The weak-line T Tauri star V410 Tau

II. A flaring star

¹ Instituto de Astrofísica de Andalucía, CSIC, Camino Bajo de Huétor 24, 18008 Granada, Spain e-mail: matilde@iaa.es
² INAF - Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
³ USRA/USNO Flagstaff Station, PO Box 1149, Flagstaff, AZ 86002-1149, USA
⁴ Ulug Beg Astronomical Institute, Astronomicheskaya 33, 700052 Tashkent, Uzbekistan
⁵ Centro de Astrofisica da Universidade do Porto, Rua das Estrelas, 4150 Porto, Portugal
⁶ Departamento de Matemática Aplicada, Faculdade de Cíencas da Universidade do Porto, 4169 Porto, Portugal
⁷ Departamento de Matemática, Instituto Superior de Engenharia do Porto, 4150 Porto, Portugal
⁸ Thüringer Landessternwarte, Karl-Schwarzschild-Observatorium, Sternwarte 5, 07778 Tautenburg, Germany

Received: 7 October 2003
Accepted: 3 July 2004

Abstract

We show that V410 Tau, a weak-line T Tauri star, is a flaring star. This result comes from an intensive, coordinated monitoring campaign carried out in November 2001 at visible and X-ray wavelength ranges. It is confirmed by previous, isolated observations found in the literature. Flares tend to occur mainly around the star's minimum brightness, when the most active regions face us.
We report on the strongest flare detected up to now on this star, for which we have obtained simultaneous visible Strömgren photometry and intermediate resolution spectroscopy. We derive decay times from 3 to 0.7 h at several wavelengths for the continuum in the 3600-5600 Å range. We estimate the energy involved in this and the other flares for which we have good time sampling, and conclude that the strongest event, at least, could have important consequences for the matter in the surroundings of the star. If similar events took place on the young Sun and lasted for several Myr, they could explain the anomalous abundances of elemental isotopes found in some meteorites. They could have also contributed to eliminate part of the primary atmospheres of the planet embryos and would have provided enough energy for the melting of solid iron-magnesium silicates, a process that may explain the presence of chondrules in chondritic meteorites.
High resolution spectroscopy of the H_α emission line in the quiescent states of V410 Tau enables us to study the variability of the broad component. We suggest that this component is related to microflaring activity, such as the one observed on more evolved, magnetically-active stars. The large velocities and the energy associated with this component support this hypothesis.