2018A&A...613A..12M


Query : 2018A&A...613A..12M

2018A&A...613A..12M - Astronomy and Astrophysics, volume 613A, 12-12 (2018/5-1)

Spectroscopic and physical parameters of Galactic O-type stars. III. Mass discrepancy and rotational mixing.

MARKOVA N., PULS J. and LANGER N.

Abstract (from CDS):

Context. Massive stars play a key role in the evolution of galaxies and our Universe. Aims. Our goal is to compare observed and predicted properties of single Galactic O stars to identify and constrain uncertain physical parameters and processes in stellar evolution and atmosphere models. Methods. We used a sample of 53 objects of all luminosity classes and with spectral types from O3 to O9.7. For 30 of these, we determined the main photospheric and wind parameters, including projected rotational rates accounting for macroturbulence, and He and N surface abundances, using optical spectroscopy and applying the model atmosphere code FASTWIND. For the remaining objects, similar data from the literature, based on analyses by means of the CMFGEN code, were used instead. The properties of our sample were then compared to published predictions based on two grids of single massive star evolution models that include rotationally induced mixing. Results. Any of the considered model grids face problem in simultaneously reproducing the stellar masses, equatorial gravities, surface abundances, and rotation rates of our sample stars. The spectroscopic masses derived for objects below ∼30M tend to be smaller than the evolutionary ones, no matter which of the two grids have been used as a reference. While this result may indicate the need to improve the model atmosphere calculations (e.g. regarding the treatment of turbulent pressure), our analysis shows that the established mass problem cannot be fully explained in terms of inaccurate parameters obtained by quantitative spectroscopy or inadequate model values of Vrot on the zero age main sequence. Within each luminosity class, we find a close correlation of N surface abundance and luminosity, and a stronger N enrichment in more massive and evolved O stars. Additionally, we also find a correlation of the surface nitrogen and helium abundances. The large number of nitrogen-enriched stars above ∼30M argues for rotationally induced mixing as the most likely explanation. However, none of the considered models can match the observed trends correctly, especially in the high mass regime. Conclusions. We confirm mass discrepancy for objects in the low mass O-star regime. We conclude that the rotationally induced mixing of helium to the stellar surface is too strong in some of the models. We also suggest that present inadequacies of the models to represent the N enrichment in more massive stars with relatively slow rotation might be related (among other issues) to problematic efficiencies of rotational mixing. We are left with a picture in which invoking binarity and magnetic fields is required to achieve a more complete agreement of the observed surface properties of a population of massive main-sequence stars with corresponding evolutionary models.

Abstract Copyright: © ESO 2018

Journal keyword(s): stars: early-type - stars: fundamental parameters - stars: evolution - stars: massive - stars: mass-loss

Status at CDS : Objects in title, abstract, text, figures, and all or part of small table(s) being processed in SIMBAD.

Simbad objects: 53

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Number of rows : 53
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 HD 108 SB* 00 06 03.3885906204 +63 40 46.771682957 6.79 7.58 7.40     O4-8f?p 308 0
2 HD 15570 Em* 02 32 49.4205362766 +61 22 42.089023028 8.40 8.80 8.11 7.41 6.86 O4If 287 0
3 NAME Rosette OB Association As* 06 31.7 +04 58           ~ 139 0
4 NGC 2244 OpC 06 31 55 +04 56.5           ~ 577 1
5 HD 46223 Y*O 06 32 09.3066083011 +04 49 24.707398183 6.73 7.50 7.28 6.95 6.79 O4V((f)) 361 0
6 HD 46202 ** 06 32 10.4728 +04 57 59.818 7.60 8.36 8.19 7.98 7.86 O9.2V 261 0
7 HD 46573 SB* 06 34 23.5693132208 +02 32 02.945820029 7.61 8.27 7.93     O7V((f))z 120 0
8 HD 48279 ** 06 42 40.54719 +01 42 58.2571 7.26 8.03 7.86     O8V+F2V 142 0
9 HD 63005 * 07 45 49.0332591007 -26 29 31.433679777 8.29 9.12 9.13 9.64   O5/6 75 0
10 NGC 2467 HII 07 52 18 -26 25.7           ~ 176 1
11 Ass Pup OB 1 As* 07 53 -26.8           ~ 24 0
12 HD 64568 * 07 53 38.2052171216 -26 14 02.593344803 8.64 9.50 9.39 9.77 9.204 O3V((f*))z 94 0
13 HD 69106 * 08 14 03.7993590115 -36 57 07.936730901 6.12 7.020 7.128 8.02   O9.7IIn 114 0
14 HD 69464 Em* 08 15 48.5654685522 -35 37 52.860331301 8.47 9.11 8.80 9.42   O7Ib(f) 98 0
15 HD 75211 * 08 47 01.5923441172 -44 04 28.844578224 7.35 7.90 7.50 8.28   O8.5II((f)) 82 0
16 HD 75222 s*b 08 47 25.1379208787 -36 45 02.670863732 7.24 7.80 7.42 8.22   O9.7Iab 85 0
17 Ass Vel OB 1 As* 08 49.9 -45 00           ~ 94 0
18 CD-44 4865 * 08 50 02.2861134697 -44 34 39.913243836 9.88 10.16 9.63 9.67   B0III 49 0
19 CD-43 4690 * 08 50 52.0463855986 -43 50 22.898381542 10.05 10.48 9.79 9.68   O7.5 27 0
20 HD 76968 V* 08 57 28.8527633493 -50 44 58.192555630 6.53 7.33 7.21 7.01 6.87 O9.2Ib 83 1
21 CD-47 4551 s*b 08 57 54.6180323134 -47 44 15.698082312 9.11 9.41 8.54 8.92   O5Ifc 69 0
22 HD 78344 * 09 05 51.3293958719 -47 46 06.830657900 10.10 10.12 9.00 8.55 8.16 O9.5/B0(Ib) 72 0
23 HD 302505 * 10 05 20.5426661619 -58 44 20.695285548 9.41 9.95 9.89 9.79   B2 30 0
24 HD 91572 * 10 33 12.2652458422 -58 10 13.644176941 7.44 8.29 8.24 9.03   O6.5V((f))z 86 0
25 HD 91824 SB* 10 34 46.6320753376 -58 09 22.038009914 7.17 8.11 8.14 9.02   O7V((f))z 136 0
26 Ass Car OB 1 As* 10 38 -59.0           ~ 148 0
27 HD 92504 * 10 39 36.8681457315 -57 27 40.632007361 7.47 8.38 8.46 9.296   O8.5V(n) 63 0
28 Cl Trumpler 14 OpC 10 43 56 -59 33.0   5.70 5.5     ~ 452 0
29 CD-58 3529 * 10 43 59.9070380728 -59 32 25.447559029 8.631 9.439 9.286 9.73 9.11 O7V((f))z 19 0
30 Cl Collinder 228 OpC 10 44 00 -60 05.2   4.58 4.4     ~ 194 0
31 HD 93204 * 10 44 32.3390160673 -59 44 31.020859370 7.63 8.52 8.42 8.20 7.92 O5.5V((f)) 177 0
32 HD 93222 Y*O 10 44 36.2479580459 -60 05 28.886871750 7.26 8.18 8.10 8.91   O7V((f))z 187 0
33 CD-59 3300 * 10 44 41.7970027863 -59 46 56.403492769 8.07 8.79 8.57 9.33   O6V((f)) 133 0
34 Cl Trumpler 16 OpC 10 45 10 -59 43.0   5.35 5.0     ~ 443 0
35 HD 93843 Er* 10 48 37.7714362588 -60 13 25.516378731 6.37 7.29 7.33 8.23   O5III(fc) 161 0
36 CPD-47 4551 * 10 51 53.3357890711 -48 31 05.054703642   12.50 12.33     ~ 2 0
37 HD 94370B * 10 52 22.9915497609 -58 44 50.480104741           ~ 1 0
38 HD 94370A * 10 52 23.2697690289 -58 44 47.630779808   8.149 8.109     O7(n)fp 6 0
39 HD 94370 ** 10 52 23.277192 -58 44 47.56704 7.19 8.69 8.92 8.84   O7.5III(f) 40 0
40 HD 94963 Em* 10 56 35.7863597984 -61 42 32.283278825 6.35 7.17 7.26 8.10   O7II(f) 76 0
41 Ass Car OB 2 As* 11 08 -60.2           ~ 79 0
42 HD 97848 * 11 14 31.9023996847 -59 01 28.839328749 7.66 8.59 8.60 9.43   O8V 75 0
43 HD 148546 Pu* 16 30 23.3125428650 -37 58 21.171380715 7.28 7.99 7.71 8.58   O9Iab 79 0
44 HD 148937 SB* 16 33 52.3867163783 -48 06 40.476619334 6.49 7.12 6.71 7.61   O6f?p 362 4
45 HD 151804 s*b 16 51 33.7215112148 -41 13 49.928887100 4.45 5.29 5.22     O8Iaf 359 0
46 HD 152003 s*b 16 52 47.3741588958 -41 47 08.991515676 6.90 7.47 7.08 6.72 6.35 O9.7IabNwk 112 1
47 NAME Sco OB 1 As* 16 53.5 -41 57           ~ 196 0
48 NGC 6231 OpC 16 54 08.51 -41 49 36.0   2.83 2.6     ~ 493 0
49 HD 152249 s*b 16 54 11.6391931444 -41 50 57.294733186 5.91 6.65 6.45     OC9Iab 222 0
50 HD 169582 s*b 18 25 43.1467026751 -09 45 11.036987380 8.74 9.24 8.70     O6Iaf 84 0
51 HD 191612 SB* 20 09 28.6111448914 +35 44 01.287772714 7.40 8.07 7.80     O8fpe 221 0
52 HD 207198 * 21 44 53.2790298387 +62 27 38.042162728 5.61 6.25 5.94 5.66 5.49 O8.5II 328 0
53 * 19 Cep * 22 05 08.7884887056 +62 16 47.323982519 4.36 5.19 5.11 4.95 4.92 O9Ib 367 0

    Equat.    Gal    SGal    Ecl

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2021.07.25-13:46:40

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