2000AJ....120..479A

Query : 2000AJ....120..479A

2000AJ....120..479A - Astron. J., 120, 479-487 (2000/July-0)

A survey for low-mass stars and brown dwarfs in the Upper Scorpius OB association.

ARDILA D., MARTIN E. and BASRI G.

Abstract (from CDS):

The Upper Scorpius association is the OB association nearest to the Sun (145 pc). Its young age (∼5 Myr) makes it an ideal place to search for low-mass stars and brown dwarfs, as these objects should be relatively bright. We have performed a photometric search for the low-mass members of the association, using the R, I, and Z filters. The completeness limit is I∼18.5, and the saturation limit is I∼13. We obtain 138 candidate members, covering nearly the entire M spectral type range. We find an excess of brown dwarf candidates over the number predicted by a Miller-Scalo initial mass function. In addition, we have performed infrared imaging and low-resolution optical spectroscopy of selected candidates. We find that the infrared observations confirm the spectral types obtained with the optical photometry. Furthermore, we find Hα in emission in 20 of the 22 objects observed spectroscopically. As Hα is an indicator of youth, we believe that these 20 objects may belong to the association. One of them, UScoCTIO 128, has a very strong and constant Hα line (equivalent width -130 Å), and its position in the color-magnitude diagram suggests that it is a brown dwarf with mass 0.02 M☉. Confirmation of this and the other candidates will have to wait for higher resolution observations that can reveal spectroscopic mass indicators such as Li I and gravity indicators such as K I and the subordinate lines of Na I.

Abstract Copyright: ∼

Journal keyword(s): open clusters and associations: individual (Scorpius-Centaurus) - Stars: Low-Mass, Brown Dwarfs

VizieR on-line data: <Available at CDS (J/AJ/120/479): table2.dat table3.dat>

Nomenclature: Table 2: UScoCTIO NNN (Nos 1-138).

Simbad objects: 143

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Number of rows : 143
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026 		#notes
1 Cl Melotte 20 MGr 03 26 50.6 +48 51 48           ~ 928 0
2 V* V2729 Ori Or* 05 38 25.57752 -02 48 37.0224   21.09 24.40 22.07 19.54 M8.5V 31 0
3 NAME sig Ori Cluster OpC 05 38 42 -02 36.0           ~ 623 0
4 NAME Lower Centaurus Crux As* 12 19 -57.1           ~ 565 1
5 NAME Upper Centaurus Lupus MGr 15 24 -41.9           ~ 567 1
6 UScoCTIO 14 err 15 39 56.45 -18 29 10.4           ~ 1 1
7 UScoCTIO 61 * 15 41 39.7235341848 -18 37 15.136823928           ~ 1 0
8 UScoCTIO 51 PM* 15 42 11.2599791616 -18 29 13.626071916           ~ 3 0
9 UScoCTIO 18 PM* 15 44 05.1786047424 -17 49 49.977504408           M4 3 0
10 UScoCTIO 121 PM* 15 51 47.3239483680 -26 23 47.850983952           M6e 10 0
11 UScoCTIO 116 * 15 52 22.5576936432 -23 13 36.280577100           M6 9 0
12 UScoCTIO 78 PM* 15 52 27.6187421496 -23 02 38.076729000           ~ 1 0
13 UScoCTIO 88 Y*? 15 52 29.3441816880 -23 52 10.542818676           ~ 6 0
14 UScoCTIO 114 PM* 15 52 32.6902235184 -23 53 57.091788960           ~ 6 0
15 LP 860-40 PM* 15 52 35.1569281800 -22 39 09.652115880           ~ 6 0
16 UScoCTIO 65 PM* 15 52 39.7489265256 -25 42 28.791377640           ~ 1 0
17 UScoCTIO 96 * 15 52 48.5760525888 -26 21 45.374912496           M6.0 11 0
18 UScoCTIO 42 Y*? 15 52 55.4532662496 -26 04 44.639308812           ~ 4 0
19 UScoCTIO 22 Y*? 15 53 06.6303445056 -26 06 32.918467752           ~ 8 0
20 UScoCTIO 10 * 15 53 13.1207653512 -26 32 59.940772368       16.03   ~ 1 0
21 UScoCTIO 2 * 15 53 18.8566526328 -23 06 41.219932896           ~ 1 0
22 LP 860-46 PM* 15 53 57.0927077485 -23 11 53.322193519           M5.5Ve 16 0
23 UScoCTIO 46 Or* 15 54 02.3988345672 -22 54 58.761967068           M4.5 13 0
24 UScoCTIO 85 PM* 15 54 03.3785966448 -23 12 33.292225044           M6e 11 0
25 UScoCTIO 133 Or* 15 54 30.6478018584 -25 36 05.565020076           M6 11 0
26 UScoCTIO 63 Or* 15 54 32.4873188736 -26 29 33.308503944           M4e 11 0
27 UScoCTIO 71 Y*O 15 54 42.6105159768 -26 26 27.000904416           M4.75 8 0
28 UScoCTIO 68 LM* 15 55 30.6018710232 -23 45 21.280190472           M4.75 9 0
29 UScoCTIO 92 Or* 15 56 00.5777112648 -23 28 10.545973608           M5.25 7 0
30 UScoCTIO 113 LM* 15 56 01.0406921856 -23 38 08.143283832           M6.5 35 0
31 UScoCTIO 137 PM* 15 56 47.9905426128 -23 47 42.533623104           M7V 8 0
32 UScoCTIO 104 Or* 15 57 12.7940996520 -23 43 46.491309768           M5e 33 0
33 UScoCTIO 13 Or* 15 57 29.8458656448 -22 58 44.104383876           M4e 42 0
34 UScoCTIO 101 Or* 15 57 51.9413233368 -20 12 33.958122120           M5e 16 0
35 UScoCTIO 135 PM* 15 57 52.0796313408 -19 56 35.513321208           d/sdM7 5 0
36 UScoCTIO 28 Y*O 15 57 53.8653968160 -23 17 53.247373332           M4.5 15 0
37 UScoCTIO 107 LM* 15 57 56.0316194736 -20 35 10.465358244           M5.25 14 0
38 UScoCTIO 39 Or* 15 58 15.7077865416 -20 21 36.971380620           M5.0e 15 0
39 UScoCTIO 30 Y*O 15 58 21.0547720584 -20 05 13.574871888           M4.25 15 0
40 UScoCTIO 106 Or* 15 58 26.2716512568 -24 01 13.172473272           M5.25 10 0
41 RX J155829.5-231026 TT* 15 58 29.8128891888 -23 10 07.752769680           M3e 64 0
42 UScoCTIO 80 Or* 15 58 35.9851884168 -23 48 13.822228764   19.8   17.3 15.07 M4e 24 0
43 UScoCTIO 21 Or* 15 58 36.2013568320 -19 46 13.518871356           M4.0e 23 0
44 UScoCTIO 58 LM* 15 58 39.8937206856 -23 07 10.698476700           M5 16 0
45 UScoCTIO 129 * 15 58 56.2770114696 -23 03 35.222425884           ~ 1 0
46 UScoCTIO 128 TT* 15 59 11.3536574304 -23 38 00.356589060           M7e 57 0
47 UScoCTIO 120 * 15 59 17.6425847640 -23 14 48.572250000           ~ 1 0
48 UScoCTIO 62 Y*O 15 59 17.8472380728 -23 43 05.805298560           M6 16 0
49 UScoCTIO 67 LM* 15 59 25.9158944712 -23 05 08.246477796           M6e 40 0
50 UScoCTIO 90 Or* 15 59 30.2082258648 -22 51 26.455643928           M4e 13 0
51 UScoCTIO 97 Y*O 15 59 31.4888583048 -23 31 57.417970944           M5.5 14 0
52 UScoCTIO 64 * 15 59 35.9001690240 -23 23 41.013553128           ~ 1 0
53 UScoCTIO 132 PM* 15 59 37.7665915874 -22 54 13.841712334           M7 19 0
54 UScoCTIO 130 Or* 15 59 43.6603037232 -20 14 39.676605324           M6.5 32 0
55 UScoCTIO 25 Or* 15 59 44.2631452512 -20 29 23.359209324           M5.0e 23 0
56 UScoCTIO 79 Or* 15 59 49.6983346608 -23 01 57.653751756           M5.5 14 0
57 UScoCTIO 5 Or* 15 59 50.5086047328 -19 44 37.368190320           M4e 54 0
58 UScoCTIO 111 PM* 15 59 57.0547833816 -24 11 38.387411196           ~ 3 0
59 UScoCTIO 91 * 15 59 57.9164043192 -24 38 14.780388732           M4.5 8 0
60 UScoCTIO 89 Y*? 15 59 58.9878909960 -24 38 15.319707720           ~ 7 0
61 UScoCTIO 6 Or* 16 00 07.0484271936 -23 40 48.738812376           M5.5e 17 0
62 UScoCTIO 118 PM* 16 00 14.0235976608 -23 27 14.655290904           ~ 1 0
63 UScoCTIO 119 Y*O 16 00 17.6597431224 -22 56 53.747885940           M6.75 8 0
64 UScoCTIO 131 LM* 16 00 19.4431273104 -22 56 28.902592752           M8 26 0
65 UScoCTIO 53 LM* 16 00 26.3114649936 -22 59 41.272528272           M5e 35 0
66 UScoCTIO 112 TT* 16 00 26.7024470616 -20 56 31.619155452           M5.5e 43 0
67 UScoCTIO 73 Or* 16 00 29.4624555216 -20 22 53.717843748           M5 21 0
68 UScoCTIO 75 LM* 16 00 30.2338702560 -23 34 45.615101448           M6e 46 0
69 UScoCTIO 29 Ro* 16 00 32.4237192648 -25 00 24.575336784           M4.5V 11 0
70 UScoCTIO 11 Or* 16 00 35.9870326584 -20 11 55.397222412   17.58 16.30 16.25   M4.5 9 0
71 UScoCTIO 52 Or* 16 00 43.0971415920 -24 30 50.438463696           M4.5e 18 0
72 UScoCTIO 103 Or* 16 00 44.6207478744 -24 50 34.145106540           M5 13 0
73 UScoCTIO 44 PM* 16 00 48.2205038808 -23 21 24.449491764           ~ 6 0
74 UScoCTIO 57 PM* 16 00 51.8002106136 -23 51 22.423822704           ~ 1 0
75 UScoCTIO 138 PM* 16 00 52.3669567200 -20 02 20.509081656           ~ 2 0
76 UScoCTIO 36 * 16 01 01.3367876112 -20 58 01.602239340           ~ 6 0
77 UScoCTIO 32 PM* 16 01 02.4736853688 -20 36 17.509742064       15.90   ~ 5 0
78 UScoCTIO 82 PM* 16 01 07.0104756864 -20 59 18.786362532           ~ 4 0
79 UScoCTIO 19 Or* 16 01 13.9717017672 -25 16 28.687475784   17.64 15.96 15.88 12.95 M4.0e 19 0
80 UScoCTIO 109 ** 16 01 19.1516628312 -23 06 39.452356836           M6e 31 0
81 UScoCTIO 27 Or* 16 01 22.6851753240 -24 08 00.436015968       15.41   M2.25 15 0
82 UScoCTIO 40 PM* 16 01 23.7301505328 -24 19 48.551836620           M5V 10 0
83 UScoCTIO 20 Or* 16 01 26.5313815608 -23 01 34.400866260           M4.5 20 0
84 UScoCTIO 7 Y*O 16 01 29.029776 -25 09 07.03116   16.69 15.55 15.27   M3.5e 18 0
85 UScoCTIO 8 Or* 16 01 30.4192154400 -24 21 31.824650664           M3.5 12 0
86 UScoCTIO 24 Or* 16 01 35.2913336976 -24 43 36.657974496           M3.75 17 0
87 UScoCTIO 99 PM* 16 01 35.5322693016 -23 15 56.220676524           M5e 4 0
88 UScoCTIO 56 Or* 16 01 40.9806829416 -20 22 08.092891236           M5e 26 0
89 UScoCTIO 66 Or* 16 01 49.5549435552 -23 51 08.269103016           M6e 40 0
90 UScoCTIO 81 Y*O 16 01 54.8157463104 -23 36 08.930009772           M5.75 8 0
91 UScoCTIO 26 * 16 01 57.6147958920 -22 50 22.777633104           ~ 2 0
92 UScoCTIO 122 PM* 16 02 02.2727719536 -20 32 37.095818532           ~ 4 0
93 UScoCTIO 100 TT* 16 02 04.3054007904 -20 50 42.580429908         15.156 M7e 51 0
94 UScoCTIO 12 TT* 16 02 05.1771315432 -23 31 06.987210852           M4.5V 26 0
95 UScoCTIO 98 LM* 16 02 06.8342275464 -25 12 38.575609920           ~ 13 0
96 UScoCTIO 60 LM* 16 02 09.5572722720 -23 02 27.912937236           M4e 20 0
97 UScoCTIO 70 Or* 16 02 10.9529499936 -20 07 49.573784208           M5e 33 0
98 UScoCTIO 54 LM* 16 02 12.8082843840 -23 21 20.266370424           ~ 15 0
99 UScoCTIO 74 Or* 16 02 14.8945795776 -24 38 32.610398136           M5.5e 15 0
100 UScoCTIO 15 Or* 16 02 23.5706537424 -22 59 33.310845096           M6.0e 20 0
101 UScoCTIO 47 LM* 16 02 25.9822730184 -22 24 57.488822136           M4.5 18 0
102 UScoCTIO 86 Or* 16 02 41.4307454088 -22 48 41.937018120           M5.5 23 0
103 UScoCTIO 45 Or* 16 02 45.7548007296 -23 04 50.974528080           M5.5e 44 0
104 UScoCTIO 37 Or* 16 02 54.3172873128 -18 05 30.150693528           M5 13 0
105 UScoCTIO 16 * 16 02 56.6129533488 -22 56 24.732206268           M4-4.5 7 0
106 UScoCTIO 77 Y*? 16 02 57.4311813240 -24 42 41.651841096           ~ 14 0
107 UScoCTIO 125 * 16 02 57.9295655640 -24 23 39.159444624           M5.5 8 0
108 UScoCTIO 59 Or* 16 03 01.6136288544 -22 07 52.472918208           M4.75 41 0
109 UScoCTIO 124 * 16 03 10.0273102224 -23 28 47.072195508           ~ 1 0
110 UScoCTIO 23 Or* 16 03 22.7810002200 -22 38 20.790740832           M5 20 0
111 UScoCTIO 31 * 16 03 23.5820718864 -24 13 20.122137192           ~ 2 0
112 UScoCTIO 94 Y*? 16 03 34.8437023824 -24 20 24.452861244           ~ 5 0
113 UScoCTIO 87 PM* 16 03 38.2740625392 -17 09 21.484660500           ~ 2 0
114 UScoCTIO 3 * 16 03 50.0718427656 -18 05 45.926793204           ~ 3 0
115 UScoCTIO 69 Or* 16 03 54.0462446832 -25 09 39.490385472           M5.5e 15 0
116 UScoCTIO 48 Y*? 16 04 10.1267008920 -22 34 45.550086924           ~ 28 0
117 UScoCTIO 93 Y*O 16 04 14.7443995344 -24 24 43.554786588           M4.75 15 0
118 UScoCTIO 9 Y*? 16 04 39.7761677016 -22 47 05.365249980           ~ 9 0
119 UScoCTIO 127 * 16 04 40.2666732720 -22 54 32.320844172           M6 12 0
120 UScoCTIO 95 Y*O 16 04 41.8074487584 -17 41 19.266720108           M5.75 8 0
121 UScoCTIO 83 * 16 04 42.7116298200 -22 54 52.900023204           ~ 1 0
122 UScoCTIO 110 Or* 16 04 43.0361205792 -23 18 25.970702328       19.0 15.9 M6.5 26 0
123 UScoCTIO 123 * 16 04 51.9989535744 -22 24 10.892776248           M8 14 0
124 UScoCTIO 117 LM* 16 04 55.8118905336 -23 07 43.835088432           M6.5 17 0
125 UScoCTIO 136 * 16 05 01.9089519984 -23 21 30.175924176           M8 8 0
126 UScoCTIO 115 * 16 05 15.0719430288 -23 12 15.713043768   17.24 15.66 15.25   ~ 1 0
127 UScoCTIO 105 Y*O 16 05 29.8177354488 -18 07 11.035110936           M6 8 0
128 UScoCTIO 72 Y*O 16 05 40.8175437576 -17 59 22.597859040           M5.75 9 0
129 UScoCTIO 108 LM* 16 05 54.0734809368 -18 18 44.376318180           M7 51 0
130 UScoCTIO 126 PM* 16 06 06.0011560824 -22 39 36.233387640           M5.25--M5 2 0
131 UScoCTIO 41 Y*? 16 06 07.8478097640 -18 03 02.495732508           ~ 6 0
132 UScoCTIO 49 Y*? 16 06 08.7367688088 -18 03 15.596523288           ~ 6 0
133 UScoCTIO 76 LM* 16 06 15.9568510488 -22 18 27.932588028           M4.75 10 0
134 UScoCTIO 84 LM* 16 06 26.3697115896 -23 06 11.399491656           M5.5 20 0
135 UScoCTIO 17 LM* 16 06 34.6123371624 -22 55 04.448597556           M5.0 15 0
136 UScoCTIO 38 LM* 16 06 39.2211590688 -22 48 34.119137484           M5.0 19 0
137 UScoCTIO 134 LM* 16 06 48.1814420832 -22 30 40.025477124           M8.00 20 0
138 UScoCTIO 1 * 16 07 11.3898028296 -17 09 13.019997384           ~ 3 0
139 UScoCTIO 50 LM* 16 07 45.2180922960 -22 22 57.486030528           M5.75 23 0
140 UScoCTIO 43 LM* 16 07 50.3935016856 -22 21 02.183498496           M5.75 25 0
141 NAME Upper Sco Association As* 16 12 -23.4           ~ 1586 1
142 NAME Upper Sco-Cen As* 16 15 -24.2           ~ 1497 1
143 NAME Gould Belt PoG ~ ~           ~ 956 1

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