Stellar Spectrophotometry Research Articles

H0534 - 581: A new intermediate polar?

view Abstract Citations (23) References (47) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS H0534-581: A New Intermediate Polar? Buckley, D. A. H. ; Tuohy, I. R. Abstract Optical spectroscopic and photometric observations of the hard X-ray-emitting HEAO 1 cataclysmic variable, H0534 - 581 are discussed. From the analysis of Exosat time series data, spectroscopic periods at 6 and 2.1 hr are identified as the orbital and white dwarf spin periods, respectively. The results suggest that H0534 - 581 is a member of the intermediate polar (DQ Herculis) class of magnetic cataclysmic variables. Publication: The Astrophysical Journal Pub Date: January 1990 DOI: 10.1086/168314 Bibcode: 1990ApJ...349..296B Keywords: Cataclysmic Variables; Magnetic Stars; Stellar Spectrophotometry; White Dwarf Stars; X Ray Binaries; Angular Velocity; Emission Spectra; Light (Visible Radiation); Line Spectra; Astrophysics; STARS: BINARIES; STARS: DWARF NOVAE; STARS: INDIVIDUAL ALPHANUMERIC: H0534-581; STARS: MAGNETIC; X-RAYS: BINARIES full text sources ADS | data products SIMBAD (12)

Evolutionary population synthesis in stellar systems. I - A global approach

view Abstract Citations (248) References (100) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Evolutionary Population Synthesis in Stellar Systems. I. A Global Approach Buzzoni, Alberto Abstract A new grid of 450 theoretical models for old simple stellar populations is presented. Evolutionary synthesis explores the influence of relevant parameters such as age, chemical composition, initial mass function, and stellar mass loss, on the integrated spectral energy distribution. Ages range between 4 and 18 Gyr, and the metallicity Z ranges from 0.0001 to 0.03, with helium content Y = 0.23 and 0.25, respectively. Three values are considered for the initial mass function, assumed as a power law, N(M) proportional to M exp-s; s = 1.35, 2.35, and 3.35. The computational code takes into account in a quantitative way the contributions from all the relevant stellar evolutionary phases according to the theory of the stellar evolution. Thus, late stage in the life of low- mass stars, such as the horizontal branch and the asymptotic and postasymptotic giant branches are accounted for. Furthermore, a simplified treatment for the evolution of the horizontal branch is developed, and the influence of different morphologies are investigated. Publication: The Astrophysical Journal Supplement Series Pub Date: December 1989 DOI: 10.1086/191399 Bibcode: 1989ApJS...71..817B Keywords: Late Stars; Stellar Evolution; Stellar Models; Stellar Spectrophotometry; Stellar Systems; Asymptotic Giant Branch Stars; Horizontal Branch Stars; Red Giant Stars; Stellar Magnitude; Stellar Structure; Astrophysics; GALAXIES: STELLAR CONTENT; STARS: EVOLUTION full text sources ADS | Related Materials (1) Part 2: 1995ApJS...98...69B

Relative abundance determinations in extremely metal poor giants. I - Photometry and equivalent width measurements

view Abstract Citations (21) References (43) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Relative Abundance Determinations in Extremely Metal-poor Giants. I. Photometry and Equivalent Width Measurements Peterson, Ruth C. ; Carney, Bruce W. Abstract Photometry and measurements of equivalent widths are presented for nine extremely metal-poor stars, including two in the globular cluster M92. Reddening estimates are evaluated in depth. An extensive intercomparison is presented of equivalent widths derived here and by various other authors for the same stars. With the echelle spectrograph, long-focus camera, and TEK CCD data, widths from 2 to 20 mA are measured to + or - 2 mA for a star with V = 6, and widths from 12 to 50 mA are measured to + or - 10 mA for a star with V = 12. Photographic image-tube echelle data produced widths good to + or - 10 mA over 10-100 mA from two plates. It is shown that the nickel overabundance deduced for the most extremely metal poor stars by Luck and Bond (1985) may arise from their overestimate of equivalent widths of weak lines at the limit of detectability. Publication: The Astrophysical Journal Pub Date: December 1989 DOI: 10.1086/168115 Bibcode: 1989ApJ...347..266P Keywords: Abundance; Astronomical Photometry; Giant Stars; Stellar Spectra; Stellar Spectrophotometry; Echelle Gratings; Globular Clusters; Interstellar Extinction; Metallicity; Astrophysics; CLUSTERS: GLOBULAR; STARS: ABUNDANCES; STARS: LATE-TYPE; STARS: POPULATION II full text sources ADS | data products SIMBAD (9) Related Materials (1) Part 2: 1990ApJ...350..173P

A spectroscopic study of Nova Centauri 1986

view Abstract Citations (12) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Spectroscopic Study of Nova Centauri 1986 de Freitas Pacheco, J. A. ; dell'Aglio Dias da Costa, R. ; Codina, S. J. Abstract Extensive spectroscopic observations of Nova Cen 1986 obtained at different evolutionary phases of the event are reported. A reddening E(B-V) = 0.54 mag and a distance of 1.4 + or - 0.2 kpc are derived for the nova. The physical conditions and ionic abundances in the ejecta are also estimated. Helium, nitrogen, and oxygen are overabundant with respect to the solar values, but iron is normal. The expansion velocity is about 1400 km/s, and the total ejected mass is about 0.00003 solar mass. Publication: The Astrophysical Journal Pub Date: December 1989 DOI: 10.1086/168137 Bibcode: 1989ApJ...347..483D Keywords: Abundance; Novae; Stellar Composition; Stellar Mass Ejection; Stellar Spectrophotometry; Cassegrain Optics; H Alpha Line; Astrophysics full text sources ADS | data products SIMBAD (1)

HR Aurigae - an active binary?

view Abstract Citations (2) References (11) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS HR Aurigae: an Active Binary? Loomis, Charles G. ; Schmidt, Edward G. Abstract Photometric and spectral observations of the variable star HR Aurigae are presented. The light curve, strong hydrogen emission, and velocity are inconsistent with the star being a type II Cepheid. It is concluded that HR Aur is in fact an active binary. Publication: The Astrophysical Journal Pub Date: December 1989 DOI: 10.1086/185612 Bibcode: 1989ApJ...347L..77L Keywords: Eclipsing Binary Stars; Stellar Activity; Stellar Spectrophotometry; Variable Stars; Hydrogen; Light Curve; Stellar Magnitude; Stellar Rotation; Astrophysics; STARS: ECLIPSING BINARIES; STARS: VARIABLES full text sources ADS | data products SIMBAD (2)

Radial velocities in 12 Algol binaries

view Abstract Citations (57) References (65) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Radial Velocities in 12 Algol Binaries Popper, Daniel M. Abstract Radial velocities derived from photometric analysis of the Na D lines for the cooler components of the 12 Algol systems are discussed. The number of velocities per system at the D lines ranges from 6 to 63, and in each case, the velocities are well represented by circular motion. For a 5-day period, the spectra of the primaries in RY Aqr, TW Dra, TW And, and RS Vul appear to be completely photospheric, while the other eight systems, Rx Gem, Ry Gem, AD Her, TT Hya, Au Mon, RW Per, RY Per, and XY Pup, show double H-alpha emission and other evidence of nonphotospheric material in the hotter spectra. For most of these systems of longer period, the velocities are quite well represented by pseudoelliptical motion, with minimum velocities and maximum departures from circular motion near phase 0.4, measured from primary minimum. Provisional masses are given for the stars based on the available spectroscopic and photometric evidence, much of it of low weight. The companions of the primaries with A-type spectra have masses of 0.75 solar mass or less, and temperatures or types in the early K range as observed in RY Aqr. All the secondaries are larger than main-sequence stars of the corresponding types. Publication: The Astrophysical Journal Supplement Series Pub Date: November 1989 DOI: 10.1086/191388 Bibcode: 1989ApJS...71..595P Keywords: Eclipsing Binary Stars; Radial Velocity; Stellar Motions; Stellar Spectrophotometry; Balmer Series; Line Spectra; Photosphere; Stellar Atmospheres; Stellar Spectra; Stellar Temperature; Astrophysics; RADIAL VELOCITIES; STARS: ECLIPSING BINARIES full text sources ADS | data products SIMBAD (13)

Hard emission at late times from SN 1987A

view Abstract Citations (176) References (55) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Hard Emission at Late Times from SN 1987A Woosley, S. E. ; Pinto, Philip A. ; Hartmann, Dieter Abstract Using a model for the explosion that has been remarkably successful in predicting and explaining the evolution of SN 1987A during its first one and one-half years we calculate the future photometric evolution of the supernova in the UV-optical-IR, X-ray, and γ-ray bands using Monte Carlo techniques. Special attention is given to the contribution from radioactive isotopes other than ^56^Co, notably ^57^Co, ^44^Ti, and ^22^Na, and to the possible appearance, probably within the next year, of X-rays from an accreting magnetic neutron star at the center of the supernova. The signature of a radio pulsar like the Crab is also considered. In both cases the time history of the bolometric light curve may be a more sensitive diagnostic than the existence of either pulses or hard emission, but will become confused in the near future by contributions from the rare radioactivities. A source as faint as the pulsed emission of the Crab pulsar will never be discernable in the bolometric light curve. Pulsed hard emission is best sought near 30 keV near the end of 1989 (and thereafter), although more sensitive instrumentation than hitherto employed may be necessary. Publication: The Astrophysical Journal Pub Date: November 1989 DOI: 10.1086/168019 Bibcode: 1989ApJ...346..395W Keywords: Astronomical Models; Light Curve; Stellar Composition; Stellar Spectrophotometry; Supernova 1987a; Computational Astrophysics; Monte Carlo Method; Neutron Stars; Pulsars; X Ray Sources; Astrophysics; GAMMA RAYS: GENERAL; PULSARS; STARS: INDIVIDUAL ALPHANUMERIC: SN 1987A; STARS: SUPERNOVAE; STARS: X-RAYS full text sources ADS | data products SIMBAD (4) NED (2)

Stellar content of nearby galaxies. II - The Local Group dwarf elliptical galaxy M32

view Abstract Citations (99) References (36) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Stellar Content of Nearby Galaxies. II. The Local Group Dwarf Elliptical Galaxy M32 Freedman, Wendy L. Abstract A field in the elliptical galaxy M32 has been resolved into stars using the prime-focus CCD camera on the Canada-France-Hawaii telescope. From these observations color-magnitude diagrams have been obtained for the brightest stars in this high-surface-brightness companion galaxy to M31. Both the I vs (V - I) and I vs (R - I) CCD color-magnitude diagrams reveal a red population of stars, the brightest of which resolve at I~19.5 mag. A lower limit to the mean metallicity of this stellar population is estimated from the apparent mean (V - I) and (R - I) colors at the giant branch tip. For the available data, this method indicates that the mean metallicity is greater than that of the most metal-rich Galactic globular clusters, that is (M/H) > -0.5 dex. The dispersion in the (V - I) and (R - I) colors exceeds that due to the estimated photometric errors, probably indicating an intrinsic range in the metallicity of the population amounting to 0.6 dex. The observed numbers of stars bracketing the tip of the first red giant branch can, in principle, provide a constraint on the age of the observed population. The histogram Iband luminosity function shows two discontinuities and allows two possible interpretations. If the bright discontinuity seen at I = 20.15 +/- 0.10 mag is interpreted as the tip of the first red giant branch, it suggests that M32 is approximately 100 kpc closer than M31, and that the age of most of the M32 stars is comparable to those in Galactic globular clusters. This result is consistent with other determinations of the relative distances of M31 and M32. Alternatively, if the fainter discontinuity at I = 20.45 +/- 0.10 mag is interpreted as being the first red giant branch tip, this suggests that M32 is at a distance comparable to M31. In this case, the relative numbers of stars above and below the adopted red giant branch tip suggests that a significant population of asymptotic giant branch stars may be present which could have formed as recently as 5 Gyr ago. This interpretation is consistent with spectroscopic studies and population synthesis models of the nucleus of M32. An independent distance modulus estimate for M32 is needed to provide a means of discriminating between these two very different alternatives. Publication: The Astronomical Journal Pub Date: October 1989 DOI: 10.1086/115216 Bibcode: 1989AJ.....98.1285F Keywords: Color-Magnitude Diagram; Dwarf Galaxies; Elliptical Galaxies; Local Group (Astronomy); Stellar Spectrophotometry; Astronomical Catalogs; Background Radiation; Charge Coupled Devices; Stellar Luminosity; Astrophysics; GALAXIES: INDIVIDUAL; GALAXIES: LOCAL GROUP; GALAXIES: STELLAR CONTENT full text sources ADS | data products SIMBAD (5) NED (1) Related Materials (2) Part 1: 1988AJ.....96.1248F Part 3: 1990AJ.....99..149W

The stellar content of NGC 346 - A plethora of O stars in the SMC

view Abstract Citations (233) References (65) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Stellar Content of NGC 346: A Plethora of O Stars in the SMC Massey, Philip ; Parker, Joel W. ; Garmany, Catharine D. Abstract Using CCD UBV photometry and spectroscopy, we have investigated the stellar content of NGC 346, the brightest H II region in the SMC. Spectra of 42 stars confirm that 33 are of O type, of which 11 are of type O6.5 or earlier; this is as many early-type 0 stars as is known in the rest of the SMC. From the spectroscopy and photometry we are able to construct an H-R diagram which is essentially complete down to ~10 M_sun_. We find an initial mass-function slope {GAMMA} = -1.9, similar to that found for massive stars near the Sun and in the LMC: the presence of six stars in the mass range 40-85 M_sun_ suggests that the upper-mass limit of the IMF is also not appreciably lower in the SMC than it is in the Galaxy. Our photometry has identified five probable red supergiants of which one was previously known. These stars, plus two B supergiants, are evolved stars of considerably lower mass (15 M_sun_) than many of the unevolved cluster members. Most of these lower-mass, evolved stars form a spatially distinct subgroup; we believe that NGC 346 thus provides an example of sequential star formation in the SMC. We also have identified a background field population of 5 M_sun_ stars. We find that the ionizing flux from the hot stars is consistent with the previously known Hα nebular luminosity. Finally, we discuss the enigmatic W-R binary HD 5980, which our point-spread-function fitting has identified as a close visual double. Publication: The Astronomical Journal Pub Date: October 1989 DOI: 10.1086/115217 Bibcode: 1989AJ.....98.1305M Keywords: H Ii Regions; Magellanic Clouds; Nebulae; O Stars; Stellar Spectrophotometry; Astronomical Catalogs; Binary Stars; Interstellar Extinction; Ubv Spectra; Wolf-Rayet Stars; Astrophysics; GALAXIES: MAGELLANIC CLOUDS; NEBULAE: HII REGIONS; STARS: EARLY-TYPE; STARS: WOLF-RAYET full text sources ADS | data products SIMBAD (890) NED (82) CDS (1)

The infrared spectrum of TX PISCIUM

view Abstract Citations (32) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Infrared Spectrum of TX PISCIUM Jorgensen, Uffe G. Abstract TX Psc is one of the very few carbon stars for which spectroscopic data for nearly all of the spectrum, from the blue toward the near infrared, can be found in the literature. Here, calculations of the first synthetic spectra are presented that are in agreement with all the major spectral features in the observed spectrum, including the H(-) peak and the 3-micron band. The spectra are calculated on the basis of available observational estimates for the basic stellar parameters, and use ODF, plane-parallel, LTE model atmospheres that include absorption from diatomic molecules and from HCN, C2H2, and C3 in the opacity calculation. Publication: The Astrophysical Journal Pub Date: September 1989 DOI: 10.1086/167857 Bibcode: 1989ApJ...344..901J Keywords: Carbon Stars; Infrared Spectra; Stellar Atmospheres; Stellar Spectrophotometry; Absorptivity; Astronomical Models; Atmospheric Models; Diatomic Molecules; Spectral Bands; Astrophysics; INFRARED: SPECTRA; STARS: ATMOSPHERES; STARS: CARBON; STARS: INDIVIDUAL CONSTELLATION NAME: TX PISCIUM full text sources ADS | data products SIMBAD (1)

The chromosphere of Beta Cassiopeiae

view Abstract Citations (13) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Chromosphere of Beta Cassiopeiae Teays, Terry J. ; Schmidt, Edward G. ; Fracassini, Massimo ; Pasinetti Fracassini, Laura E. Abstract High-resolution, long-wavelength IUE observations and ground-based photometry of the Delta Scuti star Beta Cas is reported. The ground-based observations were used together with previous results of Antonello et al. (1986) to ensure that the IUE observations were correctly phased relative to the photometric variation. Fluxes for the emission core of the Mg II k 2796-A line were obtained from the UV spectra over several cycles in 1986 and 1987. It is found that there is an increase in the emission during part of the cycle, but it occurs near minimum light in contrast to another Delta Scuti star, Rho Pup, and the classical Cepheids (where it occurs near maximum light). The mean level of chromospheric activity is comparable to other early F dwarfs. Publication: The Astrophysical Journal Pub Date: August 1989 DOI: 10.1086/167761 Bibcode: 1989ApJ...343..916T Keywords: Cassiopeia Constellation; Chromosphere; Iue; Stellar Spectrophotometry; Ultraviolet Astronomy; Variable Stars; Dwarf Stars; Early Stars; F Stars; Scutum Constellation; Astrophysics full text sources ADS | data products SIMBAD (3) MAST (1) INES (1)

Southern Milky Way carbon stars - New candidates, JHK photometry, and radial velocities

view Abstract Citations (34) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Southern Milky Way Carbon Stars: New Candidates, JHK Photometry, and Radial Velocities Aaronson, Marc ; Blanco, Victor M. ; Cook, Kem H. ; Schechter, Paul L. Abstract Data are presented for low-latitude southern Milky Way carbon stars. Coordinates and cross identifications are given for carbon stars (67 of which are confirmed new discoveries) in seven fields deemed to be unusually transparent. JHK photometry is presented for 520 stars. Velocities are presented for 393 stars. Improved coordinates are presented for selected stars in Westerlund's catalog. Averaged photometry and velocities are presented for a sample of 336 stars. Publication: The Astrophysical Journal Supplement Series Pub Date: July 1989 DOI: 10.1086/191350 Bibcode: 1989ApJS...70..637A Keywords: Carbon Stars; Milky Way Galaxy; Radial Velocity; Stellar Spectrophotometry; Astronomical Catalogs; Astronomical Coordinates; Astronomy; PHOTOMETRY; RADIAL VELOCITIES; STARS: CARBON full text sources ADS | data products SIMBAD (706) Author (1)

Pre-main-sequence stars in the young cluster IC 2391

view Abstract Citations (65) References (26) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Pre--Main-Sequence Stars in the Young Cluster IC 2391 Stauffer, John ; Hartmann, Lee W. ; Jones, Burton F. ; McNamara, Brian R. Abstract Seven or eight new, late-type members of the poor open cluster IC 2391 are identified, and membership is confirmed for two other stars. The new members fall approximately along a 3 x 10 to the 7th yr isochrone, which is the age estimated for the cluster on the basis of it super main-seqence turnoff. Echelle spectra were obtained for the most probable cluster members. Most show H-alpha in emission and a strong Li 6707 A absorption line, and a few are rapid rotators. The Li abundances for cluster stars cooler than the sun are considerably less than the primordial Li abundance, providing the first direct evidence for substantial premain-sequence Li burning. The rotational velocities show a range from about 15 to 150 km/s, with a distribution of rotational velocities not significantly different from that observed for low-mass stars in the Pleiades. Publication: The Astrophysical Journal Pub Date: July 1989 DOI: 10.1086/167592 Bibcode: 1989ApJ...342..285S Keywords: Open Clusters; Pre-Main Sequence Stars; Stellar Evolution; Stellar Spectrophotometry; Absorption Spectra; Abundance; Color-Magnitude Diagram; Echelle Gratings; H Alpha Line; Lithium; Astrophysics; CLUSTERS: OPEN; STARS: EMISSION-LINE; STARS: EVOLUTION; STARS: PRE--MAIN-SEQUENCE full text sources ADS | data products SIMBAD (11) Related Materials (1) Erratum: 1990ApJ...350..480S

Eclipse studies of the dwarf nova OY Carinae in quiescence

view Abstract Citations (183) References (27) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Eclipse Studies of the Dwarf Nova OY Carinae in Quiescence Wood, Janet H. ; Horne, Keith ; Berriman, Graham ; Wade, Richard A. Abstract High-speed photometry of OY Car have been obtained which cover 20 eclipses in white light and seven eclipses in UBR. The results show the red dwarf to have a mass of 0.070 + or - 0.002 solar masses and a radius of 0.127 + or - 0.002 solar radii, and the white dwarf to have a temperature of several thousand degrees below 15,000 K. The bright spot is found to have a compact 15,000-K core and a tail that extends along the rim but does not penetrate far into the disk. Publication: The Astrophysical Journal Pub Date: June 1989 DOI: 10.1086/167557 Bibcode: 1989ApJ...341..974W Keywords: Dwarf Novae; Eclipsing Binary Stars; Light Curve; Stellar Spectrophotometry; Red Dwarf Stars; Stellar Models; Stellar Orbits; White Dwarf Stars; Astrophysics; STARS: ACCRETION; STARS: DWARF NOVAE; STARS: ECLIPSING BINARIES; STARS: INDIVIDUAL CONSTELLATION NAME: OY CARINAE; STARS: WHITE DWARFS full text sources ADS | data products SIMBAD (5)

Evidence for clustering of field horizontal-branch stars in the Galactic halo

view Abstract Citations (49) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Evidence for Clustering of Field Horizontal-Branch Stars in the Galactic Halo Doinidis, Steve P. ; Beers, Timothy C. Abstract An investigation of the clustering of field horizontal-branch stars in the Galactic halo is reported which examines this question using a catalog of over 4400 candidate field horizontal-branch stars distributed over roughly 2300 sq deg of sky, primarily in the southern Galactic hemisphere. A two-point correlation analysis indicates that the catalog contains an excess of stellar pairs with angular separations of less than 10 arcsec; at the approximate distances of these stars (5-8 kpc from the Sun) the corresponding linear separations are r of less than 25 pc. The possible connection with loose groups of halo field horizontal-branch stars noted previously by Sommer-Larsen and Christensen (1987) and by Beers and Doinidis (1988) is discussed. Publication: The Astrophysical Journal Pub Date: May 1989 DOI: 10.1086/185438 Bibcode: 1989ApJ...340L..57D Keywords: Horizontal Branch Stars; Milky Way Galaxy; Stellar Spectrophotometry; Distance; Monte Carlo Method; Spectral Line Width; Astrophysics; CLUSTERS: ASSOCIATIONS; STARS: HORIZONTAL-BRANCH full text sources ADS |

A search for remnant planetary nebulae around hot sdO stars

view Abstract Citations (25) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Search for Remnant Planetary Nebulae around Hot sdO Stars Kwitter, Karen B. ; Massey, Philip ; Congdon, Charles W. ; Pasachoff, Jay M. Abstract Spectroscopic and imaging searches for nebular emission associated with a sample of hot subdwarf O (sdO) stars have been carried out. Of 45 stars searched, no evidence of such nebulosity is found in 44. The single exception is RWT 152, around which a planetary nebula had been discovered previously. These negative results place constraints on the evolutionary history of these stars. Publication: The Astronomical Journal Pub Date: May 1989 DOI: 10.1086/115082 Bibcode: 1989AJ.....97.1423K Keywords: Hot Stars; O Stars; Planetary Nebulae; Subdwarf Stars; Emission Spectra; Main Sequence Stars; Stellar Evolution; Stellar Spectrophotometry; Astronomy; NEBULAE: PLANETARY; STARS: WHITE DWARFS; STARS: EARLY-TYPE full text sources ADS | data products SIMBAD (38)

Faint planetary nebulae in the Magellanic Clouds - Central star properties and nebular abundances for the Jacoby sample

view Abstract Citations (45) References (64) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Faint Planetary Nebulae in the Magellanic Clouds: Central Star Properties and Nebular Abundances for the Jacoby Sample Henry, Richard B. C. ; Liebert, James ; Boroson, T. A. Abstract We have studied 44 of the LMC and SMC planetary nebulae contained in the sample compiled by Jacoby. For each of these objects we employed spectrophotometric observations published by Boroson and Liebert to infer Stoy temperatures, luminosities, and radii of the central stars. For those objects in which [O III] electron temperatures could be determined (18 in the LMC, 11 in the SMC) nebular abundances of He, N, O, and Ne were calculated and compared with values for giant H II regions for the relevant host galaxy. While the levels of He, O, and Ne were comparable to the H II region abundances, the N abundance usually exceeded the interstellar level by roughly an order of magnitude. When we combined our abundance results with previously published results for planetary nebulae in the LMC, SMC, and the Galaxy, we found a strong correlation for O/H versus Ne/H and strong anticorrelations for O/H versus [O III] temperature, and N/O versus O/H. We conclude that most planetary nebulae show CNO products principally from the CN cycle, but that the N production of these stars is a decreasing function of progenitor metallicity or mass. A comparison of current planetary nebula progenitor yields of nitrogen with both theoretical predictions for intermediate-mass stars as well as the yield required to explain the interstellar level of that element in the LMC and SMC indicates that intermediate-mass stars contribute significantly to the interstellar N enrichment in the LMC, while their contribution in the SMC is somewhat less. Finally, we find that the average mass of nitrogen ejected during the planetary nebula phase is 3.1 x 10^-4^ M_sun_ and 6.1 x 10^-5^ M_sun_ in the LMC and SMC, respectively. Publication: The Astrophysical Journal Pub Date: April 1989 DOI: 10.1086/167342 Bibcode: 1989ApJ...339..872H Keywords: Abundance; Faint Objects; Magellanic Clouds; Planetary Nebulae; Stellar Spectrophotometry; H Ii Regions; Metallicity; Stellar Luminosity; Stellar Temperature; Astrophysics; GALAXIES: MAGELLANIC CLOUDS; NEBULAE: ABUNDANCES; NEBULAE: PLANETARY full text sources ADS | data products SIMBAD (44) NED (2)

Pulse sharpness and asymmetry in millisecond pulsars

view Abstract Citations (20) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Pulse Sharpness and Asymmetry in Millisecond Pulsars Chen, Kaiyou ; Shaham, Jacob Abstract The light curves of radiation from antipodal caps of rapidly rotating neutron stars are calcuated with and without gravity. The light curves depend strongly on the rotation speed and on the emission spectrum and could become quite sharp. Gravity generally flattens the light curves, but it does so less for rapidly rotating neutron stars and the newly discovered PSR 1957+20, and can never flatten them enough to explain the absence of pulsation from low-mass X-ray binaries. Rotation also causes an asymmetry in the pulses similar to that caused by interstellar medium absorption or scattering. Publication: The Astrophysical Journal Pub Date: April 1989 DOI: 10.1086/167295 Bibcode: 1989ApJ...339..279C Keywords: Gravitational Effects; Light Curve; Pulsars; X Ray Binaries; Doppler Effect; Emission Spectra; Stellar Envelopes; Stellar Magnetic Fields; Stellar Rotation; Stellar Spectrophotometry; Astrophysics; PULSARS; RELATIVITY; STARS: NEUTRON; STARS: ROTATION; X-RAYS: BINARIES full text sources ADS | data products SIMBAD (3)

Emission-line properties of optically and radio-selected complete quasar samples

view Abstract Citations (148) References (37) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Emission-Line Properties of Optically and Radio-selected Complete Quasar Samples Baldwin, J. A. ; Wampler, E. Joseph ; Gaskell, C. Martin Abstract We present spectrophotometry of two complete samples of quasars, one found from the flat radio spectra of the objects and the other from their optical colors. We confirm that the equivalent widths of the major ultraviolet emission lines decrease with increasing continuum luminosity (the "Baldwin effect"), and that the (Lyα + N V)/C IV and λ1909/C IV intensity ratios are also luminosity dependent by virtue of the C IV luminosity dependence. We also show that the Mg II/C IV intensity ratio and possibly the strengths of the blue Fe II emission features and the FWHM of the λ1909 blend are luminosity dependent. These results generally support the Mushotzky and Ferland interpretation of the Baldwin effect in terms of a weak inverse correlation between the continuum luminosity and ionization parameter. Except for the possibility of evolution with look-back time, these luminosity-dependent effects still appear to be a valid way of calibrating quasar luminosities for cosmological tests. Possible differences in the optical spectra which might correlate with the very different radio properties of these two quasar samples are masked by these luminosity-dependent effects. Any future comparison between optical and radio-selected quasars should be made using a fainter sample of optically selected quasars which have luminosities comparable to those of the radio-selected sample. Publication: The Astrophysical Journal Pub Date: March 1989 DOI: 10.1086/167224 Bibcode: 1989ApJ...338..630B Keywords: Emission Spectra; Quasars; Stellar Spectrophotometry; Luminosity; Radio Spectra; Red Shift; Astrophysics; COSMOLOGY; QUASARS; RADIO SOURCES: GENERAL; SPECTROPHOTOMETRY full text sources ADS | data products SIMBAD (112) NED (107) MAST (1)

Properties of the main-sequence eclipsing binary UZ Draconis

view Abstract Citations (9) References (18) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Properties of the Main-Sequence Eclipsing Binary UZ Draconis Lacy, Claud H. ; Gulmen, Omur ; Gudur, Necdet ; Sezer, Cengiz Abstract The fundamental properties of the main-sequence binary, UZ Dra, are determined from observational data. Photoelectric radial-velocity measurements (Imbert, 1986), spectroscopic data obtained with solid-state array detectors, and B,V photoelectric light curves of the binary are examined. The properties of the stars in the binary are presented and compared with those of other F-type main-sequence binaries listed by Popper (1980). Publication: The Astronomical Journal Pub Date: March 1989 DOI: 10.1086/115028 Bibcode: 1989AJ.....97..822L Keywords: Eclipsing Binary Stars; Main Sequence Stars; Stellar Evolution; Stellar Spectrophotometry; Light Curve; Line Spectra; Radial Velocity; Spectral Line Width; Astrophysics; STARS: INDIVIDUAL; STARS: ECLIPSING BINARIES full text sources ADS | data products SIMBAD (3)