2009A&A...505..743V


Query : 2009A&A...505..743V

2009A&A...505..743V - Astronomy and Astrophysics, volume 505, 743-753 (2009/10-2)

On the presence and absence of disks around O-type stars.

VINK JORICK S., DAVIES B., HARRIES T.J., OUDMAIJER R.D. and WALBORN N.R.

Abstract (from CDS):

As the favoured progenitors of long-duration gamma-ray bursts, massive stars may represent our best signposts of individual objects in the early Universe, but special conditions seem required to make these bursters. These are thought to originate from the progenitor's rapid rotation and associated asymmetry. To obtain empirical constraints on the interplay between stellar rotation and wind asymmetry, we perform linear Hα spectropolarimetry on a sample of 18 spectroscopically peculiar massive O stars, including OVz, Of?p, Oe, and Onfp stars, supplemented by an earlier sample of 20 O supergiants of Harries et al. (2002MNRAS.337..341H), yielding a total number of 38 O-type stars. Our study's global aim is to characterize the differences between, and similarities amongst, different classes of peculiar O stars and to establish in how far they differ from garden-variety O stars. Our linear (Stokes QU) spectropolarimetry data should be regarded a geometric counterpart to (Stokes I) spectral classification, setting the stage for circular (Stokes V) polarimetric searches for magnetic fields. Despite their rapid rotation (with vsin i up to ∼400km/s) most O-type stars are found to be spherically symmetric, but with notable exceptions amongst specific object classes. We divide the peculiar O stars into four distinct categories: Group I includes the suspected young zero-age main sequence OVz stars and related weak-winds objects, of which the magnetic star Θ1 Ori C is the most famous member. These objects show no evidence for significant linear polarization. Group II includes the Of?p stars, in which one of its members, HD 191612, was also found to be magnetic. These objects show more linear polarization activity than those in Group I. Group III includes the Oe stars, which have been suggested to be the more massive counterparts to classical Be stars, and Group IV concerns the Onfp stars. Objects from the latter two groups are on the high-end tail of the O-star rotation distribution and have in the past been claimed to be embedded in disks. Here we report the detection of a classical depolarization ``line effect'' in the Oe star HD45314, but the overall incidence of line effects amongst Oe stars is significantly lower (1 out of 6) than amongst Be stars. The chance that the Oe and Be datasets are drawn from the same parent population is negligible (with 95% confidence). This implies there is as yet no evidence for a disk hypothesis in Oe stars, providing relevant constraints on the physical mechanism that is responsible for the Be phenomenon. Finally, we find that 3 out of 4 of the Group IV Onfp stars show evidence for complex polarization effects, which are likely related to rapid rotation, and we speculate on the evolutionary links to B[e] stars.

Abstract Copyright:

Journal keyword(s): stars: chemically peculiar - polarization - stars: winds, outflows - supergiants - stars: formation - circumstellar matter

Simbad objects: 28

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Number of rows : 28
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 HD 108 SB* 00 06 03.3890541936 +63 40 46.771220928 6.79 7.58 7.40     O4-8f?p 319 0
2 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 6562 1
3 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 16522 1
4 NAME Orion Nebula Cluster OpC 05 35.0 -05 29           ~ 2209 1
5 * tet01 Ori C SB* 05 35 16.4662967280 -05 23 22.921811880 4.20 5.15 5.13 4.91 4.73 O7Vp 1368 1
6 * tet02 Ori A SB* 05 35 22.9012398264 -05 24 57.832632108 5.37 6.30 6.39 6.30 6.35 O9.5IVp 530 0
7 * sig Ori E Y*O 05 38 47.2050040320 -02 35 40.521424812 5.66 6.38 6.46 6.84 7.08 B2IV-Vp_He 441 0
8 * zet Ori ** 05 40 45.52666 -01 56 33.2649 0.50 1.56 1.77 1.85 2.05 O9.7Ib+B0III 345 0
9 HD 39680 Be* 05 54 44.7315378936 +13 51 17.064365364 7.05 8.01 7.99     O6V:[n]pevar 119 0
10 HD 42088 * 06 09 39.5728368936 +20 29 15.450599580 6.73 7.58 7.57 8.45   O6V((f))z 241 0
11 HD 45314 Be* 06 27 15.7784072112 +14 53 21.212913660 5.91 6.79 6.64     O9:npe 168 0
12 HD 46485 Y*O 06 33 50.9566745256 +04 31 31.613196504 7.92 8.60 8.27   8.10 O7V((f))nzvar? 141 0
13 HD 54662 SB* 07 09 20.2493151288 -10 20 47.635088964 5.35 6.24 6.21 7.23   O6.5Vz(n)+O7.5Vz 334 2
14 HD 60848 Be* 07 37 05.7325392528 +16 54 15.300327852 5.55 6.67 6.87     O8:V:pe 136 0
15 * zet Pup BY* 08 03 35.04754 -40 00 11.3321 0.89 1.98 2.25 2.36 2.58 O4I(n)fp 1139 1
16 CD-58 3526 * 10 43 46.6855999968 -59 32 54.846500640 9.161 9.884 9.593 9.84 9.13 O6V((f))z 65 0
17 HD 93128 SB* 10 43 54.3957741024 -59 32 57.497266716 8.82 8.97 8.77 9.40 8.71 O3.5V((fc))z 96 1
18 HD 93129 ** 10 43 57.462360 -59 32 51.27000 6.26 7.840 7.884 7.839   O2If*+O3.5V((f)) 197 1
19 HD 93129B * 10 43 57.6453994104 -59 32 53.765064780   10.40 8.84     O3.5V((f)) 67 0
20 HD 120678 Em* 13 52 56.4133904568 -62 43 14.260321632 7.04 9.45 8.20 9.02   O9.5Ve 70 1
21 HD 148937 SB* 16 33 52.3869185520 -48 06 40.476418740 6.49 7.12 6.71 7.61   O6f?p 376 4
22 * zet Oph Be* 16 37 09.5390545 -10 34 01.529471 1.73 2.58 2.56 2.46 2.50 O9.2IVnn 1806 2
23 HD 152248 EB* 16 54 10.0618206816 -41 49 30.139291596 5.56 6.15 6.088     O7Iabf+O7Ib(f) 246 0
24 V* V1297 Sco SB* 16 56 05.2157203176 -40 20 57.576260184 7.87 9.11 9.29 9.29   O7.5Vz 129 0
25 HD 155806 Be* 17 15 19.2478670712 -33 32 54.299379012 4.61 5.52 5.53     O7.5V((f))z(e) 221 0
26 HD 191612 SB* 20 09 28.6105997664 +35 44 01.286453904 7.40 8.07 7.80     O8fpe 232 0
27 BD+40 4220 SB* 20 32 22.4238075360 +41 18 18.942475932 11.32 10.79 9.185     O7Ianfp+Ofpe/WN9 386 0
28 * lam Cep s*b 22 11 30.5765111040 +59 24 52.154264880 4.55 5.29 5.05 4.77 4.62 O6.5I(n)fp 671 1

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2023.02.02-18:05:47

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