1997A&AS..121..223D


C.D.S. - SIMBAD4 rel 1.7 - 2020.02.26CET03:22:25

1997A&AS..121..223D - Astron. Astrophys., Suppl. Ser., 121, 223-242 (1997/February-0)

Pre-main sequence candidates in the very young open cluster NGC 6611.

DE WINTER D., KOULIS C., THE P.S., VAN DEN ANCKER M.E., PEREZ M.R. and BIBO E.A.

Abstract (from CDS):

For the search of Herbig Ae/Be objects in the extremely young open cluster NGC 6611 we have selected a sample of 52 pre-main sequence candidates, discovered by Walker (1961ApJ...133..438W), Sagar & Joshi (1979Ap&SS..66....3S), Chini & Wargau (1990A&A...227..213C) and The et al. (1990A&AS...82..319T). We continue the approach of the last paper by studying each star individually with new and unpublished Walraven WULBV, Johnson/Cousins UBV(RI)C and Johnson JHKLM photometric data as well as low resolution spectroscopy. Each object is shown to have its own extinction law, which is investigated using their spectral energy distribution (SED). There does not seem to be a clear relationship between the location of a star and the extinction law. This means that the extinction is generated locally and its correction must be taken individually. For each object accurate astrophysical parameters are then derived. Plotting the objects in an HR-diagram, together with the values for the E(B-V), the probability of membership value P and the extinction characteristics, helps to discriminate between cluster members and non-cluster members. Most foreground stars are of late spectral type and are labeled as Group III objects. Group I, to which most members of this cluster belong, contains objects of early spectral type. Part of them seem to be in their post-ZAMS phase and the other part in their pre-ZAMS stage. By comparing the evolutionary tracks of Palla & Stahler (1993ApJ...418..414P) for pre-MS objects and of Maeder & Meyenet (1988A&AS...76..411M) for post-MS stars we have concluded that the cluster contains objects of a few 0.1Myr as well as objects of about 6Myr. As most of the Group I objects do not show well-known Herbig Ae/Be characteristics, the time scale of clearing the disk material must be typically less than about 0.1Myr for the more massive objects. Objects that show an IR-excess are found among the less luminous ones. They could still be in their pre-ZAMS phase, having an age of about 1Myr. Such an age is appropriate for the Group II objects, which are of intermediate spectral type. As they are located close to the stellar birthline they should have been formed recently. It seems that an efficient clearing mechanism must have taken place, because not many of these objects are embedded and show only some IR-anomalies. This could be the reason that we have found no more than four typical Herbig Ae/Be candidates. We support the hypothesis of Hillenbrand et al. (1993AJ....106.1906H) that there is an age spread in NGC 6611. The stars with the highest AV values are located in the centre of the cluster, somewhat to the northwest. This coincides with the location of many embedded sources more towards the northwest, a region in which star-formation is probably still taking place. The age of the most evolved objects is about 6Myr. It would be interesting to study these regions and the Group II objects since investigating the youngest objects which are still partly embedded may help us to understand the first phases of star formation and the rapid cleaning of the circumstellar material. Young ``naked'' stars can also be formed by evaporating gaseous globules (EGGs) as was recently discovered in dark regions of this cluster Hester & Scowen (1995). The lack of angular momentum of such objects could explain the paucity of HAeBe candidates.

Abstract Copyright:

Journal keyword(s): circumstellar matter - stars: emission-line - stars: evolution - stars: formation - stars: pre-main sequence - open clusters and associations: individual: NGC 6611

VizieR on-line data: <Available at CDS (J/A+AS/121/223): table1 table2 table3 table4 table6 tables.tex>

Simbad objects: 52

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Number of rows : 52

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 NGC 6611 559 * 18 17 40.4881353033 -13 53 26.061779497   12.19 11.58     G0 6 0
2 BD-13 4912 * 18 17 51.0437750521 -13 50 55.781354730 11.36 11.32 10.01 9.93   B2.5I 18 0
3 NGC 6611 103 * 18 18 22.78 -13 51 30.5 13 12.88 12.49     A0V 11 0
4 NGC 6611 188 * 18 18 33.7215297707 -13 40 58.855809698 14.44 14.604 13.019   10.864 B0V 14 0
5 [HMS93] J181836.06-134513.3 Em* 18 18 35.91 -13 45 13.4   15.2 14.40     A0 12 0
6 Cl* NGC 6611 PPM 25 Em* 18 18 36.7392999676 -13 47 33.071207376 12.32 12.57 12.05     B1Ve 20 0
7 UCAC3 153-230515 Em* 18 18 37.0565721042 -13 45 29.508027702 16.932 15.701 14.043   12.05 B 17 0
8 NGC 6611 232 * 18 18 38.7330997102 -13 48 32.431406430   15.71 14.81     A0? 8 0
9 NGC 6611 240 * 18 18 39.50 -13 49 14.8   13.15 12.60     B 9 0
10 [BNM2013] 21.04 136 Em* 18 18 40.0882611300 -13 47 00.854379079 15.334 14.431 13.512   12.225 A0 18 0
11 [HMS93] J181841.60-134840.6 Em* 18 18 41.55 -13 48 39.9 14.55 14.39 13.58     Ae 13 0
12 [RMB2008] G016.9693+00.8311 Em* 18 18 41.5799644201 -13 46 30.924832113 16.711 15.701 14.267   12.510 G 15 0
13 Cl* NGC 6611 PPM 47 Em* 18 18 41.6930813926 -13 46 43.855057430 13.43 13.63 13.07     B3V 14 0
14 Cl* NGC 6611 BKP 29675 Em* 18 18 42.250 -13 47 30.43 15.731 14.915 14.113   13.065 A0 15 0
15 [BNM2013] 21.04 124 * 18 18 42.4816568144 -13 48 47.037942769   14.39 13.58   12.744 B 12 0
16 Cl* NGC 6611 PPM 65 Em* 18 18 44.5245946435 -13 45 48.121858979 13.34 13.55 12.85     B1.5:V 23 0
17 NGC 6611 290 * 18 18 44.8426904562 -13 56 22.342076400 12.24 12.46 11.69     B2.5V 13 0
18 Cl* NGC 6611 PPM 69 Em* 18 18 45.0318300168 -13 45 41.023824157 13.23 13.35 12.72     B1.5Ve 23 0
19 Cl* NGC 6611 PPM 20 Em* 18 18 45.038 -13 47 47.17 13.642 13.276 12.607   11.787 B1.5Ve 21 0
20 NGC 6611 299 Ae* 18 18 45.0878297242 -13 49 19.483387535 16.068 15.211 14.313   13.359 A3/5 16 0
21 NGC 6611 313 * 18 18 46.1329444513 -13 49 23.438747806   12.11 11.60     B5III 20 0
22 M 16 OpC 18 18 48 -13 48.4   6.58 6.0     ~ 926 2
23 [BNM2013] 20.04 155 Em* 18 18 49.1681453055 -13 48 04.229176695 14.243 13.802 13.288   12.419 B5III 20 0
24 NGC 6611 339 Em* 18 18 49.21 -13 46 53.9   14.64 13.75     ~ 10 0
25 NGC 6611 349 * 18 18 50.5732420732 -13 47 33.952339826   13.01 11.61     G5III 16 0
26 [HMS93] J181855.01-134846.1 Em* 18 18 55.01 -13 48 46.1   14.28 13.70     B 13 0
27 [BNM2013] 21.04 85 Em* 18 18 55.5848817006 -13 48 44.550600429 16.369 15.305 13.965   12.326 G8 14 0
28 [BNM2013] 21.04 84 Em* 18 18 55.8332914513 -13 46 54.059887172 14.248 13.493 12.789   11.770 B9III 21 0
29 2MASS J18185599-1344462 Y*? 18 18 55.9919884427 -13 44 46.369609989 15.858 13.525 11.632   9.857 ~ 12 0
30 TYC 5689-515-1 * 18 18 56.0607372784 -13 46 25.710124514   12.39 11.16     K0II 15 0
31 NGC 6611 411 * 18 18 56.97 -13 44 06.5   13.79 12.18     K0V 14 0
32 NGC 6611 440 * 18 19 00.5300571367 -13 46 35.000592056   13.63 12.27     K0V 11 0
33 Cl* NGC 6611 ESL 49 Em* 18 19 02.8904669390 -13 47 17.652632778   12.65 12.05     A5II 16 0
34 BD-13 4933 Be* 18 19 04.8785156526 -13 48 20.447211729 11.259 11.095 10.628   9.915 B0.5Vn 40 0
35 NGC 6611 599 * 18 19 06.4627154138 -13 57 45.934307792   11.5 10.2     G8III 11 0
36 BD-13 4935 * 18 19 06.5055889794 -13 43 30.475077048 11.918 11.53 11.27   10.270 B3V 21 0
37 [HMS93] J181906.96-134504.5 Em* 18 19 06.91 -13 45 04.4   12.88 12.36     B8III 14 0
38 NGC 6611 489 * 18 19 07.3229959386 -13 43 04.724423484   11.66 11.42     B8III 16 0
39 LS IV -13 28 Em* 18 19 09.0184675516 -13 43 14.947112994 12.243 11.69 11.23   10.509 B5e 19 0
40 V* EU Ser Ae* 18 19 09.3932056315 -13 50 41.202976046   12.97 14.158   12.923 Be 25 0
41 Cl* NGC 6611 ESL 65 Em* 18 19 10.3004650011 -13 49 03.870866544   13.2 12.80     B9III 13 0
42 NGC 6611 525 * 18 19 13.6876193400 -13 44 27.643754561   15.03 13.29     ~ 7 0
43 NGC 6611 520 * 18 19 13.99 -13 52 21.5   12.10 11.63     B5IIIn 14 0
44 NGC 6611 534 * 18 19 17.6620975667 -13 51 28.845934980   14.45 13.11     G 9 0
45 LS IV -13 30 * 18 19 18.4807638608 -13 55 40.089502487 11.32 11.78 11.42     B1.5V 21 0
46 BD-13 4937 Y*? 18 19 20.0316463029 -13 54 21.680395015 10.53 11.11 10.78     B1.5V 32 1
47 NGC 6611 605 * 18 19 27.8497035183 -14 02 04.555879243   13.06 12.26     ~ 5 0
48 NGC 6611 617 * 18 19 28.55 -13 35 23.5   13.86 12.29     ~ 6 0
49 NGC 6611 611 * 18 19 30.0303669307 -13 44 12.859142194   13.61 11.98     K0V 8 0
50 NGC 6611 606 * 18 19 31.5351147037 -14 01 17.253378107   11.88 11.12     ~ 5 0
51 NGC 6611 614 * 18 19 45.0554138884 -13 37 53.659350361   12.99 12.33     ~ 5 0
52 NGC 6611 373 * ~ ~   14.32 13.38     ~ 2 0

    Equat.    Gal    SGal    Ecl

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2020.02.26-03:22:25

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