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Hubert CW8

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Information about Hubert CW8
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Published on September 14, 2007

Author: Alien

Source: authorstream.com

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Corot Be stars group:  Corot Be stars group Be stars: Secondary targets candidates for the Core Programme of asteroseismology Targets for the Additional Programme The team: 11 members (Belgium, Brazil, France and Spain) People interested in joining our group are welcome! Contact: coralie@ster.kuleuven.be Website: http://www.ster.kuleuven.ac.be/~coralie/corotbe.html Slide2:  Be stars as potential targets for the Additional Programme Science goal for Be stars: About 70 Be stars with 6andlt;Vandlt;9.5 in the cones of COROT (seismology fields) including 15 new Be stars with Vandlt;8.0 (GAUDI) (Neiner, Hubert, Catala 2005) Candidates for pulsations, rotation, activity, binarity studies (short runs) Faint Be stars with 12andlt;Vandlt;16.5 in the exoplanet fields Candidates for asteroseismology (long runs) Slide3:   Preparatory programs for bright Be stars Photometric variability Strömgren photometry (0.9m-T in Granada) : periodicity in early Be stars candidates (Gutierrez-Soto et al. 2003) and even multiperiodicity for NW Ser and V1446 Aql (Fabregat, this COROTWeek) Spectroscopic variability (LNA + OHP+ multisite) Determination of fundamental parameters taking into account fast rotation and veiling (Frémat, et al. 2005) Search for magnetic fields (EsPaDoNS, CFHT) Slide4:  Determination of stellar parameters Data : GAUDI + OHP + LNA + FEROS Rapid rotation  stellar flattening + gravitational darkening effects FASTROT (Frémat andamp; Zorec) - assumes: Rigid rotator (Roche model)  log g Von Zeipel law  Teff Local model atmospheres - LTE temperature and pressure distribution (ATLAS9, Kurucz) - NLTE level populations (TLUSTY, Hubeny andamp; Lanz) CS envelope  veiling effect Slide5:  From modeling of different spectral domains  Teff, logg, Vsin i and i for a given /c Without correction for rotational effects: Teff = 25450°  1000°K, log g = 3.87  0.10 V sini = 310  30 km/s With corrections for /c= 0.9 (value adopted from Frémat, Zorec et al., in press): Teff = 26000°  1000°K, log g = 4.10  0.10 V sini = 325  30 km/s, i ~ 60° : observed spectrum : fitted spectrum Slide6:  With corrections for /c=0.9 Without correction for rotational effects Location of Be stars in the HR diagram Slide7:  Be star’s spectral-type distribution in the cones of COROT (Frémat, Neiner, Hubert, Floquet, Zorec, Janot-Pacheco, de Medeiros, 2005, submitted) Different Be star spectral distributions between the Galactic Centre and Anticentre  to be related to the insterstellar absorption, more important towards the Galactic Centre (Lucke 1978) Slide8:  Detection of Be stars in the exoplanet fields 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., Hubert, Deleuil, Neiner, Martayan, Floquet): To validate the method of spectral classification for exoplanet stellar database (Deleuil et al.) To determine fundamental parameters To identify specific groups of stars, Hg-Mn, Be…for Additional Programmes of COROT  Preparatory programmes for faint Be stars Slide9:  Giraffe: a multi-object spectrograph Slide10:  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' Slide11:   Anticentre direction 2 GIRAFFE fields observed (=26’) next to HD 49933+HD 49434 About 35 B0-A5 candidates in each field (exodat catalog by Deleuil et al.) 2 Be 31 B0-A0 (Teff ≥ 9500°K) H (Alecian, Martayan et al. in preparation) Slide12:  Fundamental parameters B stars: -LTE temperature and pressure distributions (ATLAS9, Kurucz) -NLTE level populations (TLUSTY, Hubeny andamp; Lanz) Example of fit for a B star: : observed spectrum : fitted spectrum Teff=13615°K, log g=3.95 V sini=65 km/s, RV=49 km/s Slide13:  Be stars: Teff=20860°K, log g=3.93 V sini=260 km/s; RV=55 km/s Teff=15100°K, log g=3.40 V sini=297 km/s; RV=59 km/s Slide14:  uvby + H,H narrow filters (J. Fabregat, Gutierrez-Soto, Suso) Starting point: emission line stars catalogue of Robertson andamp; Jordan (1989) ( but Vandlt;14!) No information on spectral types is available Observations at Calar Alto (Almeria, Spain) Provide spectral classification for RJHA stars Find new Be stars in exoplanet fields Detection of Be stars in the exoplanet fields… Photometry at Granada, Spain Slide15:  Photometry of emission line stars in potential exoplanet fields to identify B stars Diagram without reddening [m1]-[c1] 5 emission line stars of RJ are B stars (from Fabregat et al. 2003, CorotWeek 4) Slide16:  IR photometry with Spitzer - 4 fields observed with IRAC: 2 at HD49933+49434, 2 at HD52265 - 4 IR colors (3.6, 4.5, 5.8 et 8.0 mm) for each field + JHK colors from 2MASS + visible colors and extinction from the exoplanets WG 4 Corot CCDs 2 Spitzer fields Slide17:  2 fields next to HD 49933+49434 Slide18:  2 fields next to HD 52265 Slide19:  Spitzer colors IR excess Examples Typical Be star SED Possible Be star observed with Spitzer B Be 2MASS Black-body B (Neiner et al. in preparation) Next Future… :  Next Future… Characterization of bright Be stars almost finished Search for faint Be stars still in progress a small number of detections only! But new data! VLT/GIRAFFE spectra (Centre direction), SPITZER data And new proposals! -WFI + ubvyr and H filters at INT, Canaries (Fabregat, Neiner, Gutierrez-Soto et al.) - spectroscopy T1.6m at LNA and T4m-SOAR, (R=6000, visible + R=3000, IR), Brazil + Chile (Janot-Pacheco, Andrade) We need positions of hot stars from exoplanet database!

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