Issue |
A&A
Volume 474, Number 2, November I 2007
|
|
---|---|---|
Page(s) | 345 - 353 | |
Section | Astrophysical processes | |
DOI | https://doi.org/10.1051/0004-6361:20078195 | |
Published online | 28 August 2007 |
The spectroscopic binary system Gl 375*
I. Orbital parameters and chromospheric activity
1
Instituto de Astronomía y Física del Espacio (IAFE), CC. 67, suc. 28, 1428 Buenos Aires, Argentina e-mail: rodrigo@iafe.uba.ar
2
Complejo Astronómico El Leoncito (CASLEO), San Juan, Argentina
Received:
30
June
2007
Accepted:
8
August
2007
Aims.We study the spectroscopic binary system Gl 375 to characterise its orbit and the spectral types and chromospheric activity levels of the components.
Methods.We employed medium-resolution echelle spectra obtained at the 2.15 m telescope at the Argentinian observatory CASLEO and photometric observations obtained from the ASAS database.
Results.We have separated the composite spectra
into those corresponding to both components. The separated spectra
allow us to confirm that the spectral types of both components are
similar (dMe3.5) and to obtain precise measurements of the orbital
period (P = 1.87844 days), minimum masses ( and
),
and other orbital parameters. The photometric observations exhibit a
sinusoidal variation with the same period as the orbital period. We
interpreted this as signs of active regions carried along with
rotation in a tidally synchronised system, and studied the evolution
of the amplitude of the modulation on longer timescales. Together
with the mean magnitude, the modulation exhibits a roughly cyclic
variation with a period of around 800 days. This periodicity is also
found in the flux of the Ca II K lines of both components, which
seem to be in phase.
Conclusions.The periodic changes in the three observables are interpreted as a sign of a stellar activity cycle. Both components appear to be in phase, which implies that they are magnetically connected. The measured cycle of ≈2.2 years (≈800 days) is consistent with previous determinations of activity cycles in similar stars.
Key words: binaries: spectroscopic / stars: activity / stars: chromospheres / stars: flare / stars: fundamental parameters / stars: late-type
© ESO, 2007
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