E. Lyratzi

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.

The Peculiar Absorption And Emission Phenomena From Stars To Quasars

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.

Some Spectroscopic Methods for Astrophysical Plasma Research

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.

The The structure of the Si IV region in Be stars: a study of Si IV spectral lines in Be 68 stars

Using the GR model, we analyze the UV Si IV resonance lines in the spectra of 68 Be stars of different spectral subtypes, in order to detect the structure of Si IV region. We calculated the values of the rotational, radial and random velocities as well as the absorbed energy of each one of the λλ 1393.755, 1402.778 A Si IV resonance lines and we present the relation between some of these parameters and their variation as a function of the spectral subtype.

A New Modeling Approach For DACs And SACs Regions In The Atmospheres Of Hot Emissions Stars

The presence of Discrete Absorption Components (DACs) or Satellite Absorption Components (SACs) is a very common phenomenon in the atmospheres of hot emission stars (Danezis et al. 2003, Lyratzi & Danezis 2004) and result to the complex line profiles of these stars. The shapes of these lines are interpreted by the existence of two or more independent layers of matter nearby a star. These structures are responsible for the formation of a series of satellite components for each spectral line. Here we will present a model reproducing the complex profile of the spectral lines of Oe and Be stars with DACs and SACs (Danezis et al. 2003, Lyratzi & Danezis 2004). In general, this model has a line function for the complex structure of the spectral lines with DACs or SACs and include a function L that considers the kinematic (geometry) of an independent region. In the calculation of the function L we have considered the rotational velocities of the independent regions, as well as the random velocities within them. ...

Studying the complex absorption profiles of Si IV in 21 HiBALQSO spectra

We investigate the physical conditions and kinematics of broad absorption line region clouds of Si IV in 21 HiBAL Quasars. We use the Danezis et al. method [1], [2], [3] in order to fit and analyze the broad absorption troughs of Si IV resonance lines in the UV region of the electromagnetic spectrum. We find that the BAL flow is not smooth but instead plasma clouds are formed in it. BAL troughs present multicomponent structure which indicates the existence of more than one absorbing cloud in the line of sight, where every absorbing cloud produces a Si IV doublet. We show that the blending of these doublets produces the apparent broad absorption troughs we observe. One of our main achievements is that we managed to decompose and deblend each complex absorption trough to the individual doublets that it consists of. Apart from that, we succeeded in deblending the resonance lines of every doublet. By achieving accurate fits to the BAL troughs we calculated some physical and kinematical parameters that describe the plasma clouds in the line of sight. These parameters are: the radial outflow velocities of the clouds, the random velocities of ions inside each plasma cloud, the apparent optical depth in the center of every absorption component, the FWHM and the equivalent width. As a final step we correlate these physical parameters in order to draw useful conclusions.

The Complex Broad Absorption Line Profiles in a Sample of QSO Spectra

Abstract Most of the Broad Absorption Lines (BALs) in quasars show very complex profiles. An idea to explain these profiles is that the dynamical systems of broad line regions are not homogeneous but consist of a number of dense regions or ion populations with different physical parameters. This approach is used to study the ultraviolet CIV resonance lines in the spectra of a group of high ionization BAL quasars, using the Gauss-Rotation model.

DACs and SACs in the UV Spectrum of the Quasar PG 0946+301

In this paper we study the C IV and Si IV resonance lines in the UV spectrum of the Broad Absorption Line Quasar (BAL QSO) PG 0946+301. The studied Broad Absorption Lines (BALs) are mainly created by a number of Satellite Absorption Components (SACs). However, the C IV doublet of PG 0946+301 is one of the very few lines that present clearly the DACs phenomenon, in the case of quasars. We applied the GR model and we calculated the apparent rotational (Vrot) and radial (Vrad) velocities of the regions where the studied lines are created and the random velocities (Vrand) of the C IV and Si IV ions.

AX Mon (HD 45910) Kinematical Parameters in the Fe II Spectral Lines as a Function of the Excitation Potential

In the UV spectrum of AX Mon (HD 45910) we observe a series of spectral lines with complex structure and peculiar profiles. This peculiarity is due to SACs or DACs. In this paper, using the GR model, we study the complex profile of Fe II spectral lines and we calculate the relation of some kinematical parameters of the regions that create the DACs/SACs with the excitation potential.