Observations Of Double Stars Research Articles

Speckle Interferometry at the US Naval Observatory. XI.

The results of 1683 speckle interferometric observations of double stars, made with the 26 inch (66 cm) refractor of the US Naval Observatory, are presented. Each speckle interferometric observation of a system represents a combination of over 2000 short-exposure images. These observations are averaged into 805 mean relative positions and range in separation from 023 to 4334, with a median separation of 433. This is the 11th in a series of papers presenting measurements obtained with this system and covers the period 2004 January 4-December 30. Included in these data are two older measurements whose positions were previously deemed possibly aberrant but are no longer classified this way following a confirming observation. Two of these systems have new orbital elements, which are also presented here.

The first cluster and double star symposium

Cluster, a joint project between the European Space Agency (ESA) and NASA, is the first mission that is composed of four spacecraft flying in formation, and thus the first able to separate spatial and temporal features inside smallscale plasma structures within, and the boundaries between, many regions of the Earth's upper atmosphere (from 19,000–119,000 kilometers altitude).During the past two years, the Cluster mission has been enhanced by the Double Star (DSP) mission, a magnetospheric mission composed of two satellites that is a joint project between the China National Space Administration (CNSA) and ESA.The orbits have been chosen so that interesting conjunctions occur frequently between Cluster and the two DSP satellites. Conducting coordinated studies using simultaneous Cluster and Double Star observations increases the overall scientific return from both missions.

DepAstroCCD an original astrometric tool

A complex software for preparation and treatment of astro photographic plates and double-star observations recorded with CCD cameras is developed. The preparation interface contains a catalogue base for the choice of observation objects and an interface for bringing into accordance the telescope and CCD camera performance with the assumptions of the postprocessor interface. The processing is based on the original development of image gradient removing software and classical FFT method and autocorrelation. The software has been tested on several theoretical and real images of double stars.

Simultaneous Double Star and Cluster FTEs observations on the dawnside flank of the magnetosphere

Abstract. We present Cluster and Double Star-1 (TC-1) observations from a close magnetic conjunction on 8 May 2004. The five spacecraft were on the dawnside flank of the magnetosphere, with TC-1 located near the equatorial plane and Cluster at higher geographic latitudes in the Southern Hemisphere. TC-1, at its apogee, skimmed the magnetopause for almost 8h (between 08:00-16:00 UT). Flux Transfer Events (FTEs), moving southward/tailward from the reconnection site, were observed by TC-1 throughout almost all of the period. Cluster, travelling on a mainly dawn-dusk trajectory, crossed the magnetopause at around 10:30 UT in the same Magnetic Local Time (MLT) sector as TC-1 and remained close to the magnetopause boundary layer in the Southern Hemisphere. The four Cluster spacecraft observed FTEs for a period of 6.5h between 07:30 and 14:00 UT. The very clear signatures and the finite transverse sizes of the FTEs observed by TC-1 and Cluster imply that, during this event, sporadic reconnection occurred. From the properties of these FTEs, the reconnection site was located northward of both TC-1 and Cluster on the dawn flank of the magnetosphere. Reconnection occurred between draped magnetosheath and closed magnetospheric field lines. Despite variable interplanetary magnetic field (IMF) conditions and IMF-Bz turnings, the IMF clock angle remained greater than 70° and the location site appeared to remain relatively stable in position during the whole period. This result is in agreement with previous studies which reported that the dayside reconnection remained active for an IMF clock angle greater than 70°. The simultaneous observation of FTEs at both Cluster and TC-1, separated by 2h in MLT, implies that the reconnection site on the magnetopause must have been extended over several hours in MLT.

Double Star, Cluster, and ground-based observations of magnetic reconnection during an interval of duskward oriented IMF: preliminary results

Abstract. We present a space- and ground-based study exploiting data from the coordinated Cluster and Double Star missions in order to investigate dayside magnetic reconnection under BY+ dominated IMF conditions. In-situ observations of magnetosheath flux transfer events combined with measurements of pulsed poleward and dawnward directed flows in the pre-noon sector high-latitude northern hemisphere ionosphere are interpreted as indications of pulsed magnetic reconnection during an interval in which the IMF remained relatively steady. Observations of newly-reconnected magnetic flux tubes anchored in the northern hemisphere both at mid-latitudes and in the vicinity of the subsolar point suggests that during BY+ dominated IMF, reconnection is not, as proposed previously, limited to the high-latitude magnetopause.

Cluster and Double Star observations of dipolarization

Abstract. We studied two types of dipolarization events with different IMF conditions when Cluster and Double Star (TC-1) were located in the same local time sector: 7 August 2004, 18:00-24:00 UT, during a disturbed southward/northward IMF interval, and 14 August 2004, 21:00-24:00 UT, when the IMF was stably northward. Cluster observed dipolarization as well as fast flows during both intervals, but this was not the case for TC-1. For both events the satellites crossed near the conjugate location of the MIRACLE stations. By using multi-point analysis techniques, the direction/speed of the propagation is determined using Cluster and is then compared with the disturbances at TC-1 to discuss its spatial/temporal scale. The propagation direction of the BZ disturbance at Cluster was mainly dawnward with a tailward component for 7 August and with a significant Earthward component for 14 August associated with fast flows. We suggest that the role of the midtail fast flows can be quite different in the dissipation process depending on the condition of the IMF and resultant configuration of the tail.

Speckle Interferometry at the US Naval Observatory. X.

The results of 3047 speckle interferometric observations of double stars, made with the 26 inch (66 cm) refractor of the US Naval Observatory, are presented. Each speckle interferometric observation of a system represents a combination of over a thousand short-exposure images. These observations are averaged into 1572 mean relative positions and range in separation from 020 to 6286, with a median separation of 419. This is the 10th in a series of papers presenting measures obtained with this system and covers the period 2003 January 13 through 2003 December 1. Included in these data are nine older measures whose positions were previously deemed possibly aberrant but are no longer classified this way following a confirming observation. Four of these systems have new orbital elements, which are presented here as well.

Observations of Hipparcos Double Stars with the WiynTelescope

AbstractA program of follow-up observations of HIPPARCOS Double Stars has been started using the WIYN 3.5-m Telescope at Kitt Peak, Arizona. Observations are made with the recently-completed RYTSI speckle camera, which is capable of determining reliable magnitude differences at various wavelengths down to the diffraction limit of the telescope. Thus in addition to precise relative astrometry, component magnitudes and colors can be obtained in a survey mode for all systems observed. Preliminary results and system capabilities are described. The benefits of a sustained program of observations of the HIPPARCOS Double Stars include populating the mass-luminosity relation with many more points (once the orbital status of these stars is known and orbital parameters are determined in sufficient detail for gravitationally bound pairs), robust tests of stellar evolution calculations in cases where at least one component has evolved off the main sequence, and a more complete picture of the nearby field binary population.

Speckle Interferometry at the US Naval Observatory. IX.

The results of 3056 speckle interferometric observations of double stars, made with the 26 inch (66 cm) refractor of the US Naval Observatory, are presented. Each speckle interferometric observation of a system represents a combination of over a thousand short-exposure images. These observations are averaged into 1675 mean relative positions and range in separation from 019 to 4521, with a median separation of 299. This is the ninth in a series of papers presenting measures obtained with this system and covers the period 2002 January 1 through 2002 December 29. Included in these data are 28 older measures whose positions were previously deemed possibly aberrant but are no longer classified this way following a confirming observation. Nine of these systems have new orbital elements, which are presented here as well.

Speckle Interferometry at the US Naval Observatory. VIII.

The results of 2044 speckle interferometric observations of double stars, made with the 26 inch (66 cm) refractor of the US Naval Observatory, are presented. Each speckle interferometric observation of a system represents a combination of over a thousand short-exposure images. These observations are averaged into 1399 mean positions and range in separation from 016 to 1497, with a mean separation of 251. This is the eighth in a series of papers presenting measures obtained with this system and covers the period 2001 March 18 through 2001 December 30.

The 2001 US Naval Observatory Double Star CD-ROM. IV. The Photometric Magnitude Difference Catalog

The Photometric Magnitude Difference Catalog, maintained at the US Naval Observatory, is a collection of magnitude-difference measures for double stars and serves as a repository for double star observations where no astrometry is given. At the present time, it consists of 19,594 measures of 10,475 systems with a mean Δm of 1.90. Because of the nonuniformity of filters and the possible variability of one or more components in a system, no WDS-like summary line is provided. Rather, all the data are presented and their interpretation is left as an exercise for the reader. This catalog is one of four USNO double star catalogs to be included on a new CD-ROM. A brief summary and statistical analysis of the contents of the catalog are presented.

Speckle Interferometry at the US Naval Observatory. VII.

The results of 2014 speckle interferometric observations of double stars, made with the 26 inch (66 cm) refractor of the US Naval Observatory, are presented. These observations are averaged into 1266 mean positions and range in separation from 021 to 1341, with a mean separation of 261. This is the seventh in a series of papers presenting measures obtained with this system and covers the period 2000 January 10 through December 8.

Speckle Interferometry of New and Problem [ITAL]HIPPARCOS[/ITAL][ITAL]Hipparcos[/ITAL] Binaries. II. Observations Obtained in 1998–1999 from M[CLC]c[/CLC]Donald Observatory

The Hipparcos satellite made measurements of over 9734 known double 3406 new double and 11,687 unresolved but possible double stars. The high angular resolution afforded by speckle interferometry makes it an efficient means to confirm these systems from the ground, which were first discovered from space. Because of its coverage of a different region of angular separation–magnitude difference (ρ-Δm) space, speckle interferometry also holds promise to ascertain the duplicity of the unresolved Hipparcos stars. Presented are observations of 116 new Hipparcos double stars and 469 Hipparcos problem stars, as well as 238 measures of other double stars and 246 other high-quality nondetections. Included in these are observations of double stars listed in the Tycho-2 Catalogue and possible grid stars for the Space Interferometry Mission.

Systematic Effects in ICCD-based Speckle Interferometry of Double Stars

Speckle interferometric observations of double stars enjoy considerably higher weight in orbital solutions than visual observations. This is justified on the basis of their higher precision and impersonal nature. It is crucial, therefore, that sources of systematic error in speckle observations are identified and controlled to a level commensurate with their low random errors. Accurate calibration is of primary importance. Other sources of systematic error that affect ICCD-based speckle interferometry include imperfect CCD charge transfer efficiency, fixed pattern noise, and nonuniform background in the autocorrelation function. All of these errors and their remedies are discussed. The restoration of observations compromised by fixed pattern noise is evaluated, and results for 30 such observations are given.

Multicolour observations of nearby visual double stars. New CCD measurements and orbits

We present multicolour CCD observations of nine nearby visual double stars obtained in August and September 1999 with the 1.3-m telescope at Skinakas Observatory. The results consist of relative positions (epochs, angular separations and position angles) and differential BVRI photometry. We confirm the physical association in eight cases. Previously known orbits do not match the new data for three systems. Orbits have been recalculated when sufficient data were available. We principally improve the precision of the known orbits for three binaries and show the acute lack of precision in two other cases. In one case, the components are shown to move apart with a linear relative speed of 0.050′′/yr.

Binarity of Hipparcos Main Sequence Survey Stars

Hipparcos observations of double stars, mainly A and F primaries, are modelled in order to check the statistics of double-star solutions in the Hipparcos Catalogue and to set quantitative limits on binary distributions. The number of companions per primary is estimated to 0.25 ± 0.05 for semi-major axes from 1 to 10 AU, and to 0.43 ± 0.20 for the range 10–100 AU. The total multiplicity found is between 0.9 and 1.2.

Speckle Observations of Double Stars with PISCO at Pic du Midi: Measurements in 1998

We present astrometric measurements of binary stars based on speckle observations of 164 independent sequences of observations (~104 frames each) made with the PISCO speckle camera at Pic du Midi. These measurements concern 147 objects, of which 134 were found to be double with a separation in the range 01-10. These objects were mainly selected among grade 3 orbits to improve the accuracy of their orbits and to constrain their masses. We discovered the binarity of 59 Aql with an angular separation of 009 ± 001.

Speckle Interferometry at the US Naval Observatory. VI.

The results of 1068 speckle interferometric observations of double stars, made with the 26 inch (0.66 m) refractor of the US Naval Observatory, are presented. These observations are averaged into 841 means of 815 binary stars. The systems range in separation from 022 to 601 with a mean separation of 221 and have a limiting secondary magnitude of V = 12.5. This is the sixth in a series of papers presenting measures obtained with this system, and it covers the period 1999 January 1 through 2000 January 9.

The Hipparcos transit data: What, why and how?

The Hipparcos Transit Data are a collection of partially reduced, fully calibrated observations of (mostly) double and multiple stars obtained with the ESA Hipparcos astrometry satellite. The data are publicly available, as part of the CD-ROM set distributed with the Hipparcos and Tycho Catalogues (ESA SP--1200, 1997), for about a third of the Hipparcos Catalogue entries including all confirmed or suspected non-single stars. The Transit Data consist of signal modulation parameters derived from the individual transits of the targets across the Hipparcos focal grid. The Transit Data permit re-reduction of the satellite data for individual objects, using arbitrarily complex object models in which time-variable photometric as well as geometric characteristics may be taken into account. We describe the structure and contents of the Transit Data files and give examples of how the data can be used. Some of the applications use standard astronomical software: Difmap or AIPS for aperture synthesis imaging, and GaussFit for detailed model fitting. Fortran code converting the data into formats suitable for these application programs has been made public in order to encourage and facilitate the use of Hipparcos Transit Data.

Speckle observations of double and multiple stars at Pic du Midi: Measurements during 1995 and 1997 and new orbits

We present speckle observations of 48 double and multiple stars observed with the 2-meter \T elescope Bernard Lyot (TBL) in December 1995, January 1997 and June 1997. Angular separations, absolute position an- gles and relative photometry result from these observa- tions. New orbital elements have been recalculated for 8 double stars.