Emission Lines Of Ca Research Articles

Activity and Secondary Minimum of RZ Eridani

RZ Eridani is an eclipsing binary star with Algol-type light curve of rather long period of 39.28 days. As this star exhibits emission lines of Ca 11 H and K it was classified also as RS CVn type. RZ Eri has been occasionally observed with the GENEVA photometric system with 40cm and later 70cm Swiss telescope at La Silla, Chile, since 1977 mainly for obtaining a complete light curve and for detecting the secondary minimum. The observation showed, that the brightness outside minima really varies as the RS CVn stars usually do. The secondary minimum has been detected at the phase 0.67. Apart from that, the variation of the brightness outside the minima occasionally drops for a short time (about one day or even less). These drops may be due to rotation and uneven distribution of active regions on the surface of the secondary or by the gas streams between the two components. The variation of the light outside minima is certainly not caused by the primary component, because such jumps in the brightness were detected during the total eclipse, when the primary component is not visible. This star certainly deserves more both photometric and spectroscopic attention. Preliminary search for periodicities by G. Burki showed that apart from the orbital period no other periods within the range of days are present. Further details will be published later elsewhere.

High-density gas in bipolar outflow sources and active galactic nuclei

The highest density regions near the base of the outflow in young stellar objects with bipolar molecular outflows are discussed. Bright emission lines of Ca II and O I characterize the spectra and lead to estimates of n ~ 1010 cm−3, temperatures of a few thousand Kelvins, and mass motions of several hundred kilometres per second. Typically the rate of momentum transfer within this region fails by more than an order of magnitude to provide the force necessary to drive the molecular outflow on the parsec scale. The overall near-infrared spectra of these young stars are similar to those of certain active galactic nuclei having strong Fe II emission.A comparison is made between the Ca II and O I lines in the infrared core source of the bipolar H II region S106 and in the Seyfert galaxy Mrk 42. The spectra are shown to be scaled versions of each other, and we conclude that the physical conditions are broadly similar in the high-density emission-line regions of these two objects. The Ca II lines appear self-reversed in both objects, but possible Ca II absorption in the underlying galaxy in Mrk 42 compromises the detailed comparison of line shapes. Nevertheless, it is likely that the geometries and velocity fields are also analogous. Derived parameters of the emission-line regions in S106 and the Seyfert galaxies I Zw 1 and Mrk 42 are compared.

Emission lines of Mg II and Ca II in planetary nebulae

Conditions of excitation of the emission resonance lines of ionized magnesium and calcium in planetary nebulae are analyzed. The allowed lines are excited by the same mechanism as the forbidden lines and not by ordinary fluorescence. An emission line lambda 2800 Mg II of reasonable strength can be observed in the spectra of planetary nebulae of medium excitation, but not in highly excited nebulae. The absence of the H and K emission lines of Ca II in the spectra results from their expected intensity which is 3 to 4 orders of magnitude lower than the intensity of the line lambda 2800 Mg II or H(beta) of hydrogen.

The Velocity-Curve of XY Leonis.

view Abstract Citations (17) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Velocity-Curve of XY Leonis. Struve, O. ; Zebergs, V. Abstract Spectrograms of XY Leonis taken in January, 1959, show double absorption lines corresponding to two K0-type stars in a W Ursae Majoris type system; = -20 km/sec, K1 = 135 km/sec, K2 = 170 km/sec. The spectrum shows double narrow emission lines of Ca ii belonging to the approaching star of larger mass. There are no emission lines belonging to the receding star of smaller mass. At the opposite elongation the receding star of larger mass and the approaching star of smaller mass each has a single Ca ii emission line. The widths of the individual emission components are always much smaller than the widths of the corresponding absorption components. Publication: The Astrophysical Journal Pub Date: July 1959 DOI: 10.1086/146704 Bibcode: 1959ApJ...130..137S full text sources ADS | data products SIMBAD (1)

H and K Emission in Late-Type Stars: Dependence of Line Width on Luminosity and Related Topics.

view Abstract Citations (423) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS H and K Emission in Late-Type Stars: Dependence of Line Width on Luminosity and Related Topics. Wilson, O. C. ; Vainu Bappu, M. K. Abstract The H and K emission lines of Ca II have been studied on 10-A/mm spectrograms of 185 stars of types G, K, and M. Nearly all stars of type G0 or later in the list of MK standards (Johnson and Morgan 1953) have been included. Emission-line widths have been measured, as well as displacements of the emission and absorption components. Tb e displacements are determined with respect to nearby low-excitation reversing- layer absorption lines. When the logarithms of the emission-line widths (corrected for instrumental width) are plotted against the Yerkes absolute spectroscopic magnitudes, the points define a straight line which extends over a 15-mag. range of Mv and which indicates that the line width varies as the one-sixth power of the luminosity. Stars with weak or strong lines and of all spectral types later than G0 seem to fit the linear relationship equally well. The widths therefore cannot be dependent upon line intensity or stellar surface temperature. Evidence from the solar spectrum, from ζ Aurigae, from Hyades stars, and from four visual binaries point to the conclusion that the relationship described here is not of a statistical nature. Therefore, it is probable that the Ca II emission-line widths can be used as luminosity indicators. Internal consistency considerations indicate that one good spectrogram should fix the absolute magnitude of any late-type star with suitable lines to within ±05 mag. It is found that,for displacements within ±6 km/sec, negative values are more frequent than positive for the emission components of H and K. On the other hand, between +4 and -4 km/sec, positive values are more common for the absorption components. The naive interpretation is that the emitting layer is rising and that the absorbing material is falling slowly inward. Statistics of the larger displacements common among the intrinsically luminous stars are discussed briefly. In particular, it is found that among the M-type giants and supergiants the negative displacements of the absorption components are not correlated with absolute magnitude. Publication: The Astrophysical Journal Pub Date: May 1957 DOI: 10.1086/146339 Bibcode: 1957ApJ...125..661W full text sources ADS | data products SIMBAD (184) Related Materials (1) Commentary: 1999ApJ...525C.776L