Oxygen Spectra Research Articles

Laser Activation of Oxygen in Aerated Solvents. Measurement of the Absorption Spectra of Oxygen Dissolved in Aerated Solvents under Natural Conditions

Laser Activation of Oxygen in Aerated Solvents. Measurement of the Absorption Spectra of Oxygen Dissolved in Aerated Solvents under Natural Conditions

Carbon and oxygen isotopes in AGB stars. From the cores of AGB stars to presolar dust

AbstractIsotopic ratios are a powerful tool for gaining insights into stellar evolution and nucleosynthesis. The isotopic ratios of the key elements carbon and oxygen are perfectly suited to investigate the pristine composition of red giants, the conditions in their interiors, and the mixing in their extended atmospheres. Of course the dust ejected from red giants in their final evolution also contains isotopically tagged material. This red giant dust is present in the solar system as presolar dust grains. We have measured isotopic ratios of carbon and oxygen in spectra from a large sample of AGB stars including both Miras and semiregular variables. We show how the derived ratios compare with expectations from stellar models and with measurements in presolar grains. Comparison of isotopes that are affected by different types of nucleosynthesis provides insights into galactic evolution.

Simulation of Nitrogen and Oxygen Spectra Emitted from High Density Hot Plasma

The expected emission spectra of nitrogen and oxygen high density plasma have been studied for different conditions. Expected nitrogen and oxygen plasma spectra at certain electron temperature range have been plotted. Suitable electron temperature ranges for nitrogen and oxygen plasma soft X-ray emission and extreme ultraviolet emission have been investigated. Numerical experiments confirm the possibility of developing nitrogen and oxygen plasma focus as a powerful X-ray radiation source for water-window X-ray microscopy, by selecting the working gas pressure, choosing corresponding design and operating parameters of the device. We have illustrated that the results obtained from XRAYFIL simulation could be used to provide spectroscopic information of the plasma focus simulated by Lee model.

Stellar oxygen abundances. 4: Systematic effects on oxygen abundances derived from the 6300 A (O I) and 7774 A O I lines

view Abstract Citations (34) References (48) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Stellar Oxygen Abundances. IV. Systematic Effects on Oxygen Abundances Derived From the 6300 angstrom [OI] and 7774 angstrom OI Lines King, Jeremy R. ; Boesgaard, Ann Merchant Abstract We consider potential systematic effects on oxygen abundances derived from the 6300 A (OI) line and the 7774 A OI triplet. Our solar intensity spectra of the 7774 A triplet confirm previous results which indicate a discrepancy between the observed equivalent widths of Altrock (1968) and the values predicted by Local Thermodynamic Equilibrium (LTE) and recent NLTE models. However, this disagreement (at low micron(s)) does not seem to affect the solar O abundance as derived from flux spectra. We derive O abundances for a selection of relatively metal-rich F and G dwarfs from both the 6300 A (OI) line and 7774 A OI triplet and detail the various uncertainties which enter into the analyses. Minimizing possible systematic effects to the extent possible, we find for Teff approximately less than 6200-6300 K no systematic difference between the 6300 and 7774 A abundances. For Teff approximately greater than 6200-6300 K, however 7774 A abundances are substantially larger than the 6300 A abundances. This agreement in O abundances from the two features at cooler Teff conflicts with that of others and we suggest that the discrepancy may be due to the different model atmospheres utilized. If recently proposed, hotter Teff values for metal-poor dwarfs are correct, then there appears to be no discrepancy between the 6300 A abundances of metal-poor giants are correct, then there appears to be no discrepancy between the 6300 A abundances of metal-poor giants or dwarfs and the 7774 A abundances for dwarfs. This would seem to rule out substantial LTE departures or atmospheric inhomogeneity effects skewing metal-poor O abundances from the 7774 A triplet (for cooler stars having low metallicity anyway). Given the repeated inability of authors to reproduce each others' O abundances from the 6300 A (OI) line and the uncertainties in the solar equivalent width, we question the usual assumption that the 6300 A (OI) line and the uncertainties in the solar equivalent width, we question the usual assumption that the 6300 A (OI) abundances are more reliable than those from the permitted triplet. Publication: The Astronomical Journal Pub Date: January 1995 DOI: 10.1086/117283 Bibcode: 1995AJ....109..383K Keywords: Abundance; Oxygen; Oxygen Spectra; Stellar Atmospheres; Dwarf Stars; Infrared Spectra; Local Thermodynamic Equilibrium; Metallicity; Visible Spectrum; Astronomy; STARS: ABUNDANCES; STARS: ATMOSPHERES; STARS: INTERIORS full text sources ADS | data products SIMBAD (49) Related Materials (4) Part 1: 1993AJ....106.1206K Part 2: 1994AJ....107..350K Part 3: 1994ApJ...436..331K Part 5: 1996AJ....112.2650K

CCD imaging of NGC 4861: Ionized gas properties and stellar formation

view Abstract Citations (15) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS CCD Imaging of NGC 4861: Ionized Gas Properties and Stellar Formation Barth, Clarissa S. ; Cepa, Jordi ; Vilchez, Jose M. ; Dottori, Horacio A. Abstract This work undertakes the study of the galaxy NGC 4861, using imaging centered at the strong lines Hα, Hβ, [O III] λ5007 and nearby continua. Integrated, absolute fluxes of 28 H II regions, and the region known as the bright knot, have been measured showing correlations between the equivalent width of Hβ and the excitation index log([O III]/β). An excitation gradient has been detected along the chain of H II regions extending northwards from the bright knot, which is unusual for irregular galaxies like NGC 4861. We suggest that this gradient is due to different stages of evolution, or ages, of the HII regions. The continuum fluxes of eight emissionless associations and the continuum colors of the companion galaxy IC 3961 have also been measured, and the presence of ionized gas cannot be detected. The age and mass of the stellar population and ionizing stars of the bright knot were subsequently estimated. It was also verified that this region is the most important burst of star formation in NGC 4861. Publication: The Astronomical Journal Pub Date: December 1994 DOI: 10.1086/117219 Bibcode: 1994AJ....108.2069B Keywords: Galactic Evolution; H Alpha Line; H Beta Line; H Ii Regions; Ionized Gases; Oxygen Spectra; Peculiar Galaxies; Star Formation; Balmer Series; Charge Coupled Devices; Chronology; Computer Programs; Stellar Mass; Astronomy; GALAXIES: INDIVIDUAL: NGC 4861; GALAXIES: ABUNDANCES; STARS: FORMATION full text sources ADS | data products SIMBAD (43) NED (1)

Bright planetary nebulae as probes of chemical evolution

view Abstract Citations (27) References (37) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Bright Planetary Nebulae as Probes of Chemical Evolution Richer, Michael G. Abstract A compilation of observations of planetary nebulae in the Magellanic Clouds has been used to study the utility of bright extragalactic planetary nebulae as distance indicators and as probes of chemical evolution. A planetary nebula's [O III] λ5007 luminosity is shown to be primarily a result of the ultraviolet luminosity of its central star, confirming Jacoby's (1989) original proposal. However, the oxygen abundance is observed to modify the maximum [O III] λ5007 luminosity actually attained. As a result, the planetary nebula luminosity function will overestimate the distances to low-luminosity galaxies. A procedure to correct the distance moduli of low-luminosity galaxies relative to the LMC is outlined. As chemical abundance probes, the brightest planetary nebulae in a galactic population appear to be very promising. A luminosity-limited study will preferentially select the planetary nebulae with the highest oxygen abundances because of the abundance dependence of the [O III] λ5007 luminosity. In the Magellanic Clouds, H II regions and bright planetary nebulae have similar oxygen abundances, so, from a chemical evolution viewpoint, both must represent recent star formation events. Consequently, bright planetary nebulae should be reliable probes of the interstellar medium oxygen abundance during the last episode of star formation, which is especially useful in galaxies that are no longer forming stars. If the width of the SMC's abundance distribution is typical of that in low-luminosity galaxies, only three planetary nebulae are required to determine the oxygen abundance at the last epoch of star formation to within +/-0.1 dex. Publication: The Astrophysical Journal Pub Date: September 1993 DOI: 10.1086/173159 Bibcode: 1993ApJ...415..240R Keywords: Chemical Evolution; Magellanic Clouds; Oxygen Spectra; Planetary Nebulae; H Ii Regions; Stellar Luminosity; Astrophysics; ISM: H II REGIONS; ISM: ABUNDANCES; GALAXIES: MAGELLANIC CLOUDS; ISM: PLANETARY NEBULAE: GENERAL full text sources ADS | data products SIMBAD (50) NED (2)

The planetary nebula system and dynamics of NGC 5128. I - Planetary nebulae as standard candles

view Abstract Citations (165) References (41) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Planetary Nebula System and Dynamics of NGC 5128. I. Planetary Nebulae as Standard Candles Hui, Xiaohui ; Ford, Holland C. ; Ciardullo, Robin ; Jacoby, George H. Abstract We present the result of a planetary nebula (PN) survey of the nearby giant elliptical galaxy NGC 5128 performed with CCD cameras at the prime focus of the CTIO 4 m telescope. By comparing CCD images centered on the characteristic emission line [O III] λ5007 and on the adjacent continuum, we identify a total of 785 PNs in areas extending 20 kpc along the photometric major axis and covering the whole galaxy to 10 kpc. From these data, we form a complete sample of 224 PNs extending to a dereddened limiting magnitude of m_5007_ = 24.8, which extends 1.5 mag down the PN luminosity function (PNLF). Adopting a foreground extinction of E(B- V) = 0.1, we derive a distance to the galaxy of 3.5 +/- 0.2 Mpc, in excellent agreement with the surface brightness fluctuation method. No population effect on the bright cutoff of PNLF is observed in the isophotal radius range of 2-16 kpc, but the luminosity specific PN density (α_2.5_) seems to increase with radius inside of 7 kpc, in agreement with the α_2.5_-color relation observed for other galaxies. Publication: The Astrophysical Journal Pub Date: September 1993 DOI: 10.1086/173093 Bibcode: 1993ApJ...414..463H Keywords: Astrometry; Elliptical Galaxies; Galactic Halos; Galactic Structure; Luminosity; Planetary Nebulae; Astronomical Photometry; Chemical Evolution; Emission Spectra; Galactic Evolution; Magnitude; Mass Distribution; Oxygen Spectra; Astrophysics; COSMOLOGY: DISTANCE SCALE; GALAXIES: INDIVIDUAL NGC NUMBER: NGC 5128; ISM: PLANETARY NEBULAE: GENERAL full text sources ADS | data products SIMBAD (15) NED (1) CDS (1) Related Materials (2) Part 2: 1993ApJS...88..423H Part 3: 1995ApJ...449..592H

Detection of O II 2471-A forbidden line from the Io plasma torus

view Abstract Citations (21) References (35) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Detection of [O ii] lambda 2471 from the Io Plasma Torus McGrath, M. A. ; Feldman, P. D. ; Strobel, D. F. ; Moos, H. W. ; Ballester, G. E. Abstract We report the first detection of the O II 2471-A forbidden line from the Io plasma torus. Observations of the east and west torus ansae at 5.7 R(J) on 1992 March 15 and May 1, respectively, using the Goddard High Resolution Spectrograph of the HST have resulted in about 5-sigma detections of the line on both occasions, with line brightnesses of 30 +/- 5 R and 28 +/- 5 R for the east and west ansae respectively in a 2 x 2 arcsec FOV. The lines are Doppler-shifted relative to the rest wavelength (vacuum) of 2471.04 A, with a separation of 1.30 +/- 0.25 A between the east and west lines, implying a torus rotation velocity of 79 +/- 15 km/s, consistent with that expected at a radial distance of 5.7 R(J). Assuming a torus electron temperature and density distribution consistent with Voyager I in situ measurements and homogeneous mixing of O(+) relative to electron density along the line of sight, the observed line brightnesses imply an average O(+) mixing ratio of 0.26 +/- 0.05, in agreement with a value derived previously by Moos et al. (1991), but lower than that derived from Voyager observations. There is no significant difference in average brightness between the east (dawn) and west (dusk) ansa observations. Publication: The Astrophysical Journal Pub Date: September 1993 DOI: 10.1086/187031 Bibcode: 1993ApJ...415L..55M Keywords: Io; Jupiter Atmosphere; Oxygen Spectra; Planetary Magnetospheres; Satellite Atmospheres; Toroidal Plasmas; Solar System; Ultraviolet Spectrometers; Lunar and Planetary Exploration; PLANETS AND SATELLITES: INDIVIDUAL JUPITER; PLANETS AND SATELLITES: INDIVIDUAL IO; PLASMAS; ULTRAVIOLET: SOLAR SYSTEM full text sources ADS | data products MAST (2) ESA (1)

Observed redshifts in O V and downflows in the solar transition region

view Abstract Citations (61) References (76) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Observed Redshifts in O V and Downflows in the Solar Transition Region Brekke, P. Abstract Spectrograms from HRTS are used to find an average net redshift of the O V lines at 1218 and 1371 A at all locations extending from disk center to solar limb. The observed shift in O V is compared with measurements of the O IV line at 1401 A and the Si IV line at 1402 A. Large variations in the shift are found along the instrument slit. Blueshifts are also observed with the sites of the largest upflow located in the sunspot umbrae and in a quiet region close to an active region. The present result could put new constraints on numerical models of flows in the solar transition region and will also be of importance for modeling stellar atmospheres. The spatial variation of line-of-sight velocities in the O V line at 1371A and the SI IV line at 1402 A is illustrated. Publication: The Astrophysical Journal Pub Date: May 1993 DOI: 10.1086/172633 Bibcode: 1993ApJ...408..735B Keywords: Doppler Effect; Magnetohydrodynamic Flow; Oxygen Spectra; Red Shift; Solar Corona; Ultraviolet Radiation; Hubble Space Telescope; Skylab Program; Spectrographs; Umbras; Solar Physics; SUN: UV RADIATION; SUN: TRANSITION REGION; SUN: CORONA full text sources ADS |

The ionized gas in the center and in the bar of the spiral galaxy NGC 6946

view Abstract Citations (14) References (54) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Ionized Gas in the Center and in the Bar of the Spiral Galaxy NGC 6946 Roy, Jean-Rene ; Belley, Julien Abstract Spectrophotometric data based on narrow-band images at Hα, Hβ, [O III] λ5007 and [N II] λ6584 for 189 H II regions in the spiral galaxy NGC 6946 are presented, with emphasis on the inner regions (R <= 2.5 kpc). The properties of the ionized gas are compared with those of the CO molecular bar. The possible influence of the bar on the ionized interstellar gas and star formation is discussed. The relatively high number of H II regions in the center is consistent with an enhancement of massive star formation as revealed by infrared and molecular observations the molecular gas bar in NGC 6946 is a favorable environment for massive star formation. The excitation and abundance indicators [O III] (λλ5007 + 4959)/Hβ and [N II] (λλ6584 + 6548)/[O III] (λλ5007+4959) show an unusual behavior as a function of galactocentric distances, and their radial trend is consistent with a flattening of the global O/H gradient in the inner regions of NGC 6946. This may be evidence of dilution by low-metallicity gas from outer regions due to strong radial flow along the molecular bar. Publication: The Astrophysical Journal Pub Date: March 1993 DOI: 10.1086/172420 Bibcode: 1993ApJ...406...60R Keywords: H Ii Regions; Ionized Gases; Spiral Galaxies; Star Formation; Gas Dynamics; H Beta Line; Oxygen Spectra; Astrophysics; GALAXIES: ISM; GALAXIES: INDIVIDUAL NGC NUMBER: NGC 6946; GALAXIES: SPIRAL; ISM: H II REGIONS; ISM: ABUNDANCES; ISM: MOLECULES full text sources ADS | data products SIMBAD (3) NED (1)

Far-ultraviolet observations of the supernova remnant N49 using the Hopkins Ultraviolet Telescope

view Abstract Citations (15) References (28) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Far-Ultraviolet Observations of the Supernova Remnant N49 Using the Hopkins Ultraviolet Telescope Vancura, Olaf ; Blair, William P. ; Long, Knox S. ; Davidsen, Arthur F. ; Bowers, Charles W. ; Dixon, W. Van Dyke ; Durrance, Samuel T. ; Feldman, Paul D. ; Ferguson, Henry C. ; Henry, Richard C. ; Kimble, Randy A. ; Kriss, Gerard A. ; Kruk, Jeffrey W. ; Moos, H. Warren Abstract Using the Hopkins Ultraviolet Telescope on the Astro-1 space shuttle mission in 1990 December, we have obtained a far-ultraviolet spectrum (912-1860 A at 3.5 A resolution) of a complex of bright filaments located in the eastern part of the supernova remnant N49 in the Large Magellanic Cloud. This is the first observation of an extragalactic supernova remnant that extends to the Lyman limit. We detect lines of O VI λ1035, O IV] λ1403, C IV λ1550, and He II λ1640. The O VI emission that we observe cannot originate in shocks with velocities <= 140 km s^-1^ which are responsible for the bulk of both the C IV and the optical line emission. Likewise, the main blast wave with a velocity ~730 km s^-1^ is unable to account for the brightness of O VI. Most of the O VI originates in optically faint, 190-270 km s^-1^ shocks, traversing clouds with densities of 20-40 cm^-3^. We expand upon earlier modeling of N49 IUE and optical spectra that assumed a distribution of shock velocities including data from below Lyα, such models still describe the data well. Publication: The Astrophysical Journal Pub Date: December 1992 DOI: 10.1086/172054 Bibcode: 1992ApJ...401..220V Keywords: Astronomical Models; Far Ultraviolet Radiation; Spaceborne Astronomy; Supernova Remnants; Carbon; Helium Ions; Magellanic Clouds; Oxygen Spectra; Astrophysics; ISM: INDIVIDUAL ALPHANUMERIC: N49; GALAXIES: MAGELLANIC CLOUDS; SHOCK WAVES; ISM: SUPERNOVA REMNANTS; ULTRAVIOLET: INTERSTELLAR full text sources ADS | data products NED (2) MAST (2) SIMBAD (1)

Observations of the velocity curves of NGC 1068

view Abstract Citations (15) References (41) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Observation of the Velocity Curves of NGC 1068 Kaneko, Noboru ; Satoh, Tetsuya ; Toyama, Kiyotaka ; Sasaki, Minoru ; Nishimura, Masaki ; Yamamoto, Masafumi Abstract For 132 spectra of NGC 1068 taken at 24 position angles of every 15^deg^ from an isophotal major axis (P.A. = 52^deg^) of the inner arm region, we measured Hα, Hβ [N II] λ6583, and [O III] λλ4959,5007 to present the velocity curves in tabular form. Comparisons are made with previous observations to show that our measurements are consistent with the recent observations, but inconsistent with Walker's measurements. Combined with CO velocity data, the velocity field was analyzed to reveal large-scale noncircular motions to occur within the galaxy. Publication: The Astronomical Journal Pub Date: February 1992 DOI: 10.1086/116071 Bibcode: 1992AJ....103..422K Keywords: Galactic Rotation; Spiral Galaxies; Starburst Galaxies; Velocity Distribution; Carbon Monoxide; Forbidden Transitions; H Alpha Line; H Beta Line; Nitrogen; Oxygen Spectra; Astrophysics; GALAXIES: STARSBURST; GALAXIES: KINEMATICS AND DYNAMICS full text sources ADS | data products SIMBAD (1) NED (1)

Solar gravitational redshift from the infrared oxygen triplet

view Abstract Citations (42) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Solar Gravitational Redshift from the Infrared Oxygen Triplet Lopresto, James C. ; Schrader, Charles ; Pierce, A. K. Abstract The difference in wavelength between the IR oxygen triplet 7772-7775 A in the sun and in the laboratory has been observed. Converted to velocities, the disk values, extrapolated to the limb, give a redshift of 655 m/s compared to the value of 636 m/s predicted from the principal of equivalence. Observations of the chromospheric oxygen lines in emission just off the sun's limb give a velocity of 627 m/s or 0.99 of the Einstein prediction. Publication: The Astrophysical Journal Pub Date: August 1991 DOI: 10.1086/170323 Bibcode: 1991ApJ...376..757L Keywords: Gravitational Effects; Red Shift; Relativity; Solar Spectra; Chromosphere; Infrared Spectra; Oxygen Spectra; Solar Gravitation; Solar Physics; GRAVITATION; INFRARED: SPECTRA; RELATIVITY; SUN: SPECTRA full text sources ADS |

First results from the Faint Object Camera - Imaging the core of R Aquarii

view Abstract Citations (22) References (18) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS First Results from the Faint Object Camera: Imaging the Core of R Aquarii Paresce, F. ; Albrecht, R. ; Barbieri, C. ; Blades, J. C. ; Boksenberg, A. ; Crane, P. ; Deharveng, J. M. ; Disney, M. J. ; Jakobsen, P. ; Kamperman, T. M. ; King, I. R. ; Macchetto, F. ; Mackay, C. D. ; Weigelt, G. ; Baxter, D. ; Greenfield, P. ; Jedrzejewski, R. ; Nota, A. ; Sparks, W. B. Abstract The Faint Object Camera on the HST was pointed toward the symbiotic long-period M7e Mira variable R Aquarii, and very high resolution images of the inner core, mainly in the ionized oxygen emission lines in the optical, are reported. Both images show bright arcs, knots, and filaments superposed on a fainter, diffuse nebulosity extending in a general SW-NE direction from the variable to the edge of the field at 10 arcsec distance. The core is resolved in forbidden O III 5007 A and forbidden O II 3727 A into at least two bright knots of emission whose positions and structures are aligned with PA = 50 deg. The central knots appear to be the source of a continuous, well-collimated, stream of material extending out to 3-4 arcsec in the northern sector corresponding to a linear distance of about 1000 AU. The northern stream seems to bend around an opaque obstacle and form a spiral before breaking up into wisps and knots. The southern stream is composed of smaller, discrete parcels of emitting gas curving to the SE. Publication: The Astrophysical Journal Pub Date: March 1991 DOI: 10.1086/185960 Bibcode: 1991ApJ...369L..67P Keywords: Faint Object Camera; Mira Variables; Nebulae; Stellar Spectra; Symbiotic Stars; Emission Spectra; Forbidden Transitions; Oxygen Spectra; Astrophysics; NEBULAE: INDIVIDUAL NAME: R AQUARII; STARS: INDIVIDUAL CONSTELLATION NAME: R AQUARII; STARS: SYMBIOTIC full text sources ADS | data products SIMBAD (1) MAST (1) ESA (1)

A new age diagnostic applied to the globular clusters NGC 288 and NGC 362

view Abstract Citations (134) References (41) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A New Age Diagnostic Applied to the Globular Clusters NGC 288 and NGC 362 Sarajedini, Ata ; Demarque, Pierre Abstract A new age diagnostic for globular clusters is described which uses the difference between the turnoff and the base of the giant branch as the age indicator. As a first application, it is shown that there is a difference in age of 3.1 + or - 0.9 Gyr between the classic 'second parameter' pair NGC 288 and NGC 362. The existence of this age difference is independent of metal abundance differences between the two clusters of up to 0.5 dex. This age difference is corrected for various combinations of relative oxygen enhancement, and it is concluded that the difference in age remains significant for all plausible scenarios. Publication: The Astrophysical Journal Pub Date: December 1990 DOI: 10.1086/169472 Bibcode: 1990ApJ...365..219S Keywords: Abundance; Color-Magnitude Diagram; Globular Clusters; Main Sequence Stars; Stellar Evolution; Galactic Evolution; Helium; Metallicity; Oxygen Spectra; Astrophysics; CLUSTERS: GLOBULAR; STARS: ABUNDANCES; STARS: EVOLUTION; STARS: POPULATION II full text sources ADS | data products SIMBAD (2)

Internal redshift difference and central mass in QSOs

view Abstract Citations (32) References (26) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Internal Redshift Difference and Central Mass in QSOs Zheng, Wei ; Sulentic, Jack W. Abstract The redshifts of broad Hβ and narrow [O III] emission lines are measured and compared in 31 low-redshift QSOs with weak or absent optical Fe II features. The redshifts are often not the same for the broad and narrow lines. The distribution of peak redshift differences for our sample is centered near zero. At larger widths the distribution is skewed, suggesting that Hβ more often shows a higher redshift. A mean redshift difference at FWHM of ~ 300 km s^-1^ is found between broad Hβ and the narrow [O III] lines. This value appears to set an upper limit to the central mass, on the order of 10^9^ M_sun_, and further to imply the dominance of radiative acceleration in the broad line region of these QSOs. Publication: The Astrophysical Journal Pub Date: February 1990 DOI: 10.1086/168407 Bibcode: 1990ApJ...350..512Z Keywords: Active Galactic Nuclei; Forbidden Transitions; H Beta Line; Mass Distribution; Quasars; Red Shift; Iron; Line Spectra; Oxygen Spectra; Astrophysics; GALAXIES: REDSHIFTS; QUASARS full text sources ADS | data products NED (31) SIMBAD (30)

The optically thick O III spectrum. I - Diagnostic ratios involving the intercombination lines

view Abstract Citations (14) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Optically Thick O III Spectrum. I. Diagnostic Ratios Involving the Intercombination Lines Kastner, S. O. ; Bhatia, A. K. Abstract An escape-probability calculation of the optically thick O III spectrum is carried out to obtain the optical depth dependence of the intercombination doublet at 1663 A and of resonance lines between the 2p2, 2s2p3, and 2p4 configurations. The effect of optical depth on diagnostic ratios involving the intercombination lines is quantitatively established. The general question raised is whether such effects may occur in actual sources. Publication: The Astrophysical Journal Supplement Series Pub Date: November 1989 DOI: 10.1086/191392 Bibcode: 1989ApJS...71..665K Keywords: Astronomical Photometry; Optical Thickness; Oxygen Spectra; Ultraviolet Spectra; Computational Astrophysics; Electron Transitions; Iue; Resonance Lines; Astrophysics; ATOMIC PROCESSES; ULTRAVIOLET: SPECTRA full text sources ADS |

An escape probability treatment of line fluorescence and overlap in astrophysics

view Abstract Citations (16) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS An Escape Probability Treatment of Line Fluorescence and Overlap in Astrophysics Lockett, Philip ; Elitzur, Moshe Abstract An escape probability method is developed that utilizes realistic line profiles to account for line overlap effects. This enables a test of the accuracy of the simpler procedure developed by Elitzur and Netzer (1985) that is also based on the escape probability method but which utilizes rectangular profiles. Good agreement is found between the two methods in calculations involving a range of possible physical situations including the Bowen fluorescence phenomenon. the simple rectangular profile method can thus be used with confidence in escape probability calculations involving line overlap. Calculations using the more accurate method are performed to see what effects the overlap of the far-infrared rotational lines of the OH molecule have on the ground-state hyperfine levels. It is found that the overlap can lead to inversion and thus to maser production. Publication: The Astrophysical Journal Pub Date: September 1989 DOI: 10.1086/167822 Bibcode: 1989ApJ...344..525L Keywords: Astronomical Spectroscopy; Fluorescence; Line Spectra; Spectrum Analysis; Far Infrared Radiation; Hydroxyl Radicals; Hyperfine Structure; Molecular Spectra; Oxygen Spectra; Astrophysics; ATOMIC PROCESSES; LINE PROFILES; MOLECULAR PROCESSES full text sources ADS |

A detailed study of the remnant of nova GK Persei and its environs

view Abstract Citations (71) References (75) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Detailed Study of the Remnant of Nova GK Persei and Its Environs Seaquist, E. R. ; Bode, M. F. ; Frail, D. A. ; Roberts, J. A. ; Evans, A. ; Albinson, J. S. Abstract Observational data on the nova remnant GK Persei and its environs at a variety of wavelengths are presented and discussed. The data suggest that the nova exploded into a circumstellar cloud whose mass is estimated to be several solar masses and whose mean diameter is several pc. Radio images of the nonthermal emission associated with the interaction of the nova ejecta with this material show a remarkable similarity to young SNR. A suggestion made by Bode et al. (1987) that the circumstellar cloud is the neutral remnant of a PN which occurred about 100,000 yr ago is examined in detail. It is concluded that this interpretation provides a remarkably consistent framework for the interpretation of all the data. Publication: The Astrophysical Journal Pub Date: September 1989 DOI: 10.1086/167846 Bibcode: 1989ApJ...344..805S Keywords: Cataclysmic Variables; Novae; Planetary Nebulae; Radio Sources (Astronomy); Supernova Remnants; Dwarf Novae; Hydrogen; Oxygen Spectra; Radio Observation; Visual Observation; Astrophysics; NEBULAE: INDIVIDUAL NAME: GK PERSEI; NEBULAE: PLANETARY; RADIO SOURCES: EXTENDED; RADIO SOURCES: 21 CM RADIATION; STARS: INDIVIDUAL CONSTELLATION NAME: GK PERSEI; STARS: NOVAE full text sources ADS | data products SIMBAD (3)

The abundance gradient across the galaxy NGC 2997

view Abstract Citations (33) References (25) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Abundance Gradient across the Galaxy NGC 2997 Walsh, J. R. ; Roy, Jean-Rene Abstract The fiber optics coupling aperture-plate system (FOCAP) of the Anglo-Australian Observatory was used to obtain low-dispersion spectra of 49 H II regions across the galaxy NGC 2997. Problems with employing fiber optics for spectrophotometry are discussed. Correlations between line ratios used as diagnostics for physical conditions and abundances in H II regions are identical to those found by McCall, Rybski, and Shields for a large number of giant H II regions in 26 galaxies. The O/H radial abundance gradient in NGC 2997 was derived using the calibration of the index ([O II] + [O III])/Hβ. The gradient and the mean metallicity of NGC 2997 are comparable to those of M51. There is significant dispersion in ([O 1I] + [O II])/Hβ and [O III]/Hβ at any given galactocentric distance. No N^+^/O^+^ gradient is observed, and the mean value of this ratio is identical to that of Galactic H II regions. Publication: The Astrophysical Journal Pub Date: June 1989 DOI: 10.1086/167531 Bibcode: 1989ApJ...341..722W Keywords: Abundance; Astronomical Spectroscopy; Galaxies; H Ii Regions; Spectrophotometry; Forbidden Transitions; Metallicity; Oxygen Spectra; Astrophysics; GALAXIES: ABUNDANCES; GALAXIES: INDIVIDUAL NGC NUMBER: NGC 2997; NEBULAE: ABUNDANCES; NEBULAE: H II REGIONS full text sources ADS | data products SIMBAD (4) NED (4)