A spectroscopic survey of the youngest field stars in the solar neighbourhood

Aims. We present the first results of an ambitious ground-based observation programme conducted on 1–4 m class telescopes. Our sample consists of 1097 active and presumably young stars, all of them being optical (Tycho Catalogue) counterparts of ROSAT AllSky Survey X-ray sources in the northern hemisphere. In this paper, we concentrate on the optically brightest (VT 9. m 5) candidates (704 objects). We acquired high-resolution optical spectroscopy in the Hα and/or lithium spectral regions for 426 of such stars without relevant data in the literature. We describe the star sample and the observations and we start to discuss the physical properties of the investigated stars. Methods. We used a cross-correlation technique and other tools developed by us to derive accurate radial and rotational velocities and to perform an automatic spectral classification for both single stars and double-lined systems. The spectral subtraction technique was used to derive chromospheric activity levels and lithium abundances. We estimated the fraction of young single stars and multiple systems in stellar soft X-ray surveys and the contamination by more evolved systems, like RS CVn binaries. We classified stars on the basis of their lithium abundance and give a glimpse of their sky distribution. Results. The sample appears to be a mixture of quite young Pleiades-like and Hyades-like stars plus an older lithium-poor population probably born within the last 1–2 Gyr. Seven stars with a lithium abundance compatible with the age of IC 2602 (about 30 Myr) or even younger were detected as well, although two appear to be lithium-rich giants.The discovery of a large number of highly or moderately lithium-rich giants is another outcome of the present survey. Conclusions. The contamination of soft X-ray surveys by old systems in which the activity level is enhanced by tidal synchronisation is not negligible, especially for K-type stars. Five stars with lithium content close to the primordial abundance are probably associated with already known moving groups in the solar neighbourhood. Some of them are good post-T Tauri candidates according to their positions in the HR diagram.

[1]  M. Skrutskie,et al.  The Two Micron All Sky Survey (2MASS) , 2006 .

[2]  U. Heiter,et al.  Giants in the Local Region , 2007 .

[3]  R. Neuhäuser.  Low-mass pre-main sequence stars and their X-ray emission. , 1997 .

[4]  M. A. Terra,et al.  On 7Li Enrichment by Low-Mass Metal-Poor Red Giant Branch Stars. , 2000, The Astrophysical journal.

[5]  D. Lambert,et al.  Rapidly Rotating Lithium-rich K Giants: The New Case of the Giant PDS 365 , 2002, astro-ph/0202158.

[6]  John R. Stauffer,et al.  The evolution of the lithium abundances of solar-type stars. III - The Pleiades , 1993 .

[7]  C. Soubiran,et al.  On-line determination of stellar atmospheric parameters $T_{\mathrm{eff}}$, $\log g$, [Fe/H] from ELODIE echelle spectra - II. The library of F5 to K7 stars , 1998 .

[8]  B. Zuckerman,et al.  Identification of a Nearby Stellar Association in theHipparcos Catalog: Implications for Recent, Local Star Formation , 2000, astro-ph/0002461.

[9]  M. Giampapa,et al.  Rotational Velocities and Chromospheric/Coronal Activity of Low-Mass Stars in the Young Open Clusters IC 2391 and IC 2602 , 1997 .

[10]  J. Munn,et al.  The USNO-B Catalog , 2002, astro-ph/0210694.

[11]  G. Torres,et al.  The Eclipsing Binary System AR Monocerotis , 2005 .

[12]  F. Favata,et al.  The stellar population of the Rosat North Ecliptic Pole survey , 2008, 0804.1253.

[13]  David R. Soderblom,et al.  High-Resolution Spectroscopy of Some Very Active Southern Stars , 1998, astro-ph/9803111.

[14]  D. A. Hunter,et al.  A library of stellar spectra. , 1984 .

[15]  Newly discovered active binaries in the RasTyc sample of stellar X-ray sources. I. Orbital and physi , 2006, astro-ph/0610591.

[16]  C. A. O. Torres,et al.  Search for associations containing young stars (SACY). I. Sample and searching method , 2006 .

[17]  V. Makarov.  Precision Kinematics and Related Parameters of the α Persei Open Cluster , 2006 .

[18]  G. L. Wycoff,et al.  The Tycho Double Star Catalogue , 2002 .

[19]  A. Klutsch,et al.  New triple systems in the RasTyc sample of stellar X-ray sources ,, , 2008, 0807.4470.

[20]  F. R. Harnden,et al.  Results from an extensive Einstein stellar survey. , 1981 .

[21]  M. Kun,et al.  Search for new T Tauri stars in the Cepheus-Cassiopeia region , 2005 .

[22]  E. Covino,et al.  Identification of a complete sample of northern ROSAT All-Sky Survey X-ray sources. VIII. The late-type stellar component , 2004, astro-ph/0412188.

[23]  R. Paul Butler,et al.  Radial Velocities for 889 Late-Type Stars , 2001, astro-ph/0112477.

[24]  N. Gehrels,et al.  The Geminga supernova as a possible cause of the local interstellar bubble , 1993, Nature.

[25]  France.,et al.  The accretion of brown dwarfs and planets by giant stars: I. Asymptotic giant branch stars , 1998, astro-ph/9812220.

[26]  J. Franco,et al.  The Kinematics of Stars Emerging from Expanding Shells: An Analysis of the Gould Belt , 1999 .

[27]  E. H. Olsen,et al.  Absolute dimensions of solar-type eclipsing binaries. - I. $\mathit{uvby}$ light curves for HS Aqr, KX Aqr, AL Ari, V963 Cen, MR Del, NY Hya, DU Leo, UW LMi, and V358 Pup , 2001 .

[28]  E. Covino,et al.  REM near-IR and optical photometric monitoring of pre-main sequence stars in Orion. Rotation periods , 2009, 0911.0760.

[29]  G. Herbig.  Chromospheric H alpha emission in F8-G3 dwarfs and its connection with the T Tauri stars. , 1985 .

[30]  J. Schmitt,et al.  Young Cool Stars in the Solar Neighborhood. , 1997 .

[31]  L. Eyer,et al.  New periodic variables from the Hipparcos epoch photometry , 2002 .

[32]  Klaus G. Strassmeier,et al.  The Vienna-KPNO search for Doppler-imaging candidate stars - I. A catalog of stellar-activity indicators for 1058 late-type Hipparcos stars , 2000 .

[33]  D. Soderblom,et al.  Rotation and chromospheric emission among F, G, and K dwarfs of the Pleiades , 1993 .

[34]  Munetaka Ueno,et al.  The AKARI/IRC mid-infrared all-sky survey , 2010, 1003.0270.

[35]  David R. Soderblom,et al.  The evolution of the lithium abundances of solar-type stars. II - The Ursa Major Group , 1993 .

[36]  E. Alfaro,et al.  Hierarchical Star Formation: Stars and Stellar Clusters in the Gould Belt , 2009, 0903.0596.

[37]  J. Li,et al.  Newly discovered candidate weak-line T Tauri stars in the surrounding area of the Taurus-Auriga region , 1998 .

[38]  Michel Mayor,et al.  ELODIE: A spectrograph for accurate radial velocity measurements , 1996 .

[39]  W. Voges,et al.  Identification of a Complete Sample of Northern ROSAT All-Sky Survey X-Ray Sources. III. The Catalog , 1998 .

[40]  M. C. Gálvez-Ortiz,et al.  A high-resolution spectroscopic survey of late-type stars: chromospheric activity, rotation, kinematics, and age , 2010, 1002.1663.

[41]  Charles J. Lada,et al.  Star formation: from OB associations to protostars , 1987 .

[42]  Lynne Hillenbrand,et al.  THE PALOMAR/KECK ADAPTIVE OPTICS SURVEY OF YOUNG SOLAR ANALOGS: EVIDENCE FOR A UNIVERSAL COMPANION MASS FUNCTION , 2008, 0808.2982.

[43]  S. Udry,et al.  Towards a New Set of High-Precision Radial-Velocity Standard Stars , 1999 .

[44]  Elena Schilbach,et al.  Astrophysical supplements to the ASCC‐2.5. II. Membership probabilities in 520 Galactic open cluster sky areas , 2004 .

[45]  G. Henry,et al.  An Automated Search for Variability in Chromospherically Active Stars , 1995 .

[46]  3D dynamical evolution of the interstellar gas in the Gould Belt , 2003, astro-ph/0303516.

[47]  Wolfgang Voges,et al.  Identification of a complete sample of northern ROSAT All-Sky Survey X-ray sources - II. The optical observations , 1997 .

[48]  D. Montes,et al.  Discovery of “isolated” co-moving T Tauri stars in Cepheus , 2010, 1009.2587.

[49]  RADIAL VELOCITY STUDIES OF CLOSE BINARY STARS. XIII , 2008, 0805.1695.

[50]  L. Girardi,et al.  Evolutionary tracks and isochrones for low- and intermediate-mass stars: From 0.15 to 7 , and from to 0.03 , 1999, astro-ph/9910164.

[51]  K. Reinsch,et al.  Identification of selected sources from the ROSAT Galactic Plane Survey. I. , 1997, astro-ph/9712208.

[52]  E. Feigelson.  Dispersed T Tauri stars and galactic star formation , 1996 .

[53]  D. Soderblom,et al.  The evolution of the lithium abundances of solar-type stars. I. The Hyades and Coma Berenices clusters , 1990 .

[54]  M. Schwartz,et al.  The TW Hydrae Association: Discovery of T Tauri Star Members Near HR 4796 , 2001 .

[55]  F. Fekel,et al.  Lithium and rapid rotation in chromospherically active single giants , 1993 .

[56]  M. Turatto,et al.  RACE-OC project: Rotation and variability of young stellar associations within 100 pc , 2010, 1004.1959.

[57]  R. Rutledge,et al.  XID II: STATISTICAL CROSS-ASSOCIATION OF ROSAT BRIGHT SOURCE CATALOG X-RAY SOURCES WITH 2MASS POINT SOURCE CATALOG NEAR-INFRARED SOURCES , 2009, 0910.3229.

[58]  B. Castilho,et al.  Discovery of new isolated T Tauri stars , 1989 .

[59]  W. Ritchey,et al.  Applications of magnetic resonance imaging to ion‐exchange resins , 1995 .

[60]  E. Martín,et al.  On a Rapid Lithium Enrichment and Depletion of K Giant Stars , 1997, astro-ph/9703131.

[61]  C. Ducourant,et al.  Pre-main sequence star Proper Motion Catalogue , 2005 .

[62]  Sofia Randich,et al.  Time scales of Li evolution: A Homogeneous analysis of open clusters from ZAMS to late-MS , 2005 .

[63]  Eric Stempels,et al.  Cool Stars, Stellar Systems and the Sun. , 2009 .

[64]  N. Bochkarev.  Local interstellar medium , 1987 .

[65]  S. Udry,et al.  Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data: Revisiting the concept of superclusters , 2004, astro-ph/0409579.

[66]  J. Topping,et al.  Errors of Observation and Their Treatment , 1957 .

[67]  J. Tonry,et al.  A survey of galaxy redshifts. I. Data reduction techniques. , 1979 .

[68]  W. Voges,et al.  The Hamburg/RASS Catalogue of optical identifications. Northern high-galactic latitude ROSAT Bright , 2003, astro-ph/0305535.

[69]  J. E. Gunn,et al.  Stellar spectrophotometric atlas, wavelengths from 3130 to 10800 A , 1983 .

[70]  P. Prugniel,et al.  A database of high and medium-resolution stellar spectra ?;?? , 2001, astro-ph/0101378.

[71]  T. Umemoto,et al.  Erratum: Atlas and Catalog of Dark Clouds Based on Digitized Sky Survey I , 2005 .

[72]  H. Froehlich.  The differential rotation of epsilon Eri from MOST data , 2007, 0711.0806.

[73]  U. S. Paulo,et al.  Polarimetry of Li-rich giants , 2005, astro-ph/0512237.

[74]  S. Mark Ammons,et al.  The N2K Consortium. IV. New Temperatures and Metallicities for More than 100,000 FGK Dwarfs , 2005, astro-ph/0510237.

[75]  Mark E. Cornell,et al.  A New Library of Stellar Optical Spectra , 1992 .

[76]  L. V. Mirzoi︠a︡n.  Problems of physics and evolution of the universe = Вопросы физики и эволюции космса = Les Problémes de physique et d' évolution de l' universe , 1978 .

[77]  D. Dragomir,et al.  Spectral Classification of Optical Counterparts to ROSAT All-Sky Survey X-Ray Sources , 2007, astro-ph/0702446.

[78]  M. Sterzik,et al.  Search for associations containing young stars (SACY) - III. Ages and Li abundances , 2009, 0909.0677.

[79]  S. C. Barden,et al.  A study of short-period RS Canum Venaticorum and W Ursae Majoris binary systems - The global nature of H-alpha , 1985 .

[80]  Chromospheric activity, lithium and radial velocities of single late-type stars possible members of young moving groups , 2001, astro-ph/0110066.

[81]  A. Turner,et al.  Properties of main-sequence eclipsing binaries : into the G stars with HS Aurigae, FL Lyrae and EW Orionis. , 1986 .

[82]  Ben Zuckerman,et al.  The AB Doradus Moving Group , 2004 .

[83]  E. Martín,et al.  Weak and Post-T Tauri Stars around B-Type Members of the Scorpius-Centaurus OB Association , 1998 .

[84]  Michael W. Richmond,et al.  TASS Mark IV Photometric Survey of the Northern Sky , 2006 .

[85]  B. Skiff,et al.  VizieR Online Data Catalog , 2009 .

[86]  P. Prugniel,et al.  The ELODIE Archive , 2004, astro-ph/0405025.

[87]  R. Reza.  Lithium Rich Red Giant Branch Stars , 2006 .

[88]  N. Scoville,et al.  Giant molecular clouds in the galaxy. 1. The axisymmetric distribution of H , 1984 .

[89]  F. V. Leeuwen.  Validation of the new Hipparcos reduction , 2007, 0708.1752.

[90]  The Carina-Near Moving Group , 2006, astro-ph/0609041.

[91]  A. Robin,et al.  A synthetic view on structure and evolution of the Milky Way , 2003 .

[92]  A. G. W. Cameron,et al.  Lithium and the s-process in red-giant stars , 1971 .

[93]  C. Soubiran,et al.  The PASTEL catalogue of stellar parameters , 2010, 1004.1069.

[94]  L. Hillenbrand,et al.  High-Dispersion Optical Spectra of Nearby Stars Younger Than the Sun , 2007, 0706.0542.

[95]  D. Christian,et al.  High-Resolution Optical Observations of Extreme-Ultraviolet-selected Active Late-Type Stars , 2002 .

[96]  G. Herbig.  Radial velocities and spectral types of T Tauri stars. , 1977 .

[97]  R. Jeffries,et al.  The kinematics of lithium-rich, active late-type stars: evidence for a low-mass Local Association , 1995 .

[98]  D. Soderblom,et al.  HD 98800: A Unique Stellar System of Post-T Tauri Stars , 1998 .

[99]  S. Roser,et al.  The initial luminosity and mass functions of the Galactic open clusters , 2008, 0806.2217.

[100]  M. Imbert.  Vitesses radiales photoélectriques de binaires à éclipses - VI. Orbites spectroscopiques et éléments physiques de 12 étoiles doubles Photoelectric radial velocities of eclipsing binaries VI. Orbital and physical elements of 12 double stars , 2002 .

[101]  R. Hoogerwerf.  OB association members in the ACT and TRC catalogues , 2000 .

[102]  F. Allard,et al.  The NextGen Model Atmosphere Grid for 3000 ≤ Teff ≤ 10,000 K , 1998, astro-ph/9807286.

[103]  O. Eggen.  Star Streams and Galactic Structure , 1996 .

[104]  C. Prosser,et al.  Membership of Low-Mass Stars in the Open Cluster (Alpha) Persei , 1992 .

[105]  David R. Soderblom,et al.  Calculating Galactic Space Velocities and Their Uncertainties, with an Application to the Ursa Major Group , 1987 .

[106]  Z. Balog,et al.  PRE-MAIN-SEQUENCE STARS IN THE CEPHEUS FLARE REGION , 2009, 0910.1894.

[107]  Sallie L. Baliunas,et al.  A Survey of CA II H and K Chromospheric Emission in Southern Solar-Type Stars , 1996 .

[108]  E. Covino,et al.  Further identification of ROSAT all-sky survey sources in Orion , 2003 .

[109]  Brian D. Mason,et al.  The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog , 2001 .

[110]  N. Drake,et al.  Lithium Enrichment-Mass-Loss Connection in K Giant Stars , 1996 .

[111]  W. Voges,et al.  Identification of a complete sample of northern ROSAT All-Sky Survey X-ray sources. V. Discovery of a z=4.28 QSO near the RASS source RX J1028.6-0844. , 1997 .

[112]  J. Hearnshaw,et al.  Precise Stellar Radial Velocities , 1998 .

[113]  F. Fekel.  ROTATIONAL VELOCITIES OF LATE-TYPE STARS , 1997 .

[114]  R. Reza,et al.  A search for T-Tauri stars based on the IRAS Point Source Catalog , 1992 .

[115]  K. Biazzo,et al.  Photospheric and chromospheric activity on the young solar-type star HD 171488 (V889 Herculis) , 2010, 1005.0564.

[116]  Jin-zeng Li.  The Status of ROSAT X-ray Active Young Stars toward Taurus-Auriga , 2004 .

[117]  D. Montes,et al.  Late-type members of young stellar kinematic groups – I. Single stars , 2001, astro-ph/0106537.

[118]  Caltech,et al.  Very Low Mass Stars and Brown Dwarfs in Taurus-Auriga , 2002, astro-ph/0209164.

[119]  C. Motch,et al.  The stellar content of medium and high sensitivity X‐ray surveys , 2003 .

[120]  C. Soubiran,et al.  On-line determination of stellar atmospheric parameters T e , logg, (Fe/H) from ELODIE echelle spectra , 1998 .