Guillout, P.Frasca, A.Klutsch, A.Marilli, E.Montes Gutiérrez, David2023-06-202023-06-202010-09Appenzeller, I., Bertout, C., & Stahl, O. 2005, A&A, 434, 1005 Cardelli, J. A., Clayton, G. C., & Mathis, J. S. 1989, ApJ, 345, 245 Chugainov, P. F., Lovkaya, M. N., & Petrov, P. P. 1991, Information Bulletin on Variable Stars, 3623, 1 Chugainov, P. F., Petrov, P. P., & Lovkaya, M. N. 1993, Izv. Krym. Astrofizicheskoj Obs., 88, 29 Cutri, R. M., Skrutskie, M. F., van Dyk, S., et al. 2003, The IRSA 2MASS AllSky Point Source Catalog, NASA/IPAC Infrared Science Dobashi, K., Uehara, H., Kandori, R., et al. 2005, PASJ, 57, 1 Droege, T. F., Richmond, M. W., Sallman, M. P., & Creager, R. P. 2006, PASP, 118, 1666 Feigelson, E. D. 1996, ApJ, 468, 306 Frasca, A., Alcalá, J. M., Covino, E., et al. 2003, A&A, 405, 149 Frasca, A., Guillout, P., Marilli, E., et al. 2006, A&A, 454, 301 Grenier, I. A., Lebrun, F., Arnaud, M., Dame, T. M., & Thaddeus, P. 1989, ApJ, 347, 231 Guillout, P., Schmitt, J. H. M. M., Egret, D., et al. 1999, A&A, 351, 1003 Guillout, P., Klutsch, A., Frasca, A., et al. 2009, A&A, 504, 829 Hauschildt, P. H., Allard, F., & Baron, E. 1999, ApJ, 512, 377 Hillenbrand, L., & FEPS Spitzer Legacy Science Team. 2006, Bull. Amer. Astron. Soc., 38, 910 Høg, E., Fabricius, C., Makarov, V. V., et al. 2000, A&A, 355, L27 Hubble, E. 1934, ApJ, 79, 8 Klutsch, A. 2008, Ph. D Thesis, ULP and Strasbourg Observatory Kun, M. 1998, ApJS, 115, 59 Kun, M., Kiss, Z. T., & Balog, Z. 2008, Handbook of Star-Forming Regions, ed. B. Reipurth, 1, 134 (San Francisco: ASP) Kun, M., Balog, Z., Kenyon, S. J., Mamajek, E. E., & Gutermuth, R. A. 2009, ApJS, 185, 451 Kurosawa, R., Harries, T. J., & Symington, N. H. 2006, MNRAS, 370, 580 Lada, C. J. 1987, IAU Symp., ed. M. Peimbert & J. Jugaku, 115, 1 López Santiago, J., Montes, D., Gálvez Ortiz, M. C., et al. 2010, A&A, 514, A97 Magazzu, A., Martin, E. L., Sterzik, M. F., et al. 1997, A&AS, 124, 449 Makarov, V. V., Zacharias, N., Hennessy, G. S., Harris, H. C., & Monet, A. K. B. 2007, ApJ, 668, L155 Meyer, M. R., Hillenbrand, L. A., Backman, D., et al. 2006, PASP, 118, 1690 Mizuno, A., Hayakawa, T., Yamaguchi, N., et al. 1998, ApJ, 507, L83 Monet, D. G., Levine, S. E., Canzian, B., et al. 2003, AJ, 125, 984 Montes, D., López Santiago, J., Fernández Figueroa, M. J., & Gálvez, M. C. 2001a, A&A, 379, 976 Montes, D., López Santiago, J., Gálvez, M. C., et al. 2001b, MNRAS, 328, 45 Moon, T. 1985, Ap&SS, 117, 261 Muzerolle, J., Calvet, N., & Hartmann, L. 2001, ApJ, 550, 944 Nations, H. L., Heckert, P. A., Mooney, C. B., et al. 1990, BAAS, 22, 1254 Olano, C. A., Meschin, P. I., & Niemela, V. S. 2006, MNRAS, 369, 867 Siess, L., Dufour, E., & Forestini, M. 2000, A&A, 358, 593 Sterzik, M. F., & Durisen, R. H. 1995, A&A, 304, L9 Sterzik, M. F., & Durisen, R. H. 1998, A&A, 339, 95 Tachihara, K., Toyoda, S., Onishi, T., et al. 2001, PASJ, 53, 1081 Tachihara, K., Neuhäuser, R., Kun, M., & Fukui, Y. 2005, A&A, 437, 919 Torres, C. A. O., Quast, G. R., Melo, C. H. F., & Sterzik, M. F. 2008, Handbook of Star Forming Regions, Vol. II, 757 Zacharias, N., Monet, D. G., Levine, S. E., et al. 2004, A&AS, 36, 1418 Zuckerman, B., & Song, I. 2004, ARA&A, 42, 6850004-636110.1051/0004-6361/201014799https://hdl.handle.net/20.500.14352/45053© ESO, 2010. We are grateful to the OHP night assistant staff in conducting our Key Program, and those of the OAC observatories for their support and help with the observations. We thank Luigia Santagati of INAF-Catania for the English revision of the text. This research made use of SIMBAD and VIZIER databases, operated at the CDS, Strasbourg, France. This publication uses ROSAT data. Part of this work was supported by the Universidad Complutense de Madrid (UCM), the Spanish MICINN, Ministerio de Ciencia e Innovación under grant AyA2008-00695 and the Comunidad Autónoma de Madrid, under PRICIT project S-2009/ESP-1496 (AstroMadrid).Context. During the course of a large spectroscopic survey of X-ray active late-type stars in the solar neighbourhood, we discovered four lithium-rich stars packed within just a few degrees on the sky. Although located in a sky area rich in CO molecular regions and dark clouds, the Cepheus-Cassiopeia complex, these very young stars are projected several degrees away from clouds in front of an area void of interstellar matter. As such, they are very good "isolated" T Tauri star candidates. Aims. We present optical observations of these stars conducted with 1-2 m class telescopes. We acquired high-resolution optical spectra as well as photometric data allowing us to investigate in detail their nature and physical parameters with the aim of testing the "runaway" and "in-situ" formation scenarios. Their kinematical properties are also analyzed to investigate their possible connection to already known stellar kinematic groups. Methods. We use the cross-correlation technique and other tools developed by us to derive accurate radial and rotational velocities and perform an automatic spectral classification. The spectral subtraction technique is used to infer chromospheric activity level in the Hα line core and clean the spectra of photospheric lines before measuring the equivalent width of the lithium absorption line. Results. Both physical (lithium content, chromospheric, and coronal activities) and kinematical indicators show that all stars are very young, with ages probably in the range 10-30 Myr. In particular, the spectral energy distribution of TYC4496-780-1 displays a strong near-and far-infrared excess, typical of T Tauri stars still surrounded by an accretion disc. They also share the same Galactic motion, proving that they form a homogeneous moving group of stars with the same origin. Conclusions. The most plausible explanation of how these "isolated" T Tauri stars formed is the "in-situ" model, although accurate distances are needed to clarify their connection with the Cepheus-Cassiopeia complex. The discovery of this loose association of "isolated" T Tauri stars can help to shed light on atypical formation processes of stars and planets in low-mass clouds.engjournal articlehttp://dx.doi.org/10.1051/0004-6361/201014799http://www.aanda.org/open access52All-sky surveyMolecular cloudsChromospheric activitySpectroscopic surveyCassiopeia regionStellar-systemsMass starsYoungSearchSampleAstrofísicaAstronomía (Física)