Evaggelia Lyratzi

A Statistical Study of Physical Parameters of the C IV Density Regions in 20 Oe Stars

We detected the presence of Satellite Absorption Components (SACs) which accompany the C IV resonance lines in the spectra of 20 Oe stars of different spectral subtypes, taken with IUE. The values of the apparent rotational and radial velocities, the random velocities of the thermal motions of the ions, as well as the column density and the Full Width at Half Maximum (FWHM) of the independent regions of matter which produce the main and the satellites components of the studied spectral lines were calculated. The variations of these physical parameters are presented as a function of the spectral subtype.

Investigation of the Post‐Coronal Density Regions of Oe Stars, with the N V UV Resonance Lines

The presence of Satellite Absorption Components (SACs) in the N V resonance lines of 20 Oe stars of different spectral subtypes is considered. We calculated the values of the apparent rotational and radial velocities, the random ion velocities, as well as, the Full Width at Half Maximum (FWHM) and the column density of the independent regions of matter which produce the main and the satellites components of the studied spectral lines. We examine also the variations of these physical parameters as a function of the spectral subtype.

A Statistical Study of the Si IV Resonance Line Parameters in 19 Be Stars

Abstract Using the GR model, we analyze the ultraviolet Si IV resonance lines in the spectra of 19 Be stars of different spectral subtypes, in order to detect the presence of absorption components and to analyze their characteristics. From this analysis we can calculate the values of a group of physical parameters, such as the apparent rotational and radial velocities, the random velocities of the ion thermal motions, as well as the absorbed energy and the logarithm of the column density of the independent regions of matter which produce the main and the satellite components of the studied spectral lines.

The N IV Density Regions in the Spectra of 20 Oe Stars

The presence of Satellite Absorption Components (SACs) in the N IV spectral lines of 20 Oe stars of different spectral subtypes were analyzed and the physical parameters which characterize the corresponding N IV density regions were studied. We found that the N IV spectral lines consist of one or two Satellite Absorption Components. We calculate the values of the apparent rotational and radial velocities, the random ion velocities, as well as the Full Width at Half Maximum (FWHM), the absorbed energy and the column density of the independent regions of matter which produce the main and the satellite components of the studied spectral lines. Finally, we present the variations of these physical parameters as a function of the spectral subtype.

A New Model for the Structure of the DACs and SACs Regions in the Oe and Be Stellar Atmospheres

As it is already known, the spectra of many Oe and Be stars present Discrete Absorption Components (DACs) which, because of their profiles width as well as the values of the expansion / contraction velocities, they create a complicated profile of the main spectral lines. This fact is interpreted by the existence of two or more independent layers of matter, in the region where the main spectral lines are formed. Such a structure is responsible for the formation of a series of satellite components (DACs) for each main spectral line. In this paper we present a first approximation to a mathematical model reproducing the complex profile of the spectral lines of Oe and Be stars that present DACs. This model presupposes that the regions, where these spectral lines are formed, are not continuous but consist of a number of independent absorbing density layers of matter, followed by an emission region and an external general absorption region. When we fit the spectral lines that present DACs, with this model, we can calculate the values of the apparent rotation and expansion / contraction velocities of the regions where the DACs are formed.

Studying the UV Mg II Resonance Lines in 20 Be Stars

Abstract Using the GR model, we analyze the UV Mg II resonance lines in the spectra of 20 Be stars of different spectral subtypes, in order to detect the presence of satellite or discrete absorption components. The values of some physical parameters – rotational, radial and random velocities, as well as the FWHM and the absorbed energy, as a function of the effective temperature for the studied stars are determined.

Studying the complex BAL profiles in the BALQSOs spectra

Most of Broad Absorption Lines (BALs) in quasars (QSOs) present very complex profiles. This means that we cannot fit them with a known physical distribution. An idea to explain these profiles is that the dynamical systems of Broad Line Regions (BLRs) are not homogeneous but consist of a number of density regions or ion populations with different physical parameters. Each one of these density regions gives us an independent classical absorption line. If the regions that give rise to such lines rotate with large velocities and move radially with small velocities, the produced lines have large widths and small shifts. As a result they are blended among themselves as well as with the main spectral line and thus they are not discrete. Based on this idea we study the BALs of UV C IV resonance lines in the spectra of a group of Hi ionization Broad Absorption Line Quasars (Hi BALQSOs) using the Gauss- Rotation model (GR model).

A Study of the Structure of Different Ionization Potential Regions in the Atmosphere of AX Mon (HD 45910)

The complex structure and the peculiar profiles of some spectral lines are common in the UV spectrum of AX Mon (HD 45910). The observed peculiar profiles are composed by a number of SACs or DACs. In this paper, using the GR model, we study the complex profile of the Al II (λ 1670.81 A), Al III (λλ 1854.722, 1867.782 A), Mg II (λλ 2795.523, 2802.698 A), Fe II (λ 2586.876 A), C II (λλ 1334.515, 1335.684 A) and Si IV (λλ 1393.73, 1402.73 A) spectral lines. Additionally, we calculate the relation of some kinematical parameters of the regions that create the DACs/SACs of the studied lines with the ionization potential.

Kinematics of Broad Absorption Line Regions of PG 1254+047

In this paper we study the Lyα spectral line and the N V, Si IV and C IV resonance lines in the UV spectrum of the Broad Absorption Line Quasar (BAL QSO) PG 1254+047. We found that the studied Broad Absorption Lines (BALs) of this quasar are created by a number of Satellite Absorption Components (SACs). We calculated some kinematical parameters such as the apparent rotational (Vrot) and radial (Vrad) velocities of the regions where the studied lines are created and the random velocities (Vrand) of the studied ions.

Kinematical parameters in the coronal and post-coronal regions of the Oe stars

In this progress report we present the main results of our research. Using a new model we studied the kinematical parameters such as the random velocities of the ions, which create the spectral lines of C IV, N IV and N V in the spectra of 20 Oe stars, as well as the rotational and radial velocities of the regions, where the above ions are created. We calculated the values of the above parameters and we present the relations between them as well as their variation as function of the spectral subtype. We also present the random velocities of the ions for each one of the C IV, N IV and N V regions as a function of the photospheric rotational velocities. Finally, we propose an explanation for the large widths that we observe in the studied spectral lines, as these widths can not be explained as large rotational or random velocities.