-period systems appear to favor an Algol-like phase of stable mass transfer followed by a common envelope phase. However, theory predicts that the brighter component is also the most massive, which is not observed in at least one system. This may require that nuclear burning must have occurred on the white dwarf that formed first, but after its formation. Systems which instead go through a common envelope episode, followed by a phase of nonconservative mass transfer from secondary to primary, would tend to form double degenerates with low mass ratios, which have not been observed to date. Finally, we discuss a new mechanism for producing subdwarf B stars in binaries. This work was supported by NSF grants AST-9415423 and AST-9727875.

Probing the properties of the pulsar wind via studying the dispersive effects in the pulses from the pulsar companion in a double neutron-star binary system

NASA Astrophysics Data System (ADS)

Yi, Shu-Xu; Cheng, K.-S.

2017-12-01

The velocity and density distribution of e± in the pulsar wind are crucial distinction among magnetosphere models, and contain key parameters determining the high-energy emission of pulsar binaries. In this work, a direct method is proposed, which might probe the properties of the wind from one pulsar in a double-pulsar binary. When the radio signals from the first-formed pulsar travel through the relativistic e± flow in the pulsar wind from the younger companion, the components of different radio frequencies will be dispersed. It will introduce an additional frequency-dependent time-of-arrival delay of pulses, which is function of the orbital phase. In this paper, we formulate the above-mentioned dispersive delay with the properties of the pulsar wind. As examples, we apply the formula to the double-pulsar system PSR J0737-3039A/B and the pulsar-neutron star binary PSR B1913+16. For PSR J0737-3039A/B, the time delay in 300 MHz is ≲ 10 μ s-1 near the superior conjunction, under the optimal pulsar wind parameters, which is approximately half of the current timing accuracy. For PSR B1913+16, with the assumption that the neutron-star companion has a typical spin-down luminosity of 1033 erg s-1, the time delay is as large as 10 - 20 μ s-1 in 300 MHz. The best timing precision of this pulsar is ∼ 5 μ s-1 in 1400 MHz. Therefore, it is possible that we can find this signal in archival data. Otherwise, we can set an upper limit on the spin-down luminosity. Similar analysis can be applied to other 11 known pulsar-neutron star binaries.

Dynamical investigations of the multiple stars

NASA Astrophysics Data System (ADS)

Kiyaeva, Olga V.; Zhuchkov, Roman Ya.

2017-11-01

Two multiple stars - the quadruple star - Bootis (ADS 9173) and the triple star T Taury were investigated. The visual double star - Bootiswas studied on the basis of the Pulkovo 26-inch refractor observations 1982-2013. An invisible satellite of the component A was discovered due to long-term uniform series of observations. Its orbital period is 20 ± 2 years. The known invisible satellite of the component B with near 5 years period was confirmed due to high precision CCD observations. The astrometric orbits of the both components were calculated. The orbits of inner and outer pairs of the pre-main sequence binary T Taury were calculated on the basis of high precision observations by the VLT and on the Keck II Telescope. This weakly hierarchical triple system is stable with probability more than 70%.

Time-Series Photometry of Variable Stars in the Globular Cluster NGC 288

NASA Astrophysics Data System (ADS)

Lee, Dong-Joo; Koo, Jae-Rim; Hong, Kyeongsoo; Kim, Seung-Lee; Lee, Jae Woo; Lee, Chung-Uk; Jeon, Young-Beom; Kim, Yun-Hak; Lim, Beomdu; Ryu, Yoon-Hyun; Cha, Sang-Mok; Lee, Yongseok; Kim, Dong-Jin; Park, Byeong-Gon; Kim, Chun-Hwey

2016-12-01

We present the results of BV time-series photometry of the globular cluster NGC 288. Observations were carried out to search for variable stars using the Korea Microlensing Telescope Network (KMTNet) 1.6-m telescopes and a 4k pre-science CCD camera during a test observation from August to December, 2014. We found a new SX Phe star and confirmed twelve previously known variable stars in NGC 288. For the semi-regular variable star V1, we newly determined a period of 37.3 days from light curves spanning 137 days. The light-curve solution of the eclipsing binary V10 indicates that the system is probably a detached system. The pulsation properties of nine SX Phe stars were examined by applying multiple frequency analysis to their light curves. We derived a new Period-Luminosity (P-L) relation, < M_{V} rangle = -2.476(±0.300) log P - 0.354(±0.385), from six SX Phe stars showing the fundamental mode. Additionally, the period ratios of three SX Phe stars that probably have a double-radial mode were investigated; P_{FO}/P_{F} = 0.779 for V5, P_{TO}/P_{FO} = 0.685 for V9, P_{SO}/P_{FO} = 0.811 for V11. This paper is the first contribution in a series assessing the detections and properties of variable stars in six southern globular clusters with the KMTNet system.

W134: A new pre-main-sequence double-lined spectroscopic binary

NASA Technical Reports Server (NTRS)

Padgett, Deborah L.; Stapelfeldt, Karl R.

1994-01-01

We report the discovery that the pre-main-sequence star Walker 134 in the young cluster NGC 2264 is a double-lined spectroscopic binary. Both components are G stars with strong Li I 6708 A absorption lines. Twenty radial velocity measurements have been used to determined the orbital elements of this system. The orbit has a period of 6.3532 +/- 0.0012 days and is circular within the limits of our velocity resolution; e less than 0.01. The total system mass is stellar mass sin(exp 3) i = 3.16 solar mass with a mass ratio of 1.04. Estimates for the orbit inclination angle and stellar radii place the system near the threshold for eclipse observability; howerver, no decrease in brightness was seen during two attempts at photometric monitoring. The circular orbit of W 134 fills an important gap in the period distribution of pre-main-sequence binaries and thereby constrains the effectiveness of tidal orbital circularization during the pre-main sequence.

Observations of the Star Cor Caroli at the Apple Valley Workshop 2016 (Abstract)

NASA Astrophysics Data System (ADS)

Estrada, R.; Boyd, S.; Estrada, C.; Evans, C.; Rhoades, H.; Rhoades, M.; Rhoades, T.

2017-12-01

(Abstract only) Using a 22-inch Newtonian Alt/Az telescope and Celestron Micro Guide eyepiece, students participating in a workshop observed the binary star Cor Caroli (STF 1692; alpha CVn) and found a position angle of 231.0 degrees as well as an average separation of 18.7" This observation compared favorably with the 2015 Washington Double Star published position. This project was part of Mark Brewer's Apple Valley Double Star Workshop. The results were analyzed using bias and circle error probability calculations.

CzeV293 and CzeV581-Two new high-amplitude double-mode delta Scuti stars

NASA Astrophysics Data System (ADS)

Skarka, M.; Cagaš, P.

2016-07-01

We report on the discovery of two high-amplitude double-mode delta Scuti stars in constellations of Hercules and Auriga. The stars were observed photometrically in five and two seasons, respectively. Frequency analysis revealed that both stars show complex pulsation behaviour with two independent modes and several combination peaks. Placing the stars into the Petersen diagram allowed us to identify the pulsation modes as the fundamental and the first overtone. Both stars follow the general trend for F/1O pulsators in the short-period part of the Petersen diagram and turned out to be classical members of HADS group of variables. Using empirical formulae we roughly estimate visual absolute magnitude, intrinsic (B - V) 0 colour index and temperature of the target stars.

Search for Type Ia supernova progenitors in open star clusters

NASA Astrophysics Data System (ADS)

Chakraborty, Subho

2013-12-01

Though Type Ia supernovae (henceforth SNae) are a primary tool in refining our understanding of cosmology and dark energy, controversies still abound regarding what the progenitors of these SNae are. The two main classes of possible Type Ia SN progenitors are: (1) the single-degenerate model, where a white dwarf (the remnant of a Sun-like star that has completed its life cycle) gravitationally accretes material from a close companion star, and (2) the double-degenerate model, involving the merger of two white dwarfs. In either case, the resulting SN explosion looks the same superficially. But some of the details of the SNae, perhaps including details critical to understanding dark energy, may depend sensitively on what the progenitors are. The goal of this thesis was to search for radial velocity variations in two candidate double degenerate systems. Firstly, I determined if either of these systems were bona fide double degenerates. I used the well-tested method of searching for radial velocity variations due to orbital motion as determined by changing Doppler shifts in their optical spectra. These data were obtained from time-series spectra of both candidate systems over several hours at the world's largest ground based optical telescope, the Keck Observatory in Hawaii. Secondly, I tested whether each confirmed binary system is of sufficient mass and sufficiently short orbital period to be progenitors of a future Type Ia SN. Binary white dwarfs that will merge to form Type IaSNae over a Hubble time have orbital periods less than six hours, which are easily detectable with these data. Type Ia SN progenitors must also have a mass near or above the Chandrasekhar limit of ~1.44 solar masses; the total mass of these systems can also be determined from our data. If one or both of these candidate systems had met both these criteria, the white dwarfs would have been the first definitive examples of the double degenerate class of Type Ia progenitors. This result, which we refer to as a positive result, would have been extremely important and highly impactful in astronomical research.

Twelve years of IUE spectra of the interacting binary VV Cephei

NASA Technical Reports Server (NTRS)

Bauer, W. H.; Stencel, R. E.; Neff, D. H.

1991-01-01

All well-exposed high-resolution IUE spectra obtained of the eclipsing binary system VV Cephei (M2Iabep + B) are examined. High-temperature absorption features attributable to the hot companion were detected, indicating that the companion (or the inner regions of its accretion disk) are not as hot as a B1-B2 star. Doubling of Fe II (UV 1) lines, with an additional narrow component redshifted by about 60 km/sec, occurs only when the B star is behind the plane of the sky containing the M supergiant, suggesting the existence of mass transfer from the red to the blue star. Absorption features from neutral elements weaken dramatically during egress, while those from ionized elements remain at nearly constant strength. During egress from primary eclipse, the Mg II resonance doublet shows asymmetric double-peaked emission indicative of formation in an expanding chromosphere. It is concluded that the outer atmosphere of the M supergiant is highly clumped.

Exclusion of a luminous red giant as a companion star to the progenitor of supernova SN 2011fe.

PubMed

Li, Weidong; Bloom, Joshua S; Podsiadlowski, Philipp; Miller, Adam A; Cenko, S Bradley; Jha, Saurabh W; Sullivan, Mark; Howell, D Andrew; Nugent, Peter E; Butler, Nathaniel R; Ofek, Eran O; Kasliwal, Mansi M; Richards, Joseph W; Stockton, Alan; Shih, Hsin-Yi; Bildsten, Lars; Shara, Michael M; Bibby, Joanne; Filippenko, Alexei V; Ganeshalingam, Mohan; Silverman, Jeffrey M; Kulkarni, S R; Law, Nicholas M; Poznanski, Dovi; Quimby, Robert M; McCully, Curtis; Patel, Brandon; Maguire, Kate; Shen, Ken J

2011-12-14

Type Ia supernovae are thought to result from a thermonuclear explosion of an accreting white dwarf in a binary system, but little is known of the precise nature of the companion star and the physical properties of the progenitor system. There are two classes of models: double-degenerate (involving two white dwarfs in a close binary system) and single-degenerate models. In the latter, the primary white dwarf accretes material from a secondary companion until conditions are such that carbon ignites, at a mass of 1.38 times the mass of the Sun. The type Ia supernova SN 2011fe was recently detected in a nearby galaxy. Here we report an analysis of archival images of the location of SN 2011fe. The luminosity of the progenitor system (especially the companion star) is 10-100 times fainter than previous limits on other type Ia supernova progenitor systems, allowing us to rule out luminous red giants and almost all helium stars as the mass-donating companion to the exploding white dwarf.

An RR Lyrae family portrait: 33 stars observed in Pisces with K2-E2

NASA Astrophysics Data System (ADS)

Molnár, L.; Szabó, R.; Moskalik, P. A.; Nemec, J. M.; Guggenberger, E.; Smolec, R.; Poleski, R.; Plachy, E.; Kolenberg, K.; Kolláth, Z.

2015-10-01

A detailed analysis is presented of 33 RR Lyrae stars in Pisces observed with the Kepler space telescope over the 8.9-d long K2 Two-Wheel Concept Engineering Test. The sample includes not only fundamental-mode and first-overtone (RRab and RRc) stars but the first two double-mode (RRd) stars that Kepler detected and the only modulated first-overtone star ever observed from space so far. The precision of the extracted K2 light curves made it possible to detect low-amplitude additional modes in all subtypes. All RRd and non-modulated RRc stars show the additional mode at PX/P1 ˜ 0.61 that was detected in previous space-based photometric measurements. A periodicity longer than the fundamental mode was tentatively identified in one RRab star that might belong to a gravity mode. We determined the photometric [Fe/H] values for all fundamental-mode stars and provide the preliminary results of our efforts to fit the double-mode stars with non-linear hydrodynamic pulsation models. The results from this short test run indicate that the K2 mission will be, and has started to be, an ideal tool to expand our knowledge about RR Lyrae stars. As a by-product of the target search and analysis, we identified 165 bona fide double-mode RR Lyrae stars from the Catalina Sky Survey observations throughout the sky, 130 of which are new discoveries.

Binary Star Fractions from the LAMOST DR4

NASA Astrophysics Data System (ADS)

Tian, Zhi-Jia; Liu, Xiao-Wei; Yuan, Hai-Bo; Chen, Bing-Qiu; Xiang, Mao-Sheng; Huang, Yang; Wang, Chun; Zhang, Hua-Wei; Guo, Jin-Cheng; Ren, Juan-Juan; Huo, Zhi-Ying; Yang, Yong; Zhang, Meng; Bi, Shao-Lan; Yang, Wu-Ming; Liu, Kang; Zhang, Xian-Fei; Li, Tan-Da; Wu, Ya-Qian; Zhang, Jing-Hua

2018-05-01

Stellar systems composed of single, double, triple or higher-order systems are rightfully regarded as the fundamental building blocks of the Milky Way. Binary stars play an important role in formation and evolution of the Galaxy. Through comparing the radial velocity variations from multi-epoch observations, we analyze the binary fraction of dwarf stars observed with LAMOST. Effects of different model assumptions, such as orbital period distributions on the estimate of binary fractions, are investigated. The results based on log-normal distribution of orbital periods reproduce the previous complete analyses better than the power-law distribution. We find that the binary fraction increases with T eff and decreases with [Fe/H]. We first investigate the relation between α-elements and binary fraction in such a large sample as provided by LAMOST. The old stars with high [α/Fe] dominate with a higher binary fraction than young stars with low [α/Fe]. At the same mass, earlier forming stars possess a higher binary fraction than newly forming ones, which may be related with evolution of the Galaxy.

An Upper Bound on Neutron Star Masses from Models of Short Gamma-Ray Bursts

NASA Astrophysics Data System (ADS)

Lawrence, Scott; Tervala, Justin G.; Bedaque, Paulo F.; Miller, M. Coleman

2015-08-01

The discovery of two neutron stars with gravitational masses ≈ 2 {M}⊙ has placed a strong lower limit on the maximum mass of nonrotating neutron stars, and with it a strong constraint on the properties of cold matter beyond nuclear density. Current upper mass limits are much looser. Here, we note that if most short gamma-ray bursts are produced by the coalescence of two neutron stars, and if the merger remnant collapses quickly, then the upper mass limit is constrained tightly. If the rotation of the merger remnant is limited only by mass-shedding (which seems probable based on numerical studies), then the maximum gravitational mass of a nonrotating neutron star is ≈ 2-2.2 {M}⊙ if the masses of neutron stars that coalesce to produce gamma-ray bursts are in the range seen in Galactic double neutron star systems. These limits would be increased by ˜4% in the probably unrealistic case that the remnants rotate at ˜30% below mass-shedding, and by ˜15% in the extreme case that the remnants do not rotate at all. Future coincident detection of short gamma-ray bursts with gravitational waves will strengthen these arguments because they will produce tight bounds on the masses of the components for individual events. If these limits are accurate, then a reasonable fraction of double neutron star mergers might not produce gamma-ray bursts. In that case, or in the case that many short bursts are produced instead by the mergers of neutron stars with black holes, the implied rate of gravitational wave detections will be increased.

Student Measurements of STFA 14 AC at Vanguard Preparatory School

NASA Astrophysics Data System (ADS)

Gillette, Sean; Archuleta, Alex; Diaz, Lizbeth; Gillespie, Kyle; Gosney, Timothy; Johnson, Stephen; Mohan, Nikita; Rajacich, Jacob; Roehl, Nathaniel; Sharpe, Scotty; Whitt, Kahaloha

2016-01-01

Eighth grade students at Vanguard Preparatory School measured the double star STFA 14 AC using a Bader Planetarium Micro Guide eyepiece. Navi (Gamma Cassiopeiae) was used as the ca libration star. The calculated means of multiple observations of STFA 14 AC resulted in a separation of 53.3" and a position angle of 2.0°. These measurements were compared to the most recent values in the Washington Double Star Catalog.

The doubling of stellar black hole nuclei

NASA Astrophysics Data System (ADS)

Kazandjian, Mher V.; Touma, J. R.

2013-04-01

It is strongly believed that Andromeda's double nucleus signals a disc of stars revolving around its central supermassive black hole on eccentric Keplerian orbits with nearly aligned apsides. A self-consistent stellar dynamical origin for such apparently long-lived alignment has so far been lacking, with indications that cluster self-gravity is capable of sustaining such lopsided configurations if and when stimulated by external perturbations. Here, we present results of N-body simulations which show unstable counter-rotating stellar clusters around supermassive black holes saturating into uniformly precessing lopsided nuclei. The double nucleus in our featured experiment decomposes naturally into a thick eccentric disc of apo-apse aligned stars which is embedded in a lighter triaxial cluster. The eccentric disc reproduces key features of Keplerian disc models of Andromeda's double nucleus; the triaxial cluster has a distinctive kinematic signature which is evident in Hubble Space Telescope observations of Andromeda's double nucleus, and has been difficult to reproduce with Keplerian discs alone. Our simulations demonstrate how the combination of an eccentric disc and a triaxial cluster arises naturally when a star cluster accreted over a preexisting and counter-rotating disc of stars drives disc and cluster into a mutually destabilizing dance. Such accretion events are inherent to standard galaxy formation scenarios. They are here shown to double stellar black hole nuclei as they feed them.

The Double Contact Nature of TT Herculis

NASA Astrophysics Data System (ADS)

Terrell, Dirk; Nelson, Robert H.

2014-03-01

We present new radial velocities and photometry of the short-period Algol TT Herculis. Previous attempts to model the light curves of the system have met with limited success, primarily because of the lack of a reliable mass ratio. Our spectroscopic observations are the first to result in radial velocities for the secondary star, and thus provide a spectroscopic mass ratio. Simultaneous analysis of the radial velocities and new photometry shows that the system is a double contact binary, with a rapidly rotating primary that fills its limiting lobe.

Siblings for SETI

NASA Astrophysics Data System (ADS)

Frisch, D.; Melia, F.

1983-09-01

The SAO Catalog of about 260,000 stars was studied to arrive at a sample of 'sibling', sun-like G-stars whose possible planetary systems' intelligent beings might feel drawn to single out each other for directional listening and broadcasting. A set of mostly untabulated sibling candidate stars can be defined, given a direction and a small solid angle that are mutually interesting to members of that set, so that overlapping broadcast/receiving cones can be selected on the basis of commonality. It is suggested that the double cone about the direction of the galactic center, whose half angle is 1/137 radian, is an almost inevitable choice in which sending and receiving with current technology can reach to about 1 kpsc, yielding an estimated 1000 G-star sibling candidates.

Einstein@Home Finds a Double Neutron Star

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-12-01

Have you been contributing your computer idle time to the Einstein@Home project? If so, youre partly responsible for the programs recent discovery of a new double-neutron-star system that will be key to learning about general relativity and stellar evolution.The 305-m Arecibo Radio Telescope, built into the landscape at Arecibo, Puerto Rico. [NOAO/AURA/NSF/H. Schweiker/WIYN]The Hunt for PulsarsObserving binary systems containing two neutron stars and in particular, measuring the timing of the pulses when one or both companions is a pulsar can provide highly useful tests of general relativity and binary stellar evolution. Unfortunately, these systems are quite rare: of 2500 known radio pulsars, only 14 of them are in double-neutron-starbinaries.To find more systems like these, we perform large-scale, untargeted radio-pulsar surveys like the ongoing Pulsar-ALFA survey conducted with the enormous 305-m radio telescope at Arecibo Observatory in Puerto Rico. But combing through these data for the signature of a highly accelerated pulsar (the acceleration is a clue that its in a compact binary) is very computationally expensive.PSR J1913+1102s L-band pulse profile, created by phase-aligning and summing all observations. [Adapted from Lazarus et al. 2016]To combat this problem, the Einstein@Home project was developed. Einstein@Home allows anyone to volunteer their personal computers idle time to help run the analysis of survey data in the search for pulsars. In a recent publication led by Patrick Lazarus (Max Planck Institute for Radio Astronomy), the Einstein@Home team announced the discovery of the pulsar PSR J1913+1102 a member of what seems to be a brand new double-neutron-starsystem.An Intriguing DiscoveryLazarus and collaborators followed up on the discovery to obtain timing measurements of the pulsar, which they found to have a spin period of 27.3 ms. They measured PSR J1913+1102 to be in a 4.95-hr, nearly circular (e 0.09) binary orbit with a massive companion that, based on its properties, is most likely another neutron star. The team wasnt able to detect pulsations from the companion, but that could mean that its beam doesnt cross the Earth, or its very faint, or its simply no longer active as a pulsar.Orbital evolution of the six known double-neutron-star systems that will coalesce within a Hubble time, including J1913+1102 (black solid line). They move toward the origin as they lose energy to gravitational waves and approach merger. Shown are current positions (black dots), estimates of the positions when the compact binaries were formed (grey dots), and future evolution. [Lazarus et al. 2016]Lazarus and collaborators use their observations of the system to arguethat PSR J1913+1102 waslikely spun up (recycled) by accretion of matter from its companions progenitor. The companion then exploded in the second supernova of the system, providing a very small kick hence the low eccentricity of the system and resulting in the current double-neutron-starbinary we observe.Lessons from PSR J1913+1102Observations of compact binaries such as this one can reveal a wealth of information. Besides providing clues about how the binary evolved, precise timing measurements (now being made) will also allow powerful tests of general relativity.One of the measurements that may be possible by the end of this year will provide information about the orbital decay of the binary expected to continue for 0.5 Gyr until the system merges due to the emission of gravitational waves.In the meantime, you can bet that Einstein@Home will continue hunting for more systems like PSR J1913+1102 and its companion!CitationP. Lazarus et al 2016 ApJ 831 150. doi:10.3847/0004-637X/831/2/150

Speckle Interferometry at Mount Wilson Observatory: Observations Obtained in 2006-2007 and 35 New Orbits

NASA Technical Reports Server (NTRS)

Hartkopf, William I.; Mason, Brian D.

2009-01-01

Results are presented for 607 speckle interferometric observations of double stars, as well as 222 measures of single stars or unresolved pairs. All data were obtained in 2006 and 2007 at the Mount Wilson Observatory, using the 2.5 m Hooker telescope. Separations range from 0.06 to 6.31, with a median of 0.34. These three observing runs concentrated on binaries in need of confirmation (mainly Hipparcos and Tycho pairs), as well as systems in need of improved orbital elements. New orbital solutions have been determined for 35 systems as a result.

Astrometric Measurements of Triple Star System 15379+3006 STF 1963AB, STF 1963AC

NASA Astrophysics Data System (ADS)

Russell, Harker; Miller, Lindsey; Beltzer-Sweeney, Alexander; Shilts, Trey; Stojimirovic, Irena

2018-04-01

Research team PRSM reports astrometric measurements of the double star system WDS 15379+3006 (STF 1963AB, STF 1963AC) obtained using the iTelescope Network. By performing CCD astrometry, the team determined a position angle of 298.4° ± 0.1° with an angular separation of 05. 28" ± 0.1" for STF 1963AB, and a position angle of 116.1° ± 0.1° with an angular separation of 32.35" ± 0.1" for STF 1963AC. The angular separation and position angle have changed from previous measurements.

Lithium and age of pre-main sequence stars: the case of Parenago 1802

NASA Astrophysics Data System (ADS)

Giarrusso, M.; Tognelli, E.; Catanzaro, G.; Degl'Innocenti, S.; Dell'Omodarme, M.; Lamia, L.; Leone, F.; Pizzone, R. G.; Prada Moroni, P. G.; Romano, S.; Spitaleri, C.

2016-04-01

With the aim to test the present capability of the stellar surface lithium abundance in providing an estimation for the age of PMS stars, we analyze the case of the detached, double-lined, eclipsing binary system PAR 1802. For this system, the lithium age has been compared with the theoretical one, as estimated by applying a Bayesian analysis method on a large grid of stellar evolutionary models. The models have been computed for several values of chemical composition and mixing length, by means of the code FRANEC updated with the Trojan Horse reaction rates involving lithium burning.

Classical Observations of Visual Binary and Multiple Stars

NASA Astrophysics Data System (ADS)

Mason, Brian D.

2007-08-01

The database of visual double star data has experienced tremendous changes, doubling in size during the last 25 years and growing at an ever increasing rate. Interferometric techniques have allowed the database to extend to much closer separation (and shorter periods), while longer timebases and higher-precision wide-field surveys have increased our knowledge of common proper motion pairs at the widest separations. These changes in the database are highlighted, describing the evolution of methods of observation (both historically and the past few years) and the effectiveness of these various methods in different regimes of separation/ period space. The various niches for wide- and narrow-field work as applied to double and multiple stars are examined and the different types of information which each can provide are also highlighted. After more than 20 years of successful work, speckle interferometry and conventional CCD astrometry have replaced filar micrometry and photography as the preferred classical techniques. Indeed, most work in filar micrometry is now being done by amateurs, although much of that community is also switching to CCDs and other electronic techniques. Despite the significant growth of the double star database, much still remains to be done, such as finding lost pairs, filling in missing parameters so that observing programs may be more efficient at observing stars appropriate to their capabilities, and providing at least approximate kinematic descriptions. Work on pairs described as neglected at the time of the last major WDS data release (2001) is given as a specific example of recent improvements, and finally the continued need to publish data using classical double star parameters is discussed.

Double Star Measurements Using a Webcam and CCD Camera, Annual Report of 2016

NASA Astrophysics Data System (ADS)

Schlimmer, Jeorg

2018-01-01

This report shows the results on 223 double star measurements from 2016; mini-mum separation is 1.23 a.s. (STF1024AB), maximum separation is 371 a.s. (STF1424AD). The mean value of all measurements is 18.7 a.s.

Searching for New Double Stars with a Computer

NASA Astrophysics Data System (ADS)

Bryant, T. V.

2015-04-01

The advent of computers with large amounts of RAM memory and fast processors, as well as easy internet access to large online astronomical databases, has made computer searches based on astrometric data practicable for most researchers. This paper describes one such search that has uncovered hitherto unrecognized double stars.

Obituary: Geoffrey Gardner Douglass, 1942-2005

NASA Astrophysics Data System (ADS)

Mason, Brian D.; Hartkopf, William; Corbin, Thomas

2005-12-01

Geoffrey Gardner Douglass passed away on 15 February 2005, following a long illness. Geoff was born 11 June 1942 in Rocky River, Ohio, and grew up there with a passion for science, theatre, and pets. He attended the nearby Case Institute of Technology (Cleveland, Ohio) before coming to the U.S. Naval Observatory on 28 April 1967. He worked at the USNO for over 30 years, until his retirement in January 1999. He was involved in the observing and measurement of parallax and double star plates on the SAMM and MANN measuring engines, and was stationed at Blenheim, New Zealand from 1985-1988 working at the Black Birch site on the Twin Astrograph Telescope. While there he and his wife Doris travelled extensively throughout New Zealand and Australia, He later worked with an early iteration of the USNO StarScan measuring machine. However, most of his work involved observations of visual double stars with the USNO 26-inch Clark Refractor, collaborating with F.J. ("Jerry") Josties on the photographic program in the late 1960s to the development of the USNO's speckle interferometry program throughout the 1990s. Geoff collaborated closely with Charles Worley from 1968 until Charles's death in December 1997, writing much of the double star software and assisting in the production of the USNO's double star catalogs. This was a period of transition, when some 200,000 punch cards of the Lick IDS (Index Catalog of Double Stars) were transferred from Lick Observatory to the USNO, then converted to magnetic tape. This ultimately resulted in the 1984 WDS catalog (currently maintained online). It was often joked that the "W" and "D" in the WDS (officially the "Washington Double Star" catalog) really stood for "Worley" and "Douglass." The "Curmudgeon" and the "Dour Scot" were a team for nearly thirty years. Geoff's first observation, of BU 442, was made 2 June 1967 with the USNO double star (photographic) camera, and his last, STF 342, was made on 28 November 1998 with the USNO speckle camera on the 26-inch refractor. In between he was an active collaborator and observer on these two different programs which, during his tenure at USNO, contributed over 18,000 measured positions to the WDS. While he discovered no new pairs, this was never his interest. He was much more interested in following up known systems and characterizing their motions to improve the catalog. During his long illness, even while at Cameron Glen Nursing Home, he continued to have an interest in the activities at the USNO and continued to be sought out for his knowledge on the instrumentation of the speckle camera. Late in 2004, when he was consulted on the location of a set of visual measures made in the early 1990s, his comment was that "every measure counted." During his last year at the observatory he oversaw the publication of over 10,000 speckle observations, and guided the recently hired Brian Mason (Charles's replacement) in the management of the double star program. Geoff battled illness for many years. He was a symbol of the worthiness of organ donation, living for some two decades following a kidney transplant, before succumbing to complications following the failure of the transplanted kidney. Geoff is survived by his wife, Doris, with whom he shared a love of cats and classical music. They touched many lives both at the Observatory and at their church, Graham Road United Methodist, where both he and Doris were active leaders in many ministries. Geoff was very passionate about his religious views, going so far as to name his old computer ``crux.'' Geoff will be sorely missed by his many friends and colleagues.

Speckle Interferometry with the OCA Kuhn 22" Telescope

NASA Astrophysics Data System (ADS)

Wasson, Rick

2018-04-01

Speckle interferometry measurements of double stars were made in 2015 and 2016, using the Kuhn 22-inch classical Cassegrain telescope of the Orange County Astronomers, a Point Grey Blackfly CMOS camera, and three interference filters. 272 observations are reported for 177 systems, with separations ranging from 0.29" to 2.9". Data reduction was by means of the REDUC and Speckle Tool Box programs. Equipment, observing procedures, calibration, data reduction, and analysis are described, and unusual results for 11 stars are discussed in detail.

IUE observations of the atmospheric eclipsing binary system Zeta Aurigae

NASA Technical Reports Server (NTRS)

Champman, R. D.

1980-01-01

IUE observations of the eclipsing binary system Zeta Aurigae made prior to and during the eclipse of the relatively small B8 V star by the cool supergiant star (spectral type K2 II) are reported. Spectral lines produced by the absorption of B star radiation in the atmosphere of the K star during eclipse can be used as a probe of the extended K star atmosphere, due to the negligible cool star continuum in the 1200-3200 A region. Spectra taken prior to eclipse are found to be similar to those of the single B8 V star 64 Ori, with the exception of very strong multi-component absorption lines of Si II, Si IV, C IV and the Mg resonance doublet with strong P Cygni profiles, indicating a double shell. Absorption lines including those corresponding to Al II, Al III, Cr II, Mn II, Fe II, Ni II and Ca II are observed to increase in strength and number as the eclipse progresses, with high-ionization-potential lines formed far from the K star, possibly in a shock wave, and low-ionization potential lines, formed in cool plasma, probably a cool wind, nearer to the K star. Finally, an emission-line spectra with lines corresponding to those previously observed in absorption is noted at the time the B-star continuum had disappeared.

Identification of stars in a J1744.0 star catalogue Yixiangkaocheng

NASA Astrophysics Data System (ADS)

Ahn, S.-H.

2012-05-01

The stars in the Chinese star catalogue, Yixiangkaocheng, which were edited by the Jesuit astronomer Kögler in AD 1744 and published in AD 1756, are identified with their counterparts in the Hipparcos catalogue. The equinox of the catalogue is confirmed to be J1744.0. By considering the precession of equinox, proper motions and nutation, the star closest to the location of each star in Yixiangkaocheng, having a proper magnitude, is selected as the corresponding identified star. I identified 2848 stars and 13 nebulosities out of 3083 objects in Yixiangkaocheng, and so the identification rate reached 92.80 per cent. I find that the magnitude classification system in Yixiangkaocheng agrees with the modern magnitude system. The catalogue includes dim stars, whose visual magnitudes are larger than 7, but most of these stars have Flamsteed designations. I find that the stars whose declination is lower than -30° have relatively larger offsets and different systematic behaviour from other stars. This indicates that there might be two different sources of stars in Yixiangkaocheng. In particular, I find that μ1 Sco and γ1 Sgr approximately mark the boundary between two different source catalogues. The observer's location, as estimated from these facts, agrees with the latitude of Greenwich where Flamsteed made his observations. The positional offsets between the Yixiangkaocheng stars and the Hipparcos stars are 0.6 arcmin, which implies that the source catalogue of stars with δ > -30° must have come from telescopic observations. Nebulosities in Yixiangkaocheng are identified with a few double stars, o Cet (the variable star, Mira), the Andromeda galaxy, ω Cen and NGC6231. These entities are associated with listings in Halley's Catalogue of the Southern Stars of AD 1679 as well as Flamsteed's catalogue of AD 1690.

Measurements of Beta Lyrae at the Pine Mountain Observatory Summer Workshop 2011

NASA Astrophysics Data System (ADS)

Carro, Joseph; Chamberlain, Rebecca; Schuler, Marisa; Varney, Timothy; Ewing, Robert; Genet, Russell

2012-04-01

As part of the Pine Mountain Observatory Summer Workshop 2011, high school and college students joined with an experienced observer to learn the use of a telescope, astrometric techniques, and measure a double star. This workshop was the first time these students operated a telescope, and, thus, constituted an educational experience for them as they used the telescope and took the measurements. The double star Beta Lyrae was measured resulting in a separation of 44.3 arc seconds and a position angle of 151.6 degrees. The Washington Double Star catalog (2009 data) lists a separation of 45.4 arc seconds and a position angle of 148 degrees.

Rule of Thumb Proposing the Size of Aperture Expected to be Sufficient to Resolve Double Stars with Given Parameters

NASA Astrophysics Data System (ADS)

Knapp, Wilfried

2018-01-01

Visual observation of double stars is an anachronistic passion especially attractive for amateurs looking for sky objects suitable for visual observation even in light polluted areas. Session planning then requires a basic idea which objects might be suitable for a given equipment—this question is a long term issue for visual double star observers and obviously not easy to answer, especially for unequal bright components. Based on a reasonably large database with limited aperture observations (done with variable aperture equipment iris diaphragm or aperture masks) a heuristic approach is used to derive a statistically well founded Rule of Thumb formula.

Light-curve and spectral properties of ultrastripped core-collapse supernovae leading to binary neutron stars

NASA Astrophysics Data System (ADS)

Moriya, Takashi J.; Mazzali, Paolo A.; Tominaga, Nozomu; Hachinger, Stephan; Blinnikov, Sergei I.; Tauris, Thomas M.; Takahashi, Koh; Tanaka, Masaomi; Langer, Norbert; Podsiadlowski, Philipp

2017-04-01

We investigate light-curve and spectral properties of ultrastripped core-collapse supernovae. Ultrastripped supernovae are the explosions of heavily stripped massive stars that lost their envelopes via binary interactions with a compact companion star. They eject only ˜0.1 M⊙ and may be the main way to form double neutron-star systems that eventually merge emitting strong gravitational waves. We follow the evolution of an ultrastripped supernova progenitor until iron core collapse and perform explosive nucleosynthesis calculations. We then synthesize light curves and spectra of ultrastripped supernovae using the nucleosynthesis results and present their expected properties. Ultrastripped supernovae synthesize ˜0.01 M⊙ of radioactive 56Ni, and their typical peak luminosity is around 1042 erg s-1 or -16 mag. Their typical rise time is 5-10 d. Comparing synthesized and observed spectra, we find that SN 2005ek, some of the so-called calcium-rich gap transients, and SN 2010X may be related to ultrastripped supernovae. If these supernovae are actually ultrastripped supernovae, their event rate is expected to be about 1 per cent of core-collapse supernovae. Comparing the double neutron-star merger rate obtained by future gravitational-wave observations and the ultrastripped supernova rate obtained by optical transient surveys identified with our synthesized light-curve and spectral models, we will be able to judge whether ultrastripped supernovae are actually a major contributor to the binary neutron-star population and provide constraints on binary stellar evolution.

Analysis of the multiple system with chemically peculiar component φ Draconis

NASA Astrophysics Data System (ADS)

Liška, J.

2016-09-01

The star ϕ Dra comprises a spectroscopic binary and a third star that together form a visual triple system. It is one of the brightest chemically peculiar stars of the upper main sequence. Despite these facts, no comprehensive study of its multiplicity has been performed yet. In this work, we present a detailed analysis of the triple system based on available measurements. We use radial velocities taken from four sources in the literature in a re-analysis of the inner spectroscopic binary (Aab). An incorrect value of the orbital period of the inner system Aab about 27 d was accepted in literature more than 40 yr. A new solution of orbit with the 128-d period was determined. Relative position measurements of the outer visual binary system (AB) from Washington Double Star Catalog were compared with known orbital models. Furthermore, it was shown that astrometric motion in system AB is well described by the model of Andrade with a 308-yr orbital period. Parameters of A and B components were utilized to estimate individual brightness for all components and their masses from evolutionary tracks. Although we found several facts which support the gravitational bond between them, unbound solution cannot be fully excluded yet.

Chromospherically active stars. 12: ADS 11060 C: A double lined K dwarf binary in a quintuple system

NASA Technical Reports Server (NTRS)

Fekel, Francis C.; Henry, Gregory W.; Hampton, Melissa L.; Fried, Robert; Morton, Mary D.

1994-01-01

ADS 11060 C is a double lined spectroscopic binary with a period of 25.7631 days and an eccentricity of 0.565. Spectral types of the two stars are estimated as K7 V and MO V with a magnitude difference of about 0.55 mag in V. The stars appear to be somewhat metal rich with respect to the Sun. Despite the relatively large masses of 0.53 and 0.51 solar mass, our photometric observations find no evidence for eclipses and we estimate an inclination of 77 deg plus or minus 11 deg. ADS 11060 C is, however, photometrically variable with a period of 9 plus or minus 1 day and an amplitude of 0.05 mag in V. Thus, it is a newly identified BY Draconis variable. The center-of-mass velocity of ADS 11060 C and an estimated parallax of 0.030 sec support its physical association with ADS 11060 AB, making this a quintuple system. The projected separation of the AB-C system is nearly 1200 AU. Although the log lithium abundances of the two components of ADS 11060 C are only upper limits, less than or equal to -0.14, lithium abundances of the AB-C components appear to be consistent with those of similar stars in the alpha Persei and Pleiades clusters, suggesting an age of about 70 Myr for ADS 11060 AB-C. The system is a possible member of the Pleiades moving group. Listed as an optical counterpart to a source in the ROSAT Wide Field Camera extreme-ultraviolet bright source catalog, both ADS 11060 AB and C may contribute to the observed flux.

Student Measurements of STFA 10AB (Theta Tauri)

NASA Astrophysics Data System (ADS)

Gillette, Sean; Estrada, Chris; Estrada, Reed; Aguilera, Sophia; Chavez, Valerie; Givens, Jalynn; Lindorfer, Sarah; Michels, Kaylie; Mobley, Makenzie; Reder, Gabriel; Renteria, Kayla; Shattles, Jenna; Wilkin, Aiden; Woodbury, Maisy; Rhoades, Breauna; Rhoades, Mark

2017-04-01

Eighth grade students at Vanguard Preparatory School measured the double star STFA 10AB using a 22-inch Newtonian Alt/Az telescope and a Celestron Micro Guide eyepiece. Bellatrix was used as the calibration star. The calculated means of multiple observations of STFA 10AB resulted in a separation of 45.18,” a scale constant of 7.88 arcseconds per division, and position angle of 257.9°. These measurements were compared to the most recent values in the Washington Double Star Catalog.

Wolf-Rayet stars in the Small Magellanic Cloud as testbed for massive star evolution

NASA Astrophysics Data System (ADS)

Schootemeijer, A.; Langer, N.

2018-03-01

Context. The majority of the Wolf-Rayet (WR) stars represent the stripped cores of evolved massive stars who lost most of their hydrogen envelope. Wind stripping in single stars is expected to be inefficient in producing WR stars in metal-poor environments such as the Small Magellanic Cloud (SMC). While binary interaction can also produce WR stars at low metallicity, it is puzzling that the fraction of WR binaries appears to be about 40%, independent of the metallicity. Aim. We aim to use the recently determined physical properties of the twelve known SMC WR stars to explore their possible formation channels through comparisons with stellar models. Methods: We used the MESA stellar evolution code to construct two grids of stellar models with SMC metallicity. One of these consists of models of rapidly rotating single stars, which evolve in part or completely chemically homogeneously. In a second grid, we analyzed core helium burning stellar models assuming constant hydrogen and helium gradients in their envelopes. Results: We find that chemically homogeneous evolution is not able to account for the majority of the WR stars in the SMC. However, in particular the apparently single WR star SMC AB12, and the double WR system SMC AB5 (HD 5980) appear consistent with this channel. We further find a dichotomy in the envelope hydrogen gradients required to explain the observed temperatures of the SMC WR stars. Shallow gradients are found for the WR stars with O star companions, while much steeper hydrogen gradients are required to understand the group of hot apparently single WR stars. Conclusions: The derived shallow hydrogen gradients in the WR component of the WR+O star binaries are consistent with predictions from binary models where mass transfer occurs early, in agreement with their binary properties. Since the hydrogen profiles in evolutionary models of massive stars become steeper with time after the main sequence, we conclude that most of the hot (Teff > 60 kK ) apparently single WR stars lost their envelope after a phase of strong expansion, e.g., as the result of common envelope evolution with a lower mass companion. The so far undetected companions, either main sequence stars or compact objects, are then expected to still be present. A corresponding search might identify the first immediate double black hole binary progenitor with masses as high as those detected in GW150914.

Stellar Astrophysics with a Dispersed Fourier Transform Spectrograph. II. Orbits of Double-lined Spectroscopic Binaries

NASA Astrophysics Data System (ADS)

Behr, Bradford B.; Cenko, Andrew T.; Hajian, Arsen R.; McMillan, Robert S.; Murison, Marc; Meade, Jeff; Hindsley, Robert

2011-07-01

We present orbital parameters for six double-lined spectroscopic binaries (ι Pegasi, ω Draconis, 12 Boötis, V1143 Cygni, β Aurigae, and Mizar A) and two double-lined triple star systems (κ Pegasi and η Virginis). The orbital fits are based upon high-precision radial velocity (RV) observations made with a dispersed Fourier Transform Spectrograph, or dFTS, a new instrument that combines interferometric and dispersive elements. For some of the double-lined binaries with known inclination angles, the quality of our RV data permits us to determine the masses M 1 and M 2 of the stellar components with relative errors as small as 0.2%.

Reassessing the fundamentals: On the evolution, ages and masses of neutron stars

NASA Astrophysics Data System (ADS)

Kiziltan, Bulent

The evolution, ages and masses of neutron stars are the fundamental threads that make pulsars accessible to other sub-disciplines of astronomy and physics. A realistic and accurate determination of these indirectly probed features play an important role in understanding a very broad range of astrophysical processes that are, in many cases, not empirically accessible otherwise. For the majority of pulsars, the only observables are the rotational period (P), and its derivative (P˙) which gives the rate of change in the spin. I start with calculating the joint P-P˙ distributions of millisecond pulsars for the standard evolutionary model in order to assess whether millisecond pulsars are the unequivocal descendants of low mass X-ray binaries. We show that the P-P˙ density implied by the standard evolutionary model is inconsistent with observations, which suggests that it is unlikely that millisecond pulsars have evolved from a single coherent progenitor population. In the absence of constraints from the binary companion or supernova remnant, the standard method for estimating pulsar ages is to infer an age from the rate of spin-down. I parametrically incorporate constraints that arise from binary evolution and limiting physics to derive a "modified spin-down age" for millisecond pulsars. We show that the standard method can be improved by this approach to achieve age estimates closer to the true age. Then, I critically review radio pulsar mass measurements and present a detailed examination through which we are able to put stringent constraints on the underlying neutron star mass distribution. For the first time, we are able to analyze a sizable population of neutron star-white dwarf systems in addition to double neutron star systems with a technique that accounts for systematically different measurement errors. We find that neutron stars that have evolved through different evolutionary paths reflect distinctive signatures through dissimilar distribution peak and mass cutoff values. Neutron stars in double neutron star and neutron star-white dwarf systems show consistent respective peaks at 1.35 M⊙ and 1.50 M⊙ , which suggest significant mass accretion (Deltam ≈ 0.15 M⊙ ) has occurred during the spin up phase. We find a mass cutoff at 2 M⊙ for neutron stars with white dwarf companions which establishes a firm lower bound for the maximum neutron star mass. This rules out the majority of strange quark and soft equation of state models as viable configurations for neutron star matter. The lack of truncation close to the maximum mass cutoff suggests that the 2 M⊙ limit is set by evolutionary constraints rather than nuclear physics or general relativity, and the existence of rare super-massive neutron stars is possible.

A Statistical Study on Neutron Star Masses

NASA Astrophysics Data System (ADS)

Cheng, Z.; Zhang, C. M.; Zhao, Y. H.; Wang, D. H.; Pan, Y. Y.; Lei, Y. J.

2013-11-01

We investigate the measurement of neutron star masses in different population of binaries. Based on the collection of the orbital parameters of 40 systems (46 sources), we apply the boot-strap method together with the Monte Carlo method to reconstruct the likelihood curves for each source separately. The cumulative analysis of the simulation result shows that the neutron star masses in X-ray systems and radio systems obey different distributions, and no evidence for the bimodal distribution could be found. Employing the Bayesian statistical techniques, we find that the most likely distributions for the high mass X-ray binaries (HMXBs), low mass X-ray binaries (LMXBs), double neutron star (DNS) systems, and neutron star-white dwarf (NS-WD) binary systems are (1.340±0.230) M_{⊙}, (1.505±0.125) M_{⊙}, (1.335±0.055) M_{⊙}, and (1.495±0.225) M_{⊙}, respectively. The statistical distribution has no significant deviation from the standard neutron star formation mechanism. It is noticed that the statistical results of the center masses of LMXBs and NS-WD systems are significantly higher than the other groups by about 0.16 M_{⊙}, which could be regarded as the evidence of accretion episodes. And if we regard the HMXBs and LMXBs as the progenitors of DNS and NS-WD systems, then we can draw the conclusion that the accretion effect must be very week during the evolution trajectory from HMXBs to DNS systems, and this could be the reason why the masses of DNS systems have such a narrow distribution.

Multiplicity among Solar-type Stars

NASA Astrophysics Data System (ADS)

Fuhrmann, K.; Chini, R.; Kaderhandt, L.; Chen, Z.

2017-02-01

We present a multiplicity census for a volume-complete all-sky survey of 422 stars with distances less than 25 pc and primary main-sequence effective temperatures T eff ≥ 5300 K. Very similar to previous results that have been presented for various subsets of this survey, we confirm the positive correlation of the stellar multiplicities with primary mass. We find for the F- and G-type Population I stars that 58% are non-single and 21% are in triple or higher level systems. For the old intermediate-disk and Population II stars—virtually all of G type and less massive—even two out of three sources prove to be non-single. These numbers being lower limits because of the continuous flow of new discoveries, the unbiased survey clearly demonstrates that the standard case for solar-type field stars is a hydrogen-burning source with at least one ordinary or degenerate stellar companion, and a surprisingly large number of stars are organized in multiple systems. A principal consequence is that orbital evolution, including the formation of blue straggler stars, is a potentially important issue on all spatial scales and timescales for a significant percentage of the stellar systems, in particular among Population II stars. We discuss a number of recent observations of known or suspected companions in the local survey, including a new detection of a double-lined Ba-Bb subsystem to the visual binary HR 8635.

X-RAY EMISSION FROM THE DOUBLE-BINARY OB-STAR SYSTEM QZ CAR (HD 93206)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parkin, E. R.; Naze, Y.; Rauw, G.

X-ray observations of the double-binary OB-star system QZ Car (HD 93206) obtained with the Chandra X-ray Observatory over a period of roughly 2 years are presented. The respective orbits of systems A (O9.7 I+b2 v, P{sub A} = 21 days) and B (O8 III+o9 v, P{sub B} = 6 days) are reasonably well sampled by the observations, allowing the origin of the X-ray emission to be examined in detail. The X-ray spectra can be well fitted by an attenuated three-temperature thermal plasma model, characterized by cool, moderate, and hot plasma components at kT {approx_equal} 0.2, 0.7, and 2 keV, respectively,more » and a circumstellar absorption of {approx_equal}0.2 x 10{sup 22} cm{sup -2}. Although the hot plasma component could be indicating the presence of wind-wind collision shocks in the system, the model fluxes calculated from spectral fits, with an average value of {approx_equal}7 x 10{sup -13} erg s{sup -1} cm{sup -2}, do not show a clear correlation with the orbits of the two constituent binaries. A semi-analytical model of QZ Car reveals that a stable momentum balance may not be established in either system A or B. Yet, despite this, system B is expected to produce an observed X-ray flux well in excess of the observations. If one considers the wind of the O8 III star to be disrupted by mass transfer, the model and observations are in far better agreement, which lends support to the previous suggestion of mass transfer in the O8 III + o9 v binary. We conclude that the X-ray emission from QZ Car can be reasonably well accounted for by a combination of contributions mainly from the single stars and the mutual wind-wind collision between systems A and B.« less

Discovery of a Highly Relativistic Double Neutron Star Binary

NASA Astrophysics Data System (ADS)

Chatterjee, Shami; Stovall, Kevin; PALFA Collaboration, Paul Demorest, Nihan Pol

2018-01-01

We report the discovery of a double neutron star (DNS) binary system, PSR J1946+2052, in Arecibo L-Band Feed Array Pulsar Survey (PALFA) observations. PSR J1946+2052 is a 17-ms pulsar in a 1.88-hour, eccentric (e = 0.06) orbit with a 1.2 solar mass companion. We have localized the pulsar to a precision of 0.09 arcseconds using a new phase binning mode at the Jansky Very Large Array. The improved position has enabled a measurement of the pulsar spin period derivative of 9E-19 s/s; the low inferred magnetic field strength at the surface of 4E+9 Gauss indicates that the pulsar has been recycled. Among all known DNS systems, PSR J1946+2052 has the shortest orbital period, and currently radiates ~13% of a solar luminosity in gravitational wave power. Its estimated time to merger is only 45.5 MYr, the shortest known, and at that time it will display the largest spin effects of any such system discovered to date. We have also measured the advance of periastron passage for this system, 25.6 +/- 0.3 degrees per year, resulting in a total system mass measurement of 2.50 +/- 0.04 solar masses.

NEW PRECISION ORBITS OF BRIGHT DOUBLE-LINED SPECTROSCOPIC BINARIES. V. THE AM STARS HD 434 AND 41 SEXTANTIS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fekel, Francis C.; Williamson, Michael H., E-mail: fekel@evans.tsuniv.ed

We have detected the secondary component in two previously known spectroscopic binaries, HD 434 and 41 Sex, and for the first time determined double-lined orbits for them. Despite the relatively long period of 34.26 days and a moderate eccentricity of 0.32, combined with the components' rotationally broadened lines, measurement of the primary and secondary radial velocities of HD 434 has enabled us to obtain significantly improved orbital elements. While the 41 Sex system has a much shorter period of 6.167 days and a circular orbit, the estimated V mag difference of 3.2 between its components also makes this a challengingmore » system. The new orbital dimensions (a{sub 1} sin i and a{sub 2} sin i) and minimum masses (m{sub 1} sin{sup 3} i and m{sub 2} sin{sup 3} i) of HD 434 have accuracies of 0.8% or better, while the same quantities for 41 Sex are good to 0.5% or better. Both components of HD 434 are Am stars while the Am star primary of 41 Sex has a late-F or early-G companion. All four stars are on the main sequence. The two components of HD 434 are rotating much faster than their predicted pseudosynchronous velocities, while both components of 41 Sex are synchronously rotating. For the primary of 41 Sex, the spectrum line depth changes noted by Sreedhar Rao et al. were not detected.« less

Three very cool degenerate stars in Luyten common proper motion binaries - Implications for the age of the galactic disk

NASA Technical Reports Server (NTRS)

Hintzen, Paul; Oswalt, Terry D.; Liebert, James; Sion, Edward M.

1989-01-01

During the course of a spectroscopic study of Luyten common proper motion (CPM) stars, spectrophotometric observations have been obtained of three binaries containing degenerate stars with estimated absolute magnitudes M(V) of about 16. Each of the three pairs consists of a yellow degenerate star primary and a DC 13 + secondary 1.4-2.3 mag fainter. One of the primary stars is spectral class DC 7, another is a sharp-lined DA 8, and the third shows peculiar broad absorption features which we interpret as pressure-shifted C2 Swan bands. The LP 701 - 69/70 system has survived for over 8 billion years without disruption by passing stars, despite its 1500 a.u. orbital major axis. The three cool degenerate companions nearly double the available sample of stars at the low-luminosity terminus of the white dwarf cooling sequence. These findings appear consistent with the conclusion that degenerate stars in the old disk population have not had time to evolve to a luminosity fainter than M(V) about 16.2.

Measurements of doubles stars made with a 12" telescope at courpiac observatory (French Title: Mesures d'étoiles doubles faites au télescope de 12 pouces de l'observatoire de courpiac)

NASA Astrophysics Data System (ADS)

Soulié, G.

2007-09-01

This paper contains 403 measures of double stars.These measures have been made with a 12",F/10 Meade LX 200 telescope and an X2 Barlow lens giving an effective focal length of about 5.5 meters. The calibration is calculated with measures of standard pairs. Frames have been obtained with a CCD camera MX516.

A gaseous metal disk around a white dwarf.

PubMed

Gänsicke, B T; Marsh, T R; Southworth, J; Rebassa-Mansergas, A

2006-12-22

The destiny of planetary systems through the late evolution of their host stars is very uncertain. We report a metal-rich gas disk around a moderately hot and young white dwarf. A dynamical model of the double-peaked emission lines constrains the outer disk radius to just 1.2 solar radii. The likely origin of the disk is a tidally disrupted asteroid, which has been destabilized from its initial orbit at a distance of more than 1000 solar radii by the interaction with a relatively massive planetesimal object or a planet. The white dwarf mass of 0.77 solar mass implies that planetary systems may form around high-mass stars.

Pulsar J1411+2551: A Low-mass Double Neutron Star System

NASA Astrophysics Data System (ADS)

Martinez, J. G.; Stovall, K.; Freire, P. C. C.; Deneva, J. S.; Tauris, T. M.; Ridolfi, A.; Wex, N.; Jenet, F. A.; McLaughlin, M. A.; Bagchi, M.

2017-12-01

In this work, we report the discovery and characterization of PSR J1411+2551, a new binary pulsar discovered in the Arecibo 327 MHz Drift Pulsar Survey. Our timing observations of the radio pulsar in the system span a period of about 2.5 years. This timing campaign allowed a precise measurement of its spin period (62.4 ms) and its derivative (9.6 ± 0.7) × 10‑20 s s‑1 from these, we derive a characteristic age of >9.1 Gyr and a surface magnetic field strength of <2.6 × 109 G. These numbers indicate that this pulsar was mildly recycled by accretion of matter from the progenitor of the companion star. The system has an eccentric (e = 0.17) 2.61 day orbit. This eccentricity allows a highly significant measurement of the rate of advance of periastron, \\dot{ω } =0.07686+/- 0.00046^\\circ {{yr}}-1. Assuming general relativity accurately describes the orbital motion, this implies a total system mass M = 2.538 ± 0.022 M ⊙. The minimum companion mass is 0.92 M ⊙ and the maximum pulsar mass is 1.62 M ⊙. The large companion mass and the orbital eccentricity suggest that PSR J1411+2551 is a double neutron star system; the lightest known to date including the DNS merger GW170817. Furthermore, the relatively low orbital eccentricity and small proper motion limits suggest that the second supernova had a relatively small associated kick; this and the low system mass suggest that it was an ultra-stripped supernova.

Studying the Pair WDS 01487+7528 = HJ 2075 AB Using the GAIA-DR1 Data

NASA Astrophysics Data System (ADS)

Romero, Francisco Rica

2018-01-01

In September 2016, the European Space Agency (ESA) released GAIA-DR1. ESA also published TGAS, a subset of Gaia source comprising those stars in the Hipparcos and Tycho-2 catalogs for which a full 5-parameters astrometric solution have been achieved. After publication of TGAS, the author decided to use the parallaxes and proper motions to review the double stars studied by LIADA’s Double Star Section during 2003. This year LIADA measured and studied 103 pairs of which only 10 have both stellar components listed in TGAS. Of those 10 pairs, 80% (8 double stars) are optical and only 2 are physical (with common parallaxes and proper motions).The main object of this work is a new study of HJ 2075 AB (WDS 01487+7528), located at 60 pc and composed of stars of 10.0 and 11.3 magnitudes with spectral types G8V and K4V separated by 31". This is a physical pair according to TGAS data (common parallaxes and proper motions).

The dynamical mass of a classical Cepheid variable star in an eclipsing binary system.

PubMed

Pietrzyński, G; Thompson, I B; Gieren, W; Graczyk, D; Bono, G; Udalski, A; Soszyński, I; Minniti, D; Pilecki, B

2010-11-25

Stellar pulsation theory provides a means of determining the masses of pulsating classical Cepheid supergiants-it is the pulsation that causes their luminosity to vary. Such pulsational masses are found to be smaller than the masses derived from stellar evolution theory: this is the Cepheid mass discrepancy problem, for which a solution is missing. An independent, accurate dynamical mass determination for a classical Cepheid variable star (as opposed to type-II Cepheids, low-mass stars with a very different evolutionary history) in a binary system is needed in order to determine which is correct. The accuracy of previous efforts to establish a dynamical Cepheid mass from Galactic single-lined non-eclipsing binaries was typically about 15-30% (refs 6, 7), which is not good enough to resolve the mass discrepancy problem. In spite of many observational efforts, no firm detection of a classical Cepheid in an eclipsing double-lined binary has hitherto been reported. Here we report the discovery of a classical Cepheid in a well detached, double-lined eclipsing binary in the Large Magellanic Cloud. We determine the mass to a precision of 1% and show that it agrees with its pulsation mass, providing strong evidence that pulsation theory correctly and precisely predicts the masses of classical Cepheids.

VizieR Online Data Catalog: Photometry of multiple stars at NAOR&ASV in 2015 (Cvetkovic+, 2017)

NASA Astrophysics Data System (ADS)

Cvetkovic, Z.; Pavlovic, R.; Boeva, S.

2018-05-01

This is the ninth series of CCD observations of double and multiple stars, obtained at the Bulgarian National Astronomical Observatory at Rozhen (NAOR) over five nights. As previously, the CCD camera VersArray 1300B was used, which was attached to the 2 m telescope. For each double or multiple star, five CCD frames in the Johnson B filter and five frames in the Johnson V filter were taken, which enabled us to determine the magnitude difference for these filters. In 2015 at the Astronomical Station at Vidojevica (ASV), over a total of 23 nights, observations were carried out by using the 60 cm telescope with a Cassegrain optical system. This is the fourth observational series at ASV since the work started there in 2011. In the observations we used the Apogee Alta U42 CCD camera whose characteristics can be found in the paper by Cvetkovic et al. (2016, J/AJ/151/58). Every pair was observed five times in the Cousins/Bessel B filter and five times in the Cousins/Bessel V one. (3 data files).

Double stars with wide separations in the AGK3 - II. The wide binaries and the multiple systems*

NASA Astrophysics Data System (ADS)

Halbwachs, J.-L.; Mayor, M.; Udry, S.

2017-02-01

A large observation programme was carried out to measure the radial velocities of the components of a selection of common proper motion (CPM) stars to select the physical binaries. 80 wide binaries (WBs) were detected, and 39 optical pairs were identified. By adding CPM stars with separations close enough to be almost certain that they are physical, a bias-controlled sample of 116 WBs was obtained, and used to derive the distribution of separations from 100 to 30 000 au. The distribution obtained does not match the log-constant distribution, but agrees with the log-normal distribution. The spectroscopic binaries detected among the WB components were used to derive statistical information about the multiple systems. The close binaries in WBs seem to be like those detected in other field stars. As for the WBs, they seem to obey the log-normal distribution of periods. The number of quadruple systems agrees with the no correlation hypothesis; this indicates that an environment conducive to the formation of WBs does not favour the formation of subsystems with periods shorter than 10 yr.

Online Meta-data Collection and Monitoring Framework for the STAR Experiment at RHIC

NASA Astrophysics Data System (ADS)

Arkhipkin, D.; Lauret, J.; Betts, W.; Van Buren, G.

2012-12-01

The STAR Experiment further exploits scalable message-oriented model principles to achieve a high level of control over online data streams. In this paper we present an AMQP-powered Message Interface and Reliable Architecture framework (MIRA), which allows STAR to orchestrate the activities of Meta-data Collection, Monitoring, Online QA and several Run-Time and Data Acquisition system components in a very efficient manner. The very nature of the reliable message bus suggests parallel usage of multiple independent storage mechanisms for our meta-data. We describe our experience with a robust data-taking setup employing MySQL- and HyperTable-based archivers for meta-data processing. In addition, MIRA has an AJAX-enabled web GUI, which allows real-time visualisation of online process flow and detector subsystem states, and doubles as a sophisticated alarm system when combined with complex event processing engines like Esper, Borealis or Cayuga. The performance data and our planned path forward are based on our experience during the 2011-2012 running of STAR.

Stars and Flowers, Flowers and Stars

NASA Astrophysics Data System (ADS)

Minti, Hari

2012-12-01

The author, a graduated from the Bucharest University (1964), actually living and working in Israel, concerns his book to variable stars and flowers, two domains of his interest. The analogies includes double stars, eclipsing double stars, eclipses, Big Bang. The book contains 34 chapters, each of which concerns various relations between astronomy and other sciences and pseudosciences such as Psychology, Religion, Geology, Computers and Astrology (to which the author is not an adherent). A special part of the book is dedicated to archeoastronomy and ethnoastronomy, as well as to history of astronomy. Between the main points of interest of these parts: ancient sanctuaries in Sarmizegetusa (Dacia), Stone Henge(UK) and other. The last chapter of the book is dedicated to flowers. The book is richly illustrated. It is designed for a wide circle of readers.

Embedded binaries and their dense cores

NASA Astrophysics Data System (ADS)

Sadavoy, Sarah I.; Stahler, Steven W.

2017-08-01

We explore the relationship between young, embedded binaries and their parent cores, using observations within the Perseus Molecular Cloud. We combine recently published Very Large Array observations of young stars with core properties obtained from Submillimetre Common-User Bolometer Array 2 observations at 850 μm. Most embedded binary systems are found towards the centres of their parent cores, although several systems have components closer to the core edge. Wide binaries, defined as those systems with physical separations greater than 500 au, show a tendency to be aligned with the long axes of their parent cores, whereas tight binaries show no preferred orientation. We test a number of simple, evolutionary models to account for the observed populations of Class 0 and I sources, both single and binary. In the model that best explains the observations, all stars form initially as wide binaries. These binaries either break up into separate stars or else shrink into tighter orbits. Under the assumption that both stars remain embedded following binary break-up, we find a total star formation rate of 168 Myr-1. Alternatively, one star may be ejected from the dense core due to binary break-up. This latter assumption results in a star formation rate of 247 Myr-1. Both production rates are in satisfactory agreement with current estimates from other studies of Perseus. Future observations should be able to distinguish between these two possibilities. If our model continues to provide a good fit to other star-forming regions, then the mass fraction of dense cores that becomes stars is double what is currently believed.

Common-envelope ejection in massive binary stars. Implications for the progenitors of GW150914 and GW151226

NASA Astrophysics Data System (ADS)

Kruckow, M. U.; Tauris, T. M.; Langer, N.; Szécsi, D.; Marchant, P.; Podsiadlowski, Ph.

2016-11-01

Context. The recently detected gravitational wave signals (GW150914 and GW151226) of the merger event of a pair of relatively massive stellar-mass black holes (BHs) calls for an investigation of the formation of such progenitor systems in general. Aims: We analyse the common-envelope (CE) stage of the traditional formation channel in binaries where the first-formed compact object undergoes an in-spiral inside the envelope of its evolved companion star and ejects the envelope in this process. Methods: We calculated envelope binding energies of donor stars with initial masses between 4 and 115M⊙ for metallicities of Z = ZMilky Way ≃ Z⊙/ 2 and Z = Z⊙/ 50, and derived minimum masses of in-spiralling objects needed to eject these envelopes. Results: In addition to producing double white dwarf and double neutron star binaries, CE evolution may also produce massive BH-BH systems with individual BH component masses of up to 50 - 60M⊙, in particular for donor stars evolved to giants beyond the Hertzsprung gap. However, the physics of envelope ejection of massive stars remains uncertain. We discuss the applicability of the energy-budget formalism, the location of the bifurcation point, the recombination energy, and the accretion energy during in-spiral as possible energy sources, and also comment on the effect of inflated helium cores. Conclusions: Massive stars in a wide range of metallicities and with initial masses of up to at least 115M⊙ may shed their envelopes and survive CE evolution, depending on their initial orbital parameters, similarly to the situation for intermediate- and low-mass stars with degenerate cores. In addition to being dependent on stellar radius, the envelope binding energies and λ-values also depend on the applied convective core-overshooting parameter, whereas these structure parameters are basically independent of metallicity for stars with initial masses below 60M⊙. Metal-rich stars ≳60M⊙ become luminous blue variables and do not evolve to reach the red giant stage. We conclude that based on stellar structure calculations, and in the view of the usual simple energy budget analysis, events like GW150914 and GW151226 might be produced by the CE channel. Calculations of post-CE orbital separations, however, and thus the estimated LIGO detection rates, remain highly uncertain.

Reconstructing merger timelines using star cluster age distributions: the case of MCG+08-11-002

NASA Astrophysics Data System (ADS)

Davies, Rebecca L.; Medling, Anne M.; U, Vivian; Max, Claire E.; Sanders, David; Kewley, Lisa J.

2016-05-01

We present near-infrared imaging and integral field spectroscopy of the centre of the dusty luminous infrared galaxy merger MCG+08-11-002, taken using the Near InfraRed Camera 2 (NIRC2) and the OH-Suppressing InfraRed Imaging Spectrograph (OSIRIS) on Keck II. We achieve a spatial resolution of ˜25 pc in the K band, allowing us to resolve 41 star clusters in the NIRC2 images. We calculate the ages of 22/25 star clusters within the OSIRIS field using the equivalent widths of the CO 2.3 μm absorption feature and the Br γ nebular emission line. The star cluster age distribution has a clear peak at ages ≲ 20 Myr, indicative of current starburst activity associated with the final coalescence of the progenitor galaxies. There is a possible second peak at ˜65 Myr which may be a product of the previous close passage of the galaxy nuclei. We fit single and double starburst models to the star cluster age distribution and use Monte Carlo sampling combined with two-sided Kolmogorov-Smirnov tests to calculate the probability that the observed data are drawn from each of the best-fitting distributions. There is a >90 per cent chance that the data are drawn from either a single or double starburst star formation history, but stochastic sampling prevents us from distinguishing between the two scenarios. Our analysis of MCG+08-11-002 indicates that star cluster age distributions provide valuable insights into the timelines of galaxy interactions and may therefore play an important role in the future development of precise merger stage classification systems.

Dynamical habitability of planetary systems.

PubMed

Dvorak, Rudolf; Pilat-Lohinger, Elke; Bois, Eric; Schwarz, Richard; Funk, Barbara; Beichman, Charles; Danchi, William; Eiroa, Carlos; Fridlund, Malcolm; Henning, Thomas; Herbst, Tom; Kaltenegger, Lisa; Lammer, Helmut; Léger, Alain; Liseau, René; Lunine, Jonathan; Paresce, Francesco; Penny, Alan; Quirrenbach, Andreas; Röttgering, Huub; Selsis, Frank; Schneider, Jean; Stam, Daphne; Tinetti, Giovanna; White, Glenn J

2010-01-01

The problem of the stability of planetary systems, a question that concerns only multiplanetary systems that host at least two planets, is discussed. The problem of mean motion resonances is addressed prior to discussion of the dynamical structure of the more than 350 known planets. The difference with regard to our own Solar System with eight planets on low eccentricity is evident in that 60% of the known extrasolar planets have orbits with eccentricity e > 0.2. We theoretically highlight the studies concerning possible terrestrial planets in systems with a Jupiter-like planet. We emphasize that an orbit of a particular nature only will keep a planet within the habitable zone around a host star with respect to the semimajor axis and its eccentricity. In addition, some results are given for individual systems (e.g., Gl777A) with regard to the stability of orbits within habitable zones. We also review what is known about the orbits of planets in double-star systems around only one component (e.g., gamma Cephei) and around both stars (e.g., eclipsing binaries).

A New Light Curve and Analysis of the Long Period Eclipsing Binary BF Draconis

NASA Astrophysics Data System (ADS)

Wolf, G. W.; Craig, L. E.; Caffey, J. F.

1999-01-01

The star BF Draconis was found to be an eclipsing binary by Strohmeier, Knigge and Ott (1962) and originally thought to be an Algol-type system with a period of 5.6 days. A spectrographic study by Imbert (1985) showed that the period was actually double this value and that the system consisted of two well-separated, almost-equal F-type stars in elliptical orbit. Diethelm, Wolf and Agerer (1993) later published a preliminary light curve of this system showing minima of unequal depth and width with a displaced secondary, confirming the elliptical orbit but disagreeing with Imbert on the specific orbital parameters. As a part of our long-term program of obtaining improved light curves of double-lined spectroscopic and eclipsing binaries, we have observed BF Draconis for the past four years using the 0.4 meter telescope at the Baker Observatory of Southwest Missouri State University. Complete light curves in the Cousins BVRI passbands have been obtained with our Photometrics CCD system, and a new model and orbital parameters for the binary have been determined using the Wilson-Devinney program. This research has been supported by NSF Grants AST-9315061 and AST-9605822 and NASA Grant NGT5-40060.

The magnetic field of the double-lined spectroscopic binary system HD 5550

NASA Astrophysics Data System (ADS)

Alecian, E.; Tkachenko, A.; Neiner, C.; Folsom, C. P.; Leroy, B.

2016-05-01

Context. The origin of fossil fields in intermediate- and high-mass stars is poorly understood, as is the interplay between binarity and magnetism during stellar evolution. Thus we have begun a study of the magnetic properties of a sample of intermediate-mass and massive short-period binary systems as a function of binarity properties. Aims: This paper specifically aims to characterise the magnetic field of HD 5550, a double-lined spectroscopic binary system of intermediate mass. Methods: We gathered 25 high-resolution spectropolarimetric observations of HD 5550 using the instrument Narval. We first fitted the intensity spectra using Zeeman/ATLAS9 LTE synthetic spectra to estimate the effective temperatures, microturbulent velocities, and the abundances of some elements of both components, as well as the light ratio of the system. We then applied the multi-line least-square deconvolution (LSD) technique to the intensity and circularly polarised spectra, which provided us with mean LSD I and V line profiles. We fitted the Stokes I line profiles to determine the radial and projected rotational velocities of both stars. We then analysed the shape and evolution of the V profiles using the oblique rotator model to characterise the magnetic fields of both stars. Results: We confirm the Ap nature of the primary, which has previously been reported, and find that the secondary displays spectral characteristics typical of an Am star. While a magnetic field is clearly detected in the lines of the primary, no magnetic field is detected in the secondary in any of our observations. If a dipolar field were present at the surface of the Am star, its polar strength must be below 40 G. The faint variability observed in the Stokes V profiles of the Ap star allowed us to propose a rotation period of 6.84-0.39+0.61 d, which is close to the orbital period (~6.82 d), suggesting that the star is synchronised with its orbit. By fitting the variability of the V profiles, we propose that the Ap component hosts a dipolar field inclined with the rotation axis at an angle β = 156 ± 17 ° and a polar strength Bd = 65 ± 20 G. The field strength is the weakest known for an Ap star. Based on the BinaMIcS Large Programme (PI: C. Neiner, runID: L131N02) obtained at the Telescope Bernard Lyot (USR5026) operated by the Observatoire Midi-Pyrénées, Université de Toulouse (Paul Sabatier), Centre National de la Recherche Scientifique of France.

East Meets West on "Double Star", a Joint Mission to Explore Earth's Magnetic Field

NASA Astrophysics Data System (ADS)

2001-07-01

ESA Director General Antonio Rodotà and Luan Enjie, Administrator of the CNSA, signed an official agreement that will enable European experiments to be flown on Chinese satellites for the first time. "This agreement marks a significant advance for international cooperation in the exploration and peaceful use of outer space," said Mr. Rodotà. "It is one of the most important landmarks in scientific collaboration since ESA and the People's Republic of China first agreed to exchange scientific information more than 20 years ago." "The Double Star programme will be just the first step in substantial cooperation between the Chinese National Space Administration and ESA" said Mr Luan Enjie. "The signing of today's agreement paves the way not only for reciprocal cooperation between scientists, but for the establishment of comprehensive cooperation between the two agencies". Double Star will follow in the footsteps of ESA's groundbreaking Cluster mission by studying the effects of the Sun on the Earth's environment. Conducting joint studies with Cluster and Double Star should increase the overall scientific return from both missions. A key aspect of ESA's participation in the Double Star project is the inclusion of 10 instruments that are identical to those currently flying on the four Cluster spacecraft. A further eight experiments will be provided by Chinese institutes. "We hope it will be possible to make coordinated measurements with both Cluster and Double Star." said Cluster Project Scientist Philippe Escoubet. "For example, we would hope to carry out a joint exploration of the magnetotail, a region where storms of high energy particles are generated. When these particles reach Earth, they can cause power cuts, damage satellites and disrupt communications." Six of the eleven Cluster principal investigators have agreed to provide flight spares or duplicates of the experiments that are currently revolutionising our understanding of near-Earth space. This reuse of Cluster instruments has a number of advantages for both European and Chinese scientists. "By flying experiments identical to those on Cluster, we can reduce costs and development time," explained Alberto Gianolio, ESA Project Manager for Double Star. "This will minimise risk and help us to ensure that we are able to meet the spacecraft development schedule." ESA has agreed to contribute 8 million euros to the Double Star programme. This funding will be used for refurbishment and pre-integration of the European instruments, acquisition of data for 4 hours per day and coordination of scientific operations. Notes for Editors: Double Star will be the first mission launched by China to explore the Earth's magnetosphere - the magnetic bubble that surrounds our planet. As its name suggests, Double Star will involve two satellites - each designed, developed, launched and operated by the CNSA - flying in complementary orbits around the Earth. This orbital configuration will enable scientists to obtain simultaneous data on the changing magnetic field and population of electrified particles in different regions of the magnetosphere. The duo is expected to be launched by Chinese Long March 2C rockets in December 2002 and March 2003. This schedule may enable them to operate alongside ESA's Cluster mission - a mini-flotilla of four identical spacecraft launched into elliptical orbits around the Earth last summer. The "equatorial" spacecraft (DSP-1) will be launched into an elliptical orbit of 550 x 60,000 km, inclined at 28.5 degrees to the equator. This will enable it to investigate the Earth's huge magnetic tail, the region where particles are accelerated towards the planet's magnetic poles by a process known as reconnection. The "polar" satellite (DSP-2) will concentrate on physical processes taking place over the magnetic poles and the development of aurorae. It will have a 350 x 25,000 km orbit taking it round the Earth once every 7.3 hours.

British variable star associations, 1848-1908

NASA Astrophysics Data System (ADS)

Toone, J.

2010-06-01

The study of variable stars lagged some distance behind solar system, positional (double star) and deep sky research until the middle part of the 19th century. Then, following F. W. A. Argelander's pioneering work in the 1840s, there was a striking increase in variable star research, particularly in Europe. The transformation was to such an extent that in the second half of the 19th century there were three attempts at forming variable star associations within Great Britain. The first in 1863 was the ASOVS, which never got off the ground. The second in 1883 was the LAS VSS, which was successfully launched but had somewhat limited achievements. The third launched in 1890 was the BAA VSS which was eventually both a resounding and lasting success. This paper is an outline history of these three associations up to a position of one hundred years ago (1908). [A summary version of this paper was presented at the joint meeting of the American Association of Variable Star Observers (AAVSO) and British Astronomical Association Variable Star Section (BAA VSS) held at Cambridge, UK, on 2008 April 11.

An estimate of the prevalence of biocompatible and habitable planets.

PubMed

Fogg, M J

1992-01-01

A Monte Carlo computer model of extra-solar planetary formation and evolution, which includes the planetary geochemical carbon cycle, is presented. The results of a run of one million galactic disc stars are shown where the aim was to assess the possible abundance of both biocompatible and habitable planets. (Biocompatible planets are defined as worlds where the long-term presence of surface liquid water provides environmental conditions suitable for the origin and evolution of life. Habitable planets are those worlds with more specifically Earthlike conditions). The model gives an estimate of 1 biocompatible planet per 39 stars, with the subset of habitable planets being much rarer at 1 such planet per 413 stars. The nearest biocompatible planet may thus lie approximately 14 LY distant and the nearest habitable planet approximately 31 LY away. If planets form in multiple star systems then the above planet/star ratios may be more than doubled. By applying the results to stars in the solar neighbourhood, it is possible to identify 28 stars at distances of < 22 LY with a non-zero probability of possessing a biocompatible planet.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parsons, S. G.; Marsh, T. R.; Gaensicke, B. T.

Using Liverpool Telescope+RISE photometry we identify the 2.78 hr period binary star CSS 41177 as a detached eclipsing double white dwarf binary with a 21,100 K primary star and a 10,500 K secondary star. This makes CSS 41177 only the second known eclipsing double white dwarf binary after NLTT 11748. The 2 minute long primary eclipse is 40% deep and the secondary eclipse 10% deep. From Gemini+GMOS spectroscopy, we measure the radial velocities of both components of the binary from the H{alpha} absorption line cores. These measurements, combined with the light curve information, yield white dwarf masses of M{sub 1}more » = 0.283 {+-} 0.064 M{sub sun} and M{sub 2} = 0.274 {+-} 0.034 M{sub sun}, making them both helium core white dwarfs. As an eclipsing, double-lined spectroscopic binary, CSS 41177 is ideally suited to measuring precise, model-independent masses and radii. The two white dwarfs will merge in roughly 1.1 Gyr to form a single sdB star.« less

Observations of Omicron 1 Cygni (STFA 50AD)

NASA Astrophysics Data System (ADS)

Bidler, Jeff; Hagee, Joshua; McGuire, Paul; McGuire, Rosa; Montes, Leslie; Richardson, Nicole; Rodriguez, Arturo; Brewer, Mark

2016-10-01

In over 215 years, the star STFA 50AD located in the Cygnus constellation has only been analyzed about 35 times. A group of eight individuals from five affiliations participated in the third annual Apple Valley Double Star Workshop to measure the separations and position angles of a double star. During this workshop, data from several astronomical identifiers was used to compare the data collected. The main apparatus used was an 8-inch telescope. An astrometric eyepiece and a stopwatch were used. The scale constant 9.9 arc seconds per division mark, separations 340.9 arc seconds, and position angles 324.1 degrees were determined by the telescope-eyepiece combination. The plate scale 1.01 arc seconds per pixel, separation 337.1 arc seconds, and position angle 321.3 degrees were determined by using the Digitized Sky Survey and Astrometrica. The results obtained were compared to previous observations listed in the Washington Double Star Catalog. After rigorous calculations and teamwork, it was concluded that the 2008 results were determined to be an outlier.

The Concise Knowledge Astronomy

NASA Astrophysics Data System (ADS)

Clerke, Agnes Mary; Fowler, Alfred; Ellard Gore, John

2011-01-01

Preface; Section I. History Agnes M. Clerke: 1. From Hipparchus to Laplace; 2. A century of progress; Section II. Geometrical Astronomy and Astronomical Instruments A. Fowler: 1. The Earth and its rotation; 2. The Earth's revolution round the Sun; 3. How the positions of the heavenly bodies are defined; 4. The Earth's orbit; 5. Mean solar time; 6. The movements of the Moon; 7. Movements of planets, satellites, and comets; 8. Eclipses and occultations; 9. How to find our situation on the Earth; 10. The exact size and shape of the earth; 11. The distances and dimensions of the heavenly bodies; 12. The masses of celestial bodies; 13. Gravitational effects of Sun and moon upon the Earth; 14. Instrumental measurement of angles and time; 15. Telescopes; 16. Instruments of precision; 17. Astrophysical instruments; Section III. The Solar System Agnes M. Clerke: 1. The solar system as a whole; 2. The Sun; 3. The Sun's surroundings; 4. The interior planets; 5. The Earth and Moon; 6. The planet Mars; 7. The asteroids; 8. The planet Jupiter; 9. The Saturnian system; 10. Uranus and Neptune; 11. Famous comets; 12. Nature and origin of comets; 13. Meteorites and shooting stars; Section IV. The Sidereal Heavens J.E. Gore: 1. The stars and constellations; 2. Double, multiple, and coloured stars; 3. The distances and motions of the stars; 4. Binary stars; 5. Variable and temporary stars; 6. Clusters and nebulae; 7. The construction of the heavens; Index.

Pulsars in binary systems: probing binary stellar evolution and general relativity.

PubMed

Stairs, Ingrid H

2004-04-23

Radio pulsars in binary orbits often have short millisecond spin periods as a result of mass transfer from their companion stars. They therefore act as very precise, stable, moving clocks that allow us to investigate a large set of otherwise inaccessible astrophysical problems. The orbital parameters derived from high-precision binary pulsar timing provide constraints on binary evolution, characteristics of the binary pulsar population, and the masses of neutron stars with different mass-transfer histories. These binary systems also test gravitational theories, setting strong limits on deviations from general relativity. Surveys for new pulsars yield new binary systems that increase our understanding of all these fields and may open up whole new areas of physics, as most spectacularly evidenced by the recent discovery of an extremely relativistic double-pulsar system.

Binary Lenses in OGLE-III EWS Database. Seasons 2002-2003

NASA Astrophysics Data System (ADS)

Jaroszynski, M.; Udalski, A.; Kubiak, M.; Szymanski, M.; Pietrzynski, G.; Soszynski, I.; Zebrun, K.; Szewczyk, O.; Wyrzykowski, L.

2004-06-01

We present 15 binary lens candidates from OGLE-III Early Warning System database for seasons 2002-2003. We also found 15 events interpreted as single mass lensing of double sources. The candidates were selected by visual light curves inspection. Examining the models of binary lenses of this and our previous study (10 caustic crossing events of OGLE-II seasons 1997--1999) we find one case of extreme mass ratio binary (q approx 0.005) and the rest in the range 0.1

TYC 5780-308-1 Discovery of Stellar Duplicity During Asteroidal Occultation by (834) Burnhamia

NASA Astrophysics Data System (ADS)

Timerson, Brad; George, T.; Blank, Ted; Maley, Paul; Messner, Steve; Moore, John

2018-04-01

An occultation of TYC 5780-308-1 by the asteroid (834) Burnhamia on August 23, 2017 (UT) showed this star to be a double star. Both components of the double star were occulted as recorded by four observers. The separation of the two components is 0.0143 ± 0.0004 arcseconds at a position angle of 73.8 ± 2.7 degrees. The magnitude of the primary component is estimated to be 9.8 +/- 0.03 (Tycho2 VT). The magnitude of the secondary component is estimated to be 9.92 +/- 0.03 (Tycho2 VT).

Recombination energy in double white dwarf formation

NASA Astrophysics Data System (ADS)

Nandez, J. L. A.; Ivanova, N.; Lombardi, J. C.

2015-06-01

In this Letter, we investigate the role of recombination energy during a common envelope event. We confirm that taking this energy into account helps to avoid the formation of the circumbinary envelope commonly found in previous studies. For the first time, we can model a complete common envelope event, with a clean compact double white dwarf binary system formed at the end. The resulting binary orbit is almost perfectly circular. In addition to considering recombination energy, we also show that between 1/4 and 1/2 of the released orbital energy is taken away by the ejected material. We apply this new method to the case of the double white dwarf system WD 1101+364, and we find that the progenitor system at the start of the common envelope event consisted of an ˜1.5 M⊙ red giant star in an ˜30 d orbit with a white dwarf companion.

Radial Velocities of 41 Kepler Eclipsing Binaries

NASA Astrophysics Data System (ADS)

Matson, Rachel A.; Gies, Douglas R.; Guo, Zhao; Williams, Stephen J.

2017-12-01

Eclipsing binaries are vital for directly determining stellar parameters without reliance on models or scaling relations. Spectroscopically derived parameters of detached and semi-detached binaries allow us to determine component masses that can inform theories of stellar and binary evolution. Here we present moderate resolution ground-based spectra of stars in close binary systems with and without (detected) tertiary companions observed by NASA’s Kepler mission and analyzed for eclipse timing variations. We obtain radial velocities and spectroscopic orbits for five single-lined and 35 double-lined systems, and confirm one false positive eclipsing binary. For the double-lined spectroscopic binaries, we also determine individual component masses and examine the mass ratio {M}2/{M}1 distribution, which is dominated by binaries with like-mass pairs and semi-detached classical Algol systems that have undergone mass transfer. Finally, we constrain the mass of the tertiary component for five double-lined binaries with previously detected companions.

Einstein@Home Discovery of a Double Neutron Star Binary in the PALFA Survey

NASA Astrophysics Data System (ADS)

Lazarus, P.; Freire, P. C. C.; Allen, B.; Aulbert, C.; Bock, O.; Bogdanov, S.; Brazier, A.; Camilo, F.; Cardoso, F.; Chatterjee, S.; Cordes, J. M.; Crawford, F.; Deneva, J. S.; Eggenstein, H.-B.; Fehrmann, H.; Ferdman, R.; Hessels, J. W. T.; Jenet, F. A.; Karako-Argaman, C.; Kaspi, V. M.; Knispel, B.; Lynch, R.; van Leeuwen, J.; Machenschalk, B.; Madsen, E.; McLaughlin, M. A.; Patel, C.; Ransom, S. M.; Scholz, P.; Seymour, A.; Siemens, X.; Spitler, L. G.; Stairs, I. H.; Stovall, K.; Swiggum, J.; Venkataraman, A.; Zhu, W. W.

2016-11-01

We report here the Einstein@Home discovery of PSR J1913+1102, a 27.3 ms pulsar found in data from the ongoing Arecibo PALFA pulsar survey. The pulsar is in a 4.95 hr double neutron star (DNS) system with an eccentricity of 0.089. From radio timing with the Arecibo 305 m telescope, we measure the rate of advance of periastron to be \\dot{ω }=5.632(18)° yr-1. Assuming general relativity accurately models the orbital motion, this corresponds to a total system mass of M tot = 2.875(14) {M}⊙ , similar to the mass of the most massive DNS known to date, B1913+16, but with a much smaller eccentricity. The small eccentricity indicates that the second-formed neutron star (NS) (the companion of PSR J1913+1102) was born in a supernova with a very small associated kick and mass loss. In that case, this companion is likely, by analogy with other systems, to be a light (˜1.2 {M}⊙ ) NS; the system would then be highly asymmetric. A search for radio pulsations from the companion yielded no plausible detections, so we cannot yet confirm this mass asymmetry. By the end of 2016, timing observations should permit the detection of two additional post-Keplerian parameters: the Einstein delay (γ), which will enable precise mass measurements and a verification of the possible mass asymmetry of the system, and the orbital decay due to the emission of gravitational waves ({\\dot{P}}b), which will allow another test of the radiative properties of gravity. The latter effect will cause the system to coalesce in ˜0.5 Gyr.

Unique Stellar System Gives Einstein a Thumbs-Up

NASA Astrophysics Data System (ADS)

2008-07-01

Taking advantage of a unique cosmic coincidence, astronomers have measured an effect predicted by Albert Einstein's theory of General Relativity in the extremely strong gravity of a pair of superdense neutron stars. The new data indicate that the famed physicist's 93-year-old theory has passed yet another test. Double Pulsar Graphic Artist's Conception of Double Pulsar System PSR J0737-3039A/B CREDIT: Daniel Cantin, DarwinDimensions, McGill University Click on image for more graphics. The scientists used the National Science Foundation's Robert C. Byrd Green Bank Telescope (GBT) to make a four-year study of a double-star system unlike any other known in the Universe. The system is a pair of neutron stars, both of which are seen as pulsars that emit lighthouse-like beams of radio waves. "Of about 1700 known pulsars, this is the only case where two pulsars are in orbit around each other," said Rene Breton, a graduate student at McGill University in Montreal, Canada. In addition, the stars' orbital plane is aligned nearly perfectly with their line of sight to the Earth, so that one passes behind a doughnut-shaped region of ionized gas surrounding the other, eclipsing the signal from the pulsar in back. "Those eclipses are the key to making a measurement that could never be done before," Breton said. Einstein's 1915 theory predicted that, in a close system of two very massive objects, such as neutron stars, one object's gravitational tug, along with an effect of its spinning around its axis, should cause the spin axis of the other to wobble, or precess. Studies of other pulsars in binary systems had indicated that such wobbling occurred, but could not produce precise measurements of the amount of wobbling. "Measuring the amount of wobbling is what tests the details of Einstein's theory and gives a benchmark that any alternative gravitational theories must meet," said Scott Ransom of the National Radio Astronomy Observatory. The eclipses allowed the astronomers to pin down the geometry of the double-pulsar system and track changes in the orientation of the spin axis of one of them. As one pulsar's spin axis slowly moved, the pattern of signal blockages as the other passed behind it also changed. The signal from the pulsar in back is absorbed by the ionized gas in the other's magnetosphere. Pulsars, first discovered in 1967, are the "corpses" of massive stars that have exploded as supernovae. What is left after the explosion is a superdense neutron star that packs more than the mass of our Sun into the size of an average city. Beams of radio waves stream outward from the poles of the star's intense magnetic field and sweep around as the star rotates, as often as hundreds of times a second. The pair of pulsars studied with the GBT is about 1700 light-years from Earth. The average distance between the two is only about twice the distance from the Earth to the Moon. The two orbit each other in just under two and a half hours. "A system like this, with two very massive objects very close to each other, is precisely the kind of extreme 'cosmic laboratory' needed to test Einstein's prediction," said Victoria Kaspi, leader of McGill University's Pulsar Group. Theories of gravity don't differ significantly in "ordinary" regions of space such as our own Solar System. In regions of extremely strong gravity fields, such as near a pair of close, massive objects, however, differences are expected to show up. In the binary-pulsar study, General Relativity "passed the test" provided by such an extreme environment, the scientists said. "It's not quite right to say that we have now 'proven' General Relativity," Breton said. "However, so far, Einstein's theory has passed all the tests that have been conducted, including ours." Breton, Kaspi and Ransom worked with Michael Kramer of the Jodrell Bank Observatory at the University of Manchester in Great Britain; Maura McLaughlin of West Virginia University and the NRAO; Maxim Lyutikov of Purdue University and other colleagues in Canada, the U.S., France and Italy. The researchers presented their work in an article in the July 4 issue of Science. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Elemental Abundances and their Implications for the Chemical Enrichment of the Boötes I Ultrafaint Galaxy

NASA Astrophysics Data System (ADS)

Gilmore, Gerard; Norris, John E.; Monaco, Lorenzo; Yong, David; Wyse, Rosemary F. G.; Geisler, D.

2013-01-01

We present a double-blind analysis of high-dispersion spectra of seven red giant members of the Boötes I ultrafaint dwarf spheroidal galaxy, complemented with re-analysis of a similar spectrum of an eighth-member star. The stars cover [Fe/H] from -3.7 to -1.9 and include a CEMP-no star with [Fe/H] = -3.33. We conclude from our chemical abundance data that Boötes I has evolved as a self-enriching star-forming system, from essentially primordial initial abundances. This allows us uniquely to investigate the place of CEMP-no stars in a chemically evolving system, in addition to limiting the timescale of star formation. The elemental abundances are formally consistent with a halo-like distribution, with enhanced mean [α/Fe] and small scatter about the mean. This is in accord with the high-mass stellar initial mass function in this low-stellar-density, low-metallicity system being indistinguishable from the present-day solar neighborhood value. There is a non-significant hint of a decline in [α/Fe] with [Fe/H]; together with the low scatter, this requires low star formation rates, allowing time for supernova ejecta to be mixed over the large spatial scales of interest. One star has very high [Ti/Fe], but we do not confirm a previously published high value of [Mg/Fe] for another star. We discuss the existence of CEMP-no stars, and the absence of any stars with lower CEMP-no enhancements at higher [Fe/H], a situation that is consistent with knowledge of CEMP-no stars in the Galactic field. We show that this observation requires there be two enrichment paths at very low metallicities: CEMP-no and "carbon-normal." Based on observations collected at the European Southern Observatory, Paranal, Chile (Proposal P82.182.B-0372, PI: G. Gilmore).

Constraints on the symmetry energy from neutron star observations

NASA Astrophysics Data System (ADS)

Newton, W. G.; Gearheart, M.; Wen, De-Hua; Li, Bao-An

2013-03-01

The modeling of many neutron star observables incorporates the microphysics of both the stellar crust and core, which is tied intimately to the properties of the nuclear matter equation of state (EoS). We explore the predictions of such models over the range of experimentally constrained nuclear matter parameters, focusing on the slope of the symmetry energy at nuclear saturation density L. We use a consistent model of the composition and EoS of neutron star crust and core matter to model the binding energy of pulsar B of the double pulsar system J0737-3039, the frequencies of torsional oscillations of the neutron star crust and the instability region for r-modes in the neutron star core damped by electron-electron viscosity at the crust-core interface. By confronting these models with observations, we illustrate the potential of astrophysical observables to offer constraints on poorly known nuclear matter parameters complementary to terrestrial experiments, and demonstrate that our models consistently predict L < 70 MeV.

On the Ultimate Fate of Massive Neutron Stars in an Ever Expanding Universe

NASA Astrophysics Data System (ADS)

Hujeirat, Ahmad A.

2018-01-01

General theory of relativity predicts the central densities of massive neutron stars (-MANs) to be much larger than the nuclear density. In the absence of energy production, the lifetimes of MANs should be shorter that their low-mass counterparts. Yet neither black holes nor neutron stars, whose masses are between two and five solar masses have ever been observed. Also, it is not clear what happened to the old MANs that were created through the collapse of first generation of stars shortly after the Big Bang. In this article, it is argued that MANs must end as completely invisible objects, whose cores are made of incompressible quark-gluon-superfluids and that their effective masses must have doubled through the injection of dark energy by a universal scalar field at the background of supranuclear density. It turns out that recent glitch observations of pulsars and young neutron star systems and data from particle collisions at the LHC and RHIC are in line with the presen! t scenario.

Alien Sunset (Artist Concept)

NASA Technical Reports Server (NTRS)

2007-01-01

Our solitary sunsets here on Earth might not be all that common in the grand scheme of things. New observations from NASA's Spitzer Space Telescope have revealed that mature planetary systems -- dusty disks of asteroids, comets and possibly planets -- are more frequent around close-knit twin, or binary, stars than single stars like our sun. That means sunsets like the one portrayed in this artist's photo concept, and more famously in the movie 'Star Wars,' might be quite commonplace in the universe.

Binary and multiple-star systems are about twice as abundant as single-star systems in our galaxy, and, in theory, other galaxies. In a typical binary system, two stars of roughly similar masses twirl around each other like pair-figure skaters. In some systems, the two stars are very far apart and barely interact with each other. In other cases, the stellar twins are intricately linked, whipping around each other quickly due to the force of gravity.

Astronomers have discovered dozens of planets that orbit around a single member of a very wide stellar duo. Sunsets from these worlds would look like our own, and the second sun would just look like a bright star in the night sky.

But do planets exist in the tighter systems, where two suns would dip below a planet's horizon one by one? Unveiling planets in these systems is tricky, so astronomers used Spitzer to look for disks of swirling planetary debris instead. These disks are made of asteroids, comets and possibly planets. The rocky material in them bangs together and kicks up dust that Spitzer's infrared eyes can see. Our own solar system is swaddled in a similar type of disk.

Surprisingly, Spitzer found more debris disks around the tightest binaries it studied (about 20 stars) than in a comparable sample of single stars. About 60 percent of the tight binaries had disks, while the single stars only had about 20 percent. These snug binary systems are as close or closer than just three times the distance between Earth and the sun. And the disks in these systems were found to circumnavigate both members of the star pair, rather than just one.

Though follow-up studies are needed, the results could mean that planet formation is more common around extra-tight binary stars than single stars. Since these types of systems would experience double sunsets, the artistic view portrayed here might not be fiction.

The original sunset photo used in this artist's concept was taken by Robert Hurt of the Spitzer Science Center at the California Institute of Technology, Pasadena, Calif.

An ancient eye test--using the stars.

PubMed

Bohigian, George M

2008-01-01

Vision testing in ancient times was as important as it is today. The predominant vision testing in some cultures was the recognition and identification of constellations and celestial bodies of the night sky. A common ancient naked eye test used the double star of the Big Dipper in the constellation Ursa Major or the Big Bear. The second star from the end of the handle of the Big Dipper is an optical double star. The ability to perceive this separation of these two stars, Mizar and Alcor, was considered a test of good vision and was called the "test" or presently the Arab Eye Test. This article is the first report of the correlation of this ancient eye test to the 20/20 line in the current Snellen visual acuity test. This article describes the astronomy, origin, history, and the practicality of this test and how it correlates with the present day Snellen visual acuity test.

VLA Reveals a Close Pair of Potential Planetary Systems

NASA Astrophysics Data System (ADS)

1998-09-01

Planets apparently can form in many more binary-star systems than previously thought, according to astronomers who used the National Science Foundation's Very Large Array (VLA) radio telescope to image protoplanetary disks around a close pair of stars. "Most stars in the universe are not alone, like our Sun, but are part of double or triple systems, so this means that the number of potential planets is greater than we realized," said Luis Rodriguez, of the National Autonomous University in Mexico City, who led an international observing team that made the discovery. The astronomers announced their results in the Sept. 24 issue of the scientific journal Nature. The researchers used the VLA to study a stellar nursery - a giant cloud of gas and dust - some 450 light-years distant in the constellation Taurus, where stars the size of the Sun or smaller are being formed. They aimed at one particular object, that, based on previous infrared and radio observations, was believed to be a very young star. The VLA observations showed that the object was not a single young star but a pair of young stars, separated only slightly more than the Sun and Pluto. The VLA images show that each star in the pair is surrounded by an orbiting disk of dust, extending out about as far as the orbit of Saturn. Such dusty disks are believed to be the material from which planets form. Similar disks are seen around single stars, but the newly-discovered disks around the stars in the binary system are about ten times smaller, their size limited by the gravitational effect of the other, nearby star. Their existence indicates, however, that such protoplanetary disks, though truncated in size, still can survive in such a close double-star system. "It was surprising to see these disks in a binary system with the stars so close together," said Rodriguez. "Each of these disks contains enough mass to form a solar system like our own," said David Wilner, of the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA. "However, we don't think these solar systems would be able to form outer, icy planets like Uranus and Neptune, because of the small size of the dust disks." The new observations "imply that young protoplanetary disks can contain considerably more mass within (a distance equal to Saturn's orbital radius) than astronomers have been willing to contemplate," wrote Alan P. Boss of the Carnegie Institution of Washington in an accompanying Nature article analyzing the results. If the stars were a few times closer together, the researchers point out, the gravitational effects of both would disrupt the disks and prevent any planets from forming. "If these disks form planetary systems, they would be among the closest possible adjacent sets of planets in the universe," said Rodriguez. Boss suggested that a giant planet formed near the edge of one of the disks might be ejected from the system by the gravitational effect of the companion star. This, he says, might explain the possible "runaway planet" shown in a Hubble Space Telescope image released in May. In that result, a planet appears to have been ejected by a binary-star system similar in size to that seen by the VLA. Further observations are required to confirm that result. In addition to Rodriguez and Wilner, the researchers are Paola D'Alessio, Salvador Curiel, Yolanda Gomez, Susana Lizano, Jorge Canto, and Alejandro C. Raga of the National Autonomous University in Mexico City; Paul Ho of the Harvard-Smithsonian Center for Astrophysics; Jose M. Torrelles of the Astrophysical Institute of Andalucia in Spain; and Alan Pedlar of the Jodrell Bank observatory in Britain. The observations of the double-star system were made at a radio wavelength of 7 millimeters, a wavelength at which emission from cosmic dust is readily detected. Astronomers long realized that the VLA had sufficient resolving power - the ability to see fine detail - to make images of the dust disks around young stars that form the building blocks of planets. Until 1993, however, the VLA could not do so because it had no receivers that worked at the required wavelength, 7 mm. Rodriguez, an experienced VLA observer interested in how planetary systems form, obtained a $1 million grant in 1992 from Mexico's National Science and Technology Foundation (Spanish acronym CONACyT) to allow the National Radio Astronomy Observatory (NRAO) to build such receivers for 13 of the VLA's 27 230-ton dish antennas. Those receivers were built and installed in 1993 and 1994, and now are used by numerous observers, including Rodriguez. With these receivers, the VLA images show 10 times more detail than any previous observations at these wavelengths. "This research proves how valuable these receivers are in increasing the scientific capability of the VLA," said Miller Goss, NRAO's director of VLA operations. "In fact, this type of work is one reason the U.S. National Science Foundation is providing the money to equip the rest of the VLA's antennas with the same kind of receivers." The additional receivers will greatly improve the quality of images for complex objects, including planetary systems in formation, said NRAO astronomer Rick Perley. "We plan a major upgrade to all aspects of the VLA in the next few years," Perley said. "The VLA upgrade will mean that astronomers using this wavelength can find about 60 times more objects of any particular type and make better images of them. That improves the chances of finding rare objects, which often are the signposts pointing to new insights into physics." The VLA is an instrument of the National Radio Astronomy Observatory, a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Using DOUBLE STAR and CLUSTER Synoptic Observations to Test Global MHD Simulations of the Large-scale Topology of the Dayside Merging Region

NASA Astrophysics Data System (ADS)

Berchem, J.; Marchaudon, A.; Bosqued, J.; Escoubet, C. P.; Dunlop, M.; Owen, C. J.; Reme, H.; Balogh, A.; Carr, C.; Fazakerley, A. N.; Cao, J. B.

2005-12-01

Synoptic measurements from the DOUBLE STAR and CLUSTER spacecraft offer a unique opportunity to evaluate global models in simulating the complex topology and dynamics of the dayside merging region. We compare observations from the DOUBLE STAR TC-1 and CLUSTER spacecraft on May 8, 2004 with the predictions from a three-dimensional magnetohydrodynamic (MHD) simulation that uses plasma and magnetic field parameters measured upstream of the bow shock by the WIND spacecraft. Results from the global simulation are consistent with the large-scale features observed by CLUSTER and TC-1. We discuss topological changes and plasma flows at the dayside magnetospheric boundary inferred from the simulation results. The simulation shows that the DOUBLE STAR spacecraft passed through the dawn side merging region as the IMF rotated. In particular, the simulation indicates that at times TC-1 was very close to the merging region. In addition, we found that the bifurcation of the merging region in the simulation results is consistent with predictions by the antiparallel merging model. However, because of the draping of the magnetosheath field lines over the magnetopause, the positions and shape of the merging region differ significantly from those predicted by the model.

Double Star Research: A Student-Centered Community of Practice

NASA Astrophysics Data System (ADS)

Johnson, Jolyon

2016-06-01

Project and team-based pedagogies are increasingly augmenting lecture-style science classrooms. Occasionally, university professors will invite students to tangentially partcipate in their research. Since 2006, Dr. Russ Genet has led an astronomy research seminar for community college and high school students that allows participants to work closely with a melange of professional and advanced amatuer researchers. The vast majority of topics have centered on measuring the position angles and searations of double stars which can be readily published in the Journal of Double Star Observations. In the intervening years, a collaborative community of practice (Wenger, 1998) formed with the students as lead researchers on their projects with the guidance of experienced astronomers and educators. The students who join the research seminar are often well prepared for further STEM education in college and career. Today, the research seminar involves multile schools in multiple states with a volunteer educator acting as an assistant instructor at each location. These assistant instructors interface with remote observatories, ensure progress is made, and recruit students. The key deliverables from each student team include a published research paper and a public presentation online or in-person. Citing a published paper on scholarship and college applications gives students' educational carreers a boost. Recently the Journal of Double Star Observations published its first special issue of exlusively student-centered research.

DO R CORONAE BOREALIS STARS FORM FROM DOUBLE WHITE DWARF MERGERS?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Staff, Jan. E.; Clayton, Geoffrey C.; Tohline, Joel E.

2012-09-20

A leading formation scenario for R Coronae Borealis (RCB) stars invokes the merger of degenerate He and CO white dwarfs (WDs) in a binary. The observed ratio of {sup 16}O/{sup 18}O for RCB stars is in the range of 0.3-20 much smaller than the solar value of {approx}500. In this paper, we investigate whether such a low ratio can be obtained in simulations of the merger of a CO and a He WD. We present the results of five three-dimensional hydrodynamic simulations of the merger of a double WD system where the total mass is 0.9 M{sub Sun} and themore » initial mass ratio (q) varies between 0.5 and 0.99. We identify in simulations with q {approx}< 0.7 a feature around the merged stars where the temperatures and densities are suitable for forming {sup 18}O. However, more {sup 16}O is being dredged up from the C- and O-rich accretor during the merger than the amount of {sup 18}O that is produced. Therefore, on the dynamical timescale over which our hydrodynamics simulation runs, an {sup 16}O/{sup 18}O ratio of {approx}2000 in the 'best' case is found. If the conditions found in the hydrodynamic simulations persist for 10{sup 6} s the oxygen ratio drops to 16 in one case studied, while in a hundred years it drops to {approx}4 in another case studied, consistent with the observed values in RCB stars. Therefore, the merger of two WDs remains a strong candidate for the formation of these enigmatic stars.« less

Chromospherically active stars. X - Spectroscopy and photometry of HD 212280

NASA Technical Reports Server (NTRS)

Fekel, Francis C.; Browning, Jared C.; Henry, Gregory W.; Morton, Mary D.; Hall, Douglas S.

1993-01-01

The system HD 212280 is a chromospherically active double lined spectroscopic binary with an orbital period of 45.284 days and an eccentricity of 0.50. The spectrum is composite with spectral types of G8 IV and F5-8 V for the components. An estimated inclination of 78 +/- 8 deg results in masses of 1.7 and 1.4 solar mass for the G subgiant and mid-F star, respectively. The distance to the system is estimated to be 112 pc. Photometric observations obtained between 1987 November and 1992 June reveal that HD 212280 is a newly identified variable star with a V amplitude of about 0.15 mag and a mean period of 29.46 days. Our V data were divided into 11 sets and in all but one case two spots were required to fit the data. Lifetimes of 650 days and a minimum of 1350 days have been determined for two of the four spots. The differential rotation coefficient of 0.05 is relatively small. The age of the system is about 1.9 X 10 exp 9 yrs. The G subgiant is rotating slower than pseudosynchronously while the F-type star is rotating faster.

Nearby Dwarf Stars: Duplicity, Binarity, and Masses

NASA Astrophysics Data System (ADS)

Mason, Brian D.; Hatkopf, William I.; Raghavan, Deepak

2008-02-01

Double stars have proven to be both a blessing and a curse for astronomers since their discovery over two centuries ago. They remain the only reliable source of masses, the most fundamental parameter defining stars. On the other hand, their sobriquet ``vermin of the sky'' is well-earned, due to the complications they present to both observers and theoreticians. These range from non-linear proper motions to stray light in detectors, to confusion in pointing of instruments due to non-symmetric point spread functions, to angular momentum conservation in multiple stars which results in binaries closer than allowed by evolution of two single stars. This proposal is an effort to address both their positive and negative aspects, through speckle interferometric observations, targeting ~1200 systems where useful information can be obtained with only a single additional observation. The proposed work will refine current statistics regarding duplicity (chance alignments of nearby point sources) and binarity (actual physical relationships), and improve the precisions and accuracies of stellar masses. Several targets support Raghavan's Ph.D. thesis, which is a comprehensive survey aimed at determining the multiplicity fraction among solar-type stars.

Nearby Dwarf Stars: Duplicity, Binarity, and Masses

NASA Astrophysics Data System (ADS)

Mason, Brian D.; Hartkopf, William I.; Raghavan, Deepak

2007-08-01

Double stars have proven to be both a blessing and a curse for astronomers since their discovery over two centuries ago. They remain the only reliable source of masses, the most fundamental parameter defining stars. On the other hand, their sobriquet ``vermin of the sky'' is well-earned, due to the complications they present to both observers and theoreticians. These range from non-linear proper motions to stray light in detectors, to confusion in pointing of instruments due to non-symmetric point spread functions, to angular momentum conservation in multiple stars which results in binaries closer than allowed by evolution of two single stars. This proposal is an effort to address both their positive and negative aspects, through speckle interferometric observations, targeting ~1200 systems where useful information can be obtained with only a single additional observation. The proposed work will refine current statistics regarding duplicity (chance alignments of nearby point sources) and binarity (actual physical relationships), and improve the precisions and accuracies of stellar masses. Several targets support Raghavan's Ph.D. thesis, which is a comprehensive survey aimed at determining the multiplicity fraction among solar-type stars.

Tomographic separation of composite spectra. The components of Plaskett's Star

NASA Technical Reports Server (NTRS)

Bagnuolo, William G., Jr.; Gies, Douglas R.; Wiggs, Michael S.

1991-01-01

The UV photospheric lines of Plaskett's Star (HD 47129), a 14.4 day period, double lined O-type spectroscopic binary were analyzed. Archival data from IUE (17 spectra well distributed in orbital phase) were analyzed with several techniques. A cross correlation analysis, which showed that the secondary produces significant lines in the UV, indicates that the mass ratio is q = 1.18 + or - 0.12 (secondary slightly more massive). A tomography algorithm was used to produce the separate spectra of the two stars in six spectral regions. The interpolated spectral classifications of the primary and secondary, 07.3 I and 06.2 I, respectively, were estimated through a comparison of UV line ratios with those in spectral standard stars. The intensity ratio of the stars in the UV is 0.53 + or - 0.05 (primary brighter). The secondary lines appear rotationally broadened, and the projected rotational velocity V sin i for this star is estimated to be 310 + or - 20 km/s. The possible evolutionary history of this system is discussed through a comparison of the positions of the components and evolutionary tracks in the H-R diagram.

HAT-TR-318-007: A Double-lined M Dwarf Binary with Total Secondary Eclipses Discovered by HATNet and Observed by K2

NASA Astrophysics Data System (ADS)

Hartman, J. D.; Quinn, S. N.; Bakos, G. Á.; Torres, G.; Kovács, G.; Latham, D. W.; Noyes, R. W.; Shporer, A.; Fulton, B. J.; Esquerdo, G. A.; Everett, M. E.; Penev, K.; Bhatti, W.; Csubry, Z.

2018-03-01

We report the discovery by the HATNet survey of HAT-TR-318-007, a P=3.34395390+/- 0.00000020 day period detached double-lined M dwarf binary with total secondary eclipses. We combine radial velocity (RV) measurements from TRES/FLWO 1.5 m and time-series photometry from HATNet, FLWO 1.2 m, BOS 0.8 m, and NASA K2 Campaign 5, to determine the masses and radii of the component stars: MA=0.448+/-0.011 M⊙N, MB=0.2721-0.0042+0.0041 M⊙N, RA=0.4548-0.0036+0.0035 R⊙N, and RB=0.2913-0.0024+0.0023 R⊙N. We obtained a FIRE/Magellan near-infrared spectrum of the primary star during a total secondary eclipse, and we use this to obtain disentangled spectra of both components. We determine spectral types of STA=M 3.71+/- 0.69 and STB=M 5.01+/- 0.73 and effective temperatures of Teff, A= 3190+/-110 K and Teff, B=3100+/- 110 K for the primary and secondary star, respectively. We also measure a metallicity of [Fe/H] = +0.298+/- 0.080 for the system. We find that the system has a small, but significant, nonzero eccentricity of 0.0136+/- 0.0026. The K2 light curve shows a coherent variation at a period of 3.41315-0.00032+0.00030 days, which is slightly longer than the orbital period, and which we demonstrate comes from the primary star. We interpret this as the rotation period of the primary. We perform a quantitative comparison between the Dartmouth stellar evolution models and the seven systems, including HAT-TR-318-007, that contain M dwarfs with 0.2 M⊙N< M< 0.5 M⊙N, have metallicity measurements, and have masses and radii determined to better than 5% precision. Discrepancies between the predicted and observed masses and radii are found for three of the systems.

Simulations of inspiraling and merging double neutron stars using the Spectral Einstein Code

NASA Astrophysics Data System (ADS)

Haas, Roland; Ott, Christian D.; Szilagyi, Bela; Kaplan, Jeffrey D.; Lippuner, Jonas; Scheel, Mark A.; Barkett, Kevin; Muhlberger, Curran D.; Dietrich, Tim; Duez, Matthew D.; Foucart, Francois; Pfeiffer, Harald P.; Kidder, Lawrence E.; Teukolsky, Saul A.

2016-06-01

We present results on the inspiral, merger, and postmerger evolution of a neutron star-neutron star (NSNS) system. Our results are obtained using the hybrid pseudospectral-finite volume Spectral Einstein Code (SpEC). To test our numerical methods, we evolve an equal-mass system for ≈22 orbits before merger. This waveform is the longest waveform obtained from fully general-relativistic simulations for NSNSs to date. Such long (and accurate) numerical waveforms are required to further improve semianalytical models used in gravitational wave data analysis, for example, the effective one body models. We discuss in detail the improvements to SpEC's ability to simulate NSNS mergers, in particular mesh refined grids to better resolve the merger and postmerger phases. We provide a set of consistency checks and compare our results to NSNS merger simulations with the independent bam code. We find agreement between them, which increases confidence in results obtained with either code. This work paves the way for future studies using long waveforms and more complex microphysical descriptions of neutron star matter in SpEC.

Compact Objects In Binary Systems: Formation and Evolution of X-ray Binaries and Tides in Double White Dwarfs

NASA Astrophysics Data System (ADS)

Valsecchi, Francesca

Binary star systems hosting black holes, neutron stars, and white dwarfs are unique laboratories for investigating both extreme physical conditions, and stellar and binary evolution. Black holes and neutron stars are observed in X-ray binaries, where mass accretion from a stellar companion renders them X-ray bright. Although instruments like Chandra have revolutionized the field of X-ray binaries, our theoretical understanding of their origin and formation lags behind. Progress can be made by unravelling the evolutionary history of observed systems. As part of my thesis work, I have developed an analysis method that uses detailed stellar models and all the observational constraints of a system to reconstruct its evolutionary path. This analysis models the orbital evolution from compact-object formation to the present time, the binary orbital dynamics due to explosive mass loss and a possible kick at core collapse, and the evolution from the progenitor's Zero Age Main Sequence to compact-object formation. This method led to a theoretical model for M33 X-7, one of the most massive X-ray binaries known and originally marked as an evolutionary challenge. Compact objects are also expected gravitational wave (GW) sources. In particular, double white dwarfs are both guaranteed GW sources and observed electromagnetically. Although known systems show evidence of tidal deformation and a successful GW astronomy requires realistic models of the sources, detached double white dwarfs are generally approximated to point masses. For the first time, I used realistic models to study tidally-driven periastron precession in eccentric binaries. I demonstrated that its imprint on the GW signal yields constrains on the components' masses and that the source would be misclassified if tides are neglected. Beyond this adiabatic precession, tidal dissipation creates a sink of orbital angular momentum. Its efficiency is strongest when tides are dynamic and excite the components' free oscillation modes. Accounting for this effect will determine whether our interpretation of current and future observations will constrain the sources' true physical properties. To investigate dynamic tides I have developed CAFein, a novel code that calculates forced non-adiabatic stellar oscillations using a highly stable and efficient numerical method.

Spectroscopic Binary Star Studies with the Palomar Testbed Interferometer II

NASA Astrophysics Data System (ADS)

Boden, A. F.; Lane, B. F.; Creech-Eakman, M.; Queloz, D.; PTI Collaboration

1999-12-01

The Palomar Testbed Interferometer (PTI) is a long-baseline near-infrared interferometer located at Palomar Observatory. Following our previous work on resolving spectroscopic binary stars with the Palomar Testbed Interferometer (PTI), we will present a number of new visual and physical orbit determinations derived from integrated reductions of PTI visibility and archival radial velocity data. The six systems for which we will present new orbit models are: 12 Boo (HD 123999), 75 Cnc (HD 78418), 47 And (HD 8374), HD 205539, BY Draconis (HDE 234677), and 3 Boo (HD 120064). Most of these systems are double-lined binary systems (SB2), and integrated astrometric/radial velocity orbit modeling provides precise fundamental parameters (mass, luminosity) and system distance determinations comparable with Hipparcos precisions. The work described in this paper was performed under contract with the National Aeronautics and Space Administration.

A FEROS Survey of Hot Subdwarf Stars

NASA Astrophysics Data System (ADS)

Vennes, Stéphane; Németh, Péter; Kawka, Adela

2018-02-01

We have completed a survey of twenty-two ultraviolet-selected hot subdwarfs using the Fiber-fed Extended Range Optical Spectrograph (FEROS) and the 2.2-m telescope at La Silla. The sample includes apparently single objects as well as hot subdwarfs paired with a bright, unresolved companion. The sample was extracted from our GALEX catalogue of hot subdwarf stars. We identified three new short-period systems (P = 3.5 hours to 5 days) and determined the orbital parameters of a long-period (P = 62d.66) sdO plus G III system. This particular system should evolve into a close double degenerate system following a second common envelope phase.We also conducted a chemical abundance study of the subdwarfs: Some objects show nitrogen and argon abundance excess with respect to oxygen. We present key results of this programme.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Yun; Kouwenhoven, M. B. N.; Stamatellos, D.

The origin of very low-mass hydrogen-burning stars, brown dwarfs (BDs), and planetary-mass objects (PMOs) at the low-mass end of the initial mass function is not yet fully understood. Gravitational fragmentation of circumstellar disks provides a possible mechanism for the formation of such low-mass objects. The kinematic and binary properties of very low-mass objects formed through disk fragmentation at early times (<10 Myr) were discussed in our previous paper. In this paper we extend the analysis by following the long-term evolution of disk-fragmented systems up to an age of 10 Gyr, covering the ages of the stellar and substellar populations inmore » the Galactic field. We find that the systems continue to decay, although the rates at which companions escape or collide with each other are substantially lower than during the first 10 Myr, and that dynamical evolution is limited beyond 1 Gyr. By t = 10 Gyr, about one third of the host stars are single, and more than half have only one companion left. Most of the other systems have two companions left that orbit their host star in widely separated orbits. A small fraction of companions have formed binaries that orbit the host star in a hierarchical triple configuration. The majority of such double-companion systems have internal orbits that are retrograde with respect to their orbits around their host stars. Our simulations allow a comparison between the predicted outcomes of disk fragmentation with the observed low-mass hydrogen-burning stars, BDs, and PMOs in the solar neighborhood. Imaging and radial velocity surveys for faint binary companions among nearby stars are necessary for verification or rejection of the formation mechanism proposed in this paper.« less

Planets around the evolved stars 24 Boötis and γ Libra: A 30 d-period planet and a double giant-planet system in possible 7:3 MMR

NASA Astrophysics Data System (ADS)

Takarada, Takuya; Sato, Bun'ei; Omiya, Masashi; Harakawa, Hiroki; Nagasawa, Makiko; Izumiura, Hideyuki; Kambe, Eiji; Takeda, Yoichi; Yoshida, Michitoshi; Itoh, Yoichi; Ando, Hiroyasu; Kokubo, Eiichiro; Ida, Shigeru

2018-05-01

We report the detection of planets around two evolved giant stars from radial velocity measurements at Okayama Astrophysical observatory. 24 Boo (G3 IV) has a mass of 0.99 M_{⊙}, a radius of 10.64 R_{⊙}, and a metallicity of [Fe/H] = -0.77. The star hosts one planet with a minimum mass of 0.91 MJup and an orbital period of 30.35 d. The planet has one of the shortest orbital periods among those ever found around evolved stars using radial-velocity methods. The stellar radial velocities show additional periodicity with 150 d, which can probably be attributed to stellar activity. The star is one of the lowest-metallicity stars orbited by planets currently known. γ Lib (K0 III) is also a metal-poor giant with a mass of 1.47 M_{⊙}, a radius of 11.1 R_{⊙}, and [Fe/H] = -0.30. The star hosts two planets with minimum masses of 1.02 MJup and 4.58 MJup, and periods of 415 d and 964 d, respectively. The star has the second-lowest metallicity among the giant stars hosting more than two planets. Dynamical stability analysis for the γ Lib system sets the minimum orbital inclination angle to be about 70° and suggests that the planets are in 7:3 mean-motion resonance, though the current best-fitting orbits for the radial-velocity data are not totally regular.

Variable Circumstellar Disks of “Classical” Be Stars, Part 2

NASA Astrophysics Data System (ADS)

Gerhartz, Cody; Davidson, J. W.; Bjorkman, K. S.; Wisniewski, J. P.

2014-01-01

Circumstellar disks are common among many stars, all spectral types, and at different stages of their lifetimes. Among the near-main sequence “Classical” Be stars, there is growing evidence that these disks can form, dissipate, and reform, on timescales that are differ from case to case. We present data for a subset of cases where observations have been obtained throughout the different phases of the disk cycle. Using data obtained with the SpeX instrument at the NASA IRTF, we examine the IR spectral line variability of these stars to better understand the timescales and the physical mechanisms involved. The primary focus in this study are the V/R variations that are observed in the sample. A complete run of all double-peaked velocity profiles in the sample is now complete. The second stage of our project is to examine a sample of star clusters known to contain Be stars, with the goal to develop a more statistically significant sample of variable circumstellar disk systems. With a robust multi-epoch study we can determine whether these Be stars exhibit disk-loss or disk-renewal phases. The larger sample will enable an understanding of the prevalence of these disk events.

Reaching the boundary between stellar kinematic groups and very wide binaries. III. Sixteen new stars and eight new wide systems in the β Pictoris moving group

NASA Astrophysics Data System (ADS)

Alonso-Floriano, F. J.; Caballero, J. A.; Cortés-Contreras, M.; Solano, E.; Montes, D.

2015-11-01

Aims: We look for common proper motion companions to stars of the nearby young β Pictoris moving group. Methods: First, we compiled a list of 185 β Pictoris members and candidate members from 35 representative works. Next, we used the Aladin and STILTS virtual observatory tools and the PPMXL proper motion and Washington Double Star catalogues to look for companion candidates. The resulting potential companions were subjects of a dedicated astro-photometric follow-up using public data from all-sky surveys. After discarding 67 sources by proper motion and 31 by colour-magnitude diagrams, we obtained a final list of 36 common proper motion systems. The binding energy of two of them is perhaps too small to be considered physically bound. Results: Of the 36 pairs and multiple systems, eight are new, 16 have only one stellar component previously classified as a β Pictoris member, and three have secondaries at or below the hydrogen-burning limit. Sixteen stars are reported here for the first time as moving group members. The unexpected large number of high-order multiple systems, 12 triples and two quadruples among 36 systems, may suggest a biased list of members towards close binaries or an increment of the high-order-multiple fraction for very wide systems.

Student Observation of HR 2282 (Furud)

NASA Astrophysics Data System (ADS)

Estrada, Reed; Estrada, Chris; Anker, Payton; Barrientos, Destiny; Colbert, Charlie; Dondelinger, Edward; Gillette, Lindsey; Goodrow, Jeremy; Izadi, Tara; Mayo, Colin; Milton, Jordan; Stuart, Sarah; Varela, Nick

2017-04-01

A selected team of 8th graders measured the separation and the position angle of double star HR 2282 also known as Furud. They used a 22- inch Newtonian Alt/Az telescope to determine the scale constant, separation, and the position angle. The separation angle was 169.6 arc seconds and the position angle was 339.7 degrees. The results were compared to the 1999 Washington Double Star Catalog and were found to be extremely close.

Data Mining for Double Stars in Astrometric Catalogs

DTIC Science & Technology

2006-03-22

Astron. Gesell . de Ball (1904) 76 WFD1906a........... Cape General Catalog Gill (1906) 11 WFD1906b........... Kat. der Astron. Gesell . Becker (1906... Gesell . Skinner (1908) 73 WFD1909............. Greenwich Second Nine Year Catalog Christie (1909) 127 WFD1914............. Abbadia Observatory (Algiers...TychoDouble Star reduction project (Fabricius et al. 2002) and 14 by 2MASS. Six others were confirmed with the USNO speckle camera and 26 inch (0.7 m) refractor

LOCATING THE TRAILING EDGE OF THE CIRCUMBINARY RING IN THE KH 15D SYSTEM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Capelo, Holly L.; Herbst, William; Leggett, S. K.

2012-09-20

Following two years of complete occultation of both stars in the binary T Tauri star KH 15D by its opaque circumbinary ring, KH 15D has abruptly brightened again during apastron phases, reaching I = 15 mag. Here, we show that the brightening is accompanied by a change in spectral class from K6/K7 (the spectral class of star A) to {approx}K1, and a bluing of the system in V - I by about 0.3 mag. A radial velocity measurement confirms that, at apastron, we are now seeing direct light from star B, which is more luminous and of earlier spectral classmore » than star A. Evidently, the trailing edge of the occulting screen has just become tangent to one anse of star B's projected orbit. This confirms a prediction of the precession models, supports the view that the tilted ring is self-gravitating, and ushers in a new era of the system's evolution that should be accompanied by the same kind of dramatic phenomena observed from 1995 to 2009. It also promotes KH 15D from a single-lined to a double-lined eclipsing binary, greatly enhancing its value for testing pre-main-sequence models. The results of our study strengthen the case for truncation of the outer ring at around 4 AU by a sub-stellar object such as an extremely young giant planet. The system is currently at an optimal configuration for detecting the putative planet and we urge expedient follow-up observations.« less

Formation of double neutron star systems as implied by observations

NASA Astrophysics Data System (ADS)

Beniamini, Paz; Piran, Tsvi

2016-03-01

Double Neutron Stars (DNS) have to survive two supernovae (SNe) and still remain bound. This sets strong limits on the nature of the second collapse in these systems. We consider the masses and orbital parameters of the DNS population and constrain the two distributions of mass ejection and kick velocities directly from observations with no a priori assumptions regarding evolutionary models and/or the types of the SNe involved. We show that there is strong evidence for two distinct types of SNe in these systems, where the second collapse in the majority of the observed systems involved small mass ejection (ΔM ≲ 0.5 M⊙) and a corresponding low-kick velocity (vk ≲ 30 km s-1). This formation scenario is compatible, for example, with an electron-capture SN. Only a minority of the systems have formed via the standard SN scenario involving larger mass ejection of ˜2.2 M⊙ and kick velocities of up to 400 km s-1. Due to the typically small kicks in most DNS (which are reflected by rather low proper motion), we predict that most of these systems reside close to the Galactic disc. In particular, this implies that more NS-NS mergers occur close to the Galactic plane. This may have non-trivial implications to the estimated merger rates of DNS and to the rate of LIGO/VIRGO detections.

Similarity of PSR J1906+0746 TO PSR J0737-3039: A Candidate of a New Double Pulsar System?

NASA Astrophysics Data System (ADS)

Yang, Yi-Yan; Zhang, Cheng-Min; Li, Di; Wang, De-Hua; Pan, Yuan-Yue; Lingfu, Rong-Feng; Zhou, Zhu-Wen

2017-02-01

PSR J1906+0746 is a nonrecycled strong magnetic field neutron star (NS), sharing the properties of the secondary-formed NS PSR J0737-3039B in the double pulsar system PSR J0737-3039AB. By comparing the orbital parameters of PSR J1906+0746 with those of PSR J0737-3039AB, we conclude that both systems have a similar origin and evolution history, involving an e-capture process for forming the second-born NS, like in the case of PSR J0737-3039B. We expect the companion of PSR J1906+0746 to be a long-lived recycled pulsar with radio beams that currently cannot be observed from Earth. We suggest possible ways to detect its presence. To compare PSR J1906+0746 with PSR J0737-3039, we also present the mass distribution of eight pairs of double NSs and find that in double NSs the mass of the recycled pulsar is usually larger than that of the nonrecycled one, which may be the result of accretion.

COSMIC-LAB: Double BSS sequences as signatures of the Core Collapse phenomenon in star clusters.

NASA Astrophysics Data System (ADS)

Ferraro, Francesco

2011-10-01

Globular Clusters {GCs} are old stellar systems tracing key stages of the star formation and chemical enrichment history of the early Universe and the galaxy assembly phase. As part of a project {COSMIC-LAB} aimed at using GCs as natural laboratories to study the complex interplay between dynamics and stellar evolution, here we present a proposal dealing with the role of Blue Straggler Stars {BSS}.BSS are core-hydrogen burning stars more massive than the main-sequence turnoff population. The canonical scenarios for BSS formation are either the mass transfer between binary companions, or stellar mergers induced by collisions. We have recently discovered two distinct and parallel sequences of BSS in the core of M30 {Ferraro et al. 2009, Nature 462, 1082}. We suggested that each of the two sequences is populated by BSS formed by one of the two processes, both triggered by the cluster core collapse, that, based on the observed BSS properties, must have occurred 1-2 Gyr ago. Following this scenario, we have identified a powerful "clock" to date the occurrence of this key event in the GC history.Here we propose to secure WFC3 images of 4 post-core collapse GCs, reaching S/N=200 at the BSS magnitude level, in order to determine the ubiquity of the BSS double sequence and calibrate the "dynamical clock". This requires very high spatial resolution and very high precision photometry capabilities that are unique to the HST. The modest amount of requested time will have a deep impact on the current and future generations of dynamical evolutionary models of collisional stellar systems.

Hubble Finds Supernova Companion Star after Two Decades of Searching

NASA Image and Video Library

2017-12-08

This is an artist's impression of supernova 1993J, an exploding star in the galaxy M81 whose light reached us 21 years ago. The supernova originated in a double-star system where one member was a massive star that exploded after siphoning most of its hydrogen envelope to its companion star. After two decades, astronomers have at last identified the blue helium-burning companion star, seen at the center of the expanding nebula of debris from the supernova. The Hubble Space Telescope identified the ultraviolet glow of the surviving companion embedded in the fading glow of the supernova. More info: Using NASA’s Hubble Space Telescope, astronomers have discovered a companion star to a rare type of supernova. The discovery confirms a long-held theory that the supernova, dubbed SN 1993J, occurred inside what is called a binary system, where two interacting stars caused a cosmic explosion. "This is like a crime scene, and we finally identified the robber," said Alex Filippenko, professor of astronomy at University of California (UC) at Berkeley. "The companion star stole a bunch of hydrogen before the primary star exploded." SN 1993J is an example of a Type IIb supernova, unusual stellar explosions that contains much less hydrogen than found in a typical supernova. Astronomers believe the companion star took most of the hydrogen surrounding the exploding main star and continued to burn as a super-hot helium star. “A binary system is likely required to lose the majority of the primary star’s hydrogen envelope prior to the explosion. The problem is that, to date, direct observations of the predicted binary companion star have been difficult to obtain since it is so faint relative to the supernova itself,” said lead researcher Ori Fox of UC Berkeley. Read more: 1.usa.gov/1Az5Qb9 Credit: NASA, ESA, G. Bacon (STScI) NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

The Optical Gravitational Lensing Experiment. Catalog of RRLyr Stars from the Small Magellanic Cloud

NASA Astrophysics Data System (ADS)

Soszynski, I.; Udalski, A.; Szymanski, M.; Kubiak, M.; Pietrzynski, G.; Wozniak, P.; Zebrun, K.; Szewczyk, O.; Wyrzykowski, L.

2002-12-01

We present the catalog of RRLyrae stars from 2.4 square degrees of central parts of the Small Magellanic Cloud (SMC). The photometric data were collected during four years of the OGLE-II microlensing survey. Photometry of each star was obtained using the Difference Image Analysis (DIA) method. The catalog contains 571 objects, including 458RRab, 56RRc variables, and 57 double mode RRLyr stars (RRd). Additionally we attach a list of variables with periods between 0.18-0.26 days, which are probably delta Sct stars. Period, BVI photometry, astrometry, amplitude, and parameters of the Fourier decomposition of the I-band light curve are provided for each object. We also present the Petersen diagram for double mode pulsators. We found that the SMC RRLyr stars are fairly uniformly distributed over the studied area, with no clear correlation to any location. The most preferred periods for RRab and RRc stars are 0.589 and 0.357 days, respectively. We noticed significant excess of stars with periods of about 0.29 days, which might be second-overtone RRLyr stars (RRe). The mean extinction free magnitudes derived for RRab stars are 18.97, 19.45 and 19.73 mag for the I, V and B-band, respectively. All presented data, including individual BVI observations, are available from the OGLE Internet archive.

Constraints on binary neutron star merger product from short GRB observations

NASA Astrophysics Data System (ADS)

Gao, He; Zhang, Bing; Lü, Hou-Jun

2016-02-01

Binary neutron star (NS) mergers are strong gravitational-wave (GW) sources and the leading candidates to interpret short-duration gamma-ray bursts (SGRBs). Under the assumptions that SGRBs are produced by double neutron star mergers and that the x-ray plateau followed by a steep decay as observed in SGRB x-ray light curves marks the collapse of a supramassive neutron star to a black hole (BH), we use the statistical observational properties of Swift SGRBs and the mass distribution of Galactic double neutron star systems to place constraints on the neutron star equation of state (EoS) and the properties of the post-merger product. We show that current observations already impose the following interesting constraints. (1) A neutron star EoS with a maximum mass close to a parametrization of Mmax=2.37 M⊙(1 +1.58 ×10-10P-2.84) is favored. (2) The fractions for the several outcomes of NS-NS mergers are as follows: ˜40 % prompt BHs, ˜30 % supramassive NSs that collapse to BHs in a range of delay time scales, and ˜30 % stable NSs that never collapse. (3) The initial spin of the newly born supramassive NSs should be near the breakup limit (Pi˜1 ms ), which is consistent with the merger scenario. (4) The surface magnetic field of the merger products is typically ˜1015 G . (5) The ellipticity of the supramassive NSs is ɛ ˜(0.004 -0.007 ), so that strong GW radiation is released after the merger. (6) Even though the initial spin energy of the merger product is similar, the final energy output of the merger product that goes into the electromagnetic channel varies in a wide range from several 1049 to several 1052 erg , since a good fraction of the spin energy is either released in the form of GWs or falls into the black hole as the supramassive NS collapses.

Functional Dependence for Calculation of Additional Real-Power Losses in a Double-Wound Supply Transformer Caused by Unbalanced Active Inductive Load in a Star Connection with an Insulated Neutral

ERIC Educational Resources Information Center

Kostinskiy, Sergey S.; Troitskiy, Anatoly I.

2016-01-01

This article deals with the problem of calculating the additional real-power losses in double-wound supply transformers with voltage class 6 (10)/0,4 kV, caused by unbalanced active inductive load connected in a star connection with an insulated neutral. When solving the problem, authors used the theory of electric circuits, method of balanced…

Comparison Study II: Double Star Measurements Made Using an Equatorial Mounted Refractor and an Alt-Az Mounted Reflector

NASA Astrophysics Data System (ADS)

Frey, Thomas G.; Coombs, Lee C.

2012-07-01

Eight double stars with separations between 13 and 48 arc seconds were studied. Their separations and position angles were measured using an equatorial mounted refractor and and alt-az mounted reflector. A 2x Barlow lens was used along with a Celestron Micro Guide eyepiece to magnify the separation. Comparison of the possible effect of magnitude difference on the separation and position angle measurements was investigated.

THE VERY EARLY LIGHT CURVE OF SN 2015F IN NGC 2442: A POSSIBLE DETECTION OF SHOCK-HEATED COOLING EMISSION AND CONSTRAINTS ON SN Ia PROGENITOR SYSTEM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Im, Myungshin; Choi, Changsu; Kim, Jae-Woo

2015-11-15

The main progenitor candidates of Type Ia supernovae (SNe Ia) are white dwarfs in binary systems where the companion star is another white dwarf (double degenerate (DD) system) or a less-evolved, non-degenerate star with R{sub *} ≳ 0.1 R{sub ⊙} (single degenerate system). However, no direct observational evidence exists to tell us which progenitor system is more common. Recent studies suggest that the light curve of a supernova shortly after its explosion can be used to set a limit on the progenitor size, R{sub *}. Here, we report high-cadence monitoring observations of SN 2015F, a normal SN Ia in themore » galaxy NGC 2442, starting about 84 days before the first light time. Using our daily cadence data, we capture the emergence of the radioactively powered light curve; more importantly, with >97.4% confidence, we detect possible dim precursor emission that appears roughly 1.5 days before the rise of the radioactively powered emission. The signal is consistent with theoretical expectations for a progenitor system involving a companion star with R{sub *} ≃ 0.1–1 R{sub ⊙} or a prompt explosion of a DD system, but is inconsistent with the typically invoked size of a white dwarf progenitor of R{sub *} ∼ 0.01 R{sub ⊙}. Upper limits on the precursor emission also constrain the progenitor size to be R{sub *} ≲ 0.1 R{sub ⊙} with a companion star size of R{sub *} ≲ 1.0 R{sub ⊙}, excluding a very large companion star in the progenitor system. Additionally, we find that the distance to SN 2015F is 23.9 ± 0.4 Mpc.« less

The 25 parsec local white dwarf population

NASA Astrophysics Data System (ADS)

Holberg, J. B.; Oswalt, T. D.; Sion, E. M.; McCook, G. P.

2016-11-01

We have extended our detailed survey of the local white dwarf population from 20 to 25 pc, effectively doubling the sample volume, which now includes 232 stars. In the process, new stars within 20 pc have been added, a more uniform set of distance estimates as well as improved spectral and binary classifications are available. The present 25 pc sample is estimated to be about 68 per cent complete (the corresponding 20 pc sample is now 86 per cent complete). The space density of white dwarfs is unchanged at 4.8 ± 0.5 × 10-3 pc-3. This new study includes a white dwarf mass distribution and luminosity function based on the 232 stars in the 25 pc sample. We find a significant excess of single stars over systems containing one or more companions (74 per cent versus 26 per cent). This suggests mechanisms that result in the loss of companions during binary system evolution. In addition, this updated sample exhibits a pronounced deficiency of nearby `Sirius-like' systems. 11 such systems were found within the 20 pc volume versus only one additional system found in the volume between 20 and 25 pc. An estimate of white dwarf birth rates during the last ˜8 Gyr is derived from individual remnant cooling ages. A discussion of likely ways new members of the local sample may be found is provided.

VizieR Online Data Catalog: Double stars with wide separations in the AGK3 (Halbwachs+, 2016)

NASA Astrophysics Data System (ADS)

Halbwachs, J. L.; Mayor, M.; Udry, S.

2016-10-01

A large list of common proper motion stars selected from the third Astronomischen Gesellschaft Katalog (AGK3) was monitored with the CORAVEL (for COrrelation RAdial VELocities) spectrovelocimeter, in order to prepare a sample of physical binaries with very wide separations. In paper I,66 stars received special attention, since their radial velocities (RV) seemed to be variable. These stars were monitored over several years in order to derive the elements of their spectroscopic orbits. In addition, 10 of them received accurate RV measurements from the SOPHIE spectrograph of the T193 telescope at the Observatory of Haute-Provence. For deriving the orbital elements of double-lined spectroscopic binaries (SB2s), a new method was applied, which assumed that the RV of blended measurements are linear combinations of the RV of the components. 13 SB2 orbits were thus calculated. The orbital elements were eventually obtained for 52 spectroscopic binaries (SBs), two of them making a triple system. 40 SBs received their first orbit and the orbital elements were improved for 10 others. In addition, 11 SBs were discovered with very long periods for which the orbital parameters were not found. It appeared that HD 153252 has a close companion, which is a candidate brown dwarf with a minimum mass of 50 Jupiter masses. In paper II, 80 wide binaries (WBs) were detected, and 39 optical pairs were identified. Adding CPM stars with separations close enough to be almost certain they are physical, a "bias-controlled" sample of 116 wide binaries was obtained, and used to derive the distribution of separations from 100 to 30,000 au. The distribution obtained doesn't match the log-constant distribution, but is in agreement with the log-normal distribution. The spectroscopic binaries detected among the WB components were used to derive statistical informations about the multiple systems. The close binaries in WBs seem to be similar to those detected in other field stars. As for the WBs, they seem to obey the log-normal distribution of periods. The number of quadruple systems is in agreement with the "no correlation" hypothesis; this indicates that an environment conducive to the formation of WBs doesn't favor the formation of subsystems with periods shorter than 10 years. (9 data files).

Nonlinear convective pulsation models of type II Cepheids

NASA Astrophysics Data System (ADS)

Smolec, Radoslaw

2015-08-01

We present a grid of nonlinear convective pulsation models of type-II Cepheids: BL Her stars, W Vir stars and RV Tau stars. The models cover a wide range of masses, luminosities, effective temperatures and chemical compositions. The most interesting result is detection of deterministic chaos in the models. Different routes to chaos are detected (period doubling, intermittent route) as well as variety of phenomena intrinsic to chaotic dynamics (periodic islands within chaotic bands, crisis bifurcation, type-I and type-III intermittency). Some of the phenomena (period doubling in BL Her and in RV Tau stars, irregular pulsation of RV Tau stars) are well known in the pulsation of type-II Cepheids. Prospects of discovering the other are briefly discussed. Transition from BL Her type pulsation through W Vir type till RV Tau type is analysed. In the most luminous models a dynamical instability is detected, which indicates that pulsation driven mass loss is important process occurring in type-II Cepheids.

Chromospherically Active Stars. XXV. HD 144110=EV Draconis, a Double-lined Dwarf Binary

NASA Astrophysics Data System (ADS)

Fekel, Francis C.; Henry, Gregory W.; Lewis, Ceteka

2005-08-01

New spectroscopic and photometric observations of HD 144110 have been used to obtain an improved orbital element solution and determine some basic properties of the system. This chromospherically active, double-lined spectroscopic binary has an orbital period of 1.6714012 days and a circular orbit. We classify the components as G5 V and K0 V and suggest that they are slightly metal-rich. The photometric observations indicate that the rotation of HD 144110 is synchronous with the orbital period. Despite the short orbital period, no evidence of eclipses is seen in our photometry.

Measurements of 427 Double Stars With Speckle Interferometry: The Winter/Spring 2017 Observing Program at Brilliant Sky Observatory, Part 1

NASA Astrophysics Data System (ADS)

Harshaw, Richard

2018-04-01

In the winter and spring of 2017, an aggressive observing program of measuring close double stars with speckle interferometry and CCD imaging was undertaken at Brilliant Sky Observatory, my observing site in Cave Creek, Arizona. A total of 596 stars were observed, 8 of which were rejected for various reasons, leaving 588 pairs. Of these, 427 were observed and measured with speckle interferometry, while the remaining 161 were measured with a CCD. This paper reports the results of the observations of the 427 speckle cases. A separate paper in this issue will report the CCD measurements of the 161 other pairs.

Measurements of 161 Double Stars With a High-Speed CCD: The Winter/Spring 2017 Observing Program at Brilliant Sky Observatory, Part 2

NASA Astrophysics Data System (ADS)

Harshaw, Richard

2018-04-01

In the winter and spring of 2017, an aggressive observing program of measuring close double stars with speckle interferometry and CCD imaging was undertaken at Brilliant Sky Observatory, my observing site in Cave Creek, Arizona. A total of 596 stars were observed, 8 of which were rejected for various reasons, leaving 588 pairs. Of these, 427 were observed and measured with speckle interferometry, while the remaining 161 were measured with a CCD. This paper reports the results of the observations of the 161 CCD cases. A separate paper in this issue will report the speckle measurements of the 427 other pairs.

Peculiar double-periodic pulsation in RR Lyrae stars of the OGLE collection - II. Short-period stars with a dominant radial fundamental mode

NASA Astrophysics Data System (ADS)

Prudil, Z.; Smolec, R.; Skarka, M.; Netzel, H.

2017-03-01

We report the discovery of a new group of double-periodic stars in the OGLE Galactic bulge photometry. In 38 stars identified as fundamental-mode RR Lyrae and four classified as first-overtone RR Lyrae, we detected an additional shorter periodicity. The periods of the dominant variability in the newly discovered group are 0.28 < PD < 0.41 d. Period ratios (0.68-0.72) are smaller than the period ratios of the Galactic bulge RRd stars. The typical amplitude ratio (of the additional to the dominant periodicity) is 20 per cent for the stars identified as fundamental-mode RR Lyrae and 50 per cent for stars classified as first-overtone RR Lyrae. 10 stars from our sample exhibit equidistant peaks in the frequency spectrum, which suggests the Blazhko-type modulation of the main pulsation frequency and/or additional periodicity. The Fourier coefficients R21 and R31 are some of the lowest among fundamental-mode RR Lyrae stars, but among the highest for the first-overtone pulsators. For the phase Fourier coefficients φ21 and φ31, our stars lie between RRab and RRc stars. The stars discussed were compared with radial linear pulsation models. Their position in the Petersen diagram cannot be reproduced by assuming that two radial modes are excited and their physical parameters are like those characteristic of RR Lyrae stars. The non-radial-mode scenario also faces difficulties. We conclude that the dominant variability is most likely due to pulsation in the radial fundamental mode, which applies to stars classified as first-overtone mode pulsators. At this point, we cannot explain the nature of the additional periodicity. Even more, the classification of the stars as RR Lyrae should be treated as tentative.

Massive eclipsing binary candidates

NASA Technical Reports Server (NTRS)

Garrison, R. F.; Schild, R. E.; Hiltner, W. A.

1983-01-01

New UBV data are provided for 63 southern OB stars which are either identified in the survey by Garrison, Hiltner, and Schild as having double lines or are known from Wood et al. to be eclipsing binaries. Twenty of the stars are known eclipsing variables. Four stars, not previously known as eclipsing, have both spectroscopic evidence of duplicity and significant photometric variations. Several additional stars have a marginally significant spread in V magnitude.

StarPals International Young Astronomers' Network Collaborative Projects for IYA

NASA Astrophysics Data System (ADS)

Kingan, Jessi

2008-09-01

StarPals is a nascent non-profit organization with the goal of providing opportunities for international collaboration between students of all ages within space science research. We believe that by encouraging an interest in the cosmos, the one thing that is truly Universal, from a young age, students will not only further their knowledge of and interest in science but will learn valuable teamwork and life skills. The goal is to foster respect, understanding and appreciation of cultural diversity among all StarPals participants, whether students, teachers, or mentors. StarPals aims to inspire students by providing opportunities in which, more than simply visualizing themselves as research scientists, they can actually become one. The technologies of robotic telescopes, videoconferencing, and online classrooms are expanding the possibilities like never before. In honor of IYA2009, StarPals would like to encourage 400 schools to participate on a global scale in astronomy/cosmology research on various concurrent projects. We will offer in-person or online workshops and training sessions to teach the teachers. We will be seeking publication in scientific journals for some student research. For our current project, the Double Stars Challenge, students use the robotic telescopes to take a series of four images of one of 30 double stars from a list furnished by the US Naval Observatory and then use MPO Canopus software to take distance and position angle measurements. StarPals provides students with hands-on training, telescope time, and software to complete the imaging and measuring. A paper will be drafted from our research data and submitted to the Journal of Double Star Observations. The kids who participate in this project may potentially be the youngest contributors to an article in a vetted scientific journal. Kids rapidly adapt and improve their computer skills operating these telescopes and discover for themselves that science is COOL!

On the Lack of Circumbinary Planets Orbiting Isolated Binary Stars

NASA Astrophysics Data System (ADS)

Fleming, David; Barnes, Rory; Graham, David E.; Luger, Rodrigo; Quinn, Thomas R.

2018-04-01

To date, no binary star system with an orbital period less than 7.5 days has been observed to host a circumbinary planet (CBP), a puzzling observation given the thousands of binary stars with orbital periods < 10 days discovered by the Kepler mission (Kirk et al., 2016) and the observational biases that favor their detection (Munoz & Lai, 2015). We outline a mechanism that explains the observed lack of CBPs via coupled stellar-tidal evolution of isolated binary stars. Tidal forces between low-mass, short-period binary stars on the pre-main sequence slow the stellar rotations, transferring rotational angular momentum to the orbit as the stars approach the tidally locked state. This transfer increases the binary orbital period, expanding the region of dynamical instability around the binary, and destabilizing CBPs that tend to preferentially orbit just beyond the initial dynamical stability limit. After the stars tidally lock, we find that angular momentum loss due to magnetic braking can significantly shrink the binary orbit, and hence the region of dynamical stability, over time impacting where surviving CBPs are observed relative to the boundary. We perform simulations over a wide range of parameter space and find that the expansion of the instability region occurs for most plausible initial conditions and that in some cases, the stability semi-major axis doubles from its initial value. We examine the dynamical and observable consequences of a CBP falling within the dynamical instability limit by running N-body simulations of circumbinary planetary systems and find that typically, at least one planet is ejected from the system. We apply our theory to the shortest period Kepler binary that possesses a CBP, Kepler-47, and find that its existence is consistent with our model. Under conservative assumptions, we find that coupled stellar-tidal evolution of pre-main sequence binary stars removes at least one close-in CBP in 87% of multi-planet circumbinary systems.

BLUE STRAGGLERS IN GLOBULAR CLUSTER 47 TUCANAE

NASA Technical Reports Server (NTRS)

2002-01-01

The core of globular cluster 47 Tucanae is home to many blue stragglers, rejuvenated stars that glow with the blue light of young stars. A ground-based telescope image (on the left) shows the entire crowded core of 47 Tucanae, located 15,000 light-years away in the constellation Tucana. Peering into the heart of the globular cluster's bright core, the Hubble Space Telescope's Wide Field and Planetary Camera 2 separated the dense clump of stars into many individual stars (image on right). Some of these stars shine with the light of old stars; others with the blue light of blue stragglers. The yellow circles in the Hubble telescope image highlight several of the cluster's blue stragglers. Analysis for this observation centered on one massive blue straggler. Astronomers theorize that blue stragglers are formed either by the slow merger of stars in a double-star system or by the collision of two unrelated stars. For the blue straggler in 47 Tucanae, astronomers favor the slow merger scenario. This image is a 3-color composite of archival Hubble Wide Field and Planetary Camera 2 images in the ultraviolet (blue), blue (green), and violet (red) filters. Color tables were assigned and scaled so that the red giant stars appear orange, main-sequence stars are white/green, and blue stragglers are appropriately blue. The ultraviolet images were taken on Oct. 25, 1995, and the blue and violet images were taken on Sept. 1, 1995. Credit: Rex Saffer (Villanova University) and Dave Zurek (STScI), and NASA

Albireo: 260 Years of Astrometric Observations

NASA Astrophysics Data System (ADS)

Hass, Jacob; Phung, Kevin; Carro, Joseph; Hock, Emily; Loveland, Donald; Nibbe, Tristan; Sharp, Zoe; Smit, Jenny; Genet, Russell

2016-03-01

The historical record of Albireo's observations reflects the progress of double star research. Some 294 astrometric observations have been published starting with Bradley's 1755 observation and ending with our 2015 observation. Several observation techniques were used over this 260 year span. Noteworthy are the historic contributions of astronomers such as James Bradley, Christian Mayer, William Herschel, Giuseppe Piazzi, Friedrich Georg Wilhelm von Struve, Sir John Herschel, Sir James South, Edward Skinner King, and Andrei Tokovinin. Overall trend lines of the past observations of Albireo are compared to our current observation, and are generally concurrent. Dividing Albireo's past observations of separation into time segments shows evidence of a known third star in Albireo's system.

Lick Observatory Optical SETI: targeted search and new directions.

PubMed

Stone, R P S; Wright, S A; Drake, F; Muñoz, M; Treffers, R; Werthimer, D

2005-10-01

Lick Observatory's Optical SETI (search for extraterrestrial intelligence) program has been in regular operation for 4.5 years. We have observed 4,605 stars of spectral types F-M within 200 light-years of Earth. Occasionally, we have appended objects of special interest, such as stars with known planetary systems. We have observed 14 candidate signals ("triple coincidences"), all but one of which are explained by transient local difficulties. Additional observations of the remaining candidate have failed to confirm arriving pulse events. We now plan to proceed in a more economical manner by operating in an unattended drift scan mode. Between operational and equipment modifications, efficiency will more than double.

ALMA detection of the rotating molecular disk wind from the young star HD 163296

NASA Astrophysics Data System (ADS)

Klaassen, P. D.; Juhasz, A.; Mathews, G. S.; Mottram, J. C.; De Gregorio-Monsalvo, I.; van Dishoeck, E. F.; Takahashi, S.; Akiyama, E.; Chapillon, E.; Espada, D.; Hales, A.; Hogerheijde, M. R.; Rawlings, M.; Schmalzl, M.; Testi, L.

2013-07-01

Disk winds have been postulated as a mechanism for angular momentum release in protostellar systems for decades. HD 163296 is a Herbig Ae star surrounded by a disk and has been shown to host a series of HH knots (HH 409) with bow shocks associated with the farthest knots. Here we present ALMA science verification data of CO J = 2-1 and J = 3-2 emission, which are spatially coincident with the blue shifted jet of HH knots, and offset from the disk by -18.6 km s-1. The emission has a double corkscrew morphology and extends more than 10'' from the disk with embedded emission clumps coincident with jet knots. We interpret this double corkscrew as emission from material in a molecular disk wind, and that the compact emission near the jet knots is being heated by the jet that is moving at much higher velocities. We show that the J = 3-2 emission is likely heavily filtered by the interferometer, but the J = 2-1 emission suffers less due to the larger beam and sensitivity to larger scale structures. Excitation analysis suggests temperatures exceeding 900 K in these compact features, with the wind mass, momentum and energy being of order 10-5 M⊙, 10-4 M⊙ km s-1 and 1040 erg, respectively. The high mass loss rate suggests that this star is dispersing the disk faster than it is funneling mass onto the star.

Hot Subluminous Stars

NASA Astrophysics Data System (ADS)

Heber, U.

2016-08-01

Hot subluminous stars of spectral type B and O are core helium-burning stars at the blue end of the horizontal branch or have evolved even beyond that stage. Most hot subdwarf stars are chemically highly peculiar and provide a laboratory to study diffusion processes that cause these anomalies. The most obvious anomaly lies with helium, which may be a trace element in the atmosphere of some stars (sdB, sdO) while it may be the dominant species in others (He-sdB, He-sdO). Strikingly, the distribution in the Hertzsprung-Russell diagram of He-rich versus He-poor hot subdwarf stars of the globular clusters ω Cen and NGC 2808 differ from that of their field counterparts. The metal-abundance patterns of hot subdwarfs are typically characterized by strong deficiencies of some lighter elements as well as large enrichments of heavy elements. A large fraction of sdB stars are found in close binaries with white dwarf or very low-mass main sequence companions, which must have gone through a common-envelope (CE) phase of evolution. Because the binaries are detached they provide a clean-cut laboratory to study this important but yet poorly understood phase of stellar evolution. Hot subdwarf binaries with sufficiently massive white dwarf companions are viable candidate progenitors of type Ia supernovae both in the double degenerate as well as in the single degenerate scenario as helium donors for double detonation supernovae. The hyper-velocity He-sdO star US 708 may be the surviving donor of such a double detonation supernova. Substellar companions to sdB stars have also been found. For HW Vir systems the companion mass distribution extends from the stellar into the brown dwarf regime. A giant planet to the acoustic-mode pulsator V391 Peg was the first discovery of a planet that survived the red giant evolution of its host star. Evidence for Earth-size planets to two pulsating sdB stars have been reported and circumbinary giant planets or brown dwarfs have been found around HW Vir systems from eclipse timings. The high incidence of circumbinary substellar objects suggests that most of the planets are formed from the remaining CE material (second generation planets). Several types of pulsating star have been discovered among hot subdwarf stars, the most common are the gravity-mode sdB pulsators (V1093 Her) and their hotter siblings, the p-mode pulsating V361 Hya stars. Another class of multi-periodic pulsating hot subdwarfs has been found in the globular cluster ω Cen that is unmatched by any field star. Asteroseismology has advanced enormously thanks to the high-precision Kepler photometry and allowed stellar rotation rates to be determined, the interior structure of gravity-mode pulsators to be probed and stellar ages to be estimated. Rotation rates turned out to be unexpectedly slow calling for very efficient angular momentum loss on the red giant branch or during the helium core flash. The convective cores were found to be larger than predicted by standard stellar evolution models requiring very efficient angular momentum transport on the red giant branch. The masses of hot subdwarf stars, both single or in binaries, are the key to understand the stars’ evolution. A few pulsating sdB stars in eclipsing binaries have been found that allow both techniques to be applied for mass determination. The results, though few, are in good agreement with predictions from binary population synthesis calculations. New classes of binaries, hosting so-called extremely low mass (ELM) white dwarfs (M < 0.3 M ⊙), have recently been discovered, filling a gap in the mosaic of binary stellar evolution. Like most sdB stars the ELM white dwarfs are the stripped cores of red giants, the known companions are either white dwarfs, neutron stars (pulsars) or F- or A-type main sequence stars (“EL CVn” stars). In the near future, the Gaia mission will provide high-precision astrometry for a large sample of subdwarf stars to disentangle the different stellar populations in the field and to compare the field subdwarf population with the globular clusters’ hot subdwarfs. New fast-moving subdwarfs will allow the mass of the Galactic dark matter halo to be constrained and additional unbound hyper-velocity stars may be discovered. Subdwarf O/B stars and extremely low mass white dwarfs: atmospheric parameters and abundances, formation and evolution, binaries, planetary companions, pulsation, and kinematics.

The MACHO Project Sample of Galactic Bulge High-Amplitude δ Scuti Stars: Pulsation Behavior and Stellar Properties

NASA Astrophysics Data System (ADS)

Alcock, C.; Allsman, R. A.; Alves, D. R.; Axelrod, T. S.; Becker, A. C.; Bennett, D. P.; Cook, K. H.; Freeman, K. C.; Geha, M.; Griest, K.; Lehner, M. J.; Marshall, S. L.; McNamara, B. J.; Minniti, D.; Nelson, C.; Peterson, B. A.; Popowski, P.; Pratt, M. R.; Quinn, P. J.; Rodgers, A. W.; Sutherland, W.; Templeton, M. R.; Vandehei, T.; Welch, D. L.

2000-06-01

We have detected 90 objects with periods and light-curve structures similar to those of field δ Scuti stars using the Massive Compact Halo Object (MACHO) Project database of Galactic bulge photometry. If we assume similar extinction values for all candidates and absolute magnitudes similar to those of other field high-amplitude δ Scuti stars (HADS), the majority of these objects lie in or near the Galactic bulge. At least two of these objects are likely foreground δ Scuti stars, one of which may be an evolved nonradial pulsator, similar to other evolved, disk-population δ Scuti stars. We have analyzed the light curves of these objects and find that they are similar to the light curves of field δ Scuti stars and the δ Scuti stars found by the Optical Gravitational Lens Experiment (OGLE). However, the amplitude distribution of these sources lies between those of low- and high-amplitude δ Scuti stars, which suggests that they may be an intermediate population. We have found nine double-mode HADS with frequency ratios ranging from 0.75 to 0.79, four probable double- and multiple-mode objects, and another four objects with marginal detections of secondary modes. The low frequencies (5-14 cycles day-1) and the observed period ratios of ~0.77 suggest that the majority of these objects are evolved stars pulsating in fundamental or first overtone radial modes.

THE RADIAL VELOCITY TATOOINE SEARCH FOR CIRCUMBINARY PLANETS: PLANET DETECTION LIMITS FOR A SAMPLE OF DOUBLE-LINED BINARY STARS-INITIAL RESULTS FROM KECK I/HIRES, SHANE/CAT/HAMSPEC, AND TNG/SARG OBSERVATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Konacki, Maciej; Helminiak, Krzysztof G.; Muterspaugh, Matthew W.

2009-10-10

We present preliminary results of the first and on-going radial velocity survey for circumbinary planets. With a novel radial velocity technique employing an iodine absorption cell, we achieve an unprecedented radial velocity (RV) precision of up to 2 m s{sup -1} for double-lined binary stars. The high-resolution spectra collected with the Keck I/Hires, TNG/Sarg, and Shane/CAT/Hamspec telescopes/spectrographs over the years 2003-2008 allow us to derive RVs and compute planet detection limits for 10 double-lined binary stars. For this initial sample of targets, we can rule out planets on dynamically stable orbits with masses as small as approx0.3 to 3 Mmore » {sub Jup} for the orbital periods of up to approx5.3 years. Even though the presented sample of stars is too small to make any strong conclusions, it is clear that the search for circumbinary planets is now technique-wise possible and eventually will provide new constraints for the planet formation theories.« less

Engaging Teenagers in Astronomy Using the Lens of Next Generation Science Standards and Common Core State Standards (Abstract)

NASA Astrophysics Data System (ADS)

Gillette, S.; Wolf, D.; Harrison, J.

2017-12-01

(Abstract only) The Vanguard Double Star Workshop has been developed to teach eighth graders the technique of measuring position angle and separation of double stars. Through this program, the students follow in the footsteps of a professional scientist by researching the topic, performing the experiment, writing a scientific article, publishing a scientific article, and finally presenting the material to peers. An examination of current educational standards grounds this program in educational practice and philosophy.

Engaging Teenagers in Astronomy Using the Lens of Next Generation Science Standards and Common Core State Standards

NASA Astrophysics Data System (ADS)

Gillette, Sean; Wolf, Debbie; Harrison, Jeremiah

2017-06-01

The Vanguard Double Star Workshop has been developed to teach eighth graders the technique of measuring position angle and separation of double stars. Through this program, the students follow in the footsteps of a professional scientist by researching the topic, performing the experiment, writing a scientific article, publishing a scientific article, and finally presenting the material to peers. An examination of current educational standards grounds this program in educational practice and philosophy.

The white dwarf binary pathways survey - II. Radial velocities of 1453 FGK stars with white dwarf companions from LAMOST DR 4

NASA Astrophysics Data System (ADS)

Rebassa-Mansergas, A.; Ren, J. J.; Irawati, P.; García-Berro, E.; Parsons, S. G.; Schreiber, M. R.; Gänsicke, B. T.; Rodríguez-Gil, P.; Liu, X.; Manser, C.; Nevado, S. P.; Jiménez-Ibarra, F.; Costero, R.; Echevarría, J.; Michel, R.; Zorotovic, M.; Hollands, M.; Han, Z.; Luo, A.; Villaver, E.; Kong, X.

2017-12-01

We present the second paper of a series of publications aiming at obtaining a better understanding regarding the nature of type Ia supernovae (SN Ia) progenitors by studying a large sample of detached F, G and K main-sequence stars in close orbits with white dwarf companions (i.e. WD+FGK binaries). We employ the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) data release 4 spectroscopic data base together with Galaxy Evolution Explorer (GALEX) ultraviolet fluxes to identify 1549 WD+FGK binary candidates (1057 of which are new), thus doubling the number of known sources. We measure the radial velocities of 1453 of these binaries from the available LAMOST spectra and/or from spectra obtained by us at a wide variety of different telescopes around the globe. The analysis of the radial velocity data allows us to identify 24 systems displaying more than 3σ radial velocity variation that we classify as close binaries. We also discuss the fraction of close binaries among WD+FGK systems, which we find to be ∼10 per cent, and demonstrate that high-resolution spectroscopy is required to efficiently identify double-degenerate SN Ia progenitor candidates.

Determining the Separation and Position Angles of Orbiting Binary Stars: Comparison of Three Methods

NASA Astrophysics Data System (ADS)

Walsh, Ryan; Boule, Cory; Andrews, Katelyn; Penfield, Andrew; Ross, Ian; Lucas, Gaylon; Braught, Trisha; Harfenist, Steven; Goodale, Keith

2015-07-01

To initiate a long term binary star research program, undergraduate students compared the accuracy and ease of measuring the separations and position angles of three long period binary pairs using three different measurement techniques. It was found that digital image capture using BackyardEOS software and subsequent analysis in Adobe Photoshop was the most accurate and easiest to use of our three methods. The systems WDS J17419+7209 (STF 2241AB), WDS 19418+5032 (STFA 46AB), and WDS 16362+5255 (STF 2087AB) were found to have separations and position angles of: 30", 16°; 39.7", 133°; and 3.1", 104°, respectively. This method produced separation values within 1.3" and position angle values within 1.3° of the most recently observed values found in the Washington Double Star Catalog.

The ARGOS laser system: green light for ground layer adaptive optics at the LBT

NASA Astrophysics Data System (ADS)

Raab, Walfried; Rabien, Sebastian; Gässler, Wolfgang; Esposito, Simone; Barl, Lothar; Borelli, Jose; Daysenroth, Matthias; Gemperlein, Hans; Kulas, Martin; Ziegleder, Julian

2014-07-01

We report on the development of the laser system of ARGOS, the multiple laser guide star adaptive optics system for the Large Binocular Telescope (LBT). The system uses a total of six high powered, pulsed Nd:YAG lasers frequency-doubled to a wavelength of 532 nm to generate a set of three guide stars above each of the LBT telescopes. The position of each of the LGS constellations on sky as well as the relative position of the individual laser guide stars within this constellation is controlled by a set of steerable mirrors and a fast tip-tilt mirror within the laser system. The entire opto-mechanical system is housed in two hermetically sealed and thermally controlled enclosures on the SX and DX side of the LBT telescope. The laser beams are propagated through two refractive launch telescopes which focus the beams at an altitude of 12 km, creating a constellation of laser guide stars around a 4 arcminute diameter circle by means of Rayleigh scattering. In addition to the GLAO Rayleigh beacon system, ARGOS has also been designed for a possible future upgrade with a hybrid sodium laser - Rayleigh beacon combination, enabling diffraction limited operation. The ARGOS laser system was successfully installed at the LBT in April 2013. Extensive functional tests have been carried out and have verified the operation of the systems according to specifications. The alignment of the laser system with respect to the launch telescope was carried out during two more runs in June and October 2013, followed by the first propagation of laser light on sky in November 2013.

ALMA detection of a disk wind from HD 163296

NASA Astrophysics Data System (ADS)

Klaassen, Pamela; Juhasz, Attila; Mathews, Geoffrey; Mottram, Joseph; De Gregorio-Monsalvo, Itziar; van Dishoeck, Ewine; Takahashi, Satoko; Akiyama, Eiji; Chapillon, Edwige; Espada, Daniel; Hales, Antonio; Hogerheijde, Michiel; Rawlings, Mark; Schmalzl, Markus; Testi, Leonardo

2013-07-01

Disk winds have been postulated as a mechanism for angular momentum release in protostellar systems for decades. HD 163296 is a Herbig Ae star surrounded by a disk and has been shown to host a series of HH knots (HH 409) with bow shocks associated with the farthest knots. Here we present ALMA Science Verification data of CO J=2-1 and J=3-2 emission which are spatially coincident with the blue shifted jet of HH knots, and offset from the disk by -18.6 km/s. The emission has a double corkscrew morphology and extends more than 10'' from the disk with embedded emission clumps coincident with jet knots. We interpret this double corkscrew as emission from material in a molecular disk wind, and that the compact emission near the jet knots is being heated by the jet which is moving at much higher velocities. We show that the J=3-2 emission is likely heavily filtered by the interferometer, but the J=2-1 emission suffers less due to the larger beam and measurable angular scales. Excitation analysis suggests temperatures exceeding 900 K in these compact features. The high mass loss rate suggests that this star is dispersing the disk faster than it is funneling mass onto the star, signaling the end of the main accretion phase.

On the Lack of Circumbinary Planets Orbiting Isolated Binary Stars

NASA Astrophysics Data System (ADS)

Fleming, David P.; Barnes, Rory; Graham, David E.; Luger, Rodrigo; Quinn, Thomas R.

2018-05-01

We outline a mechanism that explains the observed lack of circumbinary planets (CBPs) via coupled stellar–tidal evolution of isolated binary stars. Tidal forces between low-mass, short-period binary stars on the pre-main sequence slow the stellar rotations transferring rotational angular momentum to the orbit as the stars approach the tidally locked state. This transfer increases the binary orbital period, expanding the region of dynamical instability around the binary, and destabilizing CBPs that tend to preferentially orbit just beyond the initial dynamical stability limit. After the stars tidally lock, we find that angular momentum loss due to magnetic braking can significantly shrink the binary orbit, and hence the region of dynamical stability, over time, impacting where surviving CBPs are observed relative to the boundary. We perform simulations over a wide range of parameter space and find that the expansion of the instability region occurs for most plausible initial conditions and that, in some cases, the stability semimajor axis doubles from its initial value. We examine the dynamical and observable consequences of a CBP falling within the dynamical instability limit by running N-body simulations of circumbinary planetary systems and find that, typically, at least one planet is ejected from the system. We apply our theory to the shortest-period Kepler binary that possesses a CBP, Kepler-47, and find that its existence is consistent with our model. Under conservative assumptions, we find that coupled stellar–tidal evolution of pre-main sequence binary stars removes at least one close-in CBP in 87% of multi-planet circumbinary systems.

Double neutron stars: merger rates revisited

NASA Astrophysics Data System (ADS)

Chruslinska, Martyna; Belczynski, Krzysztof; Klencki, Jakub; Benacquista, Matthew

2018-03-01

We revisit double neutron star (DNS) formation in the classical binary evolution scenario in light of the recent Laser Interferometer Gravitational-wave Observatory (LIGO)/Virgo DNS detection (GW170817). The observationally estimated Galactic DNS merger rate of R_MW = 21^{+28}_{-14} Myr-1, based on three Galactic DNS systems, fully supports our standard input physics model with RMW = 24 Myr-1. This estimate for the Galaxy translates in a non-trivial way (due to cosmological evolution of progenitor stars in chemically evolving Universe) into a local (z ≈ 0) DNS merger rate density of Rlocal = 48 Gpc-3 yr-1, which is not consistent with the current LIGO/Virgo DNS merger rate estimate (1540^{+3200}_{-1220} Gpc-3 yr-1). Within our study of the parameter space, we find solutions that allow for DNS merger rates as high as R_local ≈ 600^{+600}_{-300} Gpc-3 yr-1 which are thus consistent with the LIGO/Virgo estimate. However, our corresponding BH-BH merger rates for the models with high DNS merger rates exceed the current LIGO/Virgo estimate of local BH-BH merger rate (12-213 Gpc-3 yr-1). Apart from being particularly sensitive to the common envelope treatment, DNS merger rates are rather robust against variations of several of the key factors probed in our study (e.g. mass transfer, angular momentum loss, and natal kicks). This might suggest that either common envelope development/survival works differently for DNS (˜10-20 M⊙ stars) than for BH-BH (˜40-100 M⊙ stars) progenitors, or high black hole (BH) natal kicks are needed to meet observational constraints for both types of binaries. Our conclusion is based on a limited number of (21) evolutionary models and is valid within this particular DNS and BH-BH isolated binary formation scenario.

A Model for AR Scorpii: Emission from Relativistic Electrons Trapped by Closed Magnetic Field Lines of Magnetic White Dwarfs

NASA Astrophysics Data System (ADS)

Takata, J.; Yang, H.; Cheng, K. S.

2017-12-01

AR Scorpii is an intermediate polar binary system composed of a magnetic white dwarf (WD) and an M-type star and shows nonthermal, pulsed, and highly linearly polarized emission. The radio/optical emission modulates with the WD’s spin and shows the double-peak structure in the light curves. In this paper, we discuss a possible scenario for the radiation mechanism of AR Scorpii. The magnetic interaction on the surface of the companion star produces an outflow from the companion star, the heating of the companion star surface, and the acceleration of electrons to a relativistic energy. The accelerated electrons, whose typical Lorentz factor is ∼50–100, from the companion star move along the magnetic field lines toward the WD surface. The electrons injected with the pitch angle of \\sin {θ }p,0> 0.05 are subject to the magnetic mirror effect and are trapped in the closed magnetic field line region. We find that the emission from the first magnetic mirror points mainly contributes to the observed pulsed emission and the formation of the double-peak structure in the light curve. For the inclined rotator, the pulse peak in the calculated light curve shifts the position in the spin phase, and a Fourier analysis exhibits a beat frequency feature, which are consistent with the optical/UV observations. The pulse profile also evolves with the orbital phase owing to the effect of the viewing geometry. The model also interprets the global features of the observed spectral energy distribution in radio to X-ray energy bands. We also discuss the curvature radiation and the inverse-Compton scattering process in the outer gap accelerator of the WD in AR Scorpii and the possibility of the detection by future high-energy missions.

THE CALIFORNIA PLANET SURVEY IV: A PLANET ORBITING THE GIANT STAR HD 145934 AND UPDATES TO SEVEN SYSTEMS WITH LONG-PERIOD PLANETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Katherina Feng, Y.; Wright, Jason T.; Nelson, Benjamin

2015-02-10

We present an update to seven stars with long-period planets or planetary candidates using new and archival radial velocities from Keck-HIRES and literature velocities from other telescopes. Our updated analysis better constrains orbital parameters for these planets, four of which are known multi-planet systems. HD 24040 b and HD 183263 c are super-Jupiters with circular orbits and periods longer than 8 yr. We present a previously unseen linear trend in the residuals of HD 66428 indicative of an additional planetary companion. We confirm that GJ 849 is a multi-planet system and find a good orbital solution for the c component: it is a 1more » M {sub Jup} planet in a 15 yr orbit (the longest known for a planet orbiting an M dwarf). We update the HD 74156 double-planet system. We also announce the detection of HD 145934 b, a 2 M {sub Jup} planet in a 7.5 yr orbit around a giant star. Two of our stars, HD 187123 and HD 217107, at present host the only known examples of systems comprising a hot Jupiter and a planet with a well constrained period greater than 5 yr, and with no evidence of giant planets in between. Our enlargement and improvement of long-period planet parameters will aid future analysis of origins, diversity, and evolution of planetary systems.« less

BARIUM SURFACE ABUNDANCES OF BLUE STRAGGLERS IN THE OPEN CLUSTER NGC 6819

DOE Office of Scientific and Technical Information (OSTI.GOV)

Milliman, Katelyn E.; Mathieu, Robert D.; Schuler, Simon C., E-mail: milliman@astro.wisc.edu

2015-09-15

We present a barium surface abundance of 12 blue stragglers (BSs) and 18 main-sequence (MS) stars in the intermediate-age open cluster NGC 6819 (2.5 Gyr) based on spectra obtained from the Hydra Multi-object Spectrograph on the WIYN 3.5 m telescope. For the MS stars we find [Fe/H] = +0.05 ± 0.04 and [Ba/Fe] = −0.01 ± 0.10. The majority of the BS stars are consistent with these values. We identify five BSs with significant barium enhancement. These stars most likely formed through mass transfer from an asymptotic giant branch star that polluted the surface of the BS with the nucleosynthesismore » products generated during thermal pulsations. This conclusion aligns with the results from the substantial work done on the BSs in old open cluster NGC 188 that identifies mass transfer as the dominant mechanism for BS formation in that open cluster. However, four of the BSs with enhanced barium show no radial-velocity evidence for a companion. The one star that is in a binary is a double-lined system, meaning the companion is not a white dwarf and not the remnant of a prior AGB star. In this paper we attempt to develop a consistent scenario to explain the origin of these five BSs.« less

CCD Measurements of Double and Multiple Stars at NAO Rozhen and ASV in 2015

NASA Astrophysics Data System (ADS)

Cvetković, Z.; Pavlović, R.; Boeva, S.

2017-04-01

Results of CCD observations of 154 double or multiple stars, made with the 2 m telescope of the Bulgarian National Astronomical Observatory at Rozhen over five nights in 2015, are presented. This is the ninth series of measurements of CCD frames obtained at Rozhen. We also present results of CCD observations of 323 double or multiple stars made with the 0.6 m telescope of the Serbian Astronomical Station on the mountain of Vidojevica over 23 nights in 2015. This is the fourth series of measurements of CCD frames obtained at this station. This paper contains the results for the position angle and angular separation for 801 pairs and residuals for 127 pairs with published orbital elements or linear solutions. The angular separations are in the range from 1.″52 to 201.″56, with a median angular separation of 8.″26. We also present eight pairs that are measured for the first time and linear elements for five pairs.

Orbital Analysis of Two Triple Systems in the Open Cluster NGC 2516

NASA Astrophysics Data System (ADS)

Veramendi, M. E.; González, J. F.

2010-12-01

We report the discovery of two hierarchical triple systems in the open cluster NGC 2516. Both systems are double-lined spectroscopic binaries whose center-of-mass velocity varies in a time scale of a few years. The system BDA 19 consists of an eccentric spectroscopic binary with a period of 8.7 days and a third body orbiting with a period of about 3300 days. The close pair in the triple BDA 2 has an orbital period of 11.2 days and contains a HgMn star.

A Speckle survey of Southern Hipparcos Visual Doubles and Geneva-Copenhagen Spectroscopic Binaries

NASA Astrophysics Data System (ADS)

Mendez, R. A.; Tokovinin, A.; Horch, E.

2017-07-01

The prospect of exquisite-precision parallaxes that will be enabled by the Gaia satellite dramatically changes the landscape of observational stellar astrophysics: If one considers the Hipparcos double stars that lie within 250 pc of the Solar system, a parallax determined by Gaia would yield an uncertainty under 1% for all these objects. In this volume, there are 591 Hipparcos double star discoveries and 160 spectroscopic binaries from the Geneva-Copenhagen spectroscopic survey in the declination range of -20° to -90°. These two samples are important as a source of new binaries from which we will derive masses, component luminosities, and effective temperatures in the coming years. The northern hemisphere counterpart of these objects have been systematically observed at the WIYN Telescope by Horch and collaborators (Horch, E. P., van Altena, W. F., Howell, S. B., Sherry, W. H., & Ciardi, D. R. 2011, AJ, 141, 180). On the other hand, Tokovinin has shown the ability of HRCam at the CTIO/SOAR 4m telescope for binary star research. In 2014 we started a speckle survey with SOAR+HRCam that will complement and significantly extend those previous efforts, allowing us to compile a unique all-sky, volume-limited speckle survey of these two primary samples. So far 12 nights (spread over 3 semesters) have been granted through the Chilean reserved time, with lots of binaries confirmed, many new binaries found, and with several multiple systems discovered (Tokovinin et al., 2015, AJ, 150, 50 and 2016, AJ, 151, 153). Our survey, when complete, will open the door to many sensitive tests of stellar evolution theory, and a large number of new points on the MLR. With this we will truly be able to investigate effects such as metallicity and age on the MLR for the first time. In cases where one component has evolved off the main sequence, age determinations will also be possible.

A progenitor binary and an ejected mass donor remnant of faint type Ia supernovae

NASA Astrophysics Data System (ADS)

Geier, S.; Marsh, T. R.; Wang, B.; Dunlap, B.; Barlow, B. N.; Schaffenroth, V.; Chen, X.; Irrgang, A.; Maxted, P. F. L.; Ziegerer, E.; Kupfer, T.; Miszalski, B.; Heber, U.; Han, Z.; Shporer, A.; Telting, J. H.; Gänsicke, B. T.; Østensen, R. H.; O'Toole, S. J.; Napiwotzki, R.

2013-06-01

Type Ia supernovae (SN Ia) are the most important standard candles for measuring the expansion history of the universe. The thermonuclear explosion of a white dwarf can explain their observed properties, but neither the progenitor systems nor any stellar remnants have been conclusively identified. Underluminous SN Ia have been proposed to originate from a so-called double-detonation of a white dwarf. After a critical amount of helium is deposited on the surface through accretion from a close companion, the helium is ignited causing a detonation wave that triggers the explosion of the white dwarf itself. We have discovered both shallow transits and eclipses in the tight binary system CD-30°11223 composed of a carbon/oxygen white dwarf and a hot helium star, allowing us to determine its component masses and fundamental parameters. In the future the system will transfer mass from the helium star to the white dwarf. Modelling this process we find that the detonation in the accreted helium layer is sufficiently strong to trigger the explosion of the core. The helium star will then be ejected at such high velocity that it will escape the Galaxy. The predicted properties of this remnant are an excellent match to the so-called hypervelocity star US 708, a hot, helium-rich star moving at more than 750 km s-1, sufficient for it to leave the Galaxy. The identification of both progenitor and remnant provides a consistent picture of the formation and evolution of underluminous SNIa.

Remote Imaging Projects In Research And Astrophotography With Starpals

NASA Astrophysics Data System (ADS)

Fischer, Audrey; Kingan, J.

2008-05-01

StarPals is a nascent non-profit organization with the goal of providing opportunities for international collaboration between students of all ages within space science research. We believe that by encouraging an interest in the cosmos, the one thing that is truly Universal, from a young age, students will not only further their knowledge of and interest in science but will learn valuable teamwork and life skills. The goal is to foster respect, understanding and appreciation of cultural diversity among all StarPals participants, whether students, teachers, or mentors. StarPals aims to inspire students by providing opportunities in which, more than simply visualizing themselves as research scientists, they can actually become one. The technologies of robotic telescopes, videoconferencing, and online classrooms are expanding the possibilities like never before. In honor of IYA2009, StarPals would like to encourage 400 schools to participate on a global scale in astronomy/cosmology research on various concurrent projects. We will offer in-person or online workshops and training sessions to teach the teachers. We will be seeking publication in scientific journals for some student research. For our current project, the Double Stars Challenge, students use the robotic telescopes to take a series of four images of one of 30 double stars from a list furnished by the US Naval Observatory and then use MPO Canopus software to take distance and position angle measurements. StarPals provides students with hands-on training, telescope time, and software to complete the imaging and measuring. A paper will be drafted from our research data and submitted to the Journal of Double Star Observations. The kids who participate in this project may potentially be the youngest contributors to an article in a vetted scientific journal. Kids rapidly adapt and improve their computer skills operating these telescopes and discover for themselves that science is COOL!

On the Evolution of O(He)-Type Stars

NASA Technical Reports Server (NTRS)

Kruk, Jeffrey W.; Reindl, N.; Rauch, T.; Werner, K.

2012-01-01

O(He) stars represent a small group of four very hot post-AGB stars whose atmospheres are composed of almost pure helium. Their evolution deviates from the hydrogen-deficient post-AGO evolutionary sequence of carbon-dominated stars like e.g. PG 1159 or Wolf- Rayet stars. While (very) late thermal pulse evolutionary models can explain the observed He/C/O abundances in these objects, they do not reproduce He-dominated surface abundances. Currently it seems most likely that the O(He) stars originate from a double helium white dwarf merger and so they could be the successors of the luminous helium-rich sdO-stars. An other possibility is that O(He)-stars could be successors of RCB or EHe stars.

The 2001 U.S. Naval Observatory Double Star CD-Rom. III. The Third Catalog of Interferometric Measurements of Binary Stars

DTIC Science & Technology

2001-12-01

CHARA southern speckle program from 1989 to 1996 (cf. Hartkopf et al. 1996), and by the more recent speckle e†orts of Horch and colleagues (cf. Horch ...Mason, B. D. 2001, Third Catalog of Interferometric Measurements of Binary Stars (CHARA Contrib. No. 4) (Atlanta : Georgia State Univ.) Horch , E

Fifteen DO, PG 1159 and related white dwarf stars in the SDSS, including two DO stars with ultra-high excitation ion lines

NASA Astrophysics Data System (ADS)

Krzesiński, J.; Nitta, A.; Kleinman, S. J.; Harris, H. C.; Liebert, J.; Schmidt, G.; Lamb, D. Q.; Brinkmann, J.

2004-04-01

We report on observations of 15 spectroscopically-identified DO stars from the Sloan Digital Sky Survey (SDSS) database, 13 of which are new discoveries. There are four PG 1159 type stars, two DO stars showing ultra-high excitation ion features (CVI, NVII, OVII, OVIII, NeIX, NeX) likely formed in stellar winds, 6 normal DO stars, one DBO and DBAO star, and one DAO star, which may also be magnetic. Since roughly 60 DO stars were known up to now, this new finding substantially increases the number of known DO white dwarf stars and we expect to at least double the current number of known DO stars by the end of the SDSS. We present each spectrum and provide catalog information (magnitudes, proper motion, coordinates) for each star.

Central exclusive production at RHIC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adamczyk, Leszek; Guryn, Włodek; Turnau, Jacek

The present status and future plans of the physics program of Central Exclusive Production (CEP) at RHIC are described. The measurements are based on the detection of the forward protons from the Double Pomeron Exchange (DPE) process in the Roman Pot system and of the recoil system of charged particles from the DPE process measured in the STAR experiment’s Time Projection Chamber (TPC). The data described here were taken using polarized proton-proton collisions at ps = 200 GeV. The preliminary spectra of two pion and four pion invariant mass reconstructed by STAR TPC in central region of pseudo-rapidity | |more » < 1, are presented. Near future plans to take data with the current system at center-of-mass energy ps = 200 GeV and plans to upgrade the forward proton tagging sys- tem are presented. Also a possible addition of the Roman Pots to the sPHENIX detector is discussed.« less

Identifying Likely Disk-hosting M dwarfs with Disk Detective

NASA Astrophysics Data System (ADS)

Silverberg, Steven; Wisniewski, John; Kuchner, Marc J.; Disk Detective Collaboration

2018-01-01

M dwarfs are critical targets for exoplanet searches. Debris disks often provide key information as to the formation and evolution of planetary systems around higher-mass stars, alongside the planet themselves. However, less than 300 M dwarf debris disks are known, despite M dwarfs making up 70% of the local neighborhood. The Disk Detective citizen science project has identified over 6000 new potential disk host stars from the AllWISE catalog over the past three years. Here, we present preliminary results of our search for new disk-hosting M dwarfs in the survey. Based on near-infrared color cuts and fitting stellar models to photometry, we have identified over 500 potential new M dwarf disk hosts, nearly doubling the known number of such systems. In this talk, we present our methodology, and outline our ongoing work to confirm systems as M dwarf disks.

A survey of stellar families: Multiplicity of solar-type stars

NASA Astrophysics Data System (ADS)

Raghavan, Deepak

I present the results of a comprehensive assessment of companions to 454 solar- type stars within 25 pc. New observational aspects of this work include surveys for (1) very close companions with long-baseline interferometry at the Center for High Angular Resolution Astronomy (CHARA) Array, (2) close companions with speckle interferometry, and (3) wide proper motion companions identified by blinking multi-epoch archival images. I have also obtained and included unpublished results from extensive radial velocity monitoring programs. The many sources utilized enable a thorough evaluation of stellar and brown dwarf companions. The results presented here include eight new companion discoveries, four of which are wide common proper motion pairs discovered by blinking archival images, and four more are from the spectroscopic data. The overall observed fractions of single, double, triple, and higher order systems are 57%±3%, 33%±2%, 8%±1%, and 3%±1%, respectively, counting all stellar and brown dwarf companions. The incompleteness analysis indicates that only a few undiscovered companions remain in this well-studied sample, showing that a majority of the solar-type stars are single. Bluer, more massive stars are more likely to have companions than redder, less massive ones. I confirm earlier expectations that more active stars are more likely to have companions. A preliminary, but important indication is that brown dwarfs, like planets, prefer stars with higher metallicity, tentatively suggesting that brown dwarfs may form like planets when they are companions to stars. The period distribution is unimodal and roughly Gaussian with peak and median values of about 300 years. The period-eccentricity relation shows a roughly flat distribution beyond the circularization limit of about 12 days. The mass- ratio distribution shows a clear discontinuity near a value of one, indicating a preference for twins, which are not confined to short orbital periods, suggesting that stars form by multiple formation mechanisms. The ratio of planet hosts among single, binary, and multiple systems are statistically indistinguishable, suggesting that planets are as likely to form around single stars as they are around components of binary or multiple systems at sufficiently wide separations. INDEX WORDS: Stellar multiplicity, Binary stars, Solar-type stars, Solar neighborhood, Exoplanet systems, Brown dwarfs, Survey, Long baseline interferometry, Radial velocity

USNO Image and Catalog Archive Server - Naval Oceanography Portal

Science.gov Websites

are here: Home › USNO › Astrometry › Optical/IR Products › USNO Image and Catalog Archive Server USNO Logo USNO Navigation Optical/IR Products NOMAD UCAC URAT USNO-B1.0 Double Stars Solar System Link Disclaimer This is an official U.S. Navy web site. Security & Privacy Policy Veterans Crisis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mamajek, Eric E.; Bartlett, Jennifer L.; Finch, Charlie T.

LP 876-10 is a nearby active M4 dwarf in Aquarius at a distance of 7.6 pc. The star is a new addition to the 10 pc census, with a parallax measured via the REsearch Consortium On Nearby Stars (RECONS) astrometric survey on the Small and Moderate Aperture Research Telescope System's 0.9 m telescope. We demonstrate that the astrometry, radial velocity, and photometric data for LP 876-10 are consistent with the star being a third bound stellar component to the Fomalhaut multiple system, despite the star lying nearly 6° away from Fomalhaut A in the sky. The three-dimensional separation of LPmore » 876-10 from Fomalhaut is only 0.77 ± 0.01 pc, and 0.987 ± 0.006 pc from TW PsA (Fomalhaut B), well within the estimated tidal radius of the Fomalhaut system (1.9 pc). LP 876-10 shares the motion of Fomalhaut within ∼1 km s{sup –1}, and we estimate an interloper probability of ∼10{sup –5}. Neither our echelle spectroscopy nor astrometry are able to confirm the close companion to LP 876-10 reported in the Washington Double Star Catalog (WSI 138). We argue that the Castor Moving Group to which the Fomalhaut system purportedly belongs, is likely to be a dynamical stream, and hence membership to the group does not provide useful age constraints for group members. LP 876-10 (Fomalhaut C) has now risen from obscurity to become a rare example of a field M dwarf with well-constrained age (440 ± 40 Myr) and metallicity. Besides harboring a debris disk system and candidate planet, Fomalhaut now has two of the widest known stellar companions.« less

Optical Photometry and X-Ray Monitoring of the ``Cool Algol'' BD +05°706: Determination of the Physical Properties

NASA Astrophysics Data System (ADS)

Torres, Guillermo; Mader, Jeff A.; Marschall, Laurence A.; Neuhäuser, Ralph; Duffy, Alaine S.

2003-06-01

We present new photometric observations in the BVRI bands of the double-lined eclipsing binary BD +05°706 conducted over three observing seasons, as well as new X-ray observations obtained with ROSAT covering a full orbital cycle (P=18.9 days). A detailed light-curve analysis of the optical data shows the system to be semidetached, confirming indications from an earlier analysis by Torres et al. (published in 1998), with the less massive and cooler star filling its Roche lobe. The system is a member of the rare class of cool Algol systems, which are different from the ``classical'' Algol systems in that the mass-gaining component is also a late-type star rather than a B- or A-type star. By combining the new photometry with a reanalysis of the spectroscopic observations reported by Torres et al., we derive accurate absolute masses for the components of M1=2.633+/-0.028 Msolar and M2=0.5412+/-0.0093 Msolar, radii of R1=7.55+/-0.20 Rsolar and R2=11.02+/-0.21 Rsolar, as well as effective temperatures of 5000+/-100 and 4640+/-150 K, for the primary and secondary, respectively. There are obvious signs of activity (spottedness) in the optical light curve of the binary. Our X-ray light curve clearly shows the primary eclipse but not the secondary eclipse, suggesting that the primary star is the dominant source of the activity in the system. The depth and duration of the eclipse allow us to infer some of the properties of the X-ray-emitting region around that star.

Series production of next-generation guide-star lasers at TOPTICA and MPBC

NASA Astrophysics Data System (ADS)

Enderlein, Martin; Friedenauer, Axel; Schwerdt, Robin; Rehme, Paul; Wei, Daoping; Karpov, Vladimir; Ernstberger, Bernhard; Leisching, Patrick; Clements, Wallace R. L.; Kaenders, Wilhelm G.

2014-07-01

Large telescopes equipped with adaptive optics require high power 589-nm continuous-wave sources with emission linewidths of ~5 MHz. These guide-star lasers should be highly reliable and simple to operate and maintain for many years at the top of a mountain facility. After delivery of the first 20-W systems to our lead customer ESO, TOPTICA and MPBC have begun series production of next-generation sodium guide-star lasers. The chosen approach is based on ESO's patented narrow-band Raman fiber amplifier (RFA) technology [1]. A master oscillator signal from a TOPTICA 50-mW, 1178-nm diode laser, with stabilized emission frequency and linewidth of ~ 1 MHz, is amplified in an MPBC polarization-maintaining (PM) RFA pumped by a high-power 1120-nm PM fiber laser. With efficient stimulated Brillouin scattering suppression, an unprecedented 40 W of narrow-band RFA output has been obtained. This is spatially mode-matched into a patented resonant-cavity frequency doubler providing also the repumper light [2]. With a diffraction-limited output beam and doubling efficiencies < 80%, all ESO design goals have been easily fulfilled. Together with a wall-plug efficiency of < 3%, including all system controls, and a cooling liquid flow of only 5 l/min, the modular, turn-key, maintenance-free and compact system design allows a direct integration with a launch telescope. With these fiber-based guide star lasers, TOPTICA for the first time offers a fully engineered, off-the-shelf guide star laser system for ground-based optical telescopes. Here we present a comparison of test results of the first batch of laser systems, demonstrating the reproducibility of excellent optical characteristics.

Using VizieR/Aladin to Measure Neglected Double Stars

NASA Astrophysics Data System (ADS)

Harshaw, Richard

2013-04-01

The VizierR service of the Centres de Donnes Astronomiques de Strasbourg (France) offers amateur astronomers a treasure trove of resources, including access to the most current version of the Washington Double Star Catalog (WDS) and links to tens of thousands of digitized sky survey plates via the Aladin Java applet. These plates allow the amateur to make accurate measurements of position angle and separation for many neglected pairs that fall within reasonable tolerances for the use of Aladin. This paper presents 428 measurements of 251 neglected pairs from the WDS.

Kitt Peak speckle camera

NASA Technical Reports Server (NTRS)

Breckinridge, J. B.; Mcalister, H. A.; Robinson, W. G.

1979-01-01

The speckle camera in regular use at Kitt Peak National Observatory since 1974 is described in detail. The design of the atmospheric dispersion compensation prisms, the use of film as a recording medium, the accuracy of double star measurements, and the next generation speckle camera are discussed. Photographs of double star speckle patterns with separations from 1.4 sec of arc to 4.7 sec of arc are shown to illustrate the quality of image formation with this camera, the effects of seeing on the patterns, and to illustrate the isoplanatic patch of the atmosphere.

Jonckheere Double Star Photometry – Part VIII: Sextans

NASA Astrophysics Data System (ADS)

Knapp, Wilfried

2018-01-01

If any double star discoverer is in urgent need of photometry then it is Jonckheere. There are over 3000 Jonckheere objects listed in the WDS catalog and a good part of them with magnitudes obviously far too bright. This report covers the Jonckheere objects in the constellation Sextans. One image per object was taken with V-filter to allow for visual magnitude measurement by differential photometry. All objects were additionally checked for common proper motion and a good part of the objects qualify indeed as potential CPM pairs.

Jonckheere Double Star Photometry - Part XI: Lepus & Vulpecula

NASA Astrophysics Data System (ADS)

Knapp, Wilfried; Nanson, John

2018-07-01

If any double star discoverer is in urgent need of photometry then it is Jonckheere. There are over 3000 Jonckheere objects listed in the WDS catalog and a good part of them with magnitudes obviously far too bright. This report covers the Jonckheere objects in the constellations Lep and Vul. At least one image per object was taken with V-filter to allow for visual magnitude measurement by differential photometry. All objects were additionally checked for common proper motion. Five qualify indeed as most probably CPM pairs with an additional five as potential CPM pairs.

DSLR Double Star Astrometry Using an Alt-Az Telescope

NASA Astrophysics Data System (ADS)

Frey, Thomas; Haworth, David

2014-07-01

The goal of this project was to determine if the double star's angular separation and position angle measurements could be successfully measured with a motor driven, alt-azimuth Dobsonian-mounted Newtonian telescope (without a field rotator), and a digital single-lens reflex (DSLR) camera. Additionally, the project was constrained by using as much existing equipment as much as possible, including an Apple MacBook Pro laptop and a Canon T2i camera. This project was additionally challenging because the first author had no experience with astrophotography.

Higher Incentive Payments in Medicare Advantage's Pay-for-Performance Program Did Not Improve Quality But Did Increase Plan Offerings.

PubMed

Layton, Timothy J; Ryan, Andrew M

2015-12-01

To evaluate the effects of the size of financial bonuses on quality of care and the number of plan offerings in the Medicare Advantage Quality Bonus Payment Demonstration. Publicly available data from CMS from 2009 to 2014 on Medicare Advantage plan quality ratings, the counties in the service area of each plan, and the benchmarks used to construct plan payments. The Medicare Advantage Quality Bonus Payment Demonstration began in 2012. Under the Demonstration, all Medicare Advantage plans were eligible to receive bonus payments based on plan-level quality scores (star ratings). In some counties, plans were eligible to receive bonus payments that were twice as large as in other counties. We used this variation in incentives to evaluate the effects of bonus size on star ratings and the number of plan offerings in the Demonstration using a differences-in-differences identification strategy. We used matching to create a comparison group of counties that did not receive double bonuses but had similar levels of the preintervention outcomes. Results from the difference-in-differences analysis suggest that the receipt of double bonuses was not associated with an increase in star ratings. In the matched sample, the receipt of double bonuses was associated with a statistically insignificant increase of +0.034 (approximately 1 percent) in the average star rating (p > .10, 95 percent CI: -0.015, 0.083). In contrast, the receipt of double bonuses was associated with an increase in the number of plans offered. In the matched sample, the receipt of double bonuses was associated with an overall increase of +0.814 plans (approximately 5.8 percent) (p < .05, 95 percent CI: 0.078, 1.549). We estimate that the double bonuses increased payments by $3.43 billion over the first 3 years of the Demonstration. At great expense to Medicare, double bonuses in the Medicare Advantage Quality Bonus Payment Demonstration were not associated with improved quality but were associated with more plan offerings. © Health Research and Educational Trust.

CCD Measurements and Linear Solution for WDS 02041-7115

NASA Astrophysics Data System (ADS)

Hensley, Hagan; Giles, Ava; Mayhue, Lance; Badami, Umar Ahmed; Tock, Kalée.

2018-01-01

The double star system WDS 02041-7115 or HJ 3483 was imaged using the Skynet Robotic Telescope Network on Jan 31 (Besselian date 2017.085). Using AstroImageJ, the secondary was measured to have a position angle of 263° and a separation of 7.6". Because the distance to the primary is known, along with the spectral classes and proper motions of both, we show that a gravitational relationship is not only unlikely, but mathematically impossible for these stars. Even if the secondary is at the same distance as the primary, its proper motion rela-tive to the primary would exceed its escape velocity. We also present a linear solution for the pair.

MM Herculis - An eclipsing binary of the RS CVn

NASA Technical Reports Server (NTRS)

Sowell, J. R.; Hall, D. S.; Henry, G. W.; Burke, E. W., Jr.; Milone, E. F.

1983-01-01

V, B and U differential photoelectric photometry has been obtained for the RS Canum Venaticorum-class eclipsing binary star MM Her, with the light outside the eclipse being Fourier-analyzed to study wave migration and amplitude. These, together with the mean light level of the system, have been monitored from 1976 through 1980. Observations within the eclipse have revealed eclipses to be partial, rather than total as previously thought. The geometric elements of the presently rectified light curve are forced on the pre-1980 light curves and found to be compatible. With these elements, and previously obtained double line radial velocity curves, new absolute dimensions of 1.18 solar masses and 1.58 solar radii are calculated for the hotter star and 1.27 solar masses and 2.83 solar radii for the cooler star. The plotting of color indices on the color-color curve indicates G2V and K2IV spectral types.

Stereo–SCIDAR System for Improvement of Adaptive Optics Space Debris-tracking Activities

NASA Astrophysics Data System (ADS)

Thorn, E.; Korkiakoski, V.; Grosse, D.; Bennet, F.; Rigaut, F.; d'Orgeville, C.; Munro, J.; Smith, C.

The Research School of Astronomy and Astrophysics (RSAA) in conjunction with the Space Environment Research Center (SERC) has developed a single detector stereo-SCIDAR (SCIntillation Detection And Ranging) system to characteristic atmospheric turbulence. We present the mechanical and optical design, as well as some preliminary results. SERC has a vested interest in space situational awareness (SSA), with a focus on space debris. RSAA is developing adaptive optics (AO) systems to aid in the detection of, ranging to, and orbit propagation of said debris. These AO systems will be directly improved by measurements provided by the usage of the stereo-SCIDAR system developed. SCIDAR is a triangulation technique that utilises a detector to take short exposures of the scintillation pupil patterns of a double star. There is an altitude at which light propagating from these stars passes through the same "patch" of turbulence in Earth's atmosphere: this patch induces wavefront aberrations that are projected onto different regions of the scintillation pupil patterns. An auto-correlation function is employed to extract the height at which the turbulence was introduced into the wavefronts. Unlike stereo-SCIDAR systems developed by other organisations - which utilise a dedicated detector for each of the pupil images - our system will use a pupil-separating prism and a single detector to image both pupils. Using one detector reduces cost as well as design and optical complexity. The system has been installed (in generalised SCIDAR form with a stereo- SCIDAR upgrade scheduled for nest year), tested and operated on the EOS Space Systems' 1.8m debris-ranging telescope at Mount Stromlo, Canberra. Specifically, it was designed to observe double stars separated by 5 to 25 arcseconds with a greater magnitude difference tolerance than conventional SCIDAR, that conventional difference being roughly 2.5. We anticipate taking measurements of turbulent layers up to 15km in altitude with a resolution of approximately 1km. Our system will also be sensitive to ground layer atmospheric turbulence. Here we present details of the optical and mechanical design in addition to preliminary results.

Observations of suspected low-mass post-T Tauri stars and their evolutionary status

NASA Technical Reports Server (NTRS)

Mundt, R.; Walter, F. M.; Feigelson, E. D.; Finkenzeller, U.; Herbig, G. H.; Odell, A. P.

1983-01-01

The results of a study of five X-ray discovered weak emission pre-main-sequence stars in the Taurus-Auriga star formation complex are presented. All are of spectral type K7-M0, and about 1-2 mag above the main sequence. One is a double-lined spectroscopic binary, the first spectroscopic binary PMS star to be confirmed. The ages, masses, and radii of these stars as determined by photometry and spectroscopy are discussed. The difference in emission strength between these and the T Tauri stars is investigated, and it is concluded that these 'post-T Tauri' stars do indeed appear more evolved than the T Tauri stars, although there is no evidence of any significant difference in ages.

Measurements of 42 Wide CPM Pairs with a CCD

NASA Astrophysics Data System (ADS)

Harshaw, Richard

2015-11-01

This paper addresses the use of a Skyris 618C color CCD camera as a means of obtaining data for analysis in the measurement of wide common proper motion stars. The equipment setup is described and data collection procedure outlined. Results of the measures of 42 CPM stars are presented, showing the Skyris is a reliable device for the measurement of double stars.

Close Encounters of the Stellar Kind

NASA Astrophysics Data System (ADS)

2003-07-01

NASA's Chandra X-ray Observatory has confirmed that close encounters between stars form X-ray emitting, double-star systems in dense globular star clusters. These X-ray binaries have a different birth process than their cousins outside globular clusters, and should have a profound influence on the cluster's evolution. A team of scientists led by David Pooley of the Massachusetts Institute of Technology in Cambridge took advantage of Chandra's unique ability to precisely locate and resolve individual sources to determine the number of X-ray sources in 12 globular clusters in our Galaxy. Most of the sources are binary systems containing a collapsed star such as a neutron star or a white dwarf star that is pulling matter off a normal, Sun-like companion star. "We found that the number of X-ray binaries is closely correlated with the rate of encounters between stars in the clusters," said Pooley. "Our conclusion is that the binaries are formed as a consequence of these encounters. It is a case of nurture not nature." A similar study led by Craig Heinke of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. confirmed this conclusion, and showed that roughly 10 percent of these X-ray binary systems contain neutron stars. Most of these neutron stars are usually quiet, spending less than 10% of their time actively feeding from their companion. NGC 7099 NGC 7099 A globular cluster is a spherical collection of hundreds of thousands or even millions of stars buzzing around each other in a gravitationally-bound stellar beehive that is about a hundred light years in diameter. The stars in a globular cluster are often only about a tenth of a light year apart. For comparison, the nearest star to the Sun, Proxima Centauri, is 4.2 light years away. With so many stars moving so close together, interactions between stars occur frequently in globular clusters. The stars, while rarely colliding, do get close enough to form binary star systems or cause binary stars to exchange partners in intricate dances. The data suggest that X-ray binary systems are formed in dense clusters known as globular clusters about once a day somewhere in the universe. Observations by NASA's Uhuru X-ray satellite in the 1970's showed that globular clusters seemed to contain a disproportionately large number of X-ray binary sources compared to the Galaxy as a whole. Normally only one in a billion stars is a member of an X-ray binary system containing a neutron star, whereas in globular clusters, the fraction is more like one in a million. The present research confirms earlier suggestions that the chance of forming an X-ray binary system is dramatically increased by the congestion in a globular cluster. Under these conditions two processes, known as three-star exchange collisions, and tidal captures, can lead to a thousandfold increase in the number of X-ray sources in globular clusters. 47 Tucanae 47 Tucanae In an exchange collision, a lone neutron star encounters a pair of ordinary stars. The intense gravity of the neutron star can induce the most massive ordinary star to "change partners," and pair up with the neutron star while ejecting the lighter star. A neutron star could also make a grazing collision with a single normal star, and the intense gravity of the neutron star could distort the gravity of the normal star in the process. The energy lost in the distortion, could prevent the normal star from escaping from the neutron star, leading to what is called tidal capture. "In addition to solving a long-standing mystery, Chandra data offer an opportunity for a deeper understanding of globular cluster evolution," said Heinke. "For example, the energy released in the formation of close binary systems could keep the central parts of the cluster from collapsing to form a massive black hole." NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for the Office of Space Science, NASA Headquarters, Washington. Northrop Grumman of Redondo Beach, Calif., formerly TRW, Inc., was the prime development contractor for the observatory. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass. The image and additional information are available at: http://chandra.harvard.edu and http://chandra.nasa.gov

Efficient Geometric Probabilities of Multi-transiting Systems, Circumbinary Planets, and Exoplanet Mutual Events

NASA Astrophysics Data System (ADS)

Brakensiek, Joshua; Ragozzine, D.

2012-10-01

The transit method for discovering extra-solar planets relies on detecting regular diminutions of light from stars due to the shadows of planets passing in between the star and the observer. NASA's Kepler Mission has successfully discovered thousands of exoplanet candidates using this technique, including hundreds of stars with multiple transiting planets. In order to estimate the frequency of these valuable systems, our research concerns the efficient calculation of geometric probabilities for detecting multiple transiting extrasolar planets around the same parent star. In order to improve on previous studies that used numerical methods (e.g., Ragozzine & Holman 2010, Tremaine & Dong 2011), we have constructed an efficient, analytical algorithm which, given a collection of conjectured exoplanets orbiting a star, computes the probability that any particular group of exoplanets are transiting. The algorithm applies theorems of elementary differential geometry to compute the areas bounded by circular curves on the surface of a sphere (see Ragozzine & Holman 2010). The implemented algorithm is more accurate and orders of magnitude faster than previous algorithms, based on comparison with Monte Carlo simulations. Expanding this work, we have also developed semi-analytical methods for determining the frequency of exoplanet mutual events, i.e., the geometric probability two planets will transit each other (Planet-Planet Occultation) and the probability that this transit occurs simultaneously as they transit their star (Overlapping Double Transits; see Ragozzine & Holman 2010). The latter algorithm can also be applied to calculating the probability of observing transiting circumbinary planets (Doyle et al. 2011, Welsh et al. 2012). All of these algorithms have been coded in C and will be made publicly available. We will present and advertise these codes and illustrate their value for studying exoplanetary systems.

PALFA Discovery of a Highly Relativistic Double Neutron Star Binary

NASA Astrophysics Data System (ADS)

Stovall, K.; Freire, P. C. C.; Chatterjee, S.; Demorest, P. B.; Lorimer, D. R.; McLaughlin, M. A.; Pol, N.; van Leeuwen, J.; Wharton, R. S.; Allen, B.; Boyce, M.; Brazier, A.; Caballero, K.; Camilo, F.; Camuccio, R.; Cordes, J. M.; Crawford, F.; Deneva, J. S.; Ferdman, R. D.; Hessels, J. W. T.; Jenet, F. A.; Kaspi, V. M.; Knispel, B.; Lazarus, P.; Lynch, R.; Parent, E.; Patel, C.; Pleunis, Z.; Ransom, S. M.; Scholz, P.; Seymour, A.; Siemens, X.; Stairs, I. H.; Swiggum, J.; Zhu, W. W.

2018-02-01

We report the discovery and initial follow-up of a double neutron star (DNS) system, PSR J1946+2052, with the Arecibo L-Band Feed Array pulsar (PALFA) survey. PSR J1946+2052 is a 17 ms pulsar in a 1.88 hr, eccentric (e = 0.06) orbit with a ≳1.2 M ⊙ companion. We have used the Jansky Very Large Array to localize PSR J1946+2052 to a precision of 0.″09 using a new phase binning mode. We have searched multiwavelength catalogs for coincident sources but did not find any counterparts. The improved position enabled a measurement of the spin period derivative of the pulsar (\\dot{P}=9+/- 2× {10}-19); the small inferred magnetic field strength at the surface (B S = 4 × 109 G) indicates that this pulsar has been recycled. This and the orbital eccentricity lead to the conclusion that PSR J1946+2052 is in a DNS system. Among all known radio pulsars in DNS systems, PSR J1946+2052 has the shortest orbital period and the shortest estimated merger timescale, 46 Myr; at that time it will display the largest spin effects on gravitational-wave waveforms of any such system discovered to date. We have measured the advance of periastron passage for this system, \\dot{ω }=25.6+/- 0.3 \\deg {yr}}-1, implying a total system mass of only 2.50 ± 0.04 M ⊙, so it is among the lowest-mass DNS systems. This total mass measurement combined with the minimum companion mass constrains the pulsar mass to ≲1.3 M ⊙.

The Effect of Pilates Exercise on Trunk and Postural Stability and Throwing Velocity in College Baseball Pitchers: Single Subject Design

PubMed Central

Howe, Katherine

2007-01-01

Background Baseball pitchers need trunk strength to maximize performance. The Pilates method of exercise is gaining popularity throughout the country as a fitness and rehabilitation method of exercise. However, very few studies exist that examine the effects of the Pilates method of exercise on trunk strength or performance. Objectives Using a single subject, multiple baseline across subjects design, this study examines the effects of the Pilates method of exercise on performance of double leg lowering, star excursion balance test, and throwing velocity in college-aged baseball pitchers. Methods A convenience sample of three college baseball pitchers served as the subjects for this single subject design study. For each subject, double leg lowering, star excursion balance test, and throwing speed were measured prior to the introduction of the intervention. When baseline test values showed consistent performance, the intervention was introduced to one subject at a time. Intervention was introduced to the other subjects over a period of 4 weeks as they also demonstrated consistent performance on the baseline tests. Intervention was continued with periodic tests for the remainder of the 10 week trial. Results Each subject improved in performance on double leg lowering (increased 24.43-32.7%) and star excursion balance test (increased 4.63-17.84%) after introduction of the intervention. Throwing speed improved in two of the three subjects (up to 5.61%). Discussion and Conclusions The Pilates method of exercise may contribute to improved performance in double leg lowering, star excursion balance tests, and throwing speed in college baseball pitchers. PMID:21522199

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tokovinin, Andrei, E-mail: atokovinin@ctio.noao.edu

Seven spectroscopic orbits in nearby solar-type multiple stars are presented. The primary of the chromospherically active star HIP 9642 is a 4.8 day double-lined pair; the outer 420 year visual orbit is updated, but remains poorly constrained. HIP 12780 is a quadruple system consisting of the resolved 6.7 year pair FIN 379 Aa,Ab, for which the combined orbit, masses, and orbital parallax are determined here, and the single-lined binary Ba,Bb with a period of 27.8 days. HIP 28790 is a young quintuple system composed of two close binaries, Aa,Ab and Ba,Bb, with periods of 221 and 13 days, respectively, and a singlemore » distant component C. Its subsystem Ba,Bb is peculiar, having a spectroscopic mass ratio of 0.89 but a magnitude difference of ∼2.2 mag. HIP 64478 also contains five stars: the A-component is a 29 year visual pair with a previously known 4 day twin subsystem, while the B-component is a contact binary with a period of 5.8 hr, seen nearly pole-on.« less

HUBBLE SEES CHANGES IN GAS SHELL AROUND NOVA CYGNI 1992

NASA Technical Reports Server (NTRS)

2002-01-01

The European Space Agency's ESA Faint Object Camera utilizing the corrective optics provided by NASA's COSTAR (Corrective Optics Space Telescope Axial Replacement), has given astronomers their best look yet at a rapidly ballooning bubble of gas blasted off a star. The shell surrounds Nova Cygni 1992, which erupted on February 19, 1992. A nova is a thermonuclear explosion that occurs on the surface of a white dwarf star in a double star system. The new HST image [right] reveals an elliptical and slightly lumpy ring-like structure. The ring is the edge of a bubble of hot gas blasted into space by the nova. The shell is so thin that the FOC does not resolve its true thickness, even with HST's restored vision. An HST image taken on May 31 1993, [left] 467 days after the explosion, provided the first glimpse of the ring and a mysterious bar-like structure. But the image interpretation was severely hampered by HST's optical aberration, that scattered light from the central star which contaminated the ring's image. A comparison of the pre and post COSTAR/FOC images reveals that the ring has evolved in the seven months that have elapsed between the two observations. The ring has expanded from a diameter of approximately 74 to 96 billion miles. The bar-like structure seen in the earlier HST image has disappear. These changes might confirm theories that the bar was produced by a dense layer of gas thrown off in the orbital plane of the double star system. The gas has subsequently grown more tenuous and so the bar has faded. The ring has also grown noticeably more oblong since the earlier image. This suggests the hot gas is escaping more rapidly above and below the system's orbital plane. As the gas continues escaping the ring should grow increasingly egg-shaped in the coming years. HST's newly improved sensitivity and high resolution provides a unique opportunity to understand the novae by resolving the effects of the explosion long before they can be resolved in ground based telescopes. Nova Cygni is 10,430 light years away (as measured directly from the ring's diameter), and located in the summer constellation Cygnus the Swan. Credit: F. Paresce, R. Jedrzejewski (STScI) NASA/ESA PHOTO RELEASE NO.: STScI-PR94-06

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tauris, T. M.; Langer, N.; Moriya, T. J.

Recent discoveries of weak and fast optical transients raise the question of their origin. We investigate the minimum ejecta mass associated with core-collapse supernovae (SNe) of Type Ic. We show that mass transfer from a helium star to a compact companion can produce an ultra-stripped core which undergoes iron core collapse and leads to an extremely fast and faint SN Ic. In this Letter, a detailed example is presented in which the pre-SN stellar mass is barely above the Chandrasekhar limit, resulting in the ejection of only ∼0.05-0.20 M {sub ☉} of material and the formation of a low-mass neutron star (NS).more » We compute synthetic light curves of this case and demonstrate that SN 2005ek could be explained by our model. We estimate that the fraction of such ultra-stripped to all SNe could be as high as 10{sup –3}-10{sup –2}. Finally, we argue that the second explosion in some double NS systems (for example, the double pulsar PSR J0737–3039B) was likely associated with an ultra-stripped SN Ic.« less

Near-IR Polarized Scattered Light Imagery of the DoAr 28 Transitional Disk

NASA Technical Reports Server (NTRS)

Rich, Evan A.; Wisiniewski, John P.; Mayama, Satoshi; Brandt, Timothy D.; Hashimoto, Jun; Kudo, Tomoyuki; Kusakabe, Nobuhiko; Espaillat, Catherine; Serabyn, Eugene; Grady, Carol A.;

The Expanding Bipolar Conic Shell of the Symbiotic Star AG Peg

NASA Astrophysics Data System (ADS)

Lee, Seong-Jae; Hyung, Siek

2018-06-01

Symbiotic stars are the most interesting since some systems are believed to host the most massive white dwarf, like SN Ia progenitors. Most recently, Lee and Hyung (2018, LH18) proposed a bipolar conic shell structure for the observed high expansion Hα and Hβ line profiles and other double peak lines observed in 1998 September (phase φ = 10.24): the physical conditions for the white dwarf luminosity and the ionized HII zone, responsible for double Gaussian optical lines including Balmer and Lyman line fluxes, were taken from the P-I model with gas density, nH = 109.85 cm-3 , while the column density for the scattering neutral zone was derived from the broader line components based on the result by Monte Carlo simulations. In this investigation, we examined whether the expanding shells of the bipolar conical geometry as proposed by LH18 would be able to form the other Hα and Hβ line profiles observed in other phases, φ = 11.56 and 11.98 (in 2001 August and 2002 August). We look into the kinematical property of the bipolar conic shell structure responsible for the HII and HI zones and then we discuss the secular variation of the broad line feature and the origin of the bipolar cone, i.e., part of a common envelope formed through the mass inflows from the giant star.

Resolution and Orbit Reconstruction of Spectroscopic Binary Stars with the Palomar Testbed Interferometer

NASA Astrophysics Data System (ADS)

Boden, A. F.; Lane, B. F.; Creech-Eakman, M. J.; Queloz, D.; Koresko, C. D.

2000-05-01

The Palomar Testbed Interferometer (PTI) is a long-baseline near-infrared interferometer located at Palomar Observatory. For the past several years we have had an ongoing program of resolving and reconstructing the visual and physical orbits of spectroscopic binary stars with PTI, with the goal of obtaining precise dynamical mass estimates and other physical parameters. We will present a number of new visual and physical orbit determinations derived from integrated reductions of PTI visibility and archival and new spectroscopic radial velocity data. The systems for which we will discuss our orbit models are: iota Pegasi (HD 210027), 64 Psc (HD 4676), 12 Boo (HD 123999), 75 Cnc (HD 78418), 47 And (HD 8374), HD 205539, BY Draconis (HDE 234677), and 3 Boo (HD 120064), and 3 Boo (HD 120064). All of these systems are double-lined binary systems (SB2), and integrated astrometric/radial velocity orbit modeling provides precise fundamental parameters (mass, luminosity) and system distance determinations comparable with Hipparcos precisions.

USNO CCD Astrograph Catalog (UCAC) - Naval Oceanography Portal

Science.gov Websites

are here: Home › USNO › Astrometry › Optical/IR Products › UCAC USNO Logo USNO Navigation Optical/IR Products NOMAD UCAC URAT USNO-B1.0 Double Stars Solar System Bodies USNO Image and Catalog 2MASS near-IR photometry (as in previous releases) UCAC4 now includes APASS 5-band photometry. The APASS

Energy Star program benefits Con Edison

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

Impressed with savings in energy costs achieved after upgrading the lighting and air conditioning systems at its Manhattan headquarters, Home Box Office (HBO) wanted to do more, James Flock, vice president for computer and office systems, contacted Con Edison Co. of New York in March 1991 to determine what the company could do to save money by reducing energy consumed by personal computers. Arthur Kressner, Con Edison Research and Development manager contacted industry organizations and manufacturers for advice, but was told only to shut off computers at night and on weekends. Kressner arranged a series of meetings with IBM andmore » the Electric Power Research Institute (EPRI) to discuss the issue, then approached the U.S. Environmental Protection Agency (EPA), which was designing a program to promote the introduction and use of energy-efficient office equipment. In 1992, the EPA announced the Energy Star program for PCs, enabling manufacturers to display the Energy Star logo on machines meeting program criteria, including the ability to enter a sleep mode in which neither the computer nor monitor consume more than 30 W or electricity. Industry experts estimate national energy consumption by office equipment could double by the year 2000, but Energy Star equipment is expected to improve efficiency and help maintain electric loads.« less

Tatooines Future: The Eccentric Response of Keplers Circumbinary Planets to Common-Envelope Evolution of their Host Stars

NASA Technical Reports Server (NTRS)

Kostov, Veselin B.; Moore, Keavin; Tamayo, Daniel; Jayawardhana, Ray; Rinehart, Stephen A.

2016-01-01

Inspired by the recent Kepler discoveries of circumbinary planets orbiting nine close binary stars, we explore the fate of the former as the latter evolve off the main sequence. We combine binary star evolution models with dynamical simulations to study the orbital evolution of these planets as their hosts undergo common-envelope stages, losing in the process a tremendous amount of mass on dynamical timescales. Five of the systems experience at least one Roche-lobe overflow and common-envelope stages (Kepler-1647 experiences three), and the binary stars either shrink to very short orbits or coalesce; two systems trigger a double-degenerate supernova explosion. Kepler's circumbinary planets predominantly remain gravitationally bound at the end of the common-envelope phase, migrate to larger orbits, and may gain significant eccentricity; their orbital expansion can be more than an order of magnitude and can occur over the course of a single planetary orbit. The orbits these planets can reach are qualitatively consistent with those of the currently known post-common-envelope, eclipse-time variations circumbinary candidates. Our results also show that circumbinary planets can experience both modes of orbital expansion (adiabatic and non-adiabatic) if their host binaries undergo more than one common-envelope stage; multiplanet circumbinary systems like Kepler-47 can experience both modes during the same common-envelope stage. Additionally, unlike Mercury orbiting the Sun, a circumbinary planet with the same semi-major axis can survive the common envelope evolution of a close binary star with a total mass of 1 Solar Mass.

Am stars and the influence of binarity on infall

NASA Astrophysics Data System (ADS)

Cowley, Charles R.

2016-01-01

We explore an old idea for the origin of Am star anomalies, possibly related to observations of pollution in white dwarfs (Jura & Young, ARAA, 42, 45, 2014; Gansicke, et al., Arxiv:1505.03142). It must be noted that infall of an earthlike body can explain some, but not all of the abundance anomalies of Am stars.The ingestion of earthlike material by an a star should have observable effects that are larger than for solar-type stars. We follow dynamical arguments discussed, e.g. by Debes, et al. ApJ., 747, 148, 2012), and postulate that gravitational interactions will produce an infalling stream of low angularmomentum bodies.Note that most if not all Am stars are binary. Here we investigate only whether there is an increased frequency of collisions with a close binary relative to a single star.We make quantitative estimates, using analytical 2-body solutions and restricted 3-body calculations with parameters similar to those of the eclipsing Am pair Beta Aur,or WW Aur. We use initial values for the binary similar to those which would lead to a certain collision on a (4M_sun) single star for a parabolic trajectory. All calculations begin with a distance from the center of mass along the axis of a paraboloid of revolution at 3 or 5 AU and such that a marginal collision occurs with a single star. The perpendicular area of this figure is a cross section for a collision. We sample trajectories starting within and near this cross section, for double starsystems. Based on many trials we find it about equally likely-- relative to a single star--that an incoming body will be ejected from the system than that it will collide with one of the stars. Although we have sampled only a fraction of possible parameter space, we find no basis to expect that the binarity of the Am systems makes them more likely to have ingested planetary material.Infall should probably still be considered, along with the generally accepted diffusion scenario, but it does not appear that the binarity of Am stars makes infall significantly more relevant.

HD 66051: the first eclipsing binary hosting an early-type magnetic star

NASA Astrophysics Data System (ADS)

Kochukhov, O.; Johnston, C.; Alecian, E.; Wade, G. A.

2018-05-01

Early-type magnetic stars are rarely found in close binary systems. No such objects were known in eclipsing binaries prior to this study. Here we investigated the eclipsing, spectroscopic double-lined binary HD 66051, which exhibits out-of-eclipse photometric variations suggestive of surface brightness inhomogeneities typical of early-type magnetic stars. Using a new set of high-resolution spectropolarimetric observations, we discovered a weak magnetic field on the primary and found intrinsic, element-dependent variability in its spectral lines. The magnetic field structure of the primary is dominated by a nearly axisymmetric dipolar component with a polar field strength Bd ≈ 600 G and an inclination with respect to the rotation axis of βd = 13°. A weaker quadrupolar component is also likely to be present. We combined the radial velocity measurements derived from our spectra with archival optical photometry to determine fundamental masses (3.16 and 1.75 M⊙) and radii (2.78 and 1.39 R⊙) with a 1-3% precision. We also obtained a refined estimate of the effective temperatures (13000 and 9000 K) and studied chemical abundances for both components with the help of disentangled spectra. We demonstrate that the primary component of HD 66051 is a typical late-B magnetic chemically peculiar star with a non-uniform surface chemical abundance distribution. It is not an HgMn-type star as suggested by recent studies. The secondary is a metallic-line star showing neither a strong, global magnetic field nor intrinsic spectral variability. Fundamental parameters provided by our work for this interesting system open unique possibilities for probing interior structure, studying atomic diffusion, and constraining binary star evolution.

HST/COS Detection of the Spectrum of the Subdwarf Companion of KOI-81

NASA Astrophysics Data System (ADS)

Matson, Rachel A.; Gies, Douglas R.; Guo, Zhao; Quinn, Samuel N.; Buchhave, Lars A.; Latham, David W.; Howell, Steve B.; Rowe, Jason F.

2015-06-01

KOI-81 is a totally eclipsing binary discovered by the Kepler mission that consists of a rapidly rotating B-type star and a small, hot companion. The system was forged through large-scale mass transfer that stripped the mass donor of its envelope and spun up the mass gainer star. We present an analysis of UV spectra of KOI-81 that were obtained with the Cosmic Origins Spectrograph on the Hubble Space Telescope that reveal for the first time the spectral features of the faint, hot companion. We present a double-lined spectroscopic orbit for the system that yields mass estimates of 2.92 {{M}⊙ } and 0.19 {{M}⊙ } for the B-star and hot subdwarf, respectively. We used a Doppler tomography algorithm to reconstruct the UV spectra of the components, and a comparison of the reconstructed and model spectra yields effective temperatures of 12 and 19-27 kK for the B-star and hot companion, respectively. The B-star is pulsating, and we identified a number of peaks in the Fourier transform of the light curve, including one that may indicate an equatorial rotation period of 11.5 hr. The B-star has an equatorial velocity that is 74% of the critical velocity where centrifugal and gravitational accelerations balance at the equator, and we fit the transit light curve by calculating a rotationally distorted model for the photosphere of the B-star. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program #12288.

The Green Bank North Celestial Cap Pulsar Survey. III. 45 New Pulsar Timing Solutions

NASA Astrophysics Data System (ADS)

Lynch, Ryan S.; Swiggum, Joseph K.; Kondratiev, Vlad I.; Kaplan, David L.; Stovall, Kevin; Fonseca, Emmanuel; Roberts, Mallory S. E.; Levin, Lina; DeCesar, Megan E.; Cui, Bingyi; Cenko, S. Bradley; Gatkine, Pradip; Archibald, Anne M.; Banaszak, Shawn; Biwer, Christopher M.; Boyles, Jason; Chawla, Pragya; Dartez, Louis P.; Day, David; Ford, Anthony J.; Flanigan, Joseph; Hessels, Jason W. T.; Hinojosa, Jesus; Jenet, Fredrick A.; Karako-Argaman, Chen; Kaspi, Victoria M.; Leake, Sean; Lunsford, Grady; Martinez, José G.; Mata, Alberto; McLaughlin, Maura A.; Noori, Hind Al; Ransom, Scott M.; Rohr, Matthew D.; Siemens, Xavier; Spiewak, Renée; Stairs, Ingrid H.; van Leeuwen, Joeri; Walker, Arielle N.; Wells, Bradley L.

2018-06-01

We provide timing solutions for 45 radio pulsars discovered by the Robert C. Byrd Green Bank Telescope. These pulsars were found in the Green Bank North Celestial Cap pulsar survey, an all-GBT-sky survey being carried out at a frequency of 350 {MHz}. We include pulsar timing data from the Green Bank Telescope and Low Frequency Array. Our sample includes five fully recycled millisecond pulsars (MSPs, three of which are in a binary system), a new relativistic double neutron star system, an intermediate-mass binary pulsar, a mode-changing pulsar, a 138 ms pulsar with a very low magnetic field, and several nulling pulsars. We have measured two post-Keplerian parameters and thus the masses of both objects in the double neutron star system. We also report a tentative companion mass measurement via Shapiro delay in a binary MSP. Two of the MSPs can be timed with high precision and have been included in pulsar timing arrays being used to search for low-frequency gravitational waves, while a third MSP is a member of the black widow class of binaries. Proper motion is measurable in five pulsars, and we provide an estimate of their space velocity. We report on an optical counterpart to a new black widow system and provide constraints on the optical counterparts to other binary MSPs. We also present a preliminary analysis of nulling pulsars in our sample. These results demonstrate the scientific return of long timing campaigns on pulsars of all types.

WFPC2 Observations of Astrophysically Important Visual Binaries

NASA Astrophysics Data System (ADS)

Bond, Howard

1997-07-01

We recently used WFPC2 images of Procyon A and B to measure an extremely accurate separation of the bright F star and its much fainter white-dwarf companion. Combined with ground-based astrometry of the bright star, our observation significantly revises downward the derived masses, and brings Procyon A into excellent agreement with theoretical evolutionary tracks for the first time. We now propose to begin a modest but long-term program of WFPC2 measurements of astrophysically important visual binaries, working in a regime of large magnitude differences and/or faint stars where ground-based speckle interferometry cannot compete. We have selected three systems: Procyon {P=40 yr}, for which continued monitoring will even further refine the very accurate masses; Mu Cas {P=21 yr}, a famous metal-deficient G dwarf for which accurate masses will lead to the star's helium content with cosmological implications; and G 107-70, a close double white dwarf {P=18 yr} that promises to add two accurate masses to the tiny handful of white-dwarf masses that are directly known from dynamical measurements.

WFPC2 Observations of Astrophysically Important Visual Binaries - Continued

NASA Astrophysics Data System (ADS)

Bond, Howard

1999-07-01

We recently used WFPC2 images of Procyon A and B to measure an extremely accurate separation of the bright F star and its much fainter white-dwarf companion. Combined with ground-based astrometry of the bright star, our observation significantly revises downward the derived masses, and brings Procyon A into excellent agreement with theoretical evolutionary tracks for the first time. We now propose to begin a modest but long-term program of WFPC2 measurements of astrophysically important visual binaries, working in a regime of large magnitude differences and/or faint stars where ground-based speckle interferometry cannot compete. We have selected three systems: Procyon {P=40 yr}, for which continued monitoring will even further refine the very accurate masses; Mu Cas {P=21 yr}, a famous metal-deficient G dwarf for which accurate masses will lead to the star's helium content with cosmological implications; and G 107-70, a close double white dwarf {P=18 yr} that promises to add two accurate masses to the tiny handful of white-dwarf masses that are directly known from dynamical measurements.

The long-period binary central stars of the planetary nebulae NGC 1514 and LoTr 5

NASA Astrophysics Data System (ADS)

Jones, D.; Van Winckel, H.; Aller, A.; Exter, K.; De Marco, O.

2017-04-01

The importance of long-period binaries for the formation and evolution of planetary nebulae is still rather poorly understood, which in part is due to the lack of central star systems that are known to comprise such long-period binaries. Here, we report on the latest results from the on-going Mercator-HERMES survey for variability in the central stars of planetary nebulae. We present a study of the central stars of NGC 1514, BD+30°623, the spectrum of which shows features associated with a hot nebular progenitor as well as a possible A-type companion. Cross-correlation of high-resolution HERMES spectra against synthetic spectra shows the system to be a highly eccentric (e 0.5) double-lined binary with a period of 3300 days. Previous studies indicated that the cool component might be a horizontal branch star of mass 0.55 M⊙, but the observed radial velocity amplitudes rule out such a low mass. If we assume that the nebular symmetry axis and binary orbital plane are perpendicular, then the data are more consistent with a post-main-sequence star ascending towards the giant branch. We also present the continued monitoring of the central star of LoTr 5, HD 112313, which has now completed one full cycle, allowing the orbital period (P 2700 days) and eccentricity (e 0.3) to be derived. To date, the orbital periods of BD+30°623 and HD 112313 are the longest to have been measured spectroscopically in the central stars of planetary nebulae. Furthermore, these systems, along with BD+33°2642, comprise the only spectroscopic wide-binary central stars currently known. Based on observations made with the Mercator Telescope, operated on the island of La Palma by the Flemish Community, at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.The radial velocity data for both objects are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/600/L9

Contribution to the search of binaries among Am stars. II. HD 81976 and HD 98880, double-lined spectroscopic binaries

NASA Astrophysics Data System (ADS)

Carquillat, J.-M.; Ginestet, N.; Prieur, J.-L.

2001-04-01

We present the results of the observations of two Am stars of eighth magnitude, the double-lined spectroscopic binaries HD 81976 and HD 98880, carried out with the CORAVEL instrument at the Observatoire de Haute-Provence in order to determine their orbital elements. We found 1) for HD 81976: P = 5.655750 days, T = 2449785.941 HJD, omega = 341.4deg, e = 0.061, K1 = 61.68 km s-1, K2 = 63.84 km s-1, V0 = 19.85 km s-1, a1 sin i = 4.788 Gm, a2 sin i = 4.956 Gm, M1 sin 3 i = 0.5875 Msun, M2 sin 3 i = 0.5676 Msun, and 2) for HD 98880: P = 14.20783 days, T0 = 2448682.883 HJD (ascending node), e = 0., K1 = 42.47 km s-1, K2 = 49.16 km s-1, V0 = 2.40 km s-1, a1 sin i = 8.298 Gm, a2 sin i = 9.604 Gm, M1 sin 3 i = 0.6091 Msun, M2 sin 3 i = 0.5262 Msun. The first of these two systems, HD 81976, is formed by two quasi-identical stars, and the Hipparcos data (MV, B-V) are consistent with late A stars in effective temperature; it is likely that the components rotate synchronised with the orbital motion. A third body may be present in this system since (i) the orbit has a significant eccentricity despite its short period and (ii) the systemic velocity V0 shows a possible drift. For the second system, HD 98880, we give Delta mB 1.25 and we propose a simple model based upon Strömgren photometric indices and the HR theoretical diagram of Schaller et al (1992) in addition to orbital parameters and Hipparcos data: Teff = 7000 K, log 10 g = 4.0, M1 = 1.9 Msun, M2 = 1.6 Msun, log 10(age) = 9.12. The components do not rotate synchronously contrary to HD 81976. Both binaries appear to be detached systems without possibility of eclipses. Based on observations made at the Haute-Provence Observatory, France.

Conjunction of anti-parallel and component reconnection at the dayside MP: Cluster and Double Star coordinated observation on 6 April 2004

NASA Astrophysics Data System (ADS)

Wang, J.; Pu, Z. Y.; Fu, S. Y.; Wang, X. G.; Xiao, C. J.; Dunlop, M. W.; Wei, Y.; Bogdanova, Y. V.; Zong, Q. G.; Xie, L.

2011-05-01

Previous theoretical and simulation studies have suggested that the anti-parallel and component reconnection can occur simultaneously on the dayside magnetopause. Certain observations have also been reported to support global conjunct pattern of magnetic reconnection. Here, we show direct evidence for the conjunction of anti-parallel and component MR using coordinated observations of Double Star TC-1 and Cluster under the same IMF condition on 6 April, 2004. The global MR X-line configuration constructed is in good agreement with the “S-shape” model.

A CAUTIONARY TALE: MARVELS BROWN DWARF CANDIDATE REVEALS ITSELF TO BE A VERY LONG PERIOD, HIGHLY ECCENTRIC SPECTROSCOPIC STELLAR BINARY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mack, Claude E. III; Stassun, Keivan G.; De Lee, Nathan

2013-05-15

We report the discovery of a highly eccentric, double-lined spectroscopic binary star system (TYC 3010-1494-1), comprising two solar-type stars that we had initially identified as a single star with a brown dwarf companion. At the moderate resolving power of the MARVELS spectrograph and the spectrographs used for subsequent radial-velocity (RV) measurements (R {approx}< 30, 000), this particular stellar binary mimics a single-lined binary with an RV signal that would be induced by a brown dwarf companion (Msin i {approx} 50 M{sub Jup}) to a solar-type primary. At least three properties of this system allow it to masquerade as a singlemore » star with a very-low-mass companion: its large eccentricity (e {approx} 0.8), its relatively long period (P {approx} 238 days), and the approximately perpendicular orientation of the semi-major axis with respect to the line of sight ({omega} {approx} 189 Degree-Sign ). As a result of these properties, for {approx}95% of the orbit the two sets of stellar spectral lines are completely blended, and the RV measurements based on centroiding on the apparently single-lined spectrum is very well fit by an orbit solution indicative of a brown dwarf companion on a more circular orbit (e {approx} 0.3). Only during the {approx}5% of the orbit near periastron passage does the true, double-lined nature and large RV amplitude of {approx}15 km s{sup -1} reveal itself. The discovery of this binary system is an important lesson for RV surveys searching for substellar companions; at a given resolution and observing cadence, a survey will be susceptible to these kinds of astrophysical false positives for a range of orbital parameters. Finally, for surveys like MARVELS that lack the resolution for a useful line bisector analysis, it is imperative to monitor the peak of the cross-correlation function for suspicious changes in width or shape, so that such false positives can be flagged during the candidate vetting process.« less

Improving the Ability of Image Sensors to Detect Faint Stars and Moving Objects Using Image Deconvolution Techniques

PubMed Central

Fors, Octavi; Núñez, Jorge; Otazu, Xavier; Prades, Albert; Cardinal, Robert D.

2010-01-01

In this paper we show how the techniques of image deconvolution can increase the ability of image sensors as, for example, CCD imagers, to detect faint stars or faint orbital objects (small satellites and space debris). In the case of faint stars, we show that this benefit is equivalent to double the quantum efficiency of the used image sensor or to increase the effective telescope aperture by more than 30% without decreasing the astrometric precision or introducing artificial bias. In the case of orbital objects, the deconvolution technique can double the signal-to-noise ratio of the image, which helps to discover and control dangerous objects as space debris or lost satellites. The benefits obtained using CCD detectors can be extrapolated to any kind of image sensors. PMID:22294896

Improving the ability of image sensors to detect faint stars and moving objects using image deconvolution techniques.

PubMed

Fors, Octavi; Núñez, Jorge; Otazu, Xavier; Prades, Albert; Cardinal, Robert D

2010-01-01

In this paper we show how the techniques of image deconvolution can increase the ability of image sensors as, for example, CCD imagers, to detect faint stars or faint orbital objects (small satellites and space debris). In the case of faint stars, we show that this benefit is equivalent to double the quantum efficiency of the used image sensor or to increase the effective telescope aperture by more than 30% without decreasing the astrometric precision or introducing artificial bias. In the case of orbital objects, the deconvolution technique can double the signal-to-noise ratio of the image, which helps to discover and control dangerous objects as space debris or lost satellites. The benefits obtained using CCD detectors can be extrapolated to any kind of image sensors.

Classification of O Stars in the Yellow-Green: The Exciting Star VES 735

NASA Astrophysics Data System (ADS)

Kerton, C. R.; Ballantyne, D. R.; Martin, P. G.

1999-05-01

Acquiring data for spectral classification of heavily reddened stars using traditional criteria in the blue-violet region of the spectrum can be prohibitively time consuming using small to medium sized telescopes. One such star is the Vatican Observatory emission-line star VES 735, which we have found excites the H II region KR 140. In order to classify VES 735, we have constructed an atlas of stellar spectra of O stars in the yellow-green (4800-5420 Å). We calibrate spectral type versus the line ratio He I lambda4922:He II lambda5411, showing that this ratio should be useful for the classification of heavily reddened O stars associated with H II regions. Application to VES 735 shows that the spectral type is O8.5. The absolute magnitude suggests luminosity class V. Comparison of the rate of emission of ionizing photons and the bolometric luminosity of VES 735, inferred from radio and infrared measurements of the KR 140 region, to recent stellar models gives consistent evidence for a main-sequence star of mass 25 M_solar and age less than a few million years with a covering factor 0.4-0.5 by the nebular material. Spectra taken in the red (6500-6700 Å) show that the stellar Hα emission is double-peaked about the systemic velocity and slightly variable. Hβ is in absorption, so that the emission-line classification is ``(e)''. However, unlike the case of the more well-known O(e) star zeta Oph, the emission from VES 735 appears to be long-lived rather than episodic.

Astrometric Measurements and Proper Motion Analysis for WDS 11582 +0335 HJ 1204

NASA Astrophysics Data System (ADS)

Edwards, Erica; Garcia, Jose; Terronez, Cheyenne; Stuart, Melanie; Calanog, Jae; Boyce, Pat; Boyce, Grady

2018-04-01

We obtained and analyzed CCD images of the double star system WDS 11582 +0335 (HJ 1204) using the iTelescope network and a variety of specialized software. WCS coordinates were attached to each image, and the separation distance (ρ) and mean position angle (θ) were measured at ρ = 7.9" ± 0.03" and θ = 59.3° ± 0.2°. These results were compared to historical data, dating back 200 years and we find that HJ 1204 is currently exhibiting a linearly decreasing ρ and a constant θ. This suggests that HJ 1204 could be a visual double or an edge-on binary. Follow-up spectroscopic observations should resolve the two possibilities.

Parallaxes and Distance Estimates for Eleven Cataclysmic Binary Stars

NASA Astrophysics Data System (ADS)

Thorstensen, John R.; Lepine, S.; Shara, M.; Peters, C. S.

2007-12-01

We will present new distance estimates for eleven cataclysmic binary stars, based on trigonometric parallaxes measured with the 2.4m Hiltner telescope at MDM Observatory. The MDM parallaxes have typical uncertainties of 1 mas. A Bayesian formalism is used to find the most likely distance given the parallax, proper motion, and prior information. Results will be reported for the eclipsing dwarf nova HT Cas, for which our parallax favors a relatively short distance; KT Per, which proves to have a K-dwarf physical companion; the 65-minute double-degenerate system V396 Hya (CE 315); and the low accretion rate-polar MQ Dra (SDSS 1553). We gratefully acknowledge funding from the NSF through grants AST-9987334, AST-0307413, and AST-0708810.

Implications of PSR J0737-3039B for the Galactic NS-NS binary merger rate

NASA Astrophysics Data System (ADS)

Kim, Chunglee; Perera, Benetge Bhakthi Pranama; McLaughlin, Maura A.

2015-03-01

The Double Pulsar (PSR J0737-3039) is the only neutron star-neutron star (NS-NS) binary in which both NSs have been detectable as radio pulsars. The Double Pulsar has been assumed to dominate the Galactic NS-NS binary merger rate R_g among all known systems, solely based on the properties of the first-born, recycled pulsar (PSR J0737-3039A, or A) with an assumption for the beaming correction factor of 6. In this work, we carefully correct observational biases for the second-born, non-recycled pulsar (PSR J0737-0737B, or B) and estimate the contribution from the Double Pulsar on R_g using constraints available from both A and B. Observational constraints from the B pulsar favour a small beaming correction factor for A (˜2), which is consistent with a bipolar model. Considering known NS-NS binaries with the best observational constraints, including both A and B, we obtain R_g=21_{-14}^{+28} Myr-1 at 95 per cent confidence from our reference model. We expect the detection rate of gravitational waves from NS-NS inspirals for the advanced ground-based gravitational-wave detectors is to be 8^{+10}_{-5} yr-1 at 95 per cent confidence. Within several years, gravitational-wave detections relevant to NS-NS inspirals will provide us useful information to improve pulsar population models.

Swift X-Ray Upper Limits on Type Ia Supernova Environments

NASA Technical Reports Server (NTRS)

Russell, B. R.; Immler, S.

2012-01-01

We have considered 53 Type Ia supernovae (SNe Ia) observed by the Swift X-Ray Telescope. None of the SNe Ia are individually detected at any time or in stacked images. Using these data and assuming that the SNe Ia are a homogeneous class of objects, we have calculated upper limits to the X-ray luminosity (0.2-10 keV) and mass-loss rate of L(sub 0.2-10) < 1.7 X 10(exp 38) erg/s and M(dot) < l.l X 10(exp -6) solar M/ yr x (V(sub w))/(10 km/s), respectively. The results exclude massive or evolved stars as the companion objects in SN Ia progenitor systems, but allow the possibility of main sequence or small stars, along with double degenerate systems consisting of two white dwarfs, consistent with results obtained at other wavelengths (e.g., UV, radio) in other studies.

All things White Dwarf: The State of Stellar Forensics at the University of Texas and Sandia National Laboratories

NASA Astrophysics Data System (ADS)

Winget, Donald

2011-10-01

Astronomy has always been considered an observational science, in contrast with other experimental sciences like physics, chemistry, biology, and geology. This is because it has not been possible to perform experiments on the objects we observe. This situation has changed in a way that is transformational. We are now able to make macroscopic bits of star stuff in the lab: plasmas created under conditions that are the same as the plasmas in stars. Although laboratory astrophysics has long been an important part of astronomical research, what has changed is the ability to produce large enough chunks of a star that we can make measurements and perform experiments. In this way, astronomy joins her sister sciences in becoming an experimental science as well as an observational one. I will describe how this came about, the technology behind it, and the results of recent laboratory experiments. Most importantly, we will discuss how this will change our understanding of the universe and its contents. This work will shed new light on our recent discoveries involving McDonald Observatory: planets around white dwarf stars, massive carbon/oxygen variable white dwarf stars, and white dwarf-white dwarf binaries -- including one detached double eclipsing system with an orbital period of 12 minutes. We should measure the rate of change of the orbital period in this system within a year and we expect it to be the highest S/N source of gravitational radiation, easily detectable with LISA or similar approaches.

Photometry of symbiotic stars. X. EG And, Z And, BF Cyg, CH Cyg, V1329 Cyg, AG Dra, RW Hya, AX Per and IV Vir

NASA Astrophysics Data System (ADS)

Skopal, A.; Vanko, M.; Pribulla, T.; Wolf, M.; Semkov, E.; Jones, A.

2002-04-01

We present new photometric observations of EG And, Z And, BF Cyg, CH Cyg, V1329 Cyg, AG Dra, RW Hya, AX Per and IV Vir made in the standard Johnson UBVR system. The current issue summarizes observations of these objects to 2001 December. The main results can be summarized as follows: EG And: A periodic double-wave variation in all bands as a function of the orbital phase was confirmed. A maximum of the light changes was observed in U (Delta U ~ 0.5 mag). Z And: Our observations cover an active phase, which peaked around 8.4 in U at the beginning of 2000 December. Consequently, a gradual decrease in the star's brightness has been observed. BF Cyg: A periodic wave-like variation in the optical continuum reflects a quiescent phase of this star. A complex light curve (LC) profile was observed. CH Cyg: The recent episode of activity ended in Spring 2000. We determined the position of an eclipse in the outer binary at JD 2451426 +/- 3. Recent observations indicate a slow increase in the star's brightness. V1329 Cyg: Observations were made around a maximum at 2001.2. AG Dra: Our measurements from the Autumn of 2001 revealed a new eruption, which peaked at ~JD 2452217. RW Hya: The light minimum in our mean visual LC precedes the time of the spectroscopic conjunction of the giant in the binary. AX Per: A periodic wave-like variation was observed. Our recent observations revealed a secondary minimum at the orbital phase 0.5, seen best in the V and B bands. IV Vir: The LC displays a double-wave throughout the orbital cycle.

Variations in the Orbital Light Curve of the Magnetic Cataclysmic Variable Star QQ Vulpecula (Abstract)

NASA Astrophysics Data System (ADS)

Rose, S. C.

2017-06-01

(Abstract only) Magnetic cataclysmic variable stars have brightness variations that repeat with each revolution of the two stars about the center of mass of the system. However, in the case of QQ Vulpecula, this brightness variation pattern changes in the long term. This study makes use of two decades worth of data from the Roboscope Telescope as well as data from the American Association of Variable Star Observers (AAVSO) database to examine the long-term evolution of QQ Vul's phase curves. Nightly observations using the Maria Mitchell Association Vestal and Loines Observatory supplemented this analysis by clarifying short-term brightness variation. The long-term data was divided into four commonly observed behavioral types ranging from a double peaked curve of 15.5 magnitude to a 15.0 magnitude curve that had a primary minimum and a slow, linear rise in brightness in place of the secondary minimum. The nightly data kept within the confines of these categories, though the secondary minimum in the nightly data never vanished. No periodicity was found in the long-term variations. The model often invoked to explain the double peaked curve consists of single pole accretion in which a partial self-eclipse causes the secondary minimum and cyclotron beaming causes the primary minimum. However, the long-term variation may indicate a changing accretion rate, which may manifest itself in changes to the shape, size, or location of the accretion spot on the white dwarf such that it lessens or removes the secondary minimum. This project was supported by the NSF REU grant AST-1358980, the Massachusetts Space Grant, and the Nantucket Maria Mitchell Association.

Long-term Accretion Variations of the Magnetic Cataclysmic Variable Star QQ Vulpecula

NASA Astrophysics Data System (ADS)

Cooper Rose, Sanaea; Kafka, Stella; Jorgenson, Regina; Carr, Derrick; Childs, Francesca; Christenson, Holly; Karim, Md. Tanveer; Konchady, Tarini; Walker, Gary E.; Honeycutt, R. K.

2017-01-01

Magnetic cataclysmic variable stars have brightness variations that repeat with each revolution of the two stars about the center of mass of the system. However, in the case of QQ Vulpecula (QQ Vul), this brightness variation pattern changes in the long term. This study makes use of two decades worth of data from the Roboscope Telescope as well as data from the American Association of Variable Star Observers (AAVSO) database to examine the long-term evolution of QQ Vul’s phase curves. Nightly observations using the Maria Mitchell Association's Vestal and Loines Observatories supplemented this analysis by clarifying short-term brightness variation. The long-term data was divided into four commonly observed behavioral types ranging from a double peaked curve of ~15.5 magnitude to a ~15.0 magnitude curve that had a primary minimum and a slow, linear rise in brightness in place of the secondary minimum. The nightly data kept within the confines of these categories, though the secondary minimum in the nightly data never vanished. No periodicity was found in the long-term variations. The model often invoked to explain the double peaked curve consists of single pole accretion in which a partial self-eclipse causes the secondary minimum and cyclotron beaming causes the primary minimum. However, the long-term variation may indicate a changing accretion rate, which may manifest itself in changes to the shape, size, or location of the accretion spot on the white dwarf such that it lessens or removes the secondary minimum. This project was supported by the NSF REU grant AST-1358980, the Massachusetts Space Grant, and the Nantucket Maria Mitchell Association.

Orbital Solution for the Spectroscopic Binary in the GW Ori Hierarchical Triple

NASA Astrophysics Data System (ADS)

Prato, L.; Ruíz-Rodríguez, Dary; Wasserman, L. H.

2018-01-01

We present the first double-lined orbital solution for the close binary in the GW Ori triple system. Using 12 epochs of infrared spectroscopy, we detected the lines of both stars in the inner pair, previously known as single-lined only. Our preliminary infrared orbital solution has an eccentricity of e = 0.21 ± 0.10, a period of P = 241.15 ± 0.72 days, and a mass ratio of q = 0.66 ± 0.13. We find a larger semi-amplitude for the primary star, K1 = 6.57 ± 1.00 km s‑1, with an infrared-only solution compared to K1 = 4.41 ± 0.33 km s‑1 with optical data from the literature, likely the result of line blending and veiling in the optical. The component spectral types correspond to G3 and K0 stars, with v\\sin i values of 43 km s‑1 and 50 km s‑1, respectively. We obtained a flux ratio of α = 0.58 ± 0.14 in the H-band, allowing us to estimate individual masses of 3.2 and 2.7 M ⊙ for the primary and secondary, respectively, using evolutionary tracks. The tracks also yield a coeval age of 1 Myr for both components to within 1σ. GW Ori is surrounded by a circumbinary/circumtriple disk. A tertiary component has been detected in previous studies; however, we did not detect this component in our near-infrared spectra, probably the result of its relative faintness and blending in the absorption lines of these rapidly rotating stars. With these results, GW Ori joins the small number of classical T Tauri, double-lined spectroscopic binaries.

Mass-Luminosity Relations for Rapid and Slow Rotators.

NASA Astrophysics Data System (ADS)

Malkov, O. Yu.

2006-08-01

Comparing the radii of eclipsing binaries components and single stars we have found a noticeable difference between observational parameters of B0V-G0V components of eclipsing binaries and those of single stars of the corresponding spectral type. This difference was confirmed by re-analysing the results of independent investigations published in the literature. Larger radii and higher temperatures of A-F eclipsing binaries can be explained by synchronization of such stars in close systems that prevents them to rotate rapidly. So, we have found that the mass-luminosity relation based on eclipsing binary data cannot be used to derive the initial mass function of single stars. While our current knowledge of the empirical mass-luminosity relation for intermediate-mass (1.5 to 10 m[*]) stars is based exclusively on data from eclipsing binaries, knowledge of the mass-luminosity relation should come from dynamical mass determinations of visual binaries, combined with spatially resolved precise photometry. Then the initial mass function should be revised for m>1.5m[*]. Data were collected on fundamental parameters of stars with masses m > 1.5.m [*]). They are components of binaries with P > 15^d and consequently are not synchronised with the orbital periods and presumably are rapid rotators. These stars are believed to evolve similarly with single stars, so these data allow us to construct mass-luminosity and other relations that can more confidently be used for statistical and astrophysical investigations of single stars than so called standard relations, based on data on detached main-sequence double-lined short-period eclipsing binaries. Mass-luminosity, mass-temperature and mass-radius relations of single stars are presented, as well as their HR diagram.

VizieR Online Data Catalog: WDS-DM-HD-ADS Cross Index (Roman 1987)

NASA Astrophysics Data System (ADS)

Roman, N. G.

1996-11-01

A machine-readable version of the Washington Catalog of Visual Double Stars (WDS) was prepared in 1984 (Worley 1984) on the basis of a data file that has been collected and maintained for more than a century by a succession of double-star observers. Although this catalog is now being continually updated, a new copy for distribution is not expected to be available for a few years. The WDS contains DM numbers (Argelander 1859-1862, Gill and Kapteyn 1895-1900, Thome 1892-1932), but many of these are listed only in the notes, which makes it difficult to search for double-star information, except by position. Hence, a cross index that provides complete DM identifications is desirable, and it appears useful to add HD numbers (Cannon and Pickering 1918-1924, Cannon 1925- 1936) for systems in that catalog. Aitken Double Star (ADS) numbers (Aitken 1932) have been retained from the WDS, but no attempt has been made to correct these except for obvious errors. A major effort in the preparation of this cross index has been devoted to improving the DM designations. A subset of the information in the WDS has been prepared that lists the 1900 position, the double-star observer and number, the component designation, the DM number, and the ADS number. All DM numbers given only in the notes have been entered by duplicating the entry and changing the component designation appropriately. The standard rule for multiple systems in the catalog is that the DM number refers to the first component. This rule is frequently violated, however, so that it often appears that a single component has two different DM numbers. All such cases have been checked and the component designations have been corrected appropriately. It should be noted that the introduction to the 1984 machine-readable version of the WDS is in error: unless modified by the notes, DM numbers for the -52d zone refer to the CPD. In multiple systems with more than one discoverer name, numbers are sometimes given for components with one name and not for components with another, even though the magnitudes and spectral types indicate that the entries refer to the same star. In those cases in which the stars are well above the magnitude limit of the Durchmusterung (usually brighter than ninth magnitude), the DM catalog was searched for other stars that might be confused with the star identified in the WDS. If no such star was found, the DM number was entered for the second name as well. As part of the preparation for the HIPPARCOS project, a significant number of DM numbers has been found for WDS stars by position matches (Nys 1983; Bacchus 1983; Nys 1983; Bacchus and Nys 1985; Nys 1984). Many fainter components were located in the Cape Photographic Dtuchmusterung (CP) for systems north of -52d declination for which the brighter component is in the Cordoba Dllrchmusterung (CD). These DM assignments were also checked as far as possible, and most are included in the cross index. In the course of various checks, other errors were uncovered. Many, but by no means all of these, involved either supplemental stars in the northern hemisphere (Warren and Kress 1980) or catalog confusion in the southern hemisphere. To alleviate the latter problem in the future, catalog designations have been added for all DM numbers. Appendix B (on microfiche) lists all DM numbers that have been newly entered or changed from those in the WDS. Numbers given correctly in the notes to the WDS are not included. Using the improved DM listing, a correlation between a DM sort of the WDS and a DM sort of the HD was used to insert HD numbers for the appropriate systems. Stars for which WDS and HD listings differed in position by more than 3 minutes of arc in declination or 0.3 minutes of time in right ascension were investigated individually, often leading to the discovery of errors, which were corrected. The stars without DM numbers were then correlated with the HD by position, and the HD numbers were inserted if the magnitudes and spectral types agreed satisfactorily. For most of the position matches, the stars are sufficiently close to the magnitude limit of the HD, or the HD positions in crowded fields are sufficiently rough, that it is impossible to verify that the same star is referenced. For the few cases in which the identity appears highly likely, the HD number and, occasionally, the DM number from the HD have been added to the cross index. All position matches with the HD for WDS stars without DM numbers are listed in nodm.dat. For the WDS entries, table 8 gives the 1900 position, the discoverer name and number, and the magnitudes as given in the WDS; the HD data provided are the HD and DM numbers, the position, the visual magnitude, and the spectral type. If the HD does not give a visual magnitude, the photographic magnitude is given in italics. It proved impossible to resolve a few of the problems uncovered. These are listed in Table 1. In other cases, the resolution may not have been obvious, but a reasonably likely resolution was adopted. Care should be taken with multiple systems with two or more observer identifications. The WDS is not completely consistent either in assigning DM numbers to relatively bright stars or in assigning DM numbers to components in more than one subsystem. The proper DM number for the component, the DM number for the brightest component, or no DM number may be listed. An attempt has been made to clarify the assignment of the DM numbers when it appears likely that the same star is involved and no DM number is listed. Only in extreme cases have DM numbers been removed for components that are too faint to be in the DM catalogs. Although an attempt was made to assign the proper DM number to each component, there were some circumstances in which this was not done. If the magnitude of a component is ninth or fainter, if no magnitude is given in the WDS, or if there are several stars in the vicinity with approximately the same magnitude, the proper assignment is uncertain. In many systems a DM number is given for a secondary component, but it is apparent from the magnitudes that the number refers to the brightest component of the subsystem. If the primary of the subsystem is not included in the WDS for the same subsystem name, both the component designation and the DM number are retained as given in the WDS unless it is reasonably certain that the star is the same as that in another subsystem with a different DM number. Near the limit of the DM catalogs, especially, many components listed without DM numbers are probably actually DM stars. As for the DM numbers, HD numbers have been assigned to components listed in more than one subsystem when it appears likely that the same star is involved. However, particularly with HD numbers, it is often difficult to determine whether two stars with the same DM number really are the same star. names.dat lists all systems with multiple discoverer names and numbers, with all designations occurring in the system. It is sorted alphabetically and, within a discoverer designation, numerically. The systems are listed multiply so that the list may be entered with any designation. An attempt has also been made to assign HD numbers to the proper components when two HD numbers refer to the same DM number, but this is often impossible. In many cases, the assignment of two numbers in the HD is merely an indication that the spectrum is composite, and the assignment of the numbers to individual components is meaningless. Nevertheless, an assignment for at least one discoverer designation in a system is made to alert the catalog user to the existence of two numbers in the HD. In assigning HD numbers to components, the following criteria were used in descending order of priority: (1) the relative position, in the few cases in which the HD lists different positions; (2) spectral type; (3) magnitude; and (4) position angle (that is, the earlier HD number is presumed to be the western component, although in many cases it is clear that the HD could not distinguish which component is the western one). Table 2 lists multiple HD numbers for systems with the same DM number which are not given in the Cross Index. All changes in the cross index other than those in the DM number are listed in Table 3. The references for the changes listed in the column headed "S" of Appendix B and Table 3 are as follows: 1. Abt, H. A. 1978, private communication. 2. Nys, O. 1983, Bull. Inform. CDS No. 24, p. 53. 3. Bacchus, P. 1983, Bull. Inform. CDS No. 25, p. 23. 4. Nys, O. 1983, Bull. Inform. CDS No. 25, p. 27. 5. Bacchus, P. and Nys, O. 1985, Bull. Inform. CDS No. 29, p. 43. 6. Nys, O. 1984, Bull. Inform. CDS No. 26, p. 53. 7. ADC. 8. ADC, confirmed in updated WDS file (Worley, private communication). Note that many other Changes attributed to the ADC are also included in the updated WDS, but these have not been checked. For the most part, if a component had a letter designation in the WDS, this is retained to alert the cross index user to the fact that the system may have more than two components. If a DM number is listed in the notes for B in a two-component system, A has been added for the primary component to distinguish between A and B. The revision of the WDS currently in progress replaces the 1900 positions by J2000 positions. To facilitate the use of this cross index at a later date, equinox 2000 positions are also included in 2000.dat. They may not agree exactly with the new catalog positions, since proper motions are not applied; but, except for systems with very high proper motions, they should allow the user to locate the systems in the newer catalog. Five stars in the WDS have no discoverer designations. Worley has since provided "names" for these systems. These are listed in Table 4 and are included in the cross index. (6 data files).

Matter effects on LIGO/Virgo searches for gravitational waves from merging neutron stars

NASA Astrophysics Data System (ADS)

Cullen, Torrey; Harry, Ian; Read, Jocelyn; Flynn, Eric

2017-12-01

Gravitational waves from merging neutron stars are expected to be observed in the next five years. We explore the potential impact of matter effects on gravitational waves from merging double neutron-star binaries. If neutron star binaries exist with chirp masses less than roughly one solar mass and typical neutron-star radii are larger than roughly 14 km, or if neutron-star radii are larger than 15-16 km for the chirp masses of galactic neutron-star binaries, then matter will have a significant impact on the effectiveness of a point-particle-based search at Advanced LIGO design sensitivity (roughly 5% additional loss of signals). In a configuration typical of LIGO’s first observing run, extreme matter effects lead to up to 10% potential loss in the most extreme cases.

DOUBLE COMPACT OBJECTS. I. THE SIGNIFICANCE OF THE COMMON ENVELOPE ON MERGER RATES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dominik, Michal; Belczynski, Krzysztof; Bulik, Tomasz

2012-11-01

The last decade of observational and theoretical developments in stellar and binary evolution provides an opportunity to incorporate major improvements to the predictions from population synthesis models. We compute the Galactic merger rates for NS-NS, BH-NS, and BH-BH mergers with the StarTrack code. The most important revisions include updated wind mass-loss rates (allowing for stellar-mass black holes up to 80 M {sub Sun }), a realistic treatment of the common envelope phase (a process that can affect merger rates by 2-3 orders of magnitude), and a qualitatively new neutron star/black hole mass distribution (consistent with the observed {sup m}ass gap{supmore » )}. Our findings include the following. (1) The binding energy of the envelope plays a pivotal role in determining whether a binary merges within a Hubble time. (2) Our description of natal kicks from supernovae plays an important role, especially for the formation of BH-BH systems. (3) The masses of BH-BH systems can be substantially increased in the case of low metallicities or weak winds. (4) Certain combinations of parameters underpredict the Galactic NS-NS merger rate and can be ruled out. (5) Models incorporating delayed supernovae do not agree with the observed NS/BH 'mass gap', in accordance with our previous work. This is the first in a series of three papers. The second paper will study the merger rates of double compact objects as a function of redshift, star formation rate, and metallicity. In the third paper, we will present the detection rates for gravitational-wave observatories, using up-to-date signal waveforms and sensitivity curves.« less

THE AGE OF THE LOCAL INTERSTELLAR BUBBLE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abt, Helmut A., E-mail: abt@noao.edu

2011-05-15

The Local Interstellar Bubble is an irregular region from 50 to 150 pc from the Sun in which the interstellar gas density is 10{sup -2}-10{sup -3} of that outside the bubble and the interstellar temperature is 10{sup 6} K. Evidently most of the gas was swept out by one or more supernovae. I explored the stellar contents and ages of the region from visual double stars, spectroscopic doubles, single stars, open clusters, emission regions, X-ray stars, planetary nebulae, and pulsars. The bubble has three sub-regions. The region toward the galactic center has stars as early as O9.5 V and withmore » ages of 2-4 M yr. It also has a pulsar (PSRJ1856-3754) with a spin-down age of 3.76 Myr. That pulsar is likely to be the remnant of the supernova that drove away most of the gas. The central lobe has stars as early as B7 V and therefore an age of about 160 Myr or less. The Pleiades lobe has stars as early as B3 and therefore an age of about 50 Myr. There are no obvious pulsars that resulted from the supernovae that cleared out those areas. As found previously by Welsh and Lallement, the bubble has five B stars along its perimeter that show high-temperature ions of O VI and C II along their lines of sight, confirming its high interstellar temperature.« less

Quantifying the coexistence of massive black holes and dense nuclear star clusters

NASA Astrophysics Data System (ADS)

Graham, Alister W.; Spitler, Lee R.

2009-08-01

In large spheroidal stellar systems, such as elliptical galaxies, one invariably finds a 106-109Msolar supermassive black hole at their centre. In contrast, within dwarf elliptical galaxies one predominantly observes a 105-107Msolar nuclear star cluster. To date, few galaxies have been found with both types of nuclei coexisting and even less have had the masses determined for both central components. Here, we identify one dozen galaxies housing nuclear star clusters and supermassive black holes whose masses have been measured. This doubles the known number of such hermaphrodite nuclei - which are expected to be fruitful sources of gravitational radiation. Over the host spheroid (stellar) mass range 108-1011Msolar, we find that a galaxy's nucleus-to-spheroid (baryon) mass ratio is not a constant value but decreases from a few per cent to ~0.3 per cent such that log[(MBH + MNC)/Msph] = -(0.39 +/- 0.07) log[Msph/1010Msolar] - (2.18 +/- 0.07). Once dry merging commences and the nuclear star clusters disappear, this ratio is expected to become a constant value. As a byproduct of our investigation, we have found that the projected flux from resolved nuclear star clusters is well approximated with Sérsic functions having a range of indices from ~0.5 to ~3, the latter index describing the Milky Way's nuclear star cluster.

A spectroscopic search for colliding stellar winds in O-type close binary systems. I - AO Cassiopeiae

NASA Technical Reports Server (NTRS)

Gies, Douglas R.; Wiggs, Michael S.

1991-01-01

AO Cas, a short-period, double-lined spectroscopic binary, is studied as part of a search for spectroscopic evidence of colliding stellar winds in binary systems of O-type stars. High S/N ratio spectra of the H-alpha and He I 6678-A line profiles are presented, and their orbital-phase-related variations are examined in order to derive the location and motions of high-density circumstellar gas in the system. These profile variations are compared with those observed in the UV stellar wind lines in IUE archival spectra. IUE spectra are also used to derive a system mass ratio by constructing cross-correlation functions of a single-lined phase spectrum with each of the other spectra. The resulting mass ratio is consistent with the rotational line broadening of the primary star, if the primary is rotating synchronously with the binary system. The best-fit models were found to have an inclination of 61.1 deg + or - 3.0 deg and have a primary which is close to filling its critical Roche lobe.

PSR J1930-1852: a Pulsar in the Widest Known Orbit around Another Neutron Star

NASA Astrophysics Data System (ADS)

Swiggum, J. K.; Rosen, R.; McLaughlin, M. A.; Lorimer, D. R.; Heatherly, S.; Lynch, R.; Scoles, S.; Hockett, T.; Filik, E.; Marlowe, J. A.; Barlow, B. N.; Weaver, M.; Hilzendeger, M.; Ernst, S.; Crowley, R.; Stone, E.; Miller, B.; Nunez, R.; Trevino, G.; Doehler, M.; Cramer, A.; Yencsik, D.; Thorley, J.; Andrews, R.; Laws, A.; Wenger, K.; Teter, L.; Snyder, T.; Dittmann, A.; Gray, S.; Carter, M.; McGough, C.; Dydiw, S.; Pruett, C.; Fink, J.; Vanderhout, A.

2015-06-01

In the summer of 2012, during a Pulsar Search Collaboratory workshop, two high-school students discovered J1930-1852, a pulsar in a double neutron star (DNS) system. Most DNS systems are characterized by short orbital periods, rapid spin periods, and eccentric orbits. However, J1930-1852 has the longest spin period ({{P}spin} ˜ 185 ms) and orbital period ({{P}b} ˜ 45 days) yet measured among known, recycled pulsars in DNS systems, implying a shorter than average and/or inefficient recycling period before its companion went supernova. We measure the relativistic advance of periastron for J1930-1852, \\dot{ω }=0.00078 (4) deg yr-1, which implies a total mass ({{M}tot}=2.59 (4) {{M}⊙ }) consistent with other DNS systems. The 2σ constraints on {{M}tot} place limits on the pulsar and companion masses ({{m}p}\\lt 1.32 {{M}⊙ } and {{m}c}\\gt 1.30 {{M}⊙ } respectively). J1930-1852’s spin and orbital parameters challenge current DNS population models and make J1930-1852 an important system for further investigation.

Space telescope optical telescope assembly/scientific instruments. Phase B: Preliminary design and program definition study. Volume 2A(3): Astrometry

NASA Technical Reports Server (NTRS)

1976-01-01

Wide field measurements, namely, measurements of relative angular separations between stars over a relatively wide field for parallax and proper motion determinations, were made with the third fine guidance sensor. Narrow field measurements, i.e., double star measurements, are accomplished primarily with the area photometer or faint object camera at f/96. The wavelength range required can be met by the fine guidance sensor which has a spectral coverage from 3000 to 7500 A. The field of view of the fine guidance sensor also exceeds that required for the wide field astrometric instrument. Requirements require a filter wheel for the wide field astrometer, and so one was incorporated into the design of the fine guidance sensor. The filter wheel probably would contain two neutral density filters to extend the dynamic range of the sensor and three spectral filters for narrowing effective double star magnitude difference.

A circumstellar molecular gas structure associated with the massive young star Cepheus A-HW 2

NASA Technical Reports Server (NTRS)

Torrelles, Jose M.; Rodriguez, Luis F.; Canto, Jorge; Ho, Paul T. P.

1993-01-01

We report the detection via VLA-D observations of ammonia of a circumstellar high-density molecular gas structure toward the massive young star related to the object Cepheus A-HW 2, a firm candidate for the powering source of the high-velocity molecular outflow in the region. We suggest that the circumstellar molecular gas structure could be related to the circumstellar disk previously suggested from infrared, H2O, and OH maser observations. We consider as a plausible scenario that the double radio continuum source of HW 2 could represent the ionized inner part of the circumstellar disk, in the same way as proposed to explain the double radio source in L1551. The observed motions in the circumstellar molecular gas can be produced by bound motions (e.g., infall or rotation) around a central mass of about 10-20 solar masses (B0.5 V star or earlier).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Szabo, Gy. M.; Szabo, R.; Benko, J. M.

KOI-13.01, a planet-sized companion in an optical double star, was announced as one of the 1235 Kepler planet candidates in 2011 February. The transit curves show significant distortion that was stable over the {approx}130 days time span of the data. Here we investigate the phenomenon via detailed analyses of the two components of the double star and a re-reduction of the Kepler data with pixel-level photometry. Our results indicate that KOI-13 is a common proper motion binary, with two rapidly rotating components (vsin i {approx} 65-70 km s{sup -1}). We identify the host star of KOI-13.01 and conclude that themore » transit curve asymmetry is consistent with a companion orbiting a rapidly rotating, possibly elongated star on an oblique orbit. The radius of the transiter is 2.2 R{sub J} , implying an irradiated late-type dwarf, probably a hot brown dwarf rather than a planet. KOI-13 is the first example for detecting orbital obliquity for a substellar companion without measuring the Rossiter-McLaughlin effect with spectroscopy.« less

Jonckheere Double Star Photometry - Part VII: Aquarius

NASA Astrophysics Data System (ADS)

Knapp, Wilfried R. A.

2017-10-01

If any double star discoverer is in urgent need of photometry then it is Jonckheere. There are over 3000 Jonckheere objects listed in the WDS catalog and a good part of them with magnitudes obviously far too bright. This report covers the Jonckheere objects in the constellation Aquarius. One image per object was taken with V-filter to allow for visual magnitude measurement by differential pho-tometry. All objects were additionally checked for common proper motion by comparing 2MASS to GAIA DR1 positions and a rather surprisingly large part of the objects qualify indeed as potential CPM pairs. For a few objects also WDS position errors were found.

Jonckheere Double Star Photometry – Part X: Hercules

NASA Astrophysics Data System (ADS)

Knapp, Wilfried

2018-04-01

If any double star discoverer is in urgent need of photometry then it is Jonckheere. There are over 3000 Jonckheere objects listed in the WDS catalog and a good part of them with magnitudes obviously far too bright. This report covers 28 of the in total 82 Jonckheere objects in the constellation Hercules selected by a quick WDS data check for being potentially listed with questionable magnitudes. At least one image per object was taken with V-filter to allow for visual magnitude measurement by differential photometry. All objects were additionally checked for common proper motion and two qualify indeed as potential CPM pairs.

Astronomy Research Seminar

NASA Astrophysics Data System (ADS)

Johson, Jolyon; Genet, Russell; Armstrong, James; Boyce, Grady; Boyce, Pat; Brewer, Mark; Buchheim, Robert; Carro, Joseph; Estrada, Reed; Estrada, Chris; Freed, Rachel; Gillette, Sean; Harshaw, Richard; Hollis, Thomas; Kenney, John; McGaughey, Seven; McNab, Christine; Mohanan, Kakkala; Sepulveda, Babs; Wallace, Dan; Wallen, Vera

2015-05-01

Traditional science lectures and labs are often enhanced through project- and team-based learning. Some students go beyond these classroom studies by conducting research, often under the guidance of university professors. A one-semester astronomy research seminar was initiated in 2006 in collaboration with the community of professional and amateur double star astronomers. The result was dozens of jointly-authored papers published in the Journal of Double Star Observations and the Annual Proceedings of the Society of Astronomical Sciences. This seminar, and its affiliated community, launched a series of conferences and books, providing students with additional forums to share their double star research. The original seminar, and its derivatives, enhanced educational careers through college admissions and scholarships. To expand the seminar's reach, it was restructured from a few teams at one school, to many teams, each from a different school. A volunteer from each school became an assistant instructor. Most of them were seminar veterans, experienced astronomers, or science teachers. The assistant instructors, in turn, recruited enthusiastic students for their teams. To avoid student and instructor overload, the seminar focused on its three deliverables: a formal proposal, published paper, and public PowerPoint presentation. Future seminars may offer other astronomical research options such as exoplanet transit or eclipsing binary photometry.

VizieR Online Data Catalog: Observations of binary stars at the WIYN telescope (Horch+, 2017)

NASA Astrophysics Data System (ADS)

Horch, E. P.; Casetti-Dinescu, D. I.; Camarata, M. A.; Bidarian, A.; van Altena, W. F.; Sherry, W. H.; Everett, M. E.; Howell, S. B.; Ciardi, D. R.; Henry, T. J.; Nusdeo, D. A.; Winters, J. G.

2018-05-01

The observations were carried out over six runs at the WIYN telescope, specifically, 2010 September 17-21, 2010 October 23-26, 2011 June 11-16, 2011 September 7-11, 2011 December 10-11, and 2012 February 4-8. In each case, an observing list was constructed primarily from HDSs and Hipparcos suspected doubles (ESA 1997ESASP1200.....E), double-lined spectroscopic binary stars identified in the Geneva-Copenhagen spectroscopic survey (Nordstroem et al. 2004, Cat. V/117), and stars we have previously found to be double in our own program and reported in earlier papers in this series. For all observations here, the Differential Speckle Survey Instrument (DSSI) was used (Horch et al. 2009AJ....137.5057H). The instrument can mount to either of the Nasmyth ports of the WIYN telescope and takes speckle observations in two filters simultaneously. The DSSI observing program at WIYN began in 2008, and the instrument was upgraded to use two electron-multiplying CCD cameras in 2010 January. More recently, DSSI have also been used at Lowell Observatory's Discovery Channel Telescope (DCT), and at both the Gemini north and Gemini south telescopes. (3 data files).

BinCat: a Catalog of Nearby Binary Stars with Tools for Calculating Light-Leakage for Direct Imaging Missions

NASA Astrophysics Data System (ADS)

Holte, Elias Peter; Sirbu, Dan; Belikov, Ruslan

2018-01-01

Binary stars have been largely left out of direct imaging surveys for exoplanets, specifically for earth-sized planets in their star's habitable zone. Utilizing new direct imaging techniques brings us closer to being able to detect earth-like exoplanets around binary stars. In preparation for the upcoming WFIRST mission and other direct imaging-capable missions (HabEx, LUVIOR) it is important to understand the expected science yield resulting from the implementation of these imaging techniques. BinCat is a catalog of binary systems within 30 parsecs to be used as a target list for future direct imaging missions. There is a non-static component along with BinCat that allows researchers to predict the expected light-leakage between a binary component and its off-axis companion (a value critical to the aforementioned techniques) at any epoch. This is accomplished by using orbital elements from the Sixth Orbital Catalog to model the orbits of the binaries. The software was validated against the historical data used to generate the orbital parameters. When orbital information is unknown or the binaries are purely optical the proper motion of the pair taken from the Washington Double Star catalog is integrated in time to estimate expected light-leakage.

Sizing the star cluster population of the Large Magellanic Cloud

NASA Astrophysics Data System (ADS)

Piatti, Andrés E.

2018-04-01

The number of star clusters that populate the Large Magellanic Cloud (LMC) at deprojected distances <4 deg has been recently found to be nearly double the known size of the system. Because of the unprecedented consequences of this outcome in our knowledge of the LMC cluster formation and dissolution histories, we closely revisited such a compilation of objects and found that only ˜35 per cent of the previously known catalogued clusters have been included. The remaining entries are likely related to stellar overdensities of the LMC composite star field, because there is a remarkable enhancement of objects with assigned ages older than log(t yr-1) ˜ 9.4, which contrasts with the existence of the LMC cluster age gap; the assumption of a cluster formation rate similar to that of the LMC star field does not help to conciliate so large amount of clusters either; and nearly 50 per cent of them come from cluster search procedures known to produce more than 90 per cent of false detections. The lack of further analyses to confirm the physical reality as genuine star clusters of the identified overdensities also glooms those results. We support that the actual size of the LMC main body cluster population is close to that previously known.

Water transport to circumprimary habitable zones from icy planetesimal disks in binary star systems

NASA Astrophysics Data System (ADS)

Bancelin, D.; Pilat-Lohinger, E.; Maindl, T. I.; Bazsó, Á.

2017-03-01

So far, more than 130 extrasolar planets have been found in multiple stellar systems. Dynamical simulations show that the outcome of the planetary formation process can lead to different planetary architectures (i.e. location, size, mass, and water content) when the star system is single or double. In the late phase of planetary formation, when embryo-sized objects dominate the inner region of the system, asteroids are also present and can provide additional material for objects inside the habitable zone (HZ). In this study, we make a comparison of several binary star systems and aim to show how efficient they are at moving icy asteroids from beyond the snow line into orbits crossing the HZ. We also analyze the influence of secular and mean motion resonances on the water transport towards the HZ. Our study shows that small bodies also participate in bearing a non-negligible amount of water to the HZ. The proximity of a companion moving on an eccentric orbit increases the flux of asteroids to the HZ, which could result in a more efficient water transport on a short timescale, causing a heavy bombardment. In contrast to asteroids moving under the gravitational perturbations of one G-type star and a gas giant, we show that the presence of a companion star not only favors a faster depletion of our disk of planetesimals, but can also bring 4-5 times more water into the whole HZ. However, due to the secular resonance located either inside the HZ or inside the asteroid belt, impacts between icy planetesimals from the disk and big objects in the HZ can occur at high impact speed. Therefore, real collision modeling using a GPU 3D-SPH code show that in reality, the water content of the projectile is greatly reduced and therefore, also the water transported to planets or embryos initially inside the HZ.

An Anzatz about Gravity, Cosmology, and the Pioneer Anomaly

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murad, Paul

2010-01-28

The Pulsar 1913+16 binary system may represent a 'young' binary system where previously it is claimed that the dynamics are due to either a third body or a gravitational vortex. Usually a binary system's trajectory could reside in a single ellipse or circular orbit; the double ellipse implies that the 1913+16 system may be starting to degenerate into a single elliptical trajectory. This could be validated only after a considerably long time period. In a majority of binary star systems, the weights of both stars are claimed by analysis to be the same. It may be feasible that the trajectorymore » of the primary spinning star could demonstrate repulsive gravitational effects where the neutron star's high spin rate induces a repulsive gravitational source term that compensates for inertia. If true, then it provides evidence that angular momentum may be translated into linear momentum as a repulsive source that has propulsion implications. This also suggests mass differences may dictate the neutron star's spin rate as an artifact of a natural gravitational process. Moreover, the reduced matter required by the 'dark' mass hypothesis may not exist but these effects could be due to repulsive gravity residing in rotating celestial bodies.The Pioneer anomaly observed on five different deep-space spacecraft, is the appearance of a constant gravitational force directed toward the sun. Pioneer spacecraft data reveals that a vortex-like magnetic field exists emanating from the sun. The spiral arms of the Sun's magnetic vortex field may be causal to this constant acceleration. This may profoundly provide a possible experimental verification on a cosmic scale of Gertsenshtein's principle relating gravity to electromagnetism. Furthermore, the anomalous acceleration may disappear once the spacecraft passes out into a magnetic spiral furrow, which is something that needs to be observed in the future. Other effects offer an explanation from space-time geometry to the Yarkovsky thermal effects are discussed.« less

Angular momentum exchange in white dwarf binaries accreting through direct impact

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sepinsky, J. F.; Kalogera, V., E-mail: jeremy.sepinsky@scranton.edu, E-mail: vicky@northwestern.edu

We examine the exchange of angular momentum between the component spins and the orbit in semi-detached double white dwarf binaries undergoing mass transfer through direct impact of the transfer stream. We approximate the stream as a series of discrete massive particles ejected in the ballistic limit at the inner Lagrangian point of the donor toward the accretor. This work improves upon similar earlier studies in a number of ways. First, we self-consistently calculate the total angular momentum of the orbit at all times. This includes changes in the orbital angular momentum during the ballistic trajectory of the ejected mass, asmore » well as changes during the ejection/accretion due to the radial component of the particle's velocity. Second, we calculate the particle's ballistic trajectory for each system, which allows us to determine the precise position and velocity of the particle upon accretion. We can then include specific information about the radius of the accretor as well as the angle of impact. Finally, we ensure that the total angular momentum is conserved, which requires the donor star spin to vary self-consistently. With these improvements, we calculate the angular momentum change of the orbit and each binary component across the entire parameter space of direct impact double white dwarf binary systems. We find a significant decrease in the amount of angular momentum removed from the orbit during mass transfer, as well as cases where this process increases the angular momentum of the orbit at the expense of the spin angular momentum of the donor. We conclude that, unlike earlier claims in the literature, mass transfer through direct impact need not destabilize the binary and that the quantity and sign of the orbital angular momentum transfer depends on the binary properties, particularly the masses of the double white dwarf binary component stars. This stabilization may significantly impact the population synthesis calculations of the expected numbers of events/systems for which double white dwarfs may be a progenitor, e.g., Type Ia supernovae, Type.Ia supernovae, and AM CVn.« less

The Evolutionary Connection Bewtween z~2-3 Submillimeter Galaxies and AGN as Probed by Molecular Gas Excitation

NASA Astrophysics Data System (ADS)

Sharon, Chelsea E.; Riechers, Dominik A.; Carilli, Chris Luke; Hodge, Jacqueline; Walter, Fabian

2016-01-01

Theoretical work has suggested that active galactic nuclei (AGN) play an important role in quenching star formation in massive galaxies. Direct evidence for AGN affecting the molecular ISM has so far been limited to detections of molecular outflows in low-redshift systems and extreme excitation regions which represent a tiny fraction of the total gas. Indirect evidence for AGN's impact on their host galaxies' cold gas phase may be provided by measurements of the gas excitation and dynamics. At z~2-3, the peak epoch of star formation and AGN activity, previous observations of the CO(1-0) line revealed that submillimeter galaxies (SMGs) have multi-phase molecular gas, including substantial reservoirs of cold-phase gas. However, the entirety of the molecular gas in AGN-host galaxies appears highly excited, potentially supporting an evolutionary connection between these two populations. I will present a new VLA sample that nearly doubles the number of CO(1-0) detections in z~2-3 SMGs and AGN-host galaxies that allows us to better compare the cold gas properties of these systems and further investigate evidence for the effects of AGN on the star-forming molecular gas.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan, Kuo-Chuan; Ricker, Paul M.; Taam, Ronald E., E-mail: kpan2@illinois.edu, E-mail: pmricker@illinois.edu, E-mail: r-taam@northwestern.edu

The progenitor systems of Type Ia supernovae (SNe Ia) are still under debate. Based on recent hydrodynamics simulations, non-degenerate companions in the single-degenerate scenario (SDS) should survive the supernova (SN) impact. One way to distinguish between the SDS and the double-degenerate scenario is to search for the post-impact remnant stars (PIRSs) in SN Ia remnants. Using a technique that combines multi-dimensional hydrodynamics simulations with one-dimensional stellar evolution simulations, we have examined the post-impact evolution of helium-rich binary companions in the SDS. It is found that these helium-rich PIRSs (He PIRSs) dramatically expand and evolve to a luminous phase (L {approx}more » 10{sup 4} L{sub Sun }) about 10 yr after an SN explosion. Subsequently, they contract and evolve to become hot blue-subdwarf-like (sdO-like) stars by releasing gravitational energy, persisting as sdO-like stars for several million years before evolving to the helium red-giant phase. We therefore predict that a luminous OB-like star should be detectable within {approx}30 yr after the SN explosion. Thereafter, it will shrink and become an sdO-like star in the central regions of SN Ia remnants within star-forming regions for SN Ia progenitors evolved via the helium-star channel in the SDS. These He PIRSs are predicted to be rapidly rotating (v{sub rot} {approx}> 50 km s{sup -1}) and to have high spatial velocities (v{sub linear} {approx}> 500 km s{sup -1}). Furthermore, if SN remnants have diffused away and are not recognizable at a later stage, He PIRSs could be an additional source of single sdO stars and/or hypervelocity stars.« less

The Solar Neighborhood. XXXIX. Parallax Results from the CTIOPI and NOFS Programs: 50 New Members of the 25 parsec White Dwarf Sample

NASA Astrophysics Data System (ADS)

Subasavage, John P.; Jao, Wei-Chun; Henry, Todd J.; Harris, Hugh C.; Dahn, Conard C.; Bergeron, P.; Dufour, P.; Dunlap, Bart H.; Barlow, Brad N.; Ianna, Philip A.; Lépine, Sébastien; Margheim, Steven J.

2017-07-01

We present 114 trigonometric parallaxes for 107 nearby white dwarf (WD) systems from both the Cerro Tololo Inter-American Observatory Parallax Investigation (CTIOPI) and the U. S. Naval Observatory Flagstaff Station (NOFS) parallax programs. Of these, 76 parallaxes for 69 systems were measured by the CTIOPI program and 38 parallaxes for as many systems were measured by the NOFS program. A total of 50 systems are confirmed to be within the 25-pc horizon of interest. Coupled with a spectroscopic confirmation of a common proper-motion companion to a Hipparcos star within 25 pc as well as confirmation parallax determinations for two WD systems included in the recently released Tycho Gaia Astrometric Solution catalog, we add 53 new systems to the 25-pc WD sample—a 42% increase. Our sample presented here includes four strong candidate halo systems, a new metal-rich DAZ WD, a confirmation of a recently discovered nearby short-period (P = 2.85 hr) double degenerate, a WD with a new astrometric perturbation (long period, unconstrained with our data), and a new triple system where the WD companion main-sequence star has an astrometric perturbation (P ˜ 1.6 year).

Potential of the McMath-Pierce 1.6-Meter Solar Telescope for Speckle Interferometry

NASA Astrophysics Data System (ADS)

Harshaw, Richard; Jones, Gregory; Wiley, Edward; Boyce, Patrick; Branston, Detrick; Rowe, David; Genet, Russell

2015-09-01

We explored the aiming and tracking accuracy of the McMath-Pierce 1.6 m solar telescope at Kitt Peak National Observatory as part of an investigation of using this telescope for speckle interferometry of close visual double stars. Several slews of various lengths looked for hysteresis in the positioning system (we found none of significance) and concluded that the 1.6 m telescope would make a useful telescope for speckle interferometry.

LUT Reveals a New Mass-transferring Semi-detached Binary

NASA Astrophysics Data System (ADS)

Qian, S.-B.; Zhou, X.; Zhu, L.-Y.; Zejda, M.; Soonthornthum, B.; Zhao, E.-G.; Zhang, J.; Zhang, B.; Liao, W.-P.

2015-12-01

GQ Dra is a short-period eclipsing binary in a double stellar system that was discovered by Hipparcos. Complete light curves in the UV band were obtained with the Lunar-based Ultraviolet Telescope in 2014 November and December. Photometric solutions are determined using the W-D (Wilson and Devinney) method. It is discovered that GQ Dra is a classical Algol-type semi-detached binary where the secondary component is filling the critical Roche lobe. An analysis of all available times of minimum light suggests that the orbital period is increasing continuously at a rate of \\dot{P}=+3.48(+/- 0.23)× {10}-7 days yr-1. This could be explained by mass transfer from the secondary to the primary, which is in agreement with the semi-detached configuration with a lobe-filling secondary. By assuming a conservation of mass and angular momentum, the mass transfer rate is estimated as \\dot{m}=9.57(+/- 0.63)× {10}-8 {M}⊙ {{yr}}-1. All of these results reveal that GQ Dra is a mass-transferring semi-detached binary in a double system that was formed from an initially detached binary star. After the massive primary evolves to fill the critical Roche lobe, the mass transfer will be reversed and the binary will evolve into a contact configuration with two sub-giant or giant component stars.

Detection of accreting gas toward HD 45677: A newly recognized, Herbig Be proto-planetary system

NASA Technical Reports Server (NTRS)

Grady, C. A.; Bjorkman, K. S.; Shepherd, D.; Schulte-Ladbeck, R. E.; Perez, M. R.; Dewinter, D.; The, P. S.

1993-01-01

We report detection of high velocity, accreting gas toward the Be star with IR excess and bipolar nebula, HD 45677. High velocity (+200 to +400 km/s), variable column density gas is visible in all IUE spectra from 1979-1992 in transitions of Si II, C II, Al III, Fe III, Si IV, and C IV. Low-velocity absorption profiles from low oscillator-strength transitions of Si II, Fe II, and Zn II exhibit double-peaked absorption profiles similar to those previously reported in optical spectra of FU Orionis objects. The UV absorption data, together with previously reported analyses of the IR excess and polarization of this object, suggest that HD 45677 is a massive, Herbig Be star with an actively accreting circumstellar, proto-planetary disk.

Physical Orbit for Lam Vir and Testing of Stellar Evolution Models

NASA Astrophysics Data System (ADS)

Zhao, M.; Monnier, J. D.; Torres, G.; Pedretti, E.; Millan-Gabet, R.; Berger, J.-P.; Traub, W. A.; Schloerb, F. P.

2005-12-01

Lambda Virginis is a well-known double-lined spectroscopic Am binary with the interesting property that both stars are very similar in abundance but one is sharp-lined and the other is broad-lined. The differing rotation rates and the unusual metallic-lined nature of this system presents a unique opportunity to test stellar evolution models. In this poster, we present high resolution observations of Lam Vir, taken with the Infrared-Optical Telescopes Array (IOTA) between 2003 and 2005. By combining our interferometric data with double-lined radial velocity data, we determined for the first time the physical orbit of Lam Vir, as well as the orbital parallax of the system. In addition, the masses of the two components are determined with 1% and 1.5% errors respectively. Our preliminary result from comparison with stellar evolution models suggests a discrepancy between Lam Vir and standard models.

Death and Rebirth in "Star Trek II: The Wrath of Khan."

ERIC Educational Resources Information Center

Roth, Lane

"Star Trek II" is a treatment of the penultimate stages of the monomyth in which the hero descends into the underworld and is reborn. This psychological sense of rebirth is evoked in modern audiences by the film. In particular, the doppelganger (psychic double) motif, so often associated in film, literature, and myth with the…

Frequency Analysis of the RRc Variables of the MACHO Database for the LMC

NASA Astrophysics Data System (ADS)

Kovács, G.; Alcock, C.; Allsman, R.; Alves, D.; Axelrod, T.; Becker, A.; Bennett, D.; Clement, C.; Cook, K. H.; Drake, A.; Freeman, K.; Geha, M.; Griest, K.; Kurtz, D. W.; Lehner, M.; Marshall, S.; Minniti, D.; Nelson, C.; Peterson, B.; Popowski, P.; Pratt, M.; Quinn, P.; Rodgers, A.; Rowe, J.; Stubbs, C.; Sutherland, W.; Tomaney, A.; Vandehei, T.; Welch, D. L.; MACHO Collaboration

We present the first massive frequency analysis of the 1200 first overtone RR Lyrae stars in the Large Magellanic Cloud observed in the first 4.3 yr of the MACHO project. Besides the many new double-mode variables, we also discovered stars with closely spaced frequencies. These variables are most probably nonradial pulsators.

Cataloging the Praesepe Cluster: Identifying Interlopers and Binary Systems

NASA Astrophysics Data System (ADS)

Lucey, Madeline R.; Gosnell, Natalie M.; Mann, Andrew; Douglas, Stephanie

2018-01-01

We present radial velocity measurements from an ongoing survey of the Praesepe open cluster using the WIYN 3.5m Telescope. Our target stars include 229 early-K to mid-M dwarfs with proper motion memberships that have been observed by the repurposed Kepler mission, K2. With this survey, we will provide a well-constrained membership list of the cluster. By removing interloping stars and determining the cluster binary frequency we can avoid systematic errors in our analysis of the K2 findings and more accurately determine exoplanet properties in the Praesepe cluster. Obtaining accurate exoplanet parameters in open clusters allows us to study the temporal dimension of exoplanet parameter space. We find Praesepe to have a mean radial velocity of 34.09 km/s and a velocity dispersion of 1.13 km/s, which is consistent with previous studies. We derive radial velocity membership probabilities for stars with ≥3 radial velocity measurements and compare against published membership probabilities. We also identify radial velocity variables and potential double-lined spectroscopic binaries. We plan to obtain more observations to determine the radial velocity membership of all the stars in our sample, as well as follow up on radial velocity variables to determine binary orbital solutions.

A strange dwarf scenario for the formation of the peculiar double white dwarf binary SDSS J125733.63+542850.5

NASA Astrophysics Data System (ADS)

Jiang, Long; Chen, Wen-Cong; Li, Xiang-Dong

2018-05-01

The Hubble Space Telescope observation of the double white dwarf (WD) binary SDSS J125733.63+542850.5 reveals that the massive WD has a surface gravity log g1 ˜ 8.7 (which implies a mass of M1 ˜ 1.06 M⊙) and an effective temperature T1 ˜ 13 000 K, while the effective temperature of the low-mass WD (M2 < 0.24 M⊙) is T2 ˜ 6400K. Therefore, the massive and the low-mass WDs have a cooling age τ1 ˜ 1 Gyr and τ2 ≥ 5 Gyr, respectively. This is in contradiction with traditional binary evolution theory. In this paper, we propose a strange dwarf (SD) scenario to explain the formation of this double WD binary. We assume that the massive WD is a SD originating from a phase transition (PT) in a ˜1.1 M⊙ WD, which has experienced accretion and spin-down processes. Its high effective temperature could arise from the heating process during the PT. Our simulations suggest that the progenitor of SDSS J125733.63+542850.5 can be a binary system consisting of a 0.65 M⊙ WD and a 1.5 M⊙ main-sequence star in a 1.492 d orbit. Especially, the secondary star (i.e. the progenitor of the low-mass WD) is likely to have an ultra-low metallicity of Z = 0.0001.

An Infrared Census of DUST in Nearby Galaxies with Spitzer (DUSTiNGS). IV. Discovery of High-redshift AGB Analogs

NASA Astrophysics Data System (ADS)

Boyer, M. L.; McQuinn, K. B. W.; Groenewegen, M. A. T.; Zijlstra, A. A.; Whitelock, P. A.; van Loon, J. Th.; Sonneborn, G.; Sloan, G. C.; Skillman, E. D.; Meixner, M.; McDonald, I.; Jones, O. C.; Javadi, A.; Gehrz, R. D.; Britavskiy, N.; Bonanos, A. Z.

2017-12-01

The survey for DUST in Nearby Galaxies with Spitzer (DUSTiNGS) identified several candidate Asymptotic Giant Branch (AGB) stars in nearby dwarf galaxies and showed that dust can form even in very metal-poor systems ({\\boldsymbol{Z}}∼ 0.008 {Z}ȯ ). Here, we present a follow-up survey with WFC3/IR on the Hubble Space Telescope (HST), using filters that are capable of distinguishing carbon-rich (C-type) stars from oxygen-rich (M-type) stars: F127M, F139M, and F153M. We include six star-forming DUSTiNGS galaxies (NGC 147, IC 10, Pegasus dIrr, Sextans B, Sextans A, and Sag DIG), all more metal-poor than the Magellanic Clouds and spanning 1 dex in metallicity. We double the number of dusty AGB stars known in these galaxies and find that most are carbon rich. We also find 26 dusty M-type stars, mostly in IC 10. Given the large dust excess and tight spatial distribution of these M-type stars, they are most likely on the upper end of the AGB mass range (stars undergoing Hot Bottom Burning). Theoretical models do not predict significant dust production in metal-poor M-type stars, but we see evidence for dust excess around M-type stars even in the most metal-poor galaxies in our sample (12+{log}({{O}}/{{H}})=7.26{--}7.50). The low metallicities and inferred high stellar masses (up to ∼10 {M}ȯ ) suggest that AGB stars can produce dust very early in the evolution of galaxies (∼30 Myr after they form), and may contribute significantly to the dust reservoirs seen in high-redshift galaxies. Based on observations made with the NASA/ESA Hubble Space Telescope at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program GO-14073.

A spectroscopic survey of the youngest field stars in the solar neighborhood . II. The optically faint sample

NASA Astrophysics Data System (ADS)

Frasca, A.; Guillout, P.; Klutsch, A.; Ferrero, R. Freire; Marilli, E.; Biazzo, K.; Gandolfi, D.; Montes, D.

2018-05-01

Context. Star formation in the solar neighborhood is mainly traced by young stars in open clusters, associations, and in the field, which can be identified, for example, by their X-ray emission. The determination of stellar parameters for the optical counterparts of X-ray sources is crucial for a full characterization of these stars. Aims: This work extends the spectroscopic study of the RasTyc sample, obtained by the cross-correlation of the Tycho and ROSAT All-Sky Survey catalogs, to stars fainter than V = 9.5 mag and aims to identify sparse populations of young stars in the solar neighborhood. Methods: We acquired 625 high-resolution spectra for 443 presumably young stars with four different instruments in the northern hemisphere. The radial and rotational velocity (vsini) of our targets were measured by means of the cross-correlation technique, which is also helpful to discover single-lined (SB1), double-lined spectroscopic binaries (SB2), and multiple systems. We used the code ROTFIT to perform an MK spectral classification and to determine the atmospheric parameters (Teff, logg, [Fe/H]) and vsini of the single stars and SB1 systems. For these objects, we used the spectral subtraction of slowly rotating templates to measure the equivalent widths of the Hα and Li I 6708 Å lines, which enabled us to derive their chromospheric activity level and lithium abundance. We made use of Gaia DR1 parallaxes and proper motions to locate the targets in the Hertzsprung-Russell (HR) diagram and to compute the space velocity components of the youngest objects. Results: We find a remarkable percentage (at least 35%) of binaries and multiple systems. On the basis of the lithium abundance, the sample of single stars and SB1 systems appears to be mostly ( 60%) composed of stars younger than the members of the UMa cluster. The remaining sources are in the age range between the UMa and Hyades clusters ( 20%) or older ( 20%). In total, we identify 42 very young (PMS-like) stars, which lie above or very close to the Pleiades upper envelope of the lithium abundance. A significant percentage ( 12%) of evolved stars (giants and subgiants) is also present in our sample. Some of these stars ( 36%) are also lithium rich (A(Li) > 1.4). Based on observations collected at the Italian Telescopio Nazionale Galileo (TNG) operated by the Fundacion Galileo Galilei - INAF (Canary Islands, Spain), at the Observatoire de Haute Provence (OHP, France), and the Osservatorio Astrofisico di Catania (OAC, Italy)Tables A.1-A.4 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/12/A96Rubens Freire Ferrero passed away on September 10, 2015.

Effects of stellar evolution and ionizing radiation on the environments of massive stars

NASA Astrophysics Data System (ADS)

Mackey, J.; Langer, N.; Mohamed, S.; Gvaramadze, V. V.; Neilson, H. R.; Meyer, D. M.-A.

2014-09-01

We discuss two important effects for the astrospheres of runaway stars: the propagation of ionizing photons far beyond the astropause, and the rapid evolution of massive stars (and their winds) near the end of their lives. Hot stars emit ionizing photons with associated photoheating that has a significant dynamical effect on their surroundings. 3-D simulations show that H ii regions around runaway O stars drive expanding conical shells and leave underdense wakes in the medium they pass through. For late O stars this feedback to the interstellar medium is more important than that from stellar winds. Late in life, O stars evolve to cool red supergiants more rapidly than their environment can react, producing transient circumstellar structures such as double bow shocks. This provides an explanation for the bow shock and linear bar-shaped structure observed around Betelgeuse.

RR Lyrae Stars in M4

NASA Astrophysics Data System (ADS)

Kuehn, Charles A.; Moskalik, Pawel; Drury, Jason A.

2017-10-01

Observations by Kepler/K2 have revolutionized the study of RR Lyrae stars by allowing the detection of new phenomna, such as low amplitude additional modes and period doubling, which had not previously been seen from the ground. During campaign 2, K2 observed the globular cluster M4, providiing the first opportunity to study a sizeable group of RR Lyrae stars that belong to a single population; the other RR Lyrae stars that have been observed from space are field stars in the galactic halo and thus belong to an assortment of populations. In this poster we present the results of our study of the RR Lyrae variables in M4 from K2 photometry. We have identified additional, low amplitude pulsation modes in both observed RRc stars. In 3 RRab stars we have found the Blazhko effect with periods of 16.6d, 22.4d, and 44.5d.

Studying RR Lyrae Stars in M4 with K2

NASA Astrophysics Data System (ADS)

Kuehn, Charles A.; Drury, Jason; Moskalik, Pawel

2017-01-01

Observations by Kepler/K2 have revolutionized the study of RR Lyrae stars by allowing the detection of new phenomena, such as low amplitude additional modes and period doubling, which had not previously been seen from the ground. During its campaign 2, K2 observed the globular cluster M4, providing the first opportunity to study a sizeable group of RR Lyrae stars that belong to a single population; the other RR Lyrae stars that have been observed from space are field stars in the galactic halo and thus belong to an assortment of populations. We present the results of our study of the RR Lyrae variables in M4 from K2 photometry. We have identified additional, low amplitude pulsation modes in the two observed RRc stars. In three RRab stars we have found the Blazhko effect with periods of 16.6 days, 22.4 days, and 44.5 days.

Design and construction of a multiple beam laser projector and dynamically refocused wavefront sensor

NASA Astrophysics Data System (ADS)

Stalcup, Thomas Eugene, Jr.

Adaptive optics using natural guide stars can produce images of amazing quality, but is limited to a small fraction of the sky due to the need for a relatively bright guidestar. Adaptive optics systems using a laser generated artificial reference can be used over a majority of the sky, but these systems have some attendant problems. These problems can be reduced by increasing the altitude of the laser return, and indeed a simple, single laser source focused at an altitude of 95 km on a layer of atmospheric sodium performs well for the current generation of 8--10 m telescopes. For future giant telescopes in the 20--30 m class, however, the errors due to incorrect atmospheric sampling and spot elongation will prohibit such a simple system from working. The system presented in this dissertation provides a solution to these problems. Not only does it provide the 6.5m MMT with a relatively inexpensive laser guide star system with unique capabilities, it allows research into solving many of the problems faced by laser guide star systems on future giant telescopes. The MMT laser guidestar system projects a constellation of five doubled Nd:YAG laser beams focused at a mean height of 25 km, with a dynamic refocus system that corrects for spot elongation and allows integrating the return from a 10 km long range gate. It has produced seeing limited spot sizes in ˜1 arcsecond seeing conditions, and has enabled the first on-sky results of Ground Layer Adaptive Optics (GLAO).

VizieR Online Data Catalog: Spectral types of stars in Coalsack region (Vanas 1939)

NASA Astrophysics Data System (ADS)

Vanas, E.

2010-11-01

This table shows coordinates and identifications for 1930 stars in northern Cygnus ('Northern Coalsack' region) classified by Erik Vanas in an early spectral survey. In the source paper, the stars were identified by BD number (part I of the catalogue) and by approximate coordinates for fainter non-BD stars (part II of the catalogue). The spectral types were determined from scans of objective-prism plates (~260Å/mm). Accurate coordinates of the BD stars were derived mainly from the Tycho-2 catalogue. The non-BD stars had to be identified one-by-one from DSS images via SkyView, usually unambiguous, and coordinates found in VizieR. For the non-BD stars, the acronym [V39] was used. For pairs or crowded stars, 2MASS positions are sometimes used. Where the type applies to a near-equal double star, the coordinates are for the mid-point between the two stars (rounded to 1" precision), and the magnitude is for the combined light. The original Vanas photo-blue magnitudes are somewhat uncertain, probably including a color term. Instead standard V magnitudes from Tycho-2 or from the TASS MkIV survey (Cat. II/271) are supplied. The Vanas spectral types are formally on the 'Uppsala' system, which includes the strength of the CN band to distinguish dwarfs and giants among types later than G5. These are shown in modern MK notation. The scheme also includes a pseudo-luminosity class for hot stars based largely on the width of the Balmer lines. Since the He lines were not involved in the classification, the system loses resolution (or 'granularity') for types earlier than A0. There is also the danger at this dispersion of mistaking a late-B supergiant for an early-B dwarf. From consideration of his descriptions of the spectra, and also comparison with types from modern sources for the same stars, these 'Greek-lettered' types were transformed in modern notation as: * types 'A0μ' given as A0V * types 'A0σ' and 'A0σ+' given as B8 * types 'B{tau}-' given as B, and are mainly B3 to B7 * types 'B{tau}' given as OB The classifications otherwise nominally match the HD scale. Further comparison with MK types suggests they are indeed very good, on a par with similar post-War surveys, and rather more accurate than HD types for the same stars. Vanas recognized several new metallic-line stars in this survey. (1 data file).

The Galactic O-Star Spectroscopic Survey. I. Classification System and Bright Northern Stars in the Blue-violet at R ~ 2500

NASA Astrophysics Data System (ADS)

Sota, A.; Maíz Apellániz, J.; Walborn, N. R.; Alfaro, E. J.; Barbá, R. H.; Morrell, N. I.; Gamen, R. C.; Arias, J. I.

2011-04-01

We present the first installment of a massive spectroscopic survey of Galactic O stars, based on new, high signal-to-noise ratio, R ~ 2500 digital observations from both hemispheres selected from the Galactic O-Star Catalog of Maíz Apellániz et al. and Sota et al. The spectral classification system is rediscussed and a new atlas is presented, which supersedes previous versions. Extensive sequences of exceptional objects are given, including types Ofc, ON/OC, Onfp, Of?p, Oe, and double-lined spectroscopic binaries. The remaining normal spectra bring this first sample to 184 stars, which is close to complete to B = 8 and north of δ = -20° and includes all of the northern objects in Maíz Apellániz et al. that are still classified as O stars. The systematic and random accuracies of these classifications are substantially higher than previously attainable, because of the quality, quantity, and homogeneity of the data and analysis procedures. These results will enhance subsequent investigations in Galactic astronomy and stellar astrophysics. In the future, we will publish the rest of the survey, beginning with a second paper that will include most of the southern stars in Maíz Apellániz et al. The spectroscopic data in this article were gathered with three facilities: the 1.5 m telescope at the Observatorio de Sierra Nevada (OSN), the 3.5 m telescope at Calar Alto Observatory (CAHA), and the du Pont 2.5 m telescope at Las Campanas Observatory (LCO). Some of the supporting imaging data were obtained with the 2.2 m telescope at CAHA and the NASA/ESA Hubble Space Telescope (HST). The rest were retrieved from the DSS2 and Two Micron All Sky Survey (2MASS) surveys. The HST data were obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

VizieR Online Data Catalog: CCDM (Catalog of Components of Double & Multiple stars) (Dommanget+ 2002)

NASA Astrophysics Data System (ADS)

Dommanget, J.; Nys, O.

2002-03-01

This is the second edition of the Catalogue of the Components of Double and Multiple stars (CCDM). The first one, of which a detailed description has been given in Communication de l'Observatoire Royal de Belgique, Serie A, 115, 1994, may be found at the CDS under reference . The complete description of this second edition is published (in French and English) in "Observations et Travaux", a review edited by the Societe Astronomique de France. A detailed historical sketch of the creation and development of the catalogue -- which served as double star data base for the preparation of the HIpparcos Input Catalogue -- has been published in issue 25, pp.29-31 (1999) of this same review. There are no fundamental differences between the two editions: format, presentation and construction are similar. The main difference lies in the important increase of the considered systems of which number expands from 34.031 to 49.325. Few additions exist in the description of the contents of the various columns, and some new codes had to be used for references to astronomical positions, especially related to the introduction of new Hipparcos systems or components to known systems (see the "refpos.dat" file). Concerning the names of the systems in columns 16 to 22, one has also to mention some additions to those given in the INDEX-WDS (C.E.Worley, 1984). They are: AOT = Oss. di Torino ACG = Astr.Cat.Greenw. BAC = P.Bacchus BEW = U.Bastian et al. CRI = F.Crifo DUF = M.Duflot DYL = J. Doyle HDS = Hipparcos JRN = A. Jorissen JKS = M.P.Jenniskens KZA = S.M.Kazeza LMP = P.Lampens LYS = L. Louys MCO = McCormick NYS = O.Nys ONL = Occult. News Letters PWS = Th.Pauwels RSU = M.Rousseau SLE = G.Soulie VHS = P.Verhas Note that: MAL = McAlister in WDS 1984 MCA = McAlister in WDS 1994 Some changes have finally been brought to the names of particular STT and STF systems (App) as shown here, to avoid some confusion that exists with the non (App) systems: --> For STF (App)I, addition of 4000, i.e. STF 4001 instead of STF 1(App)I STF 4002 instead of STF 2(App)I ............... STF 4060 instead of STF 60(App)I --> For STF (App)II, addition of 5000, i.e. STF 5003 instead of STF 3(App)II ............... STF 5012 instead of STF 12(App)II --> For STT (App)I, addition of 4000, i.e. STT 4001 instead of STT 1(App) STT 4005 instead of STT 5(App) ............... STT 4256 instead of STT 256(App) (2 data files).

VizieR Online Data Catalog: CCDM (Components of Double and Multiple stars) (Dommanget+ 2002)

NASA Astrophysics Data System (ADS)

Dommanget, J.; Nys, O.

2002-03-01

This is the second edition of the Catalogue of the Components of Double and Multiple stars (CCDM). The first one, of which a detailed description has been given in Communication de l'Observatoire Royal de Belgique, Serie A, 115, 1994, may be found at the CDS under reference . The complete description of this second edition will be found in its introduction that will be published (in French and English) in "Observations et Travaux", a review edited by the Societe Astronomique de France. A detailed historical sketch of the creation and development of the catalogue -- which served as double star data base for the preparation of the HIpparcos Input Catalogue -- has been published in issue 25, pp.29-31 (1999) of this same review. There are no fundamental differences between the two editions: format, presentation and construction are similar. The main difference lies in the important increase of the considered systems of which number expands from 34.031 to 49.325. Few additions exist in the description of the contents of the various columns (see table 1) and some new codes had to be used for references to astronomical positions, especially related to the introduction of new Hipparcos systems or components to known systems (see the "refpos.dat" file). Concerning the names of the systems in columns 16 to 22, one has also to mention some additions to those given in the INDEX-WDS (C.E.Worley, 1984). They are: AOT = Oss. di Torino ACG = Astr.Cat.Greenw. BAC = P.Bacchus BEW = U.Bastian et al. CRI = F.Crifo DUF = M.Duflot DYL = J. Doyle HDS = Hipparcos JRN = A. Jorissen JKS = M.P.Jenniskens KZA = S.M.Kazeza LMP = P.Lampens LYS = L. Louys MCO = McCormick NYS = O.Nys ONL = Occult. News Letters PWS = Th.Pauwels RSU = M.Rousseau SLE = G.Soulie VHS = P.Verhas Note that: MAL = McAlister in WDS 1984 MCA = McAlister in WDS 1994 Some changes have finally been brought to the names of particular STT and STF systems (App) as shown here, to avoid some confusion that exists with the non (App) systems: --> For STF (App)I, addition of 4000, i.e. STF 4001 instead of STF 1(App)I STF 4002 instead of STF 2(App)I ............... STF 4060 instead of STF 60(App)I --> For STF (App)II, addition of 5000, i.e. STF 5003 instead of STF 3(App)II ............... STF 5012 instead of STF 12(App)II --> For STT (App)I, addition of 4000, i.e. STT 4001 instead of STT 1(App) STT 4005 instead of STT 5(App) ............... STT 4256 instead of STT 256(App) (2 data files).