2008A&A...477..895Z


Query : 2008A&A...477..895Z

2008A&A...477..895Z - Astronomy and Astrophysics, volume 477, 895-900 (2008/1-3)

New constraints on the membership of the T dwarf S Ori 70 in the σ Orionis cluster.

ZAPATERO OSORIO M.R., BEJAR V.J.S., BIHAIN G., MARTIN E.L., REBOLO R., VILLO-PEREZ I., DIAZ-SANCHEZ A., PEREZ GARRIDO A., CABALLERO J.A., HENNING T., MUNDT R., BARRADO Y NAVASCUES D. and BAILER-JONES C.A.L.

Abstract (from CDS):

The nature of SOri 70 (SOri J053810.1-023626), a faint mid-T type object found towards the direction of the young σ Orionis cluster, is still under debate. We intend to find out whether it is a field brown dwarf or a 3-Myr old planetary-mass member of the cluster. We report on near-infrared JHKs and mid-infrared [3.6] and [4.5] IRAC/Spitzer photometry recently obtained for SOri 70. The new near-infrared images (taken 3.82yr after the discovery data) allowed us to derive the first proper motion measurement for this object. The colors (H-Ks), (J-Ks) and Ks-[3.6] appear discrepant when compared to T4-T7 dwarfs in the field. This behavior could be ascribed either to a low-gravity atmosphere or to an atmosphere with a metallicity that is significantly different than solar. The small proper motion of SOri 70 (11.0±5.9mas/yr) indicates that this object is farther away than expected if it were a single field T dwarf lying in the foreground of the σ Orionis cluster. Our measurement is consistent with the proper motion of the cluster within 1.5σ the astrometric uncertainty. Taking into account both SOri 70's proper motion and the new near- and mid-infrared colors, a low-gravity atmosphere remains as the most likely explanation for our observations. This supports SOri 70's membership in σ Orionis, with an estimated mass in the interval 2-7MJup, in agreement with our previous derivation.

Abstract Copyright:

Journal keyword(s): stars: low mass, brown dwarfs - stars: pre-main-sequence - open clusters and associations: individual: σ Orionis

Simbad objects: 10

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Number of rows : 10
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 2MASS J00501994-3322402 BD* 00 50 19.94352 -33 22 40.2708           T7 34 0
2 NAME Ori I As* 05 38 -02.8           ~ 585 0
3 [BZR99] S Ori 70 BD* 05 38 10.10 -02 36 26.0           T6-7 46 0
4 NAME sigma Orionis Cluster MGr 05 38 42 -02 36.0           ~ 525 0
5 * sig Ori Y*O 05 38 44.7653828520 -02 36 00.283179888 2.54 3.58 3.79 3.87 4.11 O9.5V+B0.2V(n) 775 0
6 2MASS J05591914-1404488 BD* 05 59 19.1872549354 -14 04 49.206913185           T4.5 140 0
7 2MASSI J0937347+293142 BD* 09 37 34.87968 +29 31 40.9908           T6 82 0
8 2MASSW J1047539+212423 BD* 10 47 53.85456 +21 24 23.4684           T6.5 78 0
9 2MASS J12373919+6526148 BD* 12 37 39.19632 +65 26 14.8092           T6.5 67 0
10 2MASS J13243553+6358281 BD* 13 24 35.53752 +63 58 28.1532           L8.0+T3.5 42 0

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2022.08.15-14:30:50

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