J/A+A/674/A143 EI Eri observing log of MUSICOS 1998 data (Kriskovics+, 2023)
EI Eridani: A star under the influence.
The effect of magnetic activity in the short and long term.
Kriskovics L., Kovari Z., Seli B., Olah K., Vida K., Henry G.W.,
Granzer T., Gorgei A.
<Astron. Astrophys., 674, A143 (2023)>
=2023A&A...674A.143K 2023A&A...674A.143K (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Observatory log ; Optical
Keywords: stars: activity - stars: imaging - starspots -
stars: individual: EI Eridani
Abstract:
Homogeneous photometric time series spanning decades provide a unique
opportunity to study the long-term cyclic behavior of active spotted
stars such as our target EI Eridani. In addition, with ultraprecise
space photometry data, it is possible to investigate the accompanying
flare activity in detail. However, the rotation period of ∼2 days for
EI Eri makes it impossible to achieve time-resolved surface images
from a single ground-based observing site. Therefore, for this
purpose, spectroscopic data from a multi-site observing campaign are
needed.
We use our photometric time series of more than 40yr to analyze the
long-term behavior of EI Eri. We investigate flare activity using
photometric data obtained with the Transiting Exoplanet Survey
Satellite (TESS). The MUlti-SIte Continuous Spectroscopy (MUSICOS)
campaign in 1998 was designed to achieve high-resolution,
multi-wavelength spectroscopic observations from many sites around the
globe, which meant that uninterrupted phase coverage of EI Eri became
available. We use these data to reconstruct successive
surface-temperature maps of the star in order to study the changes of
starspots on a very short timescale.
We used long-term seasonal period analysis of our photometric time
series to study changes in the rotational period. We also applied
short-term Fourier-transform to look for activity cycle-like changes.
We also studied the phase and frequency distribution of hand-selected
flares. We applied our multi-line Doppler imaging code to reconstruct
four consecutive Doppler images. These images were also used to
measure surface differential rotation with our cross-correlation
technique. In addition, we carried out tests to demonstrate how
Doppler imaging is affected by the fact that the data came from
several different instruments with different spectral resolutions.
Seasonal period analysis of the light curve reveals a smooth,
significant change in period, possibly indicating the evolution of
active latitudes. Temperature curves from B-V and V-I show slight
differences, indicating the activity of EI Eri is spot dominated.
Short-term Fourier transform reveals smoothly changing cycles of
between 4.5 and 5.5yr and of between 8.9 and 11.6yr. The time-resolved
spotted surface of EI Eri from Doppler imaging enabled us to follow
the evolution of the different surface features. Cross-correlating the
consecutive Doppler maps reveals surface shear of alpha=0.036±0.007.
Our tests validate our approach and show that the surface-temperature
distribution is adequately reconstructed by our method. The tests also
indicate how accurately the cross-correlation method can reproduce the
surface shear as a function of the spectral resolution.
Description:
Observing log of the MUSICOS 1998 data.
Objects:
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RA (2000) DE Designation(s)
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04 09 40.89 -07 53 34.1 EI Eridani = HD 26337
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb1.dat 29 90 Observing log of the MUSICOS 1998 data
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Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
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1- 12 F12.4 d HJD Heliocentric Julian date
14- 19 A6 --- Tel Observing facility
21- 25 F5.3 --- Phase Rotational phase
27- 29 A3 --- Used [yes/no ] Whether the measurement was used or not
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 28-Aug-2023