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J/ApJ/439/983     Radio & optical observation of UX Arietis (Elias+ 1995)
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Correlations between the flaring radio emission and starspot distribution of
UX Arietis
    Elias II. N.M., Quirrenbach A., Witzel A., Naundorf C.E., Wegner R.,
    Guinan E.F., McCook G.P.
   <Astrophys. J. 439, 983 (1995)>
   =1995ApJ...439..983E
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ADC_Keywords: Stars, flare ; Photometry ; Radio lines
Keywords: radio continuum: stars - stars: flare - stars: individual (UX Arietis)

Abstract:
    We have observed UX Arietis at C band (6cm) for 3 weeks with four VLA
    antennas. The temporal coverage during the program was approximately
    three scans per day. A few days into the VLA program, UX Ari began a
    radio flaring period which lasted for at least 2 weeks. All the radio
    fluxes were above the system noise during this episode, but the
    largest values (up to 270mJy) occurred close to 0.0 phase. This
    phasing is confirmed by the UX Ari radio observations of Neidhoefer,
    Massi, & Chiuderi-Drago (1993A&A...278L..51N).
    Visible-band light curves of UX Ari were obtained both during and
    after our radio observations; the peak-to-peak variation in all
    filters was ~0.2mag. The light curves indicate that the maximum
    starspot visibility occurred very close to 0.0 phase, the same phase
    as the radio maxima. Closer comparison of our radio and optical light
    curves indicates that they are almost perfectly anticorrelated. A
    similar radio/optical correlation has been found by Lim et al.
    (1992ApJ...388L..27L) and Lim et al. (1994ApJ...430..332L) for the
    single K0 V star AB Dor.
    We make the following conclusions from our observations. First, the
    episodes of long-term (~hours to days) radio flaring were modulated by
    stellar eclipses. Second, the flares were located close to the
    starspot groups. Third, the sizes of the flares were comparable to
    sizes of the starspot groups, which is consistent with nonthermal
    emission of brightness temperature T_b~10^10-10^13K. Fourth, the radio
    emission arose only from the midlatitude starspot groups. Last, the
    radio flares emitted their radiation nearly normal to the stellar
    surface.

Objects:
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       RA   (2000)   DE    Designation(s)
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     03 26 35.1  +28 42 59  UX Ari = HD 21242
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File Summary:
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 FileName    Lrecl    Records    Explanations
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ReadMe          80          .    This file
radio           23         42    UX Arietis C-band VLA observations
optical         34        418    UX Arietis visible-band photometry
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Byte-by-byte Description of file: radio
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   Bytes Format  Units   Label        Explanations
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   1- 12  F12.4  d       HJD          Heliocentric Julian Date
  14- 19  F6.4   ---     Phase        [0/1[ Phase
  21- 23  I3     mJy     Flux         Radio flux
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Byte-by-byte Description of file: optical
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   Bytes Format  Units   Label        Explanations
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   1- 13  F13.5  d       HJD          Heliocentric Julian Date
  15- 21  F7.5   ---     Phase        [0/1[ Phase
  23- 27  F5.3   mag     dMag        *Differential magnitude, Var - Comp
  29- 30  A2     ---     Filter      *Filter: b', y, r
  32- 34  A3     ---     Obs         *Observatory, VUO or APT
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Note on dMag:
  Comparison star was 62 Ari (HR 1012, HD 20825; V=+5.52; B-V=+1.10; G5 III).
  Check star was HR 999 (HD 20644, V=+4.47, B-V=+1.54; K4 III).
  62 Ari has been used previously in photometric studies of UX Ari and appears
  to be constant in light.
Note on Filter:
  Intermediate-band interference filters:
  b' - lambda = 453nm, FWHM = 15nm
  y  - Stroemgren y, lambda = 550nm, FWHM = 35nm
  r  - lambda = 660nm, FWHM = 28nm, also known as H-alpha I
Note on Obs:
  VUO - Villanova University Observatory,
  APT - Automatic Photometric Telescope, Mount Hopkins, Arizona
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Origin: AAS CD-ROM series, Volume 4, 1995         Lee Brotzman [ADS] 06-May-1995
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(End)                                                         [CDS]  11-Jul-1995