| Title: |
Correlation between activity indicators: H$\alpha$ and Ca II lines in M-dwarf stars |
| Authors: |
Bustos, R. V. Ibañez, Buccino, A. P., Flores, M., Martinez, C. F., Mauas, P. J. D. |
| Source: |
A&A 672, A37 (2023) |
| Publication Year: |
2023 |
| Collection: |
Astrophysics |
| Subject Terms: |
Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Earth and Planetary Astrophysics |
| More Details: |
Different approaches have been adopted to study short- and long-term stellar magnetic activity, and although the mechanisms by which low-mass stars generate large-scale magnetic fields are not well understood, it is known that stellar rotation plays a key role. There are stars that show a cyclical behaviour in their activity which can be explained by solar dynamo or $\alpha\Omega$ dynamo models. However, when studying late-type dwarf stars, it is necessary to implement other indicators to analyse their magnetic activity. In the present work, we perform a comparative study between the best-known activity indicators so far defined from the Ca II and H$\alpha$ lines to analyse M-dwarf stars. We studied a sample of 29 M stars with different chromospheric activity levels and spectral classes ranging from dM0 to dM6. To do so, we employed 1796 wide range spectra from different instruments with a median time span of observations of 21 yr. In addition, we complemented our data with photometric observations from the TESS space mission for better stellar characterisation and short-term analysis. We obtained a good and significant correlation ($rho = 0.91$) between the indexes defined from the two lines for the whole set of stars in the sample. However, we found that there is a deviation for faster rotators (with $P_{rot} < 4$ days) and higher flare activity (at least one flare per day). There is an overall positive correlation between Ca II and H$\alpha$ emission in dM stars, except during flare events. In particular, we found that low-energy high-frequency flares could be responsible for the deviation in the linear trend in fast-rotator M dwarfs. This implies that the rotation period could be a fundamental parameter to study the stellar activity and that the rotation could drive the magnetic dynamo in low-mass active stars. |
| Document Type: |
Working Paper |
| DOI: |
10.1051/0004-6361/202245352 |
| Access URL: |
http://arxiv.org/abs/2303.17237 |
| Accession Number: |
edsarx.2303.17237 |
| Database: |
arXiv |
