Query : 2002A&A...385..600V

2002A&A...385..600V - Astronomy and Astrophysics, volume 385, 600-618 (2002/4-2)

The enigmatic WR46: A binary or a pulsator in disguise. II. The spectroscopy.


Abstract (from CDS):

We present spectroscopic monitoring of the Wolf-Rayet (WR) star WR46 between 1989 and 1998, which has been obtained simultaneously with multicolour photometry (Veen et al., 2002A&A...385..585V, Paper I). The spectroscopic monitoring data show that the radiative fluxes of the optical emission lines (OVI 3811/34, OVI 5290, NV 4944, NV 4604/20, HeII 4686, HeII 4859, HeII 5411, HeII 6560) vary in concert with the photometric single-wave (sw) frequency fsw (Paper I), and also the difference of that period between 1989 and 1991. The line-flux variability does not provide obvious support for a short second period (Paper I). The radial-velocity variations show a remarkable behaviour: usually, they display a coherent single-wave on the time scale of the double-wave period, while during some nights the radial velocity appears surprisingly to stay constant (see also Marchenko et al., 2000AJ....120.2101M). These so-called stand-stills may be related to the observed time-delay effects. A time-delay effect manifests itself in several phenomena. Firstly, the line flux shows small, but persistent, time-delays for lines originating from lower optical depths, the outer-wind lines (NV 4604/20 and HeII). Secondly, the radial-velocity variations display much larger time-delays than the line fluxes and their behaviour appears less consistent. Assuming that the double-wave period controls the radial velocity, the stand-still is observed to start when the radial motion is in anti-phase with the presumed orbital motion. Thirdly, the outer-wind lines are observed to enter a stand-still much later than the inner-wind lines. Fourthly, the radial-velocity variations of the peaks of the emission lines precede the radial-velocity variations of the wings of those lines. In addition to line-flux- and radial-velocity variability, the HeII 4686 emission line shows pronounced line-profile changes on a time scale of hours. Our monitoring is not sufficient to study this in detail. Furthermore, we discern a flaring behaviour, i.e., an emission bump appeared on the blue wing of two HeII-lines (around -1700 km.s–1) lasting less than 5 min. Finally, the line fluxes follow the observed brightenings, also on a time scale of years. We conclude that the short-term cyclic variability confirms the WR nature as established from the WR standard model analysis by Crowther et al. (1995A&A...302..457C; hereafter referred to as CSH). The various time-delay effects are consistent with the formation of the spectrum in a stratified stellar wind. The outer layers trail the inner ones. The variability is inconsistent with the formation of the spectrum in a stellar disc as proposed by Niemela et al. (1995IAUS..163..245N) and Steiner & Diaz (1998PASP..110..276S). The long-term cyclic variability of the brightness and line fluxes is related to an increase of the mass-loss-rate, and, possibly, to the period changes. The interpretation of the nature of the variability is deferred to Veen et al. (2002A&A...385..619V, Paper III).

Abstract Copyright:

Journal keyword(s): stars: Wolf-Rayet - stars: individual: WR 46 - stars: binaries: close - stars: variables: general - stars: oscillations

Simbad objects: 7

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Number of rows : 7
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
1 HD 9974 WR* 01 38 55.6274097096 +58 09 22.673806272 9.85 10.71 10.69     WN3h-w 169 0
2 HD 50896 WR* 06 54 13.0439608392 -23 55 42.023319852 5.74 6.63 6.91 7.74   WN4b 764 0
3 HD 104994 WR* 12 05 18.7204232424 -62 03 10.140656832 9.95 10.94 10.93 11.03   WN3p-w 163 0
4 HD 187282 WR* 19 48 32.1967360032 +18 12 03.695582124 9.60 10.49 10.51     WN4(h)-w 195 0
5 HD 191765 WR* 20 10 14.1928045152 +36 10 35.070683376 7.64 8.08 8.08     WN6-s 438 0
6 MR 114 WR* 22 09 33.4430950032 +57 44 30.527883600 12.78 12.946 12.078 11.853   WN4+O5V 138 0
7 HD 211564 WR* 22 16 24.0318845736 +55 37 36.767570232   11.72 11.61     WN3(h)-w 119 0

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