Massive non-thermal radio emitters: new data and their modelling

Poster (2011)

Results from the Herschel Key Program MESS

in Kerschbaum, F.; Lebzelter, T.; Wing, R. F. (Eds.) Why Galaxies Care about AGB Stars II: Shining Examples and Common Inhabitants. ASPC 445 (2011)

MESS (Mass loss of Evolved StarS) is a Herschel Guaranteed Time Key Program that will image about 100, and do spectroscopy of about 50, post-main-sequence objects of all flavours: AGB stars, post-AGB ... [more ▼]

MESS (Mass loss of Evolved StarS) is a Herschel Guaranteed Time Key Program that will image about 100, and do spectroscopy of about 50, post-main-sequence objects of all flavours: AGB stars, post-AGB stars, planetary nebulae, luminous blue variables, Wolf-Rayet stars, and supernova remnants. In this review the implementation and current status of MESS is outlined, and first results are presented. [less ▲]

Le centre, les planètes et la noirceur : Controverses cosmiques et terrestres

Article for general public (2011)

Plasma Motion and Kinematics in Cool and Hot Stars

in Space Science Reviews (2010), 157

The environments of both hot and cool stars are the sites of highly dynamic processes involving motion of gas and plasma in winds, flows across shocks, plasma motions in closed magnetic fields, or streams ... [more ▼]

The environments of both hot and cool stars are the sites of highly dynamic processes involving motion of gas and plasma in winds, flows across shocks, plasma motions in closed magnetic fields, or streams along magnetospheric accretion funnels. X-ray spectroscopy has opened new windows toward the study of these processes. Kinematics are evident in line shifts and line broadening, and also more indirectly through the analysis and interpretation of density-sensitive lines. In hot stellar winds, expanding-wind kinematics are directly seen in broadened lines although the broadening has turned out to often be smaller than anticipated, and some lines are so narrow that coronal models have been revived. Although X-ray spectra of cool stars have shown line shifts and broadening due to the kinematics of the entire corona, e.g., in binary systems, intrinsic mass motions are challenging to observe at the presently available resolution. Much indirect evidence for mass motion in magnetic coronae is nevertheless available. And finally, spectral diagnostics has also led to a new picture of X-ray production in accreting pre-main sequence stars where massive accretion flows collide with the photospheric gas, producing shocks in which gas is heated to high temperatures. We summarize evidence for the above mechanisms based on spectroscopic data from XMM-Newton and Chandra. [less ▲]

Une course aux limites des télescopes - étudier en détail une exoplanète

Article for general public (2010)

A Best Practice Guide for Outreach to Schools

(2010, September 01)

Not Available

First Orbital Solution for the Non-thermal Emitter Cyg OB2 No. 9

in Astrophysical Journal (2010), 719

After the first detection of its binary nature, the spectroscopic monitoring of the non-thermal radio emitter Cyg OB2 No. 9 (P = 2.4 yr) has continued, doubling the number of available spectra of the star ... [more ▼]

After the first detection of its binary nature, the spectroscopic monitoring of the non-thermal radio emitter Cyg OB2 No. 9 (P = 2.4 yr) has continued, doubling the number of available spectra of the star. Since the discovery paper of 2008, a second periastron passage has occurred in 2009 February. Using a variety of techniques, the radial velocities could be estimated and a first, preliminary orbital solution was derived from the He I 5876 line. The mass ratio appears close to unity and the eccentricity is large, i.e., 0.7-0.75. X-ray data from 2004 and 2007 are also analyzed in quest of peculiarities linked to binarity. The observations reveal neither large overluminosity nor strong hardness, but it must be noted that the high-energy data were taken after the periastron passage, at a time where colliding wind emission may be low. Some unusual X-ray variability is however detected, with a 10% flux decrease between 2004 and 2007. To clarify their origin and find a more obvious signature of the wind-wind collision, additional data, taken at periastron and close to it, are needed. Based on observations collected at the Haute-Provence Observatory and with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA). [less ▲]

The quest for the most massive star

Article for general public (2010)

Hot and cool: two emission-line stars with constrasting behaviours in the same XMM-Newton field

in Astronomy and Astrophysics (2010), 510

High-energy emissions are good indicators of peculiar behaviours in stars. We have therefore obtained an XMM-Newton observation of HD 155806 and 1RXS J171502.4-333344, and derived their spectral ... [more ▼]

High-energy emissions are good indicators of peculiar behaviours in stars. We have therefore obtained an XMM-Newton observation of HD 155806 and 1RXS J171502.4-333344, and derived their spectral properties for the first time. The X-ray spectrum of HD 155806 appears soft, even slightly softer than usual for O-type stars (as shown by a comparison with the O9 star HD 155889 in the same XMM-Newton field). It is well-fitted with a two-component thermal model with low temperatures (0.2 and 0.6 keV), and it shows no overluminosity (log[L_X/L_BOL] = -6.75). The high-resolution spectrum, though noisy, reveals a few broad, symmetric X-ray lines (FWHMË 2500 km s[SUP]-1[/SUP]). The X-ray emission is compatible with the wind-shock model and therefore appears unaffected by the putative dense equatorial regions at the origin of the Oe classification. 1RXS J171502.4-333344 is a nearby flaring source of moderate X-ray luminosity (log[L_X/L_BOL] = -3), with a soft thermal spectrum composed of narrow lines and presenting a larger abundance of elements (e.g. Ne) with a high first ionization potential (FIP) compared to lower-FIP elements. All the evidence indicates a coronal origin for the X-ray emission, in agreement with the dMe classification of this source. Based on observations collected with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA).Research Associate FNRS. [less ▲]

A close look at the RGS spectra of the O4Ief star Zeta Pup

Poster (2010)