J/A+A/622/A170 V-band differential photometry for V889 Her (Willamo+, 2019)
Long-term spot monitoring on the young solar analogue V889 Herculis.
Willamo T., Hackman T., Lehtinen J.J., Kapyla M.J., Ilyin I., Henry G.W.,
Jetsu L., Kochukhov O., Piskunov N.
<Astron. Astrophys. 622, A170 (2019)>
=2019A&A...622A.170W 2019A&A...622A.170W (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Photometry
Keywords: stars: activity - starspots - stars: solar type -
stars: individual: HD 171488
Abstract:
Starspots are important manifestations of stellar magnetic activity.
By studying their behaviour in young solar analogues, we can unravel
the properties of their magnetic cycles. This gives crucial
information of the underlying dynamo process. Comparisons with the
solar cycle enable us to infer knowledge about how the solar dynamo
has evolved during the Sun's lifetime.
Here we study the correlation between photometric brightness
variations, spottedness and mean temperature in V889 Her, a young
solar analogue. Our data covers 18 years of spectroscopic and 25 years
of photometric observations.
We use Doppler imaging to derive temperature maps from high-resolution
spectra. We use the Continuous Period Search method to retrieve mean
V-magnitudes from photometric data.
Our Doppler imaging maps show a persistent polar spot structure
varying in strength. This structure is centered slightly off the
rotational pole. The mean temperature derived from the maps shows an
overall decreasing trend, as does the photometric mean brightness,
until it reaches its minimum around 2017. The filling factor of cool
spots, however, shows only a weak tendency to anti-correlate with the
decreasing mean brightness.
We interpret V889 Her to have entered into a grand maximum in its
activity. The clear relation between the mean temperature of the
Doppler imaging surface maps and the mean magnitude supports the
reliability of the Doppler images. The lack of correlation between the
mean magnitude and the spottedness may indicate that bright features
in the Doppler images are real.
Description:
We present the Johnson V-band differential photometry of V889 Her,
obtained with the Tennessee State University T3 0.4m Automatic
Photoelectric Telescope. The analysis of the data has been done using
the comparison star HD 171286; the V-magnitude of V889 Her is gained
by adding the V-magnitude of HD 171286 (V=6.84; Oja,
1987A&AS...71..561O 1987A&AS...71..561O) to each data point. For further analysis we use
the Continous Period Search-method (CPS; Lehtinen et al.,
2011A&A...527A.136L 2011A&A...527A.136L) to derive mean magnitudes for longer sets of
data.
Objects:
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RA (2000) DE Designation(s)
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18 34 20.10 +18 41 24.2 V889 Her = HD 171488
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
v889her.dat 19 2445 Differential photometry of V889 Her
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See also:
J/A+A/527/A136 : HD 116956 V-band differential light curve (Lehtinen+, 2011)
Byte-by-byte Description of file: v889her.dat
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Bytes Format Units Label Explanations
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1- 12 F12.4 d HJD Heliodentric Julian Date
15- 19 F5.3 mag DVmag Differential V-band photometry
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Acknowledgements:
Teemu Willamo, teemu.willamo(at)helsinki.fi
(End) Teemu Willamo [Helsinki Univ., Finland] Patricia Vannier [CDS] 05-Feb-2019