2008A&A...485..209A


Query : 2008A&A...485..209A

2008A&A...485..209A - Astronomy and Astrophysics, volume 485, 209-221 (2008/7-1)

MWC 297: a young high-mass star rotating at critical velocity.

ACKE B., VERHOELST T., VAN DEN ANCKER M.E., DEROO P., WAELKENS C., CHESNEAU O., TATULLI E., BENISTY M., PUGA E., WATERS L.B.F.M., VERHOEFF A. and DE KOTER A.

Abstract (from CDS):

object{MWC 297} is a nearby young massive B[e] star. The central star is attenuated by 8 mag in the optical and has a high projected rotational velocity of 350km/s. Despite the wealth of published observations, the nature of this object and its circumstellar environment is not understood very well. With the present paper, we intend to shed light on the geometrical structure of the circumstellar matter that is responsible for the near- to mid-infrared flux excess. The H-band (1.6-2.0µm), K-band (2.0-2.5µm), and N-band (8-13µm) brightness distribution of MWC 297 was probed with the ESO interferometric spectrographs AMBER and MIDI, mounted on the VLTI in Paranal, Chile. We obtained visibility measurements on 3 AMBER and 12 MIDI baselines, covering a wide range of spatial frequencies. Different models (parametrized circumstellar disks, a dusty halo) were invoked to fit the data, all of which fail to do so in a satisfying way. We approximated the brightness distribution in H, K, and N with a geometric model consisting of three Gaussian disks with different extents and brightness temperatures. This model can account for the entire near- to mid-IR emission of MWC 297. The circumstellar matter around MWC 297 is resolved on all baselines. The near- and mid-IR emission, including the silicate emission at 10 micron, emanates from a very compact region (FWHM<1.5AU) around the central star. We argue that the extinction towards the MWC 297 star+disk system is interstellar and most likely due to remnants of the natal cloud from which MWC 297 was formed. Furthermore, we argue that the circumstellar matter in the MWC 297 system is organized in a circumstellar disk, seen under moderate (i<40°) inclination. The disk displays no inner emission-free gap at the resolution of our interferometric observations. The low inclination of the disk implies that the already high projected rotational velocity of the star corresponds to an actual rotational velocity that exceeds the critical velocity of the star. This result shows that stars can obtain such high rotation rates at birth. We discuss the impact of this result in terms of the formation of high-mass stars and the main-sequence evolution of classical Be stars.

Abstract Copyright:

Journal keyword(s): techniques: interferometric - circumstellar matter - stars: pre-main-sequence - stars: individual: MWC 297 - stars: emission-line, Be - stars: rotation

CDS comments: Paragraph.5. MCW 297 is a probable misprint for EM* MWC 297.

Simbad objects: 13

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Number of rows : 13
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 V* Z CMa Ae* 07 03 43.1599411656 -11 33 06.209065836 10.51 9.99 8.80     B5/8eq+F5/7 579 3
2 * N Vel V* 09 31 13.3181527686 -57 02 03.755222030   4.691 3.139     K5III 98 0
3 * del Oph PM* 16 14 20.7390218758 -03 41 39.572826363 6.30 4.34 2.75 1.46 0.43 M0.5III 363 0
4 * alf Sco s*r 16 29 24.45970 -26 25 55.2094 4.08 2.75 0.91 -0.64 -1.87 M1.5Iab+B2Vn 746 0
5 CD-42 11721 Be* 16 59 06.7629322176 -42 42 08.404228224 12.16 12.28 11.00     B0IVe 168 0
6 HD 166460 * 18 10 40.2991027656 +03 19 27.328290276   6.693 5.489     K1II 68 0
7 * eta Sgr LP? 18 17 37.6371989461 -36 45 42.084592381 6.37 4.67 3.11 1.55 0.23 M2III 144 0
8 * del Sgr * 18 20 59.6428936493 -29 49 41.168145329   4.069 2.668     K2.5IIIaCN0.5 175 0
9 EM* MWC 297 Ae* 18 27 39.5265500160 -03 49 52.133050776 15.57 14.34 12.31 11.34   B1.5Ve 297 0
10 NAME MWC 297 Stellar Group Cl* 18 27 40 -03 49.9           ~ 14 0
11 * alf Aql dS* 19 50 46.99855 +08 52 05.9563 1.07 0.98 0.76 0.62 0.49 A7Vn 878 1
12 V* PV Cep Or* 20 45 53.9540390184 +67 57 38.679941304   19.27 17.46 15.98 14.60 A5 270 1
13 V* V645 Cyg Ae* 21 39 58.2745507632 +50 14 21.042184668   14.23 13.10 13.82   O6/9eq 274 0

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