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Natal 2004/11/011st Brazil-CoRoT meeting1 Seismology of Be stars with CoRoT Paris-Meudon Observatory: A.M. Hubert, M. Floquet, C. Neiner* Univ. of Valencia: J. Fabregat, J. Gutierrez-Soto, J. Suso Univ. of Sao Paulo: E. Janot-Pacheco, L. Andrade, S. Daflon Royal Observatory of Belgium: Y. Frémat *ESA, Estec, RSSD
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Natal 2004/11/011st Brazil-CoRoT meeting2 Seismology of Be stars with CoRoT Overview of Be stars Be stars as non radial pulsators What do we expect from COROT? Preparatory programmes in “seismo“ fields in “exoplanet“ fields Conclusion
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Natal 2004/11/011st Brazil-CoRoT meeting3 Be stars: main characteristics Population: about 20% of all B-type stars Main sequence or slightly evolved Usually rapidly rotating stars ( c ≥ 0.80) Equatorially concentrated envelope Discrete mass loss events: unknown origin Variability: NRP+ stellar and circumstellar activity Be phase: non permanent character
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Natal 2004/11/011st Brazil-CoRoT meeting4 Variability in Be stars… Short-term variability present in the quasi-totality of early Be stars, in ~ 50% of mid-types (B4-B5e) and in only 18% of late Be stars (Hipparcos data, Hubert & Floquet 1998) Short periods commonly detected in photometry and spectroscopy Multiperiodicity in light curves and line profiles e.g. Oph (O9.5Ve), Jankov, Janot-Pacheco, Leister 2000 and MOST data; 19 Mon (B1Ve), Neiner, Hubert, Floquet 2003; Balona et al. 2002
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Natal 2004/11/011st Brazil-CoRoT meeting5 Example of multiperiodicity in light curves 19 Mon Upper panel:folded in phase with P 1 =0.191d Lower panel: folded in phase with P 2 =0.204d after removing P 1 NB: P 1 and P 2 also found from ground-based data by Balona et al. 2002 Variation of the magnitude of 19 Mon from Hipparcos data.
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Natal 2004/11/011st Brazil-CoRoT meeting6 Be stars as non-radial pulsators… Cephei, SPB (Slow Pulsating B stars), Be stars Same instability domain ( mechanism) Line profiles modelling support NRP (e.g. Rivinius et al. 2002, Neiner et al. 2004)
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Natal 2004/11/011st Brazil-CoRoT meeting7 Be stars as non-radial pulsators… NRP: trigger for discrete mass loss events? only one case: Cen, 15 years of spectroscopic observations: coincidence of positive mode interference and mass loss events (Rivinius et al. 1998) 6 periods sorted in 2 groups main mode of each period group: P1=0.5029dl=2, |m|=2 f=0.21, 0.39, 0.60 Hz P5=0.2814dl=3, |m|=3 f=0.33 Hz
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Natal 2004/11/011st Brazil-CoRoT meeting8 Cen : pulsation beating effect Rivinius et al., 1998 The overall reconstructed amplitude (solid lines); circles: ; squares: ; dots:
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Natal 2004/11/011st Brazil-CoRoT meeting9 Be stars as magnetic pulsators Magnetically pulsating stars? 2 detections among pulsating early B stars: Cep (Henrichs et al. 2000): also a slowly rotating Be star! P rot =12d; P puls =0.19d Ori (Neiner et al. 2003): a « classical » Be star P rot =1.29d; P puls =0.97d magnetic fields: several hundreds of Gauss
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Natal 2004/11/011st Brazil-CoRoT meeting10 Observed frequencies in Cep (Telting et al. 1997) f 3 =56.979 Hz f 4 =58.819 Hz f 1 =60.764 Hz f 5 =62.697 Hz f 6 =64.618 Hz f 2 =62.269 Hz magnetic splitting + identification of modes information on the evolutionary stage ( Shibahashi & Aerts, 2000) - Quintuplet fine structure of a radial mode (f 1 ) - f 2 non radial mode (l=2,m=0) }
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Natal 2004/11/011st Brazil-CoRoT meeting11 Seismology with COROT Homogenous data Long-term continuous coverage: high accuracy on frequency spectrum - multimode detection - beating it will allow us to disentangle pulsations from stellar activity (temporarily corotating clouds) Very high photometric accuracy : detection of high degree modes of low amplitude Amp 4 in early Be stars (Balona & Kambe 1999) search of low-amplitude g modes in late Be stars
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Natal 2004/11/011st Brazil-CoRoT meeting12 Early and late Be stars: 2 science goals Early Be stars (B0-B3): pulsations and multiperiodicity already detected from the ground Is the beating effect of close pulsation periods the cause of the Be phenomenon i.e. the presence of a disk around Be stars? Effects of fast rotation and magnetic field on the pulsations Late Be stars (B4-B9): pulsations predicted by theory but the amplitude is too small to be detected from the ground detection of pulsations with Corot!
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Natal 2004/11/011st Brazil-CoRoT meeting13 Be stars as potential targets for asteroseismology with COROT About 70 Be stars with 6<V<9.5 in the cones of COROT (seismology fields) including 15 new Be stars with V<8.0 (GAUDI) 18 Be stars as secondary targets candidates for the core programme of asteroseismology Faint Be stars with 12<V<16.5 in the exoplanet fields as part of the Additional Programme
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Natal 2004/11/011st Brazil-CoRoT meeting14 Preparatory programmes in “seismo“ fields Be stars as secondary targets candidates in primary fields (long runs) Photometric variability: periodicity, multiperiodicity Spectroscopic variability: pulsation modes Determination of fundamental parameters taking into account fast rotation - Abundances Search of magnetic fields (EsPaDoNS, CFHT) Be stars for exploratory fields (short runs)
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Natal 2004/11/011st Brazil-CoRoT meeting15 Photometric variability: Hipparcos (Hubert & Floquet ) Some of the targets observed by Hipparcos: periodicity found!
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Natal 2004/11/011st Brazil-CoRoT meeting16 Ground-based photometry + variability (Fabregat, Gutierrez-Soto, Suso) Strömgren photometry at the 0.9m in Granada for variability: detection of variability, periodicity and even multiperiodicity for HD 168797 and HD 179405 NB: HD 168797 has been in a B phase for several years!
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Natal 2004/11/011st Brazil-CoRoT meeting17 Spectroscopy: GAUDI for 6 < V < 8 spectra in GAUDI 17 new Be stars discovered in GAUDI But: No spectrum if V > 8 Additional data for studying variability and determining fundamental parameters are needed
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Natal 2004/11/011st Brazil-CoRoT meeting18 Additional spectroscopy + variability (Hubert, Janot-Pacheco, Andrade) Spectroscopic observations at the 1.5m at OHP, soon EsPaDoNS Spectroscopic observations at the 1.6m at LNA, FEROS Spectrum for Be stars with V > 8 Detection of variability
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Natal 2004/11/011st Brazil-CoRoT meeting19 Determination of stellar parameters ( Frémat, Neiner, Daflon, Andrade) Data : GAUDI + OHP + LNA 2 independent determinations: Frémat & Neiner + Daflon & Andrade ~70 Be stars in the eyes of Corot 26000 3.75 253
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Natal 2004/11/011st Brazil-CoRoT meeting20 Rapid rotation gravitational darkening effects
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Natal 2004/11/011st Brazil-CoRoT meeting21 (Frémat & Zorec)
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Natal 2004/11/011st Brazil-CoRoT meeting22 Centre Main targetBe targetTypeVvsiniTefflog gVariability HD 171234+170580HD 171219B8e7.65300135903.07 HD 171834HD 171219B8e7.65300135903.07 HD 175726HD 175869B9IIIe5.56164118103.25 HD 177552- HD 181555+180642HD 181231B9Ve8.58250136583.73 HD 181367B8e9.36279135003.65 Only late Be stars in these primary targets fields. Results for primary fields
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Natal 2004/11/011st Brazil-CoRoT meeting23 Anticentre Main targetBe targetTypeVvsiniTefflog gVariability HD 43318- HD 43587HD 43285B6Ve6.07240140003.780.45 d HD 43913A0e7.88 HD 45067- HD 46558HD 45901B2Ve8.8164265183.73phot HD 46484B1Ve7.74120270003.603.29 d HD 47359B0.5Ve8.87 HD 49933+49434HD 49330B0e8.92300270003.820.28 d HD 49585B0.5Ve9.13253260423.750.61 d HD 50209B9Ve8.33180118093.620.66 + 0.59 d HD 50696B1Ve8.83350213003.450.31 d HD 52265HD 50891B0pe8.880.54 d HD 51193B1Vnne8.06215229943.620.61 + 5.5 d HD 51404B3e9.3342225004.20.37 d HD 51452B0IIIne8.08298298873.88spec
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Natal 2004/11/011st Brazil-CoRoT meeting24 Centre: 4 possible late Be stars including 3 well positioned next to the primary targets no early Be stars Anticentre: 3 possible late Be stars well positioned next to the primary targets 10 possible early Be stars including 3 well positioned next to HD 52265 TOTAL: 17 possible Be stars (7 late, 10 early) including 9 well positioned (6 late and 3 early)
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Natal 2004/11/011st Brazil-CoRoT meeting25 Field HD 171234 + HD 170580 171219
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Natal 2004/11/011st Brazil-CoRoT meeting26 Diapositive 29 Field HD 49933 + HD 49434 50209 49330 49585 50696 3 early Be stars outside the CCDs with this position of the CCDs
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Natal 2004/11/011st Brazil-CoRoT meeting27 Field HD 52265 + HD 50891 51404 51193 51452 50891
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Natal 2004/11/011st Brazil-CoRoT meeting28 HR diagram of Be secondary targets Rotation effect c = 0.95 + 4 Be stars
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Natal 2004/11/011st Brazil-CoRoT meeting29 Results for exploratory fields ~ 60 possible Be targets for exploratory fields (short runs) It is better to concentrate on early Be stars, since we have very few early Be stars as secondary targets 2 already detected with multiperiodicity (Fabregat et al.) : HD 168797 (B3e) and HD 179405 (B5e) Targets in non-selected primary fields have been well studied easier candidates
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Natal 2004/11/011st Brazil-CoRoT meeting30 Preparatory programmes in exoplanet fields Be stars as targets for seismology in exoplanet fields (12<V<16) Detection of Be stars in selected fields (in progress); two methods: photometry and spectroscopy Determination of fundamental parameters Selection of the “best “ candidates (early Be stars)
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Natal 2004/11/011st Brazil-CoRoT meeting31 Detection of Be stars in the exoplanet fields uvby photometry + H ,H narrow filters by J. Fabregat and collaborators: Starting point: emission line stars catalogue of Robertson & Jordan (1989) No information on spectral types is available Observations at Calar Alto (Almeria, Spain) o Provide spectral classification for RJHA stars o Find new Be stars in exoplanet fields
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Natal 2004/11/011st Brazil-CoRoT meeting32 Photometry of emission line stars in potential exoplanet fields to identify B stars Diagramme without reddening [m 1 ]-[c 1 ] 5 emission line stars of RJ are B stars
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Natal 2004/11/011st Brazil-CoRoT meeting33 At least 4 of 5 B emission line stars are confirmed and are probably Be stars + 1 more discovered Diagramme - N.B.: Robertson-Jordan stars limited to V<14!
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Natal 2004/11/011st Brazil-CoRoT meeting34 Detection of Be stars in the exoplanet fields Spectroscopy at LNA (see poster Andrade & Janot) Spectroscopy at ESO with VLT/GIRAFFE Part of a programme on the Guaranteed Time Observations of the Observatoire de Paris devoted to spectral classification and precise type identification in exoplanet fields of COROT (G. Alecian P.I., Deleuil, Hubert et al.): To validate the method of spectral classification for exoplanet stellar database To determine fundamental parameters To identify specific groups of stars, Hg-Mn, Be…for Additional Programmes of COROT
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Natal 2004/11/011st Brazil-CoRoT meeting35 Giraffe: a multi-object spectrograph
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Natal 2004/11/011st Brazil-CoRoT meeting36 VLT-GIRAFFE: a multi-object spectrograph In Medusa mode: 132 fibers R=7500 and 25000 Required astrometric precision : 0.2” Field =25’ Fibers: Minimal separation ~ 12”
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Natal 2004/11/011st Brazil-CoRoT meeting37 Search for Be stars with VLT-GIRAFFE Domains: LR06 (644nm - 710nm; R=8600): H - emission line stars:Be, Ae/Be… LR02 (397nm - 456nm; R=6400): H , H , blue He I, Mg II - stellar types and fundamental parameters For B9 stars, 1h exposure time, V= 15, S/N 100
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Natal 2004/11/011st Brazil-CoRoT meeting38 Expected detection of Be stars in the exoplanet fields Centre direction ~ 40 Be stars (12<V<16) in 1 deg 2 Exoplanet CCDs ~1.3x2.5 deg 2 Anti-centre direction ~ 10 Be stars (12<V<16) in 1 deg 2 Exoplanet CCDs ~1.3x2.5 deg 2 from estimation of stellar density in 1 deg 2 towards the galactic centre and anti-centre given by M. Deleuil and from the ‘Besançon’ model of stellar population synthesis of the Galaxy (Robin et al. 2003)
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Natal 2004/11/011st Brazil-CoRoT meeting39 Conclusions We need early and late Be stars as secondary targets: 2 different science goals We have 9 out of 17 Be stars (possible secondary targets) which are well positioned in the CCDs, but 6 late and only 3 early We need to concentrate on early Be stars for the exploratory fields We already have 2 very interesting exploratory candidates The list of faint Be stars for seismology is in preparation; it depends on the final choice of the position of the CCDs
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