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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 448066.0, MPI für Astronomie / Publikationen_mpia
Candidate free-floating Super-Jupiters in the young σ Orionis open cluster
Authors:Bihain, G.; Rebolo, R.; Zapatero Osorio, M. R.; Béjar, V. J. S.; Villó-Pérez,, I.; Díaz-Sánchez, A.; Pérez-Garrido, A.; Caballero, J. A.; Bailer-Jones, C. A. L.; Navascués, D. Barrado Y.; Eislöffel, J.; Forveille, T.; Goldman, B.; Henning, T.; Martí­n, E. L.; Mundt, R.
Date of Publication (YYYY-MM-DD):2009
Title of Journal:Astronomy and Astrophysics
Journal Abbrev.:A & A
Start Page:1169
End Page:1182
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:Context: Free-floating substellar candidates with estimated theoretical masses of as low as 5 Jupiter masses have been found in the 3 Myr old <ASTROBJ>sigma Orionis</ASTROBJ> open cluster. As the overlap with the planetary mass domain increases, the question of how these objects form becomes important. The determination of their number density and whether a mass cut-off limit exists is crucial to understanding their formation. Aims: We propose to search for objects of yet lower masses in the cluster and determine the shape of the mass function at low mass. Methods: Using new- and (re-analysed) published {IZJHK}_s[3.6]{-}[8.0]-band data of an area of 840 arcmin2, we performed a search for LT-type cluster member candidates in the magnitude range J=19.5-21.5 mag, based on their expected magnitudes and colours. Results: Besides recovering the T type object <ASTROBJ>S Ori 70</ASTROBJ> and two other known objects, we find three new cluster member candidates, S Ori 72-74, with J≈21 mag and within 12 arcmin of the cluster centre. They have theoretical masses of 4{-2}+3 M_Jup and are among the least massive free-floating objects detected by direct imaging outside the Solar System. The photometry in archival Spitzer [3.6]-[5.8]-band images infers that <ASTROBJ>S Ori 72</ASTROBJ> is an L/T transition candidate and <ASTROBJ>S Ori 73</ASTROBJ> a T-type candidate, following the expected cluster sequence in the mid-infrared. Finally, the L-type candidate <ASTROBJ>S Ori 74</ASTROBJ> with lower quality photometry is located at 11.8 arcsec ( 4250 AU) of a stellar member of sigma Orionis and could be a companion. After contaminant correction in the area complete to J=21.1 mag, we estimate that there remain between zero and two cluster members in the mass interval 6-4 M_Jup. Conclusions: We present S Ori 73, a new candidate T type and candidate sigma Orionis member of a few Jupiter masses. Our result suggests a possible turnover in the substellar mass spectrum below 6 Jupiter masses, which could be investigated further by wider and deeper photometric surveys.
Free Keywords:stars: luminosity function; mass function; Galaxy: open clusters and associations: individual: sigma Orionis; stars: low-mass; brown dwarfs
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:URL:http://adsabs.harvard.edu/abs/2009A%26A...506.1169... [ID No:1]
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