Observations Of Double Stars Research Articles

SPECKLE INTERFEROMETRY AT THE USNO FLAGSTAFF STATION: OBSERVATIONS OBTAINED IN 2008 AND NINE NEW ORBITS

Results are presented for 299 speckle interferometric observations of double stars, obtained in 2008 at the USNO Flagstaff Station using the 1.55 m Kaj Strand Astrometric Reflector. Separations range from 015 to 988, with a median of 222. This observing run concentrated on neglected systems, as well as systems in need of improved orbital elements; new orbital solutions have been determined for nine systems as a result.

SPECKLE INTERFEROMETRY AT THE U.S. NAVAL OBSERVATORY. XVII.

The results of 3362 intensified CCD observations of double stars, made with the 26 inch refractor of the U.S. Naval Observatory, are presented. Each observation of a system represents a combination of over 2000 short-exposure images. These observations are averaged into 1970 mean relative positions and range in separation from 0. �� 78 to

SPECKLE INTERFEROMETRY AT THE U.S. NAVAL OBSERVATORY. XVI.

The results of 1031 speckle-interferometric observations of double stars, made with the 26 inch refractor of the U.S. Naval Observatory, are presented. Each speckle-interferometric observation of a system represents a combination of over two thousand short-exposure images. These observations are averaged into 457 mean relative positions and range in separation from 015 to 1694, with a median separation of 303. The range in V-band magnitudes for the primary (secondary) of observed targets is 3.1-12.9 (3.2-13.3). This is the sixteenth in a series of papers presenting measurements obtained with this system and covers the period 2009 January 12 through 2009 December 17. Included in these data are 12 older measurements whose positions were previously deemed possibly aberrant, but are no longer classified this way following a confirming observation. Also, 10 pairs with a single observation are herein confirmed. This paper also includes the first data obtained using a new ICCD with fiber optic cables.

SPECKLE INTERFEROMETRY AT THE U.S. NAVAL OBSERVATORY. XV.

Results of 2433 intensified CCD observations of double stars, made with the 26-inch refractor of the U.S. Naval Observatory are presented. Each observation of a system represents a combination of over 2000 short-exposure images. These observations are averaged into 1013 mean relative positions and range in separation from 0.96" to 58.05", with a mean separation of 13.50". This is the 15th in this series of papers and covers the period 2008 January 3 through 2008 December 21.

Interplanetary shock transmitted into the Earth's magnetosheath: Cluster and Double Star observations

Abstract. On day 7 May 2005, the plasma instruments on board Double Star TC1 and Cluster SC3 spacecraft register inside the magnetosheath, at 19:15:12 and 19:16:20 UT, respectively, a strong pressure pulse due to the impact of an interplanetary shock wave (IS) on the terrestrial bow shock. The analysis of this event provides clear and quantitative evidences confirming and strengthening some results given by past simulations and observational studies. In fact, here we show that the transmitted shock is slowed down with respect to the incident IS (in the Earth's reference frame) and that, besides the transmitted shock, the IS – bow shock interaction generates a second discontinuity. Moreover, supported also by a special set three-dimensional magnetohydrodynamic simulation, we discuss, as further effects of the interaction of the IS with the magnetosphere, other two interesting aspects of the present event, that is: the TC1 double crossing of the bow shock (observed few minutes after the impact of the IS) and the presence, only in the SC3 data, of a third discontinuity produced inside the magnetosheath.

SPECKLE INTERFEROMETRY AT MOUNT WILSON OBSERVATORY: OBSERVATIONS OBTAINED IN 2006-2007 AND 35 NEW ORBITS

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.

SPECKLE INTERFEROMETRY AT THE U.S. NAVAL OBSERVATORY. XIV.

The results of 2033 intensified CCD observations of double stars, made with the 26 inch refractor of the U.S. Naval Observatory, are presented. Each observation of a system represents a combination of over 2000 short-exposure images. These observations are averaged into 1297 mean relative positions and range in separation from 0. �� 54 to 58.

Magnetosphere response to the 2005 and 2006 extreme solar events as observed by the Cluster and Double Star spacecraft

The four identical Cluster spacecraft, launched in 2000, orbit the Earth in a tetrahedral configuration and on a highly eccentric polar orbit (4–19.6 R E). This allows the crossing of critical layers that develop as a result of the interaction between the solar wind and the Earth’s magnetosphere. Since 2004 the Chinese Double Star TC-1 and TC-2 spacecraft, whose payload comprise also backup models of instruments developed by European scientists for Cluster, provided two additional points of measurement, on a larger scale: the Cluster and Double Star orbits are such that the spacecraft are almost in the same meridian, allowing conjugate studies. The Cluster and Double Star observations during the 2005 and 2006 extreme solar events are presented, showing uncommon plasma parameters values in the near-Earth solar wind and in the magnetosheath. These include solar wind velocities up to ∼900 km s −1 during an ICME shock arrival, accompanied by a sudden increase in the density by a factor of ∼5 and followed by an enrichment in He ++ in the secondary front of the ICME. In the magnetosheath ion density values as high as 130 cm −3 were observed, and the plasma flow velocity there reached values even higher than the typical solar wind velocity. These resulted in unusual dayside magnetosphere compression, detection of penetrating high-energy particles in the magnetotail, and ring current development following several successive injections of energetic particles in the inner magnetosphere, which “washed out” the previously formed nose-like ion structures.

Observations of double stars at Pulkovo with 65 cm Zeiss refractor

Some results of the photographic observations of double stars with 65 cm refractor of Pulkovo observatory are presented. We use the apparent motion parameters (AMP) method which allows to determine the orbits and to carry out the dynamical investigation of wide binaries on the basis of a short arc of their orbital motion. We have determined more than 40 orbits for wide pairs and also the sum of masses and in some cases—the mass-ratio of components. The references to our works and the basic results of observations are contained in Kisselev et al. [2004. Catalogue of relative positions of visual double stars made on the observations with 26 ″ refractor of Pulkovo observatory. Strassbourg, I/297]. We apply two ways of revealing the hidden mass of our stars, namely: revealing of possible perturbations from comparison of observational and calculated positions using differences O–C (for instance, perturbations in the orbital motion of ADS 15571) and also by means of comparison of the sum of the masses obtained by us and the sum of the masses obtained by means of the mass-luminosity relation. An excess of masses of about 1–3 solar masses is detected for binaries: ADS 497, ADS 8450 and ADS 10329 by means of last method. The estimations of the masses for some binaries are discussed. Also we justify the necessity of precise parallaxes and relative radial velocities of stars, which could be measured by space telescopes such as the GAIA as the additional parameters for determination of orbits of binaries.

Coordinated Cluster and Double Star observations of the dayside magnetosheath and magnetopause at different latitudes near noon

We present results of a favorable conjunction where the equatorial spacecraft (TC‐1) of the Double Star mission exits the dayside magnetopause near the equator, while Cluster is inbound, near the southern cusp. This configuration makes it possible to compare observations of the magnetopause, around the same magnetic local time but at different latitudes. In this paper, we report on the general properties of the magnetosheath plasma at the two latitudes: unlike predictions from gasdynamic modeling, the density is found lower near the nose of the magnetopause than further downstream. Then, we present three interesting events. First, an FTE is observed at TC‐1 and not at Cluster; we discuss the implications this has on the evolution of FTEs and on the size of the reconnection site. Then, a structure observed at both spacecraft is interpreted as a bulge progressing along the magnetopause. It is not clear whether this bulge is actually the remnant of an FTE or a running pulse that makes Cluster sense the reconnection layer. In any case, a rotational discontinuity is observed within it. At last, a northward turning of the magnetosheath magnetic field is observed at TC‐1 and a reverse FTE is subsequently seen at Cluster, suggesting that magnetic reconnection is very fast to set up following a change in the IMF orientation.

Occurrence of reconnection jets at the dayside magnetopause: Double Star observations

We present a statistical study on reconnection occurrence at the dayside magnetopause performed using the Double Star TC1 plasma and magnetic field data. We examined the magnetopause crossings that occurred during the first year of the mission in the 0600–1800 LT interval and we identified plasma flows, at the magnetopause or in the boundary layer, with a different velocity with respect to the adjacent magnetosheath. We used the Walén relation to test which of these flows could be generated by magnetic reconnection. For some event we observed opposite‐directed reconnection jets, which could be associated with the passage of the X‐line near the satellite. We analyzed the occurrence of the reconnection jets and reconnection jet reversals in relation to the magnetosheath parameters, in particular the local Alfvèn Mach number, the plasma β, and the magnetic shear angle. We also studied the positions and velocities of the reconnection jets and jet reversals in relation to the magnetosheath magnetic field clock angle. We found that the observations indicate the presence of a reconnection line hinged near the subsolar point and tilted according to the observed magnetosheath clock angle, consistently with the component merging model.

Reconnection at the dayside magnetopause: Comparisons of global MHD simulation results with Cluster and Double Star observations

This study uses two conjunctions between Cluster and Double Star TC‐1 spacecraft together with global magnetohydrodynamic (MHD) simulations to investigate the large‐scale configuration of magnetic reconnection at the dayside magnetopause. Both events involve southward interplanetary magnetic fields with significant By components. The first event occurred on 8 May 2004, while both spacecraft were exploring the dawn flank of the magnetosphere; TC‐1 was skimming the magnetopause whereas Cluster was exploring higher latitudes. Results from a global MHD simulation show the formation of an equatorial merging line in the morning sector and suggest that the three‐dimensional geometry of the merging region is mostly a radial juxtaposition of planes displaying X‐type reconnection geometries. The second conjunction was on 6 April 2004. During this event, Cluster was located at high latitudes and close to the noon‐midnight meridian, while TC‐1 was exploring the dawnside at low latitudes. Analysis of the simulation reveals that both antiparallel and component merging occurred simultaneously. Three‐dimensional rendering of the parallel electric field indicates that component merging initiated in the subsolar magnetopause. Simulation runs carried out using different parameters in the model suggest that the spread of the merging region depends on the local resistivity. The subsolar‐merging region grows with increasing resistivity values and becomes patchy when a resistivity threshold is used. However, the region of component merging appears to remain spatially constrained to the subsolar region where stronger parallel electric fields occur and no clear connection with the antiparallel‐merging regions is found for the range of parameters surveyed.

SPECKLE INTERFEROMETRY AT THE USNO FLAGSTAFF STATION: OBSERVATIONS OBTAINED IN 2003-2004 AND 17 NEW ORBITS

Results are presented for 353 speckle interferometric observations of double stars, obtained in 2003 and 2004 at the USNO Flagstaff Station using the 1.55 m Kaj Strand Astrometric Reflector. Separations range from 012 to 742, with a median of 042. These two observing runs concentrated on systems in need of improved orbital elements, and new solutions have been determined for 17 systems as a result.

Photometric detection of pulsations in the stars of the wide binary WDS 12483-6708

Die Serie Communications in Asteroseismology (CoAst) stellt eine international gefragte Plattform für wissenschaftliche Publikationen der neuesten Forschungsergebnisse auf dem Gebiet der Asteroseismologie dar. Forschungsgegenstand der Asteroseismologie sind veränderliche und pulsierende Sterne. Neben den halbjährlich erscheinenden regulären Ausgaben mit Beiträgen aus der laufenden Forschung werden auch Sonderausgaben für Konferenzberichte bzw. Programmhandbücher herausgegeben. Volume 153 beinhaltet eine Vielzahl von Arbeiten mit Ergebnissen aus erdgebundenen und satellitengestüzten Beobachtungen pulsierender Sterne sowie über den Vergleich mit theoretischen Modellen. Erstmals berichtet auch das von der EU eingerichtete Forschungsnetzwerk HELAS - European Helio- and Asteroseismology Network - über neue Instrumente und Strukturen für den Daten- und Wissensaustausch unter Astronomen.

Speckle Interferometry at the US Naval Observatory. XIII.

The results of 1424 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 1053 mean relative positions and range in separation from 0.36'' to 61.92'', with a median separation of 10.31''. This is the 13th in a series of papers presenting measurements obtained with this system and covers the period 2006 January 12-December 29. Included in these data are nine older measurements whose positions were previously deemed possibly aberrant but are no longer classified this way following a confirming observation. This paper also includes the first data obtained using a new secondary camera, designed and built at USNO.

Understanding magnetotail current sheet meso-scale structures using MHD simulations

Recent Cluster observations have strongly supported the existence of meso-scale structure in the magnetotail current sheet. In our study, a magnetohydrodynamic simulation event study exhibited current sheet behavior comparable to that seen in the Cluster observations. Geotail and DoubleStar observations also show that the simulation is providing a realistic representation of the magnetosphere during the period of interest; that is, when the current sheet evidently becomes bifurcated. The magnetohydrodynamic simulation allows us to place the local observations into a global contest. It shows that the observations can be explained in terms of localized reconnection tailward of the Cluster location and the formation of a flux rope nearby. The simulation also features wave-like structure across the current sheet.

Modeling PSBL high speed ion beams observed by Cluster and Double Star

On October 8, 2004, the Cluster and Double Star spacecraft crossed the near-Earth (12–19 R E) magnetotail neutral sheet during the recovery phase of a small, isolated substorm. Although they were separated in distance by ∼7 R E and in time by ∼30 min, both Cluster and Double Star observed steady, but highly structured Earthward moving >1000 km/s high speed H + beams in the PSBL. This paper utilizes a global magnetohydrodynamic (MHD) simulation driven by Wind spacecraft solar wind input to model the large-scale structure of the PSBL and large-scale kinetic (LSK) particle tracing calculations to investigate the similarities and differences in the properties of the observed beams. This study finds that the large-scale shape of the PSBL is determined by the MHD configuration. On smaller scales, the LSK calculations, in good qualitative agreement with both Cluster and Double Star observations, demonstrated that the PSBL is highly structured in both time and space, on time intervals of less than 2 min, and spatial distances of the order of 0.2–0.5 R E. This picture of the PSBL is different from the ordered and structured region previously reported in observations.

Do BBFs contribute to inner magnetosphere dipolarizations: Concurrent Cluster and Double Star observations

We examined the relationship between bursty bulk flow (BBF) events observed by Cluster between −19 RE < X < −12 RE and dipolarization events observed by Double Star TC1 between −13 RE < X < −6 RE. TC1 observed dipolarizations for ∼33% of the cases when BBFs were observed by Cluster. During these dipolarization events the TC1 location was closer to the Cluster location and the local BZ at TC1 was smaller than during events where TC1 observed no clear dipolarization associated with BBFs at Cluster. This result suggests that (1) flow‐associated activity dissipates within a limited spatial scale, 4–8 RE, and that (2) the initial magnetic topology in the inner magnetosphere can contribute strongly to fast flow penetration toward the Earth. The fact that there were no TC1 dipolarization events at X > −8 RE associated with BBFs at Cluster in our dataset suggests two possibilities: near‐geosynchronous dipolarization needs another mechanism in addition to flux pile‐up and braking, or during near‐geosynchronous dipolarization the near‐tail current sheet/plasma sheet is too thin to be observed by Cluster.

Speckle Interferometry at the US Naval Observatory. XII.

The results of 1657 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 1111 mean relative positions and range in separation from 016 to 1699, with a median separation of 165. This is the 12th in a series of papers presenting measurements obtained with this system and covers the period 2005 January 3-December 29. Included in these data are 30 older measurements whose positions were previously deemed possibly aberrant but are no longer classified this way following a confirming observation. Sixteen of these systems have new orbital elements, which are presented here as well. For η Coronae Borealis (STF 1937) we determine masses of 1.207 and 1.077 M⊙ and an orbital parallax of 54.95 mas.

Activities and Achievements of the Double Star Committee of the Société Astronomique de France

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 (1888–1974), an amateur before circumstances prompted him to become a professional astronomer, who devoted his life to double stars. Kenneth Glyn Jones wrote a biography and Charles Fehrenbach his obituary. Jean-Claude Thorel studied his life and career in double star observations (see Section 10 below). In the 1930s, another precursor of the Commission des Étoiles Doubles, Maurice DURUY (1894–1984) invented the micrometer with a comparison star, and applied the diffraction micrometer invented by Ejnar Hertzsprung to the measure of double stars, which he regularly observed at Nancy with a 275-mm telescope, at Lyon with a 162-mm telescope and in his observatory of Beaume-Mêle with a 40-cm and later a 60-cm telescope at Le Rouret (Alpes–Maritimes). He measured standard pairs of the list of Paul Muller and published his measures in the Journal des Observateurs; these measures requested by Paul Muller aimed at comparisons of between observers. He also collaborated with the Webb Society of Great Britain; Glyn Jones published his astronomical biography. Already in 1924, the pediatrician Paul BAIZE (1901–1995) 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 “career" (24044). He also made orbit calculations and established a formula for the calculation of dynamic parallaxes in 1946. He wrote articles explaining new observation techniques devoted to double stars in the magazine L'Astronomie and continued his astronomical activity until the beginning of the 1990s. Glyn Jones published an astronomical biography of Paul Baize. In the 1960s, Bernard CLOUET and the late Robert SAGOT (1910–2006) 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 (1908–1998) made the acquaintance of renowned professional astronomer Paul COUTEAU and learned from him how to measure double stars. Each year, he stayed for two weeks at Nice and conducted his observations with the 50-cm refractor of the Nice Observatory. In 1978, Paul COUTEAU published the first book in French devoted to double stars: L'observation des étoiles 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 Étoiles Doubles