The distortion of line profiles and velocities in the spectra of contact binaries.

view Abstract Citations (31) References (28) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Detection of radio recombination-line emission from the Rho Ophiuchi dark cloud. Brown, R. L. ; Knapp, G. R. Abstract Recombination-line observations in the direction of the p Oph dark cloud at 21 cm are described in which we have detected the carbon 166a and 167a lines. The excellent agreement between the velocity of these lines and the velocity of molecular lines from the p Oph cloud lead to an unequivocal identification of the regions of recombination-line emission with the dark cloud itself. The velocity width of the recombination lines Av = 2.4 km 1 is comparable with the widths of the CO and OH lines, indicating that the line must arise in cold gas. The emission measure of the line, 0.2 cm -6 pc, is sufficiently large as to require that the line originate in regions with densities n > 630 cm 2 From these observations, together with an analysis of the H I selfabsorption feature seen in the same direction, we infer that the relative electron density in the line-emitting regions of the cloud is ne/n <: 1.6 x 10- . Subject headings: molecules, interstellar - nebulae - radio lines - 21-cm radiation Publication: The Astrophysical Journal Pub Date: April 1974 DOI: 10.1086/152796 Bibcode: 1974ApJ...189..253B full text sources ADS | data products SIMBAD (3)

view Abstract Citations (7) References (33) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Line Variability and the Broad Emission Line Region of Quasi-stellar Objects. III. Line Profiles and Velocity Field Zheng, Wei Abstract In the study of emission line variability, the emission line profiles of low-redshift QSOs during their spectral variations are compared to study the dynamical structure of their emission-line regions. Data indicate that, at time intervals of ~ 1 yr, net changes generally have similar line widths, and no significant asymmetry is found in most cases. For the QSO 0736+017, Hβ was considerably broader when the QSO was brighter. In the QSO 0026+129, Hβ was blueshifted by 350 km s^-1^ during its variation between 1977 and 1978, but this difference diminished in 1985. This suggests that a fraction of emitting gas exists in a remote region of more than 1 lt-yr from the center. A binary supermassive system may also be an explanation. A redshift of 700 km s^-1^ is found between Hβ and narrow lines. This places an upper limit on the gravitational field. If the real size of the broad line region of 0026+129 is 1 lt-month; a rough estimate of its central mass is derived to be 10^9^ M_sun_. Publication: The Astrophysical Journal Pub Date: October 1988 DOI: 10.1086/166735 Bibcode: 1988ApJ...333..188Z Keywords: Emission Spectra; Line Spectra; Quasars; Spectral Line Width; Binary Stars; Gravitational Fields; Red Shift; Supermassive Stars; Astrophysics; LINE PROFILES; QUASARS full text sources ADS | data products SIMBAD (7) NED (7) Related Materials (2) Part 1: 1987ApJ...322..164Z Part 2: 1988ApJ...324..801Z

view Abstract Citations (25) References (32) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Microturbulence in A stars as derived from line profiles. Smith, M. A. Abstract This study represents an attempt to fix a scale of the "microturbulent velocity" in main-sequence A stars by examining the profiles of weak and saturated lines of six sharp-lined Am stars. Although the study is photographic, so that it is difficult to determine accurate core and wing parameters, studies of the loci of half-intensity widths and core shapes provide useful information. If a total broadening due to rotation and microturbulence is chosen on the basis of agreement between observed and computed intermediate-strength lines, it is found that the strongest lines are narrower and deeper than predicted by an amount that is proportional to the measured metallic-line blocking coefficients. If the strong-line cores were influenced strongly by departures from LTE, this effect would not be expected. After also testing explicitly for non-LTE in strong-line cores, it is concluded that LTE blanketed atmospheres are probably adequate to describe the formation of the spectral lines of the strengths studied. The blanketing effect seriously hampers, however, the uniqueness of the determination of the microturbulent component to the line broadening. From several lines of investigation, for example of the core shape of saturated lines, it appears that the microturbulence peaks to a value of not more than, but probably not much less than, 4 km 1, in mid- to late-A stars. One star shows a total broadening of 4 km i, and its projected rotational velocity is apparently negligible. Our present estimate disagrees with our previously determined peak value of 7 km 1 determined from curve of growth studies. An analysis of the possible error sources indicates that the discrepancy is mainly due to a combination of errors in the Corliss and Warner scale of oscillator strengths and to probably high equivalent-width scale due to the intermediate (8-9 A mm -1) coude' dispersion used. This work is actually a pilot study in that relatively precise photoelectric data are needed to describe the microturbulent velocity scale unambiguously. Even then, the question of LTE departures and the effect of blanketing on the temperature stratification is intimately tied to the scale of "microturbulence." Subject headings: line formation - line profiles - turbulence Publication: The Astrophysical Journal Pub Date: May 1973 DOI: 10.1086/152127 Bibcode: 1973ApJ...182..159S full text sources ADS | data products SIMBAD (9)

view Abstract Citations (21) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Application of Fourier analysis to broadening of stellar line profiles. I. Three Mn stars. Smith, M. A. ; Parsons, S. B. Abstract This paper explores a modified form of Gray's technique of determiriing classical microturbulence (T) by Fourier analysis of line profiles. The technique entails the transformation of the functions defined by absorption-line scans to Fourier power spectra. Our instrumental resolution of 0.05 A does not reduce the strength in the first side- lobe of the power spectra appreciably. Thus the sidelobe power is suitable as a basic criterion in the comparison of computed and observed line profiles. Our study for three Mn Ap stars shows that the formal errors placed on the solution for T are most sensitive to limited photon statistics, to the choice of whether rotation (V) or macroturbulence (M) is dominant in broadening the line, and to the total amount of this broadening. On the other hand the solution for T is insensitive to the damping parameter, the model atmosphere, and the assumption of LTE. We demonstrate that the Fourier technique provides a more convenient and precisely defined test of the value of T than would be obtained from direct comparison of line profiles. For CrB we obtain T=0'iifV=4km s-1,orT= +ffM=3 km -1 ,wefind0 T 3, with V = 12. These results do not contradict the statement that both forms of turbulence may be zero. In themselves they do not exclude atmospheric difflision as the mechanism responsible for abundance anomalies in Mn stars. An unexpected discovery made in this study is that all three strong lines observed in L CrB show a depression in their blue wings displaced in velocity -91 1 km s: 1 from the centers. This effect is not instrumental, and it appears unlikely to be caused by a secondary star. The implication is that some hitherto unsuspected mass motions are occurring at the top of the atmospheres or over a small area of these stars. However, it is not yet clear how any such effect can be reconciled with the solutions obtained for low or zero turbulences in the line-formation regions of the atmospheres. Subject headings: atmospheres, stellar - line profiles - peculiar A stars - rotation, stellar - turbulence Publication: The Astrophysical Journal Supplement Series Pub Date: August 1975 DOI: 10.1086/190348 Bibcode: 1975ApJS...29..341S Keywords: A Stars; Fourier Analysis; Line Spectra; Manganese; Metallic Stars; Spectral Line Width; Absorption Spectra; Abundance; Atmospheric Diffusion; Continuous Spectra; Graphs (Charts); Power Spectra; Stellar Atmospheres; Stellar Rotation; Stellar Spectra; Astrophysics full text sources ADS | data products SIMBAD (3)

view Abstract Citations (51) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Photoelectric Profile Measurements of Halpha and Hbeta in be Stars Gray, David F. ; Marlborough, J. M. Abstract We present photoelectric measurements of Ha and H in 14 Be stars. We find from a shape analysis of the wings of Ha that a Gaussian broadening mechanism is reasonable whereas a damping profile is not. It is suggested on this basis that the width and shape of Ha can be reasonably interpreted as a combination of shell rotation and electron scattering. Subject headings: Be stars - line profiles - rotation, stellar Publication: The Astrophysical Journal Supplement Series Pub Date: March 1974 DOI: 10.1086/190291 Bibcode: 1974ApJS...27..121G full text sources ADS | data products SIMBAD (15)

view Abstract Citations (13) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Nova Delphini 1967. II. Physical properties and element abundances in the nebular state. Robbins, R. R. ; Sanyal, A. Abstract Physical properties of the nebulosity of Nova Delphini 1967 during its "nebular" stages are derived from high dispersion spectra taken during the period 1967 July to 1969 August. The electron temperature and electron density were determined from the ratio of auroral to nebular line intensities of [0 iii] and [N ii]. During the summer of 1969, values on the order of Te = 13,300K and Ne = 1.74 x 106 cm-3 were obtained. In addition, on certain dates it was possible to determine a separate electron temperature for different components of the [0 iii] line profile; that is, for different ejections of the nova. We have determined the oxygen and helium abundances for the nebulosity. The ratio N(O)/N(H) is approximately solar, in conflict with earlier determinations for this object, while N(He)/N(H) 0.20 by number; the oxygen determination is in agreement with recent calculations by Sparks et al. Some possible reasons for earlier determinations of oxygen over-abundance are discussed. The existence of self-absorption in the He0 spectrum is noted. From Hfl photometry, the mass of the nebula is determined to be 2.9 x 1030 g, or less if there is self-absorption in the Ba1mer spectrum. A classification of emission lines by shape is carried out, and a discussion of one aspect of line intensity variations with time is carried out, namely, a comparison with time of the ratio of [0 iii] A5007 intensities between the two principal ejections. Subject headings: line profiles - nebulae: individual - stars: novae Publication: The Astrophysical Journal Pub Date: February 1978 DOI: 10.1086/155863 Bibcode: 1978ApJ...219..985R Keywords: Abundance; Nebulae; Novae; Stellar Spectra; Electron Density (Concentration); Electron Energy; Emission Spectra; H Lines; Helium; Line Spectra; Oxygen Spectra; Astrophysics; Element Abundances:Novae; Envelopes:Novae; Line Profiles:Novae; Nova HR Delphini; Nova Delphini 1967 full text sources ADS | data products SIMBAD (1) Related Materials (1) Part 1: 1974ApJS...28..115S

view Abstract Citations (37) References (26) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Observations of some early-type supergiants with variable Halpha profiles. Rosendhal, J. D. Abstract Study of multiple high-dispersion Ha spectrograms of 20 early-type supergiants indicates that 13 of these stars showed large, visually evident changes in the strength or structure of the Ha as well as in the strength of other prominent lines in the red region of the spectrum. These stars should be suitable candidates for investigating possible coupling between mass loss and turbulence. Techniques previously used for studying this problem can be extended to earlier spectral types by using the Si ii lines AA6347, 6371, the C ii lines AA6578, 6582 `and the He ilines AA5876, 6678 as turbulence indicators. Subject headings: emission-line stars - line profiles - luminous stars - mass loss Publication: The Astrophysical Journal Pub Date: June 1973 DOI: 10.1086/152160 Bibcode: 1973ApJ...182..523R full text sources ADS | data products SIMBAD (20)

view Abstract Citations (52) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS An analysis of ultraviolet resonance lines and the possible existence of coronae in O stars. Olson, G. L. Abstract A method for analyzing resonance line profiles is developed to determine the degree of ionization and the spatial distribution of ions in stellar winds. This technique is a two-parameter adaptation of the Sobolev approximation for line transfer. Families of line profiles are presented for two velocity laws, several radial dependences of the ionization, and the full range of ionic abundance. These profiles can be applied to interpreting observed resonance lines of any wavelength and oscillator strength in any star through simple scaling laws. The star Puppis (O4f) is analyzed in this manner to determine the ionic structure of its wind. This ionic structure is then compared to that predicted by a model consisting of a cool wind with a thin hot (T 5 x 106 K) corona at the base of the flow. This model is proposed as an alternative to "warm" wind models, which require electron temperatures near 200,000 K, to explain the high ionization potential ions such as O+ that are observed. Even though the coronal radiation is attenuated by the opacities of all the abundant elements, enough hard photons penetrate to produce O+ by the Auger process throughout the stellar wind. The coronal size required to fit the observed ionic structure of Pup has an emission which is very close to the X-ray upper limits set by the ANS satellite. Limits on the gas temperature and the radiation temperature in the far-UV can be obtained through this analysis. Subject headings: line profiles - stars: coronae - stars: early-type - stars: winds - ultraviolet: spectra Publication: The Astrophysical Journal Pub Date: November 1978 DOI: 10.1086/156592 Bibcode: 1978ApJ...226..124O Keywords: Line Spectra; O Stars; Stellar Coronas; Stellar Winds; Ultraviolet Spectra; Abundance; Optical Resonance; Optical Thickness; Plasma Composition; Plasma Temperature; Radial Velocity; Stellar Models; Astrophysics; Line Profiles:O Stars; O Stars:Stellar Coronae; O Stars:Stellar Winds; O Stars:UV Spectra full text sources ADS | data products SIMBAD (1)

view Abstract Citations (9) References (18) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Halpha polarization and line profiles in white dwarfs with strong magnetic fields. Borra, E. F. Abstract Ha circular polarization and intensity profiles in white dwarfs with strong magnetic fields are computed for dipole and dipole-like configurations of the magnetic field. The polar fields vary from 4 x 10 to 108 gauss. The profiles are severely distorted by the strong nonhomogeneous fields. They are strongly dependent on field strength and magnetic geometry. An interesting and potentially very useful feature of the profiles is the appearance of sharp a + (red) components. The wavelength location of those components is fairly insensitive to field strength: either they are not there or they are at the correct wavelength. This makes them useful in identifying Ha in magnetic white dwarfs. The intensity and polarization spectra of known magnetic white dwarfs are examined in the light of the models. Subject headings: line profiles - polarization - stars: magnetic - stars: white dwarfs - Zeeman effect Publication: The Astrophysical Journal Pub Date: November 1976 DOI: 10.1086/154785 Bibcode: 1976ApJ...209..858B full text sources ADS | data products SIMBAD (8)

view Abstract Citations (17) References (12) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Observations of the profile of the Ca II infrared triplet line lambda 8498 in late-type stars. Anderson, C. M. Abstract The profiles of the Ca ii infrared triplet line A8498, observed at a resolution (FWHM) of 0.28 A for 28 stars of spectral type F8 and later, are presented. Although there does not appear to be any correlation of line parameters with the strength of the emission observed in the H- and K-lines, the profile is clearly sensitive to the luminosity of the star. Subject headings: Ca ii emission - late-type stars - line profiles - luminosities - spectra, infrared Publication: The Astrophysical Journal Pub Date: June 1974 DOI: 10.1086/152914 Bibcode: 1974ApJ...190..585A full text sources ADS | data products SIMBAD (29)

This study broadens our comprehensive investigation of total-eclipse W Ursae Majoris-type contact binaries by analyzing eight additional systems, continuing our previous research. Multiband BV R c I c photometric data were obtained at an observatory in Mexico, from which new times of minima were determined. All target systems also had available space-based Transiting Exoplanet Survey Satellite time-series data. Orbital period variations were studied for eight target systems, showing either linear or parabolic trends. The target systems exhibiting parabolic trends demonstrated a sustained decrease in their orbital periods over time. We modeled the light curves utilizing the PHOEBE Python code in combination with the BSN application. We revisited the relationship between orbital period and the temperature of the hotter component in contact binary systems using an empirical approach. Our analysis identified a clear break at P = 0.27 day, separating the systems into two distinct groups for orbital periods shorter than 0.6 day. Following the determination of stellar extinction, absolute parameters for seven systems were estimated employing parallax measurements from Gaia DR3. Based on the components’ effective temperatures and masses, the systems were classified into A- and W-subtypes. Their evolutionary states were illustrated using mass–radius and mass–luminosity diagrams.

view Abstract Citations (11) References (7) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A model for P Cygni based on the He I spectrum. Oegerle, W. R. ; van Blerkom, D. Abstract Recent work on the interpretation of hydrogen emission lines from P Cygni has led to contradictory models of its atmosphere. In order to resolve the problem, we have constructed a model for He i emission in an accelerating envelope. The statistical equilibrium equations are solved at several points in the envelope using a 36 level neutral helium atom with continuum and the escape probability method to simplify the transfer of radiation. The resulting line profiles agree quite well with the observed lines for a mass loss rate of 2 x 10-6 M0 yr -`. The unusual behavior of helium lines, noted by Adams and Merrill, in which absorption components of lines in the same series have quite different displacements from line center, is a natural consequence of our model. The evidence of the radial velocity-excitation potential relation together with our line profile results point strongly to an accelerating flow in the region of P Cygni's envelope where the He I spectrum is formed. Subject headings: line profiles - stars: atmospheres - stars: circumstellar shells - stars: emission-line Publication: The Astrophysical Journal Pub Date: September 1976 DOI: 10.1086/154626 Bibcode: 1976ApJ...208..453O full text sources ADS | data products SIMBAD (1)

view Abstract Citations (93) References (73) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Halpha variations in spectra of the brighter, northern Be stars. Slettebak, A. ; Reynolds, R. C. Abstract Photoelectric scans of Ha in the spectra of 35 bright Be stars accessible from Flagstaff, Arizona, were obtained during five observing periods in 1975-1977 with the Perkins 72 inch (1.8 m) reflector. Variations in total emission andlor line profile were detected for most of the stars on time scales of months. Evidence of variability from night to night and, in a few cases, during a night was also found, but the reality of such short-term changes is less certain. Subject headings: line profiles - stars: Be - stars : emission-line Publication: The Astrophysical Journal Supplement Series Pub Date: November 1978 DOI: 10.1086/190554 Bibcode: 1978ApJS...38..205S Keywords: Be Stars:Line Profiles; Emission-Line Stars:H Alpha full text sources ADS | data products SIMBAD (42)

view Abstract Citations (1) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Analysis of the profiles of the solar S I lines at 1807 and 1900 Å. Doherty, L. R. ; McAllister, H. C. Abstract High-resolution profiles of five lines of S I have been obtained from rocket echelle spectra of a quiet region near the solar limb ( = 0.3). Lines in the 1807 A multiplet show strong central reversals; the 1900 A lines are nearly Gaussian in shape. Profiles computed with the chromospheric model of Vernazza, Avrett, and Loeser agree well with the central parts of the reversed lines if the nonthermal motion at heights above 1000 km is taken to be macroturbulence. The 1900 A lines are formed near the temperature minimum, and their observed width of 40 mA implies a turbulent motion of less than 1.2km 1 Coherent scattering provides the best fit to the wings of the reversed lines. Thus the 5 11807 A multiplet provides further evidence for the importance of partial redistribution in the formation of strong chromospheric lines. Computed absolute intensities are less than those observed by more than a factor of 2. Changes in the model which reduce this discrepancy are discussed. Subject headings: line profiles - Sun: chromosphere - Sun: spectra - ultraviolet: spectra Publication: The Astrophysical Journal Pub Date: June 1978 DOI: 10.1086/156190 Bibcode: 1978ApJ...222..716D Keywords: Chromosphere; Fine Structure; Line Spectra; Solar Spectra; Spectrum Analysis; Sulfur; Ultraviolet Spectra; Aerobee Rocket Vehicle; Atmospheric Turbulence; Atomic Spectra; Rocket Sounding; Solar Atmosphere; Solar Limb; Solar Physics; Line Profiles:Solar Chromosphere full text sources ADS |

view Abstract Citations (29) References (7) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Harmonic Analysis of the Line Profiles of an Oblique Rotator Falk, Alfred E. ; Wehlau, William H. Abstract A method of determining the parameters of the oblique-rotator model from observed line profiles is presented. Advantages and disadvantages of this procedure compared with the harmonic analysis method described by Deutsch are discussed. To illustrate the method, analyses have been carried out on some lines in the spectrum of a2 CYn. The results are discussed briefly. It appears that the method works, and should provide better results when more accurate data are available. Subject headings: line profiles - magnetic stars - peculiar A stars Publication: The Astrophysical Journal Pub Date: September 1974 DOI: 10.1086/153072 Bibcode: 1974ApJ...192..409F full text sources ADS |