1. Una búsqueda de compañeros de estrellas Luyten con el Observatorio Virtual A search for companions to Luyten stars with the Virtual Observatory José A. Caballero 1 F. Xavier Miret 2 Joan Genebriera 3 Tòfol Tobal 2 Jordi Cairol 2 David Montes 1 1: Dpto. de Astrofísica, Universidad Complutense de Madrd 2: Observatori Astronòmic del Garraf, Barcelona 3: Observatorio de Tacande, La Palma

2. Albus 1 (Caballero & Solano 2007, ApJ, 665, L151) Serendipitous discovery of a very bright white dwarf candidate......that is actually one of the brightest He-B subdwarfs (Vennes, Kawka & Smith 2007, ApJ, 668, L59; A. Ulla et al. in prep.)

3. Koenigstuhl 1 AB (Caballero 2007a, A&A, 462, L61) The (second) widest ultracool binary: a challenge for very low- mass formation ejection scenarios! Seven astrometric epochs since 1977.6 until 2004.0:  = 77.76(7) arcsec d = 23(2) pc r = 1800(170) AU M A = 0.103(6) M sol M B = 0.079(4) M sol

4. Koenigstuhl 2 AB (Caballero 2007d, ApJ, 667, 520) A new very low-mass star in a wide binary: the third widest system with M A + M B < 0.4 M sol (in a draw) Primary: LP 655-23 (Luyten 1979) Secondary: 2M0430-08 (M8.0V; Cruz et al. 2003) r = 450(40) AU M A = 0.26(4) M sol M B = 0.086(4) M sol

5. Koenigstuhl 3 ABC (Caballero 2007d, ApJ, 667, 520) The widest system containing an L dwarf component Primary: HD 221356 (F8.0V; Hipparcos) Secondary: 2M2331-04AB (M8.0V+L3.0V; Gizis et al. 2000, 2003)  = 7.530(7) arcmin ! r = 11900(300) AU M A = 1.02(7) M sol M BC = 0.088+0.072 M sol And Koenigstuhl 4 AB is coming! (Caballero, in prep.) Frequency of wide multiples with late- type (>M5) components: 5.0 ± 1.8 %

6. The Garraf survey: an Aladin-based search for common-, high-proper motion pairs The New Luyten Two Tenths (NLTT) catalogue (Luyten 1979),  > 0.2 arcsec a -1 Improved astrometry in Salim & Gould (2003): 36 000 stars Selection: proper motions between 0.5 and 1.0 arcsec a -1 Still 1947 stars! Using Aladin instead of SuperCOSMOS Science Archive Still a lot of work one person...

7. The Garraf survey: : X.Miret, T.Tobal and J.Cairol at the Observatori Astrònomic del Garraf OAG (1976): a non-proffesional centre dedicated to the study of visual double stars OAG revised the Comellas’ 1973.0 and 1980.0 catalogues and coordinated most of non- proffesional observations of doubles in Spain from 1990 to 2003 OAG is one the main measurement providers of the USNO Washington Double Stars catalogue (10 4 )

8. The Garraf survey: Methodology Data loading and cross-matching: USNO-B1+2MASS Proper-motion diagram and candidate selection Recovery of known pairs with incorrect USNO-B1 proper motions with the “proper motion filter” One-by-one inspection of all selected binary candidates (SIMBAD, CCDM, Tycho-2...)

9. The Garraf Survey Current status ~160 common-  candidate companions studied to date 86 rejected systems with bad USNO-B1 astrometry 8 pairs with different USNO-B1 proper motions 20 physical systems with both star components in Hipparcos 29 physical systems with only one star component in Hipparcos 19 physical systems with no components in Hipparcos 6 new serendipitously-discovered physical systems...

10. Joan Genebriera: The Tacande astro-photometric follow-up A battery of “small” telescopes in La Palma: 40, 20, 15, 12, 9 cm 40 cm Cassegrain Relay, F6/5, with a CCD ST8XE

11. Garraf 1AB: An example of serendipitous discovery... A: G 125-15, M4.5e, X-ray, variable, age ~ 300 Ma (Daemgen et al. 2007) B: G 125-14, M5.5? Known binary in Giclas et al. (1971)

12. Garraf 1AB: A bright, young, very wide, low-mass binary in the solar neighbourhood Multi-epoch relative astrometry: 1952 Jul 17 POSSI Red 1988 Jun 13 POSSII Blue 1992 Aug 31 POSSII Red 1993 Jun 13 POSSII Infrared 1998 Jun 01 2MASS 2001 Aug 26 CMC14 2008 Mar 07 Tacande Age?  = 46.0 ± 0.3 arcsec  = 347.34 ± 0.16 deg d = 17 +6 -5 pc r = 800 +300 -200 AU M A = 0.21 +0.08 -0.05 M sol M B = 0. 12 +0.04 -0.03 M sol

13. Garraf 1 AB Optical imaging and low-resolution spectroscopy of Garraf 1AB with CAFOS / 2.2 m by David Montes M4.5e + M5.0:e. Accurate BVRI magnitudes. New astrometric epoch (2008 Apr 30)

14. Conclusions A search for companions to Luyten stars with the Virtual Observatory What will be a trained investigator be able do with SDSS + UKIDSS + LSST + GAIA...?