hyper-ionization phenomena in the coronal and post- coronal regions in the oe stellar envelopes

Hyper-ionization phenomena in the coronal

and post- coronal regions in the Oe stellar

envelopes

An abstract of the PhD Thesis of

Dr. Antonios Antoniou

University of Athens, Faculty of Physics, Department of Astrophysics, Astronomy

and Mechanics, Panepistimioupoli, Zographou 157 84, Athens – Greece

Introduction The spectra of Hot Emission Stars (Oe and Be stars) present peculiar line

profiles. In order to explain this peculiarity, we propose and use the DACs (B.

Bates and D. R. Halliwell, Mon. Not. R. Astr. Soc. 223, 673-681, 1986) and SACs

(E. Danezis, D. Nikolaidis, E. Lyratzi, A. Antoniou, L. Č Popović, and M. S.

Dimitrijević, Mem. Soc. It. Suppl., 7, 107, 2005) theory.

In the case of hot emission stars, DACs or SACs arise from spherical density

regions surrounding the star or lying far away from it, that present spherical

(or apparent spherical) symmetry around the star or their own center (E.

Lyratzi, E. Danezis, L. Č. Popović and M. S. Dimitrijević, D. Nikolaidis and A.

Antoniou, PASJ, 59, 357, 2007).

The DACs phenomenon

In a stellar atmosphere, or disc, that we can detect around hot emission

stars, an absorption line can be produced in several density regions that

present the same temperature. From each one of these regions an absorption

line arises.

The line profile distribution of each one of these absorption components is a

function of a group of physical parameters, as the radial, the rotational, the

random velocities and the optical depth of the region that produces the

specific components of the spectral line.

These spectral lines are named Discrete Absorption Components (DACs)

when they are discrete (Bates, B. & Halliwell, D. R.: 1986, MNRAS, 223, 673).

DACs are discrete but not unknown absorption spectral lines. They are

spectral lines of the same ion and the same wavelength as a main spectral line,

shifted at different Δλ, as they are created in different density regions which

rotate and move radially with different velocities (Danezis, E., Nikolaidis, D.,

Lyratzi, V., Stathopoulou, M., Theodossiou, E., Kosionidis, A., Drakopoulos,

C., Christou G. & Koutsouris, P.: 2003a, A&SS, 284, 1119).

DACs are lines, easily observed, in the spectra of some Be stars, because the

regions that give rise to such lines, rotate with low velocities and move

radially with high velocities (E. Danezis, D. Nikolaidis, E. Lyratzi, A.

Antoniou, L. Č Popović, and M. S. Dimitrijević, Mem. Soc. It. Suppl., 7, 107,

2005).

In Fig. 1 we can see the Mg II spectral lines of two Be stars that present

DACs, in comparison with the Mg II lines of a classical B star. In these line

profiles we can see the main spectral lines and at the left of each one of them a

group of DACs.

Figure 1: The Mg II spectral lines of two Be stars that present DACs, in comparison with the

Mg II lines of a classical B star. Below the fit one can see the decomposition of the

observed profile to its DACs.

The SACs phenomenon

If the regions that give rise to the DACs, 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. In such a case the name Discrete

Absorption Components is inappropriate and we use only the name Satellite

Absorption Components (SACs) (E. Danezis, D. Nikolaidis, E. Lyratzi, A.

Antoniou, L. Č Popović, and M. S. Dimitrijević, Mem. Soc. It. Suppl., 7, 107,

2005).

In Fig. 2 it is clear that the Mg II line profiles of the star AX Mon (HD

45910), which presents DACs and the star HD 41335, which presents SACs are

produced in the same way. The only difference between them is that the

components of HD 41335 are much less shifted and thus they are blended

among themselves. The black line presents the observed spectral line's profile

and the red one the model's fit. We also present all the components which

contribute to the observed features, separately.

Figure 2: The Mg II line profiles of the star AX Mon (HD 45910), which presents DACs (left)

and the star HD 41335, which presents SACs (right). Below the fit one can see the

decomposition of the observed profile to its DACs and SACs respectively.

The proposed model Danezis, E., Lyratzi, E., Nikolaidis, D., Antoniou, A., Popović, L. Č. & Dimitrijević, M. S., 2007

PASJ, 59, 4.

Danezis, E., Lyratzi, E., Nikolaidis, D., Antoniou, A., Popović, L. Č. & Dimitrijević, M. S., SPIG

Kopaonik, Serbia, 2006.

In the case of DACs or SACs phenomenon we need to calculate the line

function of the complex line profile. We proposed a model in order to explain

the complex structure of the density regions of hot emission stars where the

spectral lines that present SACs or DACs are created (Danezis et al. 2003, 2005,

2007). We consider the area of gas, which creates a specific spectral line

consists of i independent absorbing shells followed by j independent shells

that both absorbs and emits and an outer absorbing shell. Such a structure

produces DACs or SACs (Danezis et al. 2003a) and the final line function is:

gg

gj

ejejej

i

iifinal LLSLFF

expexp1exp)()( 0

where: F(λ0) is the initial radiation intensity, Li, Lej, Lg: are the

distribution functions of the absorption coefficients kλi, kλej, kλg

respectively. Each L depends on the values of the apparent rotational

velocity as well as of the radial expansion/contraction velocity of the

density shell, which forms the spectral line (Vrot, Vexp), ds

s

0

is an

expression of the optical depth τ, where Ω is an expression of kλ, Sλej:

the source function, which, at the moment when the spectrum is taken,

is constant.

The above function does not depend on the geometry of the regions which

create the observed feature. This means that L may represent any distribution

which considers certain geometry, without changing anything in F(λ)..

In the used model we consider spherical symmetry and that the main

reason for the lines’ broadening is the rotation of the region where these lines

are created. So:

dz

zzRL

lab

lablab

0

0cos

cos1arctancos1arctancos

0

00 ,

where R is the radius of the spherical density region, λlab is the laboratory

wavelength of the spectral line produced by a particular ion and

c

Vz rotation

lab

rotation

0 , where Δλrotation is the radial displacement and Vrotation is

the apparent rotational velocity of the i density shell of matter.

As we know, in order to find the mechanism responsible for the structure of

DACs or SACs density regions we need to calculate the values of a group of

parameters, such as the rotational, the random and the radial velocities, the

FWHM, the optical depth, the absorbed or emitted energy, the column

density, and the Gaussian standard deviation, as well as the relation among

them.

Directly from the model we can calculate the apparent radial velocities

(Vrad) of the absorbing or emitting density regions, the Gaussian standard

deviation (σ) of the random thermal motions distribution, the apparent

rotational velocities (Vrot) of the absorbing or emitting density region and the

optical depth (ξ) in the center of the spectral line.

From the above parameters we can calculate, the percentage contribution

(G%) of the random velocities to the broadening of the spectral line, the Full

Width at Half Maximum (FWHM), the random velocities of the ions (Vrand)

that produce the spectral lines, the absorbed or emitted energy (Εa, Ee) and

the column density (CD).

We point out that with the proposed model we can study and reproduce

specific spectral lines. This means that we can study specific density regions in

the plasma surrounding the studied object.

In this PhD Thesis we present a statistical study of C IV, N IV and N V

regions in the spectra of 20 Oe stars, as well as the time scale variations of the

C IV, N IV, N V and Si IV density regions in the HD 149757 and HD 93521

stellar atmospheres.

A statistical study of C IV, N IV and N V regions in the spectra

of 20 Oe stars

In Table 1 we present the studied stars. As we know it is not possible to find

stars between O0 and O3 spectral subtypes.

TABLE 1. The Studied Stars

Star Spectral subtype Star Spectral subtype

HD24534 O9.5 III HD57061 O9.0I

HD24912 O7.5 III ((f)) HD60848 O8.0Vpe

HD34656 O7 II (f) HD91824 O7V((f))

HD36486 O9.5 II HD93521 O9.5II

HD37022 O6 Vp HD112244 O8.5Iab

HD47129 O7.5 III HD149757 O9V(e)

HD47839 O7 III HD164794 O4V((f))

HD48099 O6.5 V HD203064 O8V

HD49798 O6p HD209975 O9.5I

HD57060 O8.5If HD210839 O6.0I

The random velocities of the layers as a function of the photospheric

rotational velocities. Antoniou, A., Danezis, E., Lyratzi, E., Nikolaidis, D., Popović, L. Č., Dimitrijević, M. S. VI

Serbian Conference on Spectral Line Shapes in Astrophysics Sremski Karlovci, Serbia, June, 2007.

With our model we calculated the random velocities of the layers that

produce the C IV, NIV and NV satellite components in the spectra of 20 Oe

stars, with different photospheric rotational velocities. The ionization potential

of each studied ion, for all the studied stars, is the same, so the respective

random velocities will be the same. As the values of the random velocities do

not depend on the inclination of the rotational axis, we expect similar average

values of the random velocities for each component for all the studied stars.

In Figs 3, 4 and 5 we present the relation between the random velocities of

the ions that create the C IV, N IV and N V lines in the spectra of 20 stars as a

function of the photospheric rotational velocities of the studied stars

Figure 3: The random velocities (Vrand) of the ions in the C IV regions that produce the

satellite components as a function of the apparent photospheric rotational velocities (Vphot).

We detect similar average values of the random velocities for each component for all the

studied stars

Figure 4: The random velocities (Vrandom) of the N IV regions that produce the satellite

components as a function of the apparent photospheric rotational velocities (Vphot). We

detect similar average values of the random velocities for each component for all the studied

stars

N IV regions (Gaussian way)

Random Velocities for the 2nd component

0

200

400

600

800

1000

0 50 100 150 200 250 300 350 400

Vphot (km/s)

Vra

nd

(k

m/s

)


Random Velocities for the 1st component

0

200

400

600

800

1000

0 50 100 150 200 250 300 350 400

Vphot (km/s)

Vra

nd

(k

m/s

)

C IV regions

Random Velocities for the 4th component

0

200

400

600

800

1000

0 100 200 300 400 500

Vphot (km/s)

Vra

nd

(k

m/s

)

C IV regions

Random Velocities for the 3rd component

0

200

400

600

800

1000

0 100 200 300 400 500

Vphot (km/s)

Vra

nd

(k

m/s

)

C IV regions


0

200

400

600

800

1000

0 100 200 300 400 500

Vphot (km/s)

Vra

nd

(k

m/s

)

C IV regions


0

200

400

600

800

1000

0 100 200 300 400 500

Vphot (km/s)

Vra

nd

(k

m/s

)

mean Vrandom = 160 km/s mean Vrandom = 115 km/s



Figure 5: The random velocities (Vrand) of the N V regions that produce the satellite

components as a function of the apparent photospheric rotational velocities (Vphot). We

detect similar average values of the random velocities for each component for all the studied

stars

Important remark: As we see, we detect similar average values of the

random velocities for each component, for the C IV, N IV and N V regions, for

all the studied stars. The above results, taken with our model agree with the

theory. This agreement between theory and calculations is a favourable test

for our model.

Studding the rotational velocities of the density layers of matter Antoniou, A., Danezis, E., Lyratzi, E., Nikolaidis, D., Popović, L. Č., Dimitrijević, M. S., &

Theodosiou, E., SPIG, Kopaonik, Serbia, 2006.

Antoniou, A., Danezis, E., Lyratzi, E., Nikolaidis, D., Popović, L. Č., Dimitrijević, M. S., VI


In the Figs 6, 7 and 8 we present the ratio Vrot/Vphot of the C IV, N IV and

N V components as a function of the photospheric rotational velocity (Vphot).

This ratio indicates how much the rotational velocity of the specific layer that

construct the specific component is higher than the apparent rotational

velocity of the star (Vrot=Rotational Velocity of the studied density region).



0

200

400

600

800

1000

0 50 100 150 200 250 300 350 400

Vphot (km/s)

Vra

nd

(k

m/s

)

N V regions (Rotational way)


0

200

400

600

800

1000

1200

1400

0 100 200 300 400 500

Vphot (km/s)

Vra

nd

(k

m/s

)


Figure 6: The ratio Vrot/Vphot of the four detected components of C IV as a function of the

photospheric rotational velocity (Vphot).

Figure 7: The ratio Vrot/Vphot indicates how much the rotational velocity of the specific N IV

layer is higher than the apparent rotational velocity of the star

N IV regions

Vrot/Vphot for the 2nd component

0,00

0,50

1,00

1,50

2,00

2,50

3,00

100 120 140 160 180 200 220 240

Vphot (km/s)

Vro

t/V

ph

ot

N IV regions

Vrot/Vphot for the 1st component

0,00

1,00

2,00

3,00

4,00

5,00

6,00

7,00

70 120 170 220 270 320 370 420

Vphot (km/s)

Vro

t/V

ph

ot max (Vrot/Vphot) = 6 max (Vrot/Vphot) = 2.5

C IV regions

Vrot/Vphot for the 3rd component

0,00

1,00

2,00

3,00

4,00

5,00

6,00

7,00

0 100 200 300 400 500

Vphot (km/s)

Vro

t/V

ph

ot

C IV regions


0,00

5,00

10,00

15,00

20,00

25,00

30,00

0 100 200 300 400 500

Vphot (km/s)

Vro

t/V

ph

ot

C IV regions


0,00

5,00

10,00

15,00

20,00

25,00

30,00

35,00

40,00

0 100 200 300 400 500

Vphot (km/s)

Vro

t/V

ph

ot

C IV regions

Vrot/Vphot for the 4th component

0,00

1,00

2,00

3,00

4,00

5,00

6,00

0 100 200 300 400 500

Vphot (km/s)

Vro

t/V

ph

ot

max (Vrot/Vphot) = 40


max (Vrot/Vphot) = 6 max (Vrot/Vphot) = 6

Figure 8: The ratio Vrot/Vphot indicates how much the rotational velocity of the specific N V

layer is higher than the apparent rotational velocity of the star

Relations among some physical parameters Danezis, E., Antoniou, A., Lyratzi, E., Popović, L. Č., Dimitrijević, M. S., VI Serbian Conference

on Spectral Line Shapes in Astrophysics Sremski Karlovci, Serbia, June, 2007.

In Figures 9-13 we present the relations among some physical parameters of

the C IV, N IV and N V regions.

Figure 9: Relation of the Gaussian standard deviation (σ) (left) and the rotational velocity

(Vrot) (right) with the radial velocity (Vrad) of the density regions which create the C IV

resonance lines.

N IV regions

Vrot/Vphot for the 3rd component

0,00

5,00

10,00

15,00

20,00

25,00

30,00

0 100 200 300 400 500

Vphot (km/s)

Vro

t/V

ph

ot

N IV regions


0,00

5,00

10,00

15,00

20,00

25,00

30,00

35,00

40,00

0 100 200 300 400 500

Vphot (km/s)

Vro

t/V

ph

ot

N IV regions


0,00

10,00

20,00

30,00

40,00

50,00

0 100 200 300 400 500

Vphot (km/s)

Vro

t/V

ph

ot

max (Vrot/Vphot) = 45 max (Vrot/Vphot) = 40


Figure 10: Relation of the Column Density (CD) (left) and the optical depth in the center of the

line (ξ) (right) with the radial velocity (Vrad) of the density regions which create the C IV

resonance lines.

Figure 11: Relation of the Gaussian standard deviation (σ) (left) and the Column Density (CD)

(right) with the radial velocity (Vrad) of the density regions which create the N IV spectral line.

Figure 12: Relation of the Gaussian standard deviation (σ) (left) and the Column Density (CD)

(right) with the radial velocity (Vrad) of the density regions which create the N V resonance

lines.

Figure 13: Relation between the rotational velocity (Vrot) and the radial velocity (Vrad) of the

density regions which create the N V resonance lines.

The variation of the physical parameters in the C IV, N IV and

N V regions of 20 Oe stars, as a function of the spectral subtype Antoniou, A., Danezis, E., Lyratzi, E., Nikolaidis, D., Popović, L. Č., Dimitrijević, M. S., &

Theodosiou, E., XXVIth IAU General Assembly, Prague, August, 2006.

Antoniou, A., Danezis, E., Lyratzi, E., Nikolaidis, D., Popović, L. Č., Dimitrijević, M. S., &

Theodosiou, E., SPIG, Kopaonik, Serbia, September, 2006.



The study of the C IV density region

In Fig. 14a,b we present the variation of the mean radial velocities (Fig. 14a)

and the mean rotational velocities (Fig. 14b) obtained from the C IV resonance

lines (λλ 1548.155, 1550.774 Å) for the independent density regions of matter

which create the 2, 3, 4 or 5 SACs as a function of the spectral subtype. In the C

IV regions we detect four groups of radial velocities, with mean values -2066

km/s, -1743 km/s, -1235 km/s, -469 km/s and -80 km/s.

We detect the same phenomenon in the case of the rotational velocities with

mean values 1458 km/s, 821 km/s, 251 km/s, 133 km/s and 65 km/s.

Figure 14a,b. Variation of the mean radial velocities (left) and the rotational velocities (right)

of the independent density regions of matter which create the 2, 3, 4 and 5 SACs of the C IV

resonance lines (λλ 1548.155, 1550.774 Å) as a function of the spectral subtype.

In Fig. 15a,b we present the variation of the mean random velocities of the

ions (Fig. 15a) and the Full Width at Half Maximum (FWHM) (Fig. 15b) of the

2, 3, 4 and 5 SACs of the C IV resonance lines (λλ 1548.155, 1550.774 Å), as a

function of the spectral subtype. There are also four groups of the random

velocities, with mean values 187 km/s, 163 km/s, 130 km/s, 108 km/s and 56

km/s. For the FWHM we detect the same phenomenon with values 13.0 Å, 6.2

Å, 2.2 Å, 1.2 Å and 0.4 Å.

Figure 15a, b. Variation of the mean random velocities of the ions (left) and the FWHM (right)

of the C IV resonance lines (λλ 1548.155, 1550.774 Å) for the independent density regions of

matter which create the 2, 3, 4 and 5 SACs as a function of the spectral subtype

In Fig. 16a,b we present the variation of the Column Density (CD) in 1010

cm-2 for the C IV resonance lines (λ 1548.155 Å in Fig. 16a and λ 1550.774 Å in

Fig. 16b), for the independent density regions of matter which create the 2, 3, 4

or 5 satellite components in all the stars of our sample, as a function of the

spectral subtype. We detect four groups of the column densities, with values

5.6 ×1010 cm-2, 4.5 ×1010 cm-2, 3.6 ×1010 cm-2, 2.6 × 1010 cm-2 and 1.2× 1010 cm-2. We

note that each component of both of the resonance lines presents the same

variation.

Figure 16a, b. Variation of the Column Density (CD) in 1010 cm-2 of the C IV resonance line λ

1548.155 Å (left) and λ 1550.774 Å (right) for the independent density regions of matter which

create the 2, 3, 4 or 5 satellite components as a function of the spectral subtype.

The study of the N IV density region

In Fig. 17a,b we present the variation of the mean values of the radial

velocities (Fig. 17a) and the random velocities of the thermal motions of the

ions (Fig. 17b), for the N IV independent density regions of matter (SACs)

which create the 1 or 2 satellite components of the N IV spectral line (λ 1718.8

Å), as a function of the spectral subtype. In the N IV region we detect two

groups of radial velocities. The first has values between -350 and -150 km/s

and the second about -70 km/s. In the case of the random velocities we

detected also two groups: the first has values between 350 and 220 km/s and

the second between 150 and 50 km/s.

Figure 17a,b: Variation of the radial velocities (left) and the random ion velocities (right) of

the N IV spectral line (λ 1718.8 Å) for the independent density regions of matter which create

the 1 or 2 SACs as a function of the spectral subtype.

In Fig. 18 we present the variation of the Full Width at Half Maximum

(FWHM), of the 1 or 2 satellite components of the N IV spectral line (λ 1718.8

Å), as a function of the spectral subtype. We detected two groups of values.

The first has values between 5 and 3 Å and the second between 2 and 1 Å.

Figure 18: Variation of the mean value of the Full Width at Half Maximum (FWHM) of the 1

or 2 SACs of the N IV spectral line, as a function of the spectral subtype.

In Fig. 19a,b we present the variation of the absorbed energy (Ea) in eV (Fig.

19a) and the column density (CD) in 1010 cm-2 (Fig. 19b) of the N IV

independent density regions of matter, which create the 1 or 2 satellite

components of the N IV spectral line (λ 1718.8 Å), as a function of the spectral

subtype.

We detected two groups of values of the absorbed energy. The first has

values between 2 and 1.2 eV and the second between 0.6 and 0.4 eV.

We found the same for the column density. The first group has values

between 4.5×1010 cm-2 and 3× 1010 cm-2 and the second has a constant behavior

with values about 2.5×1010 cm-2.

Figure 19a, b: Variation of the absorbed energy (Ea) in eV (left) and the column density (CD)

in cm-2 (right) of the N IV spectral line (λ 1718.8 Å) for the independent density regions of

matter which create the 1 or 2 satellite components as a function of the spectral subtype.

The study of the N V density region

In Fig. 20a,b we present the variation of the mean values of the radial

velocities (Fig. 20a) and the rotational velocities (Fig. 20b), of the N V

independent density regions of matter which create the 1, 2 or 3 satellite

components for each of the N V resonance lines (λλ 1238.821, 1242.804 Å), as a

function of the spectral subtype.

In the N V region we detect two groups of radial velocities. The first one

has values between -2300 and -1500 km/s and the second between -500 and -

100 km/s.

We detect the same phenomenon in the case of the rotational velocities with

values between 1800 and 1100 km/s for the first and between 400 and 200 km/s

for the second group.

Figure 20a,b: Variation of the radial velocities (left) and the rotational velocities (right) of the

independent density regions of matter which create the 1, 2, 3 and 4 SACs of the N V

resonance lines (λλ 1238.821, 1242.804 Å) as a function of the spectral subtype.

In Fig. 21a,b we present the variation of the random velocities of the

thermal motions of the ions (Fig. 21a) and the Full Width at Half Maximum

(FWHM) (Fig.21b), of the 1, 2 or 3 satellite components of the N V resonance

lines (λλ 1238.821, 1242.804 Å), as a function of the spectral subtype.

There are two groups of values of the random velocities. The first has

values between 400 and 200 km/s and the second between 150 and 80 km/s.

We detect the same phenomenon for the FWHM, with values between 18

and 10 Å for the first and between 6.0 and 2.0 Å for the second group.

Figure 21a, b: Variation of the mean random velocities of the thermal motions of the ions (left)

and the Full Width at Half Maximum (FWHM) (right) of the 1, 2, 3 and 4 SACs of the N V

resonance lines (λλ 1238.821, 1242.804 Å), as a function of the spectral subtype.

In Fig. 22a,b we present the variation of the Column Density (CD) in 1010

cm-2 for the independent density regions of matter which create the 1, 2 or 3

satellite components of the N V resonance lines (λ 1238.821 Å in Fig. 22a and λ

1242.804 Å in Fig. 22b), in all the stars of our sample, as a function of the

spectral subtype. We detect also two groups of the values of the column

density. The first has values between 5 ×1010 cm-2 and 3 ×1010 cm-2 and the

second about 2.5 × 1010 cm-2.

Figure 22a,b: Variation of the Column Density (CD) in 1010 cm-2 of the N V resonance line at λ

1238.821 Å (left) and λ 1242.804 Å (right) for the independent density regions of matter which

create the 2, 3, 4 or 5 satellite components as a function of the spectral subtype.

Long term variability of the coronal and post-coronal regions of

the Oe star HD 149757 (zeta Oph) Antoniou, A, Danezis, E., Lyratzi, E., Nikolaidis, D., Popović, L. Č. & Dimitrijević, M. S., PASJ

(submitted July 2007).



Here we present a part of the study of the C IV, N IV and N V regions

through the variation of kinematical parameters, such as the apparent

rotational and radial velocities, as well as the random velocities of the thermal

motions of the ions.

The study of the C IV density region

In Fig. 23a,b we present the time-scale change of the apparent rotational

and radial velocities of the independent density regions of matter, which

create the 2 satellite components of the C IV resonance lines (λλ 1548.155,

1550.774 Å).

In the case of the rotational velocities (Fig. 23a) and in the years 1980, 1981,

1990, 1991, relatively low values of about 300 km/s correspond to the spectra

that we fit with the Gaussian way. This means that for these spectra the main

reason for the line broadening is the random ion motions. All the rest spectra

were fitted with the Rotational method, i.e. the main reason for the line

broadening is the rotation of the region which creates the respective

component. Apart from these values, we see a constant behavior of the

apparent rotational velocities with values of about 1400 km/s for the first

component and about 950 km/s for the second one. The marks x and +

correspond to the spectra in which the best fit has been obtained with the

Gaussian method. In the case of the radial velocities (Fig. 23b) we detect also a

constant behavior with values of about -800 km/s for the first component and

of about -700 km/s for the second component.

Figure 23a,b. Timescale variations of the apparent rotational velocities Vrot (km/s) (left) and

radial velocities Vrad (km/s) (right) of the two C IV line components between the years 1979

and 1992.

The study of the N IV density region

In Fig. 24a,b we present the timescale changes of the apparent radial

velocities Vrad (km/s) and the random velocities Vrand (km/s) of the density

region where the N IV (λ 1718.8 Å) spectral line is created.

In the case of the radial velocities (Fig. 24a) we detect a constant behavior

with values lower than -50 km/s.

In the case of the random velocities (Fig. 24b), the values of about 100 km/s

correspond to the spectra fitted with the Rotational method. This means that

in these spectra the random ion velocities are not dominant. The values

between 350 and 400 km/s (points ×) correspond to the spectra fitted with the

Gaussian method.

Figure 24a,b. Timescale variations of the apparent radial velocities Vrad (km/s) (left) and the

random velocities Vrand (km/s) (right) of the density region where the N IV λ 1718.8 Å spectral

line is created.

The study of the N V density regions

In Figs. 25a,b we present the timescale variations of the values of the

apparent radial velocity Vrad (km/s) and the random velocities Vrand (km/s) of

the ions, in the density regions which create the two or three absorption

components of the N V resonance lines at λλ 1238.821, 1242.804 Å.

For the radial velocities (Fig. 25a) we detect a constant behavior with values

of about -1160 km/s for the first component (points o), of about -1400 km/s for

the second (points ●) and about -1450 km/s for the third one (points Δ).

For the random velocities (Fig. 25b) we calculate values of about 1000 km/s

for one satellite component and values of about 200 km/s for the others (points

×). The points ● correspond to the spectral lines which are best fitted with the

Rotational method.

Figure 25a,b. Timescale variations of the values of the apparent radial velocity Vrad (km/s)

(left) and the random velocities Vrand (km/s) (right) for the independent density regions of

matter which create the 2 or 3 satellite components of the N V resonance lines at λλ 1238.821,

1242.804 Å.

Time scale variation of the C IV, Si IV, N IV and N V density

regions in the HD 93521 stellar atmosphere Antoniou, A., Danezis, E., Lyratzi, E., Nikolaidis, D., Popović, L. Č., Dimitrijević, M. S., &

Theodosiou, E., XXVIth IAU General Assembly, Prague, August, 2006.

Danezis, E., Antoniou, A., Lyratzi, E., Popović, L. Č., Dimitrijević, M. S., VI Serbian Conference

on Spectral Line Shapes in Astrophysics Sremski Karlovci, Serbia, June, 2007.

From the study of the hyper-ionization regions in the atmosphere of the Oe

star HD 93521, we found that the C IV, N IV, N V and Si IV spectral features

are fitted with 5, 1, 1 and 3 SACs, respectively. In the case of N V we also

detected one emission component.

In Figure 26 we present the best fit of the C IV, N IV, N V and Si IV spectral

lines. In Figures 27-35 we present the time scale variation of some physical

parameters of the C IV, N IV, N V and Si IV regions in the spectrum of HD

93521.

Figure 26: Best fit of the C IV, N IV, N V and Si IV spectral lines of the Oe star HD 93521. The

graph bellow the fit indicates the differences between the observed spectrum and the fit.

Below the fit one can see the decomposition of the observed profile to its SACs.

Figure 27: Time scale variation of the rotational velocities (Vrot) of the C IV (left) and Si IV

(right) regions, which create the first SAC in the spectrum of the Oe star HD 93521.

Figure 28: Time scale variation of the radial velocities (Vrad) of the C IV (left) and N IV (right)

regions, which create the first SAC in the spectrum of the Oe star HD 93521.

Figure 29: Time scale variation of the radial velocities (Vrad) of the N V (left) and Si IV (right)

regions, which create the first SAC in the spectrum of the Oe star HD 93521.

Figure 30: Time scale variation of the random velocities (Vrand) of the C IV (left) and N IV


Figure 31: Time scale variation of the random velocities (Vrand) of the N V (left) and Si IV


Figure 32: Time scale variation of the Column Density (CD) of the C IV (both members of

doublet) (left) and N IV (right) regions, which create the first SAC in the spectrum of the Oe

star HD 93521.

Figure 33: Time scale variation of the Column Density (CD) of two resonance lines for the N V

(left) and Si IV (right) regions, which create the first SAC in the spectrum of the Oe star HD

93521.

Figure 34: Time scale variation of the radial (Vrad) (left) and random (Vrand) (right) velocities of

the N IV regions, which create the emission component in the spectrum of the Oe star HD

93521.

Figure 35: Time scale variation of the Column Density (CD) of the N IV region, which creates

the emission component in the spectrum of the Oe star HD 93521.

Some important conclusions Some results deriving from this PhD Thesis are the following:

1. Using the proposed model, we can calculate the values of some parameters

such as the rotational, the random and the radial velocities, the FWHM, the

optical depth, the absorbed or emitted energy, the column density and the

Gaussian standard deviation, as well as the relation among them. This

means that now we can try to understand the mechanism that is

responsible for the DACs or SACs phenomenon.

2. The acceptance of SACs and DACs phenomena as the reason of the spectral

line complex structure lead us to accept smaller values of the FWHM,

optical depths, column densities and different values for the rotational,

radial and random velocities, because now the idea is that the complex line

profile does non present a single spectral line, but a group of satellite

components (DACs or SACs). This idea leads us to a different mechanism

for the construction of the density regions that produce the DACs or SACs

regions.

3. The detected time scale variation of the parameters values in the C IV, N IV,

N V and Si IV density regions in the UV spectrum of the Oe star HD 93521

indicates that the radial, rotational and random velocities, the column

densities, and the optical depths present only small variations. This fact

leads us to accept that matter which creates DACs or SACs remains

practically stable during the studied period of 18 years. An other

explanation of this phenomenon is that in the area where we can detect

high density regions, matter flows, and only the physical properties

(conditions) which lead to high density, remain stable (for example

magnetic fields or shocks from a companion in the case of a binary system).

hyper-ionization phenomena in the coronal and post- coronal regions in the oe stellar envelopes

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