Des explosions gigantesques dans le ciel gamma

Article for general public (2004)

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WR bubbles and HeII emission

in Astronomy and Astrophysics (2003), 408(1), 171-186

We present the very first high quality images of the He II lambda4686 emission in three high excitation nebulae of the Magellanic Clouds. A fourth high excitation nebula, situated around the WR star BAT99 ... [more ▼]

We present the very first high quality images of the He II lambda4686 emission in three high excitation nebulae of the Magellanic Clouds. A fourth high excitation nebula, situated around the WR star BAT99-2, was analysed in a previous letter. Using VLT FORS data, we investigate the morphology of the ring nebulae around the early-type WN stars BAT99-49 [less ▲]

Des étoiles vraiment très chaudes

Article for general public (2003)

VLT observations of the highly ionized nebula around Brey2

in Astronomy and Astrophysics (2003), 401(2), 13-16

We present the first high resolution He II lambda4686 images of the high excitation nebula around the WR star Brey2 in the LMC. This nebula presents a striking morphology: a small arc-like feature some 3 ... [more ▼]

We present the first high resolution He II lambda4686 images of the high excitation nebula around the WR star Brey2 in the LMC. This nebula presents a striking morphology: a small arc-like feature some 3.6 pc in radius is particularly prominent in the He II lambda4686 line. We further discover a previously unknown faint He II emission that extends over an area of 22 x 17 pc(2). An even fainter He II emission is apparently associated with the interstellar bubble blown by the progenitor of Brey2. The total He II flux corresponds to an ionizing flux of 4 x 10(47) photons s(-1). Halpha, [O III], and He I lambda5876 images and long-slit spectra are also examined in this letter, enabling us to investigate the detailed physical properties at various locations of the nebula. [less ▲]

Preliminary results from XMM-Newton observations of the massive Wolf-Rayet binary WR 22 (WN7h+O9III-V)

in A Massive Star Odyssey: From Main Sequence to Supernova (2003)

We present preliminary results from observations of the massive WR+O binary WR 22 performed with the XMM observatory. The star is brighter in the X-ray domain near apastron and fainter at periastron. The ... [more ▼]

We present preliminary results from observations of the massive WR+O binary WR 22 performed with the XMM observatory. The star is brighter in the X-ray domain near apastron and fainter at periastron. The change in brightness is very progressive and mainly corresponds to a lowering of the soft part of the spectrum. [less ▲]

Structure and dynamics of candidate O star bubbles in N44

in Astronomical Journal (The) (2002), 124(6), 3325-3335

Dynamical studies of superbubbles and Wolf-Rayet ring nebulae show discrepancies from the standard adiabatic model for windblown bubbles. We therefore study the physical properties and kinematics of three ... [more ▼]

Dynamical studies of superbubbles and Wolf-Rayet ring nebulae show discrepancies from the standard adiabatic model for windblown bubbles. We therefore study the physical properties and kinematics of three candidate bubbles blown by single O stars to evaluate whether these discrepancies are also found in these simpler objects. Our sample candidates are N44 F, N44 J, and N44 M, in the outskirts of the H II complex N44 in the Large Magellanic Cloud. We have obtained ground-based and Hubble Space Telescope emission-line images and high-dispersion echelle spectra for these objects. From the Halpha luminosities and the [ O III]/ Halpha ratios of these nebulae, we estimate the spectral types of the ionizing stars to be O7 V, O9.5 V, and O9.5 V for N44 F, N44 J, and N44 M, respectively. We. find that the observed expansion velocity of 12 km s(-1) for N44 F is consistent with the stellar wind luminosity expected from the central ionizing star, as predicted by the standard bubble model. The observed upper limits for the expansion velocities of N44 J and N44 M are also compatible with the expected values, within the uncertainties. We also report the discovery in N44 F of strongly defined dust columns, similar to those seen in the Eagle Nebula. The photoevaporation of these dense dust features may be kinematically important and may actually govern the evolution of the shell. The inclusion of photoevaporation processes may thus undermine the apparent agreement between the observed bubble dynamics and the simple adiabatic models. [less ▲]

An XMM-Newton observation of the Lagoon Nebula and the very young open cluster NGC 6530

in Astronomy and Astrophysics (2002), 395(2), 499-513

We report the results of an XMM-Newton observation of the Lagoon Nebula (M8). Our EPIC images of this region reveal a cluster of point sources, most of which have optical counterparts inside the very ... [more ▼]

We report the results of an XMM-Newton observation of the Lagoon Nebula (M8). Our EPIC images of this region reveal a cluster of point sources, most of which have optical counterparts inside the very young open cluster NGC6530. The bulk of these X-ray sources are probably associated with low and intermediate mass pre-main sequence stars. One of the sources experienced a flare-like increase of its X-ray flux making it the second brightest source in M8 after the O4 star 9 Sgr. The X-ray spectra of most of the brightest sources can be fitted with thermal plasma models with temperatures of kT similar to a few keV. Only a few of the X-ray selected PMS candidates are known to display Halpha emission and were previously classified as classical T Tauri stars. This suggests that most of the X-ray emitting PMS stars in NGC6530 are weak-line T Tauri stars. In addition to 9 Sgr, our EPIC field of view contains also a few early-type stars. The X-ray emission from HD 164816 is found to be typical for an O9.5 III-IV star. At least one of the known Herbig Be stars in NGC6530 ( LkHalpha 115) exhibits a relatively strong X-ray emission, while most of the main sequence stars of spectral type B1 and later are not detected. We also detect ( probably) diffuse X-ray emission from the Hourglass Region that might reveal a hot bubble blown by the stellar wind of Herschel 36, the ionizing star of the Hourglass Region. [less ▲]

Laisse tomber le C8 ... je pars au Chili! (2)

Article for general public (2002)

Laisse tomber le C8 ... je pars au Chili! (1)

Article for general public (2002)

Chandra/ACIS observation of NGC 346

in Bulletin of the American Astronomical Society (2001, December 01)

The cluster NGC346 is the largest star formation region in the SMC. It contains a large fraction of the early-type O stars of this galaxy. In the outskirts of this cluster lies HD 5980, a unique system of ... [more ▼]

The cluster NGC346 is the largest star formation region in the SMC. It contains a large fraction of the early-type O stars of this galaxy. In the outskirts of this cluster lies HD 5980, a unique system of massive stars of which one component underwent a LBV-type eruption in 1993. The XMEGA consortium has obtained one deep (100 ks) Chandra exposure of NGC 346. It shows ~70 point sources, of which only half possess an optical counterpart; strong emission from HD 5980; and diffuse emission associated with the cluster and SNR 0057-7226. [less ▲]