1995A&A...300..751A


Query : 1995A&A...300..751A

1995A&A...300..751A - Astronomy and Astrophysics, volume 300, 751-768 (1995/8-3)

Spectroscopic analyses of metal-poor stars. II. The evolutionary stage of subdwarfs.

AXER M., FUHRMANN K. and GEHREN T.

Abstract (from CDS):

Models of post-main sequence stellar evolution of VandenBerg & Bell (1985) have been applied to determine spectroscopic masses and distances for metal-poor stars. Careful consideration of the most important error sources published in more recent papers such as VandenBerg (1992) for the first time allow us to draw firm statistical conclusions. It is shown that the evolutionary calculations qualitatively fit to the observed stellar parameters whereas quantitatively they predict too high ages for metal-poor stars. As an important result we confirm that evolutionary sequences need to be calibrated with respect to their metal abundance in order to use their absolute predictions of temperature and luminosity. It turns out that this can be achieved by a simple shift of the evolutionary tracks and isochrones in effective temperature with values {DELTA}log Teff≲0.03 which accounts for possible changes of the mixing-length and the O/Fe ratio with metallicity. The stellar luminosities and surface gravities obtained from evolutionary models are much more reliable than their effective temperatures. Therefore we conclude that the accuracy of the corresponding spectroscopic stellar gravities is systematically affected by deviations from LTE, in particular along the subgiant sequence where systematic errors less than {DELTA}log g ≃0.3 must be ascribed to the non-LTE ionization equilibrium of Fe II/Fe I. In our spectroscopic analyses the strong dependence between surface gravity and abundances determined from Fe I lines restricts the accuracy of Fe abundances in subgiants to 0.1 dex at best. The most remarkable result of our evolutionary and kinematic investigations of halo stars refers to the large fraction of slightly evolved subgiants among the so-called subdwarfs. Since conventional photometric approaches often assume that the great majority of metal-poor stars are dwarfs this results in distances that are systematically too low for their samples. Consequently, significant differences are found when comparing evolutionary and kinematic parameters obtained from either photometric or spectroscopic data. We demonstrate this by comparing the space velocities of the stars. It appears that stars with particularly high space velocities derived from spectroscopic distances show very often much lower velocities based on their main sequence parallaxes. We find that results refering to main sequence parallaxes are doubtful and can be used only with greatest care. An advantageous side-effect of the application of spectroscopic data to evolutionary calculations is the possibility to identify binary systems that are either standing out from the Toomre diagram with their unusually high space velocities, or from a log g - log Teff diagram with apparently contradictory luminosities.

Abstract Copyright:

Journal keyword(s): stars: distances - stars: evolution - stars: fundamental parameters - stars: kinematics - stars: subdwarfs

VizieR on-line data: <Available at CDS (J/A+A/300/751): table1 table3 table4 table5>

Simbad objects: 113

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Number of rows : 113
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 * 85 Peg SB* 00 02 10.3487193861 +27 04 54.599101714 6.47 6.42 5.75 5.16 4.73 G5VbFe-2 534 0
2 HD 3567 PM* 00 38 31.9473242153 -08 18 33.392826667 9.54 9.70 9.23     F7/8wF3 198 0
3 HD 6434 PM* 01 04 40.1502696688 -39 29 17.584220159   8.32 7.71     G2/3V 218 1
4 * mu. Cas SB* 01 08 16.3029454473 +54 55 12.561201263 5.93 5.86 5.17 4.55 4.13 G5Vb 557 1
5 HD 7983 PM* 01 18 59.9850724126 -08 56 22.186543721 9.48 9.49 8.90 8.36 8.00 G3V 109 0
6 Wolf 67 PM* 01 26 55.1715472335 +12 00 25.835100566   11.860 11.358 11.020 10.679 F8 45 0
7 HD 10607 PM* 01 41 14.6907033683 -67 40 37.122568730   8.87 8.32     G0Vm-2.25 84 0
8 BD+72 94 PM* 01 47 12.3861117384 +73 28 27.195387600 10.10 10.33   9.8   sdF2: 103 0
9 BD+29 366 PM* 02 10 24.5274364299 +29 48 23.663397433 9.27 9.35 8.77 8.24 7.85 G3 130 0
10 BD-01 306 PM* 02 14 40.2989460555 -01 12 05.123909214 9.60 9.631 9.066 8.712 8.377 G0 140 0
11 HD 16784 PM* 02 40 38.7783197140 -30 08 07.460222152   8.699 8.02     F8V 105 0
12 BD+09 352 ** 02 41 13.6396003457 +09 46 12.100750635 10.37 10.62   10.0   kA7.5hF8 90 0
13 BD+46 610 SB* 02 41 45.7397605656 +47 21 01.290205512       8.8   F8 59 0
14 G 4-36 PM* 02 43 22.0483919796 +13 25 56.981522451   11.989 11.471 11.133 10.795 ~ 66 0
15 HD 19445 PM* 03 08 25.5883873084 +26 19 51.400965175 8.29 8.52 8.06 7.60 7.27 G2VFe-3 755 0
16 * zet02 Ret ** 03 18 12.8188824117 -62 30 22.904711032   5.814 5.228     G1V 346 0
17 BD+66 268 PM* 03 31 17.4003449284 +66 43 49.024902152 10.48 10.57 9.91 9.30 8.87 G0 163 0
18 HD 22879 Pe* 03 40 22.0652879951 -03 13 01.124265616 7.146 7.222 6.667 6.346 6.016 G0VmF2 469 0
19 HD 284248 PM* 04 14 35.5161858536 +22 21 04.252516252 9.49 9.68 9.23 8.77 8.43 sdG0 175 0
20 HD 31128 PM* 04 52 09.9097086888 -27 03 50.940147636   9.55 9.14     F3/5Vw 127 0
21 BD+03 740 HB* 05 01 16.6226363256 +04 06 37.021736844 9.97 10.17   9.6   sdF0 168 0
22 G 99-48 SB* 05 59 05.9748535952 +04 10 38.584848531   12.58   11.2   ~ 36 0
23 HD 250792 ** 06 03 14.8636143602 +19 21 38.696218609 9.89 9.898 9.310 8.954 8.547 G1 155 0
24 BD+37 1458 PM* 06 16 01.5222885381 +37 43 18.754343426 9.41 9.52 8.92 8.34 7.91 G0 131 0
25 HD 45282 Pe* 06 26 40.7720940072 +03 25 29.792391024 8.71 8.69 8.03     Gwl 147 0
26 HD 46341 PM* 06 32 37.9911814872 -06 29 18.504485016   9.16 8.60     G2V 72 0
27 CD-33 3337 PM* 06 54 47.8101117384 -33 44 49.024262364   9.56 9.03     F5 91 0
28 HD 51929 PM* 06 55 53.2199607424 -56 56 32.625629720   8.02 7.43     G2VFe-1.4CH-0.7 119 0
29 G 88-23 PM* 07 23 17.5718823024 +19 00 56.590285896   12.485 12.000 11.685 11.357 ~ 25 0
30 HD 59374 PM* 07 30 29.0166014070 +18 57 40.616629308   9.03   8.2   F9 111 0
31 BD+24 1676 PM* 07 30 41.2662525096 +24 05 10.248524088   11.15   10.4   F 118 0
32 HD 64090 PM* 07 53 33.1208795337 +30 36 18.256204963 8.75 8.86 8.25 7.70 7.30 K0:V_Fe-3 351 0
33 HD 69611 PM* 08 17 29.3481646355 -03 59 22.623439715   8.32 7.74     G0V 130 0
34 HD 74000 PM* 08 40 50.8036114756 -16 20 42.516208237 9.84 10.09 9.66     F2 255 0
35 BD-05 2678 ** 08 59 03.3656846900 -06 23 46.179302908   12.515 11.968 11.540 11.159 F7 72 0
36 BD+09 2190 PM* 09 29 15.5615542183 +08 38 00.467004388   11.54   10.8   sdA5 126 0
37 Ross 889 Pe* 09 40 43.2053340378 +01 00 29.511836741       10.39   sdA4 158 0
38 HD 87140 PM* 10 04 43.1808079344 +54 20 43.425537648 9.70 9.68 8.98     K0 109 0
39 HD 88261 PM* 10 09 49.5816323797 -36 45 14.955192778   8.69 8.07     G3V 71 0
40 HD 298986 PM* 10 17 14.8774744591 -52 29 18.694800089   10.46 10.03   9.48 F5 79 0
41 G 236-30 SB* 10 28 48.3760028720 +62 59 44.592409672   13.62   12.5   ~ 23 0
42 HD 91345 Pe* 10 30 04.6048336584 -71 33 39.248662428   9.757 9.510     G0wF3 70 0
43 Ross 106 PM* 10 50 29.1185841915 +56 26 30.821960145   13.18   11.9   G8: 46 0
44 HD 94518 PM* 10 54 12.2052600328 -31 09 34.587440322   8.95 8.36     G2V 76 0
45 HD 97320 Pe* 11 11 00.7344001848 -65 25 37.745815656   9.769 9.269     F3V 135 0
46 BD+36 2165 PM* 11 12 47.9997679646 +35 43 43.885058670 9.98 10.19 9.76 9.34 9.02 G0 129 0
47 HD 97855 PM* 11 16 04.0344771096 +52 46 23.384130708       6.2   F6VgF6mF3 93 0
48 HD 99383 Pe* 11 25 49.8351777360 -38 52 16.936102452   9.56 9.08     F2V 79 0
49 HD 101227 PM* 11 39 06.2189103744 +44 18 20.295031968 9.14 9.08   8.0   G0 64 1
50 HD 102200 Pe* 11 45 34.2345453384 -46 03 46.386995400   9.13 8.76     F2V 103 0
51 HD 106411 PM* 12 14 32.2342883688 -44 06 21.685821948   9.85 9.27     F7V 42 0
52 HD 106516 SB* 12 15 10.55731 -10 18 44.6354 6.44 6.57 6.11     F9VFe-1.7CH-0.7 402 0
53 HD 108076 PM* 12 24 45.8890146375 +38 19 07.459717466   8.58   7.7   G0V 107 0
54 HD 108177 PM* 12 25 34.9568267745 +01 17 02.259553591 9.87 10.09 9.66 9.21 8.89 F0V 243 0
55 HD 108405 PM* 12 27 28.4358609740 -48 07 52.783491635   9.87 9.28     G3V 47 0
56 HD 111980 SB* 12 53 15.0529661499 -18 31 20.013189741 8.80 8.91 8.38     F7V 164 0
57 HD 111971 ** 12 53 42.46017 -57 39 23.0781   9.20 8.93 8.57   F7V 55 0
58 HD 114762 SB* 13 12 19.7410686234 +17 31 01.630334317 7.78         F9VgF8mF4+M6?V 529 1
59 HD 116064 Pe* 13 21 43.7779908364 -39 18 40.025179966   9.26 8.81     F9IV-Vm-5 128 0
60 G 255-32 SB* 13 21 47.6238772026 +74 12 32.820477741       11.1   G0 48 0
61 HD 118659 PM* 13 38 00.4711997282 +19 08 53.098205358 9.58 9.47   8.4   G4V 85 0
62 Wolf 1492 Pe* 13 40 02.4921849768 -00 02 18.750053436 11.601 11.832 11.451 11.184 10.892 sdF0: 273 0
63 HD 120559 PM* 13 51 40.3987847839 -57 26 08.350982731 8.679 8.647 7.982 7.605 7.217 G7VFe-1.4CH-1 149 0
64 HD 121004 PM* 13 53 58.1163626566 -46 32 19.522719077   10.112 9.522     G2V 143 0
65 HD 121387 PM* 13 58 17.5687615392 -72 19 25.370514408   8.99 8.61     F5wA9(V) 33 0
66 HD 122196 PM* 14 01 02.1249985961 -38 03 03.313496920   9.19 8.75     F0(V)w 115 0
67 Ross 841 Pe* 14 02 30.0900761861 -05 39 05.181979951   11.508 11.149 10.866 10.576 sdA3 147 0
68 G 239-12 PM* 14 18 52.5510798024 +73 14 14.711086500       11.3   ~ 25 0
69 G 66-9 PM* 14 35 12.7359317489 +12 13 19.278257815   12.438 11.968 11.650 11.306 ~ 37 0
70 HD 128279 Pe* 14 36 48.5108525999 -29 06 46.612858494 8.64 8.63 8.00     Gw 185 0
71 BD+26 2606 SB* 14 49 02.3593347728 +25 42 09.192358874 9.92 10.16 9.73 9.27 8.95 A5 362 0
72 HD 140283 Pe* 15 43 03.0971190219 -10 56 00.595693188 7.508 7.711 7.212 6.63 8.21 F9VkA5mA1 896 0
73 HD 148211 PM* 16 27 12.8994797097 -22 07 36.476820152   8.22 7.69     F8/G0V 118 0
74 G 180-58 PM* 16 28 16.8722964664 +44 40 38.256976267   11.97   10.6   G5 72 0
75 G 169-21 PM* 16 37 05.2325496648 +31 19 24.089765340       11.7   ~ 20 0
76 HD 155918 PM* 17 22 12.6496174165 -75 20 53.340031047   7.60 7.04     G2VFe-1.0CH-0.6 100 0
77 HD 158226 PM* 17 26 43.1968765468 +31 04 37.895885806   9.09   8.1   G1V 107 0
78 BD+23 3130 Pe* 17 32 41.6247211304 +23 44 11.625460773       8.6   G0III 125 0
79 HD 159482 PM* 17 34 43.0816088882 +06 00 51.815208744   8.95   8.0   G0V 151 0
80 BD+02 3375 PM* 17 39 45.5948675731 +02 24 59.606824535 10.18 10.40 9.92 9.47 9.12 A5 191 0
81 HD 160617 PM* 17 42 49.3234249010 -40 19 15.503834657   9.18 8.73 8.394 8.065 G0 195 0
82 * b Her SB* 18 07 01.5906608928 +30 33 43.584892488 5.52 5.67 5.13 4.61 4.28 F6V 442 0
83 HD 166913 PM* 18 16 25.6832938176 -59 24 11.239435980   8.66 8.23     F5/7Vw 128 0
84 Ross 711 SB* 18 35 19.1686289616 +28 41 55.415394492   11.83   11.2   A8 92 0
85 HD 174912 PM* 18 51 25.1792851207 +38 37 35.654019974       6.8   F8 115 0
86 HD 176021 Pe* 19 02 37.2793430297 -64 55 30.899376508   8.20 7.58     G0/1III 74 0
87 HD 181720 PM* 19 22 52.9849923689 -32 55 08.589079621   8.44 7.86     G1V 109 1
88 HD 338529 PM* 19 32 31.9104668184 +26 23 26.117367216   9.72   9.2   B5 204 0
89 HD 188510 PM* 19 55 09.6782304000 +10 44 27.398607828 9.30 9.41   8.5   G5V: 244 0
90 HD 189558 PM* 20 01 00.2452184673 -12 15 20.353638621   8.28 7.73     F8/G2V 181 0
91 BD+42 3607 PM* 20 09 01.4132638739 +42 51 54.930960323       9.9   F3 81 0
92 HD 193901 PM* 20 23 35.8471605389 -21 22 14.226959304 9.08 9.22 8.67 8.17 7.87 F7V 270 0
93 HD 194598 PM* 20 26 11.9183775668 +09 27 00.429558608 8.62 8.82 8.34 7.90 7.56 F8 294 0
94 HD 196892 PM* 20 40 49.3802982816 -18 47 33.282293972   8.73 8.23     F6V 118 0
95 HD 198245 PM* 20 50 22.5567684068 -40 36 30.498682353   9.57 8.98     G3V 47 0
96 BD+41 3931 PM* 20 55 16.7551875178 +42 18 00.680491946       10.0   G5 91 0
97 HD 199288 PM* 20 57 40.0687221764 -44 07 45.733001992   7.11 6.52     G2VFe-1.0 183 0
98 HD 200654 Pe* 21 06 34.7513254468 -49 57 50.280288000   9.74 9.11     CEMP 101 0
99 HD 201891 PM* 21 11 59.0321495469 +17 43 39.890919730 7.74 7.88 7.37 6.91 6.59 G5V_Fe-2.5 378 0
100 HD 201889 ** 21 11 59.52350 +24 10 05.3897 8.60 8.64 8.05 7.52 7.15 G1V 153 0
101 G 25-22 PM* 21 14 48.4695663205 +11 00 30.239710083   12.88 12.32 12.0   F8: 40 0
102 * gam Pav PM* 21 26 26.6049826473 -65 21 58.313057521 4.57 4.70 4.22 3.75 3.45 F9VFe-1.4CH-0.7 396 0
103 HD 204155 PM* 21 26 42.9050916792 +05 26 29.902289568   9.03   8.1   F7V 123 0
104 HD 205156 PM* 21 34 50.9565047437 -49 47 35.059531817   8.74 8.16     G3V 84 0
105 HD 205650 PM* 21 37 26.0286639804 -27 38 06.697265704   9.59 9.00     F6V 99 0
106 HD 205582 PM* 21 40 23.8516742122 -71 30 12.000935749   7.97 7.43     F8/G0V 34 0
107 * 15 Peg PM* 21 52 29.9168018496 +28 47 36.750679764 5.82 5.95 5.53     F2V 234 0
108 Wolf 984 PM* 22 05 01.4078789977 +08 38 18.903030093   12.61   11.2   sdF8: 42 0
109 BD+17 4708 SB* 22 11 31.3756832854 +18 05 34.177983548 9.73 9.91 9.46 9.03 8.70 sdF8 555 0
110 * nu. Ind ** 22 24 36.8853892493 -72 15 19.488237466   5.94 5.29     G9VFe-3.1CH-1.5 264 0
111 Ross 288 PM* 22 44 56.3048714972 -02 21 12.779684696   12.127 11.491 11.075 10.668 K0 53 0
112 BD+38 4955 SB* 23 13 38.8205905578 +39 25 02.589638688 11.52 11.67 11.01 10.38 9.92 F6 117 0
113 HD 219617 ** 23 17 05.04375 -13 51 03.5971 8.41 8.60 8.14 7.70 7.37 F8 305 0

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2022.09.26-09:21:57

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