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Post Info TOPIC: V405 Andromeda
Blobrana


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RE: V405 Andromeda
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Title: Modelling of an eclipsing RS CVn-binary: V405 And
Authors: K. Vida, K. Oláh, Zs. Kovári

V405 And is an ultrafast-rotating (P_rot ~ 0.46 days) eclipsing binary. The system consists of a primary star with radiative core and convective envelope, and a fully convective secondary. Theories have shown, that stellar structure can depend on magnetic activity, i.e., magnetically active M-dwarfs should have larger radii. Earlier light curve modelling of V405 And indeed showed this behaviour: we found that the radius of the primary is significantly larger than the theoretically predicted value for inactive main sequence stars (the discrepancy is the largest of all known objects), while the secondary fits well to the mass-radius relation. By modelling our recently obtained light curves, which show significant changes of the spotted surface of the primary, we can find further proof for this phenomenon.

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Blobrana


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Title: Photospheric and chromospheric activity in V405 And: An M dwarf binary with components on the two sides of the full convection limit
Authors: K. Vida, K. Oláh, Zs. Kvári, H. Korhonen, J. Bartus, Zs. Hurta, K. Posztobányi
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Blobrana


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Posts: 131433
Date:
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Title: Photospheric and chromospheric activity in V405 And: An M dwarf binary with components on the two sides of the full convection limit
Authors: K. Vida, K. Oláh, Zs. Kvári, H. Korhonen, J. Bartus, Zs. Hurta, K. Posztobányi

We investigate the fast rotating (P_orb=P_rot=0.465d) active dwarf binary V405 And (M0V+M5V) using photometric BV(RI)_C and optical spectroscopic data. The light variation is caused by the combined effect of spottiness and binarity with a small eclipse. From the available light and radial velocity curves we estimate the system parameters. Three flare events happened during the observations: two were found in the spectroscopic data and one was observed photometrically in BV(RI)_C colours. An interesting eruptive phenomenon emerged from the photometric measurements which can be interpreted as a series of post-flare eruptions lasting for at least 3 orbits (rotations) of the system, originating from trans-equatorial magnetic loops, which connect the active regions in the two hemispheres. The two components of V405 And have masses well over and below the theoretical limit of full convection. This rare property makes the binary an ideal target for observing and testing models for stellar dynamo action.

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