Cygni-type Profiles Research Articles

Ultraviolet spectroscopy of the nova-like variable V3885 Sagittarii /= CD -42 deg 14462/

Low-dispersion long and short wavelength IUE spectra of the nova-like system V3885 Sgr were obtained on 1979 August 24 UT. The UV spectrum exhibits strong, high-temperature absorption lines of C III, C IV, He II, N IV, N V, and Si IV which all have relatively large negative velocities of 600-1000 km/s at their line centers. The C IV (1550 A) features shows a P Cygni-type profile with a blueshifted absorption line; the presence of the P Cygni-type feature strongly suggests a significant mass outflow from the system in the form of a hot stellar wind. The observed continuum fluxes are fitted with theoretical accretion disk model fluxes, and a tentative physical interpretation of the observed spectral properties is presented.

An escape probability treatment of doublet resonance lines in expanding stellar winds

When stellar winds have expansion velocities greater than the velocity separation between doublet line transitions, the line source function of the component with the longer wavelength depends on nonlocal values of the other component's source function. By using the Sobolev approximation and escape probability methods, the nonlocal radiative coupling for the case of spherically symmetric outflow with a monotonically increasing velocity can be solved explicitly and efficiently. This case is directly applicable to the doublet P Cygni type profiles observed in the ultraviolet spectra of O and B stars and leads to an improved determination of the line strengths. The nonlocal coupling also modifies the radiative forces that act on the mass outflow. Examples of how the nonlocal radiative coupling changes the line source functions, the line profiles, and the radiative forces are presented.

Radiative transfer in the co-moving frame

Solution of line-transfer equation in the co-moving frame, obtained on the basis of discrete space theory, has been employed to calculate the lines emerging from a rapidly expanding stellar atmosphere. The solution is found to be highly stable for large velocities of expansion with both positive and negative velocity gradients. We have presented profiles of spectral lines that are translated along the line of sight of the observer at infinity. We have treated a Non-LTE two-level atom in a medium scattering isotropically with line and continuum emission. P Cygni-type profiles noticed in a purely scattering medium.

A study of the MG II K line in Beta Persei

Spectral scans of the Mg II k line in Beta Per were obtained with Copernicus during two primary eclipses. A brief description of observation in a short frame mode is given. The observed data are compared with computed line profiles based on the eclipse geometry of spherical stars. It is shown that a nonuniform circumstellar envelope, or cloud, probably is present. In one scan, a red-shifted line of P Cygni-type profile appeared, indicating the occurrence of an unusual event in the close binary system.

Outflow of matter in the chromosphere of α Orionis

The spectrum of α Orionis is composite and consist of three components: 1) a photospheric spectrum characterized by symmetric absorption lines more or less typical of the spectrum of an M2 supergiant, except for their very great widths; 2) a shell spectrum consisting of P Cygnitype profiles of neutral and singly-ionized metallic lines of very low excitation potential; and 3) asymmetric absorption lines, including Hα Hβ , Fel lines of intermediate excitation potential and the infrared triplet of Ca+, which appear to be formed in a relatively warm layer, probably an extended chromosphere.

Effects of high velocities on photoionization lines

We have treated formation of spectral lines in a commoving frame where photoionization is predominant over collisional processes. We have assumed that the radiation field for causing photoionization is a function of Planck function. We have also considered the situation in which the continuum contributes to the radiation in the line. In all the models the quantityB/A (ratio of outer to inner radii) is kept equal to 10 and the total optical depth is taken to be 103. The velocity is assumed to be varying according to the lawdV/dτ ∼ 0) in the given shell. The velocities at the innermost radius (r =A) are set equal to 0 and at the outermost radius (r =B), the maximum velocities are taken to be 0, 1, 3 and 10 Doppler units. The calculated line profiles are those seen by an observer at infinity.P Cygni-type profiles are observed in the case of a medium with no continuum absorption. For a medium with continuum absorption double peaked asymmetric profiles are noticed when the velocities are small; the two emission peaks merge into a single asymmetric peak for larger velocities.

RETICON observations of the H-alpha P Cygni profiles of Zeta Orionis and Zeta Puppis

view Abstract Citations (6) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS RETICON observations of the H alf P CYG profiles of ZET ORI and ZET Pup. Ebbets, D. Abstract Observations obtained with a modern electronic detector provide line profiles with high photometric precision, good spectral resolution, and a carefully defined wavelength scale. The H-alpha lines in both stars have a P Cygni type profile, with emission visible on both sides of the absorption component. Previously undetected wings are found to extend to more than + or - 1000 km/s. The application of a simple modeling theory indicates that the wings cannot be attributed entirely to redistribution by noncoherent electron scattering, but reflect a smooth velocity law in the accelerating stellar wind. Publication: The Astrophysical Journal Pub Date: March 1980 DOI: 10.1086/157807 Bibcode: 1980ApJ...236..835E Keywords: Electron Scattering; H Alpha Line; O Stars; Stellar Spectra; Stellar Winds; Supergiant Stars; Early Stars; Electromagnetic Scattering; Incoherent Scattering; Stellar Mass Ejection; Stellar Spectrophotometry; Astrophysics full text sources ADS | data products SIMBAD (3)

Chemical Composition of Nova Cygni 1975

AbstractThe chemical composition of Nova Cygni 1975 was determined by a curve-of-growth analysis. A strong excess of helium and the CNO -group abundances and a normal Si abundance was found.Spectral observations of N Cyg 1975 were begun at the Crimean Astrophysical Observatory on 29 August 1975, at 18h 50m UT, one day before light maximum (Boyarchuk et al. 1977). Twelve spectrograms with a dispersion of 4,6 and 12 Å/mm were taken during this night. The spectral type of the Nova was B2 Ia+ and no emissions appeared in the spectrum. During the following night, 10 spectrograms were obtained. The spectral type of the Nova was A2 Ia+ qe, and strong emission lines with P Cygni-type profiles could be detected. Since absorption lines were not observed on 30 August, only the spectrograms taken on 29 August can be used for a curve-of-growth analysis.

Rocket Spectroscopy of Zeta Orionis.

Analysis of a spectrum of zeta Ori extending from 922 to 1453 A with approximately 0.8 A resolution recorded at rocket altitudes. All lines used in existing models of stellar atmospheres appear in the recorded spectrum with the exception of those masked by telluric N2 or strong P Cygni-type profiles and by an O V line at 1371.29 A. Fifteen multiplets of subordinate lines have been reliably identified, indicating an approximate range of excitation from 0 to 50 eV. Transitions in C III (1176 A), N III (991 A), N V (1239, 1243 A), O VI (1032, 1038 A), Si IV (1394, 1403 A), S IV (1063, 1074 A), and S VI (933, 944 A) have been observed as P Cygni-type profiles presumably arising in a circumstellar envelope. The degree of ionization, transitions present, and mean radial velocities are all consistent with viewing the envelope as a hot (about 100,000 K), rarefied plasma in which collisional ionization is important. Interstellar lines in C I (1277, 1280 A), C II (1036, 1334 A), N I (1134-1135 A), N I (1200-1201 A), N II (1084-1086 A), O I (1302, 1305 A), Si II (1190, 1193 A), Si II (1260 A), and Si II (1304 A) have been definitely identified. Other transitions in Ar II, S I, C I, and Fe II are tentatively identified. The equivalent width of the L alpha line is found to be 10.4 plus or minus 1.6 A, corresponding to a columnar density of 2.0 plus or minus 0.7 x 10 to the 20th per cu cm.

Influence of Noncoherent Electron Scattering on a Line Profile in Wolf-Rayet Stars

view Abstract Citations (48) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Influence of Noncoherent Electron Scattering on a Line Profile in Wolf-Rayet Stars Castor, J. I. ; Smith, L. F. ; van Blerkom, D. Abstract The 3483 line of N iv in the ?N 6 star RD 192163 is observed to have a P Cygni-type profile, except for the presence of very extensive emission wings. It is shown thatnoncoherent scattering by free electrons in the envelope can account for this profile. Publication: The Astrophysical Journal Pub Date: March 1970 DOI: 10.1086/150393 Bibcode: 1970ApJ...159.1119C full text sources ADS | data products SIMBAD (2)