Identification of red high proper-motion objects in Tycho-2 and 2MASS catalogues using Virtual Observatory tools

• Published in: Astronomy and astrophysics (Berlin) 2012-03, Vol.539, p.A86
• Main Authors: Jiménez-Esteban, F. M., Caballero, J. A., Dorda, R., Miles-Páez, P. A., Solano, E.
• Format: Article
• Language: English
• Subjects: astronomical databases: miscellaneous; Astronomy; Earth, ocean, space; Exact sciences and technology; stars: chemically peculiar; stars: late-type; stars: oscillations; stars: peculiar; virtual observatory tools
• ISSN: 0004-6361; 1432-0746
• DOI: 10.1051/0004-6361/201118375

Aims. With available Virtual Observatory tools, we looked for new M dwarfs in the solar neighbourhood and M giants with high tangential velocities. Methods. From an all-sky cross-match between the optical Tycho-2 and the near-infrared 2MASS catalogues, we selected objects with proper motions μ  >  50 mas yr-1 and very red VT − Ks colours. For the most interesting targets, we collected multi-wavelength photometry, constructed spectral energy distributions, estimated effective temperatures and surface gravities from fits to atmospheric models, performed time-series analysis of ASAS V-band light curves, and assigned spectral types from low-resolution spectroscopy obtained with CAFOS at the 2.2 m Calar Alto telescope. Results. We got a sample of 59 bright red high proper-motion objects, including fifty red giants, four red dwarfs, and five objects reported in this work for the first time. The five new stars have magnitudes VT  ≈  10.8–11.3 mag, reduced proper motions midway between known dwarfs and giants, near-infrared colours typical of giants, and effective temperatures Teff  ≈  2900–3400 K. From our time-series analysis, we discovered a long secondary period in Ruber 4 and an extremely long primary period in Ruber 6. With the CAFOS spectra, we confirmed the red giant nature of Ruber 7 and 8, the last of which seems to be one of the brightest metal-poor M giants ever identified.