A new model for the structure of the DACs and SACs regions in the Oe and Be stellar atmospheres

In this paper we present a new mathematical model for the density regions where a specific spectral line and its SACs/DACs are created in the Oe and Be stellar atmospheres. In the calculations of final spectral line function we consider that the main reasons of the line broadening are the rotation of the density regions creating the spectral line and its DACs/SACs, as well as the random motions of the ions. This line function is able to reproduce the spectral feature and it enables us to calculate some important physical parameters, such as the rotational, the radial and the random velocities, the Full Width at Half Maximum, the Gaussian deviation, the optical depth, the column density and the absorbed or emitted energy. Additionally, we can calculate the percentage of the contribution of the rotational velocity and the ions' random motions of the DACs/SACs regions to the line broadening. Finally, we present two tests and three short applications of the proposed model.Comment: 9 pages, 5 figures, accepted for publication in PAS

The complex structure of the Mg II {\lambda\lambda} 2795.523, 2802.698 {\AA} regions of 64 Be stars

Here is studied the presence of absorption components shifted to the violet or the red side of the main spectral line (satellite, or discrete absorption components, i.e. SACs or DACs), in Mg II resonance lines' regions in Be stars and their kinematical characteristics. Namely our objective is to check if 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 {\lambda \lambda} 2792.523, 2802.698 {\AA} lines in the spectra of 64 Be stars of all spectral subtypes and luminosity classes is performed. We found that the absorption atmospherical regions where the Mg II resonance lines originated may be formed of several independent density layers of matter which rotate with different velocities. It is attempted also 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.Comment: 18 pages, 12 figures, accepted for publication in PAS

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 lambda lambda 1393.755, 1402.778 angstrom Si IV resonance lines and we present the relation between some of these parameters and their variation as a function of the spectral subtype-

Studying the UV Mg II Resonance Lines in 20 Be Stars

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

Multicomponent Analysis of the UV Si IV and C IV Broad Absorption Troughs in BALQSO Spectra: The Examples of J01225 + 1339 and J02287 + 0002

Broad Absorption Line QSOs (BALQSOs) are a subtype of radio-quite QSOs that exhibit complex and unusually broad (FWHM ≥ 2,000 km/s) absorption lines. The existence of these lines in BALQSO spectra raises some questions with respect to the properties, the physical conditions and kinematics of the BAL material as well as the morphology of BAL troughs. In this study, taking into consideration the clumpy structure of the AGN outflow winds, we propose a physical model in order to explain the formation of BAL troughs and we give the mathematical description of this model. We also propose a method for analyzing spectroscopically the BAL profiles in the UV region of the electromagnetic spectrum. This method consists of the criteria we set during the fitting process of BAL troughs. The purpose of these criteria is to enable us to determine the exact number of components needed to simulate accurately the BAL troughs and guarantee the uniqueness of the fit. We give an application of the model and the method for Si IV and C IV resonance lines in the case of two BALQSOs. From the analysis, we conclude that the BAL material is in the form of clouds (density enhancements) that move radially and intercept the line-of-sight to the central continuum source. Using our method, we find the number of absorption components needed to simulate the BAL profiles, which means the number of clouds in the line-of-sight. We calculate the velocity shifts, the FWHM and the optical depths of the absorption components of BALs and we propose an internal structure for these clouds. Finally, we give some correlations between the properties of absorption components of Si IV and C IV. © 2015, Indian Academy of Sciences

Studying the UV Mg II resonance lines in 20 Be stars

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

Investigating the reasons of variability in Si IV and C IV broad absorption line troughs of quasars

In this paper we analyze the C IV and Si IV broad absorption troughs of two BALQSOs (J101056.69+355833.3, J114548.38+393746.6) to the individual components they consist of. By analyzing a BAL trough to its components we have the advantage to study the variations of the individual absorbing systems in the line of sight and not just the variations of the whole absorption trough or the variations of selected portions of BAL troughs exhibiting changes. We find that the velocity shifts and FWHMs (Full Width at Half Maximum) of the individual components do not vary between an interval of six years. All variable components show changes in the optical depths at line centers which are manifested as variations in the EW (Equivalent Width) of the components. In both BALQSOs, over corresponding velocities, Si IV has higher incidence of variability than C IV. From our analysis, evidence is in favour of different covering fractions between C IV and Si IV. Finally, although most of our results favour the crossing cloud scenario as the cause of variability, there is also strong piece of evidence indicating changing ionization as the source of variability. Thus, a mixed situation where both physical mechanisms contribute to BAL variability is the most possible scenario. © 2017, EDP Sciences, SIF, Springer-Verlag GmbH Germany

Some important notes on ASTA software: A new method of analysis of simple and complex emission and absorption spectral lines

ASTA is a new spectral analysis software aiming to serve the growing need of an integrated computing environment which will implement efficiently the demanding process of multicomponent analysis. It is a cutting-edge spectral multicomponent analysis software for displaying, fitting and analyzing astronomical spectra of complex emission and absorption line profiles. Equipped with statistical and verification tools it accelerates complex mathematical precision checks and confirms the uniqueness of the calculated physical parameters and the number of the absorption components that construct every Broad Absorption/Emission Line (BAL/BEL) and Discrete Absorption Components (DACs). DACs (in the case of Hot Emission Stars) and BALs/BELs (in the case of Quasars) are spectral lines of the same ion and the same wavelength as the main spectral line, shifted at different Δλ as they are created in different density regions which rotate and move radially with different velocities. The currently accepted view is that BELs, BALs and DACs may be due to a flow of many individual density enhancements, called clouds, cloudlets or clumps which are optically thick and very small compared with the size of the central continuum source. These density enhancements are not preexisting entities but are formed inside an unstable and turbulent wind and they are indicated by very complex profiles. According to this phenomenon, a prevailing view is that they are not simple absorption/emission lines, but the synthesis of a group of classical absorption line components of the same spectral line. ASTA software equipped with a multicomponent analysis model is a novel approach to curve fit these complex lines focusing on the physical representation of the calculated parameters of each of these components. The BAL Quasar SDSS J114548.38 + 393746.6 case study is analyzed to demonstrate the potential of ASTA, whereas the Quasar SDSS J000027.01 + 030715.5 narrow absorption line highlights the flexibility to analyze effectively simple spectral profiles. © 2018 Elsevier B.V

Interpreting the complex line profiles in the stellar spectra

In this review we present our recent investigation of the complex absorption lines in spectra of hot emission stars. The lines are created in a material ejected from stars (here we call it density regions around the objects). Particularly we present a model (GR model) which is developed to study satellite or discrete absorption components (SACs or DACs). Using the model we are able to extract kinematical parameters (rotational, radial and random velocity) and some physical parameters (full width at half maximum, optical depth in the center of the line, column density and absorbed or emitted energy) of the density regions. © 2009 Elsevier B.V. All rights reserved

A statistical study of the SiIV resonance line parameters in 19 be stars

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