1999ApJ...521..671B


Query : 1999ApJ...521..671B

1999ApJ...521..671B - Astrophys. J., 521, 671-681 (1999/August-3)

A search for very low mass stars and brown dwarfs in the young σ Orionis cluster.

BEJAR V.J.S., ZAPATERO OSORIO M.R. and REBOLO R.

Abstract (from CDS):

We present a CCD-based photometric survey covering 870 arcmin2 in a young stellar cluster around the young multiple star σ Orionis. Our survey-limiting R, I, and Z magnitudes are 23.2, 21.8, and 21.0, respectively, the completeness being about 2.2 mag brighter. From our color-magnitude diagrams, we have selected 49 faint objects (I=15-21 mag), which smoothly extrapolate the photometric sequence defined by more massive known members. Adopting the currently accepted age interval of 2-10 Myr for the Orion 1b association, in which σ Orionis is located, and considering recent evolutionary models, our objects may span a mass range from 0.1 down to 0.02 M, well within the substellar regime. Follow-up low-resolution optical spectroscopy (635-920 nm) for eight of our candidates in the magnitude range I=16-19.5 shows that they have spectral types M6-M8.5, consistent with what is expected for true members. Compared with their Pleiades counterparts of similar types, Hα emission is generally stronger, while Na I and K I absorption lines appear weaker, as expected for lower surface gravities and younger ages. In addition, TiO and in particular VO bands appear to be clearly enhanced in our candidate with the latest spectral type, S Ori 45 (M8.5, I=19.5), compared to objects of similar types in older clusters and the field. We have estimated the mass of this candidate at only 0.020-0.040 M; hence, it is one of the least massive brown dwarfs yet discovered. We examine the potential role of deuterium as a tracer of both substellar nature and age in very young clusters. The luminosity and mass at which the burning/preservation of deuterium takes place is a sensitive function of age and can therefore provide a determination of the age of a cluster. The σ Orionis cluster is an excellent site for determining this transition zone empirically; the most massive brown dwarfs identified are expected to have burned their deuterium content, while the lowest mass ones should have preserved it.

Abstract Copyright:

Journal keyword(s): Galaxy: Open Clusters and Associations: Individual: Name: σ Orionis - Stars: Evolution - Stars: Fundamental Parameters - Stars: Low-Mass, Brown Dwarfs - Stars: Pre-Main-Sequence

Nomenclature: Tables 2, 3: [BZR99] S Ori NN (Nos 1-49).

Simbad objects: 55

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Number of rows : 55
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 Cl* Melotte 22 ROQUE 4 LM* 03 43 53.53224 +24 31 11.5140         20.25 M9.0 19 0
2 Cl Melotte 22 OpC 03 46 24 +24 06.8           ~ 3196 0
3 Cl* Melotte 22 TEIDE 1 LM* 03 47 17.9147300712 +24 22 31.746313740         19.26 M8.0 104 0
4 [BZR99] S Ori 46 * 05 36 51.7 -02 32 54           M8.5 4 0
5 [BZR99] S Ori 33 * 05 36 58.0796129568 -02 35 19.475262024         17.08 ~ 11 0
6 [BZR99] S Ori 34 * 05 37 07.2192564048 -02 32 44.240012988         17.10 ~ 5 0
7 [BZR99] S Ori 37 * 05 37 07.6144718784 -02 27 14.997346128         17.49 ~ 3 0
8 [BZR99] S Ori 19 * 05 37 21.0603854496 -02 25 40.035311436         16.62 ~ 6 0
9 [BZR99] S Ori 40 Y*O 05 37 36.4816663032 -02 41 56.713683516   23.22   20.12 17.79 M3.5 18 0
10 [BZR99] S Ori 48 * 05 37 39.0 -02 39 50           ~ 2 0
11 [BZR99] S Ori 23 Y*O 05 37 51.1108853952 -02 26 07.501486812   20.6   19.4 16.88 M6.5 14 0
12 [BZR99] S Ori 35 Y*O 05 37 55.5938374392 -02 33 05.343313356 20.472 23.63   19.40 17.55 M4.5 14 0
13 [BZR99] S Ori 24 Y*O 05 37 55.7464490520 -02 24 33.705030096   23.05 20.54 18.89 17.04 M5.0 10 0
14 [BZR99] S Ori 12 Y*O 05 37 57.4587695400 -02 38 44.468902788   20.61 19.81 18.15 16.42 M4.5/6V 25 0
15 [BZR99] S Ori 44 * 05 38 07.126 -02 43 21.05   22.29 23.54 21.54 19.64 M7 7 0
16 [BZR99] S Ori 13 Y*O 05 38 13.2091054320 -02 24 07.556361588   21.07 19.68 18.06 16.13 M5.5 14 0
17 [BZR99] S Ori 43 * 05 38 13.9590316104 -02 35 01.288893300         18.99 ~ 7 0
18 [BZR99] S Ori 47 BD* 05 38 14.62416 -02 40 15.4020         20.53 L1e 28 0
19 V* V2723 Ori Or* 05 38 17.1808248144 -02 22 25.719885012   22.96 19.21 17.61 15.67 M5.0 16 0
20 2MASS J05381741-0240242 BD* 05 38 17.4145740552 -02 40 24.296790180   23.24   19.21 17.09 M5/7V 24 0
21 [BZR99] S Ori 31 Y*O 05 38 20.8792849368 -02 46 13.332049824         17.25 M4.0 23 0
22 [BZR99] S Ori 49 * 05 38 22.9 -02 37 55           M7.5 3 0
23 V* V2729 Ori Or* 05 38 25.57752 -02 48 37.0224   21.09 24.40 22.07 19.54 M8.5 31 0
24 [BZR99] S Ori 18 Y*O 05 38 25.6854086976 -02 31 21.716183784     19.99 18.68 16.59 M3.5 16 0
25 [BZR99] S Ori 29 Or* 05 38 29.6185929264 -02 25 14.270648484   21.05 20.72 19.02 17.02 M4.0 19 0
26 [BZR99] S Ori 39 Y*O 05 38 32.4445347456 -02 29 57.296432760 21.027 22.98   19.77 17.71 M6.5 16 0
27 [BZR99] S Ori 22 Y*O 05 38 35.3557024968 -02 25 22.268716356   22.52 20.73 18.91 16.87 M6e 17 0
28 NAME sigma Orionis Cluster MGr 05 38 42 -02 36.0           ~ 524 0
29 [BZR99] S Ori 6 Y*O 05 38 47.6632499544 -02 30 37.481740308 20.977 20.25   17.30 15.38 ~ 18 0
30 [BZR99] S Ori 15 Y*O 05 38 48.0991320696 -02 28 53.682649428 21.11 21.32 19.89 18.32 16.42 M5.5e 18 0
31 [BZR99] S Ori 17 Y*O 05 39 04.4949780000 -02 38 35.381301036     20.00 18.92 16.80 M6 16 0
32 [BZR99] S Ori 20 Y*O 05 39 07.5827704608 -02 29 05.658266004   22.49   19.02 17.03 M5.5 16 0
33 2MASS J05390808-0228447 Y*O 05 39 08.086 -02 28 44.77 19.34 19.57 18.69 17.56 15.88 M4.0 16 0
34 [BZR99] S Ori 7 Y*O 05 39 08.2185362880 -02 32 28.467592548 20.85 20.61 19.10 17.55 15.70 ~ 16 0
35 [BZR99] S Ori 25 Or* 05 39 08.9497481544 -02 39 57.986417520     21.09 19.34 17.02 M6.5V 23 0
36 2MASS J05391183-0227409 Y*O 05 39 11.8349306400 -02 27 41.009358564 20.843 19.55 18.04 16.81 15.16 ~ 17 0
37 [BZR99] S Ori 30 Y*O 05 39 13.0855893696 -02 37 50.971269108     20.74 19.34 17.30 M6 18 0
38 [BZR99] S Ori 16 Y*O 05 39 15.1041343392 -02 40 47.667633204 20.73 21.97   18.73 16.74 M3.5 14 0
39 [BZR99] S Ori 38 Y*O 05 39 15.2611041000 -02 21 50.711830596   22.96   20.02 17.97 M7 13 0
40 [BZR99] S Ori 26 * 05 39 15.765 -02 38 26.22         17.12 M4.5 7 0
41 2MASS J05392023-0238258 Y*O 05 39 20.2371430800 -02 38 25.948061736 21.41 20.82 18.97 17.45 15.55 M5.5 20 0
42 [BZR99] S Ori 3 LM* 05 39 20.9751873360 -02 30 33.534650772   20.66 19.25 17.58 15.57 ~ 19 0
43 [BZR99] S Ori 28 Y*? 05 39 23.1926611128 -02 46 55.782192540   22.63 21.06 19.41 17.23 M5.5 21 0
44 [BZR99] S Ori 42 Y*? 05 39 23.4322728408 -02 40 57.579062268         19.18 M7.5 10 0
45 2MASS J05392633-0228376 Y*O 05 39 26.3370825408 -02 28 37.711621812   19.69 18.02 16.96 15.26 ~ 15 0
46 [BZR99] S Ori 36 Y*O 05 39 26.8571235120 -02 36 56.236094820   22.73     17.88 ~ 16 0
47 [BZR99] S Ori 21 Y*O 05 39 34.3303193088 -02 38 46.937656932   21.01 21.12 19.27 17.29 ~ 17 0
48 [BZR99] S Ori 14 Y*O 05 39 37.5942690888 -02 44 30.504555420   22.39 20.39 18.69 16.71 ~ 15 0
49 [BZR99] S Ori 41 * 05 39 38.4999621504 -02 31 13.326968064 20.695 21.56   20.61 18.69 ~ 8 0
50 [BZR99] S Ori 4 Y*O 05 39 39.3176659728 -02 32 25.331200404 20.429 20.35 18.78 17.34 15.52 ~ 15 0
51 [BZR99] S Ori 32 Y*? 05 39 43.5829405200 -02 47 31.827482016   21.35   19.75 17.59 M6.0 17 0
52 [BZR99] S Ori 11 Y*O 05 39 44.3302873224 -02 33 02.834542764 21.137 20.75 20.11   16.46 M6 15 0
53 [BZR99] S Ori 10 Y*O 05 39 44.5055544576 -02 24 43.244819676   23.03 19.76   16.36 ~ 16 0
54 HD 42581B BD* 06 10 34.80 -21 52 00.0           T6.5 481 0
55 NAME Ophiuchus Molecular Cloud SFR 16 28 06 -24 32.5           ~ 3361 1

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2022.07.06-00:31:34

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