Bibcode
Suárez Mascareño, A.; Rebolo, R.; González Hernández, J. I.
Bibliographical reference
Astronomy and Astrophysics, Volume 595, id.A12, 14 pp.
Advertised on:
10
2016
Journal
Citations
150
Refereed citations
140
Description
Aims: We investigate the photometric modulation induced by
magnetic activity cycles and study the relationship between rotation
period and activity cycle(s) in late-type (FGKM) stars. Methods:
We analysed light curves, spanning up to nine years, of 125 nearby stars
provided by the All Sky Automated Survey (ASAS). The sample is mainly
composed of low-activity, main-sequence late-A to mid-M-type stars. We
performed a search for short (days) and long-term (years) periodic
variations in the photometry. We modelled the light curves with
combinations of sinusoids to measure the properties of these periodic
signals. To provide a better statistical interpretation of our results,
we complement our new results with results from previous similar works.
Results: We have been able to measure long-term photometric
cycles of 47 stars, out of which 39 have been derived with false alarm
probabilities (FAP) of less than 0.1 per cent. Rotational modulation was
also detected and rotational periods were measured in 36 stars. For 28
stars we have simultaneous measurements of activity cycles and
rotational periods, 17 of which are M-type stars. We measured both
photometric amplitudes and periods from sinusoidal fits. The measured
cycle periods range from 2 to 14 yr with photometric amplitudes in the
range of 5-20 mmag. We found that the distribution of cycle lengths for
the different spectral types is similar, as the mean cycle is 9.5 yr for
F-type stars, 6.7 yr for G-type stars, 8.5 yr for K-type stars, 6.0 yr
for early M-type stars, and 7.1 yr for mid-M-type stars. On the other
hand, the distribution of rotation periods is completely different,
trending to longer periods for later type stars, from a mean rotation of
8.6 days for F-type stars to 85.4 days in mid-M-type stars. The
amplitudes induced by magnetic cycles and rotation show a clear
correlation. A trend of photometric amplitudes with rotation period is
also outlined in the data. The amplitudes of the photometric variability
induced by activity cycles of main-sequence GK stars are lower than
those of early- and mid-M dwarfs for a given activity index. Using
spectroscopic data, we also provide an update in the empirical
relationship between the level of chromospheric activity as given by
log10R 'HK and the rotation periods.