A deep look into the core of young clusters* II. λ-Orionis

Context. Over the past years, theλ−Orionis cluster has been a prime location for the study of young very low mass stars, substellar and isolated planetary mass objects and the determination of the initial mass function and other properties of low mass cluster members. Aims. In the continuity of our previous studies of young associati ons cores, we search for ultracool members and new multiple systems within the central 5. ′ 3 (≈0.6 pc) of the cluster. Methods. We obtained deep seeing limited J, Ks-band images of the 5. 3 central part of the cluster with NTT/SofI and H-band images with CAHA/Omega2000. These images were complemented by multi-conjugate adaptive optics (MCAO) H and Ks images of the 1. 5 central region of theλ−Orionis cluster obtained with the prototype MCAO facility MAD at the VLT. The direct vicinity of the massiveλ−Ori O8III-star was probed using NACO/SDI at the VLT. Finally, we also retrieved Spitzer IRAC images of the same area and used archival Subaru Suprime-Cam and CFHT CFHT12Ki-band images. Results. We report the detection of 9 new member candidates selected from optical and near-IR color-color and color-magnitude diagrams and 7 previously known members. The high spatial resolution images resolve 3 new visual multiple systems. Two of them are most likely not members of the association. The third one is made of a brown dwarf candidate companion to the F8V star HD 36861C. The simultaneous differential images allow us to rule out the presence of visual companions more massive than M>0.07 M⊙ in the range 1‐2.5 ′′ , and M>0.25 M⊙ in the range 0. ′′ 5‐2.5 ′′ .

[1]  William N. Venables,et al.  Modern Applied Statistics with S , 2010 .

[2]  M. Bate.  The importance of radiative feedback for the stellar initial mass function , 2008, 0811.1035.

[3]  Matthew Bate,et al.  Stellar, brown dwarf and multiple star properties from hydrodynamical simulations of star cluster formation , 2008, 0811.0163.

[4]  J. A. Caballero,et al.  Contamination by field late-M, L, and T dwarfs in deep surveys , 2008, 0805.4480.

[5]  S. Randich,et al.  FLAMES spectroscopy of low-mass stars in the young clusters σ Ori and λ Ori , , 2008, 0805.2914.

[6]  S. Serjeant,et al.  Properties of dusty tori in active galactic nuclei – I. The case of SWIRE/SDSS quasars , 2008, 0802.2458.

[7]  T. Naylor,et al.  Fitting the young main-sequence: distances, ages and age spreads , 2008, 0801.4085.

[8]  L. Testi,et al.  Accretion properties of T Tauri stars in σ Orionis , 2008, 0801.2886.

[9]  W. Sherry,et al.  MAIN-SEQUENCE FITTING DISTANCE TO THE σ Ori CLUSTER , 2008, 0801.2585.

[10]  J. Caballero.  Dynamical parallax of σ Ori AB: mass, distance and age , 2007, 0710.3541.

[11]  M. Osorio,et al.  New constraints on the membership of the T dwarf S Ori 70 in the σ Orionis cluster , 2007, 0710.2776.

[12]  Laird M. Close,et al.  An Imaging Survey for Extrasolar Planets around 45 Close, Young Stars with the Simultaneous Differential Imager at the Very Large Telescope and MMT , 2007 .

[13]  J. Caballero.  Spatial distribution of stars and brown dwarfs in σ Orionis , 2007, 0710.1255.

[14]  Michel Mayor,et al.  The impact of stellar duplicity on planet occurrence and properties. I. Observational results of a V , 2007 .

[15]  E. Marchetti,et al.  Multi-Conjugate Adaptive Optics images of the Trapezium Cluster ⋆ , 2007, 0709.3994.

[16]  M. Osorio,et al.  Discs of planetary-mass objects in $\mathsf{\sigma}$ Orionis , 2007 .

[17]  Adam L. Kraus,et al.  Mapping the Shores of the Brown Dwarf Desert. I. Upper Scorpius , 2007, 1509.05217.

[18]  P. Kalas,et al.  In the Spirit of Bernard Lyot: The Direct Detection of Planets and Circumstellar Disks in the 21st Century. , 2007 .

[19]  R. Rebolo,et al.  The substellar mass function in σ Orionis II. Optical, near-infrared and IRAC/Spitzer photometry of young cluster brown dwarfs and planetary-mass objects , , 2007, 0705.0922.

[20]  J. Caballero.  A near-infrared/optical/X-ray survey in the centre of σ Orionis , 2007, 0705.0914.

[21]  D. B. Navascués,et al.  The young, wide and very low mass visual binary Lambda Orionis 167 , 2007, 0704.2469.

[22]  L. Hartmann,et al.  Spitzer: Accretion in Low-Mass Stars and Brown Dwarfs in the λ Orionis Cluster , 2007, 0704.1963.

[23]  J. Spyromilio,et al.  The European Extremely Large Telescope (E-ELT) , 2007 .

[24]  Etienne Artigau,et al.  A New Algorithm for Point-Spread Function Subtraction in High-Contrast Imaging: A Demonstration with Angular Differential Imaging , 2007, astro-ph/0702697.

[25]  E. Young,et al.  A Spitzer Space Telescope Study of Disks in the Young σ Orionis Cluster , 2007, astro-ph/0701476.

[26]  A.G.A. Brown,et al.  A brown dwarf desert for intermediate mass stars in Scorpius OB2 , 2006, astro-ph/0611903.

[27]  M. Osorio,et al.  A search for substellar members in the Praesepe and $\mathsf{\sigma}$ Orionis clusters , 2006, astro-ph/0609283.

[28]  James Liebert,et al.  Spitzer IRAC Photometry of M, L, and T Dwarfs , 2006, astro-ph/0606432.

[29]  Norbert Hubin,et al.  MAD star oriented: laboratory results for ground layer and multi-conjugate adaptive optics , 2006, SPIE Astronomical Telescopes + Instrumentation.

[30]  U. Exeter,et al.  Kinematic structure in the young σ Orionis association , 2006, astro-ph/0605616.

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

[32]  J. Caballero.  Ultra low-mass star and substellar formation in σ Orionis , 2005, astro-ph/0511166.

[33]  Chile.,et al.  Variability in the Lambda Orionis cluster substellar domain , 2005, astro-ph/0510402.

[34]  Italy.,et al.  XMM-Newton observations of the σ Orionis cluster: II. Spatial and spectral analysis of the full EPIC field , 2005, astro-ph/0510209.

[35]  M. Osorio,et al.  S Ori J053825.4 024241: A Classical T Tauri-like object at the substellar boundary , 2005, astro-ph/0509613.

[36]  E. Grebel,et al.  Empirical color transformations between SDSS photometry and Other photometric systems. , 2005, astro-ph/0609121.

[37]  W. Sherry,et al.  Photometric Identification of the Low-Mass Population of Orion OB1b. I. The σ Orionis Cluster , 2004, astro-ph/0410244.

[38]  H. Zinnecker,et al.  The primordial binary population. I. A near-infrared adaptive optics search for close visual companions to A star members of Scorpius OB2 , 2004, astro-ph/0410106.

[39]  J. Oliveira,et al.  Membership, binarity and accretion among very low-mass stars and brown dwarfs of the σ Orionis cluster , 2004, astro-ph/0409749.

[40]  R. Rebolo,et al.  The Substellar Population in the Young σ Orionis Cluster, Spatial Distribution , 2004 .

[41]  J. Sanz-Forcada,et al.  XMM-Newton observations of the σ Ori cluster - I. The complex RGS spectrum of the hot star σ Ori AB , 2004, astro-ph/0404078.

[42]  R. Jayawardhana,et al.  The Substellar Population of the Young Cluster λ Orionis , 2004, astro-ph/0404072.

[43]  J. Eisloeffel,et al.  Rotation and accretion of very low mass objects in the sigma Ori cluster , 2004, astro-ph/0404014.

[44]  J. Schmitt,et al.  Discovery of X-ray flaring on the magnetic Bp-star σ Ori E , 2004, astro-ph/0402437.

[45]  A. Robin,et al.  A synthetic view on structure and evolution of the Milky Way , 2003, astro-ph/0401052.

[46]  Usa,et al.  An Empirical Criterion to Classify T Tauri Stars and Substellar Analogs Using Low-Resolution Optical Spectroscopy , 2003, astro-ph/0309284.

[47]  M. Osorio,et al.  Spectroscopic Estimate of Surface Gravity for a Planetary Member in the σ Orionis Cluster , 2003, astro-ph/0307268.

[48]  M. Osorio,et al.  The sigma Orionis substellar population. VLT/FORS spectroscopy and 2MASS photometry , 2003 .

[49]  L. Hillenbrand,et al.  Accretion in Young Stellar/Substellar Objects , 2003, astro-ph/0304078.

[50]  F. Allard,et al.  Evolutionary models for cool brown dwarfs and extrasolar giant planets. The case of HD 209458 , 2003, astro-ph/0302293.

[51]  S. Okamura,et al.  Subaru Prime Focus Camera — Suprime-Cam , 2002, astro-ph/0211006.

[52]  R. Rebolo,et al.  A Methane, Isolated, Planetary-Mass Object in Orion , 2002, astro-ph/0206353.

[53]  R. Mathieu,et al.  A Photometric Study of the Young Stellar Population throughout the λ Orionis Star-forming Region , 2001, astro-ph/0110160.

[54]  Pasadena,et al.  Optical spectroscopy of isolated planetary mass objects in the σ Orionis cluster , 2001, astro-ph/0108249.

[55]  R. Rebolo,et al.  Keck NIRC Observations of Planetary-Mass Candidate Members in the σ Orionis Open Cluster , 2001, astro-ph/0108066.

[56]  M. Osorio,et al.  The Substellar Mass Function in σ Orionis , 2001, astro-ph/0104097.

[57]  R. Mathieu,et al.  The Spatial Distribution of the λ Orionis Pre-Main-Sequence Population , 2001 .

[58]  Coryn A. L. Bailer-Jones,et al.  Discovery of Young, Isolated Planetary Mass Objects in the σ Orionis Star Cluster , 2000 .

[59]  F. Allard,et al.  Evolutionary Models for Very Low-Mass Stars and Brown Dwarfs with Dusty Atmospheres , 2000, astro-ph/0005557.

[60]  Emiliano Diolaiti,et al.  StarFinder: an IDL GUI-based code to analyze crowded fields with isoplanatic correcting PSF fitting , 2000, Astronomical Telescopes and Instrumentation.

[61]  F. Ochsenbein,et al.  The VizieR database of astronomical catalogues , 2000, astro-ph/0002122.

[62]  R. Mathieu,et al.  A WIYN Lithium Survey for Young Stars in the λ Orionis Star-forming Region , 1999 .

[63]  M. Osorio,et al.  A Search for Very Low Mass Stars and Brown Dwarfs in the Young σ Orionis Cluster , 1999, astro-ph/9903217.

[64]  S. E. Persson,et al.  A New System of Faint Near-Infrared Standard Stars , 1998 .

[65]  Jean Gabriel Cuby,et al.  SOFI sees first light at the NTT. , 1998 .

[66]  C. O’Dell,et al.  Hubble Space Telescope Mapping of the Orion Nebula. I. A Survey of Stars and Compact Objects , 1996 .

[67]  Molefe Mokoene,et al.  The Messenger , 1995, Outrageous Fortune.

[68]  Blair D. Savage,et al.  An IUE Survey of Interstellar H I LY alpha Absorption , 1994 .

[69]  S. Drake.  Radio-continuum observations of a small sample of hot stars , 1990 .

[70]  N. Walborn,et al.  Sigma Orionis E as a mass-transfer binary system , 1976, Nature.

[71]  N. Walborn.  A new phenomenon in the spectrum-of sigma Orionis E , 1974 .

[72]  W. S. Adams,et al.  Eight stars whose radial velocities vary. , 1903 .

[73]  M. Langlois,et al.  Society of Photo-Optical Instrumentation Engineers , 2005 .

[74]  S. W. Burnham.  Double Star Observations made at the Lick Observatory in 1892 , 2022 .

[75]  F. G. W. Struve.  Stellarum duplicium et multiplicium mensurae micrometricae per magnum Fraunhoferi tubum annis a 1824 ad 1837 in specula Dorpatensi institutae auctore , 1837 .