J/A+A/454/295 Long-term photographic photometry of HK Lac (Froehlich+, 2006)
The RS CVn binary HK Lacertae: long-term photometry from Sonneberg Sky-Patrol
plates.
Froehlich H.-E., Kroll P., Strassmeier K.G.
<Astron. Astrophys. 454, 295 (2006)>
=2006A&A...454..295F 2006A&A...454..295F
ADC_Keywords: Stars, late-type ; Photometry, photographic ;
Photometry, special systems
Keywords: stars: activity - stars: individual: HK Lacertae -
stars: late-type - stars: rotation - stars: starspots
Abstract:
Long-term photographic photometry of the active long-period RS CVn
binary HK Lac (HD 209813) was obtained from more than 2000 Sonneberg
Sky-Patrol plates taken between 1956 and 1996. We achieve an internal
accuracy of 0.07mag. The correspondence with contemporaneous
high-precision photoelectric photometry from automatic telescopes is
striking and successfully demonstrates the feasibility of our
approach. Based on a Bayesian periodogram analysis, we improve
previously published cycle periods to 13.37±0.8 and 6.7±0.1-years,
and present evidence of an additional period of
9.48±0.13-years. This establishes the multi-periodicity of
dynamo action in these overactive stars as compared to the Sun. Of
course, the 6.7-years cycle may be an overtone of the dominating
13.4-years cycle. Our long-term photographic photometry even allowed
the detection of the star's mean rotational period of 24.35-days.
Description:
A photographic light-curve, from 1956 to 1996, of the RS CVn binary HK
Lacertae is presented. For each of the 2037 data points the Julian
Date (geocentric) and the BT magnitude (Tycho-2 photometric system) is
given. Brightnesses are with respect to the BT brightness of HD 210731
(BT=8.090mag).
Objects:
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RA (2000) DE Designation(s)
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22 04 56.6 +47 14 04 HK Lac = HIP 109002
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 24 2037 Julian Date and BT magnitude
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Seq Sequence number
7- 17 F11.3 --- JD Geocentric Julian Date at the middle of the
exposure
20- 24 F5.3 mag BTmag BT brightness in the tycho-2 system (1)
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Note (1): The Tycho-2 Catalogue of the 2.5 Million Brightest Stars
Hog et al., 2000, Cat. I/259
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Acknowledgements: Hans-Erich Froehlich, hefroehlich(at)aip.de
(End) Patricia Vannier [CDS] 09-Sep-2005