Showing papers in "Publications of the Astronomical Society of the Pacific in 1976"
TL;DR: In this paper, a four-color UVGR intermediate-band photometric system was developed to avoid several pitfalls of the standard UBV system, which is essentially nonoverlapping and is designed to exclude the strongest night-sky lines at most sites.
Abstract: A four-color UVGR intermediate-band photometric system is discussed which was developed to avoid several pitfalls of the standard UBV system. The bands are essentially nonoverlapping and are designed to exclude the strongest night-sky lines at most sites. The ultraviolet band (u) is not open at the short-wavelength end, is narrow enough that second-order extinction coefficients are not necessary, and its response is entirely shortward of the Balmer jump, making the (u-v) color index a sensitive measure of the Balmer discontinuity. The filters employed are described, the magnitude and extinction equations are given, and a list of standard stars defining the photometric system is provided. It is noted that the characteristics of the present system should make it far more powerful than the UBV system for the study of stellar temperatures, gravities in early-type stars, and metallicity in middle to late-type stars.
166 citations
TL;DR: In this article, the UBV, uvby, and Geneva photometric systems were combined with filter transmission curves and several different laws of interstellar absorption to obtain reddening relations.
Abstract: Stellar energy fluxes for various spectral types have been combined with filter transmission curves and several different laws of interstellar absorption to obtain reddening relations and the ratio of total-toselective absorption for the UBV, uvby, and Geneva photometric systems. The results are compatible with observations. Effects due to the bandwidths of the various systems on the reddening slopes, curvature of the reddening line, and the ratio of total-to-selective absorption have to be allowed for in wide-band photometry. Key words: interstellar reddening - photometric systems
105 citations
TL;DR: In this article, the progression of the strength of discrete spectral features due to gaseous molecules in the stellar atmospheres as well as those features attributable to circumstellar grains is illustrated and discussed.
Abstract: Infrared spectrophotometry with resolution A/A 0.015 over the wavelength range 2-14 m is presented for a wide variety of stars of the conventional spectral sequence. The progression of the strength of discrete spectral features due to gaseous molecules in the stellar atmospheres as well as those features attributable to circumstellar grains is illustrated and discussed. Key words: late-type stars - carbon stars - molecular spectra - infrared spectrophotometry
59 citations
TL;DR: In this paper, the authors discuss some questions about Fourier transforms, how they enter into quantitative spectrum analysis, and how they can be applied to learn more about stars, and demonstrate typical applications to stellar rotation, macro-and microturbulence, stellar magnetic fields, and velocity distributions in globular clusters and galaxies.
Abstract: The paper discusses some questions about Fourier transforms, how they enter into quantitative spectrum analysis, and how they can be applied to learn more about stars. Physical processes that are better analyzed in terms of Fourier transforms rather than line profiles, and vice versa, are identified; advantages of Fourier analysis are enumerated; and the analysis technique is outlined. The use of Fourier transforms is demonstrated by summarizing typical applications to stellar rotation, macro- and microturbulence, stellar magnetic fields, and velocity distributions in globular clusters and galaxies. Observational techniques that should be employed to obtain the best results from a Fourier analysis are considered along with some basic limitations of the Fourier approach.
50 citations
TL;DR: In this paper, a uniform two-dimensional spectral type for 575 stars, most of which are F stars, was presented, and only a few peculiar spectra, other than composites, were found although care was taken to note stars with unusually strong or weak metal characteristics.
Abstract: New uniform two-dimensional spectral types are presented for 575 stars, most of which are F stars. Only a few peculiar spectra, other than composites, were found although care was taken to note stars with unusually strong or weak metal characteristics. Key words: spectral classification - F-type stars
47 citations
TL;DR: In this paper, the authors presented new MK classifications (51 stars) and UBV magnitudes (37 stars) for stars in the region of the cluster Trumpler 37, which is the nucleus of the association I Cephei (Cep OB 2).
Abstract: New MK classifications (51 stars) and UBV magnitudes (37 stars) are presented for stars in the region of the cluster Trumpler 37, which is the nucleus of the association I Cephei (Cep OB 2). These are com bined with additional UBV magnitudes from Simonson (1968) and compared with the H-R diagram of upper Scorpius to derive a distance modulus of . The relationship of the supergiant Cep to the rest of the association is discussed and an absolute magnitude of -7.7 is derived if it is assumed to be a member. Key words: UBV photometry - MK spectral classification - clusters - associations
46 citations
TL;DR: In this article, the stellar abundances of Li, Be, and B that are relevant to the origin of these light elements and to details of stellar structure are discussed. But the authors focus on the stellar abundance of Li and Be.
Abstract: The present review is concerned with the stellar abundances of Li, Be, and B that are relevant to the origin of these light elements and to details of stellar structure. It is proposed that the best values for the cosmic abundances of these elements can be derived from abundance determinations in stellar atmospheres. The observed abundances are taken to indicate origins in spallation reactions involving galactic cosmic rays, with additional Li-7 probably produced during the big bang. Evidence is presented showing that the Li abundance with which stars are born is depleted during pre-main-sequence evolution, that atoms of the light elements are transported to regions within a star where they are destroyed by (p, alpha) reactions, and that many normal stars have large deficiencies of Li and Be. Overabundances and dilutions of the three elements in Ap stars, supergiants, and giants are discussed along with mechanisms that could account for both super-Li-rich stars and the great range of Li abundances in C and S stars
43 citations
TL;DR: In this article, a catalog of the important optical data for the radio sources in the Revised Third Cambridge Catalog is presented, including positions, redshifts, magnitudes, and identifications, as well as radio flux densities and spectral indices.
Abstract: We present a catalog of the important optical data for the radio sources in the Revised Third Cambridge Catalog. Optical positions, redshifts, magnitudes, and identifications have been included, as well as radio flux densities and spectral indices for the sample of 297 extragalactic 3CR sources. A bibliography of optical identifications, spectroscopy, and radio position/structure is also given. In addition to the literature compilation, we present new spectroscopic observations of 27 3CR radio galaxies, 25 of which do not have previously published redshifts.
43 citations
TL;DR: In this paper, a large number of 2 m Sky Suwey objects were used for infrared photometry and spectrophotometry with resolution 4A -0.015 over the wavelength range 2.
Abstract: Broad-band infrared photometry and spectrophotometry with resolution 4A --0.015 over the wavelength range 2- is presented for a large number of 2 m Sky Suwey objects. All of these sources within the present sample except IRC +40091 (Lk Ha 101) are shown to have characteristics similar to stars of the conventional spectral sequence or perhaps a slight extension to cooler surface temperature. A progression of increasing optical depth of circumstellar dust surrounding the stars is demonstrated. No evidence for a cool stellar photosphere is observed for IRC +40091. Key words: infrared objects - infrared spectrophotometry - circumstellar dust
39 citations
Journal Article•
38 citations
TL;DR: In this article, a set of glass filters is described which, when used with a Ga-As photomultiplier, enables very satisfactory transformations to be made from instrumental UBVRI measures to existing VRI photometric systems.
Abstract: A set of glass filters is described which, when used with a Ga-As photomultiplier, enables very satisfactory transformations to be made from instrumental UBVRI measures to existing UBV and VRI photometric systems. The construction of a liquid copper sulfate cell employed to prevent the red leak in UV filters is outlined, and the relative merits of different types of glass are discussed. It is concluded that the increased sensitivity of the infrared system makes it very attractive for observations of globular-cluster stars and faint cool field stars, although the situation for infrared standard stars still requires improvement.
TL;DR: The Perek-Kohoutek planetary-nebula catalogue was searched for coincidences with the Kukarkin et al. variable-star catalogue as discussed by the authors, and the majority of the coincidences are with late-type variable stars erroneously listed as planetary nebulae.
Abstract: The Perek-Kohoutek planetary-nebula catalogue was searched for coincidences with the Kukarkin et al. variable-star catalogue. Twenty-six objects appear in both catalogues, but only one, the eclipsing binarv UU Sge, appears to be a genuine new variable planetary-nebula central star. The majority of the coincidences are with late-type variable stars erroneously listed as planetary nebulae. Key words: eclipsing binaries - planetary nebulae - symbiotic variables - variable stars
TL;DR: The spectral types of 26 of the brightest cluster members show (1) nine stars with broad hydrogen-line cores, (2) two Am stars, of which one is in the region of the pre-main-sequence stars, (3) two stars with weak K lines similar to ones found in NGC 6475 and M 39, (4) three shell stars, and (5) two composite spectra, and no evolved (luminosity class IV or brighter) stars or Ap stars.
Abstract: MK spectral types of 26 of the brightest cluster members show (1) nine stars with broad hydrogen-line cores, (2) two Am stars, of which one is in the region of the pre-main-sequence stars, (3) two stars with weak K lines similar to ones found in NGC 6475 and M 39, (4) three shell stars, of which one has hydrogen emission, (5) two composite spectra, and (6) no evolved (luminosity class IV or brighter) stars or Ap stars. Key words: open clusters - spectral classification
TL;DR: In this article, the authors systematically examined orbital elements of spectroscopic binaries to provide lists of systems which might profitably be observed by astrometric and speckle interferometric techniques.
Abstract: Published orbital elements of spectroscopic binaries are systematically examined to provide lists of systems which might profitably be observed by astrometric and speckle interferometric techniques. The importance of observing these spectroscopic systems with other techniques is emphasized. Consideration is given to image-blending effects on astrometric amplitude predictions. Angular separation predictions for single-lined systems use a mass-luminosity relation to approximately account for the semimajor axis of the unseen component. The interferometric possibilities are found to be large with some 73 systems possibly resolvable with a 5-meter telescope. A 2-meter telescope could possibly resolve 29 systems. The astrometric candidates are more limited with perhaps ten systems suitable for study. Key words: spectroscopic binaries - astrometric binaries - speckle interferometry
TL;DR: In this paper, the authors show that the Am star 8 Nor has a magnetic field strength of about -2200 gauss and no evidence of magnetic or spectrum variability, which is the strongest known magnetic field for a star.
Abstract: Zeeman spectroscopic observations show that HD 101065 (Przybylski's star) has a magnetic field strength of about -2200 gauss. The limited observations available show no evidence of magnetic or spectrum variability. Observations of the Am star 8 Nor were made in order to determine whether systematic errors were present in the determination of He, and these data yield an upper limit of 150 gauss for the field of 8 Nor. Key words: peculiar A star - magnetic fields - rare-earth elements
TL;DR: The average color indices (B- V) = + and (U- B) =+ and short period (F = 0d2207) place this system at the lower temperature end of the period-color relation for the W UMa-type binaries as discussed by the authors.
Abstract: The average color indices (B- V) = + and (U- B) = + and short period (F = 0d2207) place this system at the lower temperature end of the period-color relation for the W UMa-type binaries. During minima the indices change to (B- V) = + 1'P29 and (U- B) = + 100; however, the (U- B) index reveals rather large scatter and was also observed to decrease abnormally to (U - B) = + 0' '93 during one primary minimum. It is unclear whether these abnormal variations in (U- B) are related to an ultraviolet excess of about + 0.1 (unfortunately no red-leak corrections were applied) although some support for that can be found in the fragmentary uvhy photometry. Small night-to-night changes might be present in the V-light curve as well. The large amplitude of light variation (0.85 and 0.75 magnitude in V) and the presence of a total eclipse with semiduration of totality of about 8 permit one to determine the geometrical elements with rather high accuracy, in spite of relatively large photometric errors due to the faintness of the system (+ 11.3 V + 12.2). CC Com belongs to the W-type systems, with a relative temperature excess of the secondary component X = 0.051 :::: 0.002. Other elements are: i = 900 ::::: 02, (1 = 0.521 l 0.004,f = 0.765 j 0.013 for the assumed Te = 4300 K. The membership of CC Com in the Coma Cluster (Mel 111) is discussed and shown to be very likely, but its acceptance must await further proper-motion studies. The individual times of minimum light of CC Com, and the new ephemeris, are given. Key words: light-curve synthesis - contact binaries
TL;DR: In this paper, the residuals for all published times of minimum light using three different least squares procedures were calculated for AR Lac, and good agreement was found between the observed light curves and the theoretical light curves for primary minimum, but the agreement was poor for secondary minimum.
Abstract: AR Lac was observed on 22 nights during the autumns of 1972, 1973, and 1974. Totals of 650-700 observations each were obtained in yellow, blue, and ultraviolet. The period of AR Lac, which is 1d9832, has undergone substantial changes during the past 40 years. Residuals are calculated for all published times of minimum light using three different least squares procedures. The light curves of AR Lac indicate that the intrinsic variation has a total amplitude of about . The eclipses are complete, the primary being an occultation. The primary minimum displays less scatter than does the secondary minimum, and this is consistent with the hypothesis that the intrinsic variation arises chiefly from star A. Star B may well be nonvariable. Photometric elements are obtained using the method of Russell and Merrill. Good agreement was found between the observed light curves and the theoretical light curves for primary minimum, but the agreement was poor for secondary minimum. Orbital eccentricity is considered, but it is found to be very small, if present at all. Radii of 1.54 R0 and 2.81 R0 are obtained for star A and star B, respectively. The masses of the components are nearly identical. Their effective temperatures are estimated to be 5600 K and 4700 K, respectively, and these are in agreement with their spectral types of G2 IV and KO IV. AR Lac is one of very few eclipsing binaries which have been observed to show pronounced flare activity at radio wavelengths. The radio outbursts do not appear to be correlated with phase or with instabilities in the light curves at optical wavelengths. Key words - eclipsing binaries - intrinsic variables - subgiants - radio sources
TL;DR: In this paper, the authors presented a broadband photometry and spectrophotometry with resolution xlx 0.015 over the wavelength range 2-14 m for a sample of sources in the AFCRL Infrared Sky Survey.
Abstract: Broad-band photometry and spectrophotometry with resolution xlx 0.015 over the wavelength range 2-14 m is presented for a sample of sources in the AFCRL Infrared Sky Survey. Some of the objects discovered in this survey are shown to be stars of the conventional spectral sequence surrounded by optically thick circumstellar dust shells. Others exhibit no evidence of classical cool stellar objects and may represent various transition stages of stellar evolution. Key words: infrared objects - spectrophotometry - cool stars - circumstellar dust
TL;DR: In this paper, a multichannel detector system is described in which the positions of individual photon events in a high-gain image intensifier are decoded in the output of a video detector.
Abstract: A multichannel detector system is described in which the positions of individual photon events in a high-gain image intensifier are decoded in the output of a video detector. The high-gain intensifier consists of a pair of three-stage electrostatic image-tube assemblies each containing three fiber-optically-coupled tubes potted in a rugged package with an internal high-voltage supply. Operation of the electrooptical system is discussed along with the pulse-detection process and the operation of the spectrograph in which the image-tube assembly is mounted. It is noted that the spectrometer detects 1.0 count/sec per A for an object of magnitude 13.0 at the peak of its response in the visual band when no light is lost on the slit, that a 10% coincidence correction is reached at an overall count rate of 860 per sec, and that the response follows an exponential law up to count rates of about 4000 per sec. The measured spectrum of the Seyfert galaxy NGC 5548 is provided as an example of the raw data produced by the instrument on a 1.5 meter telescope.
TL;DR: In this article, a program has been undertaken to obtain a complete sample of bright quasars on the basis of ultraviolet color excess, and the results suggest that bright quasar has a low surface density.
Abstract: A program has been undertaken to obtain a complete sample of bright quasars on the basis of ultraviolet color excess. Spectroscopic examination of candidates selected from two-color Schmidt telescope films has yielded four new quasars brighter than B = 16.5 mag, with the candidate list containing two more previously identified. Magnitudes, color indices, and redshifts are presented for the new discoveries, along with positions and finding charts. Although the sample is not yet complete, these first results suggest that bright quasars have a low surface density.
TL;DR: The Anglo-Australian Telescope (AAT) is one of the few optical telescopes that has full computer control - not only of differential motions (offsetting, scanning, etc.) but also of the more basic operations (slewing, and corrected pointing and tracking).
Abstract: The Anglo-Australian Telescope (AAT) is one of the few optical telescopes that has full computer control - not only of differential motions (offsetting, scanning, etc.) but also of the more basic operations (slewing, and corrected pointing and tracking). Brief attention is given to the actual hardware, while central consideration is given to a description of the telescope control system as a whole. The various tasks of the control software are described in detail, these tasks being of both the synchronous and asynchronous type. The steps involved in slewing and tracking are described.
TL;DR: Recently obtained spectrograms imply that RY Sct contains two massive stars embedded in an unusual nebulosity whose spectrum shows exceptionally strong (forbidden Fe III) emission as mentioned in this paper, which may result from the loss of the H-rich envelope.
Abstract: Recently obtained spectrograms imply that RY Sct contains two massive stars embedded in an unusual nebulosity whose spectrum shows exceptionally strong (forbidden Fe III) emission. At least one component is probably H-deficient (or He-rich), which may result from the loss of the H-rich envelope. Rapid rotation is thought to be the cause of this. A modern light curve is required before a complete interpretation of the data can be made.
TL;DR: In this paper, a light-curve-synthesis program was used to determine the geometrical elements of SV Cen by simultaneous differential-correction fitting of the three-color light curves obtained in UBV by Irwin and Landolt (1972).
Abstract: A light-curve-synthesis program which implements interpolation in a grid of nongray model atmospheres has been used to determine the geometrical elements of SV Cen by simultaneous differentialcorrection fitting of the three-color light curves obtained in UBV by Irwin and Landolt (1972). Solutions with the mass ratio fixed at its spectroscopic value of 0.84 reveal an extraordinarily high degree of contact between the components (fill-out parameter f = 0.10 ::::: 0.02) and a rather high temperature of the less massive component relative to the more massive component. The large local temperature excess of the secondary star, X = A TIT = 0.78 :::: 0.03 (which results in temperatures 28,000 and 17,0000 K, for the less massive and more massive compounds, respectively) is difficult to understand in the framework of the contact model but might be related to the thermal-time-scale mass-transfer stage of the evolution of SV Cen. Key words: light-curve synthesis - mass transfer
TL;DR: In this article, new radial velocities for 35 galaxies in the fields of the Pegasus I and Pegasus II clusters were presented for 35 background galaxies with apparent photographic magnitude brighter than 15" 6.
Abstract: New radial velocities are presented for 35 galaxies in the fields of the Pegasus I and Pegasus II clusters. Many background galaxies with apparent photographic magnitude brighter than 15" 6 are found to be superimposed upon the Pegasus I cluster. Galaxies with radial velocities near the average for the Pegasus II cluster are detected well outside the boundary of the cluster as defined in the Catalogue of Galaxies and Clusters of Galaxies by Zwicky et al. This suggests that the Pegasus II cluster is part of a large cloud of galaxies. Key words: clusters of galaxies - radial velocities
TL;DR: Montages of red and blue image-tube spectra for 21 different supernova remnants located in the southern Milky Way and in the Magellanic Clouds are presented in this article, and some new emission lines are tentatively identified.
Abstract: Montages of red and blue image-tube spectra are presented for 21 different supernova remnants located in the southern Milky Way and in the Magellanic Clouds. Particular spectral characteristics are described for each remnant and some new emission lines are tentatively identified. Attention is drawn to the apparently radio-quiet objects N70 and N185 in the LMC, and a case is made for their being supernova remnants.
TL;DR: In this paper, a simple treatment of gravity and limb darkening shows that measured V sin i values for OB stars are significantly lower for rapid rotators in the far ultraviolet than in the photographic region of the spectrum.
Abstract: A simple treatment of gravity and limb darkening shows that measured V sin i values for OB stars are significantly lower for rapid rotators in the far ultraviolet than in the photographic region of the spectrum. This circumstance should help in determining V, i, WlWcrit, and gravity darkening for these stars. Key words: stellar rotation - line profiles
TL;DR: The 9.2-year spectroscopic orbit of the quintuple system Ori is resolved by means of speckle interferometry with the 4-meter Mayall tdescope as mentioned in this paper.
Abstract: The 9.2-year spectroscopic orbit of the quintuple system Ori is resolved by means of speckle interferometry with the 4-meter Mayall tdescope. The value of the angular separation is combined with the spectroscopic results of Zizka and Beardsley (1976) to determine the location on the empirical massluminosity diagram for the early-type spectroscopic components. Assuming the orbits of the spectroscopic systems to be coplanar, the uncertainty of the inclination is eliminated since the short-period system is known to be eclipsing. The most massive component is 16.7 j 0.6 solar masses with Mv = -4.0 + 0.3. The total mass of the system is probably well over 50 solar masses. Key words: spectroscopic binaries - speckle interferometry - mass-luminosity relation
TL;DR: In this article, the spectral appearance of Gamma Cas has been analyzed and it is concluded that Gamma Cas is probably a single star, although the possible existence of a low-mass companion cannot be ruled out.
Abstract: Qualitative changes in the spectral appearance of Gamma Cas since 1941 are presented. Velocity variations are searched for to aid in the interpretation of the recently discovered X-ray flux. No evidence is found for velocity variations exceeding 20 km/s, and no periodicities in the range from 2.5 to 4000 days are detected. It is concluded that Gamma Cas is probably a single star, although the possible existence of a low-mass companion cannot be ruled out.
TL;DR: Optical spectrophotometry is presented in this article for 13 optically identified rocket infrared sources, seven are cool giants, some suffering appreciable circumstellar visual extinction; four are carbon stars; one is a Wolf-Rayet system; and another is unlikely to be the appropriate infrared source.
Abstract: Optical spectrophotometry is presented for 13 optically identified rocket infrared sources. Seven are cool giants, some suffering appreciable circumstellar visual extinction; four are carbon stars; one is a Wolf-Rayet system; and another is unlikely to be the appropriate infrared source.
TL;DR: In this article, the spatial distribution of optical spiral tracers and their motions in the region of the galactic plane from 1 = 280 to 340 deg were studied and a model of the optical spiral pattern was proposed which adequately describes the available spatial and kinematic information for the spiral tracer.
Abstract: Spatial distributions of optical spiral tracers and their motions in the region of the galactic plane from 1 = 280 to 340 deg are studied. When this region is related to the entire pattern of local spiral structure a major spiral arm, Sagittarius-Carina, is revealed from 1 = 280 to 30 deg. A model of the optical spiral pattern is proposed which adequately describes the available spatial and kinematic information for the spiral tracers.