Beta Line Research Articles

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)

Stellar spectra reconstruction from speckle spectroscopic data

view Abstract Citations (18) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Stellar Spectra Reconstruction From Speckle Spectroscopic Data Kuwamura, Susumu ; Baba, Naoshi ; Miura, Noriaki ; Hege, E. K. Abstract We describe a method to reconstruct stellar spectra from dispersed speckle data with diffraction-limited angular resolution. A shift-and-add (SAA) method is applied on many short exposure frames, each of which contains a dispersed speckle image and a corresponding nondispersed speckle image as a reference. The spectra of the binary star ADS 16836 were reconstructed in wideband and low dispersion mode from the data taken with the Hokudai speckle spectroscopic camera system using the Okayama 188 cm telescope. The result shows the well-separated spectra of the primary and the secondary stars, which are otherwise too close to be distinguishable due to atmospheric turbulence. These results also demonstrate high spatial resolution spectroscopy for a binary star and for a resolvable hypergiant using our SAA speckle method. Publication: The Astronomical Journal Pub Date: February 1993 DOI: 10.1086/116465 Bibcode: 1993AJ....105..665K Keywords: Data Processing; Diffraction Limited Cameras; Speckle Patterns; Spectroscopic Analysis; Stellar Spectra; Angular Resolution; Atmospheric Turbulence; Binary Stars; H Beta Line; Astronomy; TECHNIQUES: SPECTROSCOPIC full text sources ADS | data products SIMBAD (5)

The spatial and temporal development of pseudospark switch plasmas

Optical spectroscopy is used to investigate the spatial and temporal development of high-current pseudospark switch plasmas. At a peak discharge current of 12 kA in amplitude and a current reversal of 20%, the electron density is measured from Stark width broadening of the hydrogen Balmer beta line. The peak electron density of approximately 4*10/sup 15/ cm/sup -3/ is measured briefly after the current maximum. The discharge initially starts on the symmetry axis of the cathode hole. A cylindrical plasma column is observed, which is produced mainly by ionizing collisions of beam electrons formed in the hollow cathode during the early part of the discharge. This plasma column rapidly expands in the radial direction, until it contacts the edge of the cathode hole. The same behavior is found when the Balmer beta line intensity is evaluated rather than the line shape. Although statistically distributed, localized bursts of light are found occasionally, an axially symmetric, homogeneous light intensity distribution is always predominant, and the local arcing is merely superimposed on it. These results confirm that the discharge remains diffuse during most of the current pulse. >

Imaging of four planetary nebulae in the Magellanic Clouds using the Hubble Space Telescope Faint Object Camera

view Abstract Citations (25) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Imaging of Four Planetary Nebulae in the Magellanic Clouds Using the Hubble Space Telescope Faint Object Camera Blades, J. C. ; Barlow, M. J. ; Albrecht, R. ; Barbieri, C. ; Boksenberg, A. ; Crane, P. ; Deharveng, J. M. ; Disney, M. J. ; Jakobsen, P. ; Kamperman, T. M. ; King, I. R. ; Macchetto, F. ; Mackay, C. D. ; Paresce, F. ; Weigelt, G. ; Baxter, D. ; Greenfield, P. ; Jedrzejewski, R. ; Nota, A. ; Osmer, S. ; Sparks, W. B. Abstract Using the Faint Object Camera on-board the Hubble Space Telescope, we have obtained images of four planetary nebulae (PNe) in the Magellanic Clouds, namely N2 and N5 in the SMC and N66 and N201 in the LMC. Each nebula was imaged through two narrow-band filters isolating [O III] λ5007 and Hβ, for a nominal exposure time of 1000 s in each filter. Significant detail is evident on the raw images and, after deconvolution using the Richardson-Lucy algorithm, structures as small as 0.06" are easily discernible. In [O III], SMC N5 shows a circular ring structure, with a peak-to-peak diameter of 0.26" and a FWHM of 0.35", while SMC N2 shows an elliptical ring structure with a peak-to-peak diameter of 0.26" x 0.21" (FWHM 0.40" x 0.35"). The expansion ages corresponding to the observed structures in SMC N2 and N5 are of the order of 3000 yr. Such low ages appear more easy to reconcile with helium-burning rather than hydrogen-burning central star evolutionary tracks. LMC N201 is very compact, with a FWHM of 0.21" in Hβ. The Type I PN LMC N66 is a multipolar nebula, with the brightest part having an extent of about 2" and with fainter structures extending over 4". The [O III] image reveals structures unprecedented for a planetary nebula, with several bright knots and faint loops visible outside the two main bright lobes. Publication: The Astrophysical Journal Pub Date: October 1992 DOI: 10.1086/186572 Bibcode: 1992ApJ...398L..41B Keywords: Faint Object Camera; Hubble Space Telescope; Magellanic Clouds; Planetary Nebulae; Spaceborne Astronomy; H Beta Line; Stellar Evolution; Stellar Structure; Astrophysics full text sources ADS | data products SIMBAD (7) NED (2) MAST (1) ESA (1)

Determination of the He(+)/H(+) ratio from alpha, beta, and gamma radio recombination lines

High signal-to-noise ratio observations of the 91α, 114β, and 130γ hydrogen and helium radio recombination lines toward several Galactic H II regions are reported. These observations were used to determine the ionized helium-to-ionized hydrogen abundance ratio by number, y + . Since the observations were made with the same radio telescope at approximately the same frequency, we consider them to be practically free of beamwidth and frequency effects. For a given source, we find y + values consistent within error for the different n values measured

The H II regions of the galaxy M101

view Abstract Citations (65) References (57) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The H II Region of the Galaxy M101 Scowen, P. A. ; Dufour, R. J. ; Hester, J. J. Abstract Spectrophotometrically calibrated CCD imagery of two overlapping 16 arcmin fields in the SAB (rs)cdI galaxy M101 in the emission of Hα, [O III] λ5007, Hβ, and [S II] λ6723 are used to study various physical properties of the H II region population. Individual H II regions are identified and mapped using an automated algorithm thus eliminating personal bias in the measurements. Characteristics of the population studied include the H II region luminosity function and radial variations in extinction, [O III]/Hβ, O/H, [S II]/Hα, ionization parameter and numbers of ionizing photons. In addition, radial and azimuthal variations in the H II surface density are studied in comparison to that of H I and H_2_ inferred from radio 21 cm and CO observationS. It is demonstrated that the magnitude of trends and "gradients" found from such analyses depend on the surface-brightness threshold set in defining the H II region boundaries; so results are presented for both low (log F (Hα) = - 15.7 ergs s^-1^ cm^-2^ pixel^-2^; 625 H II regions) and high (-15.0; 248 H II regions) thresholds. Radial gradients in both extinction, C(Hβ)7 and O/H are seen in the H II region population- with a distinct flattening in the O/H gradient seen in the outer disk beginning at about 10 kpc. The luminosity function of the H II region population found is similar to previous studies, though both the high and low ends are sensitive to the threshold levels set. Other parameters such as the ionization parameters luminosities, and size distribution, show no evidence for systematic variations with galactocentric distance. Current star-formation processes active in the disk of M101 are analyzed two dimensionally by comparison of the distribution of ionized and neutral hydrogen. The star-formation efficiency shows considerable variation across the disk, suggesting significant spatial variation in the critical density for cloud collapse across the disk of M101 and thus departures from the simple Toomre model. Publication: The Astronomical Journal Pub Date: July 1992 DOI: 10.1086/116223 Bibcode: 1992AJ....104...92S Keywords: Astronomical Photometry; Charge Coupled Devices; H Ii Regions; Luminous Intensity; Spiral Galaxies; Star Formation; Active Galactic Nuclei; Carbon Monoxide; H Alpha Line; H Beta Line; Line Of Sight; Oxygen; Sulfur; Astrophysics; GALAXIES: SPIRAL; GALAXIES: INDIVIDUAL: M101; H II REGIONS full text sources ADS | data products SIMBAD (253) NED (251) CDS (1) Related Materials (1) Erratum: 1994AJ....107.1203S

The broad emission-line profiles and profile variability of the Seyfert 1 galaxy Arakelian 120

view Abstract Citations (35) References (42) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Broad Emission-Line Profiles and Profile Variability of the Seyfert 1 Galaxy Arakelian 120 Korista, Kirk T. Abstract We present Hα and Hβ broad emission-line profiles of the Seyfert galaxy Arakelian 120 from the past ~10 yr, representing over 100 spectroscopic observations. The broad emission-line profiles of the Balmer lines are complex in structure and variable; the profile variations themselves are complex. We attempt to isolate separate emitting components within the profiles through profile differencing and profile fitting. If Gaussian-like, at least four separate components are present in the broad Balmer emission lines. The broad emission-line profiles of other emission lines (optical and UV) are also presented, and evidence is given for a stratified BLR. Using the results of Joly, we demonstrate that the Fe II multiplets 25 and 36 (in addition to m42) may be present in the Hβ profile and in its "red shelf." Publication: The Astrophysical Journal Supplement Series Pub Date: April 1992 DOI: 10.1086/191654 Bibcode: 1992ApJS...79..285K Keywords: Emission Spectra; Line Spectra; Seyfert Galaxies; Astronomical Spectroscopy; Balmer Series; Charge Coupled Devices; H Alpha Line; H Beta Line; Astrophysics; GALAXIES: INDIVIDUAL NAME: ARAKELIAN 120; GALAXIES: SEYFERT; LINE: PROFILES full text sources ADS | data products SIMBAD (6) NED (1) MAST (1) Related Materials (1) Erratum: 1992ApJS...82..445K

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)

Photometry of F-K type bright giant and supergiants. II - Calibration on indices in terms of luminosity reddening and abundance of F-type stars

view Abstract Citations (11) References (25) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Photometry of F-K Type Bright Giants and Supergiants. II. Calibration of Indicies in Terms of Luminositiy Reddening and Abundance of F-Type Stars Eggen, Olin J. Abstract The intermediate band and H photometry of bright giants and supergiants of type F, given in Paper I, is used to obtain values of age, surface gravity, reddening, lumin6sity, and heavy element abundance of these stars. The few supergiants in galactic clusters are used to test the results. The bulk of the stars have ages between iO and 108 yr on the timescale dictated by the convective overshoot models, and have [Fe/H] between - 0.05 and 0.15 dex. Publication: The Astronomical Journal Pub Date: November 1991 DOI: 10.1086/116007 Bibcode: 1991AJ....102.1826E Keywords: F Stars; Giant Stars; K Stars; Stellar Luminosity; Stellar Spectrophotometry; Supergiant Stars; Abundance; Galactic Clusters; H Beta Line; Stellar Gravitation; Astronomy; STARS: SUPERGIANTS; STARS: LUMINOSITIES; STARS: ABUNDANCES full text sources ADS | data products SIMBAD (225) Related Materials (2) Part 1: 1992AJ....103.1381E Part 3: 1994AJ....107.2184E

Optical spectroscopy of Magellanic Cloud planetary nebulae. II

view Abstract Citations (82) References (31) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Optical Spectroscopy of Magellanic Cloud Planetary Nebulae. II. Meatheringham, Stephen J. ; Dopita, Michael A. Abstract We present optical spectroscopy in the range 3300-7800 A for a total of 37 planetary nebulae in the LMC and seven in the SMC. Together with the objects from the first paper in this series, we now have accurate emission-line intensities down to a few percent of Hβ for 77 nebulae in the Magellanic Clouds. Agreement with other authors is excellent. Reddening estimates from Balmer line ratios have been determined, and the line intensities have been dereddened accordingly. Nebular [O III] electron temperatures, and where measurable [S II] densities, are derived. [O II] electron densities are recalculated using appropriate electron temperatures. The [S II] and [O II] electron densities correlate well, with n_e_( [O II]) > n_e_([S II]). Zanstra temperatures are derived for 22 objects possessing detectable stellar continua. These temperatures are in agreement with photoionization modeling of this sample. Publication: The Astrophysical Journal Supplement Series Pub Date: August 1991 DOI: 10.1086/191592 Bibcode: 1991ApJS...76.1085M Keywords: H Beta Line; Interstellar Extinction; Magellanic Clouds; Optical Emission Spectroscopy; Planetary Nebulae; Balmer Series; Emission Spectra; Line Spectra; Astrophysics; GALAXIES: MAGELLANIC CLOUDS; NEBULAE: PLANETARY full text sources ADS | data products SIMBAD (45) NED (2) CDS (2) Related Materials (2) Catalog: 1996yCat..20761085M Part 1: 1991ApJS...75..407M

Early type high-velocity stars in the solar neighborhood. IV - Four-color and H-beta photometry

view Abstract Citations (78) References (59) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Early Type High-velocity Stars in the Solar Neighborhood. IV. Four-color and HA Photometry Stetson, Peter B. Abstract Results are presented from photometric obaservations in the Stromgren uvby four-color and H-beta systems of early-type high-velocity stars in the solar neighborhood. Several types of photometrically peculiar stars are selected on the basis of their Stromgren indices and are provisionally identified as peculiar A stars, field horizontal-branch stars, metal-poor stars near the Population II and old-disk turnoffs, metal-poor blue stragglers, or metallic-line A stars. Numerous photometrically normal stars were also found. Publication: The Astronomical Journal Pub Date: August 1991 DOI: 10.1086/115895 Bibcode: 1991AJ....102..589S Keywords: Early Stars; Solar Neighborhood; Stellar Spectrophotometry; H Beta Line; Metallic Stars; Milky Way Galaxy; Peculiar Stars; Star Clusters; Astrophysics; STARS: EARLY-TYPE full text sources ADS | data products SIMBAD (817) GCPD (1) Related Materials (3) Part 1: 1981AJ.....86.1337S Part 2: 1981AJ.....86.1882S Part 3: 1983AJ.....88.1349S

Spectroscopic measurements of the parameters of the ablation clouds of deuterium pellets injected into tokamaks

Spectroscopic measurements have been made of the parameters of the luminous cloud surrounding deuterium pellets injected into the Princeton Large Torus (PLT) [Phys. Rev. Lett. 55, 1398 (1985)] and the Tokamak Fusion Test Reactor (TFTR) [Plasma Physics and Controlled Nuclear Fusion Research (IAEA, Vienna, 1987), Vol. 1, p. 171], with the measurements on the latter described formally here for the first time. The electron densities determined from the Stark broadening of the Balmer alpha and beta lines ranged from 5×1015–1×1018 cm−3, while the temperatures obtained from the line to continuum intensity ratios and the ratio of the intensities of the Balmer alpha and beta lines ranged from 0.9 to 3 eV. Balmer alpha emission powers as high as 100 kW were measured. The electron temperature (1.5±0.2 eV) and density (3±1×1017 cm−3 ) at the time of maximum emission from intact pellets were essentially the same for the two tokamaks, although the volumes of both the discharges and the pellets were roughly ten times larger in TFTR than in PLT. The data were taken in Ohmically heated plasmas, except for a limited number of discharges in PLT with low-power (approximately half the Ohmic heating power) ion cyclotron heating for which the results are the same as with Ohmic heating alone. Various factors that may influence the results of measurements of this type are discussed, including self-absorption, low-density plasma surrounding the most intense region of an ablation cloud, fluctuations in the emission intensity, and non-Maxwellian electron distributions. The results of the present experiments are similar to measurements of the pellet cloud parameters in other machines.

H-beta photometry of V1010 Ophiuchi

view Abstract Citations (16) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS H-Beta Photometry of V1010 Ophiuchi Corcoran, M. F. ; Siah, M. J. ; Guinan, E. F. Abstract An analysis is presented of previously unpublished intermediate and narrow band H-beta light curves of the short period eclipsing binary V1010 Oph. The temperature of the primary is determined directly by comparing the UV continuum with Kurucz model atmospheres and solve the broadband lightcurve using the Wilson-Devinney program. The present solution has the primary filling its Roche lobe while the secondary is detached from its lobe. An asymmetry in the light curve in which first quadrature (0.25 P) is brighter than the second quadrature (0.75 P) may be the result of local heating of the inner surface of the secondary by mass transfer from the primary. The present semidetached solution indicates that the system is probably evolved. Publication: The Astronomical Journal Pub Date: May 1991 DOI: 10.1086/115810 Bibcode: 1991AJ....101.1828C Keywords: Astronomical Photometry; Eclipsing Binary Stars; H Beta Line; Light Curve; Ophiuchi Clouds; Stellar Evolution; Stellar Systems; Astrophysics; STARS: INDIVIDUAL; STARS: ECLIPSING BINARIES full text sources ADS | data products SIMBAD (1)

A comparison of C IV and H-beta broad emission-line profiles in low-redshift active galactic nuclei

view Abstract Citations (29) References (41) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Comparison of C IV and H beta Broad Emission-Line Profiles in Low-Redshift Active Galactic Nuclei Corbin, Michael R. Abstract Recently published IUE spectra of low-redshift QSOs and Seyfert 1 galaxies have permitted a comparison of the profiles of the C IV λ1549 and Hβ broad emission lines. A linear correlation between the FWHM values of the profiles has been found in a sample of 19 objects and is verified to not be the result of separate correlations between these parameters and luminosity. Interpreted in terms of the geometry of the broad-line region, this result is contrary to models which predict low-ionization line emission from an optically thick, geometrically thin accretion disk surrounding the central object. Current evidence favors a model in which broad-line emission arises predominantly in a stratified ensemble of clouds moving radially relative to the central continuum source. Publication: The Astrophysical Journal Pub Date: April 1991 DOI: 10.1086/186000 Bibcode: 1991ApJ...371L..51C Keywords: Active Galactic Nuclei; Emission Spectra; H Beta Line; Hydrogen Clouds; Luminous Intensity; Red Shift; Quasars; Seyfert Galaxies; Spectral Line Width; Astrophysics; GALAXIES: NUCLEI; LINE PROFILES; QUASARS full text sources ADS | data products SIMBAD (23) NED (19) MAST (1)

On the emission-line response to continuum variations in the Seyfert galaxy NGC 5548

view Abstract Citations (52) References (4) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the Emission-Line Response to Continuum Variations in the Seyfert Galaxy NGC 5548 Netzer, Hagai ; Maoz, Dan Abstract Recently, two intensive optical monitoring projects were carried out, with the aim of measuring the continuum and emission line variations in the Seyfert galaxy NGC 5548. The two groups, observing the galaxy during two different periods, reported apparently contradicting results for the delay of Hβ variations with respect to the continuum. Using the UV measurements of Clavel et al., obtained the same year as one of the above data sets, we show that the emission-line lag behind continuum variations depends on the continuum variability time scale in this object, in the sense that continuum variations with larger time scales give larger emission-line lags. Since the continuum variability time scales are different in the data sets obtained by the two groups, so are the derived lags. Such an effect can arise in some thick BLR geometries, especially if the line response to the ionizing flux changes is nonlinear. Using Monte Carlo simulations, we show that even without resorting to a nonlinear response, there is at least one possible model that could reproduce the two differing delays. In view of the effect, we note that previously reported differences in the lags of various emission lines are uncertain. In particular, we find that, using only the largest outburst in the simultaneous optical and UV light curves, Lyα, C IV λ1549, and Hβ all have similar lags behind the continuum. Publication: The Astrophysical Journal Pub Date: December 1990 DOI: 10.1086/185875 Bibcode: 1990ApJ...365L...5N Keywords: Continuous Radiation; Emission Spectra; Line Spectra; Seyfert Galaxies; H Beta Line; Light Curve; Monte Carlo Method; Ultraviolet Radiation; Astrophysics; GALAXIES: INDIVIDUAL NGC NUMBER: NGC 5548; GALAXIES: SEYFERT full text sources ADS | data products SIMBAD (2) NED (1) MAST (1)

An observational study of millimeter-wave recombination lines

view Abstract Citations (30) References (28) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS An Observational Study of Millimeter-Wave Recombination Lines Gordon, M. A. ; Walmsley, C. M. Abstract Observations of H36-alpha, He36-alpha, H40-alpha, He40-alpha, H44-beta, He44-beta, H45-beta, H50-beta, H50-gamma, H56-delta, H57-gamma, and H60-epsilon radio recombination lines in the 2 and 3 mm telluric windows made with the IRAM 30 m telescope on Pico Veleta, Spain are presented. Sources observed were the H II regions W3, NGC 1976, NGC 2024, Sgr B2, M17, W49, and DR 21. The observations are consistent with non-LTE models based upon centimeter-wave observations. The millimeter-wave recombination lines show no substantive indication of excitation by Lyman line radiation from nearby exciting stars so that conventional departure coefficients may be used with confidence. However, small departures from the expected line ratios have been found in some cases which merit additional investigation. Publication: The Astrophysical Journal Pub Date: December 1990 DOI: 10.1086/169514 Bibcode: 1990ApJ...365..606G Keywords: H Ii Regions; H Lines; Interstellar Matter; Millimeter Waves; Radio Sources (Astronomy); Recombination Reactions; Electron Energy; Emission Spectra; H Alpha Line; H Beta Line; H Gamma Line; Line Spectra; Radio Astronomy; Astrophysics; INTERSTELLAR: MATTER; NEBULAE: H II REGIONS; RADIO SOURCES: LINES full text sources ADS | data products SIMBAD (10)

The weak magnetic field of the AP star Epsilon Ursae Majoris

view Abstract Citations (28) References (22) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Weak Magnetic Field of the AP Star Epsilon Ursae Majoris Bohlender, David A. ; Landstreet, J. D. Abstract High-SNR circular polarization measurements in the wings of H-beta have been obtained for the bright A0pCr star Epsilon UMa, throughout its 5.0887-d rotation period. These data suggest that Epsilon UMa possesses an approximately dipolar magnetic field with magnetic extrema of +128 and -64 G. If the inclination of the rotation axis of the star is in the range i = 65 + or - 15 deg, then the obliquity of the magnetic field axis to the rotation axis is between 19 and 84 deg. The observations are compared with recent Doppler imaging studies of the surface abundances of Epsilon UMa. Publication: The Astrophysical Journal Pub Date: July 1990 DOI: 10.1086/185771 Bibcode: 1990ApJ...358L..25B Keywords: A Stars; Magnetic Stars; Peculiar Stars; Stellar Magnetic Fields; Circular Polarization; H Beta Line; Magnetic Field Configurations; Magnetic Flux; Stellar Rotation; Stellar Spectra; Astrophysics full text sources ADS | data products SIMBAD (1)

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 unusual outburst spectra of the cataclysmic variable IP Peg

view Abstract Citations (18) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Unusual Outburst Spectra of the Cataclysmic Variable IP Peg Piche, Francois ; Szkody, Paula Abstract Spectra are presented for the cataclysmic varible IP Peg for the period while the system was reaching the peak of an outburst. The average characteristics of the spectra are discussed and the orbital parameters are solved using the emission line profiles. The line profile evolution during and outside of the eclipse is examined and changes in the intensity of the continuum and the emission lines are studied as a function of phase. Also, the emission from the red dwarf secondary is discussed. Publication: The Astronomical Journal Pub Date: December 1989 DOI: 10.1086/115292 Bibcode: 1989AJ.....98.2225P Keywords: Cataclysmic Variables; Dwarf Novae; Stellar Spectra; Accretion Disks; Balmer Series; Emission Spectra; H Beta Line; Light Curve; Spectral Line Width; Astrophysics; STARS: INDIVIDUAL; STARS: DWARF NOVAE full text sources ADS | data products SIMBAD (1)

Toward a classification scheme for broad-line profiles in active galactic nuclei

view Abstract Citations (56) References (44) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Toward a Classification Scheme for Broad-Line Profiles in Active Galactic Nuclei Sulentic, Jack W. Abstract A study has been made of the broad-line Hβ profile in quasars and Seyfert galaxies. All objects from the Palomar Bright Quasar Survey (PBQS; Schmidt and Green) catalog with published spectral scans have been included toward a goal of determining broad-line characteristics in a complete sample of active galactic nuclei (AGNs). The principal motivation for this study was to determine the range of spectral shifts exhibited by the broad lines relative to the narrow ones. We propose a simple classification scheme for broad-line Hβ that would note the presence of systematic line shifts and line asymmetries. We investigate two samples of AGNs: (1) 25 objects from the PBQS and (2) a less well defined sample of 36 objects selected from various literature sources. Together these samples represent virtually all published spectra accurate enough to be reliably classified in our system. Combining the two samples (n = 61) we find: (a) only nine objects show symmetric and unshifted profiles; (b) a large number (15) of displaced profiles are symmetric, with redshifts twice as common as blue ones; (c) 35 objects show a measurable wavelength shift relative to the narrow-line region [O III] (from 120 to 1900 km s^-1^), with redshifts (20) slightly more common than blueshifts; (d) a shifted profile is very unlikely to show a blue asymmetry (red asymmetries are 8 times more common); and (e) 37 objects show an asymmetric profile with red (27) ones almost three times as common as blue. The distribution of wavelength centroids at all four measured profile heights (allowing for a few outliers) is displaced ~100 km s^-1^ toward the red. This can be interpreted as evidence for a small gravitational redshift in most AGNs. Publication: The Astrophysical Journal Pub Date: August 1989 DOI: 10.1086/167684 Bibcode: 1989ApJ...343...54S Keywords: Active Galactic Nuclei; Astronomical Spectroscopy; Line Spectra; Spectrum Analysis; H Beta Line; Quasars; Red Shift; Seyfert Galaxies; Sky Surveys (Astronomy); Astrophysics; GALAXIES: SEYFERT; LINE PROFILES; QUASARS full text sources ADS | data products SIMBAD (59) NED (59)