Spectral Investigations of Spectral Investigations of Cepheids in Southern Cepheids in Southern

HemisphereHemisphereScientifical Seminar

KOLOS-2012

06.12-09.12.2012

Authors:Authors:

• I.A. Usenko, Dpt. Of Astronomy, Odessa National University, Odessa, 65014 Ukraine

• A.Yu. Knyazev, SAAO, CapeTown, 7925 South Africa

• L.N. Berdnikov, Sternberg Astronomical Institute, Moscow, 119992 Russia

• V.V. Kravtsov, Instituto de Astronomia, Universidad Catolica del Norte, Antofagasta, Chile

• A.B. Fokin, Institute of Astronomy, Russian Academy of Sciences, Moscow Russia

TheThe Main Tasks:Main Tasks:

• 1. To obtain as many as possible spectra of • Cepheids during its pulsational period.• 2. To estimate the peculiar properties of • absorptinal lines in these spectra.• 3 To determine their atmosphere parametrs • and chemical composition.

•

Three unusual Cepheids:Three unusual Cepheids:

• 1. X Sgr P = 7.014 days, <V> = 4.56 mag;• Spec. Type = F7 II, DCEP.

• 2. W Sgr P = 7.595 days, <V> = 4.66 mag;• Spec. Type = F7.2 Ib, DCEP.

• 3. BG Cru P = 3.343 days, <V> = 5.49 mag;• Spec. Type = F7.2 Ib, DCEPS.

Observations:Observations:

• 1.9-m telescope of• South African

Astronomical Observatory,

• High Karoo,• South Africa.

Observations:Observations:

• Echelle-spectrograph• GIRAFFE GIRAFFE (Grating

• Instrument for Radiation Analysis with a Fibre Fed Echelle);

• R=39000; • Specral ranges:• 4300-7100 AA

Radial Velocity Curve for X Sgr

Fe I 6055.99 line in X Sgr Atmosphere (SAAO)

Fe I 6055.99 line in X Sgr Atmosphere (MDO)

Hβ line profiles for X Sgr

Hα line profiles for X Sgr

Atmosphere parameters for X Sgr

&5784.4374 &6367$\pm$10& 2.10& 4.30&5139.0176 &7.0137&0.023\\

&5785.3798 &

-------------------------------------------------------------- HJD Teff log g Vt Phase 2450000+ (K) (km/s)-------------------------------------------------------------- 5784.4374 6367 ± 10 2.10 4.30 0.023 5785.3798 6223 ± 28 2.00 4.50 0.158 5788.4230 5791 ± 25 1.90 4.30 0.591 5789.4562 5900 ± 50 2.00 4.40 0.739 5790.4428 6435 ± 38 2.10 4.30 0.879--------------------------------------------------------------- 6143 ± 30 2.00 4.35

Elemental abundances for X Sgr«Key Elements»

• Element [El/H] σ NL• C I -0.26 0.22 37• O I +0.20 0.15 10• Na I +0.31 0.18 24• Mg I +0.19 0.18 18• Al I +0.21 0.23 10• Fe I -0.02 0.17 451• Fe II -0.02 0.16 130

Elemental abundances for X Sgr«α-Elements»

• Element [El/H] σ NL• Si I +0.06 0.16 57• Si II -0.04 0.42 4• S I +0.11 0.26 16• Ca I -0.07 0.17 6• Sc II -0.10 0.20 27 •

Elemental abundances for X Sgr«Fe- group Elements»

• Element [El/H] σ NL

• Ti I +0.08 0.24 130

• Ti II -0.05 0.15 32

• V I +0.26 0.22 41

• V II -0.06 0.26 15

• Cr I +0.09 0.25 124

• Cr II -0.09 0.19 36

• Mn I -0.08 0.21 36

• Co I +0.03 0.26 61

• Ni I -0.08 0.22 202

Elemental abundances for X Sgr«r- and s- process Elements»

• Element [El/H] σ NL

• Cu I +0.28 0.20 11

• Zn I -0.34 0.22 12

• Sr I -0.08 - 1

• Y II +0.00 0.26 28

• Zr II +0.00 0.30 23

• La II +0.21 0.30 21

• Ce II -0.02 0.18 27

• Pr II -0.05 0.27 11

• Nd II -0.10 0.25 43

• Sm II -0.02 0.21 11

• Eu II +0.13 0.16 9

• Gd II -0.14 0.35 4

Radial Velocity Curve for W Sgr

Hβ line profiles for W Sgr

Hα line profiles for W Sgr

Atmosphere parameters for W Sgr

-------------------------------------------------------------- HJD Teff log g Vt Phase 2450000+ (K) (km/s)-------------------------------------------------------------- 5784.4910 6366 ± 23 2.20 4.50 0.944 5785.4231 6210 ± 30 1.90 4.00 0.067 5788.4475 5522 ± 15 1.50 3.60 0.465 5789.4562 5396 ± 8 1.40 3.50 0.598 5790.4955 5471 ± 23 1.70 4.30 0.735--------------------------------------------------------------- 5793 ± 20 1.75 4.00

Elemental abundances for W Sgr«Key Elements»

• Element [El/H] σ NL• C I -0.19 0.22 49• O I +0.04 0.21 16• Na I +0.17 0.19 27• Mg I +0.04 0.20 20 • Al I +0.24 0.23 10• Fe I +0.03 0.14 947• Fe II +0.04 0.11 153

Elemental abundances for W Sgr«α-Elements»

• Element [El/H] σ NL

• Si I +0.10 0.10 104• Si II +0.14 0.14 7• S I +0.01 0.25 19• Ca I +0.01 0.19 65• Sc I -0.07 0.31 20• Sc II -0.10 0.14 33 •

Elemental abundances for W Sgr«Fe- group Elements»

• Element [El/H] σ NL

• Ti I +0.06 0.21 304• Ti II +0.01 0.14 48• V I +0.04 0.20 103• V II -0.15 0.16 22• Cr I +0.04 0.25 252• Cr II +0.09 0.21 66 • Mn I -0.10 0.15 82• Co I -0.01 0.15 142• Ni I -0.03 0.18 453

Elemental abundances for W Sgr«r- and s- process Elements»

• Element [El/H] σ NL

• Cu I -0.05 0.33 18• Zn I -0.04 0.50 17• Sr I +0.25 0.44 9• Y II +0.10 0.18 30• Zr II +0.03 0.18 25• La II +0.10 0.21 25 • Ce II -0.03 0.25 58• Pr II -0.14 0.25 15• Nd II +0.10 0.22 81• Sm II -0.00 0.26 15• Eu II +0.06 0.11 10• Gd II +0.13 0.41 5

Radial Velocity Curve for BG Cru

Fe I 6055.99 line in BG Cru Atmosphere (SAAO)

Fe I 6055.99 line in BG Cru Atmosphere (VLT)

Lines of Ions Fe II 6369.46 and Si II

6371.355 in the Spectra of BG Cru (SAAO)

Lines of Ions Fe II 6369.46 and Si II 6371.355 in the Spectra of BG Cru (VLT)

Hα line profiles for BG Cru

Atmosphere parameters for BG Cru

• --------------------------------------------------------------• HJD Teff log g Vt Phase• 2450000+ (K) (km/s)• --------------------------------------------------------------• 5784.2863 6225 ± 35 2.10 4.00 0.258• 5785.2262 6140 ± 28 2.00 4.50 0.544• 5788.2500 6264 ± 26 2.20 4.60 0.150• 5789.2264 6416 ± 25 2.20 4.20 0.741• 5790.2977 6218 ± 34 2.20 4.20 0.061• ---------------------------------------------------------------• 6253 ± 30 2.15 4.30

Elemental abundances for BG Cru«Key Elements»

• Element [El/H] σ NL• C I -0.25 0.18 36• O I -0.00 0.13 10• Na I +0.28 0.12 20• Mg I +0.10 0.23 21 • Al I +0.27 0.25 10• Fe I +0.04 0.14 615• Fe II +0.05 0.10 108

Elemental abundances for BG Cru«α-Elements»

• Element [El/H] σ NL• Si I +0.17 0.11 60• Si II -0.00 0.23 4• S I +0.04 0.17 17• Ca I +0.09 0.17 52• Sc II +0.05 0.14 28

Elemental abundances for BG Cru«Fe- group Elements»

• Element [El/H] σ NL

• Ti I +0.16 0.17 142

• Ti II +0.04 0.16 46

• V I +0.28 0.15 41

• V II +0.05 0.20 20

• Cr I +0.10 0.26 161

• Cr II +0.05 0.16 44

• Mn I -0.01 0.18 53

• Co I -0.13 0.19 64

• Ni I +0.02 0.18 268

Elemental abundances for BG Cru«r- and s- process Elements»

• Element [El/H] σ NL

• Cu I +0.27 0.19 18

• Zn I -0.28 0.32 14

• Sr I +0.31 0.37 8

• Y II +0.08 0.19 27

• Zr II +0.16 0.18 20

• La II +0.22 0.24 17

• Ce II +0.02 0.18 44

• Pr II +0.14 0.28 10

• Nd II +0.12 0.27 61

• Sm II +0.12 0.20 14

• Eu II +0.27 0.08 10

• Gd II +0.15 0.23 5

Circumstellar envelopes around the Cepheids

• 1) Cepheids with periods more than 10-15 days: absorptional lines of metals demonstrate the usual character, therefore Hα line undergoes the complicated changes (see X Cyg (Gillet, 1993));

• 2) The main reason of this effect is the presence of circumstellar envelope around the Cepheid atmosphere (see Nardetto et al. 2008);

• 3) The observations of RS Pup and l Car confirmthis hypothesis ( see Krevella et al. 2009)

Circumstellar envelopes around the Cepheids

• 4) The main problem: this envelope should be «optically thick» in Hα line core, but to be «clear» for the absorptional lines of metals.

• 5) In this case the Hα line represents the radial velocity of this envelope, therefore the lines of metals represent the Doppler velocities of pulsating layers.

The Cases of X Sgr and BG Cru

• 1) This pecuilar character of metals absorptional lines and absence of these onesfor hydrogen lines should be explained by the presence of multiple shock waves combined with non-radial pulsations,

• producing the extensive hydrogen shell around the Cepheid.

• 2) This shell promoted itself to form these shock waves in the Cepheids atmospheres

The Cases of X Sgr and BG Cru

• 3) The presence of close hot companion could be promote to non-radial pulsations in the high levels of Cepheids atmospheres. X Sgr has a companion with an orbital period 509.25 days (Szabados 1989), thereas BG Cru is a spectroscopical binary too.

The Case of W Sgr

• 1) Emission features in the core of hydrogen lines are not typical for Population I Cepheids, but they are present in the W Vir type variables (Population II). These emission features are an evidence of so called «highlighting» behind the front of shock wave after its passing.

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