2011A&A...528A.127M


C.D.S. - SIMBAD4 rel 1.7 - 2019.12.11CET15:00:00

2011A&A...528A.127M - Astronomy and Astrophysics, volume 528A, 127-127 (2011/4-1)

A lack of close binaries among hot horizontal branch stars in globular clusters. II. NGC 2808.

MONI BIDIN C., VILLANOVA S., PIOTTO G. and MOMANY Y.

Abstract (from CDS):

The formation mechanism of hot horizontal branch (HB) stars is still one of the most uncertain points of stellar evolution theories. In the past decade, models based on their binary origin have been very successful in reproducing the properties of field subdwarf-B stars, but the observations of their analogues in globular clusters has posed new problems. In addition, the discovery of multiple populations offered an appealing alternative scenario for the formation of these stars. We search for binaries of period ≤200-days among a sample of 83 blue horizontal branch stars (Teff=12000-22000K) in NGC2808, a cluster known to host three distinct stellar populations and a multimodal horizontal branch. The final sample, after the rejection of stars with incomplete observations or poor quality data, consists of 64 targets. The radial velocity of the targets was measured in fourteen epochs, spanning a temporal interval of ∼75-days. The significant variations were identified by means of a detailed error analysis and a statistical study. We detect no RV variable object among stars cooler than the photometric G1 gap at ∼17000K, while two close (≤10-days) and two intermediate-period (=10-50-days) systems are found among hotter targets. The close and intermediate-period binary fraction for stars cooler than the gap are fc≤5% and fip≤10%, respectively, with 95% confidence. The most probable values among hotter stars are fc∼20% and fip∼30%, but the 90%-confidence level intervals are still large (6-42% and 11-72%, respectively). The G1 gap appears as a discontinuity in the binary faction along the HB, with a higher incidence of binaries among hotter stars, but a constant increase in f with temperature rather than a discontinuity cannot be excluded from our observations. We also find that intermediate-period binaries, never investigated before among cluster HB stars, could play an important role among hotter stars, being more than ∼15-20% of the hottest stars of our sample. Our results, compared with previous estimates for other clusters, indicate that fc among hot HB stars is most probably higher for younger clusters, confirming the recently proposed age-fc relation. However, the large observed difference in binary fraction between clusters (e.g. NGC2808 and NGC6752) is still not reproduced by binary population synthesis models.

Abstract Copyright:

Journal keyword(s): stars: horizontal-branch - binaries: close - binaries: spectroscopic - globular clusters: individual: NGC2808

VizieR on-line data: <Available at CDS (J/A+A/528/A127): table3.dat>

Nomenclature: Table 3: [MVP2011] NNNNN N=83 among (Nos 7227-58322).

Simbad objects: 90

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Number of rows : 90

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 [MVP2011] 32516 HB* 09 11 16.93 -64 52 53.6 17.246   17.508     ~ 1 0
2 [MVP2011] 32888 HB* 09 11 18.78 -64 52 32.7 17.945   18.315     ~ 1 0
3 [MVP2011] 35362 HB* 09 11 19.47 -64 50 04.2 17.639   17.882     ~ 1 0
4 [MVP2011] 13467 HB* 09 11 22.2012309836 -64 49 11.539808481 18.438   18.996     ~ 1 0
5 [MVP2011] 32670 HB* 09 11 24.84 -64 52 45.5 17.779   18.509     ~ 2 0
6 Cl* NGC 2808 PKD 14923 * 09 11 27.83 -64 46 22.5 17.211 17.58 17.471     ~ 2 0
7 [MVP2011] 34446 HB* 09 11 31.0042328300 -64 51 04.446687655 18.423   18.962     ~ 1 0
8 [MSL2004] J091133.72-645624.9 * 09 11 33.68 -64 56 24.9 18.475 19.35 19.269     ~ 2 0
9 [MVP2011] 13405 HB* 09 11 41.82 -64 49 16.1 17.518   17.807     ~ 1 0
10 [SDS2012] NGC 2808 350 HB* 09 11 41.8828176774 -64 42 05.698489345 17.043   17.975     ~ 2 0
11 [MVP2011] 33067 HB* 09 11 42.45 -64 52 23.4 17.415   17.740     ~ 1 0
12 [MVP2011] 50769 HB* 09 11 44.40 -64 51 29.6 17.476   17.859     ~ 1 0
13 [MVP2011] 53751 HB* 09 11 45.60 -64 50 41.9 17.329   17.597     ~ 1 0
14 Cl* NGC 2808 PKD 39744 * 09 11 46.36 -64 54 57.9 17.114 17.46 17.402     ~ 2 0
15 [MVP2011] 54675 HB* 09 11 46.80 -64 50 27.4 17.171   17.516     ~ 1 0
16 [MVP2011] 51656 HB* 09 11 48.40 -64 51 15.3 17.405   17.754     ~ 1 0
17 [MVP2011] 43170 HB* 09 11 48.45 -64 53 34.1 17.316   17.649     ~ 1 0
18 [MVP2011] 54539 HB* 09 11 50.81 -64 50 29.9 18.021   18.906     ~ 2 0
19 [MVP2011] 49443 HB* 09 11 51.16 -64 51 50.0 17.194   17.460     ~ 1 0
20 [MVP2011] 52012 HB* 09 11 51.63 -64 51 09.6 17.119   17.414     ~ 1 0
21 [MVP2011] 7700 HB* 09 11 52.41 -64 49 18.1 18.658   19.168     ~ 1 0
22 [MVP2011] 41115 HB* 09 11 52.59 -64 54 17.0 17.347   17.782     ~ 1 0
23 [MVP2011] 55009 HB* 09 11 52.90 -64 50 22.1 17.482   17.807     ~ 1 0
24 [MVP2011] 43287 HB* 09 11 53.32 -64 53 32.1 18.449   18.913     ~ 1 0
25 [MVP2011] 49321 HB* 09 11 54.05 -64 51 52.0 17.531   18.029     ~ 1 0
26 [MVP2011] 47972 HB* 09 11 54.83 -64 52 12.8 17.252   17.514     ~ 1 0
27 [MVP2011] 47037 HB* 09 11 54.86 -64 52 27.7 17.126   17.389     ~ 1 0
28 [MVP2011] 44295 HB* 09 11 55.54 -64 53 13.9 17.181   17.507     ~ 1 0
29 [MVP2011] 45980 HB* 09 11 56.65 -64 52 45.4 17.991   18.354     ~ 1 0
30 [MVP2011] 53800 HB* 09 11 57.356 -64 50 41.15 17.252   17.604     ~ 1 0
31 [MVP2011] 45042 HB* 09 11 58.06 -64 53 01.3 17.551   17.969     ~ 1 0
32 [MVP2011] 51455 HB* 09 11 58.74 -64 51 18.5 17.128   17.422     ~ 1 0
33 [MSL2004] J091158.81-645645.6 * 09 11 58.76 -64 56 45.5 18.687 19.41 19.229     ~ 2 0
34 [MVP2011] 9715 HB* 09 11 59.5713949315 -64 47 44.306321350 18.275   18.772     ~ 1 0
35 [MVP2011] 44070 HB* 09 12 00.17 -64 53 18.0 18.172   18.567     ~ 1 0
36 [MVP2011] 39433 HB* 09 12 01.8553538494 -64 55 09.594384642 17.438   17.915     ~ 1 0
37 [MVP2011] 45677 HB* 09 12 02.04 -64 52 50.4 17.196   17.582     ~ 1 0
38 [MVP2011] 39797 HB* 09 12 02.88 -64 54 55.8 17.397   17.778     ~ 1 0
39 IRAS 09110-6439 GlC 09 12 03.10 -64 51 48.6   7.77 5.69     ~ 1208 0
40 [MVP2011] 43840 HB* 09 12 03.54 -64 53 21.9 17.312   17.698     ~ 1 0
41 [MVP2011] 53504 HB* 09 12 03.67 -64 50 45.8 17.87   18.348     ~ 1 0
42 [MVP2011] 47336 HB* 09 12 04.59 -64 52 22.7 17.545   17.782     ~ 1 0
43 [MVP2011] 42482 HB* 09 12 05.53 -64 53 47.3 17.819   18.712     ~ 2 0
44 [MVP2011] 7227 HB* 09 12 06.11 -64 49 32.6 17.769   18.172     ~ 1 0
45 [MVP2011] 43422 HB* 09 12 06.35 -64 53 29.6 17.576   18.028     ~ 1 0
46 [MVP2011] 54434 HB* 09 12 07.09 -64 50 31.4 17.519   17.890     ~ 1 0
47 [MSL2004] J091207.20-645441.1 * 09 12 07.13 -64 54 41.3 18.66 19.39 19.395     ~ 2 0
48 [MVP2011] 47936 HB* 09 12 07.89 -64 52 13.3 17.437   17.902     ~ 1 0
49 [MVP2011] 51625 HB* 09 12 08.02 -64 51 15.8 17.311   17.750     ~ 1 0
50 [MVP2011] 46512 HB* 09 12 08.506 -64 52 37.00 17.317   17.690     ~ 1 0
51 [MVP2011] 49247 HB* 09 12 08.85 -64 51 53.0 17.276   17.519     ~ 1 0
52 [MVP2011] 57252 HB* 09 12 09.32 -64 49 43.1 17.231   17.450     ~ 1 0
53 [MVP2011] 47593 HB* 09 12 09.69 -64 52 18.3 17.32   17.632     ~ 1 0
54 [MVP2011] 39922 HB* 09 12 10.73 -64 54 51.2 17.184   17.412     ~ 1 0
55 [MVP2011] 52126 HB* 09 12 11.18 -64 51 07.6 17.712   18.098     ~ 1 0
56 [MVP2011] 46460 HB* 09 12 11.77 -64 52 37.3 17.68   18.029     ~ 1 0
57 [MVP2011] 53679 HB* 09 12 11.84 -64 50 43.0 17.292   17.470     ~ 1 0
58 [MVP2011] 8607 HB* 09 12 11.953 -64 48 42.22 17.291   17.545     ~ 1 0
59 [MVP2011] 37345 HB* 09 12 12.4700144824 -64 57 26.974297198 17.984   17.916     ~ 1 0
60 [MVP2011] 51077 HB* 09 12 14.46 -64 51 24.4 18.238   18.978     ~ 1 0
61 [MVP2011] 55692 HB* 09 12 15.38 -64 50 10.2 17.507   17.804     ~ 1 0
62 [MVP2011] 10078 HB* 09 12 17.1471628742 -64 47 17.072619529 18.321   18.894     ~ 1 0
63 [MVP2011] 45166 HB* 09 12 17.4620559334 -64 52 59.007584182 17.204   17.626     ~ 1 0
64 [MVP2011] 46155 HB* 09 12 18.44 -64 52 42.3 17.663   18.169     ~ 1 0
65 [MVP2011] 50078 HB* 09 12 20.46 -64 51 40.3 17.646   18.014     ~ 1 0
66 [MSL2004] J091220.68-645309.4 * 09 12 20.5886127490 -64 53 09.541073341 18.588 19.37 19.249     ~ 2 0
67 [MVP2011] 9121 HB* 09 12 21.71 -64 48 18.3 17.805   18.296     ~ 1 0
68 [MVP2011] 46398 HB* 09 12 22.04 -64 52 38.1 16.89   17.585     ~ 2 0
69 [MVP2011] 53681 HB* 09 12 22.70 -64 50 42.8 18.475   19.095     ~ 1 0
70 [MVP2011] 48326 HB* 09 12 23.85 -64 52 07.1 18.173   18.846     ~ 1 0
71 [MVP2011] 50965 HB* 09 12 24.44 -64 51 26.1 17.426   17.714     ~ 1 0
72 [MVP2011] 10719 HB* 09 12 24.79 -64 46 09.9 17.465   17.795     ~ 1 0
73 [MVP2011] 50410 HB* 09 12 28.99 -64 51 35.0 17.779   18.232     ~ 1 0
74 [MVP2011] 10620 HB* 09 12 29.08 -64 46 20.8 17.587   17.956     ~ 1 0
75 [MVP2011] 46960 HB* 09 12 29.17 -64 52 28.7 17.476   17.840     ~ 1 0
76 [MSL2004] J091229.81-644756.1 * 09 12 29.66 -64 47 56.3 18.652 19.37 19.271     ~ 2 0
77 [MVP2011] 41203 HB* 09 12 31.09 -64 54 14.5 17.665   18.063     ~ 1 0
78 [MVP2011] 55759 HB* 09 12 32.23 -64 50 08.8 18.436   19.064     ~ 1 0
79 [MVP2011] 47443 HB* 09 12 33.4313874283 -64 52 20.446711706 17.377   17.751     ~ 1 0
80 [MVP2011] 58322 HB* 09 12 34.0872937781 -65 01 05.848742565 17.27   17.683     ~ 1 0
81 [MVP2011] 37288 HB* 09 12 34.3607677012 -64 57 33.483572681 17.297   17.691     ~ 1 0
82 [MVP2011] 50088 HB* 09 12 37.34 -64 51 39.8 17.447   17.795     ~ 1 0
83 [MVP2011] 52303 HB* 09 12 53.6826472111 -64 51 03.858640752 18.34   18.872     ~ 1 0
84 [MVP2011] 11623 HB* 09 12 59.5319126316 -64 42 51.505885648 18.338   18.997     ~ 1 0
85 NGC 5139 GlC 13 26 47.28 -47 28 46.1   6.12 5.33     ~ 2922 0
86 NGC 5986 GlC 15 46 03.00 -37 47 11.1     6.92     ~ 293 0
87 M 80 GlC 16 17 02.41 -22 58 33.9           ~ 598 0
88 M 4 GlC 16 23 35.22 -26 31 32.7           ~ 1639 0
89 NGC 6752 GlC 19 10 52.11 -59 59 04.4   6.96 6.28     ~ 1769 0
90 NGC 6791 OpC 19 20 53 +37 46.3   10.52 9.5     ~ 847 0

    Equat.    Gal    SGal    Ecl

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2019.12.11-15:00:00

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