Showing papers by "Pierre Royer published in 2005"

The massive binary CPD - 41°7742. II. Optical light curve and X-ray observations

Abstract: In the first paper of this series, we presented a detailed high-resolution spectroscopic study of CPD-41° 7742, deriving for the first time an orbital solution for both components of the system. In this second paper, we focus on the analysis of the optical light curve and on recent XMM-Newton X-ray observations. In the optical, the system presents two eclipses, yielding an inclination i 77°. Combining the constraints from the photometry with the results of our previous work, we derive the absolute parameters of the system. We confirm that the two components of CPD - 41° 7742 are main sequence stars (09 V+ B1-1.5 V) with masses (M 1 ∼ 18 M ○. and M 2 ∼ 10 M ○. ) and respective radii (R 1 ∼ 7.5 R ○. and R 2 ∼ 5.4 R ○. ) close to the typical values expected for such stars. We also report an unprecedented set of X-ray observations that almost uniformly cover the 2.44-day orbital cycle. The X-ray emission from CPD-41° 7742 is well described by a two-temperature thermal plasma model with energies close to 0.6 and 1.0keV, thus slightly harder than typical early-type emission. The X-ray light curve shows clear signs of variability. The emission level is higher when the primary is in front of the secondary. During the high emission state, the system shows a drop of its X-ray emission that almost exactly matches the optical eclipse. We interpret the main features of the X-ray light curve as the signature of a wind-photosphere interaction, in which the overwhelming primary O9 star wind crashes into the secondary surface. Alternatively the light curve could result from a wind-wind interaction zone located near the secondary star surface. As a support to our interpretation, we provide a phenomenological geometric model that qualitatively reproduces the observed modulations of the X-ray emission.

The massive binary CPD-41degr7742 II. Optical light curve and X-ray observations

Abstract: In the first paper of this series, we presented a detailed high-resolution spectroscopic study of CPD - 41degr7742, deriving for the first time an orbital solution for both components of the system. In this second paper, we focus on the analysis of the optical light curve and on recent XMM-Newton X-ray observations. In the optical, the system presents two eclipses, yielding an inclination i ~ 77degr. Combining the constraints from the photometry with the results of our previous work, we derive the absolute parameters of the system. We confirm that the two components of CPD - 41degr7742 are main sequence stars (O9 V + B1-1.5 V) with masses (M_1 ~ 18 Msol and M_2 ~ 10 Msol) and respective radii (R_1 ~ 7.5 Rsol and R_2 ~ 5.4 Rsol) close to the typical values expected for such stars. We also report an unprecedented set of X-ray observations that almost uniformly cover the 2.44-day orbital cycle. The X-ray emission from CPD - 41degr7742 is well described by a two-temperature thermal plasma model with energies close to 0.6 and 1.0 keV, thus slightly harder than typical early-type emission. The X-ray light curve shows clear signs of variability. The emission level is higher when the primary is in front of the secondary. During the high emission state, the system shows a drop of its X-ray emission that almost exactly matches the optical eclipse. We interpret the main features of the X-ray light curve as the signature of a wind-photosphere interaction, in which the overwhelming primary O9 star wind crashes into the secondary surface. Alternatively the light curve could result from a wind-wind interaction zone located near the secondary star surface. As a support to our interpretation, we provide a phenomenological geometric model that qualitatively reproduces the observed modulations of the X-ray emission.

The Photodetector Array Camera & Spectrometer (PACS) for the Herschel space observatory

Abstract: The Photodetector Array Camera and Spectrometer (PACS) is one of the three science instruments for ESA's far infrared and submillimetre observatory, Herschel. It employs two Ge:Ga photoconductor arrays (stressed and unstressed) with 16 x 25 pixels, each, and two filled Si bolometer arrays with 16 x 32 and 32 x 64 pixels, respectively, to perform imaging line spectroscopy and imaging photometry in the 60-210 μm wavelength band. In photometry mode, it will simultaneously image two bands, 60-85 or 85-130 μm and 130-210 μm, over a field of view of ~1.75' x 3.5', with full beam sampling in each band. In spectroscopy mode, it will image a field of ~ 50", resolved into 5 x 5 pixels, with an instantaneous spectral coverage of ~1500 km/s and a spectral resolution of ~ 175km/s. In both modes background-noise limited performance is expected, with sensitivities (5σ in 1h) of ~ 3 mJy or 3-10x10-18W/m2, respectively.