2003A&A...412...91C

Query : 2003A&A...412...91C

2003A&A...412...91C - Astronomy and Astrophysics, volume 41291-95 (2003/12-2)

Theoretical isochrones for the Δa photometric system.

CLARET A., PAUNZEN E. and MAITZEN H.M.

Abstract (from CDS):

We have calculated theoretical isochrones for the photometric Δa system to derive astrophysical parameters such as the age, reddening and distance modulus for open clusters. The Δa system samples the flux depression at 520nm which is highly efficient to detect chemically peculiar (CP) objects of the upper main sequence. The evolutionary status of CP stars is still a matter of debate and very important to test, for example, the dynamo and diffusion theories. In fact, the dynamo or fossil origin of the magnetic fields present in this kind of star is still not clear. Using the stellar evolutionary models by Claret (1995A&AS..109..441C), a grid of isochrones with different initial chemical compositions for the Δa system was generated. The published data of 23 open clusters were used to fit these isochrones with astrophysical parameters (age, reddening and distance modulus) from the literature. As an additional test, isochrones with the same parameters for Johnson UBV data of these open clusters were also considered. The fits show a good agreement between the observations and the theoretical grid. We find that the accuracy of fitting isochrones to Δa data without the knowledge of the cluster parameters is between 5 and 15%.

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Journal keyword(s): open clusters and associations: general - stars: fundamental parameters

Simbad objects: 23

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Number of rows : 23
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 M 37 OpC 05 52 18.6 +32 32 36           ~ 436 0
2 NGC 2169 OpC 06 08 31.0 +13 57 46   5.99 5.9     ~ 173 0
3 NGC 2439 OpC 07 40 46.5 -31 41 36   7.31 6.9     ~ 150 0
4 NGC 2489 OpC 07 56 15.7 -30 03 35   8.58 7.9     ~ 83 0
5 NGC 2567 OpC 08 18 36.9 -30 38 15   7.77 7.4     ~ 97 0
6 NGC 2658 OpC 08 43 27.6 -32 39 50     9.2     ~ 55 0
7 NGC 3114 OpC 10 01 55.0 -60 02 16   4.47 4.2     ~ 213 0
8 Cl Melotte 105 OpC 11 19 40.6 -63 29 16   9.05 8.5     ~ 81 0
9 NGC 3960 OpC 11 50 36.4 -55 40 40   9.07 8.3     ~ 152 0
10 Cl Collinder 272 OpC 13 30 19.1 -61 18 59   8.25 7.7     ~ 70 0
11 NGC 5281 OpC 13 46 25.8 -62 55 00   6.15 5.9     ~ 92 0
12 Cl Pismis 20 OpC 15 15 23.5 -59 04 23   8.69 7.8     ~ 103 0
13 NGC 6134 OpC 16 27 48.5 -49 09 40   7.89 7.2     ~ 166 0
14 NGC 6192 OpC 16 40 18.7 -43 21 16           ~ 99 0
15 NGC 6204 OpC 16 46 09.1 -47 01 29   8.51 8.2     ~ 139 0
16 NGC 6208 OpC 16 49 20.5 -53 43 27   8.06 7.2     ~ 94 0
17 Cl Lynga 14 OpC 16 55 03 -45 14.3           ~ 44 0
18 NGC 6250 OpC 16 57 55.2 -45 56 48   6.14 5.9     ~ 89 0
19 NGC 6396 OpC 17 37 37.7 -35 00 58   9.41 8.5     ~ 53 0
20 NGC 6451 OpC 17 50 41.5 -30 12 50     8.2     ~ 63 0
21 M 16 OpC 18 18 45.1 -13 47 31           ~ 1084 1
22 NGC 6705 OpC 18 51 03.7 -06 16 18   6.32 5.8     ~ 442 0
23 NGC 6756 OpC 19 08 43.5 +04 42 41     10.6     ~ 43 0

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