Photometric and Photometric and spectral observations of spectral observations of

the star the star EM CepEM CepD. Kjurkchieva & D. MarchevD. Kjurkchieva & D. Marchev

Photometric and Photometric and spectral observations of spectral observations of

the star the star EM CepEM CepD. Kjurkchieva & D. MarchevD. Kjurkchieva & D. Marchev

I. IntroductionI. Introduction

Disk-like starsDisk-like starsThe disks form

around stars at different evolu-tional stages

• T Tau stars• Cataclysmic stars• Symbiotic stars• X-Ray stars• Some semidetached

systems

The

TheThe accreation accreation Keplerian diskKeplerian disk produce two-two-peakedpeaked wide wide

emission linesemission lines(the inner fast rotating (the inner fast rotating

parts produces the parts produces the wings of their profiles)wings of their profiles)

TheThe accreation accreation Keplerian diskKeplerian disk produce two-two-peakedpeaked wide wide

emission linesemission lines(the inner fast rotating (the inner fast rotating

parts produces the parts produces the wings of their profiles)wings of their profiles)

II. Some preliminary resultsII. Some preliminary results

1. The cataclysmic star UX UMaUX UMa Our H spectra of (on the left) show

• the profile is one-peaked only around the eclipse phase;• the H profiles are two-peaked (V and R peak) at the rest phases;

• the H line is symmetric at the two quadratutes;

1. The cataclysmic star UX UMaUX UMa Our H spectra of (on the left) show

• the profile is one-peaked only around the eclipse phase;• the H profiles are two-peaked (V and R peak) at the rest phases;

• the H line is symmetric at the two quadratutes;

The conclusion: two-peaked wide H line of UX UMa is produced from

an accretion disk around the white dwarf. This disk is fed by matter from the secondary late compo-

nent filling-in its Roche lobe.

The conclusion: two-peaked wide H line of UX UMa is produced from

an accretion disk around the white dwarf. This disk is fed by matter from the secondary late compo-

nent filling-in its Roche lobe.

2. H2. H spectra of the spectra of the RS CVn star RS CVn star FK ComFK Com

Kjurkchieva D., Marchev D., 2005, A & A 434, 221, “H observations of the star FK Com”

• On the left top –

The spectra averaged in phase bins

• On the left bottom – The mean spectrum

The phase variability of the subtracted spectra gives information about the position of the sources of additional H emission and absorption

The phase variability of the subtracted spectra gives information about the position of the sources of additional H emission and absorption

It is seen a bulk of emission and a bulk of absorption which position is opposite at the two quadratures.

Spectra of FK Com around phases 0,25 and 0,5Spectra of FK Com around phases 0,25 and 0,5Spectra of FK Com around phases 0,75 and 0,5Spectra of FK Com around phases 0,75 and 0,5

The analysis of the phase variability of the subtracted spectra of FK Com (individual spectra minus the mean spectrum)

leads to the conclusion

The two sources of the additional emission

and absorption moves in anti-phase during

the whole cycle.

main star - source of the absorption reversalextended half-illuminated disk - source of the emission peaksSAE – source of additional emissionSAA - source of additional absorptionsecondary starsecondary star – source of the illumination of the disk

The modeling of our H spectra leads to a

binary binary configuration ofconfiguration of

FK ComFK Com consisting of

The modeling of our H spectra leads to a

binary binary configuration ofconfiguration of

FK ComFK Com consisting of

- almost equal intensities of the emission peaks above the continuum- almost equal widths of the absorption reversal, the two emission peaks- presence of additional emission features on the main V and R peak- almost the same position of the emission peaks

We noted the similarity of the H profile of FK ComFK Com and UX UMaUX UMa in

We noted the similarity of the H profile of FK ComFK Com and UX UMaUX UMa in

- the exchanging places of the two minima - the standstill at phase 0,83 an indication of alternation between the two states???

1. Two types of

light curves

1. Two types of

light curves

III. The B-star III. The B-star EM CepEM Cep

The irregular times of the minima (O-C=0,01d for a

couple of days) confirmation of secular linear decreasing of the

period

2. Our H spectra of EM Cep

on the left: spectra at Be-state in 2004 - H in emission

on the right: spectra at B-state in 2005 - H in absorption

Тhe full width and depth of the H profiles of EM Cep at Be and B state are almost the same.

on the left: The subtracted H profiles of EM Cep at B state (individual minus spectrum at phase 0.47) have central

additional emission (ADEM) and two side additional absorptions (ADABS)

on the left: The subtracted H profiles of EM Cep at B state (individual minus spectrum at phase 0.47) have central

additional emission (ADEM) and two side additional absorptions (ADABS)

bottom: The mirror image of the subtracted H profile at phase 0,24 is similar to real

H profile at Be state

bottom: The mirror image of the subtracted H profile at phase 0,24 is similar to real

H profile at Be state

The subtracted spectra of

EM Cep at Be state (individual minus spectrum

at phase 0.43) show central

additional emission

(ADEM) around the phases of quadratures

The H profiles of EM Cep at phases 0,75

and 0,47 coincidence

while the positions and the widths of the HeI

lines (6677 A) are different. What is the What is the

reason?reason?Is there some Is there some

contribution of contribution of secondary star?secondary star?

The H profiles of EM Cep at phases 0,75

and 0,47 coincidence

while the positions and the widths of the HeI

lines (6677 A) are different. What is the What is the

reason?reason?Is there some Is there some

contribution of contribution of secondary star?secondary star?

Conclusions from the radial velocity curves:Conclusions from the radial velocity curves:

The ADABS compensate ADEM at minima;The ADABS compensate ADEM at minima; The sources of ADABS are near the star surface;The sources of ADABS are near the star surface; The angle between the line-of-sight and star rotational axis is small.The angle between the line-of-sight and star rotational axis is small.

The radial velocity The radial velocity curves of the two curves of the two ADABS show the ADABS show the opposite motion opposite motion of their sources of their sources

with velocity with velocity equal to the star equal to the star

rotational velocity rotational velocity of of EM CepEM Cep

The radial velocity The radial velocity curves of the two curves of the two ADABS show the ADABS show the opposite motion opposite motion of their sources of their sources

with velocity with velocity equal to the star equal to the star

rotational velocity rotational velocity of of EM CepEM Cep

We noted the similarity of the H the similarity of the H profile of profile of EM CepEM Cep at Be state with that at Be state with that

of of FK ComFK Com in: in: a) positions and width of the emission peaks;

b) whole width of the H line

We found also a similarity of the H profile of FK Com FK Com andand EM Cep EM Cep

with

• the shape and phase variability of the H and H lines of the cataclysmic

SU UMa-type star HT CasHT Cas (Catalan 1995);

• the H line of the T Tau-type star AA TauAA Tau (Hartmann 1998) .

IV.IV. ConclusionConclusion

• The wide two-peaked H line of EM Cep at Be state means presence of extended disk;

• The alternation between the B and Be state may be caused by the change of the optical thickness of the disk;

• There are two sources of additional absorption on surface of EM Cep which radial velocities are opposite and their amplitudes are equal to the star rotation velocity;

• The phase variability of the brightness and spectra of EM Cep might be explained by the rotation of some inhomogeneous structure but presence of companion star is not excluded.

V. Open questionsV. Open questions

• Why the HWhy the H emission peaks in the spectra of emission peaks in the spectra of different types objects (Be stars, FK Com different types objects (Be stars, FK Com stars, cataclysmic stars, T Tau stars) have the stars, cataclysmic stars, T Tau stars) have the same velocities? same velocities?

• Why the full width of the HWhy the full width of the H line in the spectra line in the spectra of these different types objects are the same? of these different types objects are the same?

• Do these facts mean that there is some Do these facts mean that there is some unifiedunified mechanismmechanism of creating of similar gaseous of creating of similar gaseous structure with equal velocitiesstructure with equal velocities in different types different types of starsof stars?!??!?