Emmanouel Danezis

The far UV spectrum of the Be star AX Monocerotis

In this paper we study the main features of the far UV spectrum of the binary star AX Mon, observed with the IUE satellite at phase 0.568.Ions indicating a large range of ionization stages, going fromCi,Oi,Ni toSiv,Civ,Nv are present.The spectrum is dominated by shell absorption lines of Feii, Feiii, Siiii,Cii, Alii, Mgii and Niii.Two satellite components are clearly indicated in all these lines except for Niii which presents only one. Their mean velocities are +10±5 km s−1, −75±10 km s−1, and −260±15 km s−1.Red emission wings are observed in the Mgii resonant doublet at 2800 Å, which shows a P Cygni profile. Each of the absorption lines of the Mgii doublet is formed by a narrow component, which is blended with the Mgii interstellar line and a broad component, which shows a complex structure.Broad and asymmetrical profiles are observed for the Siiv,Civ, andNv resonance lines with blue edge velocities about −700±30 km s−1.

SACs And DACs Phenomena In The Atmospheres Of Hot Emission Stars

In the spectra of many Oe and Be stars we observe complex profiles in the lines of many ions. The observed features are the composition of a number of absorption components. This fact is interpreted by the existence of independent density formations in the region, where a specific ion line is created. These density regions rotate and move radially with different velocities and so they create components with different widths and radial shifts. We name these components Satellite Absorption Components (SACs or DACs). In this paper we present the model proposed by Danezis et al. (2003), which describes the structure of these density regions. With this method we can calculate the apparent rotational (Vrot) and expansion/contraction radial velocities (Vexp) of these density regions, as well as an expression of the optical depth (ξ). Also we present three applications to the spectra of hot emission stars.

Similarity Between DACs/SACs Phenomena in Hot Emission Stars and Quasars Absorption Lines

In the spectra of Hot Emission Stars and AGNs we observe some peculiar profiles that result from dynamical processes such as accretion and/or ejection of matter from these objects. In this paper we indicate that DACs and SACs phenomena, can explain the spectral lines peculiarity in Hot Emission Stars and AGNs. We also try to connect the physical properties of absorption regions around stars and quasars.

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.

The Complex Structure of the Mg II

Here we consider the presence of absorption components shifted to the violet or red side of the main spectral line (satellite or discrete absorption components, i.e., SACs or DACs) in the regions of the Mg II resonance lines in Be stars a sw ell as their kinematical characteristics. Namely, our objective is to check whether there exists a common physical structure for the atmospheric regions creating SACs or DACs of the Mg II resonance lines. In order to do this, a statistical study of the Mg II �� 2795.523, 2802.698 u A lines in the spectra of 64 Be stars of all spectral subtypes and luminosity classes was performed. We found that the atmospherical absorption regions where the Mg II resonance lines originated may be formed of several independent density layers of matter that rotate with different velocities. It was also attempted to separate SACs and DACs according to low or high radial velocity. The emission lines were detected only in the earliest and latest spectral subtypes.

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The spectra of Hot Emission Stars and AGNs present peculiar profiles that result from dynamical processes such as accretion and/or ejection of matter from these objects. In this paper we analyze DACs and SACs phenomena, which indicate the existence of layers of matter with different physical conditions and we propose that these phenomena can explain the spectral lines peculiarity in Hot Emission Stars and AGNs. We also propose a new model with which we can study the density regions in the plasma surrounding the studied objects, where DACs and SACs of a spectral line are created producing the observed peculiar profiles. Finally, we present some tests to justify the proposed model.

2795.523, 2802.698

Here we will present some spectroscopic methods for emission gas research in the emission line region of Active Galactic Nuclei (AGNs): (1) We will demonstrate the possibility to use the Boltzmann‐plot method to estimate the physical conditions in the broad line regions (BLRs); (2) We will discuss the applicability of so called “Gaussian method” for spectral line shape investigation of narrow line regions (NLRs) and BLRs; (3) We will present a method to fit the line profiles with a kinematically complex model. We apply a two‐component model assuming that the line wings originate in a very broad line region (VBLR) and the line core in an intermediate line region (ILR) of AGNs. The VBLR is assumed to be an accretion disk and the ILR a spherical emission region; (4) Also, a model for fitting of the broad absorption lines in quasars will be discussed.

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A detailed list and analysis of line identifications of five UV spectra of the RS CVn-type binary system TY Pyxidis are presented. These spectra are recorded at different phases with the International Ultraviolet Explorer (IUE). Two of them are in the wavelength rangeλλ1235–1950 Å while the other three in the rangeλλ2700–3110 Å.The far-UV spectrum of TY Pyx is mainly an emission spectrum dominated by the emission lines of the ions:Ci, Oi, Cii, Siii, Heii, Alii, and Feiii. We also pointed out the existence of a Feiii [34] line in absorption.The UV spectrum between 2700–3110 Å is dominated by weak absorption lines. Two satellite components are indicated for many lines, which correspond to the two stars of the system, in the two out of the three spectra (LWP 13386 and LWP 13347).Violet emission wings are observed for Fei [1], Tii [1],Oiv [1], and Siiii [1]. The UV spectrum of TY Pyx is also characterized by the multi-structure of Mgii [1] resonance lines.

Regions of 64 Be Stars

In this paper, we give a detailed list and analysis of line identifications of the UV spectrum of the Be star 88 Her in the wavelength range λλ1958–3002 Å recorded in 1984, 23 May with the International Ultraviolet Explorer (IUE). The spectrum is crowded by shell absorptions lines, mostly those of singly ionized iron peak elements.The detailed analysis of the radial velocities measured in the whole spectral range 1100–3002 Å is also given.