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The very massive X-ray bright binary system Wack 2134 (= WR 21a)

The very massive X-ray bright binary system Wack 2134 (= WR 21a)
The very massive X-ray bright binary system Wack 2134 (= WR 21a)
From the radial velocities of the N ivλ4058 and He iiλ4686 emission lines, and the N vλ4604-20 absorption lines, determined in digital spectra, we report the discovery that the X-ray bright emission line star Wack 2134 (= WR 21a) is a spectroscopic binary system with an orbital period of 31.673 ± 0.002 d . With this period, the N iv and He ii emission and N v absorption lines, which originate in the atmosphere of the primary component, define a rather eccentric binary orbit (e =  0.64 ± 0.03) . The radial velocity variations of the N v absorptions have a lower amplitude than those of the He ii emission. Such a behaviour of the emission line radial velocities could be due to distortions produced by a superimposed absorption component from the companion. High-resolution echelle spectra observed during the quadrature phases of the binary show H and He ii absorptions of both components with a radial velocity difference of about 541 km s-1. From this difference, we infer quite high values of the minimum masses, of about 87 and 53 M☉ for the primary and secondary components, respectively, if the radial velocity variations of the He ii emission represent the true orbit of the primary. No He i absorption lines are observed in our spectra. Thus, the secondary component in the Wack 2134 binary system appears to be an early O-type star. From the presence of H, He ii and N v absorptions, and N iv and C iv emissions, in the spectrum of the primary component, it most clearly resembles those of Of/WNLha-type stars.
binaries: spectroscopic, stars: wolf-rayet, stars: individual: wack 2134, stars: individual: wr 21a
0035-8711
1447-1452
Niemela, V.S.
f127fc3e-5696-400f-add0-ca77a5bf39d7
Gamen, R.C.
fa82bf15-fabe-4c3b-b78b-274cdfc35166
Barbá, R.H.
7ab44347-5ac3-4ab2-a9b4-c2ae2b66c888
Fernández Lajús, E.
d9eff6ca-d96d-488e-bafa-bc6b5c65a58a
Benaglia, P.
ac307e7f-5537-446e-8742-4b39dd435542
Solivella, G.R.
c8793eef-0b03-40a2-9bf2-353fa4c40adc
Reig, P.
66ae1b8d-9c4b-449d-a459-6e8382a5986b
Coe, Malcolm J.
04dfb23b-1456-46a3-9242-5cee983471d5
Niemela, V.S.
f127fc3e-5696-400f-add0-ca77a5bf39d7
Gamen, R.C.
fa82bf15-fabe-4c3b-b78b-274cdfc35166
Barbá, R.H.
7ab44347-5ac3-4ab2-a9b4-c2ae2b66c888
Fernández Lajús, E.
d9eff6ca-d96d-488e-bafa-bc6b5c65a58a
Benaglia, P.
ac307e7f-5537-446e-8742-4b39dd435542
Solivella, G.R.
c8793eef-0b03-40a2-9bf2-353fa4c40adc
Reig, P.
66ae1b8d-9c4b-449d-a459-6e8382a5986b
Coe, Malcolm J.
04dfb23b-1456-46a3-9242-5cee983471d5

Niemela, V.S., Gamen, R.C., Barbá, R.H., Fernández Lajús, E., Benaglia, P., Solivella, G.R., Reig, P. and Coe, Malcolm J. (2008) The very massive X-ray bright binary system Wack 2134 (= WR 21a). Monthly Notices of the Royal Astronomical Society, 389 (3), 1447-1452. (doi:10.1111/j.1365-2966.2008.13684.x).

Record type: Article

Abstract

From the radial velocities of the N ivλ4058 and He iiλ4686 emission lines, and the N vλ4604-20 absorption lines, determined in digital spectra, we report the discovery that the X-ray bright emission line star Wack 2134 (= WR 21a) is a spectroscopic binary system with an orbital period of 31.673 ± 0.002 d . With this period, the N iv and He ii emission and N v absorption lines, which originate in the atmosphere of the primary component, define a rather eccentric binary orbit (e =  0.64 ± 0.03) . The radial velocity variations of the N v absorptions have a lower amplitude than those of the He ii emission. Such a behaviour of the emission line radial velocities could be due to distortions produced by a superimposed absorption component from the companion. High-resolution echelle spectra observed during the quadrature phases of the binary show H and He ii absorptions of both components with a radial velocity difference of about 541 km s-1. From this difference, we infer quite high values of the minimum masses, of about 87 and 53 M☉ for the primary and secondary components, respectively, if the radial velocity variations of the He ii emission represent the true orbit of the primary. No He i absorption lines are observed in our spectra. Thus, the secondary component in the Wack 2134 binary system appears to be an early O-type star. From the presence of H, He ii and N v absorptions, and N iv and C iv emissions, in the spectrum of the primary component, it most clearly resembles those of Of/WNLha-type stars.

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More information

Published date: 21 August 2008
Keywords: binaries: spectroscopic, stars: wolf-rayet, stars: individual: wack 2134, stars: individual: wr 21a
Organisations: University of Southampton

Identifiers

Local EPrints ID: 143569
URI: http://eprints.soton.ac.uk/id/eprint/143569
ISSN: 0035-8711
PURE UUID: bd5c4f59-8c60-4e8c-8317-6fc9f00463bf
ORCID for Malcolm J. Coe: ORCID iD orcid.org/0000-0002-0763-8547

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Date deposited: 12 Apr 2010 13:51
Last modified: 18 Feb 2021 16:34

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Contributors

Author: V.S. Niemela
Author: R.C. Gamen
Author: R.H. Barbá
Author: E. Fernández Lajús
Author: P. Benaglia
Author: G.R. Solivella
Author: P. Reig
Author: Malcolm J. Coe ORCID iD

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