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Spectral Investigations of Spectral Investigations of Cepheids in Southern Cepheids in Southern
HemisphereHemisphereScientifical Seminar
KOLOS-2012
06.12-09.12.2012
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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
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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.
•
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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.
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Observations:Observations:
• 1.9-m telescope of• South African
Astronomical Observatory,
• High Karoo,• South Africa.
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Observations:Observations:
• Echelle-spectrograph• GIRAFFE GIRAFFE (Grating
• Instrument for Radiation Analysis with a Fibre Fed Echelle);
• R=39000; • Specral ranges:• 4300-7100 AA
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Radial Velocity Curve for X Sgr
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Fe I 6055.99 line in X Sgr Atmosphere (SAAO)
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Fe I 6055.99 line in X Sgr Atmosphere (MDO)
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Hβ line profiles for X Sgr
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Hα line profiles for X Sgr
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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
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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
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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 •
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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
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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
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Radial Velocity Curve for W Sgr
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Hβ line profiles for W Sgr
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Hα line profiles for W Sgr
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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
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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
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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 •
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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
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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
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Radial Velocity Curve for BG Cru
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Fe I 6055.99 line in BG Cru Atmosphere (SAAO)
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Fe I 6055.99 line in BG Cru Atmosphere (VLT)
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Lines of Ions Fe II 6369.46 and Si II
6371.355 in the Spectra of BG Cru (SAAO)
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Lines of Ions Fe II 6369.46 and Si II 6371.355 in the Spectra of BG Cru (VLT)
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Hα line profiles for BG Cru
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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
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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
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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
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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
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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
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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)
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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.
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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
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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.
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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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THANK YOU!