HD 108: The mystery deepens with<i>XMM-Newton</i>observations

Nazé, Yaël; Rauw, Grégor; Vreux, Jean-Marie; Becker, M. De

doi:10.1051/0004-6361:20034422

Cited by 45 publications

(66 citation statements)

References 49 publications

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“…The derived properties are remarkably similar: overluminosities with respect to the "canonical" L X /L BOL = 10 −7 relation, soft spectra, broad X-ray lines (Nazé et al 2004(Nazé et al , 2007(Nazé et al , 2008a. Monitoring HD 191612 further revealed small variations of the X-ray flux.…”

Section: Introductionmentioning

confidence: 71%

“…Since 2004, when optical spectra of HD 108 were last published (Nazé et al 2004), we have continued the monitoring of the star with the Aurélie spectrograph mounted on the 1.52 m telescope of the Haute-Provence Observatory (OHP, France). The detector was a thin back-illuminated CCD composed of 2048 × 1024 pixels of size 13.5 μm 2 .…”

Section: Aurélie Datamentioning

confidence: 99%

“…The spectrum of HD 108 has been followed intensively since 1986 (Nazé et al 2001(Nazé et al , 2004. While some (purely photospheric) lines such as He ii λ 4542 remain constant, the strength of the Balmer, He i (e.g.…”

Section: Hd 108mentioning

confidence: 99%

“…In the past, stars displaying this feature were classified by Walborn (1972) in a separate category, dubbed Of?p. In recent years, this category has attracted a lot of attention, as one can see from the numerous publications (Walborn et al 2003(Walborn et al , 2004Donati et al 2006;Howarth et al 2007;Hubrig et al 2008;Nazé et al 2001Nazé et al , 2004Nazé et al , 2007Nazé et al , 2008a. They dealt with the peculiar properties of these stars (for a summary see Nazé et al 2008b) and led to a modification of the definition of these stars.…”

Section: Introductionmentioning

confidence: 99%

“…The minimum emission state was not yet reached in 2004 (Nazé et al 2004), which prevented a precise evaluation of the recurrence time.…”

Section: Introductionmentioning

confidence: 99%

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New findings on the prototypical Of?p stars

Nazé¹,

ud‐Doula

Spano

et al. 2010

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Aims. In recent years several in-depth investigations of the three prototypical Of?p stars were undertaken. These multiwavelength studies revealed the peculiar properties of these objects (in the X-rays as well as in the optical): magnetic fields, periodic line profile variations, recurrent photometric changes. However, many questions remain unsolved.Methods. To clarify some of the properties of the Of?p stars, we have continued their monitoring. A new xmm-Newton observation and two new optical datasets were obtained. Results. Additional information about the prototypical Of?p trio has been found. HD 108 has now reached its quiescent, minimumemission state for the first time in 50-60 yr. The échelle spectra of HD 148937 confirm the presence of the 7d variations in the Balmer lines and reveal similar periodic variations (though of lower amplitudes) in the He i λ 5876 and He ii λ 4686 lines, underlining its similarities with the other two prototypical Of?p stars. The new xmm-Newton observation of HD 191612 was taken at the same phase in the line modulation cycle, but at a different orbital phase from previous data. It clearly shows that the X-ray emission of HD 191612 is modulated by the 538d period and not by the orbital period of 1542d -it is thus not of colliding-wind origin. The phenomenon responsible for the optical changes appears also at work in the high-energy domain. There are problems however: our MHD simulations of the wind magnetic confinement predict both a harder X-ray flux of a much larger strength than what is observed (the modelled differential emission measure peaks at 30-40 MK, whereas the observed one peaks at 2 MK) and narrow lines (hot gas moving with velocities of 100-200 km s −1 , whereas the observed full width at half maximum is ∼2000 km s −1 ).

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Section: Introductionmentioning

confidence: 71%

Section: Aurélie Datamentioning

confidence: 99%

Section: Hd 108mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…The minimum emission state was not yet reached in 2004 (Nazé et al 2004), which prevented a precise evaluation of the recurrence time.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

New findings on the prototypical Of?p stars

Nazé¹,

ud‐Doula

Spano

et al. 2010

A&A

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111

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First detection of a magnetic field in the fast rotating runaway Oe star ζ Ophiuchi

2011

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The star ζ Ophiuchi is one of the brightest massive stars in the northern hemisphere and was intensively studied in various wavelength domains. The currently available observational material suggests that certain observed phenomena are related to the presence of a magnetic field. We acquired spectropolarimetric observations of ζ Oph with FORS 1 mounted on the 8-m Kueyen telescope of the VLT to investigate if a magnetic field is indeed present in this star. Using all available absorption lines, we detect a mean longitudinal magnetic field Bz all = 141 ± 45 G, confirming the magnetic nature of this star. We review the X-ray properties of ζ Oph with the aim to understand whether the X-ray emission of ζ Oph is dominated by magnetic or by wind instability processes.

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X‐ray emission from massive stars with magnetic fields

et al. 2011

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We investigate the connections between the magnetic fields and the X-ray emission from massive stars. Our study shows that the X-ray properties of known strongly magnetic stars are diverse: while some comply to the predictions of the magnetically confined wind model, others do not. We conclude that strong, hard, and variable X-ray emission may be a sufficient attribute of magnetic massive stars, but it is not a necessary one. We address the general properties of X-ray emission from "normal" massive stars, especially the long standing mystery about the correlations between the parameters of X-ray emission and fundamental stellar properties. The recent development in stellar structure modeling shows that small scale surface magnetic fields may be common. We suggest a "hybrid" scenario which could explain the X-ray emission from massive stars by a combination of magnetic mechanisms on the surface and shocks in the stellar wind. The magnetic mechanisms and the wind shocks are triggered by convective motions in sub-photospheric layers. This scenario opens the door for a natural explanation of the well established correlation between bolometric and X-ray luminosities.

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HD 108: The mystery deepens withXMM-Newtonobservations

Cited by 45 publications

References 49 publications

New findings on the prototypical Of?p stars

New findings on the prototypical Of?p stars

First detection of a magnetic field in the fast rotating runaway Oe star ζ Ophiuchi

X‐ray emission from massive stars with magnetic fields

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