Boyden Observatory Research Articles

Transient behaviour of three SU UMa-type dwarf novae: AR Pic, QW Ser, and V521 Peg

ABSTRACT Changes in the supercycle lengths of some SU UMa-type dwarf novae have been detected by other studies, and indicate that the mass transfer rates noticeably decrease over time. We investigated the supercycle lengths of three SU UMa-type dwarf novae: AR Pic, QW Ser, and V521 Peg, to determine if they have detectable changes in their supercycles. We present the results of optical spectroscopic and photometric observations of these sources. Our observations were conducted in 2016 and 2017 at the Boyden Observatory and the Sutherland station of the South African Astronomical Observatory. The quiescent results indicated that all three sources are typical SU UMa-type dwarf novae. We also present results of AR Pic and QW Ser in outburst and of V521 Peg during a precursor outburst and superoutburst. Light curves were supplemented by the Catalina Real-Time Transient Survey, the ASAS-3 and ASAS-SN archives, and the AAVSO International Database in order to investigate the long-term behaviour of these sources. Our results combined with catalogued properties for all short-period dwarf novae show a possible relationship between the supercycle time in SU UMa systems and their orbital periods, which is interpreted as the decline in the mass transfer rate as systems evolve towards and away from the ‘period minimum’. At the shortest orbital periods, SU UMa systems are almost indistinguishable from WZ Sge systems. However, we propose that the scaleheight between the secondary’s photosphere and L1 may be a factor that distinguish the SU UMa subclasses.

The development of the Schmidt telescope

AbstractBernhard Schmidt (1879–1935) was born in Estonia. After a few years of studying engineering he ran an optical workshop in Mittweida, Saxonia, between 1901 and 1927. Astronomers appreciated the quality of his telescopes. Starting in 1925, on behalf of the Hamburg Observatory, he developed a short focal length optical system with a large field of view. For this purpose, Schmidt moved his workshop to the observatory. He succeeded in inventing the “Schmidt telescope” which allows the imaging of a large field of the sky without any distortions. Schmidt's first telescope (spherical mirror diameter 0.44 m, correction plate 0.36 m diameter, aperture ratio 1:1.75, and focal length 0.625 m) has been used since 1962 at the Boyden Observatory in Bloemfontein/South Africa. Apart from his 0.36m telescope, Schmidt produced a second larger one of 0.60m aperture. Shortly after Schmidt's death, the director of the observatory published details on the invention and production of the Schmidt telescope. After World War II, Schmidt telescopes have been widely used. The first large Schmidt telescope, the “Big Schmidt” (1.26 m), Mount Palomar, USA, was completed in 1948. The 0.80 m Schmidt telescope of Hamburg Observatory, planned since 1936, finished in 1954, is now on Calar Alto/Spain (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Alan Hamer Jarrett 1925–2007

Professor Alan Hamer Jarrett, former Director of the Boyden Observatory in Bloemfontein, died on 28 January 2007. He was born on 2 February 1925 in Manchester, United Kingdom, where he attended Manchester Grammar School until 1943. He obtained a BSc at Leeds University in 1946, an MSc at Manchester University in 1949 (under P.M.S. Blackett) and a PhD at St Andrews University in 1952 (under Erwin Findlay-Freundlich).

The variable stars in the globular cluster NGC 2808

view Abstract Citations (22) References (31) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Variable Stars in the Globular Cluster NGC 2808 Clement, Christine M. ; Hazen, Martha L. Abstract The variable stars of the globular cluster NGC 2808 have been studied on 244 plates taken at the Boyden Observatory in South Africa, and at the Las Campanas and Cerro Tololo observatories in Chile between 1935 and 1985. Three new variables have been discovered and classified. Nine stars previously classified as variables were also studied and only two of them were found to be variable. Of the five known variables, two are of the RR Lyrae type, one is a short-period Population II Cepheid, and the two others are red semiregulars. All of the variables have apparent magnitudes appropriate for cluster membership. No double-mode pulsations were detected in the RR Lyrae stars. Publication: The Astronomical Journal Pub Date: February 1989 DOI: 10.1086/114991 Bibcode: 1989AJ.....97..414C Keywords: Blue Stars; Globular Clusters; Red Giant Stars; Stellar Spectrophotometry; Variable Stars; Abundance; Cepheid Variables; Color-Magnitude Diagram; Light Curve; Metallicity; Stellar Magnitude; Astronomy; CLUSTERS: GLOBULAR; STARS: VARIABLE; STARS: CEPHEIDS; STARS: RR LYRAE; STARS: LONG-PERIOD VARIABLES full text sources ADS | data products SIMBAD (13)

Observed mass motions in limb prominences

Line shifts occurring on Fabry-Perot interferograms of four limb prominences obtained at Boyden Observatory are reported and analyzed in terms of mass motions of the emitting parts of the prominences. The contribution of these motions to the energy balance of prominences is discussed.

Comet Tago-Sato-Kosaka 1969 IX: Tail structure 25 December 1969 to 12 January 1970

On photographs taken between 25 December 1969 and 12 January 1970 with the Michigan Curtis Schmidt on Cerro Tololo and the Hamburg Schmidt at the Boyden Observatory, Comet 1969 IX is seen projected on planes nearly perpendicular to its orbit. During this period the Type I tail was free of major structural disturbances, and the faintness of the Type II tail facilitated study of the Type I tail near the lead. Characteristics of the main Type I tail are described in Part II. A classification of the tail forms according as the tail had the form of a fan of rays or a wedge, the orientation of the tail axis, and the angular width of the tail are discussed in Section IIA. In Section IIB the structure of the tail from 26 to 31 December, a period within which a disconnection of the tail took place, is viewed as the possible result of the passage across the comet of an interplanetary magnetic sector boundary, as proposed by Niedner and Brandt (1977, Bull. Amer. Astron. Soc. 4). In Sections IIC and IID waves in rays and the onset of turbulence are considered. Section IIIA is devoted to unusually long and bright off-axis rays; data on longitudinal forms, closing rate to the axis, and photometry of a ray are presented. In Section IIIB the structure of a “plume” of seven nearly parallel rays is related to the configuration of magnetic field lines predicted by Schmidt and Wegmann (1976, IPP Report 6/147). The orientations of the plume rays are consistent with those of the calculated field lines; the inferred rate of generation of the rays is about 1/hr.

A Surface Polarization Survey of the Milky Way and the Zodiacal Light

An elliptical Surface polarimetry of the Night Sky has been carried out at the Boyden Observatory, South Africa. The Milky Way is linearly polarized by p = 1 to 2 % (Figure 1); 11 regions also show a circular polarized light contribution (Table I).The amounts of circular polarization near v ≈ 0.1 % or less, observed within the Zodiacal Light, are generally not exceeding twice the error of measurement: see Staude and Schmidt (1972). (v > 0 is defined by clockwise rotation, looking against the light source).

Radial velocities of early-type stars

With the Fehrenbach objective prism radial velocities of about 700 stars of type B0 to A0 were determined in two fields of the Southern Milky Way (lII = 295° bII = −0.6°; lII = 320° bII = −2.5°), with a mean error of ±20 km s−1. An additional photographic UBV-photometry with plates of the ADH-telescope at Boyden Observatory was accomplished. Minimum distances for the stars resulted from absorption-corrected magnitudes and a MK-spectral classification. About 200 stars lay at distances greater than 1.5 kpc from the sun. The largest distances determined were 5 kpc. From the radial velocities and distances circular velocities were derived and plotted against galactocentric distances R. Even within the possible error limits a positive velocity gradient showed up in the range 8 kpc < R < 9.5 kpc, which French authors had already found for the region 10.5 kpc < R < 12.5 kpc. If there do not exist significant deviations from circular motion for these stars, a conformity with Schmidt's 1965 model cannot be obtained.

Progress report of the current research on the galactic structure in Vela

In order to find evidence for supporting or rejecting the idea of a major spiral feature in the direction of lII = 270°, as proposed by Velghe (1969), it is necessary to extend the limits of the survey both in longitude and in distance. The extension towards smaller longitudes was placed arbitrarily at lII = 257°, while in the direction of Carina, the investigation was confined to lII = 285°. In doing so, sufficient overlap was made with the studies by Velghe and by Graham and Lyngå (1965), in order to get a homogeneous and complete material in a large, but important section of the southern Milky Way. Following the same technique as outlined in the preceding paper, about 360 young type stars were selected from objective-prism plates, taken with the ADH-telescope of the Boyden Observatory. Later on (in 1966) a first series of UBV photoelectric measurements was carried out at the Boyden Observatory, however with insufficient accuracy. Before finishing the reductions, a second series was made with the 1m-photometric telescope of the ESO (La Silla, Chile) at the end of 1968. These (ESO)-values, in the Johnson UBV-system, will be available before long. In the definite form, they will be combined with the Boyden-measurements. The surface distribution of the stars in the whole section is shown in Figure 1. Many of the stars between lII = 273° and 282° are of rather late B-type, but they were included for the purpose of determining the absorption in this field. The space distribution will enable us to decide whether the edge of the Carina spiral feature is seen in this direction (Bok et al., 1969) and if there is any indication for a possible linkage from Carina to Puppis. To extend the distance limit, a search for faint blue stars, applying the idea of Bok (1966), is planned and some photoelectric sequences will be measured early in 1970 as standards for photographic photometry. As another approach to the galactic structure in this field a complete set of red objective-prism plates has been obtained since 1966, to pick out the objects with H α in emission. As for the reality of the association I Vel, some preliminary material on Radial Velocities will be collected also in 1970, using the Fehrenbach astrograph of the ESO at La Silla (Chile).

A study of O and B stars in Vela, along the galactic equator

The spiral structure of our Galaxy, as defined by optical evidence, shows a striking gap around lII = 270°. Intrigued by this feature, the author started, in 1955, a survey of early type stars based on objective-prism plates taken with the ADH-Schmidttelescope of the Boyden Observatory (South-Africa); dispersion of the spectra: 240 Å/mm at Hγ.

Photometric investigation of the association Car OB 2

A photometric investigation of the association Car OB 2 was carried out with a photoelectric standard sequence observed with the ESO photometric telescope and plates taken with the ADH telescope of Boyden Observatory. The distance of Car OB 2 is 2.04 kpc, the color excess EB–V is 0m.38. The main sequence of this ‘OB’ association reaches at least to late A-type stars. The luminosity function was determined and compared with the luminosity functions of very young open clusters observed by Walker (1957). The distance of a group of 13 early-type stars in the area of Car OB 2 (‘group c’) was found to be 2.5 kpc, the reddening 0m.68. The relation of Car OB 2 and group c to the structure of the Carina arm is regarded.

The new Stockholm spectral survey of the Southern Milky Way

This article gives a brief description of a new survey of the Southern Milky Way which is being carried out at the Stockholm Observatory. Photographic and photoelectric material, obtained at the Boyden Observatory in South Africa, is used for the selection of interesting objects, and for a preliminary classification and photometry of these objects to facilitate subsequent detailed investigations. Some comments are added concerning the procedures involved, and also relating to a special programme concerned with the search for associations, which may lead to interesting results.

Two-color photoelectric photometry of the earthshine

This paper presents two-color observations of the earthshine made during 14 nights of July and August 1965 at the Boyden Observatory in South Africa. Although the information provided is limited because the observations cover a range in phase angle of only 45°, it is possible to derive earth albedos of 0.30 in V and 0.36 in B, both accurate to about 10%.

FLARES OF V 1216 SAGITTARII

The flare star V 1216 Sagittarii (Ross 154, a = lSMT^, 8 = 23°52' (1966), vis. mag. 10.5, dM4.5e) was observed photoelectrically at the Boyden Observatory for 114 hours from June 26 until July 26, 1966. The purpose of this series of observations was, first, to provide optical coverage for radio observations at Jodrell Bank and, second, to search for recently suspected recurrences of certain time lapses between flares noted in another flare star, YZ Canis Minoris (Andrews 1966). The instruments used were the 16-inch Nishimura and 60-inch Rockefeller reflectors, both equipped with E.M.I. 6256A photomultipliers and standard UBV filters. Ten possible flares were recorded, one of which was a major optical event ( Fig. 1 ) . Details of the photoelectric coverage are given in Table I where interruptions to monitoring of more than 5 minutes are indicated. Suspected flares are listed in Table II. Exceptionally good weather conditions during a 12-night period allowed observations capable of detecting flares of 0.1 magnitude in blue for more than 90 hours, which represents optical coverage of the star for one-third of that total day-and-night period. Simultaneous photographic confirmation of the major flare of July 15 was obtained with the aid of a telephone link to the 36/42/62 cm Hamburg Schmidt telescope at Boyden. Information on simultaneous radio events is not yet available.

NINE FLARES OF YZ CANIS MINORIS

The flare star YZ Canis Minoris (Ross 882, a = 7*42*9, 8 = +3°39', vis. mag. 11.6, dM4.5e) was monitored at the Boyden Observatory from January 25 until March 20, 1966, during which period nine flares were recorded. The 16-inch Nishimura reflector and photometer, equipped with an E.M.I. 6256 photomultiplier and standard UBV filters, was employed. The technique used was to continuously monitor the star in blue (B), and approximately each half hour to take measures also in yellow (V) and ultraviolet ( (7), together with their sky. The smallest flare detectable by us would have an amplitude in blue of about 0.1 magnitude. In the event of activity, the maximum phase was followed using whichever filter was set, and during the gradual decline the other color measures were attempted. The intensity of a flare was then expressed in terms of the normal intensity of the star, taking this as the mean relative intensity before and after the flare. While this technique introduces a small discrepancy in the comparison of one flare with another, it ensures the greatest coverage of the star. Roques ( 1961 ) , in fact, found no longterm irregularities in the star greater than about 0.05 mag., except near one major flare of 2.44 mag. when the variations amounted to only 0.2 mag. The coverage over 54 nights and the observed flares with their magnitude range in blue and the total duration over which the flare was active are given in Table I. Light curves in blue are shown in Figure 1, where the ordinate is the excess intensity of the flare expressed in terms of the normal intensity of the star, and the abscissa is the time in minutes. We note that, apart from the flare continuum, the observed blue flare may contain possible variations in the early Balmer emission lines, except Ha. The nine flares together illustrate well the characteristics of previously observed flares, namely, the pre-flare phenomenon, the flash phase and rapid decline, the secondary maximum or stillstand,

A spectral survey of southern Milky Way regions

A great spectral survey of the southern Milky Way, initially planned by B. Lindblad, is being carried out at the Stockholm Observatory since 1956. The observations have been performed at the Boyden Observatory in South Africa. The purpose of the investigation is in the first instance an extension and a completing of present lists of high-luminosity stars, stars of rare spectral types, galactic clusters, associations, and nebulae for the southern hemisphere. Within the framework of the principal project a series of partial investigations are to be performed. To a large extent the present programme will also constitute a preparation for continued work at the European Southern Observatory in Chile.

A photometric and spectrophotometric investigation of the central parts of the Norma Cloud

The author has for some time at the Stockholm Observatory been occupied in a photometric and spectrophotometric investigation of the central parts of the Norma Cloud of stars (α = 16h19m5, δ = −52°). The plate material has been collected at the Boyden Observatory: the spectral plates have been secured with the ADH telescope combined with objective prism, the photometric plates with the ADH and the 10-inch Metcalf telescopes. The photographic magnitudes and the colour indices are referred to the photometric system of the E-regions, as established by the Cape Observatory.

Clobular clusters of the Large Magellanic Cloud.

view Abstract Citations (1) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Clobular clusters of the Large Magellanic Cloud. Hodge, Paul W. Abstract Globular clusters of the Large Magellanic Cloud have been identified on plates taken with the ADH Baker-Schmidt telescope of the Boyden Observatory. The series of plates employed emulsion and filter combinations that correspond to B and V colors. Twenty plates in each color cover the Cloud, giving a total surveyed area of 100 by 12.50. The plates were exposed to a uniform limiting magnitude of about 18.5. The correcting plate was diaphragmed to eliminate vignetting. There are about 70 objects on the plates which, in their general appearance, resemble globular clusters. Not all can be true globulars, however; some have early-type spectra and blue integrated colors. The present work involved the investigation of colors and magnitudes of the brightest stars in each cluster. The color- magnitude diagrams for the brightest stars of 35 objects show them to be globular clusters similar to those of our galaxy. They have widely differing sizes, integrated brightnesses, and degrees of concentration. The remaining clusters have stars on the main sequence as well as in the giant region. Their color-magnitude diagrams appear to be similar, within the accuracies of the photometry, to those of open clusters in our galaxy. The most notable difference is the very great total number of stars. A number of these pseudo-globular clusters contain what appear to be ordinary classical Cepheid variables. In clusters containing more than one variable, the periods of the Cepheids are nearly equal. Periods are directly related to the magnitudes of the brightest stars in the cluster in the sense that the shorter periods are found in the clusters with the fainter stars. Harvard College Observatory Cambridge, Mass. Publication: The Astronomical Journal Pub Date: October 1959 DOI: 10.1086/107943 Bibcode: 1959AJ.....64..335H full text sources ADS |