J/ApJ/439/983 Radio & optical observation of UX Arietis (Elias+ 1995)
Correlations between the flaring radio emission and starspot distribution of
UX Arietis
Elias N.M. II, Quirrenbach A., Witzel A., Naundorf C.E., Wegner R.,
Guinan E.F., McCook G.P.
<Astrophys. J. 439, 983 (1995)>
=1995ApJ...439..983E 1995ApJ...439..983E
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 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 1992ApJ...388L..27L) and Lim et al. (1994ApJ...430..332L 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∼1010-1013K. 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
(End) [CDS] 11-Jul-1995