Young solar type active stars: the TYC 2627-638-1 system ^*,**,***

¹ Konkoly Observatory of the Hungarian Academy of Sciences, 1525 Budapest, Hungary e-mail: olah@konkoly.hu
² ESO, Karl-Schwarzschild Strasse 2, 85748 Garching bei Munchen, Germany
³ Astrophysical Institute Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
⁴ Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Mariesvej 30, 2100 Kbh Ø, Denmark
⁵ Nordic Optical Telescope, Apartado 474, 38700 Santa Cruz de La Palma, Santa Cruz de Tenerife, Spain
⁶ Tartu Observatoorium, Tõravere 61602, Estonia
⁷ Astronomický ústav, Akademie věd České republiky, 25165 Ondřejov, Czech Republic

Received: 14 July 2009
Accepted: 6 March 2010

Abstract

We present BV(RI)_C and JHKs photometry and low- and high-resolution spectroscopy of the 11th mag G-type star TYC 2627-638-1. Our investigation reveals that the target is separated into two young, early-G-type main-sequence (or late pre-main-sequence) stars, which are most probably bound and form a wide binary system. A substellar body orbits the brighter component as implied by radial velocity variations. The brighter component possibly also has a faint, later type stellar companion. 
Both components of the wide binary have clear emission cores in the Ca ii H&K lines and filled-in Hα absorption, indicating that both stars are chromospherically active. Our photometric time series reveals clear but only a few hundredths of a magnitude amplitude rotational modulation, which is most likely due to cool starspots. Two distinct periods, near 3.5 and 3.7 days, are found in the brightness variations. Photometry obtained separately of the two components of the wide binary show that these periodicities belong to the brighter star. The fainter component shows a much slower light variation of about 0.3 mag. amplitude. In addition, long-term changes in the brightness of both stars are seen. The spectral energy distribution shows a strong near-infrared excess in the fainter component of the wide binary.