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J/A+A/304/415   uvby-Hbeta photometry of Eta Car 1992-94   (van Genderen+, 1995)
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A pulsating star inside Eta Carinae I. Light variations 1992-1994
     van Genderen A.M., Sterken C., De Groot M., Stahl O., Andersen J.,
     Andersen M.I., Caldwell J.A.R., Casey B., Clement R., Corradi W.J.B.,
     Cuypers J., Debehogne H., Garcia de Maria J.M., Joench-Soerensen H.,
     Vaz L.P.R., Stefl S., Suso Lopez J., Beele D., Eggenkamp I.M.M.G.,
     Goecking K.-D., Jorissen A., de Koff S., Kuss C., Schoenmakers A.P.,
     Vink J., Waelde E.
    <Astron. Astrophys. 304, 415 (1995)>
    =1995A&A...304..415V      (SIMBAD/NED BibCode)
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ADC_Keywords: Stars, variable; Stars, supergiant; Photometry, uvby, beta
Keywords: techniques: photometric -
          stars: individual: {eta} Car; variables; supergiants; oscillations

Description:
    We present and analyze two seasons of intense photometric monitoring
    in the Stroemgren uvbyH{beta} system of {eta} Carinae (October
    1992-August 1994). The luminous blue variable (LBV) in the core did
    not show much S Dor activity, i.e. it was in a relatively quiescent
    stage. This situation was very favourable for studying its optical
    micro variations. It appears that the central LBV pulsates (presumably
    in a non-radial mode) like other massive evolved stars, the {alpha}
    Cyg variables. The quasi-period is 58.56d. The linear ephemeris is:
    JD_max_=2448875.0 +58.56 E. Support was found for the existence of the
    presumed periodicity of 52.4d of the so-called "dimples", shallow dips
    in the light curve which only last for a few days. The cause may be
    the eclipse of a small companion or of a hot spot in an accretion
    disk. The H{beta} index became bluer by ~0.07mag during the last 11/2
    years and shows an oscillation in anti-phase with the 58.56d
    pulsation, suggesting that the HII region(s) responsible for the
    hydrogen line emission has a relatively high luminosity. This is
    another reason to suppose that a second luminous source, perhaps a
    luminous disk (with a hot spot), may be present in the {eta} Car
    system.

Objects:
    --------------------------------------------------
       RA  (2000)  DE     Name(s)
    --------------------------------------------------
    10 45 03.6 -59 41 03  eta Car = HR 4210 = HD 93308
    --------------------------------------------------

File Summary:
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  FileName      Lrecl  Records   Explanations
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ReadMe             80        .   This file
table1             64      285   Stroemgren uvbyH-beta photometry of Eta Car
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Byte-by-byte Description of file: table1
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   Bytes Format  Units   Label    Explanations
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   1- 11  F11.3  d       JD       Julian date
      12  A1     ---   u_JD       [:] Uncertainty flag on JD
  18- 23  F6.4   mag     ymag     []? y Stroemgren magnitude
  26- 31  F6.4   mag     bmag     []? b Stroemgren magnitude
  33- 39  F7.4   mag     vmag     []? v Stroemgren magnitude
  42- 47  F6.4   mag     umag     []? u Stroemgren magnitude
  50- 55  F6.4   mag     Hbmag    []? H{beta} Stroemgren magnitude
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(End)                                             Simona Mei [CDS]   26-Jul-1995