J/A+A/659/A71 ZDI maps of five young solar-type stars (Willamo+, 2022)
Zeeman-Doppler imaging of five young solar-type stars.
Willamo T., Lehtinen J.J., Hackman T., Kapyla M.J., Kochukhov O.,
Jeffers S.V., Korhonen H., Marsden S.C.
<Astron. Astrophys. 659, A71 (2022)>
=2022A&A...659A..71W 2022A&A...659A..71W (SIMBAD/NED BibCode)
ADC_Keywords: Stars, late-type ; Magnetic fields
Keywords: stars: activity - stars: magnetic field - stars: solar-type -
starspots
Abstract:
The magnetic activity of the Sun changes with the solar cycle. Similar
cycles are found in other stars as well, but their details are not
known to a similar degree. Characterising stellar magnetic cycles is
important for the understanding of the stellar and solar dynamos that
are driving the magnetic activity.
We present spectropolarimetric observations of five young, solar-type
stars and compare them to previous observations, with the aim to
identify and characterise stellar equivalents of the solar cycle.
We use Zeeman-Doppler imaging (ZDI) to map the surface magnetic field
and brightness of our targets. The magnetic field is decomposed into
spherical harmonic expansions, from which we report the strengths of
the axisymmetric versus non-axisymmetric and poloidal versus toroidal
components, and we compare them to the Rossby numbers of the stars.
We present five new ZDI maps of young, solar-type stars from December
2017. Of special interest is the case of V1358 Ori, which had gone
through a polarity reversal between our observations and earlier ones.
A less evident polarity reversal might also have occurred in HD 35296.
There is a preference for a more axisymmetric field, and possibly a
more toroidal field, for the more active stars with lower Rossby
number, but a larger sample should be studied to draw any strong
conclusions from this. For most of the individual stars, the amounts
of toroidal and poloidal field have stayed on levels similar to those
in earlier observations.
We find evidence for a magnetic polarity reversal having occurred in
V1358 Ori. An interesting target for future observations is
χ1 Ori, which may have a short magnetic cycle of a few years. The
correlation between the brightness maps and the magnetic field is
mostly poor, which could indicate the presence of small-scale magnetic
features of different polarities that cancel one another out and are
thus not resolved in our maps.
Description:
We present Zeeman-Doppler imaging (ZDI) maps, containing surface maps
of the radial, meridional and azimuthal components of the magnetic
field, and the brightness of BE Cet, χ1 Ori, HD 29615, HD 35296
and V1358 Ori. The epoch for the maps is December 2017. For V1358 Ori
we publish also one ZDI map from an earlier epoch, September 2013,
which is specified in the filename.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
stars.dat 60 5 List of studied stars
becet.dat 51 1876 ZDI map of BE Cet
chi1ori.dat 51 1876 ZDI map of χ1 Ori
hd29615.dat 51 1876 ZDI map of HD 29615
hd35296.dat 51 1876 ZDI map of HD 35296
v1358ori.dat 51 1876 ZDI map of V1358 Ori
v1358or2.dat 51 1876 ZDI map of V1358 Ori from September 2013
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Byte-by-byte Description of file: stars.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Name
12- 13 I2 h RAh Simbad Hour of Right Ascension (J2000.0)
15- 16 I2 min RAm Simbad Minute of Right Ascension (J2000.0)
18- 22 F5.2 s RAs Simbad Second of Right Ascension (J2000.0)
24 A1 --- DE- Simbad Sign of the Declination (J2000.0)
25- 26 I2 deg DEd Simbad Degree of Declination (J2000.0)
28- 29 I2 arcmin DEm Simbad Arcminute of Declination (J2000.0)
31- 34 F4.1 arcsec DEs Simbad Arcsecond of Declination (J2000.0)
36- 47 A12 --- FileName Name of the file with ZDI map
49- 60 A12 --- FileName2 Name of the second file with ZDI map
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Byte-by-byte Description of file: [bhcv]*.dat v1358ori.dat
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Bytes Format Units Label Explanations
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1- 7 F7.3 deg Lat Latitude
9- 15 F7.3 deg Lon Longitude
17- 24 F8.5 kG Brad Radial magnetic field
26- 33 F8.5 kG Bmer Meridional magnetic field
35- 42 F8.5 kG Bazi Azimuthal magnetic field
44- 51 F8.5 --- Brig Normalised brightness
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Acknowledgements:
Teemu Willamo, teemu.willamo(at)helsinki.fi
(End) T. Willamo [Univ. of Helsinki, Finland], P. Vannier [CDS] 27-Dec-2021